SPECIES COMPOSITION AND QUANTITATIVE DISTRIBUTION OF LARVAE OF DRAGONFLIES (ODONATA) IN THE NEW ECOLOGICAL CONDITIONS OF THELAKE AGGOL
The paper presents newdata on species composition, number and distribution of the larvae of dragonflies (Odonata) in new environmental conditions ofthe different habitats of in the lake Aggol. Field works conducted in 2011-2012 in the lake Aggolresulted in the rearings of 28 species and forms of dragonfly larvae. Six of these Coenagrion concinnum Joh., C. armatum Charp., Aeschna viridis Eversman, Sympetrum striolatum Charp., S. sanguineum Müll., S. meridionale Selys. arenew to the lake. Species Coenagrion concinnum and C. armatum were found in winter, spring and autumn of 2011 and winter and autumn of 2012; Aeschna viridi s in winter and autumn of 2011; Sympetrum striolatum - winter, spring and autumnof 2011; S. sanguineum in winter and autumn of 2011-2012; S. meridionale inwinter and spring of 2011-2012.The widest distributed species belong to the genera Coenagrion, Aeschna и Sympetrum. The maximum development of larvae of dragonflies was registered in winter (106 ind./m2, 1,10 g/m2) and minimum in summer (12 ind./m2; 0,14 g/m2). Ecology of the fauna is studied in detail.In the study period (2011-2012) the number of species of dragonfly larvae reaches a minimum in summer (6 species), and the maximum (27 species) in winter.Species Coenagrion scitulum, C. vernale, C. puealla, C. mercuriale, Anax imperator, Sympetrum flaveolum are observed in the lake in all seasons andare dominated by widespread. It should be noted that the decrease in the number of larvae of dragonflies in the summer, especially at depths of up to 0.5 m is due to their intensive consumption by fish and water birds and emergence of adultdragonflieswhich leave the lake. On the other hand, in summer period, the volume of oxygen in shallow water of the lake Aggolis greatly reduced, and as a result of evaporation of water, the amount of salts in wateris increased. In such circumstances, the probability of occurrence of freshwater organisms in the benthosis naturally decreased.Average annual number of dragonfly larvae per square meter of the lake Aggolin 2011 was 88 ind./m2, and biomass - 0.31 g/m2. During this period, the maximum development of the larvae of dragonflies observed in winter (141 ind./m2, 0.50 g/m2), and the minimum - in the summer (25 ind./m2; 0.10 g/m2). In contrast to 2011, in 2012 the average annual number of dragonfly larvae per square meter lake was 66 ind./m2, and biomass -0.24 g/m2. It is shown that the maximum development of dragonfly larvae was observed in winter (126 ind./m2;0.47 g/m2) and the minimum (11 ind./m2, 0.03 g/m2) - during the summer season.The study of the distribution of larvae of dragonflies on specific habitats of the lake revealed their maximum development on plant and silty habitats, and the minimum - on black silty sand.Changes in biomass of benthic organisms as well as larvae of dragonflies, which developed very poor isanalyzed. The index of the average biomass of dragonfly larvae per square meter of lake in the 60s was 0.27 g/m2 in 70s - 0, 20 g/m2, in 80s - 0.13 g/m2, and in 2011-2012 - 0.28 g/m2. Poor development of dragonfly larvae in the lake Aggolis characterized, on the one handwith their intensive consumption by fish and water birds andon the other hand - the steady worsening of the environmental conditions of the lake.