Camp, E. F., Smith, D. J., Evenhuis, C., Enochs, I., Manzello, D., Woodcock, S., et al. (2016). Acclimatization to high-variance habitats does not enhance physiological tolerance of two key Caribbean corals to future temperature and pH. Proc. R. Soc. B, 283(1831), 20160442.
Abstract: Corals are acclimatized to populate dynamic habitats that neighbour coral reefs. Habitats such as seagrass beds exhibit broad diel changes in temperature and pH that routinely expose corals to conditions predicted for reefs over the next 50-100 years. However, whether such acclimatization effectively enhances physiological tolerance to, and hence provides refuge against, future climate scenarios remains unknown. Also, whether corals living in low-variance habitats can tolerate present-day high-variance conditions remains untested. We experimentally examined how pH and temperature predicted for the year 2100 affects the growth and physiology of two dominant Caribbean corals (Acropora palmata and Porites astreoides) native to habitats with intrinsically low (outer-reef terrace, LV) and/or high (neighbouring seagrass, HV) environmental variance. Under present-day temperature and pH, growth and metabolic rates (calcification, respiration and photosynthesis) were unchanged for HV versus LV populations. Superimposing future climate scenarios onto the HV and LV conditions did not result in any enhanced tolerance to colonies native to HV. Calcification rates were always lower for elevated temperature and/or reduced pH. Together, these results suggest that seagrass habitats may not serve as refugia against climate change if the magnitude of future temperature and pH changes is equivalent to neighbouring reef habitats.
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Campbell, J. E., & Fourqurean, J. W. (2018). Does Nutrient Availability Regulate Seagrass Response to Elevated CO2? Ecosystems, 21(7), 1269–1282.
Abstract: Future increases in oceanic carbon dioxide concentrations (CO2(aq)) may provide a benefit to submerged plants by alleviating photosynthetic carbon limitation. However, other environmental factors (for example, nutrient availability) may alter how seagrasses respond to CO2(aq) by regulating the supply of additional resources required to support growth. Thus, questions remain in regard to how other factors influence CO2(aq) effects on submerged vegetation. This study factorially manipulated CO2(aq) and nutrient availability, in situ, within a subtropical seagrass bed for 350 days, and examined treatment effects on leaf productivity, shoot density, above- and belowground biomass, nutrient content, carbohydrate storage, and sediment organic carbon (Corg). Clear, open-top chambers were used to replicate CO2(aq) forecasts for the year 2100, whereas nutrient availability was manipulated via sediment amendments of nitrogen (N) and phosphorus (P) fertilizer. We provide modest evidence of a CO2 effect, which increased seagrass aboveground biomass. CO2(aq) enrichment had no effect on nutrient content, carbohydrate storage, or sediment Corg content. Nutrient addition increased leaf productivity and leaf N content, however did not alter above- or belowground biomass, shoot density, carbohydrate storage, or Corg content. Treatment interactions were not significant, and thus NP availability did not influence seagrass responses to elevated CO2(aq). This study demonstrates that long-term carbon enrichment may alter the structure of shallow seagrass meadows, even in relatively nutrient-poor, oligotrophic systems.
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Cuyler, E. E., & Byrne, R. H. (2018). Spectrophotometric calibration procedures to enable calibration-free measurements of seawater calcium carbonate saturation states. Analytica Chimica Acta, 1020, 95–103.
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Davidson, T. M., Altieri, A. H., Ruiz, G. M., Torchin, M. E., & Navarrete, S. (2018). Bioerosion in a changing world: a conceptual framework. Ecol Lett, 21(3), 422–438.
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Dutra, E., Koch, M., Peach, K., & Manfrino, C. (2016). Tropical crustose coralline algal individual and community responses to elevated pCO(2) under high and low irradiance. ICES J. Mar. Sci., 73(3), 803–813.
