What Are Plankton And Why Study Them

The term plankton refers to any small biota (from microns to centimetres) living in the water and drifting at the mercy of currents - ranging from bacteria to jellyfish. This definition is rather loose, as we often include jellyfish and krill (euphausids - and their larval forms) as plankton, yet they are active swimmers and are therefore technically referred to as 'nekton'. Sometimes even good swimmers, such as late-stage fish larvae are incorrectly termed 'planktonic', as they often show up...

Fixation and preservation of plankton

A fixative, such as formaldehyde, chemically treats the tissues stopping biochemical activity and increases the mechanical strength. A preservative, such as alcohol or salt, is a natural compound that reduces or stops decomposition without chemically fixing the tissue. Samples preserved in alcohol may shrink or become distorted more than in formaldehyde, but are safer and more pleasant to study, and are suitable for DNA analysis. Therefore the type and amount of fixative preservative used...

Jellyfish And Their Relatives

The jellyfish, or medusae, are treated separately here as they are increasingly common, and of great interest to humans because of their sting and as a fishery. Jellyfish belong to Phylum Cnidaria, which is divided into three classes Hydrozoa, Scyphozoa, and Cubozoa a fourth class of cnidarians contains all the benthic anemones and corals . They are distinguished from all other gelatinous zooplankton, and often from each other, by their stinging cells cnidocytes, nematocysts, Ostman 2000 . More...