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Impacts of a shallow shipwreck on a coral reef: A case study from St. Brandon's Atoll, Mauritius, Indian Ocean
Abstract
Shallow shipwrecks, can have severe ecological and toxicological impacts on coral atolls. In 2012, a tuna longliner ran aground on the reef crest of St Brandon’s Atoll, Mauritius, broke up into three pieces which was moved by currents and storms into the lagoon. In the months following the grounding, the coral around the wreck became dead and black. Down-current from the wreck, a dense bloom of filamentous algae (Ulva sp.) attached to coral occurred. To determine the ecological effects of the wreck on the system, the marine biota around the wreck, in the algal bloom, and fish reference zones were counted in 2014. Metal concentrations in reference and affected coral was determined using inductively coupled plasma mass spectrometry (ICP/MS). A pronounced difference was seen in the metal concentration pattern between coral from the wreck- and algal zones, and the coral reference zone. While the wreck zone contained the highest abundance of fish, the fish reference zone had the highest species diversity but with fewer fish. We also counted eleven Critically Endangered hawksbill sea turtles Eretmochelys imbricata and significantly more sea cucumbers in the algal zone than the reference zones. The effects of shipwrecks on coral reefs must be considered a threat over periods of years and should be studied further.
... There are no permanent residents on the reef, with only occasional visitors making landfall. The major driver of pollution, therefore, comes from marine debris [27,68,69]. ...
... There are no permanent residents on the reef, with only occasional visitors making landfall. The major driver of pollution, therefore, comes from marine debris [27], [68,69]. ...
... Although various vessels have been stranded on this reef [70], including one which created a concentrated algal bloom in 2012 [27], satellite image coverage is poor. Only one cloud-free Google Earth image (dating to 2005, Figure 2h) is available, prior to the strandings described in [27,70]. ...
UNESCO estimates that our planet’s oceans and lakes are home to more than three million shipwrecks. Of these three million, the locations of only 10% are currently known. Apart from the historical and archaeological interest in finding wrecks, there are other reasons why we need to know their precise locations. While a shipwreck can provide an excellent habitat for marine life, acting as an artificial reef, shipwrecks are also potential sources of pollution, leaking fuel and corroding heavy metals. When a vessel runs aground on an iron-free environment, changes in the chemistry of the surrounding environment can occur, creating a discoloration called black reef. In this work, we examine the use of supervised deep learning methods for the detection of shipwrecks on coral reefs through the presence of this discoloration using satellite images. One of the main challenges is the limited number of known locations of black reefs, and therefore, the limited training dataset. Our results show that even with relatively limited data, the simple eight-layer, fully convolutional network has been trained efficiently using minimal computational resources and has identified and classified all investigated black reefs and consequently the presence of shipwrecks. Furthermore, it has proven to be a useful tool for monitoring the extent of discoloration and consequently the ecological impact on the reef by using time series imagery.
... Although wrecks can last for a very long time (>100 year, Arena et al., 2007;Fowler and Booth 2012) the inevitable deterioration of metal surfaces results in rust and flaking, which ultimately inhibits recruitment and survival of sessile organisms (Fitzhardinge and Bailey-Brock 1989). Interestingly, multiple studies from the Indo-Pacific reported changes in the benthic community of the natural reefs surrounding a metal wreck (Work et al., 2008;Kelly et al., 2012;Carter et al., 2019;van der Schyff et al., 2020). This has been suggested to be the result of iron leakage from the degrading wreck (Work et al., 2008;Kelly et al., 2012). ...
... This has been suggested to be the result of iron leakage from the degrading wreck (Work et al., 2008;Kelly et al., 2012). The elevated iron levels in algae surrounding the wrecks (Kelly et al., 2012;van der Schyff et al., 2020) suggest that wrecks can locally alleviate iron limitation occurring on many Indo-Pacific reefs. Higher iron availability can explain observed increases of cyanobacteria (Kelly et al., 2012), turf algae (Kelly et al., 2012), corallimorphs (Work et al., 2008;Kelly et al., 2012) and macroalgae (van der Schyff et al., 2020), all of which can decrease coral cover (Work et al., 2008;Kelly et al., 2012;van der Schyff et al., 2020). ...
... The elevated iron levels in algae surrounding the wrecks (Kelly et al., 2012;van der Schyff et al., 2020) suggest that wrecks can locally alleviate iron limitation occurring on many Indo-Pacific reefs. Higher iron availability can explain observed increases of cyanobacteria (Kelly et al., 2012), turf algae (Kelly et al., 2012), corallimorphs (Work et al., 2008;Kelly et al., 2012) and macroalgae (van der Schyff et al., 2020), all of which can decrease coral cover (Work et al., 2008;Kelly et al., 2012;van der Schyff et al., 2020). Metal wrecks may thus cause iron-induced phase shifts in adjacent natural reefs, turning them into so called "black reefs" (Kelly et al., 2012). ...
p>Caribbean coral reefs are in decline and the deployment of artificial reefs, structures on the sea bottom that mimic one or more characteristics of a natural reef, is increasingly often considered to sustain ecosystem services. Independent of their specific purposes, it is essential that artificial reefs do not negatively affect the already stressed surrounding habitat. To evaluate the ecological effects of artificial reefs in the Caribbean, an analysis was performed on 212 artificial reefs that were deployed in the Greater Caribbean between 1960 and 2018, based on cases documented in grey (n = 158) and scientific (n = 54) literature. Depending on the availability of data, reef type and purpose were linked to ecological effects and fisheries management practices around the artificial reefs. The three most common purposes to deploy artificial reefs were to create new dive sites (41%), to perform research (22%) and to support ecosystem restoration (18%), mainly by stimulating diversity. Ship wrecks (44%), reef balls</p
... In 1970, triphenyltin and tributyltin were used to prepare highly effective antifouling paints for the shipping industry [76]. Van der Schyff et al. reported that 1% of marine MP contamination resulting from ship paint occurs from weathering, 1.8% result from spillage during painting, 3.2% from maintenance, and 6% from coating that is naturally lost during a ship's lifetime [77]. Similarly, high usage of paints containing polymers, such as PVC, polydiallyl phthalate, polyester, and polymethyl methacrylate during road construction, has led to road dust in several Japanese cities [78]. ...
... Metals have natural sources whereas bisphenols and benzophenone UV filters do not and indicate pollution linked with human activities. Additional marine pollution sources that may influence metallic element concentrations in mussels can include activities linked to ship-to-ship fuel bunkering, which has been operational in Algoa Bay since 2016, oil spills (Adeniji et al., 2017;Pichegru et al., 2022), and shipwrecks around Algoa Bay (Rogers, 2018;Van der Schyff et al., 2020). Biological and other environmental factors that may modulate concentrations in biota include for example, the species, their reproductive stage, season, and rainfall (Rainbow, 1993;Wepener and Fig. 5. Graphical comparison of estimated daily intake (EDI) values measured in mussels collected at the different sites around Algoa Bay, South Africa. ...
Elevated metal concentrations can become harmful to marine organisms and to humans that consume them. Metal concentrations at multiple sites around Algoa Bay, South Africa, were last investigated in the 1980s. We collected wild brown mussels (Perna perna) from seven sites around Algoa Bay, and quantified metallic elements using ICPMS. Metallic element concentrations differed significantly among the sampling sites and correlated with pollution sources at specific sites. The concentration of Pb in mussels at one site slightly exceeded South African limits. Based on the South African estimated daily intake, the target hazard quotient, and South African metal limits, mussels from Algoa Bay are safe for human consumption, except possibly from one site. However, combined with data on bisphenols and benzophenone UV filters in P. perna from the same sites, we suggest a possible health concern to consumers.
... Paint particles are also generated while ships are at sea. For example, groundings and collisions are known to generate large quantities of antifouling paint around the location of impaction (Negri et al., 2002;Jones, 2007;van der Schyff et al., 2020), while vessels navigating through ice or fishing activities generating friction between painted surfaces and rope may also act as more diffuse sources (Negri and Marshall, 2009;Song et al., 2014). It is also likely that paint particles are generated more passively with the general wear and tear (erosion) of hull, waterline, topside and deck coatings (Dibke et al., 2021). ...
