Community structure of macrobenthic invertebrates in the River Ganga in Bihar, India

Abstract

Benthic macroinvertebrates are reliable indicators of the environmental health of rivers as their distributions vary in response to variations in time and space and available habitats. We investigated the longitudinal and seasonal distribution of macrobenthic assemblages in different habitats (such as vegetated and unvegetated/sand, silt, rock and clay) in the River Ganga. Samples were collected in September 2010, and January, April and June 2011 at four study sites in the heterotrophic Meta-Potamon part extending from Patna through Bhagalpur covering a 249-km stretch of the river. Sampling stations were located along a gradient of macrophytic coverage in marginal water and sediment texture. A total of 69 taxa belonging to 47 families and 23 orders were identified. The data of benthic communities from all samples were subjected to non-metric multi-dimensional scaling (NMDS). NMDS of all data segregated samples on the basis of seasons. The most indicative taxon of monsoon was Culicidae followed by the Corixidae (Sigara distorta) and Micronectidae; whereas, the most indicative taxon in January was Plumatella bombayensis followed by Libellulidae. Highest abundance and species richness were recorded at Bhagalpur. Species richness and abundance were significantly higher in marginal habitats with macrophytes compared to similar habitats without vegetation. Furthermore, differences in species composition were recorded at different substrate types. The persistence of a well-structured macrobenthic community, including families of marine origin in the middle to lower reaches, indicates that the Ganga ecosystem is resilient enough to recover to its pristine ecological value.