Background | Ocean Acidification in New York State

What is ocean acidification?

Carbon dioxide – one of the culprits behind climate change – is changing ocean chemistry, due to increasing emissions from human activity. Carbon dioxide dissolved in water makes carbonic acid, and while the ocean will not get so acidic that it burns your skin, plants and animals that live in the water can feel the difference. In particular, animals that form hard calcium carbonate shells or skeletons, such as oysters and coral, have trouble growing and surviving when the pH gets lower, or more acidic.

Time series of carbon dioxide and ocean pH at Mauna Loa Observatory, Hawaii. The pH drops as CO2 from the atmosphere is added to the oceans, making the water more acidic. Shellfish growing in acidified water have smaller, weaker shells. (Figure adapted from NOAA).

Shellfish, corals and urchins are a few examples of marine animals that are expected to suffer from reduced growth and survival under ocean acidification. Scientific research is also showing that some fishes lose sensory function in acidified water, making it harder to detect predators, food, and suitable habitats. Here in the Northeast U.S., the shellfish that make up a multi-million dollar industry are threatened by acidification, as are the commercially valuable fishes that eat shellfish. And just like a bottle of soda stays fizzier in the refrigerator, colder seawater can hold more carbon dioxide, making acidification worse as you get further from the equator.

Reef-building corals and shellfish are just two of the organisms expected to suffer from ocean acidification, because the chemical changes in the water make it harder to build their calcium carbonate shells.

While the average pH of the global oceans gradually drops, coastal waters in bays and estuaries also experience regular fluctuations in pH due to natural and human influences, including the effects of pollution. Nutrients from wastewater and fertilizers enter our waterways through runoff and create dense algae blooms. The algae use up oxygen and replace it with carbon dioxide to acidify the water, and this can last for days, weeks, or even months in the most closed-in, polluted waters. Densely populated areas such as New York City and Long Island make significant contributions to this phenomenon, as do large farms that fertilize their soil or keep livestock. Even the fertilizer you put on your lawn can send nutrients seeping into the water.

Excess nutrient pollution causes algal blooms that remove oxygen and give off carbon dioxide, causing fish kills and local acidification events. Certain types of algal blooms, such as red tides, also make shellfish from the water toxic to humans.