December 8, 2015

PLANKTON: Holoplankton & Meroplankton

This group includes both microscopic plants like Algae (phytoplankton) and animals like crustaceans and protozoans (zooplankton) found in all aquatic ecosystems, except certain swift moving waters.

The locomotory power of the planktons is limited so that their distribution is controlled, largely, by currents in the aquatic ecosystems.

Based on the length of life cycle / planktonic mode of life, they are grouped as:

Holoplankton (or) Permanent plankton: These organisms that are planktonic for their entire life cycle. Examples: radiolarians, foraminiferans, amphipods, krills, copepods, salps, and jellyfishes (except porifera, bryozoa, phoronida, prochordata and mammalia).

Meroplankton (or) Temporary plankton: These organisms that are planktonic for only a part of their life cycle, usually the egg and larval stages. Examples: the larvae of echinoderms, crustaceans, marine worms, and most fish.

After a period of time in the plankton, meroplankton either graduates to the nekton or adopt a benthic (often sessile) lifestyle on the seafloor.

While the former ones are distributed throughout the year, the latter forms are only seasonal in occurrence and are generally found distributed in shallow-neritic waters and in mangroves. The growth rate, productivity and species diversity of plankton in tropical waters especially in mangrove waters are high. The zooplankton community is represented by heterogeneous groups of organisms of varying size and belonging to different phyla of animal kingdom.


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