Contemporary cnidarian-algae symbioses are challenged by increasing CO2 concentrations (ocean warming and acidification) affecting organisms’ biological performance. We examined the natural variability of carbon and nitrogen isotopes in the symbiotic sea anemone Anemonia viridis to investigate dietary shifts (autotrophy/heterotrophy) along a natural pCO2 gradient at the island of Vulcano, Italy. δ13C values for both algal symbionts (Symbiodinium) and host tissue of A. viridis became significantly lighter with increasing seawater pCO2. Together with a decrease in the difference between δ13C values of both fractions at the higher pCO2 sites, these results indicate there is a greater net autotrophic input to the A. viridis carbon budget under high pCO2 conditions. δ15N values and C/N ratios did not change in Symbiodinium and host tissue along the pCO2 gradient. Additional physiological parameters revealed anemone protein and Symbiodinium chlorophyll a remained unaltered among sites. Symbiodinium density was similar among sites yet their mitotic index increased in anemones under elevated pCO2. Overall, our findings show that A. viridis is characterized by a higher autotrophic/heterotrophic ratio as pCO2 increases. The unique trophic flexibility of this species may give it a competitive advantage and enable its potential acclimation and ecological success in the future under increased ocean acidification.
Posts Tagged 'cnidaria'
Natural high pCO2 increases autotrophy in Anemonia viridis (Anthozoa) as revealed from stable isotope (C, N) analysis
Published 12 March 2015 Science ClosedTags: abundance, biological response, chemistry, cnidaria, field, Mediterranean, otherprocess, physiology, protists
Biogeochemical implications of decomposing jellyfish blooms in a changing climate
Published 5 January 2015 Science ClosedTags: biogeochemistry, biological response, cnidaria, dissolution, laboratory, mesocosms, multiple factors, primary production, South Pacific, temperature
Jellyfish often exhibit ‘boom and bust’ population dynamics whereby they proliferate rapidly and then die en masse and decompose. The few studies that have investigated post-bloom processes have not studied how changing ocean conditions will alter rates of decomposition. Climate change will result in warmer and more acidic waters, and studies therefore need to consider these factors in concert to determine their combined effect on decomposition processes. To quantify the effect, we measured oxygen consumption and nutrient regeneration rates during decomposition of Catostylus mosaicus in mesocosms at current average summer pH and temperature (pH 8.0 and 27 °C) as well as conditions projected for year 2100 (pH 7.8 and 30 °C) and compared these fluxes to control mesocosms without jellyfish over 12 days. We hypothesised that rates of jellyfish decomposition, as measured by oxygen demand and nutrient regeneration, would be accelerated in the end-of-century treatments, compared to present day treatments. Overall decomposition rates were only slightly elevated under end–of-century conditions, and the difference was only significant for ammonium fluxes from 19 h until 43 h after the experiment commenced. The difference between treatments was much smaller than would be expected due to the temperature increase, based on theoretical modelling of jellyfish decomposition which predicts a Q10 of 4.28, or a 1.5 fold increase in decomposition rates. This highlights the importance of investigating net effects on decomposition rates, as simultaneous shifts in temperature and pH may not follow patterns predicted due to one stressor alone. Ultimately, these results suggest that rates of oxygen consumption and nutrient regeneration resulting from collapsed jellyfish blooms may not change drastically over the next 100 years.
