Ocean Acidification: Indirect Effects on Coastal Marine Biodiversity
By Musa Jundi
The majority of coastal marine life depends on habitat-forming organisms like coral and sea vegetation for things like food, protection from the motion of water, and protection from predators. An article in Nature Climate Change by an international group of researchers find that the consequences of ocean acidification may affect biodiversity indirectly by altering these biogenic habitats. As atmospheric carbon dioxide concentrations rise, the oceans experience rising acidity as the carbon dioxide is absorbed by the water. While the negative physiological effects of acidification on marine organisms have been well-documented as direct causes of biodiversity loss in marine ecosystems, the indirect impact of habitat change has not been studied as extensively.
The findings in the article detail the effects of declining ocean pH and increased carbonate saturation, both caused by rising CO2 levels in the atmosphere, on the structural complexity of four distinct biogenic habitats around the globe: coral reefs, mussel beds, seagrass meadows, and macroalgae. As pH declined, a decrease in habitat complexity was observed in both the coral reefs and mussel beds. However, complexity rose in seagrass meadows and macroalgae. It is generally understood that as habitat complexity increases, so does species richness. Habitat-forming organisms are integral to their delicate ecosystems, and disturbances to their functions can possibly have much greater impacts at the community level. The falling pH, and its relationship with biodiversity, will likely depend on whether the acidification increases or decreases habitat complexity in the area (e.g. macroalgae vs. coral reefs).
More research is needed to fully understand the potential effects and impact that these shifts in biogenic habitat complexity may have on marine ecosystems and biodiversity. While the direct impact of ocean acidification on marine organisms has been studied extensively and is relatively easy to predict, this indirect impact has been largely overlooked and remains very difficult to accurately predict.
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