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Design, development, and implementation of recirculating aquaria for maintenance and experimentation of deep-sea corals and associated fauna: Recirculating aquaria for deep-sea corals
Limnology and Oceanography: Methods
Abstract
Here, the development and construction of recirculating aquaria for the long-term maintenance and study of deep-water corals in the laboratory is described. This system may be applied to the maintenance and exper-imentation on marine organisms in the absence of a natural seawater supply. Since 2009, numerous colonies of Lophelia pertusa as well as several species of associated invertebrates from the Gulf of Mexico have been main-tained in the described systems. The behavior of some of these species, including L. pertusa, the corallivorous snail Coralliophila sp., the polychaete Eunice sp., and the galetheoid crab Eumunida picta in the laboratory is described. Additionally, these systems were used for the manipulation of pH and dissolved oxygen for short-term experiments using L. pertusa. The detailed manipulation of carbonate chemistry in artificial seawater is described for use in ocean acidification experiments.
... L. pertusa were collected in the Gulf of Mexico in April and May 2014 on the R/V Atlantis using the DSV Alvin (Woods Hole Oceanographic Institution). All corals were collected at similar depths, temperature and carbonate chemistry conditions (Table 1) from the Viosca Knoll 826 (VK826) site (Cordes et al., 2008), named for the oil lease block governed by the At the time of arrival, all corals were kept in a 550 L recirculating aquarium system with artificial seawater (ASW) prepared using Instant Ocean R (aquarium sea-salt mixture) and maintained at a temperature of ∼8 • C, salinity 35 ppt, and total alkalinity (TA) ∼2,300 µmol kg −1 (for full description of the system see Lunden et al., 2014b). The corals were fed 20 mL of artificial MarineSnow R (Two Little Fishies) 3 days a week, as per comparable experimental procedures (Lunden et al., 2014a,b;Hennige et al., 2015;Georgian et al., 2016b). ...
... Because Instant Ocean R at salinity 35 yields seawater with a total alkalinity of ∼3,600 µmol kg −1 , 12.1 N HCl was added to previously prepared artificial seawater (ASW) in order to reduce the total alkalinity to ∼2,300 µmol kg −1 before adjusting the pH (Lunden et al., 2014b). The manipulation of the pH was accomplished by bubbling pure CO 2 gas into the different treatment tanks using an automated CO 2 injection system (American Marine Inc, PINPOINT pH Monitor). ...
... In July 2014, the six collections were randomly split between two identical 550 L recirculating units (fully described in Lunden et al., 2014b). Two pH T treatments were selected: 7.90 as the control, and 7.60 as the treatment. ...
Ocean acidification, the decrease in seawater pH due to the absorption of atmospheric CO2, profoundly threatens the survival of a large number of marine species. Cold-water corals are considered to be among the most vulnerable organisms to ocean acidification because they are already exposed to relatively low pH and corresponding low calcium carbonate saturation states (Ω). Lophelia pertusa is a globally distributed cold-water scleractinian coral that provides critical three-dimensional habitat for many ecologically and economically significant species. In this study, four different genotypes of L. pertusa were exposed to three pH treatments (pH = 7.60, 7.75, and 7.90) over a short (2-week) experimental period, and six genotypes were exposed to two pH treatments (pH = 7.60 and 7.90) over a long (6-month) experimental period. Their physiological response was measured as net calcification rate and the activity of carbonic anhydrase, a key enzyme in the calcification pathway. In the short-term experiment, net calcification rates did not significantly change with pH, although they were highly variable in the low pH treatment, including some genotypes that maintained positive net calcification in undersaturated conditions. In the 6-month experiment, average net calcification was significantly reduced at low pH, with corals exhibiting net dissolution of skeleton. However, one of the same genotypes that maintained positive net calcification (+0.04% day⁻¹) under the low pH treatment in the short-term experiment also maintained positive net calcification longer than the other genotypes in the long-term experiment, although none of the corals maintained positive calcification for the entire 6 months. Average carbonic anhydrase activity was not affected by pH, although some genotypes exhibited small, insignificant, increases in activity after the sixth month. Our results suggest that while net calcification in L. pertusa is adversely affected by ocean acidification in the long term, it is possible that some genotypes may prove to be more resilient than others, particularly to short perturbations of the carbonate system. These results provide evidence that populations of L. pertusa in the Gulf of Mexico may contain the genetic variability necessary to support an adaptive response to future ocean acidification.
... Two). The physical environment of the two sites is similar: temperatures at VK906 range from 8 to 12.5 @BULLET C and from 6.5 to 11.6 @BULLET C at VK826, while salinity at both sites ranges from 34.9 to 35.4 (Mienis et al., 2012; Georgian et al., 2014; Lunden et al., 2014). Observations of dissolved oxygen concentrations from the two sites range from 1.5 to 3.4 ml·l −1 , with mean dissolved oxygen near 3 ml·l −1 (Davies et al., 2010; Georgian et al., 2014). ...
... Upon return to port, corals were immediately transported overnight to the laboratory on wet ice. In the laboratory, corals were maintained in one of two 570 liter recirculating aquaria systems at temperature 8 @BULLET C and salinity 35 ppt (Lunden et al., 2014). Regular partial water changes (15–20%) were performed with seawater made using Instant Ocean® sea salt. ...
... Each experiment consisted of 3–5 treatments (Table 1 ). All experiments were conducted in a constanttemperature room in the laboratory (see Lunden et al., 2014, for complete description of experimental aquaria). Three 75-l aquaria ( " tall " type: 61 × 33 × 43 cm) with individual Hagen® AquaClear® 30 filtration units (Drs. ...
Changing global climate due to anthropogenic emissions of CO2 are driving rapid changes in the physical and chemical environment of the oceans via warming, deoxygenation, and acidification. These changes may threaten the persistence of species and populations across a range of latitudes and depths, including species that support diverse biological communities that in turn provide ecological stability and support commercial interests. Worldwide, but particularly in the North Atlantic and deep Gulf of Mexico, Lophelia pertusa forms expansive reefs that support biological communities whose diversity rivals that of tropical coral reefs. In this study, L. pertusa colonies were collected from the Viosca Knoll region in the Gulf of Mexico (390 to 450 m depth), genotyped using microsatellite markers, and exposed to a series of treatments testing survivorship responses to acidification, warming, and deoxygenation. All coral nubbins survived the acidification scenarios tested, between pH of 7.67 and 7.90 and aragonite saturation states of 0.92 and 1.47. However, net calcification generally declined with respect to pH, though a disparate response was evident where select individuals net calcified and others exhibited net dissolution near a saturation state of 1. Warming and deoxygenation both had negative effects on survivorship, with up to 100% mortality observed at temperatures above 14°C and oxygen concentrations of approximately 1.5 ml· l⁻¹. These results suggest that, over the short-term, climate change and OA may negatively impact L. pertusa in the Gulf of Mexico, though the potential for acclimation and the effects of genetic background should be considered in future research.
... Apesar de já existirem vários estudos piloto a demonstrar a viabilidade de transplantar espécies de corais profundas, algumas das quais a apresentarem elevadas taxas de sobrevivência (e.g., Brooke et al., 2006;Brooke e Young, 2009;Dahl, 2013;Montseny et al., 2019;2020 Para além destes desafios logísticos, muitos organismos do mar profundo estão adaptados a condições ambientais extremas, o que dificulta a sua manutenção em cativeiro, uma vez que variações grandes de pressão e temperatura durante a amostragem comprometem a sua capacidade de manter funções biológicas cruciais à sobrevivência (Somero, 1992;Bartlett et al., 1995;Pradillon et al., 2004). Para corais em particular, a temperatura parece ser o parâmetro ambiental mais importante de controlar visto que a grande maioria das espécies ocorrem a faixas batimétricas acima dos 1000 m onde a adaptação a pressões hidrostáticas elevadas é menos pronunciada (Pradillon et al., 2004;Lunden et al., 2014). A este respeito, os desenvolvimentos tecnológicos das últimas duas décadas têm contribuído para um melhoramento substancial das condições de manipulação e manutenção de corais em tanques (Lunden et al., 2014;Orejas et al., 2019). ...
... Para corais em particular, a temperatura parece ser o parâmetro ambiental mais importante de controlar visto que a grande maioria das espécies ocorrem a faixas batimétricas acima dos 1000 m onde a adaptação a pressões hidrostáticas elevadas é menos pronunciada (Pradillon et al., 2004;Lunden et al., 2014). A este respeito, os desenvolvimentos tecnológicos das últimas duas décadas têm contribuído para um melhoramento substancial das condições de manipulação e manutenção de corais em tanques (Lunden et al., 2014;Orejas et al., 2019). ...
This technical report provides an overview about coral ecosystems in deep continental waters of Portugal. We start by giving a historic account of research conducted to date for these marine habitats in Portugal to then discuss the key ecosystem services and goods they provide, major human impacts, conservation and restoration efforts, as well as challenges that lie ahead. The document is an output of project HABMAR also describing some of the research conducted during the project.
... Contrastingly, L. pertusa from Norway exhibited decreased calcification rates in another short-term (1 week) experiment but slightly elevated rates after a six month exposure to low pH (Form & Riebesell, 2012), potentially indicating acclimation to low pH. Gulf of Mexico Kurman, Gómez, Georgian, Lunden, & Cordes, 2017;Lunden, Turner, McNicholl, Glynn, & Cordes, 2014) and California (Gómez, 2018) populations of L. pertusa exhibited decreased calcification rates in short-term experiments (2-5 weeks). However, in both short-and long-term experiments certain colonies were able to grow more quickly and maintain positive calcification longer than others (Kurman et al., 2017;. ...
... At Temple, corals were kept in a 550 L recirculating aquarium (Lunden, Turner, et al., 2014). Briefly, artificial seawater (ASW) was prepared using Instant Ocean and tanks were maintained at ca. 8°C, salinity 35 ppt, and total alkalinity ca. ...
Cold‐water corals (CWCs) are important foundation species in the world’s largest ecosystem, the deep sea. They support a rich faunal diversity but are threatened by climate change and increased ocean acidification. As part of this study, fragments from three genetically distinct Lophelia pertusa colonies were subjected to ambient pH (pH = 7.9) and low pH (pH = 7.6) for 6 months. RNA was sampled at 2, 4.5, and 8.5 weeks and sequenced. The colony from which the fragments were sampled explained most of the variance in expression patterns, but a general pattern emerged where up‐regulation of ion transport, required to maintain normal function and calcification, was coincident with lowered expression of genes involved in metabolic processes; RNA regulation and processing in particular. Furthermore, there was no differential expression of carbonic anhydrase detected in any analyses, which agrees with a previously described lack of response in enzyme activity in the same corals. However, one colony was able to maintain calcification longer than the other colonies when exposed to low pH and showed increased expression of ion transport genes including proton transport and expression of genes associated with formation of microtubules and the organic matrix, suggesting that certain genotypes may be better equipped to cope with ocean acidification in the future. While these genotypes exist in the contemporary gene pool, further stresses would reduce the genetic variability of the species, which would have repercussions for the maintenance of existing populations and the ecosystem as a whole.
