The term "plankton" refers to those microscopic aquatic forms having little or no resistance to currents and living free-floating and suspended in natural waters, such as planktonic plants, "phytoplankton", and planktonic animals, "zooplankton". Discussed in this section are sampling collection, including specific instructions for gathering samples; concentration techniques; guidelines for preparing slide mounts for various types of plankton; discussion of various types of microscopes and calibration. Counting techniques are given for phytoplankton (10200F) and zooplankton (10200G). Five methods for determining chlorophyll are given in 10200H. Various methods of estimating or determining biomass are given in 10200I. Metabolic rate measurements are discussed in 10200J.