Runoff-related agricultural impact in relation to macroinvertebrate communities of the Lourens River, South Africa

A field study at the Lourens River, South Africa, was undertaken during the pesticide application period between November 2001 and January 2002 in order to investigate the potential relation of agricultural pollution to the aquatic macroinvertebrate fauna. The upper regions of the Lourens River were free of contamination (LR1), whereas subsequent stretches flowing through a 400-ha orchard area (LR2) received transient insecticide peaks. Continuously operating suspended-particle samplers as well as flood samplers operating during runoff events were used to measure pesticide contamination. In addition, various physicochemical and morphological parameters were examined. A survey of the macroinvertebrate communities associated with the rocky substrates was carried out every three weeks. Community indices were calculated using the South African Scoring System (SASS 5) for bioassessment of water quality in rivers. The two sites differed in pesticide pollution as well as in average turbidity levels (LR1 5.5 mg/L; LR2 64.3 mg/L), but were similar in bottom substrate composition and most other abiotic factors. At the downstream site (LR2), pesticide values of 0.05 microg/L azinphos-methyl in water as well as 49 microg/kg azinphos-methyl, 94 microg/kg chlorpyrifos and 122 microg/kg total endosulfan in suspended particles were found during runoff conditions. The macroinvertebrate communities of the two sampling sites were similar in terms of number of total individuals, but differed significantly (ANOVA) in average number of taxa (LR1 11.7, LR2 8.9). Seven out of 17 investigated taxa occurred in significantly reduced numbers or were even absent at the downstream site LR2. The community characteristics determined by SASS 5 showed a significantly less sensitive community structure at the downstream site (TS 41; ASPT 4.6), indicating continuously lower water quality compared to site LR1 (TS 80; ASPT 6.9). It is concluded that the Lourens River macroinvertebrate communities are affected by agricultural pollution, with pesticides and increased turbidity as the most important stressors.     

TheGammarus: Asellus ratio as an index of organic pollution

Macroinvertebrate populations includingGammarus pulex andAsellus aquaticus were surveyed at riffle sites on four lowland rivers, i.e. the Rivers Adur and Ouse and the Chess Stream, Sussex, and the Eridge Stream, Kent. Sites were situated both upstream and downstream of sewage treatment works. Macroinvertebrates were collected using a Surber sampler and at some sites the water analysed for the main chemical constituents.Poor water quality is characteristically associated with low biotic scores and in this respect theGammarus : Asellus ratio applied to riffle data corresponded with the Chandler Biotic Score Index and the Extended Trent Biotic Index. TheGammarus : Asellus ratio showed the closest correlations with concentrations of BOD, ammonia-nitrogen (NH₃-N), nitrite-nitrogen (NO₂-N) and phosphate-phosphorus (PO₄-P) being sensitive to changes in water quality brought about by organic enrichment in the four rivers investigated.It is proposed that theGammarus : Asellus ratio may provide a simple biological tool which could be used by anglers and other non-professional river users to routinely monitor water quality.     

Multivariate techniques relating macroinvertebrate and environmental data from a river catchment

Macroinvertebrates were collected over 4 years by standard sampling procedures used within the UK Environment Agency (EA). Contemporary environmental data were used to “explain” biological variation using multivariate techniques provided by the program CANOCO. Variations in macroinvertebrate taxa composition, Biological Monitoring Working Party (BMWP) score and average score per taxon (ASPT) primarily reflected changes in habitat across the Mole catchment. When the analysis was restricted to sites overlying the dominant geological stratum (Weald clay) the principal variation in taxa composition, BMWP score and ASPT was most correlated with variation in water quality. Significant correlations between the presence of certain taxa and measurements of dissolved oxygen (DO) provided support for the relative scores attributed to these taxa by the BMWP. The month in which a macroinvertebrate sample was collected was relatively unimportant as an influence on taxa composition.     