... Once at Temple University, all corals were kept in 550-liter recirculating aquarium systems with artificial seawater (ASW) prepared using Instant Ocean ® or B-Ionic (EVS) and maintained at a temperature of ~8 °C, salinity of 35 ppt, and a pH of ~7.9 69 . Corals were fed MarineSnow (Two Little Fishes) at least 3 days a week 45,53,69 . ...
... Once at Temple University, all corals were kept in 550-liter recirculating aquarium systems with artificial seawater (ASW) prepared using Instant Ocean ® or B-Ionic (EVS) and maintained at a temperature of ~8 °C, salinity of 35 ppt, and a pH of ~7.9 69 . Corals were fed MarineSnow (Two Little Fishes) at least 3 days a week 45,53,69 . Prior to experimentation the corals were fragmented into nubbins (3-6 polyps) and allowed to acclimate to aquaria conditions for at least two months. ...
There are numerous studies highlighting the impacts of direct and indirect stressors on marine organisms, and multi-stressor studies of their combined effects are an increasing focus of experimental work. Lophelia pertusa is a framework-forming cold-water coral that supports numerous ecosystem services in the deep ocean. These corals are threatened by increasing anthropogenic impacts to the deep-sea, such as global ocean change and hydrocarbon extraction. This study implemented two sets of experiments to assess the effects of future conditions (temperature: 8 °C and 12 °C, pH: 7.9 and 7.6) and hydrocarbon exposure (oil, dispersant, oil + dispersant combined) on coral health. Phenotypic response was assessed through three independent observations of diagnostic characteristics that were combined into an average health rating at four points during exposure and recovery. In both experiments, regardless of environmental condition, average health significantly declined during 24-hour exposure to dispersant alone but was not significantly altered in the other treatments. In the early recovery stage (24 hours), polyp health returned to the pre-exposure health state under ambient temperature in all treatments. However, increased temperature resulted in a delay in recovery (72 hours) from dispersant exposure. These experiments provide evidence that global ocean change can affect the resilience of corals to environmental stressors and that exposure to chemical dispersants may pose a greater threat than oil itself.
... These two systems, while differing slightly in their mechanism of temperature control, utilise similar designs in terms of waste removal and water flow, and each has continuously supported CWCs from September 2009 up until the present day. A detailed description of this system is available in Lunden et al. (2014a). In support of ongoing research activities in the Gulf of Mexico (GoM), the recirculating aquaria at Temple were designed primarily to maintain scleractinian CWCs for global ocean change and anthropogenic disturbance studies (e.g. ...
... Upon return to port, corals were transported overnight to Temple University (Philadelphia, USA) where all the experiments were performed. At the time of arrival, the different collections were split into two 550 L recirculating systems (see Lunden et al. 2014b for full description of the system) with custommade artificial seawater (ASW) prepared using B-ionic ® , and maintained at a temperature of ~ 8 °C, salinity 35ppt and total alkalinity ~ 2300 µmol kg −1 , which simulates conditions at L. pertusa sites (Lunden et al 2013, Georgian et al. 2015. Corals from the parental colonies were cut into small fragments of an average 8 polyps each (range: 5-11) and attached to acrylic plates of 2 cm 2 , fixed with epoxy (Corafix ® ) and placed in the recirculating tanks. ...
Seawater temperature is one of the main variables that determines cold-water coral distribution worldwide. As part of an initiative to explore new areas of deep-sea habitats along the Southeast United States (SEUS) continental margin, a series of expeditions were carried out as part of the Deep-Sea Exploration to Advance Research on Corals/Canyons/Cold seeps (DEEP SEARCH) project. During these explorations, a cold-water coral reef complex composed mainly of Lophelia pertusa was located off the coast of South Carolina at 650–850 m depth. In this geographic area the species normally has a thermal tolerance between 6 and 12 °C with the capacity to form extensive calcium carbonate structures, thus creating complex habitat for a variety of associated species. Owing to the paucity of these structures and the unusual environmental conditions of this geographic area, with regular arrival of warm surface waters from the Gulf Stream, the main aim of this study was to understand the physiological response of L. pertusa to the variation in extreme temperature events in this region. Short-term experiments simulated the rate of temperature increase from the ambient temperature (8 °C) to the environmental maximum (14 °C) (heat-wave treatment). We found that temperature had a significant effect on the metabolic functions through an increase in respiration (0.108 to 0.247 µmol O2 g−1DW h−1) and excretion rates (0.002 to 0.011 µmol NH3 g−1DW h−1) at 14 °C. Oxygen to Nitrogen ratios (O:N) also showed an effect of temperature where corals switched from lipid-dominated toward a mix of lipid-protein and protein-dominated catabolism. To further characterize the metabolic response, feeding assays (capture rate of Artemia) were performed at the same temperature range with an overall three-fold decrease in capture rates under 14 °C compared to ambient temperature, thus increasing the probability of temperature-induced metabolic stress. Our results suggest that temperature variations affect the metabolic response of cold-water corals, particularly along the SEUS continental margin. Since the incursion of warm surface water to deeper zones is predicted to increase in frequency and duration due to climate change, L. pertusa may be implicated negatively, followed by ecological consequences for the survival and functionality for the ecosystem it supports.
... These two systems, while differing slightly in their mechanism of temperature control, utilise similar designs in terms of waste removal and water flow, and each has continuously supported CWCs from September 2009 up until the present day. A detailed description of this system is available in Lunden et al. (2014a). In support of ongoing research activities in the Gulf of Mexico (GoM), the recirculating aquaria at Temple were designed primarily to maintain scleractinian CWCs for global ocean change and anthropogenic disturbance studies (e.g. ...
Knowledge on basic biological functions of organisms is essential to understand not only the role they play in the ecosystems but also to manage and protect their populations. The study of biological processes, such as growth, reproduction and physiology, which can be approached in situ or by collecting specimens and rearing them in aquaria, is particularly challenging for deep-sea organisms like cold-water corals. Field experimental work and monitoring of deep-sea populations is still a chimera. Only a handful of research institutes or companies has been able to install in situ marine observatories in the Mediterranean Sea or elsewhere, which facilitate a continuous monitoring of deep-sea ecosystems. Hence, today’s best way to obtain basic biological information on these organisms is (1) working with collected samples and analysing them post-mortem and / or (2) cultivating corals in aquaria in order to monitor biological processes and investigate coral behaviour and physiological responses under different experimental treatments. The first challenging aspect is the collection process, which implies the use of oceanographic research vessels in most occasions since these organisms inhabit areas between ca. 150 m to more than 1000 m depth, and specific sampling gears. The next challenge is the maintenance of the animals on board (in situations where cruises may take weeks) and their transport to home laboratories. Maintenance in the home laboratories is also extremely challenging since special conditions and set-ups are needed to conduct experimental studies to obtain information on the biological processes of these animals. The complexity of the natural environment from which the corals were collected cannot be exactly replicated within the laboratory setting; a fact which has led some researchers to question the validity of work and conclusions drawn from such undertakings. It is evident that aquaria experiments cannot perfectly reflect the real environmental and trophic conditions where these organisms occur, but: (1) in most cases we do not have the possibility to obtain equivalent in situ information and (2) even with limitations, they produce relevant information about the biological limits of the species, which is especially valuable when considering potential future climate change scenarios. This chapter includes many contributions from different authors and is envisioned as both to be a practical “handbook” for conducting cold-water coral aquaria work, whilst at the same time offering an overview on the cold-water coral research conducted in Mediterranean laboratories equipped with aquaria infrastructure. Experiences from Atlantic and Pacific laboratories with extensive experience with cold-water coral work have also contributed to this chapter, as their procedures are valuable to any researcher interested in conducting experimental work with cold-water corals in aquaria. It was impossible to include contributions from all laboratories in the world currently working experimentally with cold-water corals in the laboratory, but at the conclusion of the chapter we attempt, to our best of our knowledge, to supply a list of several laboratories with operational cold-water coral aquaria facilities.
... Experimental exposures at TCNJ were run in artificial seawater (Instant Ocean), mixed to a salinity of 35. Since Instant Ocean is formulated with total alkalinity (TA) above what is found in natural seawater (SW), TA was reduced to ∼2200 µmol kg −1 SW by addition of 12 M HCl (Lunden et al., 2014). The value of ∼2200 µmol kg −1 SW was chosen to approximate typical TA values in Beaufort, NC where the barnacle broodstock was collected. ...
Barnacles are dominant members of marine intertidal communities. Their success depends on firm attachment provided by their proteinaceous adhesive and protection imparted by their calcified shell plates. Little is known about how variations in the environment affect adhesion and shell formation processes in barnacles. Increased levels of atmospheric CO2 have led to a reduction in the pH of ocean waters (i.e., ocean acidification), a trend that is expected to continue into the future. Here, we assessed if a reduction in seawater pH, at levels predicted within the next 200 years, would alter physiology, adhesion, and shell formation in the cosmopolitan barnacle Amphibalanus (=Balanus) amphitrite. Juvenile barnacles, settled on silicone substrates, were exposed to one of three static levels of pHT, 8.01, 7.78, or 7.50, for 13 weeks. We found that barnacles were robust to reduced pH, with no effect of pH on physiological metrics (mortality, tissue mass, and presence of eggs). Likewise, adhesive properties (adhesion strength and adhesive plaque gross morphology) were not affected by reduced pH. Shell formation, however, was affected by seawater pH. Shell mass and base plate area were higher in barnacles exposed to reduced pH; barnacles grown at pHT 8.01 exhibited approximately 30% lower shell mass and 20% smaller base plate area as compared to those at pHT 7.50 or 7.78. Enhanced growth at reduced pH appears to be driven by the increased size of the calcite crystals that comprise the shell. Despite enhanced growth, mechanical properties of the base plate (but not the parietal plates) were compromised at the lowest pH level. Barnacle base plates at pHT 7.50 broke more easily and crack propagation, measured through microhardness testing, was significantly affected by seawater pH. Other shell metrics (plate thickness, relative crystallinity, and atomic disorder) were not affected by seawater pH. Hence, a reduction in pH resulted in larger barnacles but with base plates that would crack more readily. It is yet to be determined if such changes would alter the survival of A. amphitrite in the field, but changes in the abundance of this ecologically dominant species would undoubtedly affect the composition of biofouling communities.
... Few studies have used a static or recirculating exposure system, due to challenges such as frequent water changes, organismal fouling, and how to effectively restore pCO 2 to ambient levels in recirculated waters. Studies that have measured coral calcification rates in response to elevated pCO 2 without a flow-through water regime include the Biosphere 2 coral reef biome (recirculating system with water volume of 2650-m 3 ; Langdon et al., 2003), 8-L static mesocosms requiring frequent water changes (Renegar and Riegl, 2005), and an experimental system consisting of three, independent recirculating aquaria (Lunden et al., 2014). Interestingly, the experimental design of a study can seemingly influence the observed response to acidification. ...
