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Branch tips of the branching zooxanthellate stony coral Stylophora pistillata . The white tips of the branches, where the most active accretion of new calcium carbonate skeleton takes place, do not contain zooxanthellae. Photography by Tim Wijgerde.
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... we will provide an overview of methods to characterize photosynthesis in these animals, highlight important data obtained with these methods and present conceptual frameworks that describe how photosynthesis is controlled in marine symbiotic invertebrates. Hereby, we will be particularly focusing on zooxanthellate Scleractinia (stony corals, Fig. 1), a symbiosis that will be described in the next ...
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... and phosphorous in a natural ratio) enhances tissue growth in corals and increases the size of the symbiotic population and pigmentation per cell leading to thicker tissue (cf Trench & Fisher 1983) and higher photosynthetic rates per unit of coral surface under increasing light than their food-limited conspecifics ( Houlbrèque et al. 2004; Fig. 10A). This enables highly fed corals to calcify faster under high light than food-limited corals ( Osinga et al. 2011). In contrast to these findings, corals exposed to increased DIN levels displayed a higher P max without a corresponding increase in calcification, despite the denser population of zooxanthellae residing in those corals ...
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... enables highly fed corals to calcify faster under high light than food-limited corals ( Osinga et al. 2011). In contrast to these findings, corals exposed to increased DIN levels displayed a higher P max without a corresponding increase in calcification, despite the denser population of zooxanthellae residing in those corals (Marubini & Davies 1996; Fig 10B). There are two possible explanations for this apparent paradox. ...
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... reduced by increasing the flow ( Mass et al. 2010;Schutter et al. 2011) or by increasing the availability of DIC, thus reducing carbon limitation of coral photosynthesis. Indeed, several authors reported on increased photosynthetic activity in corals under elevated DIC levels (e.g. Herfort et al. 2008;Marubini et al. 2008; see next subsection). Fig. 11 depicts a predicted change in P/E curve following an increase in flow. Under high flow, P n will linearly increase until Pn max has been reached, whereas under low flow, inhibition of net oxygen evolution due to photorespiration will increase with increasing irradiance, thus resulting in a lower Pn max and a quantum yield (slope) that ...
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... in P/E curve following an increase in flow. Under high flow, P n will linearly increase until Pn max has been reached, whereas under low flow, inhibition of net oxygen evolution due to photorespiration will increase with increasing irradiance, thus resulting in a lower Pn max and a quantum yield (slope) that decreases with increasing irradiance. Fig. 11. Predicted effect of flow on photosynthesis in corals. The presumed thickness and pigmentation of the coral tissue corresponding to the P/E curves is equal in both conditions as ...
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... La eficiencia fotosintética (α) se calculó a partir de la pendiente de la fase lineal de la fotosíntesis a intensidades de luz sub-saturantes. El punto de compensación (E c ) correspondió a la intensidad de luz donde la tasa de fotosíntesis bruta igualó la respiración (Osinga et al., 2012). Los parámetros fotosintéticos se normalizaron por unidad de área, calculada con la técnica del papel de aluminio (Marsh, 1970). ...
... The photosynthetic efficiency (α) was calculated from the slope of the linear increase in photosynthesis at sub-saturating light intensities. The compensation point (E c ) was the light intensity where gross photosynthesis matched respiration (Osinga et al., 2012). The photosynthetic parameters were normalized per unit area, which was calculated with the aluminium foil technique (Marsh, 1970). ...
El deterioro de las propiedades ópticas del agua, o aumento de turbidez, debido a perturbaciones antropogénicas es un fenómenogeneralizado en zonas costeras. Los efectos sobre el ambiente lumínico submarino y la fisiología de corales simbióticos, quedependen principalmente de la luz para sobrevivir y mantener elevada calcificación, han sido poco explorados. En este estudiose describen los efectos de la pluma del Canal del Dique sobre el ambiente lumínico, sobrevivencia y fisiología de corales en el arrecifeVaradero. Se realizó un trasplante recíproco con fragmentos de Orbicella faveolata entre una zona somera en Varadero (3.5 m) y un sitio contrastante con aguas más claras a mayor profundidad (12 m) con intensidad de luz comparable. La columna de agua en Varadero se encontró fuertemente estratificada, favoreciendo el aislamiento del arrecife de la pluma. Corales trasplantados a Varadero mostraron mayor sobrevivencia posiblemente debido a reducción de estrés lumínico y mayor heterotrofía. Su fisiología indicó aclimatación a poca luz y limitado potencial autotrófico, evidenciando un riesgo para la sobrevivencia de corales a mayor profundidad. Los resultados indican que un mayor deterioro de las propiedades ópticas del agua en la bahía de Cartagena por perturbaciones antropogénicas en la cuenca del río Magdalena y en la zona costera pone en riesgo la prevalencia del arrecife Varadero.
