Monitoring of water quality variation trends in a tropical urban wetland system located within a Ramsar wetland city: A GIS and phytoplankton based assessment

Abstract

The present study, was conducted in an urban wetland system within a Ramsar wetland city in Sri Lanka to study the effectiveness of using the Geostatitical and multivariate statistical techniques together with phytoplankton based biological indices to assess the wetland ecological status. Seven sites were selected from the wetland and the water quality parameters and the diversity and abundance of phytoplankton at each site was assessed. Thirteen species of phytoplankton from Class Cyanophyceae, 18 species from Class Chlorophyceae and six species from class Bacillorphyceae were recorded during the study. There were significant spatial variation of water quality parameters and phytoplankton composition among the study sites. Principal component analysis for water quality and phytoplankton distribution was performed. Palmers index, percentage biological index and the limnological condition index was calculated based on water quality and phytoplankton data. According to the classification based on Palmers index the sites located in the northern portion ofthe wetland indicated high organic pollution, while otier sites indicated no or less less organic pollution. According to the limnological categorization based on pollution index, %BI and LICOI, the northern sites were categorized as sites with poor ecological quality and as severely contaminated sites. The sites in the southern portion of the wetland were categorized as moderately polluted sites with acceptable limnological conditions for the ecologicaI functions to occur within tolerable limits. Water quality prediction maps for the wetland was developed using geostatistical methods and the water quality trends also agreed with the results of the biological indices and the results of the multivariate statistics. The results indicated that the geostatisical and multivariate techniques together with the Palmers index, percentage biological index and the limnological condition index can serve as important tools for monitoring the water quality trends in tropical urban wetland ecosystems.