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A review and meta-analysis of the effects of multiple abiotic stressors on marine embryos and larvae
Published 16 December 2014 Science ClosedTags: biological response, cnidaria, crustaceans, echinoderms, mollusks, mortality, multiple factors, reproduction, review, salinity, temperature
Marine organisms are simultaneously exposed to anthropogenic stressors with likely interactive effects, including synergisms in which the combined effects of multiple stressors are greater than the sum of individual effects. Early life stages of marine organisms are potentially vulnerable to the stressors associated with global change, but identifying general patterns across studies, species and response variables is challenging. This review represents the first meta-analysis of multi-stressor studies to target early marine life stages (embryo to larvae), particularly between temperature, salinity and pH as these are the best studied. Knowledge gaps in research on multiple abiotic stressors and early life stages are also identified. The meta-analysis yielded several key results: 1) Synergistic interactions (65% of individual tests) are more common than additive (17%) or antagonistic (17%) interactions. 2) Larvae are generally more vulnerable than embryos to thermal and pH stress. 3) Survival is more likely than sub-lethal responses to be affected by thermal, salinity, and pH stress. 4) Interaction types vary among stressors, ontogenetic stages, and biological responses, but they are more consistent among phyla. 5) Ocean acidification is a greater stressor for calcifying than non-calcifying larvae. Although more ecologically realistic than single-factor studies, multifactorial studies may still oversimplify complex systems, and so meta-analyses of the data from them must be cautiously interpreted with regard to extrapolation to field conditions. Nonetheless our results identify taxa with early life stages that may be particularly vulnerable (e.g. molluscs, echinoderms) or robust (e.g. arthropods, cnidarians) to abiotic stress. We provide a list of recommendations for future multiple stressor studies, particularly those focussed on early marine life stages.
Effects of increased pCO2 levels on the nematocyst densities in the symbiotic sea anemone Anthopleura elegantissima
Published 17 November 2014 Science ClosedTags: biological response, cnidaria, laboratory, morphology, North Atlantic, performance
The temperate sea anemone Anthopleura elegantissima participates in a facultative symbiosis with two genera of unicellular photosynthetic algae. Under stressful conditions such as increased levels of pCO2, anemones expel their algal symbionts causing the anemones to rely more heavily upon heterotrophic feeding. A heavier reliance on heterotrophic feeding could be accomplished by increasing the density of nematocysts. Anthopleura elegantissima individuals were collected from the Friday Harbor Laboratories shoreline (48° 32.7646 N, 123° 00.5932 W), Washington in June 2014, and the number of nematocyst per μg of protein was measured to determine if increasing oceanic pCO2 levels will affect the density of nematocysts. The number of nematocyst per μg of protein was measured again after 7 days in higher (2200 μatm) or ambient (700 μatm) pCO2 conditions. There was no difference in the density of nematocysts between individuals kept in different pCO2 levels.
Polyp flats, a new system for experimenting with jellyfish polyps, with insights into the effects of ocean acidification
Published 23 June 2014 Science ClosedTags: biological response, cnidaria, laboratory, methods, morphology
Research interest on jellyfish has grown exponentially over the last years and studies focusing on the biology and ecology of the jellyfish polyp stage are being recognized as crucial in understanding jellyfish proliferations. Due to the difficulty of conducting in situ work with jellyfish polyps, laboratory experiments are the most used approach. Here, we describe the design and successful testing of a new system that allows continuous seawater renewal while keeping constant the selected physicochemical conditions of the water throughout the experiment in contrast to closed systems used previously. As a first test, we started an experiment to assess the effects of ocean acidification on the growth and development of jellyfish polyps of Aurelia sp. This new design demonstrated high precision in maintaining constant conditions (pH, temperature, and flow rates) among the replicates of each treatment, and ensured excellent conditions for jellyfish polyp survival. All together it has shown to be an effective platform to assess the effect of environmental variables on the growth and development of jellyfish polyps.
