5.2.1 Ciliate Protozoa in Plankton 



NILA V. MAMAEVA 



Institute oj Oceanology of the USSR Academy oj Sciences. Southern Branch. Gelendzhik. USSR 



Introduction 



Methods 



Intense growth of protozoa was observed throughout the 

 Bering and Chukchi Seas. The maximum Cihophora biomass 

 was found to be higher in the Chukchi than in the Bering Sea. 

 Values were 1.22 and 2.33 g/m", respectively. Most of the 

 infusoria mass occurred in the top 40 m of the water column. 

 Although the taxonomic composition was virtually the same as 

 in 1981, it was substantially different in the two seas. Genus 

 Strombidiitm oligotrichids were predominant in both seas. The 

 degree of Ciliophora development corresponded to chlorophyll 

 levels. Ciliate protozoa are a key factor in the ecosystems of 

 both seas. According to mean data for the layer of maximum 

 concentrations, they may account for as much as 1.5 g of 

 primary nutrient/m Vd circulating in the Bering and 2 g/mVd in 

 the Chukchi. The production yield of ciliate protozoa is 

 1 g/mVd. 



Today, as pollution threatens to engulf the world's oceans, 

 the study of sea areas removed from highly industrialized and 

 densely populated regions (i.e.. areas such as the Bering and 

 Chukchi Seas) is becoming of increasing interest to researchers 

 (Izrael&Tsyban, 1983). Thehighly productive waters of these 

 areas are characterized by extremely intense growth of early 

 stages ofthe food chain, especially ofciliate protozoa (infusoria). 

 As the major constituent of microzooplankton. the infusoria 

 serve as a link between the primary food (algae and bacteria) on 

 the one hand and the larger consumer species on the other. 

 Hence, these organisms in large measure drive the 

 transformation of organic matter in the lower stages ofthe food 

 chain. In addition, ciliate protozoa are an excellent indicator of 

 water quality or pollution level. Information about this 

 component of the plankton community of the Bering and 

 Chukchi Seas, however, remains meager. Fraginentary early 

 data (Stepanova, 1937) have now been supplemented by more 

 recent findings (Mamaeva, 1983). 



The chief purpose ofthe present study, undertaken within 

 the Third Joint US-USSR Bering & Chukchi Seas Expedition 

 in July-November 1988 during the 47th cruise ofthe research 

 vessel (R/V)/4 A«(7('/;h' A: Korolev. was to pursue the investigation 

 ofthe plankton Ciliophoracommunity. Research areas included 

 1. species composition; 2. quantitative distribution over the 

 water column and sea areas; 3. links with abiotic and biotic 

 factors in the environment; 4. quantitative role in the food 

 chain; and 5. use as an indicator ofthe environmental status of 

 a given sea area. 



The Bering and Chukchi Seas have extremely 

 heterogeneous ecosystems. Individual areas of both seas are 

 characterized by distinctive hydrological and hydrochemical 

 parameters. This meant that this study had to be conducted in 

 a discrete manner for each individual subarea chosen 

 (Frontispiece). 



Sampling was performed using Niskin samplers. These 

 were employed following preliminary probing to determine 

 sharp temperature discontinuities and to identify water layers 

 characterized by elevated chlorophyll and suspended matter 

 levels. Parallel determinations were made of biogenic 

 .component levels, pigment concentration, and traditional 

 organic pollutant concentrations. 



Microzooplankton content was determined conventionally. 

 Immediately upon sampling, 10 ml of the water contained in an 

 oblong chamber were examined under the microscope using a 

 succession of magnifications ranging from low to high. These 

 samples were used to examine and count smaller untrapped 

 forms that perished upon filtering and subsequent treatment of 

 the water. One to three liters of the same sample were then 

 reverse-filtered through a 10- 1 5 ^im mesh in order to isolate the 

 larger protozoa. Samples were likewise taken using nets. 

 Biomass was determined by measuring immobilized infusoria 

 and comparing their shapes with geometric figures and 

 precalculated volume. The specific weight of the organisms 

 was assumed to be the same. The total number of samples taken 

 in the Bering and Chukchi Seas was 350. 



Results 



Bering Sea 



The East Polygon (Frontispiece ) was situated in a complex 

 hydrological setting that included a sharp bottom declivity. 

 Most of the stations had depths of 3.000 m. but the two 

 northernmost ones stood over j ust 1 45 and 2 1 4 m of water. The 

 water contained large amounts of biogenic components: 

 phosphates ranged from 1 .0 to 2.5 |ig al/1 and silicates from 20 

 to 30 |im at/I. The species mix within the polygon was varied 

 and differed little from ambient conditions (Table 1 ). The 

 predominant forms were smaller Strombidia 15-50 |a in size; 

 the principal Tintinnida were Parafavella denticulate, 

 Ptychocylis umula. and Codonellopsis turgescena. Also 

 common were larger Stobilis, Didinium sp.. Mesodinium sp.. 



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