Pollution Sensitive Taxa Research Articles

Benthic macroinvertebrates as indicators of water quality: A case study of estuarine ecosystems along the coast of Ghana

Increasing human activities in coastal areas of Ghana have led to the degradation of many surface waterbodies, with significant consequences for the ecosystems in the affected areas. Thus, this degradation extremely affects the health of ecosystems and disrupts the essential services they provide. The present study explored the use of benthic macroinvertebrates as an indicator of estuarine degradation along the coast of Ghana. Water and sediment samples were collected bimonthly from Ankobra, Kakum and Volta estuaries for physicochemical parameters, nutrients and benthic macroinvertebrates. The findings revealed the dominance of pollution-tolerant taxa such as Capitella sp., Nereis sp., Heteromastus sp., Tubifex sp., Cossura sp. and Chironomous sp. in Kakum Estuary while pollution-sensitive taxa such as Scoloplos sp., Euridice sp., Lumbriconereis sp. and Pachymelania sp. in the Volta Estuary. The species-environment interactions showed dissolved oxygen, temperature, salinity, orthophosphate, nitrates, ammonium, electrical conductivity, turbidity, and chemical oxygen demand as the most significant parameters that complement the use of benthic macroinvertebrates as indicators of environmental quality in the studied estuaries. There were correlations of some benthic macroinvertebrate taxa with environmental factors in the estuaries suggesting low, moderate and high levels of pollution in the Volta, Kakum and Ankobra estuaries, respectively. Nevertheless, the study finds Kakum Estuary to be the ecologically healthiest estuary than the Volta and Ankobra Estuaries. Therefore, the study has shown benthic macroinvertebrates as a key indicator of ecosystem health alterations, and it is recommended that they should be incorporated with other environmental data for pollution monitoring in Ghanaian coastal waters.

Aquatic Insects as Bioindicators of Water Quality in the Achenkovil River, Kerala, India.

The origin of the Achenkovil River, the Devarmalai of Western Ghats, is within the Konni reserve forest of Pathanamthitta district, flowing through Pathanamthitta, Kollam, and merging with the Pamba river in the Alappuzha district. This study included the spatial variation of aquatic insect fauna with respect to water quality. The bottom water samples and insect fauna were collected bimonthly using a Niskin sampler and D-frame nets for a period of one year (February 2019 to January 2020). The study yielded 10736 insect fauna under 8 orders, 21 families, 35 genera, and 36 species. How the quality of the water affects biodiversity of aquatic insects was examined using multivariate statistical techniques (PCA and CCA) and Pearson's correlation coefficient. The findings showed that the upstream portion of the river has a remarkable diversity and quantity of aquatic insect species. The major insect group in the collected sample was ephemeroptera. There were no pollution-sensitive taxa in the middle stream or downstream portions of the river, which suggests that the water quality was declining. The middle stream and downstream sections of the river did not contain any pollution-sensitive taxa, indicating deteriorating water quality. Human-caused factors like washing, cleaning cars, and washing cattle and disposal of garbage are common in these regions. Because most aquatic insects are sensitive to environmental fluctuations, they can be used as an efficient tool in biomonitoring studies.

Drying niches of aquatic macroinvertebrates identify potential biomonitoring indicators in intermittent and ephemeral streams