Consequences of ecological, evolutionary and biogeochemical uncertainty for coral reef responses to climatic stress
Published 26 May 2014 Science ClosedTags: algae, biological response, BRcommunity, cnidaria, communitymodeling, corals, fish, modeling, multiple factors, review, temperature
Coral reefs are highly sensitive to the stress associated with greenhouse gas emissions, in particular ocean warming and acidification. While experiments show negative responses of most reef organisms to ocean warming, some autotrophs benefit from ocean acidification. Yet, we are uncertain of the response of coral reefs as systems. We begin by reviewing sources of uncertainty and complexity including the translation of physiological effects into demographic processes, indirect ecological interactions among species, the ability of coral reefs to modify their own chemistry, adaptation and trans-generational plasticity. We then incorporate these uncertainties into two simple qualitative models of a coral reef system under climate change. Some sources of uncertainty are far more problematic than others. Climate change is predicted to have an unambiguous negative effect on corals that is robust to several sources of uncertainty but sensitive to the degree of biogeochemical coupling between benthos and seawater. Macroalgal, zoanthid, and herbivorous fish populations are generally predicted to increase, but the ambiguity (confidence) of such predictions are sensitive to the source of uncertainty. For example, reversing the effect of climate-related stress on macroalgae from being positive to negative had no influence on system behaviour. By contrast, the system was highly sensitive to a change in the stress upon herbivorous fishes. Minor changes in competitive interactions had profound impacts on system behaviour, implying that the outcomes of mesocosm studies could be highly sensitive to the choice of taxa. We use our analysis to identify new hypotheses and suggest that the effects of climatic stress on coral reefs provide an exceptional opportunity to test emerging theories of ecological inheritance.
The photo-physiological response of a model cnidarian–dinoflagellate symbiosis to CO2-induced acidification at the cellular level
Published 29 April 2014 Science ClosedTags: abundance, biological response, cnidaria, laboratory, otherprocess, photosynthesis, primary production, protists, respiration
We measured the relationship between CO2-induced seawater acidification, photo-physiological performance and intracellular pH (pHi) in a model cnidarian–dinoflagellate symbiosis – the sea anemone Aiptasia sp. – under ambient (289.94 ± 12.54 μatm), intermediate (687.40 ± 25.10 μatm) and high (1459.92 ± 65.51 μatm) CO2 conditions. These treatments represented current CO2 levels, in addition to CO2 stabilisation scenarios IV and VI provided by the Intergovernmental Panel on Climate Change (IPCC). Anemones were exposed to each treatment for two months and sampled at regular intervals. At each time-point we measured a series of physiological responses: maximum dark-adapted fluorescent yield of PSII (Fv/Fm), gross photosynthetic rate, respiration rate, symbiont population density, and light-adapted pHi of both the dinoflagellate symbiont and isolated host anemone cell. We observed increases in all but one photo-physiological parameter (Pgross:R ratio). At the cellular level, increases in light-adapted symbiont pHi were observed under both intermediate and high CO2 treatments, relative to control conditions (pHi 7.35 and 7.46 versus pHi 7.25, respectively). The response of light-adapted host pHi was more complex, however, with no change observed under the intermediate CO2 treatment, but a 0.3 pH-unit increase under the high CO2 treatment (pHi 7.19 and 7.48, respectively). This difference is likely a result of a disproportionate increase in photosynthesis relative to respiration at the higher CO2 concentration. Our results suggest that, rather than causing cellular acidosis, the addition of CO2 will enhance photosynthetic performance, enabling both the symbiont and host cell to withstand predicted ocean acidification scenarios.
Settlement pattern of Posidonia oceanica epibionts along a gradient of ocean acidification: an approach with mimics
Published 24 March 2014 Science ClosedTags: abundance, algae, annelids, biological response, BRcommunity, bryozoa, chordata, cnidaria, community composition, crustaceans, field, Mediterranean, morphology, otherprocess, phanerogams, reproduction
Effects of ocean acidification (OA on the colonization/settlement pattern of the epibiont community of the leaves and rhizomesof the Mediterranean seagrass,Posidoniaoceanica, have been studied at volcanic CO2vents off Ischia (Italy), using “mimics”as artificial substrates. The experiments were conducted in shallowPosidoniastands (2-3 m depth), in three stations on the northand three on the south sides of the study area, distributed along a pH gradient. At each station, 4 rhizome mimics and 6 artificialleaves were collected every three months (Sept 2009-Sept 2010). The epibionts on both leaf and rhizome mimics showed clearchanges along the pH gradient; coralline algae and calcareous invertebrates (bryozoans, serpulid polychaetes and barnacles) weredominant at control stations but progressively disappeared at the most acidified stations. In these extremely low pH sites theassemblage was dominated by filamentous algae and non calcareous taxa such as hydroids and tunicates. Settlement pattern onthe artificial leaves and rhizome mimics over time showed a consistent distribution pattern along the pH gradient and highlightedthe peak of recruitment of the various organisms in different periods according to their life history.Posidoniamimics at theacidified station showed a poor and very simplified assemblage where calcifying epibionts seemed less competitive for space. Thisprofound difference in epiphyte communities in low pH conditions suggests cascading effects on the food web of the meadow and,consequently, on the functioning of the system.
