V.V. Kuznetsov (VNIRO, Russia)

The shelf of the high-Arctic seas (Kara, Laptev, East Siberian, Chukchi Seas) is rich in hydrocarbons, whose development has already started.

To minimize harmful effects of this process for environment and bioresources it is necessary to organize ecological monitoring of aquatic ecosystems.
The freshening due to runoff of the great Siberian rivers (Lena, Yenisei, Ob) and other flows is a characteristic feature of the high-Arctic seas’ shelf.

Now the riverine input of industrial, agricultural, and domestic wastes is the main factor of shelf pollution.

The proper sea waters of these seas are characterized by the low bioproductivity and scarcity of ichthyofauna. The specific secondary water mass (brackish water mass forming as a result of mixture of Arctic sea surface water and river water) which is highly variable both in time and space with respect to its volume and configuration, is inherent in the high-Arctic seas. It is characterized by euryhaline fauna of planktonic organisms and fishes.

The brackish-water populations of whitefishes are the main fishery resource of shelf areas intended for field development. More or less, these areas are developed also by freshwater populations. The favorable conditions for existence of fish populations are formed due to the volume river discharge determining freshening, warming of coastal areas, input of nutrients, off-shore ice displacement and its melting.

The establishment of ecological monitoring suggests estimation of the present natural and anthropogenic background in areas intended for field development, with identification of sites characterizing by large fishery importance, determination of localities with pollutant accumulation, and further tracing of occurring changes. The approaches to establishment of monitoring in local area destined for drilling and at scale of large estuarian ecosystems must be different. In the first case the complex detailed (with account of biotope patchiness) survey of selected area and adjacent waters is necessary.

In the second case, first of all, the proper selection of monitoring stations is needed. The observations in the productive brackish-water zone, especially in area of critical salinity (5-8%o) where sedimentation of suspensions, colloid flocculation, and pollutant accumulation occur, are of special interest. The ecological health of vast watershed territory may be judged from observations at minimal number of properly selected sites and stations.

When determining a work period, it is necessary to take into account the temporal dynamics of the main environmental factors affecting the ecosystem state, which is inherent in estuaries. This dynamics is characterized by: 1) important seasonal component associated with fluctuations in river discharge; 2) periodic tidal changes; 3) aperiodic changes due to offshore and inshore winds and wind mixing of water masses of different genesis; 4) considerable temperature variations and role of ice cover, development of which lessens the atmospheric impact on water masses. The Gulf of Ob is characterized by seasonal formation of suffocation waters. Under these changeable conditions any parameter of environment or fishery objects based on sporadic registrations are unrepresentative.

In summer, at the maximal intensity of all biological processes the extensive investigations of bioresources and environment must be conducted. This will allow to determine the general natural and anthropogenic background of interested aquatories, to identify the accumulation areas of pollutants, to clear up questions on bioproductivity and fishery importance of any given area.

The most dynamic state of estuarian ecosystems is observed in periods with the considerable change in river discharge. The ecosystem reorganizations associated with the autumn-winter decrease in river discharge, when area of brackish water mass distribution reduces sharply and large concentrations of commercial fishes are formed in estuaries, are of special interest. At conditions of the Gulf of Ob, the spreading of suffocation waters is an important factor. The occurring changes serve as trigger for wintering, feeding, and spawning migrations and for the local short-term displacements of fish.

Because of technical difficulties, in late autumn and winter much less number of stations may be used for monitoring than during the ice free period. Under the high dynamics of occurring processes, the carrying out of stationary observations comes into importance.

The International Oil&Gas Conference, October 2009

Unpublished articles