Em biologia marinha e limnologia chama-se fitoplâncton ao conjunto dos organismos aquáticos microscópicos que têm capacidade fotossintética e que vivem dispersos flutuando na coluna de água
O fitoplâncton também pode ser responsável por alguns problemas ecológicos quando se desenvolve demasiadamente:
Numa situação de excesso de nutrientes e de temperatura favorável, estes organismos podem multiplicar-se rapidamente formando o que se costuma chamar "florescimento" ou bloom (palavra inglesa que é mais usada).
Nesta situação, a água fica esverdeada mas rapidamente, de um a dois dias, dependendo da temperatura, se torna acastanhada, quando o plâncton esgota os nutrientes e começa a morrer.
Nessa altura, a decomposição mais ou menos rápida dos organismos mortos pode levar ao esgotamento do oxigênio na água e, como consequência, à morte em massa de peixes e outros organismos.
Fonte: http://pt.wikipedia....topl%C3%A2ncton
Para ilustrar, junto esta imagem obtida através do site da ESA (Agencia Espacial Europeia) sobre o mar de Barents no norte da Europa:
Do site da ESA:
The phytoplankton bloom pictured in this Envisat image stretches across the Barents Sea off the coast of mainland Europe’s most northern point, Cape Nordkinn.
The southern area of this deep shelf sea – with an average depth of 230 m – remains mostly ice-free due to the warm North Atlantic Drift.
This contributes to its high biological production compared to other oceans of similar latitude.
Free-floating phytoplankton highlight the whirls of ocean currents in spectacular shades of blue and green. These microscopic marine organisms that drift on or near the surface of oceans and seas have been called 'the grass of the sea' because they are the foundation of the oceanic food chain.
The simple organisms also play a similar role to terrestrial 'green' plants in the photosynthetic process. Phytoplankton are able to convert inorganic compounds such as water, nitrogen and carbon into complex organic materials.
With their ability to 'digest' these compounds, they are credited with removing as much carbon dioxide from the atmosphere as their 'cousins' on land – therefore having a profound influence on climate.
They are also sensitive to environmental changes, so it is important to monitor and model phytoplankton into calculations of future climate change.
Although most types of phytoplankton are individually microscopic, the chlorophyll they use for photosynthesis collectively tints the colour of the surrounding ocean waters.
This allows for these tiny organisms to be detected from space with dedicated 'ocean colour' sensors, such as Envisat's Medium Resolution Imaging Spectrometer, which acquired this image on 17 August 2011.
