9.1.1 Investigation of Negative Effects and 

 Critical Concentrations of Some Toxic 

 Substances on the Plankton Community 



MIKHAIL N. KORSAK'. TERRY E. WHITLEDGE*. VASSILIY M. KUDRYATSEV, and NILA V. MAMAEVA* 

 ^Institute of Global Climate and Ecology. State Committee for Hydrometeorology and Academy of Sciences, Moscow, USSR 

 ^Marine Science Institute, University of Texas at Austin, Port Aransas, Texas, USA 

 *Southeni Division of the Oceanographic Institute of the USSR Academy of Sciences, Oceanologiva, USSR 



Introduction 



In recent decades anthropogenic effects have contributed 

 to pollution in the World Ocean and have decreased the natural 

 ability of marine ecological systems forcontinued reproduction 

 and regulation, especially in those regions where continuous 

 pollution inputs occur (Izrael, 1979; Izrael & Tsyban, 1989). 

 Since marine environmental pollution continues to occur, it is 

 necessary to conduct ecotoxicological research on the effects 

 on plankton. In order to predict the ecological consequences of 

 marine pollution, it is necessary to understand the oceanographic 

 and biological processes controlling the values and the limits of 

 critical concentrations of different pollutants ( Izrael & Tsyban, 

 1989). The critical concentration concept means that the 

 content of the pollutants in the aqueous medium will not initiate 

 nonreversible changes in the ecosystem being considered. If 

 pollutant concentrations are larger, then the value of critical 

 concentration will lead to degradation and nonreversible changes 

 of the plankton (Nosov & Syrotkina, 1981; Egorov 

 etal., 1 984; Korsak& Egorov, 1985;Lifshits& Korsak, 1988; 

 Izrael & Tsyban, 1989; Maximov et ai, 1989; Korsak & 

 Timoshenkova, 1990). 



The results of ecotoxicological research has shown that 

 the intluence of low concentrations of pollutants on a plankton 

 community causes individual physiological effects in sensitive 

 marine organisms. However, there may be no significant 

 changes in the ecosystem that are expressed in the form of 

 structural and functional changes of the main ecosystem 

 characteristics such as primary production/destruction (P/D) 

 coefficients, for example. The increase of a toxic contaminant 

 influence in an ecosystem first results in a decrease of the 

 number and biomass of the most sensitive plankton organisms. 

 If a toxicant concentration increases further the most .sensitive 

 organisms will be completely replaced by more resistant 

 planktonic species that occupy the nearest ecological niche 

 (Odum, 1975; Nosov & Syrotkina, 1981). In the final stage 

 there will be a few species, but total biomass will possibly 

 increase. 



During the Third Joint US-USSR Bering & Chukchi Seas 

 Expedition, ecotoxicological experiments were performed on 

 the basis of a "dose-effect" scheme (Lifshits & Korsak, 1988; 

 Korsak & Timoshenkova, 1990). They were conducted with 



the purpose of determining the limits of natural variation of 

 critical concentrations of a plankton community to 

 benzo(a)pyrene (BaP), polychlorinated biphenyls (PCB's), 

 cadmium (Cd), and copper (Cu) pollutants. The biological 

 responses measured were primary production (P), bacterial 

 production (B^,), and the total number of microzooplankton. 



Experimental Procedure 



Water samples for the experiments were collected from 

 the surface with 5-1 plastic Niskin samplers. Nutrient samples 

 were analyzed in the initial water for nitrate, ammonium, and 

 phosphate using standard techniques. The experimental 

 additions of 0.1, 1.0,5.0, and IOngofBaP/1; I.O, 10, 20, and 

 50 |ig of PCB/I; 2, 4, 10, and 20 |ig of Cu/I; 10, 20, 40, and 

 60 |ig of Cd/1 were made within 30 min after collection. The 

 experimental bottles (150 ml) were placed in a shipboard deck 

 incubator with flowing seawater under natural illumination. At 

 the end of incubation unpreserved subsamples were used for 

 the determination of the total number of microzooplankton as 

 well as primary production and bacterial destruction using 

 previous '"'C-methods (Egorov et ai. 1984). The data were 

 then used for calculations of LC^o values (Liftshits & Korsak, 

 1988). 



Results 



The ecotoxicological data and critical concentrations of 

 BaP, PCB's, Cu and Cd from experiments performed in the 

 Bering and Chukchi Seas are presented in Tables 1-8 and 

 Figs. 1-8. Those data show the range of toxicity of the 

 investigated pollutants in the following decreasing toxicity: 

 BaP, Cu, PCB's, Cd (Table 7, 8; Figs. 1-8). 



The LC,n values, which approximate critical concentration 

 values for BaP during its influence on phyto- and 

 microzooplankton in the Bering Sea, vary from 0.1 to \0\xgf[ 

 in relation to primary production (Table 7). When 

 microzooplankton are used as a biological target, the critical 

 concentration values range from 0.05 to 7 ^ig/1 (Table 7). For 

 the Bering Sea, the average critical concentrations for BaP on 

 phyto- and microzooplankton were 3. 6and 1.0 (ig/1, respectively 

 (Table 7). The most sensitive phytoplankton communities to 



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