Multi-biochemical responses of benthic macroinvertebrate species as a complementary tool to diagnose the cause of community impairment in polluted rivers

Biological indexes, based on benthic macroinvertebrate taxa, are currently used worldwide to measure river ecological quality. These indexes assign a global ecological status of the biotic community, but not necessarily may detect specific effects of water pollutants. Conversely a large set of biochemical markers measured in macroinvertebrate benthic species can detect sublethal effects and inform us about additional environmental factors that are impairing benthic communities. This is especially interesting in moderately polluted sites, where other stressors are already affecting communities but not too strongly to be detected by biotic indexes. Up to ten different markers belonging to distinct metabolic paths and 42 contaminants measured in sample collections of the caddis fly Hydropsyche exocellata were assessed across a polluted gradient in the industrialized Mediterranean River basins of Besós and Llobregat (NE, Spain). Twenty four sample collections were selected to include macroinvertebrate communities representing the five impairment degrees defined by the Spanish Environmental authorities using the biotic metrics. Results evidenced a clear deterioration of the ecological water quality parameters and benthic communities towards downstream reaches. Biochemical responses varied significantly across the studied samples and were able to differentiate samples within communities having a good and deteriorated ecological stage. Principal Component Analyses indicated that salinity was one of the major stresses affecting macroinvertebrate assemblages, whereas antioxidant and metabolizing enzymes responded differently and were closely related to high and presumably toxic levels of accumulated organic pollutants. Therefore these results indicate that the use of multiple -markers sensitive to water pollution may provide complementary information to diagnose environmental factors that are impairing macroinvertebrate communities.     

Microdistribution patterns of macroinvertebrate communities upstream and downstream of organic effluents

The present study analyses the distribution patterns of macroinvertebrate communities in four microhabitats (riffles, glides, leaf litter and bank roots) upstream and downstream of two waste water treatment plant (WWTP) effluents in northern Spain rivers. Macroinvertebrate communities were analysed in November 2006 by taking 5 samples from each of the microhabitats under unaffected (upstream WWTP) and affected (downstream WWTP) conditions, respectively. Water velocity, depth, substrate coarseness and hydraulic stress by means of the Froude number were also estimated at all sampling locations.Under unaffected conditions, the abundance and presence/absence of certain macroinvertebrate taxa were mainly determined by hydraulic characteristics (water velocity and Froude number) and feeding resource availability. However, neither macroinvertebrate richness nor abundance were neither significantly correlated with hydraulic stress nor substrate coarseness, although the number of macroinvertebrate taxa increased in microhabitats with high structural complexity. Macroinvertebrate abundance increased downstream of both WWTPs, while macroinvertebrate richness was not adversely affected by the organic enrichment of water. The structure and composition of macroinvertebrate communities occurring in riffles was similar under unaffected and affected conditions, while communities from leaf litter and submerged bank roots showed important changes above and below the WWTPs, indicating that they are probably the most appropriate communities for water quality assessment.     

Preliminary observations on the benthic macroinvertebrate communities of Ross Bay,a polluted area of lough leane,south-west Ireland

The physical, chemical and biological water quality characteristics of Ross Bay, monitored during the period July 1974–May 1975, are described. The benthic macroinvertebrate standing crop of the littoral zone was sampled quantitatively during July 1974. The results are described in terms of biomass distribution and the distribution of taxa. The sampling stations are placed in an ordinal series based on their respective pollutional status. Changes in community structure and taxonomic composition along the series are described in terms of species diversity and the distribution of “indicator” organisms. Based on this distribution, a scheme of biotic indices is devised in order to reduce complex community composition to simple numerical terms. For this purpose, individual organisms are given a water quality rating which is dependent on their relative tolerance or intolerance to pollution. Significant correlation is shown between the ordinal series, water quality, Diversity Index ($\text{d}\text{?}$) values, Community Similarity (τ) values and Biotic Quality (qb) values. The biological evaluation of water quality in lakes is discussed and it is suggested that the littoral benthos may serve in any future assessment of organic pollution and enrichment in Lough Leane.     