... Temperature is an important factor influencing coral growth and photosynthesis [4], and elevated temperature induces oxidative stress and coral bleaching [5,6]. Coral is typically sensitive to temperature changes, resulting in coral stress at the cellular level. ...
... All seawater parameters and samples (n = 3) were collected around midday, at the same time as coral sampling, which might favor observing extreme values of light intensity. 4 3− (µg-atm P-PO 4 L −1 ) 0.23 ± 0.14 0.49 ± 0.02 ...
... The coral nubbin for each treatment was weighed in seawater; both the seawater temperature and salinity were recorded for calculating the density of the sea water, and a glass reference was weighed in both sea water and air; then, the density of P. acuta, taken as 2.01 g cc −1 [44,45], was used to calculate coral dry weight in Equation (4). The determined weights were used in Equation (5): ...
Increasing levels of greenhouse gases lead to ocean warming, which affects a range of marine organisms. Corals live in a narrow temperature range and become stressed when the temperatures change. Bleaching occurs when the temperature exceeds the coral’s threshold, and can be severe when this is combined with other stressors such as light. In order to understand how temperature and light affect corals in their physiological responses and photosynthetic performance, Pocillopora acuta from Maiton Island (MT) and Panwa Cape (PW), representing different environments, were investigated. The results show that light and temperature had by regime different effects on Symbiodiniaceae photosynthesis and the coral growth rate. There was a synergistic effect of elevated temperature and light on photosynthesis, as observed in the photochemical efficiency and pigment contents, suggesting photo-damage. A higher growth rate in Panwa corals was observed in control, and while elevated temperature reduced coral growth. Elevated temperature affected the Panwa coral less, suggesting that corals from this regime might be able to recover when the temperature returns to normal. This information is important for predicting the coral responses to elevated temperature especially in the summer, as regards the possibility of coral bleaching.
... In the extraction of data for meta-analysis of the effects of pollutants on photosynthetic efficiency, we focused on maximum quantum yield (MQY) instead of effective quantum yield (EQY). MQY is represented by F v (= F m -F 0 ) / F m , where F m is maximal fluorescence and F 0 is background fluorescence (Osinga et al., 2012). MQY is measured after the coral has been dark-adapted, meaning a complete relaxation of photochemical quenching activity (Osinga et al., 2012). ...
... MQY is represented by F v (= F m -F 0 ) / F m , where F m is maximal fluorescence and F 0 is background fluorescence (Osinga et al., 2012). MQY is measured after the coral has been dark-adapted, meaning a complete relaxation of photochemical quenching activity (Osinga et al., 2012). EQY is measured under steady but illuminated conditions and can therefore be more variable (Enríquez and Borowitzka, 2010). ...
Reduced water quality degrades coral reefs, resulting in compromised ecosystem function and services to coastal communities. Increasing management capacity on reefs requires prioritization of the development of data-based water-quality thresholds and tipping points. To meet this urgent need of marine resource managers, we conducted a systematic review and meta-analysis that quantified the effects on scleractinian corals of chemical pollutants from land-based and atmospheric sources. We compiled a global dataset addressing the effects of these pollutants on coral growth, mortality, reproduction, physiology, and behavior. The resulting quantitative review of 55 articles includes information about industrial sources, modes of action, experimentally tested concentrations, and previously identified tolerance thresholds of corals to 13 metals, 18 pesticides, 5 polycyclic aromatic hydrocarbons (PAHs), a polychlorinated biphenyl (PCB), and a pharmaceutical. For data-rich contaminants, we make more robust threshold estimates by adapting models for Bayesian hierarchical meta-analysis that were originally developed for biopharmaceutical application. These models use information from multiple studies to characterize the dose-response relationships (i.e., Emax curves) between a pollutant's concentration and various measures of coral health. Metals used in antifouling paints, especially copper, have received a great deal of attention to-date, thus enabling us to estimate the cumulative impact of copper across coral's early life-history. The effects of other land-based pollutants on corals are comparatively understudied, which precludes more quantitative analysis. We discuss opportunities to improve future research so that it can be better integrated into quantitative assessments of the effects of more pollutant types on sublethal coral stress-responses. We also recommend that managers use this information to establish more conservative water quality thresholds that account for the synergistic effects of multiple pollutants on coral reefs. Ultimately, active remediation of local stressors will improve the resistance, resilience, and recovery of individual reefs and reef ecosystems facing the global threat of climate change.
