COMMUNITY STRUCTURE OF MACROZOOBENTHOS IN TWO TYPICAL HABITATS OF CAIZI LAKE DURING THE EARLY PERIOD OF THE “10-YEAR FISHING BAN”

In order to understand the community structure of macrozoobenthos in Caizi Lake during the early period of the “10-year fishing ban”, seasonal investigations of two typical habitats (littoral area and offshore area) were conducted during 2022—2024. The results showed that a total of 83 macrozoobenthos species were collected, belonging to 3 phyla, 7 classes, 17 orders, and 32 families. Among these, Novaculina chinensis and Lamprotula leai were the first recorded national second-class protected species in Caizi Lake. The average density and biomass of macrozoobenthos in the whole survey area were 208 ind./m² and 75.8 g/m², respectively, revealing obvious spatial distribution differences. Biomass was obviously higher in the western lake area and the Changhe River. In terms of species number and predominance, 66 macrozoobenthos species were collected in the littoral area, where Micronectra sp. and Cricotopus sp. were the predominant taxa; 44species were collected in the offshore area, where the Microchironomus sp. and Tanypus sp. were the predominant taxa. Decapoda (shrimp) contributed the highest proportion of the average biomass in the offshore area, whereas, the relative abundance of different functional feeding groups varied greatly. In contrast, Mollusca contributed the highest proportion to the littoral average biomass, and the relative abundance of different functional feeding groups was comparatively constant. As to the statistical analysis, the results of the Two-way ANOVA showed that none of habitat, season, and the interactions of the two significantly affected the biomass of macrozoobenthos in Caizi Lake. Analyses of similarity showed that the macrozoobenthos communities in two typical habitats differed significantly. Although the macrozoobenthos communities in different seasons had a certain overlap, significant differences were revealed. Vegetation coverage, substrate type, and water temperature were the main influencing factors resulting in the differences of macrozoobenthos communities in two typical habitats among different seasons. Comparing with the historical data before the “10-year fishing ban” policy implemented, the species number and standing crop of macrozoobenthos in this study increased obviously. However, the predominant taxa in the offshore area had changed from the coexistence of chironomidae larvae, oligochaeta, and mollusca to chironomidae larvae. Future studies should focus on continuous monitoring to provide a scientific basis for the restoration of macrozoobenthos resources and ecological evaluation of the “10-year fishing ban” policy.