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Increasing pCO2 correlates with low concentrations of intracellular dimethylsulfoniopropionate in the sea anemone Anemonia viridis
Published 29 January 2014 Science ClosedTags: abundance, biogeochemistry, biological response, chemistry, cnidaria, field, Mediterranean, physiology, protists
Marine anthozoans maintain a mutualistic symbiosis with dinoflagellates that are prolific producers of the algal secondary metabolite dimethylsulfoniopropionate (DMSP), the precursor of the climate-cooling trace gas dimethyl sulfide (DMS). Surprisingly, little is known about the physiological role of DMSP in anthozoans and the environmental factors that regulate its production. Here, we assessed the potential functional role of DMSP as an antioxidant and determined how future increases in seawater pCO2 may affect DMSP concentrations in the anemone Anemonia viridis along a natural pCO2 gradient at the island of Vulcano, Italy. There was no significant difference in zooxanthellae genotype and characteristics (density of zooxanthellae, and chlorophyll a) as well as protein concentrations between anemones from three stations along the gradient, V1 (3232 μatm CO2), V2 (682 μatm) and control (463 μatm), which indicated that A. viridis can acclimate to various seawater pCO2. In contrast, DMSP concentrations in anemones from stations V1 (33.23 ± 8.30 fmol cell−1) and V2 (34.78 ± 8.69 fmol cell−1) were about 35% lower than concentrations in tentacles from the control station (51.85 ± 12.96 fmol cell−1). Furthermore, low tissue concentrations of DMSP coincided with low activities of the antioxidant enzyme superoxide dismutase (SOD). Superoxide dismutase activity for both host (7.84 ± 1.37 U·mg−1 protein) and zooxanthellae (2.84 ± 0.41 U·mg−1 protein) at V1 was 40% lower than at the control station (host: 13.19 ± 1.42; zooxanthellae: 4.72 ± 0.57 U·mg−1 protein). Our results provide insight into coastal DMSP production under predicted environmental change and support the function of DMSP as an antioxidant in symbiotic anthozoans.
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Sea water acidification affects osmotic swelling, regulatory volume decrease and discharge in nematocytes of the jellyfish Pelagia noctiluca
Published 30 December 2013 Science ClosedTags: biological response, cnidaria, laboratory, Mediterranean, performance, physiology
Background: Increased acidification/PCO2 of sea water is a threat to the environment and affects the homeostasis of marine animals. In this study, the effect of sea water pH changes on the osmotic phase (OP), regulatory volume decrease (RVD) and discharge of the jellyfish Pelagia noctiluca (Cnidaria, Scyphozoa) nematocytes, collected from the Strait of Messina (Italy), was assessed. Methods: Isolated nematocytes, suspended in artificial sea water (ASW) with pH 7.65, 6.5 and 4.5, were exposed to hyposmotic ASW of the same pH values and their osmotic response and RVD measured optically in a special flow through chamber. Nematocyte discharge was analyzed in situ in ASW at all three pH values. Results: At normal pH (7.65), nematocytes subjected to hyposmotic shock first expanded osmotically and then regulated their cell volume within 15 min. Exposure to hyposmotic ASW pH 6.5 and 4.5 compromised the OP and reduced or totally abrogated the ensuing RVD, respectively. Acidic pH also significantly reduced the nematocyte discharge response. Conclusion: Data indicate that the homeostasis and function of Cnidarians may be altered by environmental changes such as sea water acidification, thereby validating their use as novel bioindicators for the quality of the marine environment.