Projected increases in ocean pCO2 levels are anticipated to affect calcifying organisms more rapidly and to a greater extent than other marine organisms. The effects of ocean acidification (OA) have been documented in numerous species of corals in laboratory studies, largely tested using flow-through exposure systems. We developed a recirculating ocean acidification exposure system that allows precise pCO2 control using a combination of off-gassing measures including aeration, water retention devices, venturi injectors, and CO2 scrubbing. We evaluated the recirculating system performance in off-gassing effectiveness and maintenance of target pCO2 levels over an 84-day experiment. The system was used to identify changes in calcification and tissue growth in response to elevated pCO2 (1000 μatm) in three reef-building corals of the Caribbean: Pseudodiploria clivosa, Montastraea cavernosa, and Orbicella faveolata. All three species displayed an overall increase in net calcification over the 84-day exposure period regardless of pCO2 level (control + 0.28–1.12 g, elevated pCO2 + 0.18–1.16 g), and the system was effective at both off-gassing acidified water to ambient pCO2 levels, and maintaining target elevated pCO2 levels over the 3-month experiment.
... Manipulation of corals and general work with deep-sea coral in lab Although L. pertusa is well adapted to life in the deep, this species seems to tolerate lab conditions at atmospheric pressure. L. pertusa was noted to thrive in the lab for several months provided stable water conditions were maintained (Lunden et al., 2014;Mortensen, 2001;Orejas et al., 2011b). However, food availability and water flow need to be carefully considered, in addition to water Figure 6a. ...
Despite the importance of the cold-water coral Lophelia pertusa to deep-sea reef ecosystem functioning, current knowledge of key physiological responses to available food resources is scarce. Scenarios with varying food density may help to understand how corals deal with seasonal variations in the dark ocean and might be used to study consequences of anthropogenic activities potentially affecting food availability. Thus, the physiological responses of L. pertusa to varying food (Artemia salina nauplii) concentration, ranging from 20% to 300% of carbon equivalent turned over by basal coral respiration, were investigated. A starvation group was also included. Measurements of respiration, growth, mucus production, and energy reserves (storage fatty acids) were performed at several time intervals over 26 weeks. In general, data showed a stronger effect of experimental time on measured responses, but no significant influence of food density treatment. In starved corals, respiration rate declined to 52% of initial respiration, while skeleton growth rate was maintained at the same rate as Artemia-fed corals throughout the investigation. Mucus production measured as the sum of dissolved organic carbon (DOC) and particulate organic carbon (POC) was also similar across food treatments, but POC production exceeded that of DOC at the highest food density. No marked effect was observed on storage fatty acids. These results confirm that L. pertusa is highly resilient to environmental conditions with suboptimal food densities over a time scale of months. Regulation of several physiological processes, including respiration and mucus production, possibly in combination with an opportunistic feeding strategy, contributed to this tolerance to maintain viable corals. Thus, it appears that L. pertusa is well adapted to life in the deep sea.
... Corals were sampled within a depth range of 450-500 m from visually distinct colonies separated by at least 20-30 m to avoid sampling identical genotypes (sensu Lunden et al. 2014a) and returned to the surface in a temperature-insulated 'biobox'. After collection, corals were transferred to Temple University (Philadelphia, PA, USA) and housed in a 550-l maintenance aquarium system as described in Lunden et al. (2014b) for approximately 7 months prior to experimentation. ...
While ocean acidification is a global issue, the severity of ecosystem effects is likely to vary considerably at regional scales. The lack of understanding of how biogeographically separated populations will respond to acidification hampers our ability to predict the future of vital ecosystems. Cold-water corals are important drivers of biodiversity in ocean basins across the world and are considered one of the most vulnerable ecosystems to ocean acidification. We tested the short-term physiological response of the cold-water coral Lophelia pertusa to three pH treatments (pH = 7.9, 7.75 and 7.6) for Gulf of Mexico (USA) and Tisler Reef (Norway) populations, and found that reductions in seawater pH elicited contrasting responses. Gulf of Mexico corals exhibited reductions in net calcification, respiration and prey capture rates with decreasing pH. In contrast, Tisler Reef corals showed only slight reductions in net calcification rates under decreased pH conditions while significantly elevating respiration and capture rates. These differences are likely the result of environmental differences (depth, pH, food supply) between the two regions, invoking the potential for local adaptation or acclimatization to alter their response to global change. However, it is also possible that variations in the methodology used in the experiments contributed to the observed differences. Regardless, these results provide insights into the resilience of L. pertusa to ocean acidification as well as the potential influence of regional differences on the viability of species in future oceans.
... Commercial mixtures of ASW (such as Instant Ocean TM ) are highly buffered and have total alkalinity (TA) values significantly higher than true ocean values (2100 to 2400 lmolÁkg À1 ). Therefore, prior to setting up our experimental treatments, we reduced the TA of our ASW to 2300 lmolÁkg À1 using 12 M hydrochloric acid as described in Lunden et al. (2014). Knocking down TA in commercial ASW mixtures is necessary to reduce the buffering capacity so that target pH values can be achieved using CO 2 gas. ...
Increasing sea-surface temperatures and ocean acidification (OA) are impacting physiologic processes in a variety of marine organisms. Many sea anemones, corals and jellies in the phylum Cnidaria form endosymbiotic relationships with Symbiodinium spp. (phylum Dinoflagellata) supply the hosts with fixed carbon from photosynthesis. Much work has focused on the generally negative effects of rising temperature and OA on calcification in Symbiodinium-coral symbioses, but has not directly measured symbiont photosynthesis in hospite or fixed carbon translocation from symbiont to host. Symbiodinium species or types vary in their environmental tolerance and photosynthetic capacity; therefore, primary production in symbiotic associations can vary with symbiont type. However, symbiont type has not been identified in a large portion of Symbiodinium-cnidarian studies. Future climate conditions and OA may favor non-calcifying, soft-bodied cnidarians, including zoanthids. Here we show that two zoanthid species, Palythoa sp. and Zoanthus sp., harboring different symbiont types (C1 and A4), had very different responses to increased temperature and increased partial pressure of CO2 (pCO2), or dissolved CO2, and low pH. Thermal stress did not affect carbon fixation or fixed carbon translocation in the Zoanthus sp./A4 association, and high pCO2/low pH increased carbon fixation. In contrast, both thermal stress and high pCO2/low pH greatly inhibited carbon fixation in the Palythoa sp./C1 association. However, the combined treatment of high temperature and high pCO2 increased carbon fixation relative to the treatment of high temperature alone. Our observations support the growing body of evidence that demonstrates that the response of symbiotic cnidarians to thermal stress and OA must be considered on a host-specific and symbiont-specific basis. In addition, we show that the effects of increased temperature and pCO2 on photosynthesis may change when these two stressors are combined. Understanding how carbon fixation and translocation varies among different host-symbiont combinations is critical to predicting which Symbiodinium associations may persist in warm, acidified oceans. DOI: 10.1111/maec.12291
... In order to manipulate pH in commercial ASW using CO 2 gas, the buffering capacity of the ASW must be reduced. Therefore, prior to experimentation, TA of the ASW was reduced to 2300 µmol kg -1 using a single injection of 12 M hydrochloric acid (Lunden et al., 2014). Treated ASW was then left to equilibrate in aerated open-air containers for two days, or until pH stabilized at 8.1. ...
Carbon dioxide (CO2) makes up less than 1% of dissolved inorganic carbon (DIC) in the ocean. To acquire carbon dioxide for photosynthesis, many marine autotrophs rely on the enzyme carbonic anhydrase (CA) to catalyze the conversion of bicarbonate ions (HCO3−) to CO2. In zoanthids and other cnidarians with Symbiodinium spp. endosymbionts, CA is essential for transporting CO2 to symbionts for photosynthesis. Temperature and ambient DIC affect CA activity, therefore, increased sea water temperatures and ocean acidification (OA) will alter CO2 transport in symbiotic cnidarians. However, these effects are likely to be species specific for both host and symbiont, as different cnidarians and Symbiodinium spp. vary in their mechanisms of DIC transport and utilization of CA. In this study, host and symbiont CA activity in the zoanthids Palythoa sp. and Zoanthus sp. varied with thermal stress and low pH. Increased temperature inhibited algal, but not host CA activity in Zoanthus sp. polyps with A4 Symbiodinium, while temperature had no effect on CA activity in Palythoa sp. with C1 Symbiodinium. High pCO2/low pH altered algal CA activity in both zoanthid species, but host CA activity changed in Zoanthus sp. polyps only. This study shows that thermal stress and OA induce species-specific changes in CA activity, and thus DIC transport in symbiotic zoanthids. These observations suggest that CA activity in symbiotic cnidarians will be altered by climate conditions predicted for the future, and for some cnidarians, changes in CA activity may inhibit photosynthesis.
... ASW allowed us to accurately maintain desired salinity and temperature for large volumes of water without the potential for introducing contaminants from the ship's seawater system, and to avoid the unreliability of collecting buckets of seawater from over the side in variable sea states. We have used ASW to maintain other coldwater coral species alive in laboratory aquaria for extended periods of time without adverse affects (Lunden et al., 2014). ...
The 2010 Deepwater Horizon (DWH) disaster released an unprecedented amount of oil at depth in the Gulf of Mexico, with known adverse effects on deep-sea coral ecosystems. During the ensuing cleanup efforts, dispersants were also applied at depth for the first time. The ultimate fate of these pollutants is still under investigation, although evidence suggests a large portion was retained in deep waters and sediments. However, the response of deep-sea organisms to both the oil and dispersant are not fully understood. Quantifying these effects on the surrounding communities is crucial to determining long-term environmental consequences. We conducted live exposure experiments to investigate the physiological effects and toxicity of oil and dispersants on two deep-sea corals, Callogorgia delta and Paramuricea type B3. For both species, the treatments containing dispersants had a more pronounced effect than oil treatments alone. In addition, RNA from unexposed and DWH spill-impacted Paramuricea biscaya was extracted and sequenced using Illumina technology to investigate changes in gene expression. This lead to the production of a de novo reference transcriptome, which we used to investigate possible gene expression changes in response to environmental stressors. Current findings show an up-regulation of genes coding for Cytochrome p450 (CYP1A1), Tumor necrosis factor receptor-associated factors (TRAFs), Peroxidasin and additional genes involved in innate immunity and apoptotic pathways. CYP1A1 is involved in the metabolism of xenobiotics and has been used as a diagnostic tool in several studies looking at toxin exposure. TRAFs are responsible for regulating pathways involved in immune and inflammatory responses and have been found to be overexpressed in corals exposed to thermal stress. Ribosomal proteins and related-HSP90 proteins were also significantly down-regulated in addition to other processes that play a role in apoptosis. Our results provide insights into the responses of deep-sea corals to toxin exposure, implications of applying dispersants to oil spills and a novel reference assembly for a relatively under-studied group of corals.
