Meeting Abstract

7.3  Sunday, Jan. 4  Effects of Karenia brevis Harmful Algal Blooms on Nearshore Fish Communities in Southwest Florida GANNON, D.P.*; BERENS, E.J.; CAMILLERI, S.A.; GANNON, J.G.; BRUEGGEN, M.K.; BARLEYCORN, A.B.; PALUBOK, V.I.; KIRKPATRICK, G.J.; WELLS, R.S.; Bowdoin College; Mote Marine Laboratory; Mote Marine Laboratory; Mote Marine Laboratory; University of Missouri-Columbia; Chicago Zoological Society; Mote Marine Laboratory; Mote Marine Laboratory; Chicago Zoological Society dgannon@bowdoin.edu

Blooms of the toxic alga, Karenia brevis, cause massive fish kills on Florida’s Gulf Coast. The ecological effects of K. brevis on nearshore fish communities are poorly known. We surveyed fishes in five habitats of Sarasota Bay and the adjacent Gulf of Mexico during four summers using a purse seine. We collected synoptic data on K. brevis cell densities, temperature, salinity, dissolved oxygen, and turbidity. Catch per unit effort and species richness were significantly lower in all habitats during blooms. Shannon-Weaver diversity indices were significantly lower in four of five habitats during blooms. Classification and regression tree analysis showed significant negative relationships between K. brevis density and non-clupeid CPUE, and between K. brevis density and species richness. Canonical correspondence analysis indicated that K. brevis affected fish community structure. Most trophic guilds were negatively associated with K. brevis density, whereas the guild including clupeids was positively associated. We concluded that red tides caused the observed changes in fish abundance and community structure. Harmful algal blooms occur throughout the world and may play an important, yet little-understood, role in regulating fish communities.