Mollusks

Mollusks

Mollusks are a varied group of soft-bodied animals, many of which have hard shells. They are essential to both marine ecosystems and human economies.

Species Role

Mollusks are invertebrates, and their body forms vary widely from clams and scallops, to snails and slugs, to octopus and squid. Not only are mollusks a highly diverse group of animals, they are also the basis of a number of major world fisheries and a large component of global marine aquaculture.

Mid-Atlantic Mollusk Fisheries

In the Mid-Atlantic, bivalve and cephalopod mollusks – clams, oysters, scallops, and squid – are among the largest and most valuable commercial fisheries. Bivalve clams and oysters are also the foundation of the majority of marine aquaculture produced in the Mid-Atlantic region.

Many mollusks have shells made of calcium carbonate, a material that can be vulnerable to low pH or acidified conditions. In a recent review of species sensitivity to changing climate, the shellfisheries of the Mid-Atlantic were identified as being at particularly high risk of negative impacts due to both acidification and sea water temperature increases.

Photo: Kristen Jabanoski/Atlantic Sea Scallops

Acidification Threats to Bivalve Larvae

The larval stages of bivalves are especially sensitive to changes in pH and alkalinity, because their shells are thin, newly developing, and made of a highly soluble form of calcium carbonate called aragonite, which could dissolve easily at lower pH.

Low pH and undersaturation of calcium carbonate can easily dissolve thin aragonite shells and have been shown in laboratory experiments to lead to reduced survival and growth for bivalve larvae. In the Pacific and Northeast, calcium carbonate undersaturation has negatively impacted shellfish hatchery production, leading to regional and national economic impacts.

Photo: NOAA Fisheries/Eastern Oyster

Challenges of Acidification for Bivalves

Research suggests that later life stages of bivalves, like juvenile clams and oysters, may still be susceptible to OA. The sensitivity of bivalves to OA is highly variable among species and life stages. Further research is required to understand how OA interacts with impacts from other environmental conditions like increasing temperature and decreasing salinity, which are expected to occur due to climate change.

Nonetheless, the sensitivity of larval and young juvenile bivalves has important consequences in terms of population size and reproducibility of these economically and ecologically important species.

Photo: Mark Dixon NOAA Fisheries/Oysters

Shellfish and Coastal Resilience

Bivalve shellfish are filter-feeders (remove particles and compounds from water) and important coastal ecosystem builders (create habitat for other species), and are often the focus of restoration and ecosystem resilience planning. To effectively implement coastal resilience or restoration priorities that include shellfish, it is imperative to better understand the ways that future acidified conditions will interact with these species throughout their life cycle.

Photo: Mark Dixon NOAA Fisheries/Surf Clam

References

Barton, A, Hales, B, Waldbusser, GG, Langdon, C, and Feely, RA. 2012. The Pacific oyster, Crassostrea gigas, shows negative correlation to naturally elevated carbon dioxide levels: Implications for near-term ocean acidification effects. Limnology and Oceanography 57(3): 698–710. https://doi.org/10.4319/lo.2012.57.3.0698

Clements, JC, Woodard, KD, and Hunt, HL. 2016. Porewater acidification alters the burrowing behavior and post-settlement dispersal of juvenile soft-shell clams (Mya arenaria). Journal of Experimental Marine Biology and Ecology, 477: 103-111. https://doi.org/10.1016/j.jembe.2016.01.013

Gazeau, F, Parker, LM, Comeau, S, Gattuso, JP, O’Connor, WA, Martin, S, Pörtner, HO, and Ross, PM. 2013. Impacts of ocean acidification on marine shelled molluscs. Marine Biology. 160: 2207-2245. https://doi.org/10.1007/s00227-013-2219-3

Gobler, CJ, et al. 2014. Hypoxia and Acidification Have Additive and Synergistic Negative Effects on the Growth, Survival, and Metamorphosis of Early Life Stage Bivalves. PLoS ONE. 9(1): e83648. https://doi.org/10.1371/journal.pone.0083648

Green, MA, Waldbusser, GG, Hubazc, L, Cathcart, E, and Hall, J. 2013. Carbonate mineral saturation state as a recruitment cue for settling bivalves in marine muds. Estuaries and Coasts 36(1): 18-27. https://doi.org/10.1007/s12237-012-9549-0

Miller, AW, Reynolds, AC, Sobrino, C, and Riedel, GF. 2009. Shellfish face uncertain future in high CO2 world: influence of acidification on oyster larvae calcification and growth in estuaries. PLoS ONE, 4(5), e5661. https://doi.org/10.1371/journal.pone.0005661

Ruesink, JL, van Raay, K, Witt, A, Herrold, S, Freshley, N, Sarich, A, and Trimble, AC. 2014. Spatio-Temporal Recruitment Variability of Naturalized Manila Clams (Ruditapes philippinarum) in Willapa Bay, Washington, USA. Fisheries Research 151: 199-204. http://dx.doi.org/10.1016/j.fishres.2013.11.011

Talmage, SC and Gobler, CJ. 2010. Effects of past, present, and future ocean carbon dioxide concentrations on the growth and survival of larval shellfish. Proceedings of the National Academy of Sciences. 107: 17246–17251. https://doi.org/10.1073/pnas.0913804107

Waldbusser, GG, Bergschneider, H, and Green, MA. 2010. Size-dependent pH effect on calcification in post-larval hard clam Mercenaria spp. Marine Ecology Progress Series 417:171-182. https://doi.org/10.3354/meps08809

Waldbusser, GG, Voigt, EP, Bergschneider, H, Green, MA, and Newell, RI. 2011. Biocalcification in the eastern oyster (Crassostrea virginica) in relation to long-term trends in Chesapeake Bay pH. Estuaries and Coasts, 34(2): 221-231. https://doi.org/10.1007/s12237-010-9307-0

Waldbusser, GG, Hales, B, Langdon, CJ, Haley, BA, Schrader, P, Brunner, EL, Gray, M, Miller, C, and Gimenez, I. 2014. Saturation-state sensitivity of marine bivalve larvae to ocean acidification. Nature Climate Change, 5: 273–280. https://doi.org/10.1038/nclimate2479

Schwaner C, Barbosa M, Schwemmer TG, Pales Espinosa E, Allam B. Increased Food Resources Help Eastern Oyster Mitigate the Negative Impacts of Coastal Acidification. Animals. 2023 Mar 25;13(7):1161. https://doi.org/10.3390/ani13071161