... ASW allowed us to accurately maintain desired salinity and temperature for large volumes of water without the potential for introducing contaminants from the ship's seawater system, and to avoid the unreliability of collecting buckets of seawater from over the side in variable sea states. We have used ASW to maintain other coldwater coral species alive in laboratory aquaria for extended periods of time without adverse affects (Lunden et al., 2014). ...
... ASW allowed us to accurately maintain desired salinity and temperature for large volumes of water without the potential for introducing contaminants from the ship's seawater system, and to avoid the unreliability of collecting buckets of seawater from over the side in variable sea states. We have used ASW to maintain other cold-water coral species alive in laboratory aquaria for extended periods of time without adverse affects (Lunden et al., 2014). ...
Cold-water corals serve as important foundation species by building complex habitat within deep-sea benthic communities. Little is known about the stress response of these foundation species yet they are increasingly exposed to anthropogenic disturbance as human industrial presence expands further into the deep sea. A recent prominent example is the Deepwater Horizon oil-spill disaster and ensuing clean-up efforts that employed chemical dispersants. This study examined the effects of bulk oil-water mixtures, water-accommodated oil fractions, the dispersant Corexit9500A®, and the combination of hydrocarbons and dispersants on three species of corals living near the spill site in the Gulf of Mexico between 500–1100 m depths: Paramuricea sp. B3, Callogorgia delta and Leiopathes glaberrima. Following short-term toxicological assays (0–96 h), all three coral species examined showed more severe health declines in response to dispersant alone (2.3–3.4 fold) and the oil-dispersant mixtures (1.1–4.4 fold) than in the oil-only treatments. Higher concentrations of dispersant alone and the oil-dispersant mixtures resulted in more severe health declines. C. delta exhibited somewhat less severe health declines than the other two species in response to oil and oil/dispersant mixture treatments, likely related to its increased abundance near natural hydrocarbon seeps. These experiments provide direct evidence for the toxicity of both oil and dispersant on deep-water corals, which should be taken into consideration in the development of strategies for intervention in future oil spills.
Sampling deep-sea biota is a significant challenge because of the logistics required, in terms of vessels and equipment, to obtain minimally preserved specimens. Traditional methods (trawls, nets, and dredges) cause physical damage, stress, and even contamination during the process of removal from the seabed and their displacement through the water column to the surface. Preserving conditions similar to those found in situ is particularly important when the sampling strives to maintain living organisms and for analyses where contamination or degradation by stress or damage may interfere with the results. Therefore, for the sampling and storage of this biota with less interference, a polypropylene box was designed based on the model of Kellogg et al. (2009) incorporating adaptations to be used by a Remotely Operated Vehicle (ROV). This new device has been successfully used in eight oceanographic campaigns, adequately performing for sediment and biota sampling, including coral reef forming or framework species (Scleractinia), octocorals, associated fauna, and rhodoliths, at depths between 50 and 900 m.
The rise of CO2 has been identified as a major threat to life in the ocean. About one-third of the anthropogenic CO2 produced in the last 200 yr has been taken up by the ocean, leading to ocean acidification. Surface seawater pH is projected to decrease by about 0.4 unit between the pre-industrial revolution and 2100. The branching cold-water corals Madrepora oculata and Lophelia pertusa are important, habitat-forming species in the deep Mediterranean Sea. Although previous research has investigated the abundance and distribution of these species, little is known regarding their ecophysiology and potential responses to global environmental change. A previous study indicated that the rate of calcification of these two species remained constant up to 1000 μatm CO2 a value that is at the upper end of changes projected to occur by 2100. We examined whether the ability to maintain calcification rates in the face of rising pCO2 affected the energetic requirements of these corals. Over the course of three months, rates of respiration were measured at a pCO2 ranging between 350 and 1100 μatm to distinguish between short-term response and longer-term acclimation. Respiration rates ranged from 0.074 to 0.266 μmol O2 (g skeletal dry weight)−1 h−1 and 0.095 to 0.725 μmol O2 (g skeletal dry weight)−1 h−1 for L. and M. oculata, respectively, and were independent of pCO2. Respiration increased with time likely due to regular feeding which may have provided an increased energy supply to sustain coral metabolism. Future studies are needed to confirm whether the insensitivity of respiration to increasing pCO2 is a general feature of deep-sea corals in other regions.
A list of 138 positions with records of Lophelia pertusa is compiled from all published and unpublished investigations in the area including material from the BIOFAR research programme. In addition, Solenosmilia variabilis, another species of branching coral new to the area is reported. The Lophelia records are from areas that are dominated by the northeastern Atlantic water (NEA W) and in depths from 200 to c. 1000 m. The highest abundance of Lophelia tends to be in the depth range where the bottom slope is critical to internal waves of semidiurnal frequency. The causal link behind this is suggested to be an increase of food availability either through higher primary production at the surface or by a redistribution of suspended particles in the bottom mixed layer.
Significance
Fish appear to be absent from the ocean's greatest depths, the trenches from 8,400–11,000 m. The reason is unknown, but hydrostatic pressure is suspected. We propose that the answer is the need for high levels of trimethylamine oxide (TMAO, common in many marine animals), a potent stabilizer capable of counteracting the destabilization of proteins by pressure. TMAO is known to increase with depth in bony fishes (teleosts) down to 4,900 m. By capturing the world's second-deepest known fish, the hadal snailfish Notoliparis kermadecensis from 7,000 m, we find that they have the highest recorded TMAO contents, which, moreover, yield an extrapolated maximum for fish at about 8,200 m. This is previously unidentified evidence that biochemistry may constrain depth for a large taxonomic group.
Cold-water corals are associated with high local biodiversity, but despite their importance as ecosystem engineers, little is known about how these organisms will respond to projected ocean acidification. Since preindustrial times, average ocean pH has decreased from 8.2 to ~8.1, and predicted CO2 emissions will decrease by up to another 0.3 pH units by the end of the century. This decrease in pH may have a wide range of impacts upon marine life, and in particular upon calcifiers such as cold-water corals. Lophelia pertusa is the most widespread cold-water coral (CWC) species, frequently found in the North Atlantic. Here, we present the first short-term (21 days) data on the effects of increased CO2 (750 ppm) upon the metabolism of freshly collected L. pertusa from Mingulay Reef Complex, Scotland, for comparison with net calcification. Over 21 days, corals exposed to increased CO2 conditions had significantly lower respiration rates (11.4±1.39 SE, µmol O2 g−1 tissue dry weight h−1) than corals in control conditions (28.6±7.30 SE µmol O2 g−1 tissue dry weight h−1). There was no corresponding change in calcification rates between treatments, measured using the alkalinity anomaly technique and 14C uptake. The decrease in respiration rate and maintenance of calcification rate indicates an energetic imbalance, likely facilitated by utilisation of lipid reserves. These data from freshly collected L. pertusa from the Mingulay Reef Complex will help define the impact of ocean acidification upon the growth, physiology and structural integrity of this key reef framework forming species.
(1) Oceanic CO2 levels are expected to rise during the next 2 centuries to levels not seen for 10-150 million years by the uptake of atmospheric CO2 in surface waters or potentially through the disposal of waste CO2 in the deep sea. Changes in ocean chemistry caused by CO2 influx may have broad impacts on ocean ecosystems. Physiological processes animals use to cope with CO2-related stress are known, but the range of sensitivities and effects of changes in ocean chemistry on most ocean life remain unclear. We evaluate the effectiveness of various designs for in situ CO2 release experiments in producing stable perturbations in seawater chemistry over experimental seafloor plots, as is desirable for evaluating the CO2 sensitivities of deep sea animals. We also discuss results from a subset of these experiments on the impacts of hypercapnia on deep sea meiofauna, in the context of experimental designs. Five experiments off central California show that pH perturbations were greatest for experiments using ''point source'' CO2 pools surrounded by experimental plots. CO2 enclosure experiments with experimental plots positioned within a circular arrangement of CO2 pools had more moderate pH variation. The concentration of dissolution plumes from CO2 pools were related to the speed and turbulence of near-bottom currents, which influence CO2 dissolution and advection. Survival of meiofauna (nematodes, amoebae, euglenoid flagellates) was low after episodic severe hypercapnia but lower and variable where pH changes ranged from 0 to 0.2 pH units below normal.
On the upper slope of the northern Gulf of Mexico, topographic features are often associated with authigenic carbonate, which provides hard substrate for sessile benthic communities. At depths >300 m, large Lophelia pertusa colonies frequently occur on these carbonate outcroppings. Surficial sediments at these depths are dominated by fine-grained particulates, which are readily resuspended during the episodic high current events that have been documented for the Gulf of Mexico. Colonies of L. pertusa found in the deep Gulf of Mexico exhibit 2 distinct growth forms: the very heavily calcified 'brachycephala' and the more fragile 'gracilis'. The objective of this research was to determine the tolerance of these 2 morphotypes to suspended sediment and to complete burial, using sediment collected from the study region, Results demonstrated that, although both morphotypes of L. pertusa can tolerate fairly heavy sediment conditions, mortality increases rapidly with longer burial or higher sediment loads.
This study characterized the response to thermal stress in 3 kelp species to contribute to the un- derstanding of the role of the heat shock response in species distributions and in native-invasive species in- teractions. We sampled the invasive kelp Undaria pin- natifida in its native range in Japan and its introduced range in California, USA, to investigate small- and large-scale differences in its response to temperature stress. We then conducted similar experiments on native kelp species in different habitats in California to investigate differences in the response among species and habitats. We examined temperature response by measuring the induction of the gene (hsp70) that en- codes for heat shock protein 70 (Hsp70), which protects cellular proteins from mis-folding and degradation by environmental stress. Individuals of U. pinnatifida, and the native California species Egregia menziesii and Pterygophora californica were heat-shocked at a range of temperatures, and mRNA was extracted and ana- lyzed for expression of hsp70. Significant differences in the timing and magnitude of hsp70 induction were ob- served between intertidal and harbor populations of U. pinnatifida within a few meters of each other in Japan, indicating environmentally driven variability in this re- sponse. Similarly, intertidal and subtidal populations of E. menziesii showed different responses, with subtidal E. menziesii populations responding more like subti- dal P. californica populations. Native California species showed similar magnitudes of expression across all population, while U. pinnatifida collected from Califor- nia harbors exhibited a more robust hsp70 response than native California species but was similar in magni- tude to Japanese populations sampled.
