Composition and location of trophic groupings of zoobenthos in the Arctic Ocean

. This study is devoted to the distribution of trophic groups of zoobenthos in the Arctic Ocean. The patterns of distribution of detritus feeders, seston feeders, and predators along the bottom of the Arctic polar basin are analyzed. The object of the study is the geoecology of the distribution of food groups of benthic animals in the polar regions. The subject of the study is the methods used in assessing the distribution of zoobenthos with different types of nutrition in the polar regions. The results of the work are based on the analysis of the vertical and horizontal structures of the distribution of benthic fauna, reflected in the map of the distribution of trophic groups of zoobenthos and systematized in the distribution table of the leading species of zoobenthos in the Arctic Ocean. To assess the patterns of geoecological distribution of zoobenthos according to the method of feeding, the following were used: actual and cartographic scientific data on the relief, soils, waters, ice cover, maps on the distribution of plankton and the content of organic matter in bottom sediments, as well as data on the trophic characteristics of the benthic fauna of the polar regions, leading biocenoses of the polar regions and geo-ecological conditions for the existence of benthic fauna in the polar regions. This article presents a map of the distribution of zoobenthos in the Arctic Ocean (according to literary sources), developed by the author, and a table of distribution of guide species of zoobenthos trophic groups in various areas of the Arctic Ocean, compiled by the author based on literary sources. The obtained results of the distribution of food groups of zoobenthos can be used in further detailed assessment of food reserves of bioresources in the polar regions of the World Ocean and their consumption; when designing the economic development of the polar regions; during landscape monitoring


Introduction
The trophic factor, which depends on relief features, hydrodynamics, sedimentation rates and organic matter content in bottom sediments, has a dominant influence on the distribution of oceanic zoobenthos in polar latitudes.

Materials and Methods
According to the trophic attribute, benthic marine animals can be divided into: sestonophages (filter feeders associated with the absorption of seston), detritophages (collecting detritus on the bottom surface and in the sediment column (subsurface deposit feeder)), and predators (eating living individuals).Species are distinguished as trophically stable (Table 1), i.e. they feed only in a certain way and plastic species that feed in a combination depending on food availability.Mapping of the locations of various trophic groups made it possible to map the location of benthic fauna in the Arctic polar region (Fig. 1), as well as to identify guiding forms of zoobenthos food groups in the Arctic Ocean (Table 2).The geodetic base of the Arctic contour map at a scale of 1:25 000 000 was taken as the working basis of the trophic map.The available material on zoobenthos distribution was preliminarily systematised based on the quantitative and qualitative composition of benthic animals.Subsequently, the obtained material was reflected in the iconic way, reflecting the trophic affiliation of the find with reference to the location of its detection.In the case of mass finds, trophic diversity was reflected on the map, while numbers were recorded separately.This explains the off-scale nature of the conventions, as it is not possible to reflect the actual number of data on a small-scale map in a pictorial way.A total of about 3,000 discoveries were recorded within the Arctic Ocean boundary.

Results and discussion
The trophic membership of benthic fauna includes: sestonophages (extracting food from benthic suspension), detritophages (feeding directly from the substrate) and carnivores (predators).
A more detailed classification of sestonophages includes mobile and stationary forms.Non-mobile sestonophages inhabit shallow waters, rocky and stony shores, as well as shelf and continental slope margins and submarine uplands, i.e. areas of coarse sediment distribution.Their spreading is confined to areas of interaction between coastal waters and deep subsurface water masses, as well as in zones of abrupt landform change accompanied by intensified hydrodynamics.Areas of junction of waters of different origin, increased current velocities and intensive mixing lead to high concentrations of biogenic elements, increased suspended solids content in bottom waters, good aeration on stony and hard mixed sediments.Mobile sestonophages settle predominantly in sandy sediments under conditions of active mobility of benthic waters where the processes of organic suspended sediment transport over the bottom prevail over the processes of its settling.
Detritophages are classified as gatherers and selective swallowers.Gathering detritophages feed on organic detritus and microflora from the surface of the bottom.They settle on fine-grained sediments (aleurite, silt) containing organic matter in areas with slow movement of bottom waters, where the process of settling of organic suspended matter prevails over the process of its transport.Detritophagous, indiscriminately ingesting substrate, inhabit the surface sediment column and use the substrate in which they live as food material.They settle predominantly in fine-grained sediments with organic matter content and retarded hydrodynamics that promote the settling of fine soil fractions.
Carnivorous zoobenthos feed on living and dead organic matter.Its distribution depends on food items.
However, the trophic classification of benthic marine invertebrates cannot have a clear system, as organisms with a stable and plastic type of feeding are distinguished, having the ability to switch, if necessary, from one type of food to another, to change the source and method of receiving food or to receive it simultaneously from several sources (Table 1).Thus, different feeding conditions have been created on the seabed in different parts of the ocean for the deep-sea bottom population.
The maximum quantitative distribution is observed for representatives of predators, which is explained by the almost ubiquitous availability of food resources represented by different species of animals.The distribution of detritivores is mostly confined to the slopes of depressions and in-shelf troughs, as well as to certain areas of coastal shallows [2].This is facilitated by the high concentration of organic matter deposited in the fine fraction of the bottom sediments lining the deep sea benthic areas.The maximum input of nutrients in these areas is associated with divergence zones.Sestonophages are observed in coastal areas, shallow waters, continental slopes and slopes of depressions.This fact is explained by the presence of rigid substrates and bottom currents in these areas, as well as by the high sedimentation rate (Fig. 1).
The coastal parts of the shelf zone of polar oceans with distribution of rigid soils are inhabited mainly by sestonophages [3,4].In these areas both mobile and stationary sestonophages are present.Dominance of the former is confined to areas of ice spreading and erosion of bed rocks.Stationary sestonophages are maximally concentrated in areas of strong bottom currents and active wave processes.
The central parts of the shelf up to the continental slope are dominated by detritophages, with few sestonophages in some areas (Table 2).The mainland slope in the central part is inhabited by detritophages, the foreshore and foothill are zones of overlapping of sestonophages and detritophages, as they are areas of sand and pelitic soil fraction drift and underwater currents.The ocean floor is covered with fine-grained soils and is an area of detritophage distribution [5,6].The submarine uplands are inhabited by sestonophages (predominantly coarse-silty and sandy soils, washed away by the currents).The upper parts of the deepwater trough slopes are inhabited predominantly by detritivores, less so by sestonophages as they are lined by fine-grained substrates and have a low degree of sedimentation.The bottoms of depressions are generally hardly inhabited, as the content of organic matter in sediments and the bottom layer is minimal.In the Arctic Ocean, benthic fauna does not go below 3,500 m.

Conclusions
The following conclusions were drawn in the course of the study: The most optimal conditions of existence are found in the near-continental area.It is here that the greatest species diversity of zoobenthos is represented.
Benthic fauna of the Arctic Ocean periphery is represented predominantly by sestonophages, the central part of the ocean is occupied by fine-grained ground fractions, which are inhabited predominantly by detritophages.Predators are widespread.
The distribution of the leading species of zoobenthos trophic groupings indicates the presence of representatives of bottom fauna in all areas of the Arctic Ocean.

Fig. 1 .
Fig. 1.Map of zoobenthos trophic groups in the Arctic Ocean (from literature sources).

Table 1 .
Trophic characteristics of benthic fauna of polar regions.

Table 2 .
Distribution of leading species of zoobenthos trophic groupings in different areas of the Arctic Ocean.