The Influential of Physico-chemical Parameters on the Distributions of Oligochateas (Limnodrilus sp.) at the Polluted Downstream of the Tropical Langat River, Peninsular Malaysia

The influential physico-chemical parameters on the spatial and temporal distribution of oligochateas (Limnodrilus sp.) at the polluted downstream of Langat River were studied in comparison to the unpolluted upstream for 10-months sampling from March 1998 to February 1999. Based on the correlation analysis (CA) and multiple stepwise regression analysis (SRA), the distribution, abundance and density of Limnodrilus sp. were almost consistent during the ten time samplings from April 1998 to February 1999. Based on CA, the density and distribution of Limnodrilus sp. correlated negatively with the pH and dissolved oxygen (DO) while positively correlated with conductivity, biological oxygen demand (BOD), NO3, NH3, total suspended solids (TSS), chemical oxygen demand (COD) and dissolved concentrations of Cu and Zn. Based on SRA, most of the above parameters are selected as influential factors in affecting the distribution and presence of Limnodrilus sp. on the tropical river. This indicated that the Limnodrilus sp. is a pollutant resistant worm since they can survive in the poor water quality ecosystem. These results based on CA and SRA signified the resistance and tolerance of Limnodrilus sp. survived at the polluted ecosystem of the tropical river. Hence, Limnodrilus sp. is a good bioindicator of polluted rivers in the tropical ecoregion. @JASEM Benthic macroinvertebrates are found in all rivers and they play crucial roles in organic matter dynamics and trophic energy transfer in river ecosystem (Hershey and Lamberti, 1988). As a group, they are the primary food source for most stream and river fishes. Their taxonomic, habitat and life-history diversity ensure that an array of food types is available to many fish species over the entire annual cycle. They also conduct the less apparent but no less important work of decomposing leaf litter and small particles of organic debris on the stream bottom or in the water column and of grazing stream algae, fungi and bacteria. Benthic macroinvertebrates are of importance to aquatic biologists because they can indicate pollution effects on the river ecosystem. In particular, environmental quality has been assessed with respect to oligochaete species ecology by numerous authors (Brinkhurst, 1967; Brinkhurst and Jamieson, 1971; Lang, 1985; Mason and Parr, 2003). These authors based their findings on the relative abundance of species that are classified as intolerant, moderately tolerant and very tolerant of organic pollution. The changes which take place in benthic species composition with polluted conditions form the basis on which biotic indices of water quality are formulated. In this regard, certain aquatic oligochaetes are of such importance in the biotic index that they are referred to as ‘indicator species’. Earlier report by Azlina et al. (2006) found that the biodiversity of macrobenthic invertebrates of Langat River were affected by physico-chemical factors. However, detailed study and discussion on how abiotic factors influence the distribution of the resistant Limnodrilus sp. has not yet been discussed in the literature. The worm species, Limnodrilus sp. was focused in this study because of two reasons. First, it has been suggested as a bioindicator of polluted river ecosystem in Peninsular Malaysia (Yap et al., 2003a; Azlina et al., 2006). However, its potential use for the bioindication purpose needs further validation. Second, the tolerant worm is a very interesting species from ecotoxicological point of view but how is it to be influenced by physicochemical factors are not clarified in the literature. Therefore, the objectives of this study were 1) to determine the relationships between the distribution of Limnodrilus sp. and physico-chemical factors by using correlation analysis (CA) and 2) to find out the most influential physico-chemical factors affecting the distribution of Limnodrilus sp. by month by using stepwise regression analysis (SRA). The use of SRA had been used to find out the most influential allometric variables affecting the accumulation of heavy metals in Perna viridis (Yap et al., 2003b). MATERIALS AND METHODS Description of the study area: Samplings were conducted from March 1998 to February 1999 at eight sampling sites during day time along the Langat River Basin which is located in Selangor, Peninsular Malaysia (Figure 1). The water flows from the upstream area in Hulu Langat until Kuala Selangor at the downstream area where the Langat River becomes the main river in the basin which flows in a southwesterly direction and drains into the Straits of Malacca. The upstream stations covering stations 1 to 4 were clean ecosystem and there was no oligochaetes found in this part of the river. These four sites were characterized by the presence of cobbles and pebbles and sometimes sand and gravel. There was generally high vegetation coverage at the JASEM ISSN 1119-8362 All rights reserved J. Appl. Sci. Environ. Mgt. September, 2006 Vol. 10 (3) 135140 Full-text Available Online at www.bioline.org.br/ja The Influential of Physico-chemical Parameters on... Yap, C K; Rahim Ismail, A; Azrina, M Z; Ismail, A; Tan, S G 136 four upstream sampling stations. The other four downstream stations (Stations 5-8), were known to receive anthropogenic impacts due to domestic wastes, paper factory, oil palm plantation and township. Fig 1: Sampling stations along the Langat River. Water Quality Measurement and Worm Sampling: Triplicates of the physico-chemical parameters of the river were recorded directly at each sampling site. These were temperature, river depth, river width, conductivity, pH and dissolved oxygen (DO). River depth and width were measured by direct observation (meter ruler and measuring tape for river width and core for river depth), conductivity and temperature by a YSI meter Model 33, pH by a pH meter Beckman Model F8 253 and dissolved oxygen (DO) by a YSI oxygen meter Model 57. Water samples were collected and analysed for total suspended solids (TSS), dissolved concentrations of Cu and Zn, nitrate (NO3) and ammonia (NH3), biological oxygen demand (BOD) and chemical oxygen demand (COD) according to Standard Methods. Limnodrilus sp. were sampled by using a corer sampler (20.83 cm). The worms were placed in plastic bottles and were preserved with 80% of ethanol. In the laboratory, the worms were sorted by the naked eyes. Sorting of smaller fauna was done under a dissecting microscope with the aid of watchmaker forceps. All the sorted samples were preserved in new 80% ethanol before using the appropriate taxonomical keys. The keys used in this study was Brinkurst and Jamieson (1971) for Oligochaeta identification. Transformation of Data: In order to stabilize the variance so that the data frequency distribution was close to the normal distribution (Sheldon and Haick, 1981), all the physico-chemical data were log10 transformed while the density of Limnodrilus sp. were fourth-root transformed. Afterwards, Spearman’s correlation analysis (CA) and multiple stepwise regression analysis (SRA) would be carried out based on the transformed data to find out the Sampling area at