Intermittent rivers and ephemeral streams (IRES) compose the majority of draining networks on Earth, supporting a unique fraction of biodiversity. Despite their high ecological value, IRES are increasingly threatened by global change and require appropriate biomonitoring and restoration tools. However, indices and indicators used in routine biomonitoring programs are often confounded by drying effects. This occurs because most pollution-sensitive taxa are lost over drying gradients, limiting the utility of current biomonitoring tools in IRES. To address this challenge, there is a need to evaluate which taxa should be used to calculate biomonitoring metrics and indicators over the different portions of the drying gradient. Here, using high-resolution drying data from 33 unpolluted streams, we explored the drying preferences of macroinvertebrates to identify their potential as biomonitoring indicators in IRES. To do this, we characterized macroinvertebrate drying niches and identified those with drying resistance and sensitivity preferences. Next, we evaluated the capacity of functional traits to predict drying specialization and affinity. Finally, to identify potential biomonitoring metrics and indicators for IRES, we evaluated how drying influenced the density, relative abundance and richness of taxa in drying-sensitive and drying-resistant niches. Our results identified three macroinvertebrate groups with drying-resistant niches (partly tolerant, generalist and specialist taxa) and one group of drying-sensitive taxa. We also found that functional traits had a limited capacity to represent differences in drying niches, with shredding trophic preferences and body size showing the strongest correlations. In addition, we observed that the density, relative abundance and richness of drying-resistant taxa were less influenced by drying intensity than those of drying-sensitive taxa. Finally, we found that some pollution-sensitive taxa with partial (e.g., Lepidostoma), moderate (e.g., Corduliidae) or high drying tolerance (e.g., Nemoura) can serve as potential indicators in IRES. Taken together, our results demonstrate that characterizing drying niches can be a useful strategy for developing biomonitoring tools in IRES and for highlighting the limitations of taxonomic and trait-based approaches.

Responses of benthic macroinvertebrate communities in tropical Asian streams passing through an industrial zone

ABSTRACT Industrial zones have been key drivers of growth across Asia but are also the source of water quality deterioration in surrounding rivers and streams. This study examined the effects of industrial zone located at the San Cristobal sub-catchment of Laguna de Bay, the Philippines on the spatiotemporal variation in water quality and benthic macroinvertebrate communities. Sampling sites were established in upstream and downstream sections of two tributaries of San Cristobal River, and the main channel of Diezmo River, and were sampled in 2018 during dry (February and April) and rainy (June and October) seasons. Results showed significant spatial difference with declining water quality (low dissolved oxygen; high levels of ammonia-nitrogen, phosphate-phosphorus, and total suspended solids) at the downstream sites. Consequently, benthic macroinvertebrates responded via change in community structure and composition (decline in pollution-sensitive taxa from upstream through downstream) to water quality degradation related to industrial land use downstream. Furthermore, seasonal variation was observed in benthic macroinvertebrate communities due to the absence of spate-induced disturbance, allowing benthic macroinvertebrates to proliferate in the rainy season. Findings of this study reveal that benthic macroinvertebrates can be used as bioindicators in the evaluation of the ecological integrity of surface river and stream systems that pass through industrial zones.

The effects of water chemistry and lock-mediated connectivity on macroinvertebrate diversity and community structure in a canal in northern England

Freshwater ecosystems are under threat from habitat loss, partly due to urban expansion. However, some elements of urban freshwaters are already integral parts of the urban landscape and so are more resilient to loss, representing opportunities for the enhancement of freshwater resources within cities. This study investigated the biodiversity value of the Leeds-Liverpool Canal in Leeds, UK, in relation to its landscape context. Specifically, we tested the hypotheses that (i) biodiversity value is lowest nearest to the urban core, and (ii) the pattern of canal locks structured ecological communities. Nutrients, metals and dissolved carbon all existed at relatively low concentrations, contrary to what is often seen in urban water bodies, although concentrations were higher in the urban core. This gradient of chemical stress was associated with a decline in macroinvertebrate diversity towards the city centre, which manifested as pollution-sensitive taxa being excluded from this area. Community structures were found to vary between groups of sampling sites separated by locks, suggesting that locks may act as barriers for aquatic invertebrates by restricting dispersal. The results in this study indicate that canals in urban areas can be high-quality habitats, despite the associated anthropogenic stressors, and locks may represent a unique model for researching relationships between connectivity and community structure.