Because paint particles consist of a resin (polymer) combined with one or more additives, they bear compositional similarities with microplastics. Despite these shared characteristics, however, paint particles are often undetected, deliberately overlooked or evade classification in the pool of micro-debris (all synthetic debris of < 5 mm in size), and in particular in the marine setting where an extensive body of microplastic literature exists. Accordingly, the present paper provides a critical insight into the physico-chemical properties, sources, distributions, behaviour and toxicity of paint particles in the marine environment.
Paint particles contain a greater proportion of additives than plastics and, consequently, are more brittle, angular, opaque, dense, heterogeneous and layered than microplastics of equivalent dimensions. Land-based sources of paint particles, including deteriorating or disturbed coatings on roads and building, are transported to the ocean with other microplastics via urban runoff, water treatment facilities and the atmosphere. However, inputs of paint particles are enhanced significantly and more directly by the disturbance, erosion and weathering of coatings on coastal structures, boats and ships. Estimates of paint particle emissions to the marine environment vary widely, with calculated contributions to the total synthetic micro-debris input as high as 35%. Upper estimates are consistent with available (albeit limited) quantitative information on the relative abundance of paint particles amongst synthetic material captured by sea surface trawls and ingested by marine animals. Of greatest environmental concern is the high chemical toxicity of paint particles compared with similarly-sized microplastics and other synthetic debris. This results from the contemporary and historical use of high concentrations of hazardous inorganic additives in marine antifouling and land-based paints, and the relatively ready mobilisation of harmful ions, like Cu⁺/Cu²⁺, TBT⁺, Pb²⁺ an CrO4²⁻, from the matrix. Recommendations arising from this review include greater use of particulate capturing devices, waste collection systems and recycling facilities during paint disturbance, raising awareness of the potential impacts of discarded paint amongst users, and alerting the microplastic community to the significance of paint particles and developing means by which they are isolated from marine samples.
... OECD (2009) suggested that about 6% of a ship's coating would be spilled directly into the sea during its lifetime, with about 1.8% being spilled during painting, 1% by weathering during use and 3.2% by maintenance. Shipwrecks are another source of paint MPs (van der Schyff et al., 2020) and these may contain currently banned toxic (antifouling or anticorrosion) materials. ...
Paint particles are part of the increasingly important microplastics (MPs) pollution of our oceans. They contain polyurethanes, polyesters, polyacrylates, polystyrenes, alkyls and epoxies. In spite of their prevalence, paint fragments are often excluded from MP audits. This review, citing 127 references, discusses detection, characteristics , sources and ecological effects of paint fragments in our oceans, as well as the abundance of paint fragments in MP samples around the world and their colonization by marine microorganisms, which differs from that of non-paint MPs. Paint MPs arise from shipping and boating activities, road markings and external surfaces of buildings. Many paint fragments come from antifouling paints used on commercial vessels and leisure boats; these may be regarded as particular pollutants, not only containing but also leaching heavy metals and biocides. Some effects of antifouling paint particles on aquatic biota are caused by these toxins. Paint particles are an understudied portion of marine MP pollution.
... Some of the debris was clothing and food packaging, which are known to include PFAS as a production component (Buck et al., 2011). In addition to long-range transported debris items, shipwrecks on the atoll could be a possible contamination source (van der Schyff et al., 2020b). According to the International Convention for the Safety of Life at Sea (SOLAS), all commercial vessels are required to carry foam firefighting equipment at all times in the boiler rooms (SOLAS, 2018). ...
Per- and polyfluoroalkyl substances (PFAS) are anthropogenic fluorinated compounds of concern for human and environmental health. There is no data on PFAS concentrations in marine bird eggs from the Western Indian Ocean. We analysed eight PFAS in eggs of fairy terns (Gygis alba), sooty terns (Onychoprion fuscatus), and common noddies (Anous stolidus) from St. Brandon's Atoll. Fairy tern eggs contained the highest concentrations, followed by sooty terns and common noddies. Perfluoroundecanoic acid (PFUdA) had the highest mean concentration (2.3 ng/g wm), followed by perfluorooctane sulfonic acid (PFOS) (2.0 ng/g wm), and perfluorononanoic acid (PFNA) (0.93 ng/g wm) in fairy tern eggs. Concentrations of all PFAS were lower than values found in literature. PFOS and PFOA concentrations were three orders of magnitude lower than toxicity reference values and levels of lowest-observed-adverse-effect-level concentrations. Eggs from St. Brandon's would be useful to monitor background changes on a regional and perhaps global scale.
Silica sol can activate the surface of hollow ceramic microspheres and improve the properties of composite materials by improving the interface between the microspheres and the epoxy resin. The group changes on the surface of microspheres were measured using infrared spectroscopy. The microspheres were observed with a scanning electron microscope. The density, water absorption, and mechanical properties of the materials were tested using scales and mechanical testing machines. The results showed that SiO 2 and silane molecules were introduced on the surface of the microspheres after treatments. As the silica sol content increased, the slurry viscosity increased by 34.5%, the composite density increased by 5.8%, and the water absorption decreased by 35.8%. When the silica sol content was 25%, the flexural strength and compressive strength of the composites were 73.49 and 116.27 MPa, respectively, which were 37.8% and 23.6% higher than those of the untreated composites, and the mechanical properties became clearly improved. High mechanical properties enable the materials to be used in deeper ocean areas.
Highlights
Nanoparticles are introduced onto the surface of hollow microspheres.
The activated microspheres can bind better to the silane coupling agent.
Silane coupling agent assisted by silica sol improved interfacial bonding.
Surface activation of microspheres improves the properties of composites.
There is continued growth in paints and synthetic textile materials production and consumption due to expanded use of paints in different applications, population growth and fast fashion trends. Paints and synthetic textile materials are some of the major sources of microplastics. The major sources of microplastics originating from paints are marine paints, road markings, architectural paints, and spray painting. Major contributing factors in the release of microplastics from paints to the environment are paint production processes, weathering and abrasion, paint spilling, residual paints on paint application tools and storage containers, paint end of life (EoL) disposal, and paint applicator’s expertise. In the context of synthetic textile materials, major emissions of the microplastics occur during the production processes of the synthetic textile materials, during use and laundering, washing conditions and drying. Studying the role and influence of paints and synthetic textile materials in the generation of microplastics is critical. It helps in coming up with mitigatory measures to reduce the generation of microplastics from paints and synthetic textile materials and hence promotion of sustainability. Devising a holistic approach to research and development of green chemistry and green manufacturing processes in the production of paints and synthetic textile materials is one of the mitigatory measures. Also, developing policies and legislation on wastewater treatment systems for all responsible stakeholders and introducing legislation on do-it-yourself (DIY) painting activities could help in reducing the generation of microplastics from paints and synthetic textile materials.
Pollution by polycyclic aromatic hydrocarbons, lead, mercury, arsenic, cadmium, and chromium is impairing marine ecosystems. Here, we review the effect of these contaminants on coral reefs and mangrove ecosystems, with focus on reef fishes, algae, corals, and oil spills. We also discuss the effects of natural hydrocarbons. Some polycyclic aromatic hydrocarbons display carcinogenic and mutagenic properties. Heavy metals are highly toxic to most marine living organisms, causing reproductive failure, deoxyribonucleic acid damage, and neurological problems. Heavy metals accumulate through the food chain, ending up in humans who eat seafood. Mangroves and coral reefs can be severely impacted with diminished water quality, reduced biodiversity, compromised fish habitats, decreased fish catches, and damaged seagrass beds, ultimately affecting other coastal habitats.
An estimated three million shipwrecks exist worldwide and are recognized as cultural resources and foci of archaeological investigations. Shipwrecks also support ecological resources by providing underwater habitats that can be colonized by diverse organisms ranging from microbes to megafauna. In the present article, we review the emerging ecological subdiscipline of shipwreck ecology, which aims to understand ecological functions and processes that occur on shipwrecks. We synthesize how shipwrecks create habitat for biota across multiple trophic levels and then describe how fundamental ecological functions and processes, including succession, zonation, connectivity, energy flow, disturbance, and habitat degradation, manifest on shipwrecks. We highlight future directions in shipwreck ecology that are ripe for exploration, placing a particular emphasis on how shipwrecks may serve as experimental networks to address long-standing ecological questions.
