dead pelican

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A pelican killed by domoic acid. (T. Work)

dead loons

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Emaciated loons that washed ashore in North Carolina. (P. Spitzer)


Seabirds feed on the abundant life associated with the oceans and estuaries and thus are susceptible to the effects of HABs. In 1991 more than 100 pelicans and cormorants were found dead or suffering from unusual neurological symptoms in Monterey Bay, California. This event was attributed to a bloom of the diatom, Pseudo-nitzschia australis, which produce the toxin domoic acid. The toxin was transmitted to the seabirds via Northern anchovies. Anchovies are also consumed by marine mammals, several species of finfish, and are occasionally eaten by humans.

Likewise, these emaciated loons (bottom right) that were washed ashore in North Carolina may have been victims of algal toxins in their food. Exposures that are not initially lethal may still cause mortality in wildfowl,both during and after stresses such as migration. However, since ecosystem impacts are difficult to document, their true extent or significance is not known.

Inland birds are also affected by HABs.  Freshwater cyanobacterial blooms have been implicated as the cause of mass mortalities of birds.  Freshwater HABs are an expanding global problem and occur in nearly every state in the U.S.

Last updated: February 25, 2016