... Each coral fragment was incubated for a total of 105 minutes per trial, 181 and each fragment was measured a total of seven times. The photosynthetic parameters were 182 calculated according to standard methods (Osinga et al., 2012). Briefly, photosynthesis-183 irradiance (PE) curves were constructed by plotting the rate of change in oxygen concentration 184 and irradiance. ...
Scleractinian corals form the foundation of coral reefs by secreting skeletons of calcium carbonate. Their intracellular algal symbionts (Symbiodiniaceae) translocate a large proportion of photosynthate to the coral host, which is required to maintain high rates of calcification. Global warming is causing dissociation of coral host and algal symbiont, visibly presented as coral bleaching. Despite decades of study, the precise mechanisms of coral bleaching remain unknown. Separating the thermal stress response of the coral from the algal symbiont is key to understanding bleaching in tropical corals. The facultatively symbiotic northern star coral, Astrangia poculata, naturally occurs as both symbiotic and aposymbiotic (lacking algal symbionts) polyps - sometimes on the same coral colony. Thus, it is possible to separate the heat stress response of the coral host alone from the coral in symbiosis with its symbiont Breviolum psygmophilum. Using replicate symbiotic and aposymbiotic ramets of A. poculata, we conducted a chronic heat stress experiment to increase our understanding of the cellular mechanisms resulting in coral bleaching. Sustained high temperature stress resulted in photosynthetic dysfunction in B. psygmophilum, including a decline in maximum photosynthesis rate, maximum photochemical efficiency, and the absorbance peak of chlorophyll a. Interestingly, the metabolic rates of symbiotic and aposymbiotic corals were differentially impacted. RNAseq analysis revealed more differentially expressed genes between heat-stressed and control aposymbiotic colonies than heat-stressed and control symbiotic colonies. Notably, aposymbiotic colonies increased the expression of inflammation-associated genes such as nitric oxide synthases. Unexpectedly, the largest transcriptional response was observed between heat-stressed and control B. psygmophilum, including genes involved in photosynthesis, response to oxidative stress, and meiosis. Thus, it appears that the algal symbiont suppresses the immune response of the host, potentially increasing the vulnerability of the host to pathogens. The A. poculata-B. psygmophilum symbiosis provides a tractable model system for investigating thermal stress and immune challenge in scleractinian corals.
... Oxygen concentrations inside the compartments within the chamber were measured with a 4-channel fiber optical oxygen meter system (FireSting, Pyroscience, Germany). The photosynthetic efficiency (a), compensating irradiance (E c ), saturating irradiance (E k ), respiration rates (R d ), and maximum photosynthetic rates (P max ), were calculated following Iglesias-Prieto and Trench (1994) and Osinga et al. (2012). ...
Coral reefs are undergoing degradation due to overexploitation, pollution, and climate change. Management and restoration efforts require that we gain a better understanding of the complex interactions between corals, their microbiomes, and their environment. For this purpose, Varadero Reef near Cartagena, Colombia, serves as an informative study system located at the entrance of the Bay of Cartagena adjacent to the Canal del Dique, which carries turbid and polluted water into the bay. Varadero’s survival under poor environmental conditions makes it a great study site for investigating the relationship between the microbiome and coral resistance to environmental stressors. To determine whether the microbiomes of Varadero corals differ from those in less impacted sites, we conducted a reciprocal transplant experiment by relocating coral fragments from Varadero as well as a geographically proximate reef that is less affected by plume dynamics (Rosario) across a gradient of turbidity (low, medium, and high). After 6 months of acclimatization, transplanted corals developed site-specific microbiomes that differed significantly from pre-transplant microbiomes, and corals transplanted to the highly impacted site from both Varadero and Rosario site saw higher mortality and an increase in overall microbial diversity. In combination with physiology and survivorship outcomes pointing to a limit in the corals’ photoacclimative capacity, our results indicate that, rather than surviving, Varadero Reef is experiencing a slow decline, and its corals are likely on the brink of dysbiosis. With continued anthropogenic interference in marine environments, sites such as Varadero will become increasingly common, and it is imperative that we understand how corals and their microbial symbionts are changing in response to these new environmental conditions.