Underwater cultural heritage sites (UCH), such as shipwrecks and sunken aircrafts, can provide physical structures to support coral recruitment and habitats for marine organisms. Conversely, these archaeological artifacts can also be detrimental to live coral and release pollutants into the environment. The military history of Guam has resulted in a high abundance of UCH sites on shallow coral reef habitats, and little is known about how these artifacts may affect the ecology of these natural systems. In this study, we used photogrammetry techniques to survey coral assemblages on both natural and artificial reef substrata. We statistically examined patterns in coral cover, diversity, richness, and 3D habitat complexity. Our results found significant differences in live coral cover and assemblage structure between natural and artificial reef substrata. The results from univariate modeling and multivariate analyses indicate that coral assemblage structure plays an important role in supporting 3D habitat complexity, and the archaeological artifacts themselves can be a significant source of habitat structure. There is still a lack of clarity as to the overall implications of archaeological artifacts on underwater habitats, and the approach described here can be applied elsewhere to better understand the ecological impacts of UCH sites on coral reefs.
Little is known about early coral settlement on shipwrecks with regard to their species and size compositions. Hurricanes in the Caribbean have a long history of sinking ships but a link with new coral settlement is understudied. In 2017, Hurricane Irma caused the sinking of over 300 vessels in the coastal waters of Saint Martin, eastern Caribbean. In 2021, coral settlement was studied on one of them, which included two native, one non-native, and two cryptogenic species. The corals were smaller than 8 cm in diameter. The invasive Tubastraea coccinea was the most abundant scleractinian and was predominantly represented by juveniles. A cryptogenic species, Stragulum bicolor, new for the Caribbean, was the most common octocoral. Because they can be harmful to the environment, shipwrecks should be monitored frequently for the occurrence of non-native species, especially when they are only a few years old.
In order to enhance the performance of lightweight and high-strength composites in the deep-sea environment, epoxy resin (EP) was used as the matrix and hollow glass beads (HGB) was used as the reinforcing phase to reduce the density of composite. Graphene oxide (GO) was employed to modify HGB for improving the interfacial adhesion between HGB and EP. In this work, the effect of GO on the mechanical properties of HGB/EP composites in simulated deep-sea environment was investigated. The results show that compared with HGB/EP composite, the compressive and impact strength of [email protected]/EP composite after high-pressure seawater treatment is increased by 26.6% and 29.7%, respectively. And the compressive and impact strength after low-temperature seawater treatment is increased by 23.1% and 51.3%, respectively. The improvement of mechanical properties of HGB/EP composites makes its application in deep-sea environment more promising.
Despite the debate that continues to go on, at present, corals do not qualify to be a part of the conventional blue carbon ecosystems. Nonetheless, these marine ecosystems are crucial as they provide a plethora of ecosystem services not only to humans but also to several blue carbon ecosystems. These ecosystems provide shelter to the adjacent seagrass and mangroves. Corals act as wave breakers in many parts of the world and thereby furnishes a calm and stable environment to blue carbon ecosystems lying adjacent to each other. The present chapter collated the knowledge acquired so far on the coral species count and areal cover in the different countries bordering the Indian Ocean. This chapter also discussed the various threats that make corals vulnerable on these coastlines. We observed a spatial disparity in the degree of attention paid to the corals bordering the Indian Ocean. The coral triangle region received much higher attention than that observed in the western Indian Ocean. Several countries are yet to configure the principal threats to the corals lying on their coastline. Thus, this chapter apart from detailing the present state-of-the-art identifies the arenas that require scientific attention in the Indian Ocean periphery.
Reducing the global reliance on fossil fuels is essential to ensure the long-term survival of coral reefs, but until this happens, alternative tools are required to safeguard their future. One emerging tool is to locate areas where corals are surviving well despite the changing climate. Such locations include refuges, refugia, hotspots of resilience, bright spots, contemporary near-pristine reefs, and hope spots that are collectively named reef ‘safe havens' in this mini-review. Safe havens have intrinsic value for reefs through services such as environmental buffering, maintaining near-pristine reef conditions, or housing corals naturally adapted to future environmental conditions. Spatial and temporal variance in physicochemical conditions and exposure to stress however preclude certainty over the ubiquitous long-term capacity of reef safe havens to maintain protective service provision. To effectively integrate reef safe havens into proactive reef management and contingency planning for climate change scenarios, thus requires an understanding of their differences, potential values, and predispositions to stress. To this purpose, I provide a high-level review on the defining characteristics of different coral reef safe havens, how they are being utilised in proactive reef management and what risk and susceptibilities they inherently have. The mini-review concludes with an outline of the potential for reef safe haven habitats to support contingency planning of coral reefs under an uncertain future from intensifying climate change.
This chapter tabulates the analytical techniques used for selected studies and briefs about the species of scleractinian coral used; the component of the coral analysed; the appropriate analytical methodology adopted; the different metals analysed and the specific instrument used for analysis. Different concentrations of heavy metals are obtained for different studies due to different components being analysed and the concentrations measured as either wet weight or dry weight. Certain studies focus on the analysis of the total metal concentrations for the skeleton, tissue and zooxanthallae whilst some studies have analysed specific components of the coral species. Hence, this chapter gives a general feedback on the analytical techniques adopted for the variety of scleractinian coral species under study. This sort of feedback can be used for general comparison between studies and scleractinian species and the different analytical techniques.
We report the concentrations of persistent organic pollutants (POPs) in seabird eggs from St. Brandon's Atoll, a tropical island system in the western Indian Ocean. Ten eggs each of sooty terns (Onychoprion fuscatus), fairy terns (Gygis alba), and common noddies (Anous stolidus) were collected from the atoll. For a terrestrial reference, we analysed three feral chicken (Gallus gallus domesticus) eggs from the same location. Sooty tern eggs contained the highest mean concentrations of three chemical classes: ƩCHL3 (0.21 ng/g wm; wet mass), ƩPCB10 (1.5 ng/g wm), and ƩPBDE6 (1.1 ng/g wm). Fairy tern eggs contained the highest mean concentrations of HCB (0.68 ng/g wm) and ƩCHB5 (0.83 ng/g wm). The chicken eggs contained the highest mean concentrations of ƩDDT3 (2.6 ng/g wm), while common noddy eggs contained the highest mean concentrations of ƩHCH2 (0.5 ng/g wm). We surmise that the differences in chemical composition between species reflect different pollutant compositions in prey from the bird’s different foraging ranges. The sooty terns foraging offshore contained higher POPs concentrations than the nearshore-foraging common noddies. Fairy tern eggs contained intermediate concentrations, commensurate with their intermediate foraging. Inter-island differences in contaminant concentrations were seen between eggs of the common noddies from St. Brandon's Atoll and Rodrigues Island, 520 km to the south-east. Concentrations of contaminants found in this study were lower than values quantified by other studies, making St. Brandon's Atoll an ideal reference site to monitor background concentrations of POPs in the tropical Indian Ocean.
Persistent halogenated compounds (PHC) are of concern for human and environmental health. Persistent Organic Pollutants (POPs) are regulated by international treaties, but alternative compounds such as novel brominated flame retardants (NBFRs) and Dechlorane Plus (DP) are not—yet they are increasingly used. There are no data on PHCs in coral reef biota from tropical islands in the western Indian Ocean (WIO). For this assessment, three hard coral genera, two soft coral genera, and ember parrotfish (Scarus rubroviolaceus) were collected from the remote Rodrigues, Agalega, and St. Brandon’s Atoll (Republic of Mauritius) in the Mascarene Basin of the WIO. Five compounds — Pentabromotoluene (PBT), γ-HCH, p,p’-DDE, HCB, and BDE-47— were quantifiable in all samples. Hard coral consistently contained the lowest concentrations of PHCs, except for NBFRs. The presence of BDE-47 suggests long-range aerial transport. We quantified DP, currently a candidate POP, in coral reef biota. PBT was measured in all samples also suggests long-range transport. Because the hard coral, soft coral, and fish had differing concentrations and patterns of PHCs, future surveys should stratify sampling accordingly. Agalega and St. Brandon’s Atoll can be considered as locations to monitor changes in background concentrations of pollutants due to their remoteness.