Ocean acidification caused by anthropogenic uptake of CO2 is perceived to be a major threat to calcifying organisms. Cold-water corals were thought to be strongly affected by a decrease in ocean pH due to their abundance in deep and cold waters which, in contrast to tropical coral reef waters, will soon become corrosive to calcium carbonate. Calcification rates of two Mediterranean cold-water coral species, Lophelia pertusa and Madrepora oculata, were measured under variable partial pressure of CO2 (pCO2) that ranged between 380 µatm for present-day conditions and 930 µatm for the end of the century. The present study addressed both short- and long-term responses by repeatedly determining calcification rates on the same specimens over a period of 9 months. Besides studying the direct, short-term response to elevated pCO2 levels, the study aimed to elucidate the potential for acclimation of calcification of cold-water corals to ocean acidification. Net calcification of both species was unaffected by the levels of pCO2 investigated and revealed no short-term shock and, therefore, no long-term acclimation in calcification to changes in the carbonate chemistry. There was an effect of time during repeated experiments with increasing net calcification rates for both species, however, as this pattern was found in all treatments, there is no indication that acclimation of calcification to ocean acidification occurred. The use of controls (initial and ambient net calcification rates) indicated that this increase was not caused by acclimation in calcification response to higher pCO2. An extrapolation of these data suggests that calcification of these two cold-water corals will not be affected by the pCO2 level projected at the end of the century.
The rise of CO2 has been identified as a major threat to life in the ocean. About one-third of the anthropogenic CO2 produced in the last 200 years has been taken up by the ocean, leading to ocean acidification. Surface seawater pH is projected to decrease by about 0.4 unit between the pre- industrial revolution and 2100. The branching cold-water corals Madrepora oculata and Lophelia pertusa are important, habitat-forming species in the deep Mediterranean Sea. Although previous research has investigated the abundance and distribution of these species, little is known regarding their ecophysiology and potential responses to global environmental change. A previous study indicated that the rate of calcification of these two species remained constant up to 1000 μatm CO2, a value that is at the upper end of changes projected to occur by 2100. We examined whether the ability to maintain calcification rates in the face of rising pCO2 affected the energetic requirements of these corals. Over the course of three months, rates of respiration were measured at a pCO2 ranging between 350 and 1100 μatm to distinguish between short-term response and longer-term acclimation. Respiration rates ranged from 0.074 to 0.266 μmol O2 (g skeletal dry weight)-1 h-1 and 0.095 to 0.725 μmol O2 (g skeletal dry weight)-1 h-1 for L. pertusa and M. oculata, respectively, and were independent of pCO2. Respiration increased with time likely due to regular feeding which may have provided an increased energy supply to sustain coral metabolism. Future studies are needed to confirm whether the insensitivity of respiration to increasing pCO2 is a general feature of deep-sea corals in other regions.
We investigated the interactions between the cold-water coral Lophelia pertusa and its associated polychaete Eunice norvegica by quantifying carbon (C) and nitrogen (N) budgets of tissue assimilation, food partitioning, calcification and respiration using (13)C and (15)N enriched algae and zooplankton as food sources. During incubations both species were kept either together or in separate chambers to study the net outcome of their interaction on the above mentioned processes. The stable isotope approach also allowed us to follow metabolically derived tracer C further into the coral skeleton and therefore estimate the effect of the interaction on coral calcification. Results showed that food assimilation by the coral was not significantly elevated in presence of E. norvegica but food assimilation by the polychaete was up to 2 to 4 times higher in the presence of the coral. The corals kept assimilation constant by increasing the consumption of smaller algae particles less favored by the polychaete while the assimilation of Artemia was unaffected by the interaction. Total respiration of tracer C did not differ among incubations, although E. norvegica enhanced coral calcification up to 4 times. These results together with the reported high abundance of E. norvegica in cold-water coral reefs, indicate that the interactions between L. pertusa and E. norvegica can be of high importance for ecosystem functioning.
Growth and behaviour of Lophelia pertusa and selected associated invertebrates were observed in aquaria with running sea-water. The coral polyps captured food particles by means of nematocyst adhesion. Food items up to 2 cm long were ingested. The polyps discriminated between food and sediment particles when presented separately, probably involving chemoreceptors. When presented together with food, sediment was ingested. Linear skeletal extension occurred in pulses of up to 1.2 mm.day-1 in young polyps (mean = 9.4 mm.yr-1). Factors influencing the linear extension were: food availability, water quality, and patterns of water flow. The highest extension rate was recorded in periods with influx of new water masses to the aquarium water intake, and in parts of the aquaria with a slow water movement and a high sedimentation rate. Settlement and reproduction of the parasitic foraminiferan Hyrrokkin sarcophaga was observed, but no clear negative effects on the coral could be observed. The polychaete Eunice norvegica appeared to be a non-obligate mutualist. It frequently "stole" food from Lophelia, cleaned the polyps from sediment particles, and it's tube-building stimulated the production of coral skeleton. The latter probably strengthens both polychaete tube and coral skeleton. Two species of polynoids lived as commensals with Eunice.
The consequences of ocean acidification to benthic organisms and ecosystems could be significant but are, overall, poorly known and quantified at this time. By integrating the current knowledge on the effects of ocean acidification on major benthic biogeochemical processes, individual benthic organisms, and observed characteristics of benthic environments as a function of seawater carbonate chemistry, it is possible to draw some general conclusions regarding the response of benthic organisms and ecosystems to a world of increasingly higher atmospheric CO2 levels. Large-scale geographical and spatial differences in seawater carbonate system chemistry, owing to both natural and anthropogenic processes, provide a powerful means to evaluate the effects of ocean acidification on marine benthic systems. Based on this approach, it is concluded that benthic biogeochemical processes such as calcification and CaCO3 dissolution as well as the community composition of benthic ecosystems will most likely be significantly altered by ocean acidification.
Seagrasses, marine flowering plants, have a long evolutionary history but are now challenged with rapid environmental changes as a result of coastal human population pressures. Seagrasses provide key ecological services, including organic carbon production and export, nutrient cycling, sediment stabilization, enhanced biodiversity, and trophic transfers to adjacent habitats in tropical and temperate regions. They also serve as “coastal canaries,” global biological sentinels of increasing anthropogenic influences in coastal ecosystems, with large-scale losses reported worldwide. Multiple stressors, including sediment and nutrient runoff, physical disturbance, invasive species, disease, commercial fishing practices, aquaculture, overgrazing, algal blooms, and global warming, cause seagrass declines at scales of square meters to hundreds of square kilometers. Reported seagrass losses have led to increased awareness of the need for seagrass protection, monitoring, management, and restoration. However, seagrass science, which has rapidly grown, is disconnected from public awareness of seagrasses, which has lagged behind awareness of other coastal ecosystems. There is a critical need for a targeted global conservation effort that includes a reduction of watershed nutrient and sediment inputs to seagrass habitats and a targeted educational program informing regulators and the public of the value of seagrass meadows.
Since the beginning of the industrial revolution, the concentration of the greenhouse gas carbon dioxide in the atmosphere has increased from 275 to 370 ppm; the increase is thought to have caused much of the rise in global temperature that has occurred during the same period. A means of mitigating its effects is to collect industrial carbon dioxide and sequester it in the deep ocean. Knowledge of effects of such sequestration on deep-sea organisms is crucial to evaluation of the wisdom of deep-ocean sequestration. We therefore tested deep-sea animals for indications that exposure to carbon dioxide-rich seawater is stressful, Our study site was at 3087 rn depth off the coast of central California (36 degrees 41.91'N, 123 degrees 0.14' W). We deployed liquid carbon dioxide in open-topped containers on the sea floor. The carbon dioxide reacted with the carbonate system in the overlying seawater, and carbon dioxide-rich seawater flowed out onto the sediment. We placed inverted funnel traps near the containers and similar to 75 rn away from them. Measurements of pH confirmed that the area near the containers was exposed to carbon dioxide-rich seawater. As a test taxon, we chose harpacticoid copepods. The traps near the source of the carbon dioxide-rich seawater caught significantly more harpacticoids than those far from it. The harpacticoids apparently attempted to escape from the advancing front of carbon dioxide-rich seawater and therefore presumably found exposure to it to be stressful.
In the north-east Atlantic, the dominant reef-framework forming coral species, Lophelia
pertusa and Madrepora
oculata, form a symbiotic association with the polychaete worm Eunice
norvegica. The polychaete–coral symbiosis was studied by visually observing and photographing live animals in aquaria over many months and using time-lapse video under infra-red lighting to record activity patterns. The polychaetes act as reef aggregating agents by joining coral colonies and enhancing the development of reef patches in deep water. The symbiosis was investigated using samples collected from a relatively shallow site in a Norwegian fjord and from a deeper open ocean site in the Porcupine Seabight. The potential functional roles of this symbiosis are considered. The reef aggregating behaviour of the polychaete symbiont allied with the ability of the coral host to anastomose its branches, the polychaete tubes and debris falling onto the reef structure will help to shift the balance between reef growth and (bio)erosion in favour of growth.
Research into the effects of ocean acidification (OA) on marine organisms has greatly increased during the past decade, as realization of the potential dramatic impacts has grown. Studies have revealed the multifarious respon-ses of organisms to OA conditions, indicating a high level of intra-and interspecific variation in species' ability to accommodate these alterations. If we are to provide policy makers with sound, scientific input regarding the expected consequences of OA, we need a broader understanding of these predicted changes. As a group of 20 multi-disci-plinary postgraduate students from around the globe, with a study focus on OA, we are a strong representation of 'next generation' scientists in this field. In this unique cumulative paper, we review knowledge gaps in terms of assessing the biological impacts of OA, outlining directions for future research.
Keeping deep corals alive under optimum water temperature and quality conditions is not an easy task. It is important to achieve a balance among a high-water renewal rate, constant water temperature, flow speed, and nutrient concentrations (especially ammonium). In trying to find a "meeting point" among all of these factors, the ZAE (Experimental Aquaria Area) of the Instituto de Ciencias del Mar (CSIC) in Barcelona developed an aquarium system that maintains constant temperature conditions in an open water circuit for five deep coral species being kept for HERMES project experimental purposes (Figure 1). The new system operates with a temperature variation of ± 0.2°C, allowing culture conditions similar to those in the field.
The Lophelia pertusa community at Viosca Knoll (VK826) is the most extensive found to date in the Gulf of Mexico. As part of a multi-disciplinary study, the physical setting of this area was described using benthic landers, CTD transects and remotely operated vehicle observations. The site was broadly characterised into three main habitats: (1) dense coral cover that resembles biogenic reef complexes, (2) areas of sediment, and (3) authigenic carbonate blocks with sparse coral and chemosynthetic communities. The coral communities were dominated by L. pertusa but also contained numerous solitary coral species. Over areas that contained L. pertusa, the environmental conditions recorded were similar to those associated with communities in the north-eastern Atlantic, with temperature (8.5–10.6 °C) and salinity (∼35) falling within the known species niche for L. pertusa. However, dissolved oxygen concentrations (2.7–2.8 ml l−1) and density (σΘ, 27.1–27.2 kg m−3) were lower and mass fluxes from sediment trap data appeared much higher (4002–4192 mg m−2 d−1). Yet, this species still appears to thrive in this region, suggesting that L. pertusa may not be as limited by lower dissolved oxygen concentrations as previously thought. The VK826 site experienced sustained eastward water flow of 10–30 cm s−1 over the 5-day measurement period but was also subjected to significant short-term variability in current velocity and direction. In addition, two processes were observed that caused variability in salinity and temperature; the first was consistent with internal waves that caused temperature variations of 0.8 °C over 5–11 h periods. The second was high-frequency variability (20–30 min periods) in temperature recorded only at the ALBEX site. A further pattern observed over the coral habitat was the presence of a 24 h diel vertical migration of zooplankton that may form part of a food chain that eventually reaches the corals. The majority of detailed studies concerning local environmental conditions in L. pertusa habitats have been conducted within the north-eastern Atlantic, limiting most knowledge of the niche of this species to a single part of an ocean basin. Data presented here show that the corals at VK826 are subjected to similar conditions in temperature, salinity, and flow velocity as their counterparts in the north-east Atlantic, although values for dissolved oxygen and density (sigma-theta: σΘ) are different. Our data also highlight novel observations of short-term environmental variability in cold-water coral habitat.