Regulation of intracellular pH in cnidarians: response to acidosis in Anemonia viridis
Published 25 November 2013 Science ClosedTags: biological response, cnidaria, laboratory, physiology
The regulation of intracellular pH is a fundamental aspect of cell physiology that has received little attention in studies of the phylum Cnidaria, which includes ecologically important sea anemones and reef building corals. Like all organisms, cnidarians must maintain pH homeostasis to counterbalance reduction in intracellular pH, which can arise due to changes in either intrinsic or extrinsic parameters. Corals and sea anemones face natural daily changes in internal fluids where extracellular pH can range from 8.9 during the day to 7.4 at night. Furthermore, cnidarians are likely to experience future CO2-driven declines in seawater pH, a process known as ocean acidification. Here, we carried out the first mechanistic investigation to determine how cnidarian pHi responds to decreases in extracellular and intracellular pH. Using the anemone Anemonia viridis, we employed confocal live cell imaging and a pH-sensitive dye to track the dynamics of pHi after intracellular acidosis induced by acute exposure to decreases in seawater pH and NH4Cl prepulses. The investigation was conducted on cells that contained intracellular symbiotic algae (Symbiodinium sp.) and on symbiont-free endoderm cells. Experiments using inhibitors and sodium-free seawater indicate a potential role of Na+/H+ plasma membrane exchangers (NHE) in mediating pHi recovery following intracellular acidosis in both cell types. We also measured the buffering capacity of cells and obtained values between 20.8 and 43.8 mM/pH unit, comparable with other invertebrates. Our findings provide the first steps towards a better comprehension of acid-base regulation in these basal metazoans, for which information on cell physiology is extremely limited.
Irukandji jellyfish polyps exhibit tolerance to interacting climate change stressors
Published 30 October 2013 Science ClosedTags: biological response, cnidaria, laboratory, morphology, multiple factors, reproduction, South Pacific, temperature
Increasing ocean temperatures and strengthening boundary currents have caused the poleward migration of many marine species. Cubozoan jellyfish known to cause Irukandji syndrome have historically been confined to tropical waters but may be expanding into subtropical regions. Here, we examine the interactive effects of warming and acidification on the population dynamics of polyps of an Irukandji jellyfish, Alatina nr mordens, and the formation of statoliths in newly metamorphosed medusae, to determine if this jellyfish could tolerate future conditions predicted for southeast Queensland (SEQ), Australia. Two experiments, examining the orthogonal factors of temperature and pH, were undertaken. Experiment 1 mimicked the current, ca. 2050 and ca. 2100 summer temperature and pH conditions predicted for SEQ using A1F1 scenarios (temperature: 25, 27, 29 °C; pH: 7.9, 7.8, 7.6) and Experiment 2 mimicked current and future winter conditions (18 and 22 °C, pH 7.9, 7.8, 7.6). All polyps in Experiment 1 survived and budded. Fewer polyps budded in the lower pH treatments; however, patterns varied slightly among temperature treatments. Statoliths at pH 7.6 were 24% narrower than those at pH 7.8 and 7.9. Most polyps survived the winter conditions mimicked by Experiment 2 but only polyps in the 22 °C, pH 7.9 treatment increased significantly. The current absence of A. nr mordens medusae in SEQ, despite the polyps’ ability to tolerate the current temperature and pH conditions, suggests that ecological, rather than abiotic factors currently limit their distribution. Observations that budding was lower under low pH treatments suggest that rates of asexual reproduction will likely be much slower in the future. We consider that A. nr mordens polyps are likely to tolerate future conditions but are unlikely to thrive in the long term. However, if polyps can overcome potential ecological boundaries and acidification proceeds slowly A. nr mordens could expand polewards in the short term.