Macroinvertebrate Assemblages in Selected New Jersey Springs

Springs are often very diverse aquatic systems that have important ecological functions. This study documented water quality and macroinvertebrate assemblages, while providing a baseline inventory, in 6 New Jersey springs which varied by discharge (4–16,990 L/min). We collected aquatic macroinvertebrates using a Hess sampler quarterly from August 2014 to September 2015. This study documented diverse macroinvertebrate communities, with a total of 2383 macroinvertebrate individuals encompassing 103 taxa. The numerically dominant taxa present were Diptera, Amphipoda, and Coleoptera. No single genus or species were present at all 6 spring sites. We collected 2 taxa that have not been previously documented in New Jersey: Neoplasta and Cecidomyiidae. Each spring exhibits unique characteristics; analysis of the data presented in this study focuses on correlation between datasets. Correlations suggest that springs with higher discharge house a more diverse macroinvertebrate community including more pollution-sensitive taxa. For future study, more data is needed to pinpoint the causation of macroinvertebrate metrics related to human disturbance and urbanization. Continued monitoring of these springs is recommended due to their ecological importance and to study the long-term water quality trends.

Macroinvertebrates and its impact in assessing water quality of riverine system: A case study of Mahanadi river, Cuttack, India

The aim of this study was to identify the diverse macroinvertebrates present in river Mahanadi, Cuttack in India and to evaluate the role of macroinvertebrates in assessing river water quality and pollution level. We conducted field study of the river at Cuttack (85°46’21.29” E 20°28’15.81” N & 85°49’45.23” E 20°30’50.00” N) during 2013-2014 and collected aquatic invertebrate samples from 12 stations on river basin. The samples were analysed to explore the various families of Macroinvertebrates communities present in river Mahanadi, to examine the status of water quality of the river using biological indicators, to determine whether there are relationships between water chemistry and presence of typical macroinvertebrates and to develop a Macroinvertebrates based index to bio-assessment of Mahanadi River. A total of 484 taxa were identified and about 244 taxa of bivalves and 184 taxa of gastropods were collected. Presence of high number of pollution tolerant taxa and pollution sensitive taxa (Ephemeroptera, Plecoptera, Tricoptera and Chironomidae) indicated increased risk of water pollution and calculated biotic score (8), biological monitoring working party (BMWP) score (52), average score per taxa (ASPT) score (4) and macroinvertebrate-based index (MBI) value indicated moderate pollution level in the river. We recorded pH, total hardness, dissolved oxygen (DO), biological oxygen demand (BOD), total nitrite, chloride and total phosphate of water and physico-chemical parameters supported the values of biological assessment of water quality. Studying macaroinvertebrates helped to gain knowledge about aquatic faunal biodiversity in river Mahanadi and to develop a method for diagnosis of the health of river ecosystem and for measuring water pollution level.

Effects of Ecohydraulic Bank Stabilization Structures on Bank Stability and Macroinvertebrate Community in Surabaya River

There were 18 accelerated erosion sites identified along 7 km of Surabaya River Fishery Sanctuary Area. A model of ecohydraulic bank stabilization was applied to reduce bank erosion in Surabaya River at Gresik Regency Indonesia. The model is combination of reprofiled and revegetated bank with rock toe reinforcement and addition of log groynes. Various native plant species were planted and naturally grown to establish multi-strata littoral vegetation structure. This study assessed effects of ecohydraulic bank stabilization on bank morphology, near bank velocity and littoral macroinvertebrate community during September 2014 to August 2016. The study found that rock toe enforcement, log groynes and reprofiled bank slope could stabilized the eroded bank, and littoral vegetation formation reduced near bank velocity at restored sites. There were 31 families of macroinvertebrate found in Surabaya River with high abundance of moderately pollution sensitive taxa Atyidae and pollution tolerant taxa Corixidae, Chironomidae and Tubificidae. The taxa richness, diversity index and abundance of sensitive and moderately sensitive macroinvertebrate group were increased after application of ecohydraulic bank stabilization at restored area. The results shown that ecohydraulic bank stabilization structure provides multi-benefits in improving bank stabilization against erosion and providing new micro-habitats for biotic community. Keywords: ecohydraulic bank stabilization , macroinvertebrates, riparian restoration

