Off-Flavors and Harmful Algae

Abstract

Phytoplankton are an essential part of the microbial community of most aquaculture ponds and the role of algae in oxygen budgets and nutrient cycling has been stressed throughout this book. Quite frequently, however, phytoplankton becomes a nuisance in pond aquaculture. The most common problems are related to excessive total biomass, and most efforts at managing phytoplankton in ponds are directed at the control of overall abundance (see Section 10.8), with little regard to the taxonomic structure of the community. On the other hand, there are times when a particular species of phytoplankton can become a problem, even when overall algal biomass is low. For example, some species of algae produce odorous metabolites that confer undesirable flavors to aquatic animals. Other species produce potent toxins that may either kill the animal under culture or accumulate in its tissues so that the product is toxic to human consumers. Development of off-flavors and problems related to harmful algae are severe economic problems in some types of aquaculture. The purpose of this chapter is to summarize what is known about these problems and discuss management practices that may reduce their impact. At the outset, it should be mentioned that these problems have proven to be quite difficult to manage under commercial aquaculture conditions.