Physiological plasticity preserves the metabolic relationship of the intertidal non-calcifying anthozoan-Symbiodinium symbiosis under ocean acidification
Published 28 October 2013 Science ClosedTags: abundance, biological response, cnidaria, laboratory, North Atlantic, photosynthesis, physiology, phytoplankton, respiration
Ocean acidification (OA) is predicted to have profound effects on the physiological performance of marine organisms. Intertidal organisms may be better able to cope with future OA scenarios, as they tend to exhibit high levels of physiological plasticity and already experience pH levels predicted to occur with future OA. Here we investigated the physiological plastic responses and performance under OA conditions (pH 7.7, 7.4 and 6.8) of an intertidal non-calcifying anthozoan-Symbiodinium symbiosis, using the snakelocks sea anemone Anemonia viridis. We focussed on Symbiodinium productivity as this is the primary physiological feature of the symbiosis in terms of the shared metabolic relationship. Following a reduction in sea water pH to 7.4, Symbiodinium density decreased. However, Symbiodiniumproductivity significantly increased, which may have triggered their expulsion by the anemone. There was also a significant increase in Symbiodinium chlorophyll content which maintained normal anemone chlorophyll levels. As a result, the photosynthetic capacity of the symbiosis was preserved. This along with the unaffected anemone respiration rates indicated that the metabolic relationship was also preserved. Our work has shown that the physiological performance of an intertidal non-calcifying anthozoan-Symbiodinium symbiosis was maintained under OA conditions, due to the fact that both symbionts exhibited high levels of physiological plasticity. It is suggested that physiological plasticity could be an important mechanism enabling sea anemones to be successful in a future high CO2 world.
Future reef decalcification under a business-as-usual CO2 emission scenario
Published 9 September 2013 Science ClosedTags: abundance, algae, biological response, calcification, cnidaria, community composition, corals, crustaceans, echinoderms, field, fish, laboratory, mesocosms, mollusks, mortality, multiple factors, porifera, primary production, prokaryotes, temperature
Increasing atmospheric partial pressure of CO2 (pCO2) is a major threat to coral reefs, but some argue that the threat is mitigated by factors such as the variability in the response of coral calcification to acidification, differences in bleaching susceptibility, and the potential for rapid adaptation to anthropogenic warming. However the evidence for these mitigating factors tends to involve experimental studies on corals, as opposed to coral reefs, and rarely includes the influence of multiple variables (e.g., temperature and acidification) within regimes that include diurnal and seasonal variability. Here, we demonstrate that the inclusion of all these factors results in the decalcification of patch-reefs under business-as-usual scenarios and reduced, although positive, calcification under reduced-emission scenarios. Primary productivity was found to remain constant across all scenarios, despite significant bleaching and coral mortality under both future scenarios. Daylight calcification decreased and nocturnal decalcification increased sharply from the preindustrial and control conditions to the future scenarios of low (reduced emissions) and high (business-as-usual) increases in pCO2. These changes coincided with deeply negative carbonate budgets, a shift toward smaller carbonate sediments, and an increase in the abundance of sediment microbes under the business-as-usual emission scenario. Experimental coral reefs demonstrated highest net calcification rates and lowest rates of coral mortality under preindustrial conditions, suggesting that reef processes may not have been able to keep pace with the relatively minor environmental changes that have occurred during the last century. Taken together, our results have serious implications for the future of coral reefs under business-as-usual environmental changes projected for the coming decades and century.
