Using artificial substrates to quantify Gambierdiscus and other toxic benthic dinoflagellates for monitoring purposes

Collecting methods generally used to determine cell abundances of toxic benthic dinoflagellates (BHAB) use cells dislodged from either macrophytes or artificial substrates. This article compares the advantages of the macrophyte and artificial substrate methods and discusses which method is more appropriate for use in monitoring programs that focus on toxic BHAB species identification and quantification. The concept of benthic dinoflagellate "preference" for specific macrophytes was also reviewed. Examination of data from 75 field studies showed macrophytes with higher surface area per unit biomass harbored higher concentrations of Gambierdiscus cells. There was no definitive evidence that cells were actively selecting one macrophyte over another. This observation supports the use of artificial substrates (AS) as a means of assessing cell abundances in complex habitats because cell counts are normalized to a standardized surface area, not macrophyte biomass. The artificial substrate method represents the most robust approach, currently available, for collecting toxic, benthic dinoflagellates for a cell-based early warning system.