We explicitly quantified spatial and temporal patterns in the body temperature of an ecologically important species of intertidal invertebrate, the mussel Mytilus californianus, along the majority of its latitudinal range from Washington to southern California, USA. Using long-term (five years), high-frequency temperature records recorded at multiple sites, we tested the hypothesis that local ''modifying factors'' such as the timing of low tide in summer can lead to large-scale geographic mosaics of body temperature. Our results show that patterns of body temperature during aerial exposure at low tide vary in physiologically meaningful and often counterintuitive ways over large sections of this species' geographic range. We evaluated the spatial correlations among sites to explore how body temperatures change along the latitudinal gradient, and these analyses show that ''hot spots'' and ''cold spots'' exist where temperatures are hotter or colder than expected based on latitude. We identified four major hot spots and four cold spots along the entire geographic gradient with at least one hot spot and one cold spot in each of the three regions examined (Washington– Oregon, Central California, and Southern California). Temporal autocorrelation analysis of year-to-year consistency and temporal predictability in the mussel body temperatures revealed that southern animals experience higher levels of predictability in thermal signals than northern animals. We also explored the role of wave splash at a subset of sites and found that, while average daily temperature extremes varied between sites with different levels of wave splash, yearly extreme temperatures were often similar, as were patterns of predictability. Our results suggest that regional patterns of tidal regime and local pattern of wave splash can overwhelm those of large-scale climate in driving patterns of body temperature, leading to complex thermal mosaics of temperature rather than simple latitudinal gradients. A narrow focus on population changes only at range margins may overlook climatically forced local extinctions and other population changes at sites well within a species range. Our results emphasize the importance of quantitatively examining biogeographic patterns in environ-mental variables at scales relevant to organisms, and in forecasting the impacts of changes in climate across species ranges.
Ocean acidification (OA), a consequence of anthropogenic carbon dioxide emissions, poses a serious threat to marine organisms in tropical, open-ocean, coastal, deep-sea, and high-latitude sea ecosystems. The diversity of taxonomic groups that precipitate calcium carbonate from seawater are at particularly high risk. Here we review the rapidly expanding literature concerning the biological and ecological impacts of OA on calcification, us-ing a cross-scale, process-oriented approach. In comparison to calcification, we find that areas such as fertilization, early life-history stages, and interac-tion with synergistic stressors are understudied. Although understanding the long-term consequences of OA are critical, available studies are largely short-term experiments that do not allow for tests of long-term acclimatization or adaptation. Future research on the phenotypic plasticity of contemporary organisms and interpretations of performance in the context of current en-vironmental heterogeneity of pCO 2 will greatly aid in our understanding of how organisms will respond to OA in the future.
Global environmental changes, including ocean acidification, have been identified as a major threat to scleractinian corals. General predictions are that ocean acidification will be detrimental to reef growth and that 40 to more than 80 per cent of present-day reefs will decline during the next 50 years. Cold-water corals (CWCs) are thought to be strongly affected by changes in ocean acidification owing to their distribution in deep and/or cold waters, which naturally exhibit a CaCO(3) saturation state lower than in shallow/warm waters. Calcification was measured in three species of Mediterranean cold-water scleractinian corals (Lophelia pertusa, Madrepora oculata and Desmophyllum dianthus) on-board research vessels and soon after collection. Incubations were performed in ambient sea water. The species M. oculata was additionally incubated in sea water reduced or enriched in CO(2). At ambient conditions, calcification rates ranged between -0.01 and 0.23% d(-1). Calcification rates of M. oculata under variable partial pressure of CO(2) (pCO(2)) were the same for ambient and elevated pCO(2) (404 and 867 µatm) with 0.06 ± 0.06% d(-1), while calcification was 0.12 ± 0.06% d(-1) when pCO(2) was reduced to its pre-industrial level (285 µatm). This suggests that present-day CWC calcification in the Mediterranean Sea has already drastically declined (by 50%) as a consequence of anthropogenic-induced ocean acidification.
Scleractinian cold-water corals (CWC) represent key taxa controlling deep-sea reef ecosystem functioning by providing structurally complex habitats to a high associated biodiversity, and by fuelling biogeochemical cycles via the release of organic matter. Nevertheless, our current knowledge on basic CWC properties, such as feeding ecology and key physiological processes (i.e. respiration, calcification and organic matter release), is still very limited. Here, we show evidence for the trophic significance of zooplankton, essentially sustaining levels of the investigated key physiological processes in the cosmopolitan CWC Desmophyllum dianthus (Esper 1794). Our results from laboratory studies reveal that withdrawal (for up to 3 weeks) of zooplankton food (i.e. Artemia salina) caused a significant decline in respiration (51%) and calcification (69%) rates compared with zooplankton-fed specimens. Likewise, organic matter release, in terms of total organic carbon (TOC), decreased significantly and eventually indicated TOC net uptake after prolonged zooplankton exclusion. In fed corals, zooplankton provided 1.6 times the daily metabolic C demand, while TOC release represented 7% of zooplankton-derived organic C. These findings highlight zooplankton as a nutritional source for D. dianthus, importantly sustaining respiratory metabolism, growth and organic matter release, with further implications for the role of CWC as deep-sea reef ecosystem engineers.
In order to determine the metal concentrations in cultured oysters from four coastal lagoons from SE Gulf of California, several individuals of Crassostrea gigas and C. corteziensis were collected and their cadmium, copper, lead and zinc levels were measured by atomic absorption spectrometry after acid digestion. The concentration of metals in oyster soft tissue was Zn > Cu > Cd > Pb. In two lagoons, Cd concentrations (10.1-13.5 μg g(-1) dw) exceeded the maximum level allowed according to the Official Mexican Standard (NOM-031-SSA1-1993), which is equivalent to the WHO recommended Cd levels in organisms used for human consumption.
The cold-water coral Lophelia pertusa is one of the few species able to build reef-like structures and a 3-dimensional coral framework in the deep oceans. Furthermore, deep cold-water coral bioherms are likely among the first marine ecosystems to be affected by ocean acidification. Colonies of L. pertusa were collected during a cruise in 2006 to cold-water coral bioherms of the Mingulay reef complex (Hebrides, North Atlantic). Calcium-45 labelling was conducted shortly after sample collection onboard. After this method proved to deliver reliable data, the same experimental approach was used to assess calcification rates and the effect of lowered pH during a~cruise to the Skagerrak (North Sea) in 2007. The highest calcification rates were found in youngest polyps with up to 1% d<sup>−1</sup> new skeletal growth and average values of 0.11±0.02% d<sup>−1</sup>(±S.E.). Lowering the pH by 0.15 and 0.3 units relative to ambient pH resulted in a strong decrease in calcification by 30 and 56%, respectively. The effect of changes in pH on calcification was stronger for fast growing, young polyps (59% reduction) than for older polyps (40% reduction) which implies that skeletal growth of young and fast calcifying corallites will be influenced more negatively by ocean acidification. Nevertheless, L. pertusa revealed a positive net calcification (as indicated by <sup>45</sup>Ca incorporation) at an aragonite saturation state (Ω<sub> a </sub>) below 1, which may indicate some adaptation to an environment that is already relatively low in Ω<sub> a </sub> compared to tropical or temperate coral bioherms.
The diversity, frequency, and scale of human impacts on coral reefs are increasing to the extent that reefs are threatened
globally. Projected increases in carbon dioxide and temperature over the next 50 years exceed the conditions under which coral
reefs have flourished over the past half-million years. However, reefs will change rather than disappear entirely, with some
species already showing far greater tolerance to climate change and coral bleaching than others. International integration
of management strategies that support reef resilience need to be vigorously implemented, and complemented by strong policy
decisions to reduce the rate of global warming.
The absorption of atmospheric carbon dioxide (CO2) into the ocean lowers the pH of the waters. This so-called ocean acidification could have important consequences for marine
ecosystems. To better understand the extent of this ocean acidification in coastal waters, we conducted hydrographic surveys
along the continental shelf of western North America from central Canada to northern Mexico. We observed seawater that is
undersaturated with respect to aragonite upwelling onto large portions of the continental shelf, reaching depths of ∼40 to
120 meters along most transect lines and all the way to the surface on one transect off northern California. Although seasonal
upwelling of the undersaturated waters onto the shelf is a natural phenomenon in this region, the ocean uptake of anthropogenic
CO2 has increased the areal extent of the affected area.
We report results from an oyster hatchery on the Oregon coast, where intake waters experienced variable carbonate chemistry (aragonite saturation state , 0.8 to . 3.2; pH , 7.6 to . 8.2) in the early summer of 2009. Both larval production and midstage growth (, 120 to , 150 mm) of the oyster Crassostrea gigas were significantly negatively correlated with the aragonite saturation state of waters in which larval oysters were spawned and reared for the first 48 h of life. The effects of the initial spawning conditions did not have a significant effect on early-stage growth (growth from D-hinge stage to , 120 mm), suggesting a delayed effect of water chemistry on larval development.
This Guide contains the most up-to-date information available on the chemistry of CO 2 in sea water and the methodology of determining carbon system parameters, and is an attempt to serve as a clear and unambiguous set of instructions to investigators who are setting up to analyze these parameters in sea water.
Ocean acidity has increased by 30% since preindustrial times due to the uptake of anthropogenic CO2 and is projected to rise by another 120% before 2100 if CO2 emissions continue at current rates. Ocean acidification is expected to have wide-ranging impacts on marine life, including reduced growth and net erosion of coral reefs. Our present understanding of the impacts of ocean acidification on marine life, however, relies heavily on results from short-term CO2 perturbation studies. Here, we present results from the first long-term CO2 perturbation study on the dominant reef-building cold-water coral Lophelia pertusa and relate them to results from a short-term study to compare the effect of exposure time on the coral's responses. Short-term (1 week) high CO2 exposure resulted in a decline of calcification by 26–29% for a pH decrease of 0.1 units and net dissolution of calcium carbonate. In contrast, L. pertusa was capable to acclimate to acidified conditions in long-term (6 months) incubations, leading to even slightly enhanced rates of calcification. Net growth is sustained even in waters sub-saturated with respect to aragonite. Acclimation to seawater acidification did not cause a measurable increase in metabolic rates. This is the first evidence of successful acclimation in a coral species to ocean acidification, emphasizing the general need for long-term incubations in ocean acidification research. To conclude on the sensitivity of cold-water coral reefs to future ocean acidification further ecophysiological studies are necessary which should also encompass the role of food availability and rising temperatures.