In order to assess pollutants and impact of environmental changes along the Egyptian Red Sea coast, seven recent and Pleistocene coral species have been analyzed for Zn, Pb, Mn, Fe, Cr, Co, Ni, and Cu. Results show that the concentration of trace elements in recent coral skeletons is higher than those of Pleistocene counterpart except for Mn and Ni. In comparison with recent worldwide reefs, the present values are less than those of Central America coast (iron), Gulf of Aqaba, Jordan (lead, copper), Gulf of Mannar, India (chromium, zinc, manganese), Costa Rica, Panama (chromium, nickel), North-west coast of Venezuela and Saudi Arabia (copper). The present values are higher than those of Gulf of Aqaba, Jordan (iron, zinc, manganese), Gulf of Mannar, India (lead, cobalt, nickel), North-west coast of Venezuela (lead, zinc, chromium, manganese), Australia (copper, nickel, zinc, manganese). The highest values were recorded in Stylophora
pistillata (iron, lead and copper), Acropora
cytherea (cobalt), Pocillopora
verrucosa (zinc) and the lowest concentrations were recorded in Goniastrea
pectinata (iron, chromium, copper and nickel), Favites
pentagona (lead, zinc and manganese), and Porites
lutea (cobalt). The differences in metals content among the studied species are attributed to differences in microstructure and microarchitecture.
Anthropogenic global change and local stressors are impacting coral growth and survival worldwide, altering the structure and function of coral reef ecosystems. Here, we show that skeletal extension rates of nearshore colonies of two abundant and widespread Caribbean corals (Siderastrea siderea, Pseudodiploria strigosa) declined across the Belize Mesoamerican Barrier Reef System (MBRS) over the past century, while offshore coral conspecifics exhibited relatively stable extension rates over the same temporal interval. This decline has caused nearshore coral extension rates to converge with those of their historically slower growing offshore coral counterparts. For both species, individual mass coral bleaching events were correlated with low rates of skeletal extension within specific reef environments, but no single bleaching event was correlated with low skeletal extension rates across all reef environments. We postulate that the decline in skeletal extension rates for nearshore corals is driven primarily by the combined effects of long-term ocean warming and increasing exposure to higher levels of land-based anthropogenic stressors, with acute thermally induced bleaching events playing a lesser role. If these declining trends in skeletal growth of nearshore S. siderea and P. strigosa continue into the future, the structure and function of these critical nearshore MBRS coral reef systems is likely to be severely impaired.
In 2013, the remote Tubbataha Reef UNESCO World Heritage Site, in the western Philippines, experienced two ship groundings within four months: the USS Guardian (USSG), a US military vessel, and the Min Ping Yu (MPY), an illegal Chinese fishing vessel. Here, we present the results of coral disease assessments completed two years post-grounding and recovery patterns monitored annually within these grounding sites. Site assessments were undertaken in three distinct zones: ‘ground zero’, where reef was scoured to its limestone base by direct ship impact; the ‘impact border’, containing surviving upright but damaged, abraded and fragmented colonies injured during ship movement; and undamaged ‘control’ sites, remote from the ship groundings but located on the same atoll. Coral diseases were dominated by white syndromes, and prevalence was an order of magnitude higher within the impact border zones than within the other zones two years after the events. Hard coral cover has steadily increased at a mean rate of 3% per year within the scoured USSG site at a rate comparable to control sites. In contrast, recovery has been negligible within the rubble-dominated MPY site, suggesting that substrate quality strongly influenced recovery processes such as recruitment, as larvae do not survive well on unstable substrates. Long-term recovery trajectories from these two grounding events appeared strongly influenced by movement of the ship during and after each event, and site-specific wave-influenced persistence of rubble and debris. High prevalence of coral disease among damaged but surviving colonies two years post-grounding suggested long-term impacts which may be slowing recovery and creating localized pockets of higher persistent disease prevalence than that of the surrounding population.
Metal pollution is nowadays a serious threat worldwide for ecosystem and human health. Despite that, there is still a paucity of data on metal impact on coral reef ecosystems. Herein, the levels of eleven metals (Mn, Zn, Cu, Cr, Co, Ni, V, As, Cd, Hg, Pb) were assessed in surface sediments, seawater samples, Scleractinian corals (tissue and skeleton) and their algal symbionts collected from Kharg and Lark coral reefs in the Persian Gulf, Iran. At Kharg, surface sediments and seawater showed higher concentrations of metals than Lark, attributable to the higher metal loads and petrochemical activities in the area. Sediment quality guidelines indicated Hg as a serious threat to biota both at Kharg and Lark. Accordingly, metals bioaccumulation and bioconcentration was higher in corals from Kharg relatively to Lark Island. Interestingly, as supported by values of BCFs and BSAFs, metal accumulation was higher in coral tissues in respect to skeletons, and in zooxanthellae relatively to coral tissues at both coral reefs. Differential metal bioaccumulation was found among Scleractinian species, indicating that corals have distinct selectivity for assimilating metals from ambient sediments and seawater. Overall, metal accumulation in corals and zooxanthellae is an appropriate tool for environmental monitoring studies in coral reefs. Noteworthy , the use of Porites lutea, among Scleractinian corals, seems to be as a good bioindicator in monitoring studies of metal pollution.
Global warming is rapidly emerging as a universal threat to ecological integrity and function, highlighting the urgent need for a better understanding of the impact of heat exposure on the resilience of ecosystems and the people who depend on them 1 . Here we show that in the aftermath of the record-breaking marine heatwave on the Great Barrier Reef in 2016 2 , corals began to die immediately on reefs where the accumulated heat exposure exceeded a critical threshold of degree heating weeks, which was 3-4 °C-weeks. After eight months, an exposure of 6 °C-weeks or more drove an unprecedented, regional-scale shift in the composition of coral assemblages, reflecting markedly divergent responses to heat stress by different taxa. Fast-growing staghorn and tabular corals suffered a catastrophic die-off, transforming the three-dimensionality and ecological functioning of 29% of the 3,863 reefs comprising the world's largest coral reef system. Our study bridges the gap between the theory and practice of assessing the risk of ecosystem collapse, under the emerging framework for the International Union for Conservation of Nature (IUCN) Red List of Ecosystems 3 , by rigorously defining both the initial and collapsed states, identifying the major driver of change, and establishing quantitative collapse thresholds. The increasing prevalence of post-bleaching mass mortality of corals represents a radical shift in the disturbance regimes of tropical reefs, both adding to and far exceeding the influence of recurrent cyclones and other local pulse events, presenting a fundamental challenge to the long-term future of these iconic ecosystems.
Dynamics in reef cover, mortality and recruitment success of a high-latitude coral community in South Africa were studied over 20 yr with the aim to detect the effects of climate change. Coral communities at this locality are the southernmost on the African continent, non-accretive, attain high biodiversity and are dominated by soft corals. Long-term monitoring within fixed transects on representative reef was initiated in 1993 and has entailed annual photo-quadrat surveys and hourly temperature logging. Although sea temperatures rose by 0.15 °C p.a. at the site up to 2000, they have subsequently been decreasing, and the overall trend based on monthly means has been a significant decrease of 0.03 °C p.a. Despite this, minor bleaching was encountered in the region during the 1998 El Niño–Southern Oscillation event, again in the summer of 2000/2001 and in 2005. A significant decreasing trend of 0.95% p.a. in soft coral cover has been evident throughout the monitoring period, attributable to significant decreases in Sinularia and Lobophytum spp. cover. In contrast, hard coral cover gradually and significantly increased up to 2005, this being largely attributable to increases in cover by Acropora spp. Recruitment success and mortality of both soft and hard corals has displayed high inter-annual variability with increasing but non-significant trends in the last 5 yr. The reduction in soft coral cover has been more consistent and greater than that of hard corals, but it is difficult at this stage to attribute this to changes in water quality, acidification-linked accretion or temperature.
The ISME Journal: Multidisciplinary Journal of Microbial Ecology is the official Journal of the International Society for Microbial Ecology, publishing high-quality, original research papers, short communications, commentary articles and reviews in the rapidly expanding and diverse discipline of microbial ecology.