... They describe that F 0 /F m , (dV/dt) 0 and VJ refer to the structure and function of PSII while V I , t Fmax and S m concern the activity of the electron transport chain (ETC) beyond Q A . Among parameters of chlorophyll fluorescence, the maximum PSII efficiency, as given by F v /F m in dark-adapted leaves is more often used in research (Su et al., 2015) probably because it is more frequently used and commonly available from early pulse amplitude modulated (PAM) fluorimeters (Osinga et al., 2012). The ratiometric normalization of F v /F m also facilitates ease of results interpretation. ...
The aim of experiments was to investigate a maximal efficiency of PSII, as a marker indicating growth, vigor, energetic value and physiological activity of sorghum fertilized with wastes from a biomass biodigestion to methane in a distillery integrated with a biogas plant using corn grains as substrate. The sorghum plants grown outdoor in different climate and in pots and in field were fertilized with different doses of the waste or Apol-humus – a soil improver and Stymjod – a nano-organic-mineral fertilizer. The maximal efficiency of PSII, in comparison with plant growth and health, chlorophyll content, gas exchange, activity of selected enzymes, element content in leaves and energetic value were studied. The wastes applied to soil resulted in increased maximal efficiency of PSII and the doses of 30 m³ ha⁻¹ and 40–50 m³ ha⁻¹ of the non-centrifuged and centrifuged ones, respectively, were most efficient. This enhancement was associated with the increased kinetics of plant growth, their health, fresh and dry biomass and physiological activity of plants as evidenced by activity of acid and alkaline phosphatase, RNase and dehydrogenase, as well as by gas exchange: net photosynthesis, transpiration, stomatal conductance, intercellular CO2 concentration and index of chlorophyll content in leaves. The fertilization with Apol-humus and Stymjod additionally increased maximal photochemical efficiency of PSII and plant development, biomass yield and physiological activity. The results indicate that waste from a biomass biodigestion to methane can be used as a natural fertilizer in sorghum crops and this ensures their recycling and environmental protection. The measurement values of maximal efficiency of PSII were proportionally to the vigor, growth and physiological activity of the plants. The obtained results indicate that the maximal efficiency of PSII in sorghum plants is a non-destructive method for defining the degree of growth and may be used as a marker of plant vigor and health, development and physiological activity expressed by gas exchange and activity of selected enzymes.
... Table 1 identifies that few researchers have utilised the six parameters discussed by Strasser et al. (2000). The parameter Fv/Fm is more frequently occurring and widely used (Su et al., 2015); putatively because it is widely used and commonly available from early pulse amplitude modulated (PAM) fluorimeters (Osinga et al., 2012). The ratio-metric normalisation of Fv/Fm also facilitates ease of interpretation. ...
The effect of drought stress on continuous excitation chlorophyll fluorescence parameters and the OJIP transient is examined in cultivars of Acer campestre, A. platanoides and A. pseudoplatanus. Comparisons between whole tree level drought and desiccation of detached leaves under laboratory conditions is evaluated using both fluorescence parameters and differential kinetics. Data presented in this study suggests similarities exist between drought and desiccation. Chlorophyll fluorescence parameters which are both suitable and unsuitable at identifying drought stress are discussed and evaluated. New or uncommon fluorescence parameters and methods of analysis which may prove beneficial as drought detection tools are assessed. The over utilisation of the parameter Fv/Fm is also discussed. Results suggest utilisation of the parameters PIABS, Fo/Fm and V0(Bo) is recommended in preference to Fv/Fm, in studies aiming to identify drought stress in trees.
... The symbiosis between scleractinian corals and phototrophic dinoflagellates (zooxanthellae) has been studied intensively (reviewed in Furla et al., 2005;Weis, 2008;Osinga et al., 2012). ...
... Factors reported to influence the efficiency of photosynthetic processes inside corals include light (reviewed in Osinga et al. 2012), temperature (reviewed in Smith et al., 2005), nutrients (reviewed in Osinga et al., 2011) and gas exchange (e.g. Dennison and Barnes, 1988;Finelli et al., 2006). ...
Rates of dark respiration and net photosynthesis were measured on six replicate clonal fragments of the stony coral Galaxea fascicularis (Linnaeus 1767), which were incubated under twelve different combinations of dissolved oxygen (20%, 100% and 150% saturation), dissolved carbon dioxide (9.5 and 19.1 μmol L(-1)) and water flow (1-1.6 cm s(-1) versus 4-13 cm s(-1)) in a repeated measures design. Dark respiration was enhanced by increased flow and increased oxygen saturation in an interactive way, which relates to improved oxygen influx into the coral tissue. Oxygen saturation did not influence net photosynthesis: neither hypoxia nor hyperoxia affected net photosynthesis, irrespective of flow and pH, which suggests that hyperoxia does not induce high rates of photorespiration in this coral. Flow and pH had a synergistic effect on net photosynthesis: at high flow, a decrease in pH stimulated net photosynthesis by 14%. These results indicate that for this individual of G. fascicularis, increased uptake of carbon dioxide rather than increased efflux of oxygen explains the beneficial effect of water flow on photosynthesis. Rates of net photosynthesis measured in this study are among the highest ever recorded for scleractinian corals and confirm a strong scope for growth.