Ocean acidification, the reduction in pH and calcium carbonate saturation states of seawater, is likely to exhibit its most immediate effects on cold-water corals in deep waters with the shoaling of the aragonite saturation horizon. However, empirical data describing the carbonate chemistry at cold-water coral reefs are very rare. Regions of the upper slope of the Northern Gulf of Mexico harbor several deep-water reefs structured by the scleractinian Lophelia pertusa. We collected discreet water samples at a range of depths in the Gulf of Mexico, including eight Lophelia reefs, and measured total alkalinity and pH to calculate the aragonite saturation state (Ωarag). The deep waters of the Gulf of Mexico (> 300 m depth) were at aragonite saturation states between 0.98 and 1.69. L. pertusa was present at sites with Ωarag between 1.25 and 1.69, and carbonate ion concentrations between 92 and 123 µmol kg−1. These data provide a critical baseline for detecting future changes in carbonate chemistry in the water column (i.e., aragonite saturation horizon shoaling), as well as at the sites of well-developed cold-water coral structures threatened by ongoing ocean acidification.
Water temperature may be a primary exogenous determinant of deep-sea coral distributions. The upper thermal threshold for survival of the deep-water coral Lophelia pertusa (Linnaeus, 1758) is generally accepted to be ~12–14 °C, based on field observations of coral distributions. However, hydrographic conditions over coral mounds are dynamic on various scales, often producing temperature fluctuations of unpredictable duration and magnitude. This study investigated the survival of L. pertusa under a range of experimental temperatures: 5, 8 °C (ambient), 15, 20 and 25 °C, for two experimental durations: 24 h and seven days. There was a significant difference (p<0.001) in survival among temperatures after both the 24 h and the seven day experiments. The experimental data were supported by survival data for coral fragments deployed on benthic landers off North Carolina, where historical data show that temperatures over coral mounds vary greatly and reached 15 °C on a recurring basis. Experimental and in situ data suggested that the upper lethal temperature limit for this deep-sea coral species is near 15 °C. Tolerance to fluctuations in environmental variables, such as temperature, decreases the probability of mortality in the face of anomalous events and/or variable environments. Understanding the eco-physiology of structure forming deep-coral taxa will help inform management strategies; for example, preserving those ecosystems that are more resilient to threats from predicted changes.
I tested the hypothesis that high pCO2 (76.6 Pa and 87.2 Pa vs. 42.9 Pa) has no effect on the metabolism of juvenile massive Porites spp. after 11 days at 28 °C and 545 μmol quanta m−2 s−1. The response was assessed as aerobic dark respiration, skeletal weight (i.e., calcification), biomass, and chlorophyll fluorescence. Corals were collected from the shallow (3–4 m) back reef of Moorea, French Polynesia (17°28.614′S, 149°48.917′W), and experiments conducted during April and May 2011. An increase in pCO2 to 76.6 Pa had no effect on any dependent variable, but 87.2 Pa pCO2 reduced area-normalized (but not biomass-normalized) respiration 36 %, as well as maximum photochemical efficiency (F
v/F
m) of open RCIIs and effective photochemical efficiency of RCIIs in actinic light (∆F/
$ F_{\text{m}}^{\prime } $
); neither biomass, calcification, nor the energy expenditure coincident with calcification (J g−1) was effected. These results do not support the hypothesis that high pCO2 reduces coral calcification through increased metabolic costs and, instead, suggest that high pCO2 causes metabolic depression and photochemical impairment similar to that associated with bleaching. Evidence of a pCO2 threshold between 76.6 and 87.2 Pa for inhibitory effects on respiration and photochemistry deserves further attention as it might signal the presence of unpredictable effects of rising pCO2.
Ecological studies, including those focusing on coastal eutrophication, vary in the emphasis they place on species-level vs. ecosystem-level processes. The degree of variation among interacting species in their response to perturbations to the physical environment is likely to be important in determining when species- or population-level processes will strongly affect attributes measured at higher levels of ecological organization. We conducted mesocosm and small-scale laboratory experiments to determine how low oxygen affects predation rates in a zooplankton-fish larvae-larval predator food web typical of mesohaline areas in the Chesapeake Bay. Dissolved oxygen concentrations in bottom waters of the Chesapeake Bay decline during summer to levels that can be physiologically stressful or lethal to animals dependent on aerobic respiration. Our results indicate that the effects of low oxygen on trophic interactions vary among interacting pairs of species in the food web studied. Low but nonlethal dissolved oxygen concentrations greatly increased predation on fish larvae (mostly naked goby Gobiosoma bosc) by sea nettles (the scyphomedusan jellyfish Chrysaora quinquecirrha) but decreased predation by juvenile striped bass (Morone saxatilis). Predation by a single predator, the sea nettle, increased for fish larvae, decreased for fish eggs (Anchoa mitchilli), and was significantly but not strongly affected for copepods (mostly Acartia tonsa) at low dissolved oxygen concentrations. Changes in predator-prey interactions reflected variation among species in their physiological tolerance to low oxygen and the effects of low oxygen on the escape behavior of prey, as well as on swimming and feeding behaviors of predators. Because of the variation in effects on trophic interactions, low dissolved oxygen has the potential to cause major alterations in the relative importance of different pathways of energy flow in the Chesapeake Bay and in other estuarine systems.
Many deep-sea organisms need hydrostatic pressure for their survival. Thus, when retrieved from their natural environment for biological studies that cannot be conducted at the bottom of ocean, they must be returned to high pressure using appropriate pressure vessels. Our studies of organisms living at deep-sea hydrothermal vents lead us to develop such pressure vessels. Here, we present a system of small pressure reactors that were specifically conceived for the study of embryonic development, but may be also used for the study of small organisms, larvae, cells or bacteria. The system consists of two reactors fed by a common pressure line which can be manipulated separately using a set of valves. It is possible to carry out different operations (renewal of water, sampling) without depressurizing the reactors, a feature which proves crucial when carrying out long-term development experiments (over several days). The system has special chambers equipped with sapphire windows that allow the observation of embryos under pressure using a standard optical microscope. Using this system, we studied for the first time the embryonic development of Alvinella pompejana, one of the most intriguing species colonizing the hydrothermal vents.
Environmental variables that are correlated with depth have been suggested to be among the major forces underlying speciation in the deep sea. This study incorporated phylogenetics and ecological niche models (ENM) to examine whether congeneric species of Callogorgia (Octocorallia: Primnoidae) occupy different ecological niches across the continental slope of the Gulf of Mexico (GoM) and whether this niche divergence could be important in the evolution of these closely related species. Callogorgia americana americana, Callogorgia americana delta and Callogorgia gracilis were documented at 13 sites in the GoM (250-1000 m) from specimen collections and extensive video observations. On a first order, these species were separated by depth, with C. gracilis occurring at the shallowest sites, C. a. americana at mid-depths and C. a. delta at the deepest sites. Callogorgia a. delta was associated with areas of increased seep activity, whereas C. gracilis and C. a. americana were associated with narrow, yet warmer, temperature ranges and did not occur near cold seeps. ENM background and identity tests revealed little to no overlap in ecological niches between species. Temporal calibration of the phylogeny revealed the formation of the Isthmus of Panama was a vicariance event that may explain some of the patterns of speciation within this genus. These results elucidate the potential mechanisms for speciation in the deep sea, emphasizing both bathymetric speciation and vicariance events in the evolution of a genus across multiple regions.
Fall Chinook salmon (Oncorhynchus tshawytscha) initiate spawning in the Hells Canyon reach of the Snake River, Idaho (rkm 240-397), at water temperatures above 16 C. This temperature exceeds the states of Idaho and Oregon water quality standards for salmonid spawning. These standards are consistent with results from studies of embryos exposed to a constant thermal regime, while salmon eggs in the natural environment are rarely exposed to a constant temperature regime. The objective of this study was to assess whether variable temperatures (i.e., declining after spawning) affected embryo survival, development, and growth of Snake River fall Chinook salmon alevins and fry. In 2003, fall Chinook salmon eggs were exposed to initial incubation temperatures ranging from 11-19 C in 2 C increments, and in 2004 eggs were exposed to initial temperatures of 13 C, 15 C, 16 C, 16.5 C, and 17 C. In both years, temperatures were adjusted downward approximately 0.2 C/day to mimic the thermal regime of the Snake River where these fish spawn. At 37-40 days post-fertilization, embryos were moved to a common exposure regime that followed the thermal profile of the Snake River through emergence. Mortality of fall Chinook salmon embryos increased markedly at initial incubation temperatures >17 C in both years. A logistic regression model estimated that a 50% reduction in survival from fertilization to emergence would occur at an initial incubation temperature of â16 C. The laboratory results clearly showed a significant reduction in survival between 15 C and 17 C, which supported the model estimate. Results from 2004 showed a rapid decline in survival occurred between 16.5 C and 17 C, with no significant differences in survival at initial incubation temperatures 0.2 C/day following spawning.
Near-bed hydrodynamic conditions were recorded for almost one year in the Viosca Knoll area (lease block 826), one of the most well-developed cold-water coral habitats in the Gulf of Mexico. Here, a reef-like cold-water coral ecosystem, dominated by the coral Lophelia pertusa, resembles coral habitats found off the southeastern US coast and the North East Atlantic. Two landers were deployed in the vicinity and outside of the coral habitat and measured multiple near-bed parameters, including temperature, salinity, current speed and direction and optical and acoustic backscatter. Additionally, the lander deployed closest to the coral area was equipped with a sediment trap that collected settling particles over the period of deployment at 27 day intervals. Long-term monitoring showed, that in general, environmental parameters, such as temperature (6.5-11.6 degrees C), salinity (34.95-35.4) and current speed (average 8 cm s(-1), peak current speed up to 38 cm s(-1)) largely resembled conditions previously recorded within North East Atlantic coral habitats. Major differences between site VK 826 and coral areas in the NE Atlantic were the much higher particle load, and the origin of the particulate matter. Several significant events occurred during the deployment period beginning with an increase in current speed followed by a gradual increase in temperature and salinity, followed by a rapid decrease in temperature and salinity. Simultaneously with the decrease in temperature and salinity, the direction of the current changed from west to east and cold and less turbid water was transported upslope. The most prominent event occurred in July, when a westward flow lasted over 21 days. These events are consistent with bottom boundary layer dynamics influenced by friction (bottom Ekman layer). The Mississippi River discharges large quantities of sediment and dominates sedimentation regimes in the area. Furthermore, the Mississippi River disperses large amounts of terrestrial organic matter and nutrients, resulting in increased primary productivity, whereby marine organic matter is produced that will sink to the seafloor and can serve as food for the cold-water corals and associated species. As a result mass fluxes from the sediment trap were higher (1120-4479 mg m(-2) day(-1)) than those observed in the North East Atlantic and were highest during periods of westward-flow, which corresponded to warm turbid water. During eastward-flow, colder and less turbid water was pushed upslope, resulting in lower mass fluxes. Trap samples had a low CaCO3, high organic carbon content and high C/N ratios, suggesting a fluvial origin. The high sediment load in the water column can be a limiting factor for coral growth, especially since the corals can be smothered with sediment. However, eastward-flows provided periods of relatively clearer water that can remove sediment from the coral area and allow corals to expel sediment from their polyps. Around Viosca Knoll food supply comes from two possible sources. During April and June several fluorescence peaks were observed near the seabed, showing the arrival of phytodetritus in the area. Furthermore, a consistent diel vertical migration of zooplankton was observed that might provide an additional food source. (C) 2011 Elsevier Ltd. All rights reserved.