Abstract: Crustose coralline algae (CCA) cement reefs and create important habitat and settling sites for reef organisms. The susceptibility of CCA to increasing ocean pCO(2) and declining pH or ocean acidification (OA) is a growing concern. Although CCA are autotrophs, there has been little focus on the interaction of elevated pCO(2) and irradiance. We examined elevated pCO(2) effects on individual CCA and macroalgal benthic communities at high and low irradiance (205 13 mol photons m(-2) s(-1)) in an aquaria experiment (35 d, June August 2014) on Little Cayman Island, Caribbean. A dominant Cayman reef wall CCA (Peyssonnelia sp.) in its adult lobed form and individual CCA recruits were used as experimental units. Changes in CCA, fleshy macroalgae (branching and turfs), and microalgae (including microbial biofilm) per cent cover and frequency were examined on macroalgal communities that settled onto plates from the reef. Reef diel cycles of pCO(2) and pH were simulated using seawater inflow from a back reef. Although CO2 enrichment to year 2100 levels resulted in 1087 mu atm pCO(2) in the elevated pCO(2) treatment, CaCO3 saturation states remained high (Omega(cal) >= 2.7). Under these conditions, elevated pCO(2) had no effect on Peyssonnelia sp. calcification rates or survival regardless of irradiance. Individual CCA surface area on the bottom of settling plates was lower under elevated pCO(2), but per cent cover or frequency within the community was unchanged. In contrast, there was a strong and consistent community assemblage response to irradiance. Microalgae increased at high irradiance and CCA increased under low irradiance with no significant pCO(2) interaction. Based on this short-term experiment, tropical macroalgal communities are unlikely to shift at pCO(2) levels predicted for year 2100 under high or low irradiance. Rather, irradiance and other factors that promote microalgae are likely to be strong drivers of tropical benthic algal community structure under climate change.
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Edmunds, P. J., & Burgess, S. C. (2016). Size-dependent physiological responses of the branching coral Pocillopora verrucosa to elevated temperature and P-CO2. J Exp Biol, 219(24), 3896–3906.
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Enochs, I. C., Manzello, D. P., Kolodziej, G., Noonan, S. H. C., Valentino, L., & Fabricius, K. E. (2016). Enhanced macroboring and depressed calcification drive net dissolution at high-CO[sub:2]coral reefs. Proc. R. Soc. B, 283(1842), 20161742.
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Enochs, I. C., Manzello, D. P., Wirshing, H. H., Carlton, R., & Serafy, J. (2016). Micro-CT analysis of the Caribbean octocoral Eunicea flexuosa subjected to elevated pCO(2). ICES J. Mar. Sci., 73(3), 910–919.
Abstract: Rising anthropogenic carbon dioxide has resulted in a drop in ocean pH, a phenomenon known as ocean acidification (OA). These acidified waters have many ramifications for diverse marine biota, especially those species which precipitate calcium carbonate skeletons. The permanence of coral reef ecosystems is therefore closely related to OA stress as habitat-forming corals will exhibit reduced calcification and growth. Relatively little is known concerning the fate of other constituent taxa which may either suffer concomitant declines or be competitively favoured in acidified waters. Here, we experimentally (49 d) test the effects of next century predictions for OA (pH = 7.75, pCO(2) = 1081 mu atm) vs. near-present-day conditions (pH = 8.01, pCO(2) = 498 mu atm) on the common Caribbean octocoral Eunicea flexuosa. We measure linear extension of this octocoral and use a novel technique, high-resolution micro-computed tomography, to measure potential differences in the morphology of calcified internal skeletal structures (sclerites) in a 2 mm apical section of each branch. Despite the use of highly accurate procedures, we found no significant differences between treatments in either the growth of E. flexuosa branches or the structure of their sclerites. Our results suggest a degree of resilience to OA stress and provide evidence that this octocoral species may persist on Caribbean coral reefs, despite global change.
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Gómez, C. E., Paul, V. J., Ritson-Williams, R., Muehllehner, N., Langdon, C., & Sánchez, J. A. (2014). Responses of the tropical gorgonian coral Eunicea fusca to ocean acidification conditions. Coral Reefs, .
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Gravinese, P. M., Enochs, I. C., Manzello, D. P., & van Woesik, R. (2018). Warming and pCO(2) effects on Florida stone crab larvae. Estuarine, Coastal and Shelf Science, 204, 193–201.