... Quantifying photosynthesis under different light fields, generally referred to as photosynthesis to irradiance (P/E) curves, describes the dynamics of photosynthesis. From these data, the light compensation point (where photosynthesis and respiration are equal), photosynthetic efficiency (the slope under light-limiting conditions), saturating irradiance, and the photosynthetic maximum can be determined (see diagram in Osinga et al., 2012). Photoacclimation of eight phylotypes of cultured Symbiodinium under two growth irradiances provide evidence for highly variable bio-physical and bio-optical measurements (Hennige et al., 2009). ...
... A recent study showed that during a heat stress experiment, corals began bleaching when Q m reached ∼0.4 and continued heat stress intensified the bleaching until the Q m reached ∼0.8 (when measurements were no longer possible due to the low level of symbionts) while control corals maintained Q m < 0.2 (Roth et al., 2012). Measuring chlorophyll fluorescence under various light regimes can also provide estimates of the relative electron transport rate (rETR) similar to P/E curves, but there are many problems and pitfalls with this approach Osinga et al., 2012). Despite its limitations, measuring chlorophyll fluorescence is an important noninvasive methodology to assess the physiological state of Symbiodinium and thus the coral. ...
... Despite its limitations, measuring chlorophyll fluorescence is an important noninvasive methodology to assess the physiological state of Symbiodinium and thus the coral. For more information on the methodologies and the instrumentation mentioned in this section see recent reviews Osinga et al., 2012). ...
Coral reef ecosystems thrive in tropical oligotrophic oceans because of the relationship between corals and endosymbiotic dinoflagellate algae called Symbiodinium. Symbiodinium convert sunlight and carbon dioxide into organic carbon and oxygen to fuel coral growth and calcification, creating habitat for these diverse and productive ecosystems. Light is thus a key regulating factor shaping the productivity, physiology, and ecology of the coral holobiont. Similar to all oxygenic photoautotrophs, Symbiodinium must safely harvest sunlight for photosynthesis and dissipate excess energy to prevent oxidative stress. Oxidative stress is caused by environmental stressors such as those associated with global climate change, and ultimately leads to breakdown of the coral–algal symbiosis known as coral bleaching. Recently, large-scale coral bleaching events have become pervasive and frequent threatening and endangering coral reefs. Because the coral–algal symbiosis is the biological engine producing the reef, the future of coral reef ecosystems depends on the ecophysiology of the symbiosis. This review examines the photobiology of the coral–algal symbiosis with particular focus on the photophysiological responses and timescales of corals and Symbiodinium. Additionally, this review summarizes the light environment and its dynamics, the vulnerability of the symbiosis to oxidative stress, the abiotic and biotic factors influencing photosynthesis, the diversity of the coral–algal symbiosis, and recent advances in the field. Studies integrating physiology with the developing “omics” fields will provide new insights into the coral–algal symbiosis. Greater physiological and ecological understanding of the coral–algal symbiosis is needed for protection and conservation of coral reefs.
Acclimatization through phenotypic plasticity represents a more rapid response to environmental change than adaptation and is vital to optimize organisms' performance in different conditions. Generally, animals are less phenotypically plastic than plants, but reef‐building corals exhibit plant‐like properties. They are light dependent with a sessile and modular construction that facilitates rapid morphological changes within their lifetime. We induced phenotypic changes by altering light exposure in a reciprocal transplant experiment and found that coral plasticity is a colony trait emerging from comprehensive morphological and physiological changes within the colony. Plasticity in skeletal features optimized coral light harvesting and utilization and paralleled significant methylome and transcriptome modifications. Network‐associated responses resulted in the identification of hub genes and clusters associated to the change in phenotype: inter‐partner recognition and phagocytosis, soft tissue growth and biomineralization. Furthermore, we identified hub genes putatively involved in animal photoreception–phototransduction. These findings fundamentally advance our understanding of how reef‐building corals repattern the methylome and adjust a phenotype, revealing an important role of light sensing by the coral animal to optimize photosynthetic performance of the symbionts.
