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The difference of the evenness index (DE′) is offered for an assessment of the ecological state of zoobenthos communities. The index is deduced on the basis of the Shannon indexes calculated according to abundance and biomass data and differentiates between these informational estimations (Shannon diversity) of evenness of species in any given community. Conclusions made by Pianka about the predomination of organisms with r and K life strategy in communities impacted and unimpacted by ecological stress, as well as the ABC-curves method suggested by Warwick, were used as the basis of the functioning mechanism for the suggested index. The examples of index applicability are demonstrated by an assessment of materials collected in freshwater, estuarine, and marine waterbodies during one-time surveys and long-term monitoring observations. The results are compared with zoobenthos assessments made on the basis of some other indexes. Conclusions concerning the efficiency of the DE′ have been made and some of its advantages over other indexes are shown.

Feeding selectivity and assimilability of the Baikal invader Gmelinoides fasciatus (Stebbing, 1899) in Lake Ladoga at feeding by various types of plant and animal food have been studied experimentally. The food demand has been assessed at different assimilation levels. Freshwater shrimp G. fasciatus has been shown to have distinct selective capacity with respect to different kinds of plant and animal food.

The feeding of the Baikal invader Gmelinoiudes fasciatus (Stebbing, 1899) in Lake Ladoga has been studied based on field and experimental data. The food spectrum of this amphipod was revealed; it includes many plant and animal species. Differences in the feeding of G. fasciatus living in different littoral biotopes were shown. The ecological and physiological rations of this species were determined. The effect that the bottom substrate has on the feeding rate of the amphipod was estimated. The introduction of G. fasciatus into Lake Ladoga provided a more adequate utilization of the energy accumulated by the primary producers and its transfer to higher trophic levels. This Baikal amphipod occupied a niche that had been, in effect, vacant. This made the invader capable of maintaining the quantitative parameters of its population at a very high level, and it largely reorganized the flow of matter and energy in the littoral zone of the lake.

Dynamics of the size-age structure and sexual structure of the population and characteristics of reproduction and life cycle have been studied in the Baikal invader Gmelinoiudes fasciatus (Stebbing, 1899) in Lake Ladoga. The studied characteristics display both similar features with and differences from populations of this species in other waterbodies. It is found that the size and age structure of the G. fasciatus population changes in the circannian aspect under the influence of complex of environmental factors. The sexual structure of the population is dynamic, but a sex ratio of approximately 1: 1 is maintained in the circannian cycle. Six principal periods of hatching are recognized. The main factor determining the timing of the start and termination of the reproduction period in G. fasciatus is temperature. The weight of eggs oviposited by the female over the whole life cycle (about 21.5 cal in the energy equivalent) amounts to about 60% of the female body weight.