Zooplankton is found in almost all major fresh and marine water bodies.Manyspecies, however, are restricted to specific territories depending on conditions of light, temperature, salinity, chemical composition, and turbulence. Their range also varies geographically and vertically within the water column.
The diversity of zooplankton makes classification difficult. Holoplanktonic zooplankton are freefloating their entire lives and are mostly invertebrates. Flagellated, ciliated, and amoeboid protozoa as well as several species from the animal phyla Cnidaria, Ctenophora, Chaetognatha, Mollusca, Annelida, Urochordata, Echinodermata, and Arthropoda make up the majority of collected organisms. Meroplanktonic zooplankton are the free-floating forms of organisms having swimming nekton or attached benthic stages as part of their life cycle. They consist mostly of egg and larval stages of marine benthic invertebrates that include worms, snails, clams, barnacles, crabs, starfish, and sea urchins, as well as many marine fish, such as tuna. Body forms, life cycles, diet, and location vary among species Zooplankton are often divided according to size. The most common divisions and sizes for zooplankton are nanoplankton (2 to 20 micrometers), microplankton (20 to 200 micrometers), mesoplankton (0.2 to 20 millimeters), macroplankton (2 to 20 centimeters), and megaplankton (20 to 200 centimeters). Although generally small, even jellyfish several meters in size are considered zooplankton because they are unable to swim effectively against the current. Copepods are one of the most studied forms and are classified as holoplanktonic zooplankton. Copepods have a segmented body with three distinct sections. Several pairs of legs and large antennae are used to create feeding currents that capture phytoplankton, especially diatoms, and other small zooplankton. Copepods are classified as mesoplankton and are nearly five millimeters in size. They are the most important herbivore in the ocean. Advanced collection techniques, however, have uncovered the presence of smaller zooplankton classifications that may be an important ecological first link.
Thanks for description - Animal life club