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Distribution of benthic marine invertebrates at northern latitudes ― an evaluation applying multi-algorithm species distribution models
Published 20 June 2013 Science ClosedTags: annelids, biological response, chemistry, cnidaria, crustaceans, field, multiple factors, North Atlantic
Different techniques of species distribution modeling were applied to evaluate the distribution of eight benthic marine species in Icelandic waters. The species examined were Symplectoscyphus tricuspidatus, Stegopoma plicatile (both Hydrozoa), Prionospio cirrifera, Amphicteis gunneri (both Polychaeta), Desmosoma strombergi, Eurycope producta (both Isopoda), Andaniella pectinata and Harpinia crenulata (both Amphipoda). Information on 13 environmental variables (temperature mean, temperature mean SD, temperature minimum, temperature maximum, salinity mean, salinity mean SD, oxygen content, particulate organic carbon, seasonal variation index, bottom roughness, sediment thickness, acidification) and records of occurrences of these eight species was collated in an ArcGIS project. Modeling methods applied were MARS, TreeNet, and MaxENT. According to Area under the receiver operating curve (AUC) model assessment values, models with moderate to outstanding discriminatory power were found for all species. There was a good overlap in the overall pattern of prediction for most species independent on the modeling technique. Among the three applied techniques MARS seemed to generalize most whereas TreeNet predictions very precisely reflected information from the training data set. The distribution of the selected benthic invertebrate species in Icelandic waters could be linked to a variety of environmental factors related to oceanography, seabed topography and human impact. Their multivariate interactions acted as a structuring force of species distribution, instead of just their one by one individual influence. The selected predictors varied between the different models for the same species. They substituted each other in different models. The expected distribution of the examined species was mapped for a seascape of known environmental settings. Such maps will serve as excellent references in future impact studies and enable the detection of changes in the distribution of benthic marine invertebrates.
Effects of acidified seawater on asexual reproduction and statolith in the scyphozoan Chrysaora colorata
Published 15 January 2013 Science ClosedTags: biological response, cnidaria, laboratory, North Pacific, reproduction
Absorption of anthropogenic atmospheric CO2 into the ocean surface is causing ocean acidification and chemistry changes that reduce calcification in organisms that form calcium carbonate skeletons and shells. Increased acidity also affects aspects of life history other than calcification, such as sexual reproduction and recruitment. Studies of scyphozoan jellyfish abundance have not reached a consensus on the effects of ocean acidification on jellyfish populations, and few laboratory studies have looked at the effects of acidified seawater on jellyfish biology. This study examined the effect of acidity on the benthic and early pelagic stages of the scyphozoan Chrysaora colorata and the formation of a calcium sulfate sensory structure, the statolith. Researchers who model future ocean surface pH levels predict a drop of 0.3-0.5 units from pre-industrial levels by 2100 if fossil fuel consumption continues at its current rate. To understand how these conditions will affect C. colorata, treatments of acidified seawater (pH = 7.85, 7.75, 7.65, and 7.55) and a control (pH = 7.97) were used to test the effects of ocean acidification on asexual reproduction (number of podocysts formed, number of new polyps formed, number of days to begin strobilation, duration of strobilation, number of healthy ephyrae released, and percentage of ephyrae that were healthy) and statolith size. There was no effect of acidity on asexual reproduction in C. colorata, but there was a significant negative effect of acidity on statolith size—this supports previous research on the scyphozoan Aurelia labiata. This study suggests that C. colorata will be able to survive and asexually reproduce from the polyp stage through the ephyra stage in near-future ocean conditions. Previous studies have shown that a lack of statoliths results in swimming abnormalities, but the effect of smaller statoliths is unknown. To fully understand how C. colorata will be affected by ocean acidification, further research needs to be conducted on other stages of the lifecycle. C. colorata and other scyphozoans play important roles in their ecosystems, and if their abundance is negatively affected then their predators, prey, and competitors will be affected as well. However, it is possible that the effects of ocean acidification on C. colorata and other scyphozoans will be subtle and that they could benefit from declines in the abundance of predators and competitors that are more sensitive to the chemistry changes of ocean acidification.