Inshore coral reefs are experiencing the combined pressures of excess nutrient availability associated with coastal activities and warming seawater temperatures. Both pressures are known to have detrimental effects on the early life history stages of hard corals, but studies of their combined effects on early demographic stages are lacking. We conducted a series of experiments to test the combined effects of nutrient enrichment (three levels) and elevated seawater temperature (up to five levels) on early life history stages of the inshore coral Acropora tenuis, a common species in the Indo-Pacific and Red Sea. Gamete fertilization , larval survivorship and larval settlement were all significantly reduced as temperature increased, but only fertilization was further affected by simultaneous nutrient enrichment. Combined high temperatures and nutrient enrichment affected fertilization in an additive manner, whereas embryo abnormalities increased synergistically. Higher than normal temperatures (32°C) increased coral juvenile growth rates 1.6-fold, but mortality also increased by 50%. The co-occurrence of nutrient enrichment with high temperatures reduced juvenile mortality to 36%, ameliorating temperature stress (antagonistic interaction). Overall, the types of effect (additive vs synergistic or antagonistic) and their magnitude varied among life stages. Gamete and embryo stages were more affected by temperature stress and, in some cases, also by nutrient enrichment than juveniles. The data suggest that coastal runoff events might exacerbate the impacts of warming temperatures on fertilization if these events co-occur during corals spawning. The cumulative impacts of simultaneous exposure to nutrient enrichment and elevated temperatures over all early life history stages increases the likelihood for failure of larval supply and recruitment for this coral species. Our results suggest that improving the water quality of river discharges into coastal areas might help to enhance the thermal tolerances of early life history stages in this common coral species.
Acute and chronic toxicity tests were conducted with sea cucumber (
Apostichopus japonicus
) exposed to heavy metals. Acute toxicity values (96 h LC50) were 2.697, 0.133, and 1.574 mg L
−1
for Zn, Cu, and Cd, respectively, and were ranked in order of toxicity: Cu > Cd > Zn. Under chronic metal exposure the specific growth rates of sea cucumbers decreased with the increase of metal concentration for all the three metals. After acute metal exposure, the oxygen consumption rate (OCR) decreased. The OCRs in all groups were significantly different than control (
P
<
0.05
) except in the group treated with 1.00 mg L
−1
Zn (
P
<
0.05
), where the increase of OCR was observed. The OCRs in groups chronically exposed to metals were significantly lower than that in the control group (
P
<
0.05
). The activity of both pyruvate kinase (PK) and hexokinase (HK) in sea cucumbers followed: respiratory tree > muscle > intestine in natural sea water. After chronic Zn, Cu, and Cd exposure, the change pattern of HK and PK in respiratory tree, muscle, and intestine varied slightly. However, the activity of the enzyme showed a general trend of increase and then decrease and the higher the exposure concentration was, the earlier the highest point of enzyme activity was obtained.
Urban estuaries are susceptible to metal and organic pollution, yet most remain understudied in South Africa with respect to the presence, concentrations and distribution of contaminants. Metal and organic chemical concentrations were assessed in sediment and organisms from different trophic levels in the lower reaches of the Swartkops Estuary. Species sampled included Upogebia africana (Malacostraca: Upogebiidae), Gilchristella aestuaria (Clupeidae), Psammogobius knysnaensis (Gobiidae), Mugil cephalus (Mugilidae), Lichia amia (Carangidae), Argyrosomus japonicus (Sciaenidae), Pomadasys commersonnii (Haemulidae) and Larus dominicanus (Avis: Laridae). This study is one of the most comprehensive studies to date assessing pollution levels in a food web in estuaries in South Africa. Due to biomagnification, higher concentrations of Arsenic, Lead, Mercury and Cadmium were found in the juveniles stages of popular angling fishes. High concentrations of Cadmium and Arsenic were recorded in the liver of L. amia, A. japonicus and P. commersonnii which exceed international quality food guidelines. Eggs from the gull, L. dominicanus, showed detectable concentrations of PCBs.
We have examined trends in marine pollution research in South Africa over the past 40 years, based on analyses of the primary literature. There has been a striking decline in the quantity of research outputs in the past two decades. New initiatives are needed to rebuild a research culture in this discipline.
A multibeam bathymetric survey of six mature-phase and 17 youthful-phase submarine canyons, many of which were previously unknown, on the northern KwaZulu-Natal continental shelf was undertaken in order to define the physical, structural habitat of coelacanths and to guide surveys by manned submersibles within the canyons. Five survey blocks were systematically surveyed to develop a series of colour-draped bathymetric maps and three-dimensional models of the canyons. The bathymetric data and maps were developed further to provide the basal layer of a marine Geographical Information System upon which to build all geo-referenced physical and biological data of the African Coelacanth Ecosystem Programme.
The effects of ocean acidification alone or in combination with warming on coral metabolism have been extensively investigated, whereas none of these studies consider that most coral reefs near shore are already impacted by other natural anthropogenic inputs such as metal pollution. It is likely that projected ocean acidification levels will aggravate coral reef health. We first investigated how ocean acidification interacts with one near shore locally abundant metal on the physiology of two major reef-building corals: Stylophora pistillata and Acropora muricata. Two pH levels (pH T 8.02; pCO 2 366 μatm and pH T 7.75; pCO 2 1140 μatm) and two cobalt concentrations (natural, 0.03 μg L-1 and polluted, 0.2 μg L-1)
Abstract
Threat of the coral reef ecosystem is still occur due to anthropogenic and natural causes. It is less known that the coral reef degradations had been caused by ship grounding due to navigational error or bad weather. Ship grounding can impact to the coral reef and shallow seabed ecosystems particularly change the bottom structure of habitat. Measuring the habitat damage can be investigated by diving methods namely Rapid Reef Assessment, Point Intercept Transect (PIT) and manta tow. Furthermore to estimate the type and wide of reef degraded can be investigated by on boat namely Run Video Camera, Deep Scan Sonar and submesible photographic Quadrat Transect. Selection of manual methods depending on oceanographic condisitions, depth of reef, ability of diver and equipment available. Ship grounding impact can be divided into three site categories are inbounding track, parking lot and the hull resting area. Many cases of it had impact in around inbounding track was 100% dead coral dominated by boulder fragments, in the parking lot was less than 70% of dead and injured coral and in the hull resting area were 95% of dead and injured head corals and 5% of sand coverage. The grounding ships was affecting to the on site coral reef condition and diversity. They always threatened by these accidents around the ship lines anytime. So we have to care and take a responsibility to rehabilitate the degradation of the coral reefs.
Keywords : Coral reef, degradation, ship grounding
Mining and other economic activities have led to the pollution of the Vaal River with metals of mainly industrial origin, but the consequences of this for animal and human health are unknown. Based on chemical analysis and histological examination, we report the contamination with 15 metals of river sediments and organs of sharptooth catfish Clarias gariepinus from four widely separated sites along this important South African waterway, sampled in spring 2010. Although some metals proved to be highly enriched, the fish organs showed no histological alterations that could be related to metal exposure. However, when the levels of metals that accumulated in C. gariepinus were used in a theoretical scenario, these concentrations signalled a potential threat to human health.
The coral surface mucus layer provides a vital interface between the coral epithelium and the seawater environment and mucus acts in defence against a wide range of environmental stresses, in ciliary-mucus feeding and in sediment cleansing, amongst other roles. However, we know surprisingly little about the in situ physical and chemical properties of the layer, or its dynamics of formation. We review the nature of coral mucus and its derivation and outline the wide array of roles that are proposed for mucus secretion in corals. Finally, we review models of the surface mucus layer formation. We argue that at any one time, different types of mucus secretions may be produced at different sites within the coral colony and that mucus layers secreted by the coral may not be single homogeneous layers but consist of separate layers with different properties. This requires a much more dynamic view of mucus than has been considered before and has important implications, not least for bacterial colonisation. Understanding the formation and dynamics of the surface mucus layer under different environmental conditions is critical to understanding a wide range of associated ecological processes.
