Marine Phytoplankton Essay

Phytoplankton From Wikipedia, the free encyclopedia Jump to: navigation, search Diatoms are one of the most common types of phytoplankton. Phytoplankton are the autotrophic component of the plankton community. The name comes from the Greek words cpur?v (phyton), meaning â€Å"plant†, and TIXay? «?q (planktos), meaning â€Å"wanderer† or â€Å"drifter†. [l] Most phytoplankton are too small to be individually seen with the unaided eye. However, when present in high enough numbers, they may appear as a green discoloration of the water due to the presence f chlorophyll within their cells (although the actual color may vary with the species of phytoplankton present due to varying levels of chlorophyll or the presence of accessory pigments such as phycobiliproteins, xanthophylls, etc. ). Contents [hide] * 1 Ecology * 2 Aquaculture * 3 Blooms * 4 See also * 5 References * 6 External links [edit] Ecology Phytoplankton are the foundation of the oceanic food chain. Of these, the best known are dinoflagellate genera such as Noctiluca and Dinophysis, that obtain organic carbon by ingesting other organisms or detrital material. The term phytoplankton encompasses all photoautotrophic microorganisms in quatic food webs. Phytoplankton serve as the base of the aquatic food web, providing an essential ecological function for all aquatic life. However, unlike terrestrial communities, where most autotrophs are plants, phytoplankton are a diverse group, incorporating protistan eukaryotes and both eubacterial and archaebacterial prokaryotes. There are about 5,000 species of marine phytoplankton. [8] There is uncertainty in how such diversity has evolved in an environment where competition for only a few resources would suggest limited potential for niche differentiation. [9] In terms of numbers, the most important groups of phytoplankton include the diatoms, cyanobacteria and dinoflagellates, although many other groups of algae are represented. One group, the coccolithophorids, is responsible (in part) for the release of significant amounts of dimethyl sulfide (DMS) into the atmosphere. DMS is converted to sulfate and these sulfate molecules act as cloud condensation nuclei, increasing general cloud cover. In oligotrophic oceanic regions such as the Sargasso Sea or the South Pacific Gyre, phytoplankton is dominated by the small sized cells, alled picoplankton, mostly composed of cyanobacteria (Prochlorococcus, Synechococcus) and picoeucaryotes such as Micromonas. [edit] Aquaculture Diagrams of some typical phytoplankton. Main article: Algaculture Phytoplankton are a key food item in both aquaculture and mariculture. Both utilize phytoplankton for the feeding of the animals being farmed. In mariculture, the phytoplankton is naturally occurring and is introduced into enclosures with the normal circulation of seawater. In aquaculture, phytoplankton must be obtained and introduced directly. The plankton can either be collected from a body of water or foodstock for the production of rotifers[10], which are in turn used to feed other organisms. Phytoplankton is also used to feed many varieties of aquacultured molluscs, including pearl oysters and giant clams. The production of phytoplankton under artificial conditions is itself a form of aquaculture. Phytoplankton is cultured for a variety of purposes, including foodstock for other aquacultured organisms[10], a nutritional supplement for captive invertebrates in aquaria. Culture sizes range from small-scale laboratory cultures of ess than 1 L to several tens of thousands of liters for commercial aquaculture[10]. Regardless of the size of the culture, certain conditions must be provided for efficient growth of plankton. The majority of cultured plankton is marine, and seawater of a specific gravity of 1. 010 to 1. 026 may be used as a culture medium. This water must be sterilized, usually by either high temperatures in an autoclave or by exposure to ultraviolet radiation, to prevent biological contamination of the culture. Various fertilizers are added to the culture medium to facilitate the growth of plankton. A culture must be aerated or agitated in some way to keep plankton suspended, as well as to provide dissolved carbon dioxide for photosynthesis. In addition to constant aeration, most cultures are manually mixed or stirred on a regular basis. Light must be provided for the growth of phytoplankton. The colour temperature of illumination should be approximately 6,500 K, but values from 4,000 K to upwards of 20,000 K have been used successfully. The duration of light exposure should be approximately 16 hours daily; this is the most efficient artificial day length[10]