Community Structure of Macrozoobenthos from Upstream to Downstream of Purba District, North Sumatra

Abstract

The community and composition of benthic macrofaunal species are determined in three sampling stations from upstream to downstream in Purba District. Sampling was performed in November 2021 during the rainy season. The results showed a population shift from upstream to downstream based on the predominance of insect and mollusk groups. The upstream was populated by Chironomus sp. (Insecta: Chironomidae) with 124 ind/m2, followed by Helicorbis sp. (Mollusca: Planorbidae) with 90 ind/m2, and Cambarincola sp. (Oligochaete) with 89 ind/m2. Helicorbis sp. with 298 ind/m2 had the highest density in the midstream, followed by Cambarincola sp. (Oligochaete: Branchiobdllidae) with 285 ind/m2, and Melanoides sp. (Mollusca: Thiaridae) with 184 ind/m2. Furthermore, Melanoides sp. (533 ind/m2), Helicorbis sp. (475 ind/m2), and Limnodrilus sp. (288 ind/m2, Oligochaete: Naididae) were the three most dominant taxa in the downstream. The Shannon's diversity index (H') in upstream and downstream were both 2.12, while the downstream index was 1.90. There was a significant difference among stations based on relative taxa density (F2,8 = 14.16, p = 0.005). Therefore, further research on other taxa groups, such as plankton and fish, should be conducted to increase the understanding of the anthropogenic effect on stream conditions in the Purba District.