2. Plankton (Phytoplankton; Zooplankton)
• algae (phytoplankton)
• predominantly protozoa and other minute animal life (zooplankton)
• Phototrophic microorganisms are regarded as the most important
plankton since they are the primary producers of organic matter via
photosynthetic or chemosynthetic
marine and fresh water habitats
diatoms and dinoflagellates
microscopic animal forms
marine and fresh water habitats
primary or secondary consumer
Holoplankton, meroplankton and
blue-green algae, and
cyanobacteria are examples
Crustaceans-like krill, holoplankton,
meroplankton, protozoans, and worms
are examples of zooplankton.
9. Mixing of Waters (Upwelling)
• The movement of water by wind, tide, or currents accomplishes some
redistribution of the microbial flora.
Notes de l'éditeur
The aggregation of floating and drifting microbial life in the surface region of the aquatic ecosystem is called plankton Plankton may be composed primarily of algae (phytoplankton) or it may be predominantly protozoa and other minute animal life (zooplankton). Phototrophic microorganisms are regarded as the most important plankton since they are the primary producers of organic matter via photosynthesis.
Most phytoplanktonic organisms are motile, possess some structural feature, or contain oil droplets which give them buoyancy; all these features aid the organisms in maintaining their location in the photosynthetic zone (see Figs. .26-4A and B). The multitude of physical conditions which influence the plankton population quantitatively and qualitatively are shown in Fig. 26-5.
The shape of a diatom can be a sphere, ellipse or star. The significance of the diatoms is the silica shell, which serves as the cell wall of diatoms. Most dinoflagellates comprise a pair of flagella for the movement. Moreover, the oils in the body of both diatoms and dinoflagellates help the movement through water. The high growth rates of diatoms and dinoflagellates cause algae blooms. The red tide is a type of a marine algae bloom which produces biotoxins. These biotoxins can harm small fish.
Holoplankton remains as a plankton throughout its lifecycle while meroplankton is a larval stage of another life form. Copepods are another type of zooplankton. They are a group of crustaceans. Copepods possess spikes which aid their movement through water. The filter-feeding organisms such as whales, fish, and shellfish eat zooplankton.
Microbial inhabitants of the bottom region of a body of water are referred to as the benthic organisms.
The richest region of an aquatic system in terms of numbers and kinds of organisms is the benthic region.
Many aquatic microorganisms inhabit the gut of marine animals, an even richer habitat.
Since activity is high, oxygen is utilized quickly and as a result, the benthic environment supports aerobic and anaerobic microbes.
Microbial mats are often centimeter-thick multilayered structures of microorganisms, mainly bacteria, archaea, fungi, and sometimes these mats are enriched with protozoans. Microbial biofilms are in contrast much thinner (10–100 µm) than microbial mats and have a different architecture
A phenomenon called upwelling occurs in an ocean when water rises from a deeper to a shallower depth, usually as a result of divergence of offshore currents or winds.
In this process the bottom water carries with it a rich supply of nutrients that are delivered to the surface region.
Geothermal vents also contribute to the total nutrient budget of the ocean. It has been calculated that vents such as the one near the Galapagos Islands account for most of the nutrients dissolved in the oceans of the world. Prior to discovery of these vents, oceanographers were unable to account for nutrients on the basis of precipitation, input from rivers and streams, and other obvious sources. Another interesting feature of the oceans is the gyre, large spiralling surface currents in the ocean that tend to aggregate and retain nutrients, wastes, and microorganisms. Gyres have only been appreciated in recent years, through the use of satellite imagery