Harmful dinoflagellate Cochlodinium polykrikoides impairs the feeding behavior of larval sheepshead minnows (Cyprinodon variegatus)

Research evaluating the toxicity of the harmful dinoflagellate Cochlodinium (a.k.a. Margalefidinium) polykrikoides has been dominated by acute bioassays while the sublethal effects remain less well understood. This study examined the sublethal effects of C. polykrikoides exposure on the feeding behavior of larval estuarine fish. Sheepshead minnow (Cyprinodon variegatus) larvae were used in feeding experiments which assessed the total consumption of zooplankton prey (i.e., Artemia nauplii) over defined time periods. Larvae exposed to intermediate concentrations (i.e., 10² cells ml⁻¹) of clonal cultures of C. polykrikoides saw statistically significant reductions (range = 10%–81%) in the Artemia consumed compared to controls (i.e., filtered seawater, culture media or nontoxin producing dinoflagellate). These reductions were found independent of whether the larvae were fed or starved prior to experimentation. As these concentrations are similar to those typically found during mild blooms or at the periphery of dense blooms, these findings have significant implications for the feeding behavior of ichthyoplankton.