Selecting a suitable diversity index for a tropical Ramsar wetland site

Abstract

AbstractWetlands are under threat from the inflow of urban pollutants on a daily basis. The phytoplankton community is the most affected by increasing eutrophication. Biodiversity based on species richness and evenness can reflect the phytoplankton community composition, as well as describing the water pollution impacts on biotic communities. Eutrophication is a major problem in tropical wetland systems because they receive various waste discharges. Therefore, an attempt was made in this study to analyse the eutrophication status of a tropical wetland (part of the Vembanad Wetland in Cherthala‐Aroor‐Edakochi coastal belt, Kerala) that is being affected by seafood effluent discharges. Alpha indices (Shannon–Weiner Diversity Index; Simpson Index) and beta diversity (Jaccard Index and Sorensen Index) were used to identify appropriate diversity index in a eutrophic environment. Analysis of the plankton populations indicated significant variations among the wetland sampling sites, with the highest percentage of pollution indicators observed in the interconnected channels than in the main portion of the wetland. The results of this study also reveal that a dangerous level of reduction in Chlorophyceae occurred which, in turn, affects the wetland primary productivity. If this situation continues, the wetland will become dominated by fewer, more pollution‐tolerant species over time, indicating serious attention must be given to stopping the loss of diversity in the wetland. This study revealed that β diversity indices are more suitable for studying diversity in a eutrophic wetland system than α diversity indices, mainly because β diversity indices indirectly consider the pollution indicator species, whereas the Shannon Index fails to do so. This study also notes the importance of using the Simpson Index over the Shannon Index for eutrophic waterbodies.