Several studies have shown that the growth of macroalgae is reduced when in contact with corals, but very few have addressed the mechanisms involved. This study provides for the first time an explicative mechanism for the inhibition of algal growth by scleractinian corals. In experimental field contacts between 8 species of scleractinian corals and the green alga Halimeda opuntia, corals extruded their mesenterial filaments (MFs) onto the plant. In some coral species, this extrusion was followed by persistent discolouration of the contacting algal segments. Microscopic examination of these segments revealed migration of chloroplasts away from the surface of segments, as well as the presence of nematocysts from the MFs fired into the algal epidermis. There was a significant relationship between the extent of algal discolouration and both the occurrence and length of the MFs, potentially explaining differences among coral species in their ability to damage algal segments. MF extrusion also occurred in experimental contacts with 2 other species of macroalgae (Lobophora variegata and Dictyota sp.). The use of extruded MFs by scleractinian corals against macroalgae is similar to their aggressive behaviour against other scleractinian coral species. However, the ranking of competitive ability against H. opuntia (measured by the extent of algal discolouration) differed from that established in interspecific aggressions among corals. The great abundance and wide distribution of the species of corals and macroalgae used in this study, together with observations of MFs in natural interactions, suggest that the use of MFs is a common and widespread mechanism of interaction between corals and macroalgae. We conclude that coral-algal competition involves complex mechanisms and is therefore likely to represent a complex hierarchical structure, in which macroalgae are not always able to overgrow and kill corals.
The reefs of the Mascarenes differ in structure and stage of development. Mauritius is the oldest island, bound by a discontinuous fringing reef and small barrier reef, with large lagoon patch reefs. Rodrigues has nearly continuous fringing reefs bounding an extensive lagoon with deep channels and few patch reefs. Réunion, the youngest island, has short stretches of narrow fringing reefs along southwestern coasts. The islets of St Brandon are bound to the east by an extensive arc of fringing reef. Reef mapping of the Mascarenes using satellite imagery provides an estimate of 705 km2 of shallow reef habitats. These areas have been modified over geological time by changes in sea level, ocean-atmosphere disturbances and biological and chemical forcing. Further modification has resulted from historical changes in land-use patterns. Recent economic development has placed many of these reefs at risk from anthropogenic impact. The reefs of the Mascarenes have escaped mass mortality from bleaching to date, which increases their conservation significance within the wider Indian Ocean. The reefs are poorly protected. A case study shows how a geographic information system incorporating reef-habitat maps can help formulate and demonstrate Marine Protected Area boundaries.
Competition between hard corals and macroalgae is a key ecological process on coral reefs, especially during reef degradation, which often involves a 'phase-shift' from coral- to alga-dominated reefs. However, there are relatively few published studies exploring the variability in this interaction. This paper expands the range of documented coral-algal interactions by comparing the mechanisms and outcomes of interactions involving 3 different algal species, as well as general, mixed algal turfs. Mixed filamentous turfs had relatively minor effects on corals. However, the turfing filamentous red alga Corallophila huysmansii provided a dramatic exception to this pattern, being able to settle on, overgrow and kill live coral tissue, perhaps due to allelochemical production by the alga, although this was not directly demonstrated. The larger filamentous alga Chlorodesmis fastigiata ('Turtle Weed'), which is conspicuous and abundant on Indo-Pacific reefs, caused polyp retraction but had little other noticeable effect on coral tissue. A corticated red alga Hypnea pannosa, frequently observed living within colonies of the branching coral Porites cylindrica, did not have a major impact on underlying coral tissue, even over a period of 1 yr, apparently because its relatively translucent and porous thallus structure does not strongly inhibit coral tissue functions. Together, the results demonstrate the considerable potential variability in both the process and outcome of coral-algal competition. This variability can be effectively interpreted in terms of the limited number of mechanisms by which algae can affect corals, with these mechanisms depending largely on the properties (physical, biological, chemical) of the algae. Given the central importance of coral-algal competition to the process of coral reef phase-shifts, understanding the variability and complexity in such competition will have important implications for the prediction and consequences of such phase-shifts.
Shipwrecks deteriorate and the probability of a release of oil increases with time on the sea floor. The potential leakage is a risk to the marine environment and may also have social and economic consequences. The purpose of this study was to evaluate existing methods for risk assessment of shipwrecks and suggest a generic risk assessment framework. A risk assessment is necessary for providing decision support on remediation actions and thus enabling an efficient use of available resources. Existing risk assessment methods aimed for assessing shipwrecks were evaluated by comparison to relevant parts of an international standard on risk management. The comparison showed that existing methods lack several key components of risk assessment procedures. None of the evaluated methods provide a comprehensive risk assessment for potentially polluting shipwrecks and few take into account uncertainty and sensitivity. Furthermore, there is a need to develop risk assessment methods considering long-term effects of continuous release of oil into the marine environment. Finally, a generic comprehensive framework for risk assessment of shipwrecks is suggested.
The nature and degree of impact of ship groundings on coral reefs and subsequent recovery is not well understood. Disturbed benthic and associated fish assemblages may take years-decades to return to pre-impact levels or may attain alternate stable states. Rose Atoll, a small, remote coral atoll in the central South Pacific, was impacted by a major ship grounding and associated contaminant spill in October 1993. Coral reef fish assemblages were quantitatively surveyed at the site of impact and compared to other nearby sites along the western outer reef slope in August 1995, February 2002, February 2004, and March 2006. In 1995, herbivorous surgeonfishes dominated the site, likely attracted to the early algal blooms. During 2002-2006, both numbers and biomass of pooled herbivorous fishes were significantly greater at the wreck site than at the other reef-slope survey sites. This greater abundance, where some corroding steel debris remained, was associated with significantly greater substratum cover by opportunistic algae (both turf and cyanobacteria). Thus, more than 13 yrs later, the grounding of this ship is still impacting algal growth and herbivorous reef-fish populations. While continued ecosystem monitoring at Rose Atoll is necessary for a full understanding of recovery rates by fish assemblages from such major anthropogenic disturbances, in the event of future groundings, containment of the contaminant spill and prompt removal of all metallic debris is recommended to preserve ecosystem integrity.
Metals attributed to pollution may increase their concentrations above the geological background and pose toxic challenges towards humans and biota. We analysed sixteen Kelp Gull eggs and eggshells for 30 metallic elements from the Swartkops Estuary (SE), an important recreational, industrial, and ecological asset for Port Elizabeth, the region, and South Africa. Mean concentrations for eggshell and egg content for Hg was 0.02 and 0.4 mg/kg dm, Cr was 4 and 18 mg/kg dm (the highest yet recorded for any gull or tern egg), for Zn 2.1 and 62 mg/kg dm, for Sr 880 and 12 mg/kg dm, for V 170 and 1.3 mg/kg dm, and for Co 1.7 and 0.002 mg/kg dm, respectively. Zinc, Se, and Hg, increased on a dry-mass basis from sediment via small fish to gull egg content, indicating bioaccumulation. No effect on eggshell thickness was seen. We also determined that eggshell concentrations cannot be used as a proxy for egg content concentrations. Mercury, Cr, V, Co, and Zn were elements we identified as potentially problematic that require source identification and mitigation. Further research into other high-trophic animals such as herons, egrets, cormorants, and otters in the SE system is proposed.
Coral reefs support rich levels of biodiversity, but are globally threatened by a multitude of factors, including land-sourced pollutants. Concentrations of organochlorine pesticides (OCPs) in three species of coral reef invertebrate at five sites along the Maputaland coast, South Africa were quantified. We aimed to assess spatial and interspecies variations in pesticide accumulation. Markedly high levels of a range of OCP residues were detected within tissues, with total concentrations (ng g−1 ww) ranging from 460 to 1200 (Sarcophyton glaucum), 1100–3000 (Sinularia gravis) and 450–1500 (Theonella swinhoei), respectively. A decreasing gradient in total pesticide concentrations was detected southward from Regal Reef, opposite Lake Sibaya, the hypothesised source of the pollutants. Observed gradients in pesticide concentrations and nitrogen isotope signatures indicated coastal groundwater to be the likely source of the pollutants. Further studies are required to assess the potential ecotoxicological impacts of these contaminants at the organismal and ecosystem level.
The Phoenix Islands Protected Area is in a naturally iron-poor region in the equatorial central Pacific. The introduction of iron to this environment from shipwrecks is linked to proliferation of turf algae and cyanobacterial mats, and the formation of degraded ‘black reefs’. No recovery has been documented at black reefs observed between 2003 and 2015.