Responses of aquatic organisms to metal pollution in a lowland river in Flanders: a comparison of diatoms and macroinvertebrates

The role of macroinvertebrates and diatoms as indicator for metal pollution was investigated by assessing both biota along a metal gradient in the Belgian river the Dommel. Macroinvertebrates and diatoms were sampled in summer and winter and physical-chemical characteristics of the water were measured at four different sample periods and related to sediment characteristics. Although metal concentrations, except cadmium, in the water nowhere exceeded water quality standards, high metal concentrations were measured in the sediment, indicating historical contamination of the Dommel. At the sites that were situated downstream of the pollution source, high levels of conductivity and chloride were measured in the water. Redundancy Analysis (RDA) indicated pH, phosphate and zinc as the significant environmental variables explaining each respectively 7.7%, 11.6% and 22.6% of the macroinvertebrate community composition. Two clusters could be separated, with Gammarus pulex, Leptocerus interruptus, Baetis rhodani and Cloeon dipterum associated with low zinc concentrations and Tubificidae, Asellus aquaticus, Erpobdella sp. and Chironomus thummi-plumosus associated with higher zinc concentrations. Ammonium (10.6%), conductivity (16.5%), chloride (11.4%) and zinc (5.9%) turned out to be significant variables explaining the diatom community structure. Based on physical-chemical differences and species composition, three different groups could be separated. With this Tabellaria flocculosa and Fragilaria capucina var. rumpens were associated with low metal concentrations, Gomphonema parvulum and Nitzschia palea with elevated concentrations and Eolimna minima and Sellaphora seminulum with high zinc concentrations. In conclusion, the diatom community best reflected the metal gradient. With regard to water quality indices, those based on macroinvertebrates best followed the metal pollution gradient and were most strongly correlated with physical-chemical variables of water and sediment. This study indicated that to assess the effect of metal pollution in lowland rivers, the combined use of macroinvertebrates and diatoms is more appropriate than the use of both biota separately.     

Integrated environmental assessment of Volturno River in South Italy

The application of a battery of toxicity and genotoxicity tests on pore water in parallel and in combination with physico-chemical analyses and benthic macroinvertebrate community investigations is discussed as a tool to assess the environmental quality of the Volturno River in South Italy. Toxicity testing was performed on the rotifer Brachionus calyciflorus and the crustacean Daphnia magna. Genotoxicity was determined by the SOS chromotest and Mutatox system. The biotic index used for macroinvertebrates was the extended biotic index that was developed to verify if the observed benthic community accords with the expected one for an identical environment without anthropic contaminations. The physico-chemical characterization of the surface waters showed a declining trend from up-river to down-river for dissolved oxygen and conductivity. Also, chemical variables showed a worsening along the river axis showing an increase in ammonium, phosphates, sulfates, and heavy metals. The assessment of macro-invertebrates reflected the general ecological deterioration occurring to chemical as well as toxic and genotoxic pollution. Furthermore, benthic community composition and the sediment contamination of toxic and genotoxic substances were shown to be correlated. We concluded that investigations on pore water, integrated with benthic macroinvertebrate communities, could provide the basis for a robust monitoring of rivers.     

Diversity, biotic and similarity indices: A review with special relevance to aquatic ecosystems

Diversity Indices, Biotic Indices and Similarity Indices are reviewed considering their ecological application, both theoretical and practical. Eighteen diversity indices in eight groups, nineteen biotic indices in ten groups and five similarity indices are examined for their applicability to biological systems, particularly aquatic ecosystems. All the diversity indices were found unsuitable except for Simpsons D, Hurlberts PIE, indices based on the theory of Runs (SCI and TU) and possibly McIntosh's M. Indices based on information theory, such as H′ and H, although the most commonly used diversity indices were unsatisfactory due to the lack of exploration of their biological relevance. The use of H′ in aquatic ecosystems is only justified until the more satisfactory indices are adequately field tested.Biotic indices are highly specialised for a particular type of water pollution, usually organic pollution. Chutter's and Chandler's biotic index appear to be most favoured. In their present form, however, such indices are necessarily limited to the geographical area in which the tolerance lists were compiled. Although many comparisons have been made between diversity indices and biotic indices, these were found to be spurious as one index reflects community structure the other the physiological response of indicator species to one type of pollution. Such comparisons have usually been justified by claiming that one index performs better when compared to the term “water quality”, which is usually left undefined.The five similarity indices examined have been used in aquatic systems. It is not clear which of these indices is best to use. The percentage similarity index (PSC) and Pinkham and Pearson's index (B) appear to be most favoured for aquatic systems, though there is a need for further research and field testing of similarity indices for water pollution.The relationship and definitions of diversity and stability are examined. Though discussion is by no means concluded on this topic it is clear that diversity does not automatically lead to either stability or instability but may be found with both. Disturbance to an ecosystem may often increase diversity provided it is of intermediate frequency, yet an ecosystem may also become more diverse without becoming less stable.The numbers of these three types of indices have become legion, as has their use. It is time that only those indices with biological relevance were used. It is hoped that work will now concentrate on the promising members of the two indices of community structure (diversity and similarity) as these are of broad applicability while biotic indices are limited to one or a few pollutants and one geographical area.     

