Bioluminescent Phytoplankton, Hong Kong, China

Certain creatures both on land and sea can produce light through chemical reactions taking place within their bodies known as Bioluminescence. The bioluminescence results from a light-producing chemical reaction also called chemiluminescence. Certain types of chemicals when mixed together produce energy which ‘excites’ other particles on vibration and generate light which causes the glow. The group of chemicals involved to make plankton glow are broadly termed luciferins and the light is produced by a series of oxidation reactions set off by a catalyst called luciferase. The bioluminescence in plankton is very high in several forms of Plankton and is a form of cold light or luminescence.
Phytoplankton
Phytoplankton are the autotrophic components of the plankton community and a key factor of oceans, seas and freshwater basins ecosystems. The name comes from the Greek words φυτόν (phyton), meaning "plant", and πλαγκτός (planktos), meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye. However, when present in high enough numbers, some varieties may be noticeable as a green discoloration of the water; this is due to the presence of chlorophyll within their cells, and in some species also due to the presence of accessory pigments such as phycobiliproteins, xanthophylls, etc.).