1 - An Introduction to Algal Ecology in Freshwater Benthic Habitats

Abstract

This chapter investigates algal ecology in freshwater benthic habitats. Algae are a highly diverse group of organisms that have important functions in aquatic habitats. Algae are an evolutionarily diverse group of photoautotrophic organisms with chlorophyll a and unicellular reproductive structures. By various taxonomic schemes, the number of algal divisions ranges from 4 to 13, with as many as 24 classes, and about 26,000 species. Benthic algae are those that live on or in association with substrata. Phytoplankton is a type of algae found suspended in the water column. An individual alga may be benthic or planktonic at one time or another, but many species are characteristically found in just one habitat. Most benthic algae in freshwater habitats are bluegreen algae (cyanophyta), green algae (chlorophyta), diatoms (bacillariophyta), or red algae (rhodophyta). However, most other divisions of algae can occur in freshwater benthic habitats. The chrysophyta, xanthophyta, cryptophyta, and pyrrophyta have many species that usually occur in the phytoplankton, but they may also occur in physiologically active forms in some benthic habitats. In addition, resting cells of many algae can be found in the benthos, which may have originated there or may have settled from the water column.