Ecological health assessment of a coastal ecosystem: Case study of the largest brackish water lagoon of Asia

This study focuses on the ecological health assessment of Chilika, a shallow lagoon present in east coast of India, through nutrient stoichiometry and trophic state index (TSI). Multivariate statistical analysis such as ANOVA, Pearson's correlation, Principal Component Analysis (PCA), and Discriminant Analysis (DA) were employed for data interpretation. Nutrient stoichiometry revealed that the Chilika Lagoon experiences phosphorus limitation with regard to nitrogen and silicate (N:P:Si = 16:1:16) throughout the study period. As per the computed TSI values, the southern sector (SS), central sector (CS), and outer channel (OC) were assigned with a mesotrophic status, whereas the northern sector (NS) was assigned with the eutrophic status. From PCA, total nitrogen was found to be negatively correlated with salinity and positively correlated with silicate, thus indicating that the major source of nitrogen in the lagoon was freshwater ingress by rivers with high silicate content. DA indicated that it was successful in discriminating the groups as predicted.