The ecological surveys with special reference to the dynamic of macrobenthos in the estuaries have not been comprehensively studied in Sri Lanka. Hence, this study was conducted to determine the correlation between physicochemical parameters and macrobenthos diversity and evaluate the pollution level in the estuary using macrobenthos diversity. Macrobenthos and bottom water samples were collected from randomly selected 19 sampling locations using a Grab and Ruttner sampler respectively from May to July 2015 every month. The results revealed that the macrobenthos consist of 13 families belonging to the phylum Mollusca and Arthropoda. The most abundant families were Planobidae (12200 individuals/m²), Veneridae (11400 individuals/m²), and Haminoidae (11000 individuals/m²). A total of 21 species belonging to 15 gastropoda; five bivalvia and one crustacea were recorded. The Venerid sp and Muricid sp were the most abundant (7240 individuals/m²) and the least abundant (520 individuals/m²) species, respectively. The highest species richness and diversity were reported at PE7, exposed to the canal which mainly carried hospital wastes. The lowest species richness and diversity were reported at PE6, consisting of an underlying rock layer, making it difficult for sediment collection. Macrobenthos diversity showed that the sampling locations were separated into several clusters. BOD and nitrate-nitrogen were the main physicochemical parameters affecting macrobenthos diversity based on the correlation analysis. CCA showed that macrobenthos assemblage was affected by the convergence of anthropogenic and natural stressors presented at the lower and upper estuary parts, respectively. Furthermore, H’ index and Pollution Tolerance Index in the estuary were between 2 and 3 and ≤ 20, respectively. Both indices confirmed that the water quality of the estuary was in poor condition. This study is important to determine the baseline information of the Panadura estuary’s macrobenthos.

斯里兰卡尚未对河口大型底栖动物动态的生态调查进行全面研究。因此，本研究旨在确定理化参数与大型底栖动物多样性之间的相关性，并利用大型底栖动物多样性评估河口的污染水平。2015年5月至7月，每月使用Grab和Ruttner采样器分别从随机选择的19个采样点采集大型底栖动物和底层水样本。结果表明，大型底栖动物由属于软体动物门和节肢动物门的 13 个科组成。最丰富的科是Planobidae (12200 个体/m ² )、Veneridae (11400 个体/m ² )和Haminoidae (11000 个体/m ² )。腹足纲15科，共21种；记录到五种双壳类动物和一种甲壳类动物。Venerid sp 和Muricid sp分别是数量最多的物种（7240 个体/m ²）和数量最少的物种（520 个体/m ²）。据报告，PE7 的物种丰富度和多样性最高，该处暴露于主要输送医院废物的运河。据报告，PE6 的物种丰富度和多样性最低，由下伏岩层组成，难以收集沉积物。大型底栖动物多样性表明采样地点被分成几个簇。相关分析显示BOD和硝态氮是影响大型底栖动物多样性的主要理化参数。CCA表明，大型底栖动物群落分别受到河口下游和上游人为和自然应激源汇聚的影响。此外，河口H'指数和耐污染指数分别在2～3和≤20之间。两项指标均证实河口水质状况较差。这项研究对于确定帕纳杜拉河口大型底栖动物的基线信息具有重要意义。