Karenia brevis red tides and brevetoxin-contaminated fish: a high risk factor for Florida’s scavenging shorebirds?

Abstract

Shorebirds, including sanderlings ( Calidris alba ) and ruddy turnstones ( Arenaria interpres ), were observed scavenging beached fish, such as thread herring ( Opisthonema oglinum ), scaled sardine ( Harengula jaguana ) and mullet ( Mugil spp.) killed during a 2005 Karenia brevis red tide along the central west coast of Florida. Brevetoxin concentrations in dead fish tissues were analyzed to determine the potential exposure risk to scavenging shorebirds. This component of brevetoxin cycling in the food web has not previously been explored and the risks or benefits of this behavior for shorebirds are not currently understood. Toxin levels in freshly dead fish tissues ranged from 32 to 95,753 ng PbTx g -1 . Brevetoxins in shorebird livers were also confirmed (26–1313 ng PbTx g -1 ) in dead birds collected opportunistically from local beaches and rehabilitation centers during the red tide event, suggesting that brevetoxin exposure is a risk factor for mortality. These findings underscore the need to assess the ecological impacts of K. brevis blooms on Florida’s migratory and resident shorebird populations.