Phytoplankton encompassed all microscopic algae which drift with currents or float on water surface of an ocean, rivers, lakes and other water bodies. Phytoplankton plays a major role as the basis of the aquatic food web, providing essential ecological function of all aquatic life. The many kind of phytoplankton are classified into many different classes, families, genera and species of both marine and freshwater. Phytoplankton has a rapid responds to environmental changes, and hence their occurrence, species composition and diversity are widely used as biological indicator of the quality of the water conditions.
The main environmental concerns are the occurrence of cultural eutrophication and harmful algal blooms. Cultural eutrophication is caused by excessive nutrient inputs mainly human activities (domestic and industrial effluent) which lead to the proliferation of phytoplankton. The undesirable environmental conditions will indirectly influence the community structure in the aquatic ecosystem.
Under certain environmental conditions phytoplankton can experience elevated growth rates and attained high densities which lead to algal bloom. Some are natural events as part of annual phytoplankton cycle, meanwhile some blooms can have negative impact on the ecological system and aquaculture industry and are termed ‘Harmful Algae Bloom’ (HAB). Many regions of the world implement phytoplankton monitoring program to protect their aquaculture industry.
The Water Framework Directive (WFD) uses phytoplankton as one of the ecosystem component required to monitor the quality status of the marine and freshwater bodies. Phytoplankton is also a required biological component of Environmental Impact Assessment (EIA) to ensure that impacts on the biodiversity are taken into account and adverse effects are avoided or minimized.
Analysis of phytoplankton begin with sample collection using Van Dorn water sampler or plankton net, preservation, identification of samples to lowest level possible, enumeration to data interpretation including statistical analysis of the population obtained. A long term monitoring program could provide better and accurate information on the state of the biodiversity and assessing priorities for conservation of a target area.