|Biotic Setting||Planktonic Biota
|Biotic Subclass||Chrysophyte Phytoplankton
|Definition||This class includes areas of floating or suspended microscopic algae that are capable
of photosynthesis. Although some species are motile, they are generally passively
transported by water movements. Under certain conditions, they can form aggregations,
large blooms or colonies.
The spatial and temporal expressions of phytoplankton are described as three types in CMECS. (1) Aggregations are detectable concentrations of one or more species within a defined volume or area. Aggregations form when conditions are sufficient for growth of phytoplankton and are typically represented as mixed aggregations, but often with a single species or group predominating. (2) Blooms are defined as rapid growth and multiplication of single species to high density in an area of surface waters within a short period of time (days), often to the exclusion of other species. Blooms are often considered to be harmful to the ecology of the system and may represent an imbalance of conditions. (3) Phytoplankton maxima layers are expressed as defined layers of one or more species, often with one group predominating, that form at depth within the water column, whose thickness is small relative to its areal extent. Maxima layers generally occur in response to presence of optimal conditions, such as salinity and temperature or the supply of a limiting resource, such as nutrients, for growth along an interface.