by Elizabeth Rodarte
Ocean acidification is the process in which the pH of the world’s oceans decreases due to the production of atmospheric CO2. The increase of CO2 and decrease in pH leads to changes in calcification, growth, and abundance of species such as coral reefs, mussels, seagrass, and macroalgae. Habitats experience the indirect effects of such CO2 increases. They must remain resistant to sudden changes in pH and CO2 in order to benefit the organisms they support. By modeling the effects of lowering pH in habitats with corals, mussels, seagrass, and microalgae, we can determine the costs to these species. Coral reefs and mussels are calcifying organisms that are negatively affected by the pH which limits survival and stunts, or even stops, growth and development. Lower pH decreases the species complexity of corals and mussels and ultimately the species richness in habitats. Mytilus mussels, for example, require specific pH to function. The species of mussels, other than Mytilus, that survive decreases in pH lack “structural complexity” to support dense surrounding vegetation. Therefore, the loss of Mytilus mussels due to ocean acidification allows for a more stable yet less diverse habitat.
Seagrass and macroalgae differ from coral reefs and mussels in that they benefit from ocean increases in CO2. These photosynthetic organisms increase their biomass and species richness along with decreases in pH. However, in terms of habitats, the increase in CO2 leads to a response of “competitive replacement” between species for spatial area. Thus, habitats also experience decreased species richness as species compete with each other for resources. This process takes longer to see than in coral reefs and mussel beds.
Different marine habitats experience a variety of consequences to ocean acidification. The positive side of the consequences of ocean acidification in different habitats allows for the study of “habitat recovery after disturbance.” Knowing that ocean acidification affects each habitat and species differently can better prepare us to treat habitats more efficiently.
Sunday, J.M., Fabricius, K.E., Kroeker, K.J., Anderson, K.M., Brown, N.E., Barry, J.P., et al., 2016. Ocean Acidification can Mediate Biodiversity Shifts by Changing Biogenic Habitat. Nature Climate Change 7.1, 81-85