Glossary:Eutrophication

eutrophication

process by which large additions of nutrients causes an overgrowth of algae and subsequent depletion of oxygen.

Word Class: noun

Pronunciation: eu·troph·i·ca·tion / yo͞oˌträfəˈkāSH(ə)n

Eutrophication in the Indian River Lagoon

Eutrophication is caused by excessive nitrogen and/or phosphorous polluting a water body, where it results in a dense growth of algae, followed by the death of animal life resulting from oxygen depletion. Sadly, in many subtropical estuaries such as the IRL, we have documented “phase shifts” from seagrass to macroalgae to toxic phytoplankton blooms and cascading impacts on the lagoon’s biota.

Phytoplankton are single-celled algae that thrive in the water column. Healthy estuaries produce “good” species of phytoplankton that turn sunlight into energy and in turn feed organisms such as oysters and important consumers, such as the forage fish called menhaden. Eutrophic, or, in the case of the IRL, hypereutrophic estuaries produce toxic phytoplankton, including those that cause brown and red tides, as well as cyanobacteria blooms. Their toxins reduce the growth of other phytoplankton, block sunlight to benthic plants, and release toxins into the water and air.

From Sewage on the Move by Dr. Peter Barile, Senior Scientist at Marine Research & Consulting Inc.