Distribution of Intertidal Organisms in the Shores of Teluk Aling, Pulau Pinang, Malaysia

Abstract

Distribution of intertidal organisms were analysed at the sandy and rocky shores of Teluk Aling, Pulau Pinang during the spring tides on August 4 and September 11, 2007. Four higher taxa were recorded at the sandy shore including Polychaeta, Crustacea, Mollusca and Echinodermata with the highest abundance by phylum Mollusca: 89.4%. The species found to be the most abundant was the button snail, Umbonium vestiarum at the sandy shore during both sampling periods with the highest abundance measured by Importance Species Indices (ISI) at both middle and lower zones with 39.84 and 36.59, respectively. At the rocky shore, assemblages of Crustacea, Mollusca, Cnidaria as well as Polychaeta were recorded and Crustaceans appeared to be the most abundant with 98% of total composition. At the rocky shore, Cthamalus sp. showed the highest ISI value among other organisms with 64.67 for the first sampling and 65.41 for the second sampling. The highest diversity, measured by Shannon-Wiener index, H' was observed at middle zone of sandy shore for both sampling periods (0.951 for first sampling and 1.422 for second sampling) and higher evenness as measured by Pielou Evenness index, J' with 0.207 and 0.314 respectively. In contrast, the lower zone at the rocky shore appeared to be more diverse as compared to middle zone with H' = 1.738 for the first sampling and 2.309 for the second sampling. Evenness was also higher with 0.673 and 0.769, respectively. This study also showed that particle size distribution and organic matter along the intertidal gradient influenced the distribution pattern of intertidal organisms at sandy shore. Based on Pearson correlation analysis, the organic content showed a significant correlation with particle size distribution (p < 0.01). Lower zone had finer sand and the highest percentage of organic content, therefore could sustain a greater number of species as compared to the sterile upper zone as a result of coarse sand and less organic content. The Isopoda Eurydice sp. was the only species that could withstand the unstable conditions within this zone. The rocky shore showed the most striking zonation pattern compared to sandy shore where there were considerable overlaps of species in their zonation along the intertidal gradient, although organisms may remain quite separate in the sand column.