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Groner, M. L., Burge, C. A., Cox, R., Rivlin, N. D., Turner, M., Van Alstyne, K. L., et al. (2018). Oysters and eelgrass: potential partners in a high pCO2 ocean. Ecology, 99(8), 1802–1814.
Abstract: Climate change is affecting the health and physiology of marine organisms and altering species interactions. Ocean acidification (OA) threatens calcifying organisms such as the Pacific oyster, Crassostrea gigas. In contrast, seagrasses, such as the eelgrass Zostera marina, can benefit from the increase in available carbon for photosynthesis found at a lower seawater pH. Seagrasses can remove dissolved inorganic carbon from OA environments, creating local daytime pH refugia. Pacific oysters may improve the health of eelgrass by filtering out pathogens such as Labyrinthula zosterae (LZ), which causes eelgrass wasting disease (EWD). We examined how co-culture of eelgrass ramets and juvenile oysters affected the health and growth of eelgrass and the mass of oysters under different pCO2 exposures. In Phase I, each species was cultured alone or in co-culture at 12 degrees C across ambient, medium, and high pCO2 conditions, (656, 1,158 and 1,606 muatm pCO2 , respectively). Under high pCO2 , eelgrass grew faster and had less severe EWD (contracted in the field prior to the experiment). Co-culture with oysters also reduced the severity of EWD. While the presence of eelgrass decreased daytime pCO2 , this reduction was not substantial enough to ameliorate the negative impact of high pCO2 on oyster mass. In Phase II, eelgrass alone or oysters and eelgrass in co-culture were held at 15 degrees C under ambient and high pCO2 conditions, (488 and 2,013 muatm pCO2 , respectively). Half of the replicates were challenged with cultured LZ. Concentrations of defensive compounds in eelgrass (total phenolics and tannins), were altered by LZ exposure and pCO2 treatments. Greater pathogen loads and increased EWD severity were detected in LZ exposed eelgrass ramets; EWD severity was reduced at high relative to low pCO2 . Oyster presence did not influence pathogen load or EWD severity; high LZ concentrations in experimental treatments may have masked the effect of this treatment. Collectively, these results indicate that, when exposed to natural concentrations of LZ under high pCO2 conditions, eelgrass can benefit from co-culture with oysters. Further experimentation is necessary to quantify how oysters may benefit from co-culture with eelgrass, examine these interactions in the field and quantify context-dependency.
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Ingels, J., dos Santos, G., Hicks, N., Vazquez, Y. V., Neres, P. F., Pontes, L. P., et al. (2017). Short-term CO 2 exposure and temperature rise effects on metazoan meiofauna and free-living nematodes in sandy and muddy sediments: Results from a flume experiment. Journal of Experimental Marine Biology and Ecology, .
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Koch, M., Bowes, G., Ross, C., & Zhang, X. - H. (2013). Climate change and ocean acidification effects on seagrasses and marine macroalgae. Glob Change Biol, 19(1), 103–132.
Abstract: Although seagrasses and marine macroalgae (macro-autotrophs) play critical ecological roles in reef, lagoon, coastal and open-water ecosystems, their response to ocean acidification (OA) and climate change is not well understood. In this review, we examine marine macro-autotroph biochemistry and physiology relevant to their response to elevated dissolved inorganic carbon [DIC], carbon dioxide [CO2], and lower carbonate [CO32-] and pH. We also explore the effects of increasing temperature under climate change and the interactions of elevated temperature and [CO2]. Finally, recommendations are made for future research based on this synthesis. A literature review of >100 species revealed that marine macro-autotroph photosynthesis is overwhelmingly C3 (= 85%) with most species capable of utilizing HCO3-; however, most are not saturated at current ocean [DIC]. These results, and the presence of CO2-only users, lead us to conclude that photosynthetic and growth rates of marine macro-autotrophs are likely to increase under elevated [CO2] similar to terrestrial C3 species. In the tropics, many species live close to their thermal limits and will have to up-regulate stress-response systems to tolerate sublethal temperature exposures with climate change, whereas elevated [CO2] effects on thermal acclimation are unknown. Fundamental linkages between elevated [CO2] and temperature on photorespiration, enzyme systems, carbohydrate production, and calcification dictate the need to consider these two parameters simultaneously. Relevant to calcifiers, elevated [CO2] lowers net calcification and this effect is amplified by high temperature. Although the mechanisms are not clear, OA likely disrupts diffusion and transport systems of H+ and DIC. These fluxes control micro-environments that promote calcification over dissolution and may be more important than CaCO3 mineralogy in predicting macroalgal responses to OA. Calcareous macroalgae are highly vulnerable to OA, and it is likely that fleshy macroalgae will dominate in a higher CO2 ocean; therefore, it is critical to elucidate the research gaps identified in this review.