A modification of the Trent Index for use in Denmark

A new pollution index based on macroinvertebrates has been devised which can be used as a surveillance system in Danish streams. The index is inspired by the Trent Index although it was necessary to incorporate two new principles. First, the pollution indicators Asellus aquaticus and Chironomus sp. are used as negative taxa, with a negative influence on the index value, thereby strongly enhancing the utility of the keygroups. Secondly, the taxonomic groups used in the Trent Index have been replaced by establishing positive and negative index groups, where the number of negative index groups is subtracted from the number of positive. Thus, the utility of the basic principle, increasing pollution effecting decreasing numbers of taxonomic groups, is enhanced.     

In situ tests for water quality assessment: a case study in Pampean rivers

Two invertebrate species (Hyalella curvispina and Palaemonetes argentinus) and one macrophyte (Egeria densa) from a naturally high nutrient content system (Pampean rivers of La Plata, Argentina) were evaluated for their potential use in situ assays aiming to assess changes in water quality. Invertebrates were individually placed in cylindrical chambers in polluted sections of rivers and in reference upstream sites. Mortality after 48 h was high in polluted and reduced in control sites. Mortality was also higher in situ assays than in laboratory static tests. Standard sections of the macrophyte were also deployed at the reference and control sites. Growth (7 days) in terms of mass increment (but not in length) was consistently reduced in polluted sites. Results of benthic invertebrate and periphitic algae surveys were consistent with the in situ tests: pollution resulted in a decrease in the number of taxa, taxa replacement and in changes in the value of the biotic indices Indice Biótico PAMPeano and Indice de Diatomeas Pampeano, indicating deterioration of water quality. In situ assays have a high potential as environmental tools in integrated approaches of bioassessment programs.     

Diversity and community comparison indices: Assessing macroinvertebrate recovery following a gasoline spill

Diversity and community comparison indices were evaluated to determine their utility in quantifying macroinvertebrate response to a catastrophic gasoline spill into Wolf Lodge Creek, Idaho, U.S.A. The Shannon and Brillouin diversity indices, and the following community comparison indices were analyzed: (1) Jaccard's coefficient of similarity; (2) Renkonen's percentage similarity; (3) Bray-Curtis index; (4) Morisita's similarity index; (5) simplified Morisita index; (6) Canberra metric index; and (7) average χ² index. The Bray-Curtis and average χ² community comparison indices were more effective in quantifying differences in macroinvertebrate composition between gas-impacted and reference areas of Wolf Lodge Creek following the spill. In addition, these indices tracked the progressive spatial recolonization of macroinvertebrates during the 16 month recovery period. All other indices tested failed to adequately quantify macroinvertebrate community response to the gasoline spill.     

Monitoring the Effect of Sewage Effluent on the Oxford Canal Using Chironomid Pupal Exuviae

Collections of chironomid pupal exuviae from the Oxford Canal were taken monthly from May to October 1991 at stations above and below the sewage effluent discharge at Kidlington, near Oxford.
The chironomid exuvial assemblages showed clear changes reflecting the effects of the sewage, notably in the increased dominance of Parachironomus arcuatus and Chironomus riparius and other pollution-tolerant species downstream from the effluent inflow. A return to the pattern of taxa seen in the upstream stations was noted below the next canal lock, 2.8 km downstream from the effluent discharge.
Environmental quality indices, calculated according to the Chironomid Pupal Exuvial Technique, also reflected the effects of the sewage inflow.
The results show that chironomid populations, as sampled by collecting pupal exuviae, are potentially valuable for monitoring organic pollution in canals.     