Combined effects of water stress and pollution on macroinvertebrate and fish assemblages in a Mediterranean intermittent river

Water stress is a key stressor in Mediterranean intermittent rivers exacerbating the negative effects of other stressors, such as pollutants, with multiple effects on different river biota. The current study aimed to determine the response of macroinvertebrate and fish assemblages to instream habitat and water chemistry, at the microhabitat scale and at different levels of water stress and pollution, in an intermittent Mediterranean river. Sampling was conducted at high and low summer discharge, at two consecutive years, and included four reaches that were targeted for their different levels of water stress and pollution. Overall, the macroinvertebrate fauna of Evrotas River indicated high resilience to intermittency, however, variation in community structure and composition occurred under acute water stress, due to habitat alteration and change in water physico-chemistry, i.e. water temperature increase. The combined effects of pollution and high water stress had, however, pronounced effects on species richness, abundance and community structure in the pollution impacted reach, where pollution sensitive taxa were almost extirpated. Fish response to drought, in reaches free of pollution, consisted of an increase in the abundance of the two small limnophilic species, coupled with their shift to faster flowing riffle habitats, and a reduction in the abundance of the larger, rheophilic species. In the pollution impacted reach, however, the combination of pollution and high water stress led to hypoxic conditions assumed to be the leading cause of the almost complete elimination of the fish assemblage. In contrast, the perennial Evrotas reaches with relatively stable physicochemical conditions, though affected hydrologically by drought, appear to function as refugia for fish during high water stress. When comparing the response of the two biotic groups to combined acute water stress and pollution, it is evident that macroinvertebrates were negatively impacted, but fish were virtually eliminated under the two combined stressors.

Filling in the Gaps for Aquatic Ecosystem Conservation – Biomonitoring forBaseline Information and Capacity Building in Meghalaya, India

This paper describes a stream biomonitoring program that builds capacity in undergraduate college students in the field of freshwater ecology and conservation. The program involves sampling of aquatic macroinvertebrates and hydrological parameters in streams of the state of Meghalaya, India. Several colleges from Shillong initiated short-term, one-year and long-term biomonitoring of streams in East Khasi Hills and Ri-Bhoi districts. Nine stream locations sampled over October-December in 2014 provided a snapshot of physical and biotic conditions, thus enabling the examination of spatial trends in water quality parameters and aquatic biota. A year-long sampling study from 2014-2015 provided a seasonal view of stream parameters at Lwai (clean) and Umkaliar (moderately polluted) streams. Results from both sampling sets suggest that turbidity negatively affected the richness of pollution sensitive taxa. Dissolved Oxygen values were lower in polluted streams and were non-significantly lower in summer than in winter. After an initial training in the field, the sampling was conducted by college students under supervision from their lecturers. Data obtained on macroinvertebrates adds to the sparse information available on stream ecosystems in the biodiversity-rich northeast Indian region. We hope the paper provides a template for monitoring of vital ecosystems in this and similar regions.

Global climate change in large European rivers: long‐term effects on macroinvertebrate communities and potential local confounding factors

