Ocean acidification is often referred to as the evil twin of climate change and it is one of the greatest threats to marine ecosystems. Especially vulnerable are coastal waters and estuaries, so-called nurseries of the sea. New research published in PLoS ONE is the first to show ocean acidification’s “multi-stressor” impact on bivalve larvae.
Rising carbon levels are once again the culprit, lowering the pH of surface ocean waters by about 0.1 pH units says the US National Ocean and Atmospheric (NOAA). That seemingly small change translates into an approximately 30 percent increase in acidity says the NOAA.
Process of ocean acidification. Image source: NOAA
What follows is a cascade of changing ocean chemistry that is particularly challenging to marine calcifiers—corals, bivalves, and other marine organisms that make shells or skeletons. The widely reported bleaching of coral is one example. Increased acidity is a double-edged sword, both corroding marine shells and skeletons and disrupting the availability of essential minerals in the water.
Oyster hatcheries in the US Northwest served as an unwelcome harbinger when they saw an approximately 80% drop in oyster “seed” or larvae due to mass die off as reported in several outlets including Yale Environment 360. Scientists at Oregon State University College of Earth, Ocean, and Atmospheric Sciences are trying to understand “the mechanisms of failure” in bivalve larvae which have shown to be highly sensitive to ocean acidification.
They looked at how specific factors – changes in pH, the concentration of carbon dioxide and the availability of calcium carbonate minerals, the building blocks of the shells – affected shell growth, feeding and respiration of mussel (Mytilus californianus and M. galloprovincialis) embryo and larvae.
“In marine bivalves, other earlier studies have either directly or indirectly shown a saturation state sensitivity, however our current study is the first to show differential sensitivity of different physiological processes to different carbonate system parameters on the same species,” say the study authors.
This is just one more clue on the impact of changing ocean chemistry on marine ecosystems. To find out more about the impact of ocean acidity on bivalves check out this video by study author George Waldbusser, Assistant Professor, Oregon State University.
Kimberly Hatfield