Isolations of pressure-adapted deep sea bacteria from depths of 1,400 to 5,100 m resulted in a variety of psychrophilic barotolerant and barophilic strains. Growth rates determined at different pressures indicated a gradual transition between the two types of pressure-adapted isolates. The presence of barotolerant bacteria in deep water, sustained by sinking particulate matter, causes the nonbarophilic response of natural populations, i.e., increased growth after decompression. With increasing pressure-adaptation in barophilic isolates the maximum growth rates at optimum pressures decrease. Thus, the observed general slow-down of microbial activity in the deep sea takes effect regardless of the common occurrence of psychrophilic and barophilic bacteria. The highest degree of barophilism was observed in isolates from nutrient-rich habitats such as intestinal tracts of deep sea animals or decaying carcasses. Detailed studies with an isolate, growing barophilically on a complex as well as a single-carbon-source medium, showed that (1) culturing at pressures lower than optimal for growth resulted in the formation of cell filaments, (2) growth was unaffected by repeated compression/decompression cycles and (3) no perceptible differences in the distribution of radiolabeled carbon from an amino acid mixture occurred in cells grown at, below and above the pressure optimal for growth.
Increasing atmospheric carbon dioxide (CO(2)) concentrations are expected to decrease surface ocean pH by 0.3-0.5 units by 2100 (refs 1,2), lowering the carbonate ion concentration of surface waters. This rapid acidification is predicted to dramatically decrease calcification in many marine organisms(3,4). Reduced skeletal growth under increased CO(2) levels has already been shown for corals, molluscs and many other marine organisms(4-9). The impact of acidification on the ability of individual species to calcify has remained elusive, however, as measuring net calcification fails to disentangle the relative contributions of gross calcification and dissolution rates on growth. Here, we show that corals and molluscs transplanted along gradients of carbonate saturation state at Mediterranean CO(2) vents are able to calcify and grow at even faster than normal rates when exposed to the high CO(2) levels projected for the next 300 years. Calcifiers remain at risk, however, owing to the dissolution of exposed shells and skeletons that occurs as pH levels fall. Our results show that tissues and external organic layers play a major role in protecting shells and skeletons from corrosive sea water, limiting dissolution and allowing organisms to calcify(10,11). Our combined field and laboratory results demonstrate that the adverse effects of global warming are exacerbated when high temperatures coincide with acidification.
The equimolal Tris buffer (0.04 mol/kg-H2O Tris + 0.04 mol/kg-H2O Tris-HCl) prepared in synthetic seawater of salinity 35 has been shown to be stable when sealed in a borosilicate glass bottle with a greased ground-glass stopper (drift rate ≤ 0.0005 in pH per year). The error in pH of such buffers resulting from uncertainties in the preparation of such buffers is typically less than 0.002 in pH (relative to the results of DelValls and Dickson, 1998 [DelValls, T.A., Dickson, A.G., 1998. The pH of buffers based on 2-amino-2-hydroxymethyl-1,3-propanediol (‘tris’) in synthetic sea water. Deep-Sea Research I, 45, 1541–1554]).
Habitat formation by foundation species is a major ecological force affecting community structure in numerous systems. On the upper continental slope of the Gulf of Mexico, the cold-water scleractinian coral Lophelia pertusa creates complex habitat on cold seep-associated carbonates. In this study, the communities associated with the cold-water coral L. pertusa are described from the Gulf of Mexico for the first time. A total of 68 taxa was identified in close association with the coral framework. Three species with specific relationships to L. pertusa were identified: Eunice sp., a polychaete which may facilitate colony formation in L. pertusa; Coralliophila sp., a species of corallivorous gastropod ; and Stenopus sp., a decapod crustacean which may act in a cleaner shrimp role in these habitats. Similarity among coral-associated communities was best explained by similarity in depth of collection and the proportion of live coral in the collections. These variables were somewhat confounded with location as the sites to the east were both shallower and contained higher proportions of live coral; however, distance between collections per se was not as significant in the analyses. The coral-associated communities also showed a low degree of similarity to communities inhabiting vestimentiferan tubeworm aggregations that occur nearby at the same sites. The increased habitat heterogeneity in the coral structure, differences in the niches constructed by the two foundation species, and different direct interspecific interactions between foundation species and members of the associated community contributed to the presence of dissimilar communities in these two biogenic habitats.
Lophelia pertusa is the world's most common and widespread framework-forming cold-water coral. It forms deep-water coral reefs and carbonate mounds supporting diverse animal communities on the continental shelf and on seamounts. These recently discovered ecosystems have been damaged by deep-sea fishing and are threatened by predicted shallowing of the aragonite saturation horizon. Despite this, very little is known about the ecophysiology of L. pertusa and its likely response to environmental changes. Here we describe the first study of the respiratory physiology of L. pertusa and the effects of altered temperature and oxygen level. This study shows that L. pertusa can maintain respiratory independence over a range of PO2 illustrated by a high regulation value (R = 78%). The critical PO2 value of 9–10 kPa is very similar to the lower values of oxygen concentration recorded in the field. This suggests that oxygen level may be a limiting factor in the distribution of this cold-water coral. L. pertusa survived periods of anoxia (1 h), hypoxia (up to 96 h), but high Q10 values revealed sensitivity to short-term temperature changes (6.5–11 °C). For the first time vital data have been gathered on the physiology of this species that is essential to understand distribution and underpin future climate change studies.
The carbonate chemistry of seawater is usually not considered to be an important factor influencing calcium-carbonate-precipitation by corals because surface seawater is supersaturated with respect to aragonite. Recent reports, however, suggest that it could play a major role in the evolution and biogeography of recent corals. We investigated the calcification rates of five colonies of the zooxanthellate coral Stylophora pistillata in synthetic seawater using the alkalinity anomaly technique. Changes in aragonite saturation from 98% to 585% were obtained by manipulating the calcium concentration. The results show a nonlinear increase in calcification rate as a function of aragonite saturation level. Calcification increases nearly 3-fold when aragonite saturation increases from 98% to 390%, i.e., close to the typical present saturation state of tropical seawater. There is no further increase of calcification at saturation values above this threshold. Preliminary data suggest that another coral species, Acropora sp., displays a similar behaviour. These experimental results suggest: (1) that the rate of calcification does not change significantly within the range of saturation levels corresponding to the last glacial-interglacial cycle, and (2) that it may decrease significantly in the future as a result of the decrease in the saturation level due to anthropogenic release of CO2 into the atmosphere. Experimental studies that control environmental conditions and seawater composition provide unique opportunities to unravel the response of corals to global environmental changes.
The importance of adaptation to high pressure has long been implicit in the findings of studies in which 1 atm-adapted species were subjected to elevated pressures. Recent comparative studies have shown that pressure sensitivities of enzymes, structural proteins, and membrane-based systems differ markedly between shallow- and deep-living species. These studies allow operational definition of what constitutes high pressures for different biological structures and processes. These are the habitat (adaptation) pressures at which a given type of system first exhibits reduced perturbation by pressure. These threshold pressures vary among physiological systems, but are similar for a given system among different species. Dehydrogenase enzymes and adenylyl cyclases exhibit threshold perturbation pressures of only 50-100 atm; the Na(+)-K(+)-ATPase of teleost gills appears to have a pressure perturbation threshold near 200 atm, and a similar threshold was found for actin self-assembly. Even this limited sample of physiological processes indicates that the terms deep and high pressure begin to apply at depths of only 500 m or less--and processes yet to be examined in comparative analysis may yield even lower pressure thresholds. The differences in sensitivity to pressure of homologous systems in shallow- and deep-living organisms have implications at several levels of biological organization. The vertical distribution patterns of species in aquatic habitats may be established, in part, by interspecific differences in resistance to pressure. High pressures may restrict the depths to which shallow-living species can penetrate, and the obligately barophilic systems found in deep-living organisms may limit their upper distribution limits. The similarities noted among the adaptations of deep-sea species with different shallow-water ancestors reflect a high degree of convergent evolution in pressure adaptation. It will be interesting to learn if the similarities in pressure-resistance of function among diverse deep-sea species are the result of similar or identical changes at the molecular level, e.g. in protein sequence. Acclimation to pressure may be of widespread occurrence among species that undergo large changes in depth, e.g. during ontogeny. Pressure acclimation may require pressure-regulation of gene expression. Lastly, comparisons of species from the cold deep sea with those from hydrothermal vents have shown that adaptations to both temperature and pressure play critical roles in determining the distribution patterns of deep-living species.
Deep-sea ecosystems contain unique endemic species whose distributions show strong vertical patterning in the case of pelagic animals and sharp horizontal patterning in the case of benthic animals living in or near the deep-sea hydothermal vents. This review discusses the biochemical adaptations that enable deep-sea animals to exploit diverse deep-sea habitats and that help establish biogeographic patterning in the deep-sea. The abilities of deep-sea animals to tolerate the pressure and temperature conditions of deep-sea habitats are due to pervasive adaptations at the biochemical level: enzymes exhibit reduced perturbation of function by pressure, membranes have fluidities adapted to deep-sea pressures and temperatures, and proteins show enhanced structural stability relative to homologous proteins from cold-adapted shallow-living species. Animals from the warmest habitable regions of hydrothermal vent ecosystems have enzymes and mitochondria adapted to high pressure and relatively high temperatures. The low metabolic rates of bathypelagic fishes correlate with greatly reduced capacities for ATP turnover in locomotory muscle. Reduced light and food availability in bathypelagic regions select for low rates of energy expenditure in locomotory activity. Deep-sea animals thus reflect the importance of biochemical adaptations in establishing species distribution patterns and appropriate rates of metabolic turnover in different ecosystems.
Elevated hydrostatic pressure can influence gene and protein expression in both 1 atmosphere-adapted and high pressure-adapted microorganisms. Here we review experiments documenting these effects and describe their significance towards understanding the molecular bases of life in deep-sea high pressure environments.