Biological and functional responses of in situ bioassays with Chironomus riparius larvae to assess river water quality and contamination

Single species responses have the potential to measure impacts at earlier stages than more traditional methods based in community structure. This study evaluates a bioassay with biological (survival, development, growth) and functional (post-exposure feeding rate) responses of Chironomus riparius larvae to assess water quality and contamination in rivers. The bioassay with C. riparius third instar larvae was performed, in autumn and spring, in reference sites and in organic and metal contaminated sites in Portuguese rivers. Biotic, physical and chemical parameters were determined for each site. The relationship between both bioassays responses and biotic indices (IBMWP and IASPT) and the physical and chemical parameters of respective sites were determined. In general biotic indices were able to discriminate between contaminated and not contaminated sites although they demonstrated a poor ability to detect low level of metal contamination during autumn. IASPT was negatively related to ammonia concentrations in both seasons. No significant differences in survival and post-exposure feeding rate were found between sites. Development was inhibited in the most metal contaminated site during autumn, but pH and ammonia concentrations in water accounted for 82% of developmental variation during this season. Growth was highly inhibited in the most metal contaminated site during both seasons. In autumn, growth was also inhibited in the low metal contaminated site and, during this season, pH and Mn and Fe concentrations in water samples accounted for 97% of growth variation between sites. The results suggest that in situ bioassay with C. riparius larvae using growth as the endpoint is a responsive and suitable tool that can be used as bioindicator of metal pollution and to biomonitor water quality in metal contaminated rivers.     

A coefficient of community loss to assess detrimental change in aquatic communities

Many techniques used to evaluate biological community data for effects of wastewater discharge do not discriminate between change and harmful change. A coefficient using the ratio of numbers of taxa lost between an unaffectd reference community and a pollution affected community, to the total number of taxa found in the affected community, provides a better evaluation of detrimental change. The value of the coefficient is determined by both the observed change in community richness as well as change in taxonomic similarity. The coefficient produces values from zero indicating no harmful change to infinity where there is complete loss of a community. Macroinvertebrate data suggests that values exceeding 0.8 are indicative of excessively harmful change in those communities.     

Patterning and predicting aquatic macroinvertebrate diversities using artificial neural network

A counterpropagation neural network (CPN) was applied to predict species richness (SR) and Shannon diversity index (SH) of benthic macroinvertebrate communities using 34 environmental variables. The data were collected at 664 sites at 23 different water types such as springs, streams, rivers, canals, ditches, lakes, and pools in The Netherlands. By training the CPN, the sampling sites were classified into five groups and the classification was mainly related to pollution status and habitat type of the sampling sites. By visualizing environmental variables and diversity indices on the map of the trained model, the relationships between variables were evaluated. The trained CPN serves as a 'look-up table' for finding the corresponding values between environmental variables and community indices. The output of the model fitted SH and SR well showing a high accuracy of the prediction (r>0.90 and 0.67 for learning and testing process, respectively) for both SH and SR. Finally, the results of this study, which uses the capability of the CPN for patterning and predicting ecological data, suggest that the CPN can be effectively used as a tool for assessing ecological status and predicting water quality of target ecosystems.     

Scale-dependency of macroinvertebrate communities: responses to contaminated sediments within run-of-river dams

