Assessment of functional diversity of macroinvertebrates in Rekawa lagoon, Sri Lanka

Abstract

Macroinvertebrates are important as ecosystem engineers that perform diverse ecosystem functions to sustain ecosystem resilience. This study was conducted to assess the taxonomic and functional diversity of macroinvertebrates and to understand the environmental drivers of their community composition in Rekawa Lagoon. Physico-chemical parameters of water (temperature, salinity, conductivity, pH, dissolved oxygen concentration, total dissolved solids, depth, and Secchi depth) and sediment samples were collected from seven sites in the Rekawa lagoon during September 2023. We identified macroinvertebrate species and calculated taxonomic and functional diversity indexes. The correlation analysis, ANOVA, and redundancy analysis (RDA) were performed to understand variations in macroinvertebrate species composition/diversity indexes and their link to the environmental variables. There were nine species of benthic macroinvertebrates named Grandidierella sp., Gammarus sp., Alitropus typus, Sphaerodema rusticum, Chironomus sp. larvae, Melanoides tuberculata, Nassarius sp., Lymnaea stagnalis, and Nereis sp. were in the lagoon. Shannon-Weiner index in sites 1, 2, and 6 was significantly higher than in site 7. The highest functional richness (Fric) was recorded on site 5 as 16.44±0.73 and the lowest on site 7 as 0.92±0.00. The lowest functional dispersion (Fdis) was also recorded at site 7 as 2.05±0.38 and it was significantly lower than sites 1, 2, 5, and 6. Overall, Site 7 showed significantly lower functional diversity indexes compared to other sites that are characterized by high salinity and conductivity in water. Gammarus sp. were highly correlated with DO concentration. Grandidierella sp. and Chironomus sp. larvae were highly associated with soil organic content. Our study gives insights into how site-specific management practices are needed to manage and conserve the biodiversity of Rekawa Lagoon. Furthermore, we recommend studying the functional diversity of the ecosystems which reveal different and more information than traditional taxonomic indexes to understand our ecosystems.