Periphyton Community Analyses
The phytoplankton community
consists of free-living algae which are suspended in the water column. It is
most important in standing water systems such as lakes and ponds. Because algae
are primary producers and form the base of the food web, higher organisms depend
on them for food and for the oxygen released during the process of
photosynthesis. These tiny plants have an extremely high rate of reproduction;
therefore, in the presence of sufficient light and ample nutrients, their
populations can explode into blooms which can contribute to oxygen depletion,
fish kills, and aesthetic problems that can interfere with recreational use.
Problems in the phytoplankton populations are often the first indicators of
anthropogenic stress on a system.
The periphyton community is
made up of algae inhabiting the surfaces of underwater vegetation, rocks, and
other substrates. Due to the sedentary nature of periphyton, the community
composition, structure, and biomass are sensitive to changes in water quality
and are often used as indicators of ambient conditions.
Changes in the phytoplankton
(free-water) and periphyton (attached) algal communities can be particularly
useful as assessment tools, due to their rapid response to environmental stress.
Studies of algal, combined with macroinvertebrate communities, provide a
valuable assessment of the overall health of aquatic systems.
Measures of Algal
measurements of algal community health are routinely employed to determine
whether populations are disturbed. These are:
- Taxa richness: the number of
different types of organisms present in a system.
- Shannon-Weaver diversity: an
measures the distribution of organisms present. Low diversities represent
conditions where only a few organisms are abundant, to the exclusion of other
- Numbers of pollution
sensitive taxa: certain taxa are labeled as sensitive or tolerant to pollution,
based on the literature.
- Community structure:
measurements of shifts in proportions of major groups of organisms, compared to
- Algal biomass: the amount of
algal growth a body of water can support, measured as algal density or
- Habitat Assessment: quality
of the local environment with respect to the needs of the organisms
The Standard Operating
Procedures used in the collection and analysis of periphyton and phytoplankton
samples can be viewed or downloaded from the
Biology Section SOPs.