Plankton generally refers to drifting organisms that live in water and lack effective fluidity, including phytoplankton and zooplankton. Some plankton have the ability to swim, but their swimming speed is often slower than the ocean current, so they can't swim flexibly and effectively in the water.
Plankton, among the creatures in the sea, lakes, rivers and other waters, has no fluidity at all, or is very weak, so it can't move against the current, but lives on the water surface. This creature is always called plankton. Plankton is a small organism, most of which are invisible to the naked eye, suspended in the water layer and have poor swimming ability. It is called plankton. Plankton is a kind of biological group divided by lifestyle, not by species.
Plankton generally refers to drifting organisms that live in water and lack effective fluidity, including phytoplankton and zooplankton. Some plankton have the ability to swim, but their swimming speed is often slower than the ocean current, so they can't swim flexibly and effectively in the water.
Distribution characteristics:
Marine plankton can be roughly divided into three types according to latitude: cold zone species, temperate zone species and tropical zone species. They are quite different in kind and quantity. Generally speaking, there are few species of plankton in cold regions, and there are many species. On the other hand, there are many species of tropical plankton, but the number of each species is small; Temperate plankton is somewhere in between. For example, pteropods are not found in the North Yellow Sea, only 8 species in the South Yellow Sea, 365,438+0 species in the East China Sea and 50 species in the South China Sea. Temperature is obviously the main factor of this phenomenon.
The horizontal distribution of plankton is closely related to cold current and warm current, so some species can often be used as indicators of cold current and warm current. For example, tube jellyfish and silver coin jellyfish can be used as indicators of Kuroshio warm current in the East China Sea.
Besides temperature and current, salinity also affects the horizontal distribution of marine plankton. Generally, the offshore plankton belongs to the broad salt species, which is widely distributed, while the offshore plankton belongs to the narrow salt species, which is relatively narrow in distribution. Nutrient is also a factor affecting the horizontal distribution of marine plankton. In the nutrient-rich coastal waters, there are a large number of phytoplankton.
The horizontal distribution of freshwater plankton is mainly affected by temperature. According to different habitats, it can be divided into three types: frigid species, temperate species and tropical species. There are many world-wide temperate species, which are caused by the widespread spread of wind or birds in resting spore or resting eggs. Many species of freshwater cladocera in the world were formed through the spread of resting eggs.