Bio-monitoring of pollutants in long-lived animals such as sea turtles is an important tool in ecotoxicology. We present the first report on metallic elements in sea turtle eggs from the Indian Ocean. Eggs of the leatherback and loggerhead turtle that breed on the Indian Ocean coast of South Africa were analysed for 30 elements. The eggshells and egg contents of the loggerhead turtle, the smaller of the two species, had higher or significantly higher concentrations than leatherbacks, except for strontium - the reason is unknown. Elemental concentrations in eggshells and contents were the same or lower compared with other studies. The differences in concentrations in the egg contents and eggshells between the two species are likely due to different trophic levels, migration patterns, life histories, age, and growth, as well as differences in pollution sources and the uptake, retention and elimination characteristics of the different elements by the different species. We found no congruence between patterns in eggshells and corresponding egg contents, for both species. However, eggshells and egg contents showed congruence between species. The lack of congruence between eggshells and contents within each species precludes using eggshell concentrations as a proxy for egg content concentrations. Copper, strontium, and selenium occurred at concentrations higher than available toxic reverence values. Further research is warranted, including the analyses of POPs, as well as possible deme discrimination based on compositional pattern differences. Turtles serve as 'active samplers' returning to the same location to breed-something that is not practical with marine mammals or elasmobranchs.
The multiple-contamination of heavy metals and nutrients worsens increasingly and Ulva sp. green tide occurs almost simultaneously. To reveal the biological mechanism for outbreak of the green tide, Ulva pertusa was exposed to seven-day-multiple-contamination. The relation between pH variation (VpH), Chl a content, ratio of (Chl a content)/(Chl b content) (Rchla/chlb), SOD activity of U. pertusa (ASOD) and contamination concentration is [Formula: see text] (p<0.05), Cchla=0.88±0.09-0.01±0.00×CCd (p<0.05), [Formula: see text] (p<0.05), and [Formula: see text] (p<0.05), respectively. Cammonia, CCd and CZn is concentration of ammonia, Cd(2+) and Zn(2+), respectively. Comparing the contamination concentrations of seawaters where Ulva sp. green tide occurred and the contamination concentrations set in the present work, U. pertusa can adapt to multiple-contaminations in these waters. Thus, the adaption to multiple-contamination may be one biological mechanism for the outbreak of Ulva sp. green tide.
The drivers behind microplastic (up to 5 mm in diameter) consumption by animals are uncertain and impacts on foundational species are poorly understood. We investigated consumption of weathered, unfouled, biofouled, pre-production and microbe-free National Institute of Standards plastic by a scleractinian coral that relies on chemosensory cues for feeding. Experiment one found that corals ingested many plastic types while mostly ignoring organic-free sand, suggesting that plastic contains phagostimulents. Experiment two found that corals ingested more plastic that wasn't covered in a microbial biofilm than plastics that were biofilmed. Additionally, corals retained ~ 8% of ingested plastic for 24 h or more and retained particles appeared stuck in corals, with consequences for energetics, pollutant toxicity and trophic transfer. The potential for chemoreception to drive plastic consumption in marine taxa has implications for conservation.
A survey of seabirds and turtles at St Brandon’s Rock, 400 km north of Mauritius, was undertaken in 2010. We estimated that 1 084 191 seabirds comprising seven breeding species and excluding non-breeders were present at the archipelago and we counted 279 turtle tracks and nesting pits of green turtles Chelonia mydas. Hawksbill turtles Eretmochelys imbricata were also present. Analyses of 30 different islets that make up the atoll showed that the seabird species mostly partitioned their use of islets based on islet size, with four species preferring larger islets and two species preferring smaller islets. Alien species introduced historically are still present and other threats, such as shipwrecks, remain. We propose conservation and other measures that should adequately protect the birds, turtles and coral reef by treating the atoll as a system.
Isolated coral atolls are not immune from marine debris accumulation. We identified Southeast Asia, the Indian sub-continent, and the countries on the Arabian Sea as most probable source areas of 50 000 items on the shores of St. Brandon’s Rock (SBR), Indian Ocean. 79% of the debris was plastics. Flip-flops, energy drink bottles, and compact fluorescent lights (CFLs) were notable item types. The density of debris (0.74 m-1 shore length) is comparable to similar islands but less than mainland sites. Intact CFLs suggests product-facilitated long-range transport of mercury. We suspect that aggregated marine debris, scavenged by the islands from currents and gyres, could re-concentrate pollutants. SBR islets accumulated debris types in different proportions suggesting that many factors act variably on different debris types. Regular cleaning of selected islets will take care of most of the accumulated debris and may improve the ecology and tourism potential. However, arrangements and logistics require more study.
Metal-smelting and combustion processes are the major anthropogenic sources for the emission of metals to the atmosphere. Metals emitted this way are generally bound in small particles with the potential for atmospheric long-range transport and contamination. Sediments are the ultimate sink for metals emitted to the aquatic environment; this is most evident in coastal and estuarine sediments. Besides direct emissions, man-made environmental changes such as acidification, oxygen depletion, and draining of waterlogged areas may mobilize metals not otherwise available to organisms. The speciation of metals is an important determinant for their bioavailability, uptake, and toxicity in the environment. Organisms have developed a wide range of mechanisms for the internal handling and storage of essential and/or toxic metals. No metal other than mercury is consistently biomagnified along food chains. In the environment, the most adverse impacts of metals (on populations) have been caused by organic tin compounds used in antifouling paints and aluminum mobilized by acid rain. High concentrations of organic mercury and cadmium in certain organisms may cause concerns for the health of human populations that rely heavily on their use as food items.
The influence of nutrients on the growth of Ulva prolifera was studied in the SYS by field experiments. The wet weight of U. prolifera gradiently increased from 11.94% to 25.92% in proportion to contents of DIN supply, which indicated DIN content was essentially decisive for the output of U. prolifera blooms. Continuous nutrient supply could promote the growth of U. prolifera, indicated by the increase of growth rate from 10.46% of the batch culture to 42.17% of the in situ culture. The higher P utilized rate in all treatments showed P was the potential limited factor for the growth of U. prolifera. Moreover, it was calculated about 4.1×10(5)t organic matter was begot by U. prolifera in the whole Yellow Sea based on the statistical relationship between output of U. prolifera and DIN content. This work could be convenient to evaluate biomass and prepare enough tools to manage U. prolifera.
Copyright © 2015 Elsevier Ltd. All rights reserved.
Fragments of leaded paint sampled from abandoned boats have been ground as a composite and added in different quantities to aliquots of clean estuarine sediment in order to examine the mobility and bioaccessibility of Pb. Concentrations of Pb mobilised by sea water increased with increasing quantity of paint present, but the percentage of total Pb mobilised was greatest from paint-free sediment. Lead mobilisation was enhanced in the presence of the protein, bovine serum albumin, a surrogate for the digestive fluids of deposit-feeding invertebrates, but, likewise, the percentage of Pb mobilised was greatest from paint-free sediment. Lower percentage mobility and bioaccessibility in contaminated sediment than in paint-free sediment is attributed to the relatively low solubility and amenability of Pb compounds in the paint matrix. Despite the low mobility of Pb, however, sediment contaminated by as little as 0.2% paint is predicted to result in dissolved concentrations that exceed available water quality standards.
Understanding the role played by sunken vessels in Mediterranean marine ecosystems is acquiring increasing importance. The aim of this research was to study the fish communities associated with four shipwrecks, by means of underwater visual censuses performed by a remotely operated vehicle, and to test the differences in composition of fish assemblages between these shipwrecks and the adjacent soft bottoms, considered as control sites. Multivariate analysis on the total fish assemblage showed significant differences between wrecks and controls. Results also showed higher levels of species richness and abundance near all wrecks than at a short distance from them on soft bottoms, thus indicating that these sunken vessels, thanks to their higher habitat complexity, act as artificial reefs, attracting aggregations of fish species and leading to a greater diversification of the local fish assemblage. Nevertheless, shipwrecks, which are an ideal target for recreational fishermen, could contribute to the over-exploitation of some high-value fish species, such as Mycteroperca rubra, Dentex dentex and Diplodus spp., attracted by the artificial hard substrate of the vessel-reefs. The recent European directives suggest an urgent need for a better understanding of the crucial role played by these potential sources of pollutants on marine environments and ecosystems. An ecosystem approach to study and monitor these pollutant sources is, therefore, mandatory for appropriate remediation and/or mitigation of the potential negative effects on a productive and healthy ocean.
