The Negative Effects of Ocean Acidification on the Physiology of Marine Animals and Fauna

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in relations to coral reefs. The article summarises how coral reefs are constructed and the many types of dissolutions that can happen, as well how ocean acidification and climate change influences the breakdown, export and dissolution of CaCO3 of coral communities. The review suggests that with an increase in ocean acidification bioerosion and CaCO3 dissolution on coral reefs will significantly increase as a response. Also with recent studies, though some coral reefs are relatively tolerant to ocean acidification this provides little relief as bioerosion and CaCO3 dissolution can exceed the growth of the coral reef.

This subjects touched within this review gave a good explanation on the chemical background on coral reefs and the processes of dissolution before discussing ocean acidification, allowing an easy understanding of the topic. 3.5/5

References

Andersson, A.J, Gledhill, Dwight (2013) Ocean Acidification and Coral reefs: Effects on Breakdown Dissolution, and Net Ecosystem Calcification. Annual Review of Marine Science 5: 321-348

Fernandez, PA, Roleda, MY, Hurd, CL (2015) Effects of ocean acidification on the photosynthetic performance, carbonic anhydrase activity and growth of the giant help Macrocytis pyrifera. Photosynth Res 124: 293-304

Sarmento, V.C, Souza, T.P, Esteves, A.M, Santos, P.J.P (2015) Effects of seawater acidification on coral reef meiofauna community. Coral reefs 34: 955-966

Taylor, JRA, Gilleard, JM, Allen, MC, Deheyn, DD (2015) Effects of CO2-induced pH reduction on exoskeleton structure and biophotonic properties of shrimp Lysmata californica. Sci Rep 5:10608 doi: 10.1038/srep10608

Wizemann, A, Meye, F.W, Hofmann, L.C, Wild, C, Westphal, H (2015) Ocean acidification alters the calcareous microstructure of the green macro-alga Halimeda opuntia. Coral reefs 34: 941-954

Abstract

Effects of CO2 induced pH reduction on the exoskeleton structure and biophotonic properties of the shrimp Lysmata californica

The anticipated effects of CO2-induced ocean acidification on marine calcifiers are generally negative, and include dissolution of calcified elements and reduced calcification rates. Such negative effects are not typical of crustaceans for which comparatively little ocean acidification research has been conducted. Crustaceans, however, depend on their calcified exoskeleton for many critical functions. Here, we conducted a short-term study on a common caridean shrimp, Lysmata californica, to determine the effect of CO2-driven reduction in seawater pH on exoskeleton growth, structure, and mineralization and animal cryptic coloration. Shrimp exposed to ambient (7.99 } 0.04) and reduced pH (7.53 } 0.06) for 21 days showed no differences in exoskeleton growth (percent increase in carapace length), but the calcium weight percent of their cuticle increased significantly in reduced pH conditions, resulting in a greater Ca:Mg ratio. Cuticle thickness did not change, indicating an increase in the mineral to matrix ratio, which may have mechanical consequences for exoskeleton function. Furthermore, there was a 5-fold decrease in animal transparency, but no change in overall shrimp coloration (red). These results suggest that even short-term exposure to CO2-induced pH reduction can significantly affect exoskeleton mineralization and shrimp biophotonics, with potential impacts on crypsis, physical defense, and predator avoidance.

Effects of ocean acidification on the photosynthetic performance, carbonic anhydrase activity and growth of the giant help Macrocytis pyrifera

Under ocean acidification (OA), the 200 % increase in CO2(aq) and the reduction of pH by 0.3–0.4 units are predicted to affect the carbon physiology and growth of macroalgae. Here we examined how the physiology of the giant kelp Macrocystis pyrifera is affected by elevated pCO2/low pH. Growth and photosynthetic rates, external and internal carbonic anhydrase (CA) activity, HCO3 - versus CO2 use were determined over a 7-day incubation at ambient pCO2 400 latm/pH 8.00 and a future OA treatment of pCO2 1200 latm/pH 7.59. Neither the photosynthetic nor growth rates were changed by elevated CO2 supply in the OA treatment. These results were explained by the greater use of HCO3- compared to CO2 as an inorganic carbon (Ci) source to support photosynthesis. Macrocystis is a mixed HCO3- and CO2 user that exhibits two effective mechanisms for HCO3 - utilization; as predicted for species that possess carbon-concentrating mechanisms (CCMs), photosynthesis was not substantially affected by elevated pCO2. The internal CA activity was also unaffected by OA, and remained high and active throughout the experiment; this suggests that HCO3 - uptake via an anion exchange protein was not affected by OA. Our results suggest that photosynthetic Ci uptake and growth of Macrocystis will not be affected by elevated pCO2/low pH predicted for the future, but the combined effects with other environmental factors like temperature and nutrient availability could change the physiological response of Macrocystis to OA. Therefore, further studies will be important to elucidate how this species might respond to the global environmental change predicted for the ocean.

Effects of seawater acidification on coral reef meiofauna community

Despite the increasing risk that ocean acidification will modify benthic communities, great uncertainty remains about how this impact will affect the lower trophic levels, such as members of the meiofauna. A mesocosm experiment was conducted to investigate the effects of water acidification on a phytal meiofauna community from a coral reef. Community samples collected from the coral reef subtidal zone (Recife de Fora Municipal Marine Park, Porto Seguro, Bahia, Brazil), using artificial substrate units, were exposed to a control pH (ambient seawater) and to three levels of seawater acidification (pH reductions of 0.3, 0.6, and 0.9 units below ambient) and collected after 15 and 30 d. After 30 d of exposure, major changes in the structure of the meiofauna community were observed in response to reduced pH. The major meiofauna groups showed divergent responses to acidification. Harpacticoida and Polychaeta densities did not show significant differences due to pH. Nematoda, Ostracoda, Turbellaria, and Tardigrada exhibited their highest densities in low-pH treatments (especially at the pH reduction of 0.6 units, pH 7.5), while harpacticoid nauplii