Scientists from the Shirshov Institute of Oceanology (IO) RAS, for the first time in the world, have conducted a large-scale study of how life on the bottom of the Arctic Ocean changes with depth. This was reported on Friday in the press service of the Ministry of Science and Higher Education of the Russian Federation.

"The depth distribution of life is called 'vertical' or 'bathymetric', and is usually studied within individual regions or seas. In their new study, scientists have conducted such an analysis for the first time on the scale of the entire Arctic Ocean and with a large coverage of depths - from 14 to 5416 m. The authors used both their original data, obtained at about 150 stations, and a large array of published information," the press service said in a statement.

Speaking about the applied significance of the results obtained, scientists note that ideas about the distribution of life in the depths of the Arctic Ocean may be needed if it is necessary to assess the impact on the environment associated with economic activities. For example, when assessing environmental risks associated with the operation of the Northern Sea Route, or when laying deep-sea pipelines.

Scientists have found that the greater the depth, the smaller the number of animals living on it.

“Why do the “sets” of animal species change with depth in the ocean? There is no simple answer to this question. But each species has its own “range of vertical distribution”, in depth there is an upper limit of distribution and there is a lower limit. What do they depend on? Rather in total, from a complex of reasons, among which the most important are environmental factors (temperature, salinity, soil type, organic matter content in sediment, etc.) and interaction with other species that live "in the neighborhood," the press service cites words of Andrey Gebruk, Deputy Director for Scientific Work of Marine Ecology of the IO RAS.

Areas of vertical distribution

The scientist noted that on the basis of a complex of such factors, "areas of vertical distribution" of marine animal species are formed. In deep-sea animal species, vertical ranges can vary greatly: in some it is the first hundreds of meters, in others it is several thousand meters in depth.

"The most difficult and interesting task is to trace the depth horizons at which the "thickening" of the boundaries of the ranges occurs: for some species this may be the lower limit of distribution, for others - the upper. Zones of "thickening of the boundaries of the ranges" indicate the most important universal boundaries of the distribution of species in nature, that is, on biogeographical boundaries," said Gebruk.

In the Arctic Ocean, several depth horizons with similar sets of species and predominant forms have been identified. These horizons are called "lower shelf", "upper slope", "lower slope" and "abyssal". They encircle the entire ocean, located one under the other. The most important result of the work was the clarification of the position of the boundaries between these belts, or, in other words, the position of the main boundaries in the distribution of life in depth.

The revealed patterns of the vertical distribution of life at the bottom of the Arctic Ocean turned out to be universal for the entire basin. So far, it is not completely clear what caused such a discrepancy in the position of the vertical boundaries in the Arctic Ocean from the average pattern throughout the World Ocean. Among these reasons, there may be a unique ice regime, and features of the formation of primary production, and the most powerful freshwater outflow into the ocean by northern rivers.