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General Characteristics of Sea Biota |
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General Characteristics of Sea Biota
The populations of the sea may be grouped under three major categories, viz. plankton, nekton and benthos.
While the plankton and nekton are found in the pelagic environments, the benthos inhabit the benthic region. Benthos are sessile, creeping or burrowing organisms which spend most or whole part of their life on or inside the benthic substrata. Organisms of this group are found distributed from the highest high tide level to the deep bottom of the sea.
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The benthic forms are represented by (a) sessile animals like sponges, barnacles, mussels, oysters, coraIs, worms, seaweeds, benthic diatoms and (b) creepers like crabs, lobsters, some copepods, amphipods, crustaceans, protozoans, snails, fishes, etc. and (c) burrowers like clams, worms, echinoderms, etc.
The group nekton (swimming) comprises active swimming animals is found in the pelagic part. Most of the adult squids, fin and shellfishes, and mammals like whales come under this category. These are larger animals provided with some swimming organs with which they can swim and move against the water currents, waves, etc.
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The group plankton (wandering) comprises minute, microscopic plant and animal components of the pelagic I system, which are passive drifters. These floating creatures are carried away by the water currents. The two main divisions of plankton are phytoplankton I and zooplankton. While the former include minute floating plants, the latter is represented by diverse permanent animal plankton and also the eggs and - larvae of swimming and benthic organisms.
Nutrient availability is extremely important in determining microbial productivity in marine habitats. Recycling of mineral nutrients is very slow in the pelagic environment.
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Dead organisms from the euphotic epipelagic zone (zone of effective light penetration) sink into the great depths of the bathypelagic and ultimately the benthic zone. They carry with them essential nutrients, mainly nitrogen and phosphorus that are liberated in the perpetual darkness of the deep ocean. From here they are returned to the surface water by upwelling currents at extremely slow rates. Upwelling phenomena often occur along the continental slope, caused by surface currents running rapidly away from the shore and being replaced by deeper, nutrient rich water
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Marine plankton is the major source of organic matter and comprises numerous species of diatoms, cyanobacteria, dinoflagellates, chrysomonads and chlamydomonads. Phytoplanktons (phyto-plants, plankton-wandering) are otherwise called free-floating plants. A common planktonic alga is Synecoccus. Picocyanobacteria may represent 20-80% of the total planktonic biomass. These act as a source of food for marine fishes.
Planktonic algae, under certain environmental conditions, may grow into an enormous population with resultant discolouration of water, a condition referred to as bloom. For example, the characteristic colour of' red sea' is associated with blooms of pigments.
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Marine plankton is the major source of organic matter and comprises numerous species of diatoms, cyanobacteria, dinoflagellates, chrysomonads and chlamydomonads. Phytoplanktons (phyto-plants, plankton-wandering) are otherwise called free-floating plants. A common planktonic alga is Synecoccus. Picocyanobacteria may represent 20-80% of the total planktonic biomass. These act as a source of food for marine fishes.
Planktonic algae, under certain environmental conditions, may grow into an enormous population with resultant discolouration of water, a condition referred to as bloom. For example, the characteristic colour of' red sea' is associated with blooms of pigments.
Bacterial population depends on the distribution of phytoplankton since the latter contributes organic substance and solid surfaces for bacterial aggregation. Growth of psychrophilic and halophilic microbes are common. Among the psychrophilic organisms are the luminous bacteria that can produce light in the presence of oxygen. These bacteria exist in symbiotic association with marine animals.
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