Abstract: 10200 A. Introduction

1. Introduction

Plankton are microscopic aquatic life forms with little or no ability to resist current movement and, thus, live free-floating (suspended) in natural waters. This section covers both phytoplankton and zooplankton. Phytoplankton are microscopic algae that occur in unicellular, colonial, or filamentous forms. Most are photosynthetic and eaten by zooplankton or other filter-feeding aquatic organisms. Freshwater zooplankton principally consist of protozoans, rotifers, cladocerans, and copepods, whereas marine water zooplankton are more diverse. Other planktonic microscopic aquatic organisms are discussed elsewhere. Zoosporic fungi are in Section 9610 F; aquatic hyphomycetes in Section 9610 G; and bacteria in Part 9000.