Eutrophication is a big word that describes a big problem in the nation’s estuaries. Harmful algal blooms, dead zones, and fish kills are the results of a process called eutrophication-which begins with the increased load of nutrients to estuaries and coastal waters. The primary culprits in eutrophication appear to be excess nitrogen and phosphorus—from sources including fertilizer runoff and septic system effluent to atmospheric fallout from burning fossil fuels—which enter water bodies and fuel the overgrowth of algae, which, in turn, reduces water quality and degrades estuarine and coastal ecosystems. Eutrophication can also produce carbon dioxide, which lowers the PH of seawater (ocean acidification). This slows the growth of fish and shellfish, may prevent shell formation in bivalve mollusks, and reduces the catch of commercial and recreational fisheries, leading to smaller harvests and more expensive seafood.

Source: Environment by Shankar IAS