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McCoy, S. J., & Kamenos, N. A. (2018). Coralline algal skeletal mineralogy affects grazer impacts. Glob Chang Biol, 24(20), 4775–4783.
Abstract: In macroalgal-dominated systems, herbivory is a major driver in controlling ecosystem structure. However, the role of altered plant-herbivore interactions and effects of changes to trophic control under global change are poorly understood. This is because both macroalgae and grazers themselves may be affected by global change, making changes in plant-herbivore interactions hard to predict. Coralline algae lay down a calcium carbonate skeleton, which serves as protection from grazing and is preserved in archival samples. Here, we compare grazing damage and intensity to coralline algae in situ over 4 decades characterized by changing seawater acidity. While grazing intensity, herbivore abundance and identity remained constant over time, grazing wound width increased together with Mg content of the skeleton and variability in its mineral organization. In one species, decreases in skeletal organization were found concurrent with deeper skeletal damage by grazers over time since the 1980s. Thus, in a future characterized by acidification, we suggest coralline algae may be more prone to grazing damage, mediated by effects of variability between individuals and species.
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McCoy, S. J., Kamenos, N. A., Chung, P., Wootton, T. J., & Pfister, C. A. (2018). A mineralogical record of ocean change: Decadal and centennial patterns in the California mussel. Global Change Biology, .
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McCoy, S. J., Allesina, S., & Pfister, C. A. (2016). Ocean acidification affects competition for space: projections of community structure using cellular automata. Proc. R. Soc. B, 283(1826), 20152561.
Abstract: Historical ecological datasets from a coastal marine community of crustose coralline algae (CCA) enabled the documentation of ecological changes in this community over 30 years in the Northeast Pacific. Data on competitive interactions obtained from field surveys showed concordance between the 1980s and 2013, yet also revealed a reduction in how strongly species interact. Here, we extend these empirical findings with a cellular automaton model to forecast ecological dynamics. Our model suggests the emergence of a new dominant competitor in a global change scenario, with a reduced role of herbivory pressure, or trophic control, in regulating competition among CCA. Ocean acidification, due to its energetic demands, may now instead play this role in mediating competitive interactions and thereby promote species diversity within this guild.
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Okazaki, R. R., Towle, E. K., van Hooidonk, R., Mor, C., Winter, R. N., Piggot, A. M., et al. (2017). Species-specific responses to climate change and community composition determine future calcification rates of Florida Keys reefs. Glob Change Biol, 23(3), 1023–1035.
Abstract: Anthropogenic climate change compromises reef growth as a result of increasing temperatures and ocean acidification. Scleractinian corals vary in their sensitivity to these variables, suggesting species composition will influence how reef communities respond to future climate change. Because data are lacking for many species, most studies that model future reef growth rely on uniform scleractinian calcification sensitivities to temperature and ocean acidification. To address this knowledge gap, calcification of twelve common and understudied Caribbean coral species was measured for two months under crossed temperatures (27, 30.3 °C) and CO2 partial pressures (pCO2) (400, 900, 1300 μatm). Mixed-effects models of calcification for each species were then used to project community-level scleractinian calcification using Florida Keys reef composition data and IPCC AR5 ensemble climate model data. Three of the four most abundant species, Orbicella faveolata, Montastraea cavernosa, and Porites astreoides, had negative calcification responses to both elevated temperature and pCO2. In the business-as-usual CO2 emissions scenario, reefs with high abundances of these species had projected end-of-century declines in scleractinian calcification of >50% relative to present-day rates. Siderastrea siderea, the other most common species, was insensitive to both temperature and pCO2 within the levels tested here. Reefs dominated by this species had the most stable end-of-century growth. Under more optimistic scenarios of reduced CO2 emissions, calcification rates throughout the Florida Keys declined <20% by 2100. Under the most extreme emissions scenario, projected declines were highly variable among reefs, ranging 10�100%. Without considering bleaching, reef growth will likely decline on most reefs, especially where resistant species like S. siderea are not already dominant. This study demonstrates how species composition influences reef community responses to climate change and how reduced CO2 emissions can limit future declines in reef calcification.