The concentrations of total organic carbon (TOC), total petroleum hydrocarbons (TPH), and petroleum-related heavy metals were determined in sediment samples collected from eight stations along the coastal area in Kuwait. The TOC concentrations ranged from 5.21 to 24.89 mg/g dry sediment. The TPH concentrations were variable and ranged from 7.43 to 458.61 μg/g dry sediment. The highest TPH concentrations were found near the Shuaiba Industrial Area and in the Shuwaikh Port where both industrial and boating activities and land-based wastewater discharges are most common. Petroleum-related heavy metals, namely lead, nickel, and vanadium, were detected at all stations. The data support the premise that industrial wastewater discharges, waste and port activities are the major sources of pollution in the study areas. The concentration of TPH and TOC, carbonate content, and distance from the pollution sources were also investigated.
Coral reefs represent the most spectacular and diverse marine ecosystem on the planet as well as a critical source of protein and income for many millions of people. However, the combined effects of human activities have led to a rapid decline in the health of reefs worldwide, with many now facing complete destruction. This book provides an integrated overview of the function, physiology, ecology, and behaviour of coral reef organisms. Each chapter is enriched with a selection of 'boxes' on specific aspects written by internationally recognised experts. The emphasis in this book is on the organisms that dominate this marine environment although pollution, conservation, climate change, and experimental aspects are also included. Indeed, particular emphasis is placed on conservation and management due to the habitat's critically endangered status. A global range of examples is employed which gives the book international relevance. Charles R. C. Sheppard, Simon K. Davy, and Graham M. Pilling 2009. All rights reserved.
Fertilization success of gametes from the scleractinian coral Goniastrea aspera was used to determine toxic effects of the trace metals copper, zinc and cadmium. Spawned eggs and sperm were collected from adult colonies of G. aspera and dosed separately with different concentrations of copper, zinc or cadmium, with normal seawater used as controls. The eggs and sperm were then combined to allow fertilization to occur. After 5 h development time, the number of fertilized and developing embryos and unfertilized eggs were counted and recorded to determine percentage fertilization. Copper was the most toxic metal, whereas cadmium and zinc did not affect fertilization success at the concentrations tested. High fertilization rates of 91%±3.2% and 93%±4.0% were recorded in the copper controls and in 2 μg/l of copper, respectively. However, fertilization success was significantly reduced to 41%±7.1% at 20 μg/l of copper, and
In this paper, we review observations, theory and model results on the monsoon circulation of the Indian Ocean. We begin with a general overview, discussing wind-stress forcing fields and their anomalies, climatological distributions of stratification, mixed-layer depths, altimetric sea-level distributions, and seasonal circulation patterns (Section 2). The three main monsoon circulation sections deal with the equatorial regime (Section 3), the Somali Current and western Arabian Sea (Section 4), and the Bay of Bengal, seasonally reversing monsoon currents south of India and Sri Lanka, and the eastern and central Arabian Sea (Section 5). For the equatorial regime, we discuss equatorial jets and undercurrents, their interactions with the eastern and western boundaries, and intraseasonal and vertically propagating signals. In the Somali Current section, we describe the ocean's responses to the summer and winter monsoon winds, and outline the modelling efforts that have been carried out to understand them. In the Bay of Bengal section, we present observational and modeling evidence showing the importance of remote forcing from the east, which to a large extent originates along the equator. In the following three sections, we review the southern-hemisphere subtropical regime and its associated boundary currents (Section 6), the Indonesian Throughflow (Section 7), the Red Sea and Persian Gulf circulations (Section 8), and discuss aspects of their interactions with other Indian-Ocean circulations. Next, we describe the Indian Ocean's deep and shallow meridional overturning cells (Section 9). Model results show large seasonal variability of the meridional overturning streamfunction and heat flux, and we discuss possible physical mechanisms behind this variability. While the monsoon-driven variability of the deep cell is mostly a sloshing motion affecting heat storage, interesting water-mass transformations and monsoonal reversals occur in the shallow cross-equatorial cell. In the mean, the shallow cell connects the subduction areas in the southern subtropics and parts of the Indonesian Throughflow waters with the upwelling areas of the northern hemisphere via the cross-equatorial Somali Current. Its near-surface branch includes a shallow equatorial roll that is seasonally reversing. We close by looking at coupled ocean-climate anomalies, in particular the large events that were observed in the tropical and subtropical Indian Ocean in 1993/94 and 1997/98. These events have been interpreted as an independent Indian-Ocean climate mode by some investigators and as an ENSO-forced anomaly by others.
In this study we have used laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), to produce a high resolution coral record of rare earth elements (REE), Mn and Ba from coastal Porites corals from the Great Barrier Reef of Australia. Validation of the LA-ICP-MS technique indicated that the method provides accurate and reproducible (RSD = 13–18%) analysis of low concentration REE in corals (∼1 to 100 ppb). The REE composition in coral samples was found to closely reflect that of the surrounding seawater and distribution coefficients of ∼1–2 indicated minimal fractionation of the series during incorporation into coral carbonate. To explore the idea that coral records of REE can be used to investigate dissolved seawater composition, we analyzed two coastal corals representing a total of ∼30 yr of growth, including a 10-yr overlapping period. Comparable results were obtained from the two samples, particularly in terms of elemental ratios (Nd/Yb) and the Ce anomaly. Based on this evidence and results from the determination of distribution coefficients, we suggest that useful records of seawater REE composition can be obtained from coral carbonates. When compared to the REE composition of a mid shelf coral, coastal corals showed a significant terrestrial influence, characterized by higher REE concentrations (greater than 10 times) and light REE enrichment. The REE composition of coastal seawater inferred from the coral record was dependent on seasonal factors and the influence of flood waters. REE fractionation displayed a strong seasonal cycle that correlated closely with Mn concentration. We suggest that higher Nd/Yb ratios and higher Mn concentrations in summer result from scavenging of heavy REE by particulate organic ligands and Mn reductive dissolution respectively, both processes displaying higher rates during periods of high primary productivity. The Ce anomaly also displayed a strong seasonal cycle showing an enhanced anomaly during summer and during flood events. This is consistent with the Ce anomaly being primarily controlled by the abundance of Ce oxidizing bacteria. Based on these arguments, we suggest that the coral record of dissolved REE and Mn may be regarded as a useful proxy for biological activity in coastal seawater.
Analyses were performed for strontium, iron, manganese, magnesium, sodium, and potassium in the skeletal material of three species of scleractinian corals. The results indicate that skeletal mineralogy is the predominant factor controlling the incorporation of minor elements into the aragonitic skeletal material. The distribution of minor elements both between and within the skeletal material of individual organisms is heterogeneous. Generic and specific association appear to control the distribution of certain minor elements between individual organisms. The distribution of minor elements within the skeletal material of a single organism does not appear to be related to calcification rate for the organisms investigated.
Coral reefs in a marine reserve at Sodwana Bay (27°30'S) make it a premier dive resort. Corals are at the southern limits of their African distribution on these reefs which are dominated by soft corals. The coastline is exposed and turbulent. An assessment of the degree to which sport diving damages the reefs is needed for their management. This study showed that recognizable diver damage is generally concentrated in heavily dived areas. This damage and that of unknown cause probably attributable to divers exceeded natural damage on the reefs, despite the normally rough seas. Fishing line discarded in angling areas also caused considerable damage by tangling around branching corals which become algal fouled and die. Heaviest damage was caused in isolated areas by a minor crown-of-thorns outbreak. A linear regression indicated that 10% diver damage occurs at 9000 dives per dive site p. a. Taking uncertainty into account, a precautionary limit of 7000 dives per dive site p. a. was recommended. Further recommendations are that the reefs be zoned in terms of their sensitivity to diver damage, depth and use by divers according to qualification, and a ban be placed on the use of diving gloves to reduce handling of the reefs.