# What is eutrophication?

VIDEO: What is eutrophication? Here's an overview in one minute. [Transcript](#transcript)

Eutrophication is a big word that describes a big problem in the nation's estuaries. [Harmful algal blooms](/hazards/hab/), [dead zones](/facts/deadzone.html), and fish kills are the results of a process called eutrophication — which occurs when the environment becomes enriched with nutrients, increasing the amount of plant and algae growth to [estuaries](/facts/estuary.html) and coastal waters.

Sixty-five percent of the estuaries and coastal waters in the [contiguous U.S.](#) that have been studied by researchers are moderately to severely degraded by excessive nutrient inputs. Excessive nutrients lead to algal blooms and low-oxygen (hypoxic) waters that can kill fish and seagrass and reduce essential fish habitats. Many of these estuaries also support [bivalve mollusk](/facts/bivalve.html) populations (e.g., oysters, clams, scallops), which naturally reduce nutrients through their filter-feeding activities.

Eutrophication sets off a chain reaction in the ecosystem, starting with an overabundance of algae and plants. The excess algae and plant matter eventually decompose, producing large amounts of carbon dioxide. This lowers the pH of seawater, a process known as [ocean acidification](/facts/acidification.html). Acidification slows the growth of fish and shellfish and can prevent shell formation in bivalve mollusks. This leads to a reduced catch for commercial and recreational fisheries, meaning smaller harvests and more expensive seafood.

##### **Did you know?**

_In September 2017, New York Governor Andrew M. Cuomo announced a $10.4 million effort to improve Long Island's water quality and bolster the economies and resiliency of coastal communities by restoring native shellfish populations to coastal waters. The state plans to establish five new sanctuary sites in Suffolk and Nassau Counties to transplant seeded clams and oysters, and to expand public shellfish hatcheries in the two counties through a dedicated grant program. Eutrophication has had significant economic impacts on Long Island Sound, where commercial shellfisheries have lost millions of dollars annually since 1985. Recent projections indicate that without intervention, the Sound could lose all of its [seagrass](https://www.fisheries.noaa.gov/feature-story/importance-eelgrass) beds by 2030, and that two-thirds of the Sound could lack enough oxygen for fish to survive._

In recent years, NOAA's [National Centers for Coastal Ocean Science](https://coastalscience.noaa.gov/) (NCCOS), in collaboration with NOAA's [Northeast Fisheries Science Center](https://www.nefsc.noaa.gov/nefsc/woodshole/), has enlisted estuaries' indigenous residents, namely, bivalve mollusks, to help slow and, in some cases, reverse the process of eutrophication, since they efficiently remove nutrients from the water as they feed on [phytoplankton](/facts/phyto.html) and detritus.

A groundbreaking modeling project in Long Island Sound showed that the oyster [aquaculture](/facts/aquaculture.html) industry in Connecticut provides $8.5 – $23 million annually in nutrient reduction benefits. The project also showed that reasonable expansion of oyster aquaculture could provide as much nutrient reduction as the comparable investment of $470 million in traditional nutrient-reduction measures, such as wastewater treatment improvements and agricultural best management practices.

The NOAA scientists used aquaculture modeling tools to demonstrate that shellfish aquaculture compares favorably to existing nutrient management strategies in terms of efficiency of nutrient removal and implementation cost. Documenting the water quality benefits provided by shellfish aquaculture has increased both communities' and regulators' acceptance of shellfish farming, not only in Connecticut but across the nation. In Chesapeake Bay, for example, nutrient removal policies include the harvesting of oyster tissue as an approved method, and in Mashpee Bay, Massachusetts, cultivation and harvest of oysters and clams are part of the official nutrient management plan.

### Video Transcript

What is Eutrophication? It’s a problem that should matter to you, whether you live near the ocean or not. That’s because it begins wherever people live and ends with damage to resources we all use and enjoy.It all starts when nutrients get into lakes and oceans. Remember, what’s waste to humans can be food to plants and other creatures. Nutrients feed algae, like they do other plants. Algae grows and blocks sunlight. Plants die without sunlight. Eventually, the algae dies too. Bacteria digest the dead plants, using up remaining oxygen, and giving off carbon dioxide. If they can’t swim away, fish and other wildlife become unhealthy, or die without oxygen. But it doesn’t have to be this way. Protecting marine resources starts with sound agricultural and waste management practices.

Did you know? - *In September 2017, New York Governor Andrew M. Cuomo announced a $10.4 million effort to improve Long Island's water quality and bolster the economies and resiliency of coastal communities by restoring native shellfish populations to coastal waters. The state plans to establish five new sanctuary sites in Suffolk and Nassau Counties to transplant seeded clams and oysters, and to expand public shellfish hatcheries in the two counties through a dedicated grant program. Eutrophication has had significant economic impacts on Long Island Sound, where commercial shellfisheries have lost millions of dollars annually since 1985. Recent projections indicate that without intervention, the Sound could lose all of its [seagrass](https://www.fisheries.noaa.gov/feature-story/importance-eelgrass) beds by 2030, and that two-thirds of the Sound could lack enough oxygen for fish to survive.*