Krill is a collective name for various species of the smallest crustaceans, plankton, which inhabit the upper water column. Scientists have been studying krill for a long time, trying to figure out its effect on the environment. And this influence, it must be said, is
very large , despite the tiny sizes of living organisms themselves.
The size of the crustaceans reaches a maximum of two centimeters in length; they themselves serve as food for sea creatures. Krill feeds on very tiny creatures - photosynthetic plankton, which is the basis of the trophic chain of marine and oceanic ecosystems. Despite the fact that the crustaceans themselves are small, their number is simply huge. The krill biomass exceeds the biomass of all creatures living on land and sea.
Krill, in particular, serve as food for the largest living creature on earth - the whales. But these crustaceans are not only important for whales, they have an impact on the entire aquatic environment of the Earth, both literally and figuratively.
Ocean and sea water for humans is just salty, somewhere more, somewhere less. In fact, its salinity varies by region and depth. Water evaporation and freshwater inflows can affect salinity levels. In general, the surface layers of water may vary in salinity. Mixing water layers is important because it provides nutrient and oxygen exchange.
And here just krill is important. Of course, the crustacean itself is nothing, its impact on the water and the environment is negligible. Nevertheless, a huge number of crustaceans leads to a change in the processes of mixing layers of water in the seas and oceans. Krill perform daily and seasonal migrations. At night, the crustaceans go more deeply, in the daytime they rise to the surface. The depth of migration can reach hundreds of meters. The general movement of huge masses of tiny crustaceans leads to mixing of various layers of water.
The boundaries between the individual layers are literally erased. True, to track what is happening in natural conditions is very difficult, if not impossible. Therefore, the group from Stanford decided to conduct a study of the situation in the laboratory.
To create a model of a natural part of the ocean, specialists used a large cylindrical container. Then salt solutions of various concentrations were added to it. The result was a layer of water consisting of two parts with different concentrations. And already after that, krill was added to the water - tiny shrimps of the species Artemia salina. Rachkov was added a lot, in a cubic meter, their number reached from 20 thousand to 140 thousand individuals.
It seems to be a lot, but in nature it is a normal concentration of krill - sometimes less, sometimes more, but on average this is the case.
The results of the experiment were very interesting. The crustaceans stirred two different layers of water, and quite strongly. If one crustacean generates a very weak flow of water, then all together these crustaceans create the strongest currents that are amenable to instrumental measurements without any problems. Gradual separation of water layers with different salt concentrations is leveled as a result of migrations.
The experiment was relatively close to reality, in nature this situation does not repeat with 100% probability. The fact is that the migration of shrimps in the tank was stimulated by turning off the blue LEDs on the bottom. When turning on the light, the shrimps were striving downwards; when turned off, they were passively swimming in the water column. Intensive lighting leads to more active migration of crustaceans - under natural conditions it is less strong. However, this is a significant approximation to those conditions that are characteristic of the oceans and seas.
Scientists who conducted the study believe that the value of krill is very high, it can be called global. The mixing of water layers as a result of the activity of miniature creatures influences the biogeochemical structure of the ocean. ”It is clear that not only krill is involved in these processes, but it is clear from his example how important living organisms are.
DOI:
10.1038 / s41586-018-0044-z