Lack of colour is an adaptation of life in photic zone :planktons and transparancy of zooplanktons reduce their visibility in pelagic zone thus reduce the chance of being discoversd by predators.;
Blue colour of neuston to reduce the predation from sea birds.
Some zooplanktons are red & silver colour ;silver colour produces mirror like reflection.
Red colour is strong absorber to blue green light thus make diffult for predator to form a sharp immage in bioluminescent light.
Many fishes use counter shading colour pattern in which the upper part of the body is dark makes difficult see them from above & lower part of the body is lighter so that predators look up towards the brightly lit surface can’t see them.
Many adapted to swim fast some meso plankton have cilia ;
Fishes having streamline body surface secretes slime & special ribbing of skin to reduce the drag.
Tuna like fishes have lunate tail & retractable finlets to increase the swimming speed & ther mussels are well developed for it.
Vertical migration of zooplankton diurnally during the day they move down wards to avoid predation by pelagic fish & at night they move to surface .
Bacteria , phytoplankton ,zooplankton, benthic invertebrates & fish .
Generally blue /greenish ;
Dinoflagelate , ctenophora, copepods , medusa may produce light but some bacteria luminesce constantly.
Function is startle or blind predators .predators man scared / confused by flash of light.
Other defensive adaptations
Small size & transparency of planktons is most common to avoid detection by predators.
Schooling is a common adaptation of fishes (makeral) & zooplanktons this behavior of forming large schools may confuse predators.
Largebody size : some can contain large amount of water in their tissues :puffer fish.
Grow spines : Foraminiference &Radiolariana.
Some use toxins :skin of the parrot fish has toxins.
Squids use several ways:
Ink ejection : they eject cloud of ink and become hidden while escape.
Jet propelsion: propel spray of water on predator to escape.
Colour change .