Aquatic species living in running waters are widely acknowledged to be vulnerable to climate-induced, thermal and hydrological fluctuations. Climate changes can interact with other environmental changes to determine structural and functional attributes of communities. Although such complex interactions are most likely to occur in a multiple-stressor context as frequently encountered in large rivers, they have received little attention in such ecosystems. In this study, we aimed at specifically addressing the issue of relative long-term effects of global and local changes on benthic macroinvertebrate communities in multistressed large rivers. We assessed effects of hydroclimatic vs. water quality factors on invertebrate community structure and composition over 30 years (1979-2008) in the Middle Loire River, France. As observed in other large European rivers, water warming over the three decades (+0.9 °C between 1979-1988 and 1999-2008) and to a lesser extent discharge reduction (-80 m(3) s(-1) ) were significantly involved in the disappearance or decrease in taxa typical from fast running, cold waters (e.g. Chloroperlidae and Potamanthidae). They explained also a major part of the appearance and increase of taxa typical from slow flowing or standing waters and warmer temperatures, including invasive species (e.g. Corbicula sp. and Atyaephyra desmarestii). However, this shift towards a generalist and pollution tolerant assemblage was partially confounded by local improvement in water quality (i.e. phosphate input reduction by about two thirds and eutrophication limitation by almost one half), explaining a significant part of the settlement of new pollution-sensitive taxa (e.g. the caddisfly Brachycentridae and Philopotamidae families) during the last years of the study period. The regain in such taxa allowed maintaining a certain level of specialization in the invertebrate community despite climate change effects.

Ecological Integrity of a Peri-Urban River System, Chiraura River in Zimbabwe

Ecological integrity of a peri-urban river system facing a plethora of anthropogenic pressures was assessed through multivariate analysis of physicochemical parameters correlated to the resident macroinvertebrate community. Monthly collection of macroinvertebrates and concurrent measurement of the physical and chemical parameters (dissolved oxygen concentration, percentage saturation of oxygen, pH, temperature, electrical conductivity and salinity) of water was done over a period of 5 months from November 2011- March 2012 in six sites across the Chiraura River. Macroinvertebrates were collected using the kick-net sampling technique, identified up to family level and enumerated at each site. Biodiversity indices were calculated for each site following the South African Scoring System version 5 (SASS5). A total of 1209 macroinvertebrates belonging to 49 families and11 orders were recorded in the Chiraura River. Most pollution sensitive taxa were found at sites 3 and 4 and the most pollution tolerant families were found at sites 1, 5 and 6. Sites4 and 5 of Chiraura River were the least polluted. Unsustainable anthropogenic activities, including industrial, domestic and urban agricultural activities affects water quality of Chiraura River. This is mainly through run-off and increased effluent to the river making routine water quality monitoring imperative.

Integrated Constructed Wetlands (ICW): Ecological Development in Constructed Wetlands for Manure Treatment

In Flanders (Belgium), treatment systems based on constructed wetlands have been successfully implemented to treat the liquid fraction of separated pig manure, resulting in water that meets the stringent discharge criteria. As these systems have proven their nutrient removal performance, attention has moved towards the concept of biodiversity development from a perspective of Integrated Constructed Wetlands (ICWs). The spontaneous colonization of constructed wetlands with macroinvertebrates was examined to quantify the added biological value presented by a farmyard treatment wetland. In total, 17 taxa were found. The diversity of macroinvertebrates increased along the water treatment path in the system and was higher in summer than in autumn. Several pollution sensitive taxa like Orthetrum, Ischnura, and Cloeon were found at the last basins of the treatment wetland chain. Most species were insects, since their adults can easily aerially colonize these recently constructed systems. Water quality was assessed using the Multimetric Macroinvertebrate Index Flanders (MMIF), and showed a general increase towards the end of the treatment. The MMIF increased significantly with decreasing nutrient levels. ICWs adequately combine the treatment of wastewater with supporting and enhancing biodiversity in agricultural landscapes.

