|Biotic Setting||Planktonic Biota
|Biotic Subclass||Crustacean Holoplankton
|Definition||Water parcels or layers in which zooplankton are perceived to be the dominant feature.
Zooplankton are heterotrophic biota of the water column; zooplankton drift with the
currents, but may (or may not) be able to move through the water under their own power.
Zooplankton may feed on phytoplankton, other zooplankton, or on detritus. CMECS classifies
zooplankton that may range in size from gigantic salp chains (strings of gelatinous
filter feeding tunicates that attain a length of 30 meters or more), to radiolarians
(minute, shelled amoebas). CMECS was not designed to be used for the smallest planktonic
forms (nanoplankton or picoplankton). CMECS Class Zooplankton includes both Holoplankton
(that live out their entire life histories in the plankton) and Meroplankton (that
are transient in the plankton). Meroplankton are typically larval stages that develop
into nekton or benthos as they mature. Meroplankton in general are difficult to identify;
specialized taxonomic knowledge and sets of regional keys are generally required.
Both Holoplankton and Meroplankton are quite diverse and include members of most marine
Aggregations of specific types of zooplankton (or of mixed zooplankton/phytoplankton communities) may occur in many forms. In general, an "Aggregation" is a relatively dense and homogeneous group of plankton that may be produced by rapid reproduction in-place under favorable conditions (by phytoplankton and holoplankton), by hydrodynamic forcing, by a common mass origin, by plankton motility (e.g., diurnal vertical migrations), by barriers to movement (e.g., pycnoclines), or by other phenomena. A Spawning Aggregation forms after a mass spawning event when synchronous spawning by many individuals produces large pulses of gametes and larvae. Classification of a Spawning Aggregation requires some evidence of recent mass spawning. Aggregations of all types may occur as amorphously shaped packets of water, may occur in layers at various depths, and may occur as diurnal migrations, among other forms.