Changes in microbial communities associated with the sea anemone Anemonia viridis in a natural pH gradient
Published 2 October 2012 Science ClosedTags: abundance, biological response, cnidaria, community composition, field, Mediterranean, physiology, prokaryotes
Ocean acidification, resulting from rising atmospheric carbon dioxide concentrations, is a pervasive stressor that can affect many marine organisms and their symbionts. Studies which examine the host physiology and microbial communities have shown a variety of responses to the ocean acidification process. Recently, several studies were conducted based on field experiments, which take place in natural CO(2) vents, exposing the host to natural environmental conditions of varying pH. This study examines the sea anemone Anemonia viridis which is found naturally along the pH gradient in Ischia, Italy, with an aim to characterize whether exposure to pH impacts the holobiont. The physiological parameters of A. viridis (Symbiodinium density, protein, and chlorophyll a+c concentration) and its microbial community were monitored. Although reduction in pH was seen to have had an impact on composition and diversity of associated microbial communities, no significant changes were observed in A. viridis physiology, and no microbial stress indicators (i.e., pathogens, antibacterial activity, etc.) were detected. In light of these results, it appears that elevated CO(2) does not have a negative influence on A. viridis that live naturally in the site. This suggests that natural long-term exposure and dynamic diverse microbial communities may contribute to the acclimation process of the host in a changing pH environment.
Benthic invertebrates in a high-CO2 world
Published 27 June 2012 Science ClosedTags: biological response, bryozoa, cnidaria, corals, crustaceans, echinoderms, mollusks, protists, review
Ocean acidification (OA), whereby increases in atmospheric carbon dioxide (cO2) over the past 200 years have led to a decline in the pH and carbonate ion availability of the oceans, has emerged as one of the major drivers of twenty- first century marine scientific research. Here we describe the current understanding of OA effects on benthic marine invertebrates, in particular the calcifiers thought to be most sensitive to altered carbonate chemistry. We describe the responses of benthic invertebrates to OA conditions predicted up to the end of the century, examining individual organism response through to ecosystem- level impacts. Research over the past decade has found great variability in the physiological and functional response of different species and communities to OA, with further variability evident between life stages. Over both geological and recent timescales, the presence and calcification rates of marine calcifiers have been inextricably linked to the carbon chemistry of the oceans. Under short-term experimentally enhanced cO2 conditions, many organisms have shown trade-offs in their physiological responses, such as reductions in calcification rate and reproductive output. In addition, carry-over effects from fertilization, larval and juvenile stages, such as enhanced development time and morphological changes, highlight the need for broad- scale studies over multiple life stages. These organism- level responses may propagate through to altered benthic communities under naturally enhanced cO2 conditions, evident in studies of upwelling regions and at shallow- water volcanic cO2 vents. Only by establishing which benthic invertebrates have the ability to acclimate or adapt, via natural selection, to changes from OA, in combination with other environmental stressors, can we begin to predict the consequences of future climate change for these communities.
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Sea anemones may thrive in a high CO2 world
Published 22 June 2012 Science ClosedTags: abundance, biological response, cnidaria, field, morphology, photosynthesis, respiration
Increased seawater pCO2, and in turn ‘ocean acidification’ (OA), is predicted to profoundly impact marine ecosystem diversity and function this century. Much research has already focussed on calcifying reef-forming corals (Class: Anthozoa) that appear particularly susceptible to OA via reduced net calcification. However, here we show that OA-like conditions can simultaneously enhance the ecological success of non-calcifying anthozoans, which play key ecological and biogeochemical roles in present day benthic ecosystems but also represent a model organism should calcifying anthozoans exist as less calcified (soft-bodied) forms in future oceans. Increased growth (abundance and size) of the sea anemone (Anemonia viridis) population was observed along a natural CO2 gradient at Vulcano, Italy. Both gross photosynthesis (PG) and respiration (R) increased with pCO2 indicating that the increased growth was, at least in part, fuelled by bottom up (CO2 stimulation) of metabolism. The increase of PG outweighed that of R and the genetic identity of the symbiotic microalgae (Symbiodinium spp.) remained unchanged (type A19) suggesting proximity to the vent site relieved CO2 limitation of the anemones’ symbiotic microalgal population. Our observations of enhanced productivity with pCO2, which are consistent with previous reports for some calcifying corals, convey an increase in fitness that may enable non-calcifying anthozoans to thrive in future environments, i.e. higher seawater pCO2. Understanding how CO2-enhanced productivity of non- (and less-) calcifying anthozoans applies more widely to tropical ecosystems is a priority where such organisms can dominate benthic ecosystems, in particular following localised anthropogenic stress.
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