Due to their nutrient recycling function and their importance in food-webs, macroinvertebrates are essential for the functioning of aquatic ecosystems. These organisms also constitute an important component of biodiversity.Sediment evaluation and monitoring is an essential aspect of ecosystem monitoring since sediments represent an important component of aquatic habitats and are also a potential source of contamination. In this study, we focused on macroinvertebrate communities within run-of-river dams, that are prime areas for sediment and pollutant accumulation. Little is known about littoral macroinvertebrate communities within run-of-river dam or their response to sediment levels and pollution. We therefore aimed to evaluate the following aspects: the functional and structural composition of macroinvertebrate communities in run-of-river dams; the impact of pollutant accumulation on such communities, and the most efficient scales and tools needed for the biomonitoring of contaminated sediments in such environments. Two run-of-river dams located in the French alpine area were selected and three spatial scales were examined: transversal (banks and channel), transversal × longitudinal (banks/channel × tail/middle/dam) and patch scale (erosion, sedimentation and vegetation habitats). At the patch scale, we noted that the heterogeneity of littoral habitats provided many available niches that allow for the development of diversified macroinvertebrate communities. This implies highly variable responses to contamination. Once combined on a global ‘banks’ spatial scale, littoral habitats can highlight the effects of toxic disturbances.     

Time-dependent variation of mercury in a stream sediment and the effect upon mercury content in Gammarus pulex (L.)

A 3-month investigation has been carried out in a stream environment, on the fluctuation of the level of mercury within the sediment and the Gammarus pulex population. A positive correlation is found between the organic content and the mercury content (μg g⁻¹ dry wt) of the samples. The mean mercury concentration in the organic fraction can be read from the regression line. Of the units: μg g⁻¹ dry wt, μg g⁻¹ ashfree dry wt and μg cm⁻³, the values expressed g⁻¹ ashfree dry wt are considered to be of greatest validity for comparing different localities, and for establishing the pollution level in a stream sediment. Within the investigation period a very high fluctuation is found in the mercury content of analyzed Gammarus pulex. The phenomenon may be explained through fluctuations in the methylating processes within the sediment. No positive correlation is found between mercury in Gammarus pulex and in sediement taken from identical sample locations.     

Dinoflagellate cyst records and human disturbance in two neighboring estuaries,New Bedford Harbor and Apponagansett Bay,Massachusetts (USA)

The dinoflagellate cyst records in sediments from New Bedford Harbor and Apponagansett Bay demonstrate sensitivity to environmental change caused by human activity in the watersheds over the last 500 years. Changes in the species richness, as well as absolute and relative abundance of dinoflagellate cyst taxa reflect recent periods of development around the estuaries. Cyst taxa sensitive to these changes include Dubridinium spp., Polykrikos schwartzii, Lingulodinium machaerophorum, Operculodinium israelianum and Selenopemphix quanta. The greatest changes in the dinoflagellate cyst record occur during the 20th century, when New Bedford Harbor was exposed to both toxic pollution and heavy nutrient loading from point and non-point sources. Apponagansett Bay was not subject to industrial pollution and nutrient enrichment has been lower (from non-point sources). In Apponagansett Bay there is an increase in the dinoflagellate cyst species richness while species richness first increased, then declined in New Bedford Harbor. During the same period, the total dinoflagellate cyst concentration in New Bedford Harbor fluctuated over a wide range. The decline of species richness and the large fluctuations in the total cyst abundances signal the intensified anthropogenic disturbance in the watershed, notably a high degree of eutrophication and toxic pollution.     

Monitoring metal and metalloid bioaccumulation in Hydropsyche (Trichoptera, Hydropsychidae) to evaluate metal pollution in a mining river. Whole body versus tissue content

Whole body metal concentration is easier to analyse than concentration in tissues, but is often not an accurate measure of the potential toxicity of the metal. We tested if whole body metal and metalloid concentrations in the caddisfly Hydropsyche (Trichoptera, Hydropsychidae), common in a mine-polluted river (Guadiamar River, SW Spain), were a useful measure to extrapolate environmental degradation. Our results confirmed that metal and metalloid accumulation by Hydropsyche strongly correlated with metal and metalloid concentration both in the water and the sediment, and also correlated with macroinvertebrate community parameters such as total richness and abundance, as well as the richness of some taxonomic groups (EPT and OCH). Seven elements were analysed, Zn, Cu, Pb, As, Cd, Tl and Sb; only As did not show significant correlations. In addition, after leaving live organisms in clean water for 24 or 48 h, we found that 24 h were sufficient to clean the gut content and that between 33% and 75% of the whole body metal content were concentrated in this organ. Although concentration in tissues also discriminated between control and affected stations, we found better results with whole body concentrations when evaluating environmental quality.