An Assessment of the Effect of Industrial and Sewage Effluent on Aquatic Invertebrates: A Case Study of A Southern Urban Stream, Zimbabwe

The impact of industrial effluent discharged in Mazai stream was assessed through physical-chemical parameters and also by bio-monitoring of benthic macro-invertebrates. Samples were collected at three sites, one before the effluent discharge point into the stream (site 3) and two sites which were located downstream after the discharge points (sites 1 and 2). High levels of chemical pollutants were recorded at sites 1 and 2 (ZINWA red category) whereas site 3 (reference site) consisted of relatively clean water (ZINWA blue category). This was confirmed by the biological evaluation process. The SASS4 scores at sites 1 and 2 indicated a deterioration of water quality while site 3 there was good water quality with high species diversity. Detrended correspondence analysis (DCA) showed that pollution sensitive taxa such as Hemiptera, Trichoptera, Coleoptera and Odonata were dominant at site 3 whilst the other sites were dominated by pollution tolerant species such Chironomids. Continuous discharge of effluent could lead to extreme degradation of Mazai stream hence loss of biodiversity of macro-invertebrates.

A method to identify estuarine macroinvertebrate pollution indicator species in the Virginian Biogeographic Province

Abstract Macroinvertebrates are commonly used as biomonitors to detect pollution impacts in estuaries. The goal of this research was to identify estuarine benthic invertebrates that could be used as indicator species to detect presence or absence of pollution in the Virginian Biogeographic Province using available monitoring data from the U.S. Environmental Protection Agency's Environmental Monitoring and Assessment Program. The data were first subdivided by habitat. Then we summarized the benthic community using principal coordinates analysis and projected the results onto a pollution gradient. Then we compared medians and corrected interquartile ranges to identify indicator species that were sensitive to pollution (or lack thereof) and showed low variation in response. Our data set was divided into smaller subsets that ranged from 108 to 532 stations per habitat. Out of 707 species in the Virginian Province, 67 were identified as pollution indicator species; 37 pollution sensitive taxa and 30 pollution tolerant taxa. The pollution sensitive taxa were represented by more phyla than were the pollution tolerant taxa. The pollution tolerant taxa were dominated by deposit feeders while the pollution sensitive taxa were not dominated by animals using any one feeding strategy. The pollution sensitive taxa included many crustaceans, known to be sensitive to pollution, while the pollution tolerant taxa included many tubificid oligochaetes, which are common indicators of pollution. Our empirically based results corresponded well with other studies that identified tolerance values or indicator species. One advantage of this technique is that it can be used on smaller data sets, assuming that there are not major habitat differences among the samples. We believe that this parsimonious technique can be applied to other coastal areas where mid-size (100–500 stations) monitoring data sets are available.

Critical influence of seasonal sampling on the ecological quality assessment of small headwater streams

Variability in the ecological quality assessment of reference sites was tested on small headwater streams in Ireland. Although headwater streams constitute a large portion of the river channel network, they are not routinely monitored for water quality. Various metrics were used including the Irish Q-value and the newly developed Small Streams Risk Score (SSRS), and metrics applied elsewhere in the Atlantic biogeographic region in Europe, including the Biological Monitoring Working Party score (BMWP), the Average Score per Taxon (ASPT), the Ephemeroptera, Plecoptera and Trichoptera taxa (EPT), the Belgium Biotic Index (BBI) and the Danish Stream Fauna Index (DSFI). The AQEM (version 2.5a) assessment software was used to apply some of these metrics. The spring and summer datasets are used to test the performance of biotic metrics with respect to season, and the applicability of their use to assess the ecological quality of wadeable streams. The quality status of most sites assigned by the various metrics was high using the spring invertebrate data, and an apparent considerable deviation in quality status occurred when the summer data was applied. Seasonal differences were noted using all the biotic indices and are attributed to the absence of pollution-sensitive groups in summer. Seasonal variability in the water quality status was particularly evident in acidic streams draining non-calcareous geologies with peaty soils that had relatively lower numbers of taxa. Some indices applied reflect a greater seasonal difference in the quality category assigned. The least amount of variability between seasons was obtained using the ASPT and the SSRS risk assessment system. Results suggest that reference status is reliably reflected in spring when more pollution-sensitive taxa were present, and that a new ecological quality assessment tool is required for application in summer when impacts may be most severe. This highly heterogeneous freshwater habitat seems to have too few taxa present in the summer to reliably determine the ecological quality of the stream using the available indices.

