HORIZONS How to assess toxin ingestion and post- ingestion partitioning in zooplankton?

Algal toxins can have severe impacts on marine and aquatic ecosystems and often bioaccumulate through the food chain. One of the major obstacles facing research in this area is the lack of standardized and realistic techniques with which to probe algal–grazer interactions. Here we present a synopsis on current and innovative techniques which can be used to monitor the ambient concentration and fate of algal toxins in grazers and determine their eventual target within the grazers’ tissues. We focus on a newly recognized class of oxylipin toxins (volatile polyunsaturated aldehydes and oxo-acids), which have been identified from lipid-rich microalgae. While some workers have reported that these biotoxins have negative effects on fecundity and recruitment of metazoan grazers, this mechanism is currently under debate as a result of conflicting evidence. We argue that the use of a variety of non-standard and often invalid or unrealistic assays has confounded our ability to scrutinize this mechanism systematically.