Increasingly acidic zone from land-based nutrient pollution found in Chesapeake Bay

  • Zone of water 30 feet below surface is increasing in acidity, threatening shellfish

August 28, 2017 University of Delaware

…The team analyzed little studied factors that play a role in ocean acidification (OA) — changes in water chemistry that threaten the ability of shellfish such as oysters, clams and scallops to create and maintain their shells, among other impacts.

…”This study shows for the first time that the oxidation of hydrogen sulfide and ammonia from the bottom waters could be a major contributor to lower pH in coastal oceans and may lead to more rapid acidification in coastal waters compared to the open ocean,” said Cai, the paper’s lead author and an expert in marine chemistry and carbon’s movement through coastal waters.

in the coastal ocean, in general, there is a synergistic effect on OA when excess nutrients introduced into the ecosystem from land cause plant overgrowth, a process known as eutrophication that upsets the water’s natural chemistry and causes the death of marine species. When that organic matter sinks to the bottom sediment it is consumed by bacteria that respire, creating excess carbon dioxide that mixes upward into the water column.

The water is already lower in pH and when you add just a little more carbon dioxide and other acids, it creates a tipping point that leads to a decrease in pH” said Cai….

[Compared to Gulf of Mexico] the combined environmental and climate change stressors make the Bay more vulnerable, and the excess nutrients and increase in acidity may take a larger toll….

Wei-Jun Cai, et al. Redox reactions and weak buffering capacity lead to acidification in the Chesapeake Bay. Nature Communications, 2017; 8 (1) DOI: 10.1038/s41467-017-00417-7