Keeping it simple: Benefits of targeting riffle-pool macroinvertebrate communities over multi-substratum sampling protocols in the preparation of a new European biotic index

Abstract The purpose of this study was to test the performance of a new sampling strategy for bioassessment of water quality. The macroinvertebrates living in the mineral substrata of geomorphological unit riffles strategy (MMS-GUR) concentrates sampling effort on certain geomorphologically and hydrobiologically representative units within survey sites and refines the level of taxonomic sorting of pertinent macroinvertebrate communities therein. Previous data have demonstrated that the mineral substrata of geomorphological unit riffles (GURs) harbour a wide variety of macroinvertebrates and pollution-sensitive taxa [Beauger, A., Lair, N., Reyes-Marchant, P., Peiry, J.-L., 2006. The distribution of macroinvertebrate assemblages in a reach of the River Allier (France), in relation to riverbed characteristics. Hydrobiologia 571, 63–76]. These units are typical of alluvial rivers and are easily identified from the bank and easily sampled. The objectives of the present study were to specify the sampling effort required to obtain representative taxonomic data from these communities, and to compare the performance of the new protocol with that of an established multi-substratum sampling methodology (XS). Two sampling series were carried out on two rivers within the same hydro-ecoregion. Two separate data were compiled from each site, incorporating taxon lists and relevant biological, ecological and physiological trait (BEPT) information, one using conventional (XS) methodology and the other from the MMS-GUR protocol. Macroinvertebrates sampled from three GURs of the River Allier ranged from pollution-tolerant to pollution-sensitive taxa. A comparison between the two methods (MMS-GUR and XS) conducted on the Allier and the Loire confirmed the validity of GURs as representative features, showing that pollution-sensitive taxa were better represented on mineral substrata and pollution-tolerant taxa were not over-estimated. The XS method is characterised by eight samples, while preliminary studies on the Allier suggested that a maximum of 13 samples were required to obtain sufficient taxonomic richness using the MMS-GUR methodology. However in river sections where pollution-sensitive taxa were numerous, the number of MMS-GUR samples required for analysis could be reduced to 10 or 8. In the context of the EU Water Framework Directive and associated AQEM project, the MMS-GUR protocol may facilitate the comparison of different rivers by sampling macroinvertebrate communities from similar rhithron or epipotamon habitats and focussing on pollution-sensitive taxa. It has the further advantage of reducing the time and effort spent in sampling and sorting. Increasing the resolution of taxonomic information to the genus level may also improve the standard of water quality assessment.

Anthropogenic Impacts on Aquatic Insects in Six Streams of South Western Ghats

Diversity patterns of aquatic insects among sampling sites lying with!ç the unprotected and protected areas of Western Ghats were studied. This study primarily emphasizes whether anthropogenic influence is the prime cause for the presence of aquatic insects especialIy of pollution-sensitive organisms belonging to the orders Ephemeroptera, Plecoptera and Trichoptera, or to factors such as the physico-chemical features of the water, or sampling methods. Six streams were sampled quantitatively, of which three streams (Abbifalls, Monkey falls and SiIver Cascade) were within protected areas and the remaining three streams (Kumbakarai, Shenbagadevi and Manimutharu falls) were in unprotected areas. A total of 3,209 individual aquatic insects belonging to 25 genera, 18 families and 7 orders were collected. The highest species richness and abundance was observed in Monkey falls followed by Kumbakkarai falls. Large çumbers of more habitat-sensitive organisms such as Ecdyonurus sp., Epeorus sp., Thalerosphyrus sp., Euthraulus sp., and Nathanella sp., were found in Monkey falls. Though the species assemblage was somewhat different, pollution-sensitive taxa were also observed in Kumbakkarai falls. Shenbagadevi and Manimutharu falls had a lower diversity of aquatic insects. The likely causes of these differences are discussed.