Recent water quality issues led to slowed growth, increased morphological abnormalities, altered feeding behaviors, and mortality among bivalve larvae being reared at an East Coast shellfish hatchery. The potential toxin was identified as a polyunsaturated aldehyde (PUA) which belongs to a class of compounds known as oxylipins. Oxylipins are bioactive secondary metabolites produced by a variety of organisms including plants, mosses, fungi, and algae. They are derived from a number of fatty acid precursors via lipoxygenase-based pathways. Oxylipins have been well characterized in marine diatoms and several studies have documented the pathological impact they have on zooplankton grazers and other phytoplankton. In contrast, relatively few studies have examined the effect of oxylipins on marine bivalves.
In this study, larvae of two bivalve species, Crassostrea virginica and Mytilus edulis, were exposed to two polyunsaturated aldehydes, 2,4-decadienal and 2,4-heptadienal. During the experiment, larvae were reared in filtered seawater containing a non-diatom diet composed of a mixture of T-Isochrysis and Pavlova. Decadienal and heptadienal treatments were applied shortly after the larvae had progressed to the D-stage with subsets of larvae being reared at 6 different concentrations of each chemical. The effect of these two PUAs upon larval feeding, morphological development, growth, and survival were monitored over a period of five days post-exposure. While previous studies have examined the effects of PUAs on bivalve hemocyte cell cultures, this is the first to investigate the range of concentrations over which these toxins impact larval bivalves.