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Pfister, C. A., Roy, K., Wootton, J. T., McCoy, S. J., Paine, R. T., Suchanek, T. H., et al. (2016). Historical baselines and the future of shell calcification for a foundation species in a changing ocean. Proc. R. Soc. B, 283(1832), 20160392.
Abstract: Seawater pH and the availability of carbonate ions are decreasing due to anthropogenic carbon dioxide emissions, posing challenges for calcifying marine species. Marine mussels are of particular concern given their role as foundation species worldwide. Here, we document shell growth and calcification patterns in Mytilus californianus, the California mussel, over millennial and decadal scales. By comparing shell thickness across the largest modern shells, the largest mussels collected in the 1960s-1970s and shells from two Native American midden sites (similar to 1000-2420 years BP), we found that modern shells are thinner overall, thinner per age category and thinner per unit length. Thus, the largest individuals of this species are calcifying less now than in the past. Comparisons of shell thickness in smaller individuals over the past 10-40 years, however, do not show significant shell thinning. Given our sampling strategy, these results are unlikely to simply reflect within-site variability or preservation effects. Review of environmental and biotic drivers known to affect shell calcification suggests declining ocean pH as a likely explanation for the observed shell thinning. Further future decreases in shell thickness could have significant negative impacts on M. californianus survival and, in turn, negatively impact the species-rich complex that occupies mussel beds.
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Robbins,, & Lisle,. (2018). Regional Acidification Trends in Florida Shellfish Estuaries: a 20+ Year Look at pH, Oxygen, Temperature, and Salinity. Estuaries and Coasts, 41(5), 1268–1281.
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Towle, E., Baker, A., & Langdon, C. (2016). Preconditioning to high CO2 exacerbates the response of the Caribbean branching coral Porites porites to high temperature stress. Mar. Ecol. Prog. Ser., 546, 75–84.
Abstract: Climate change stress on coral reefs occurs as a result of increased temperature and ocean acidification. However, these stressors do not act uniformly: acidification is a ‘press’ disturbance characterized by chronic increases in CO2, whereas thermal stress is a ‘pulse’ disturbance characterized by acute episodes of anomalously warm temperatures. Therefore future episodes of thermal stress will develop within the context of pre-existing acidification. Many studies have investigated the effect of combined temperature and CO2 on corals, but no study has yet investigated whether pre-exposing corals to elevated CO2 affects their response to high temperature. We investigated this for the first time using replicate fragments of the Caribbean coral Porites porites preconditioned to either 390 ppm or 900 ppm CO2 at 26°C for 3 mo. After this period, half of the corals from each CO2 level were exposed to 31°C (i.e. 31°C/390 ppm or 31°C/900 ppm) for 2 mo, while the other half were maintained in their original treatments (26°C/390 ppm or 26°C/900 ppm). Calcification, feeding rate, and photochemical efficiency were measured. Corals preconditioned to high CO2 before thermal stress (i.e. 31°C/900 ppm) showed 44% lower calcification rates than the control group, but single stress treatment groups did not experience significant growth reductions. Feeding rates increased for corals exposed to either high CO2 or high temperature singularly, but not when thermal stress was applied following CO2 preconditioning. Photochemical efficiency decreased by 25% for all treatment groups compared to the control. Together, these data suggest that preconditioning to elevated CO2 worsens holobiont response to thermal stress, potentially exacerbating the effects of climate change stressors on coral reefs.
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