Qualitative forecast of possible changes in benthos communities at the oil-gas fields development on the Barents Sea shelf Печать E-mail

FROLOVA E. A., KUZMIN S. A., ZENZEROV V.S. Murmansk Marine Biological Institute RAS

It is known that benthos is a major indicator of the aquatic environment anthropogenic contamination. Peculiarities of its biology (coincidence with definite places of inhabitancy, inactive mode of life, filtration of large amounts of near bottom water etc.) make bottom invertebrates the most vulnerable to different chemical pollutants of the environment. Thus, regular investigations of benthos animals (their quantitative and qualitative characteristics of distribution) are obligatory while EIA procedure of marine engineering environmental site investigations and construction of different hydrotechnical installations is carried out.

Barents Sea shelf possesses large amounts of hydrocarbon raw, during its development different ways for oil-gas transportation are supposed, that is using marine terminals for oil reloading into super-tankers and pipe-lines laid on the sea bottom.

In accordance with the plan for exploration of the Stockman gas condensate field (SGCF) in the Barents Sea lay out of the submarine pipe-line from the Stockman field to the coast near the settlement of Teriberka is supposed.

Murmansk Marine Biological Institute KSC RAS carried out investigations of benthos communities in the Barents Sea coastal zone including the Teriberskaya bay area for many years as there occur large settlings of both: rare and commercially valuable species of benthos animals.

In the paper there presented the analysis results of current state of benthos in the coastal Barents Sea zone in the Teriberskaya bay area according to the materials of benthos surveys earned out by MMBI in recent years. Primary processing and species composition of the benthos samples was fulfilled by the members of the zoobenthos laboratory: E.A. Frolova, S.A. Kuzmin. O.S. Lyubina. N.N. Panteleeva, A.V. Gudimov, A.A. Frolov, E.A.Garbul, L.V. Pavlova. D.R. Dikaeva, V.N. Payusova. Account of both: sub-littoral and littoral fauna was conducted applying surveying frames 0.5 m. The materials obtained were processed using standard hydrobiolgical methods.

The data on the current state of littoral and sub-littoral bottom invertebrates biocenoces have been obtained by the data processing of expedition works earned out in the Teriberskaya bay area and especially in the area of planned pipe-line outlet from the Stockman field. It should be stated that the species list was replenished and now it consists of 274 taxons among which 243 are on the species level. There discovered 15 not noted earlier taxons including 9 species.

Comparison of benthos surveys data carried out by MMBI in previous and recent years did not reveal significant differences in bottom communities. Nowadays there exist undisturbed biocenoses of bottom invertebrates on littoral and sub-littoral zone.

The results of carried out investigations show that in the Teriberskaya bay and in the coastal zone where layout of pipe-line is planned there located settlings of benthos animals belonging on the one hand to rare species, on the other - to commercially valuable animals.

According to the data available in the upper sub-littoral of the Teriberskaya bay there inhabits not less than 220 species of bottom invertebrates, species abundance of which is in average about 120 species 0.5 m, and fluctuations in separate points might be in the range 82 -176 species 0.5 m2. Average biomass of settlings is 1 017 g/m2, the density of settlings of these species varied in the range 425 - 16376 specimens/in2.

In the immediate vicinity from the coast at the distance not more than 10 miles there located a community with dominance of such warm- water forms as urchins Echinus esculentus and Brisaster fragilis, not occurring in other Barents Sea areas. It should be stated that the first urchin species is referred to the protected in the Murmansk region animal species.

Special attention in our work is paid to the commercially valuable and perspective for fishery benthos animals species inhabiting in this region. Thus, in the coastal zone not far from the Teriberskaya bay there located settlings of commercially valuable bottom invertebrates: holothurians, modioluses, urchin, blue mussels and others.

On the Geese fishing ground and in the area of Sem Ostrovov (Seven Islands) archipelago there located settlings of scallop the stock of which is approximately 35-40 thousand ton. On the slopes of the Geese fishing ground annual fishery of deep water prawn and bottom fish species is carried out. Besides, the Geese fishing ground slopes is one of the major places of inhabitancy of the introduced into the Barents Sea valuable commercial species - Opilio crab.

In the area of the Teribersky cape during last decade (10 years) a commercial grouping of the red king crab is observed.

In a variant area of sea bottom estrangement for the pipe-line a reproductive stock might constitute of red king crab might be more than 40 ton, commercial - about 100 ton.

The data obtained testify to the fact that in the area of the planned layout of pipe-line from the Stockman field to the coast through the Teriberskaya bay there concentrated significant settlings of commercial bottom invertebrates species and this region is to be considered a zone of special vulnerability when the works on the realization of the design for the Stockman field are earned out.

To our opinion fulfillment of the dredging works at the layout of the pipe-line might impact negatively the bottom fauna in this region. If to speak on the red king crab, then pipeline layout in the coastal zone and in the Teriberskaya bay might disturb spawning grounds and places of inhabitancy of red king crab and especially its juveniles, which might lead to the decrease of its что reproductive part in the Barents Sea.

A possible accident at the pipe-line in the area of its outlet to the coast might also cause worsening of the ecological situation, as marginal ecotons to which littoral, sub-littoral and supra-littoral are referred, are the most productive.

Besides damage due to the possible contamination of the area with gas condensate it might be increased owing to the direct destruction of the pointed above ecotons. In the places of pipes layout bottom animals with soft body covers might die, moreover, at the deepening of pipe-line there might occur changes of bottom sediments texture with destruction of the existing now structure of bottom biocenoces. Appearance of the suspension and increase of turbidity of the near bottom water layer might become dangerous for the vital activity of organisms-filtrators.

Restoration of benthos communities on the littoral according to our calculations when the construction works are over might take not less than 3 years and red king crab population restoration up to 5 years.

As a conclusion it might be said that the presented in out paper data ground the urgency and necessity to carry out ecological monitoring and first of all investigations of benthos state in the areas and regions which might be subjected to the negative anthropogenic impact.



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