Quality Of Aquatic Ecosystems Research Articles

El estado ecológico de las pequeñas cuencas de cabecera en las serranías béticas húmedas (parque natural Los Alcornocales, sur de España) según la Directiva Marco del Agua: ¿su aplicación garantiza la conservación?

In compliance with the European Water Framework Directive, member states have had to develop a method to assess the quality of aquatic ecosystems by comparing the current situation regarding near–natural reference conditions for each river type. In 2008, the Spanish Ministry of Environment approved the Order of Water Planning Statement. This statement sets out reference conditions and ecological status class change limits for the different types of rivers in Spain for which sufficient data are available. In the presentstudy, we established reference conditions and quality class thresholds for streams classified as wet Betic mountain rivers from 24 reaches of streams located in the Los Alcornocales natural park, using two qualitative indices based on macroinvertebrates (IBMWP and IMMi–L). The results for the IBMWP index indicate that from the standpoint of management of the ecological state, the watercourses studied show more affinity with the types of the Spanish Atlantic siliceous slope than with those of the Mediterranean siliceous slope when we consider EQR values. Considering the threshold values, the index resembles siliceous low Mediterranean mountain rivers (type 8). However, the EQR values do not match those calculated in this study. These results suggest that it is necessary to use an index adapted to the characteristics of these watercourses. Application of the quality criteria contained in the Guadalete–Barbate and Mediterranean–Andalusian Basin Plans to the management of these waterways is discussed, because it is unlikely that they ensure the maintenance of good ecological status. We thus propose a new calibration of the IBMWP index that ensures the maintenance of good environmental status of watercourses in this natural area, and the use of the IMMi–L index as an effective management tool. However, as our study area represents only a part of the wet headwaters in the southern Iberian peninsula, analysis of other basin types is necessary to complete such information.

Community structure and nutrient level control the tolerance of autotrophic biofilm to silver contamination.

Autotrophic biofilms are complex and fundamental biological compartments of many aquatic ecosystems. Since microbial species differ in their sensitivity to stressors, biofilms have long been proposed for assessing the quality of aquatic ecosystems. Among the many stressors impacting aquatic ecosystems, eutrophication and metal pollution are certainly the most common. Despite that these stressors often occur together, their effects on biofilms have been far much studied separately than interactively. In this study, we evaluated the interactive effects of silver (Ag), a reemerging contaminant, and phosphorus (P), a nutrient often associated with freshwater eutrophication, on the structure and functioning of two types of autotrophic biofilms, one dominated by diatoms and another one dominated by cyanobacteria. We hypothesized that P would alleviate the toxic effects of Ag, either directly, through the contribution of P in metal detoxification processes, or indirectly, through P-mediated shifts in biofilm community compositions and associated divergences in metal tolerance. Results showed that Ag impacted biofilm community structure and functioning but only at unrealistic concentrations (50μg/L). P availability led to significant shifts in biofilm community composition, these changes being more pronounced in diatom- than those in cyanobacteria-dominated biofilm. In addition, P tended to reduce the impact of Ag but only for the cyanobacteria-dominated biofilm. More generally, our results highlight the preponderant role of the initial community structure and nutrient level on biofilm response to metallic pollutants.

Evaluation of effect of sediment on aquatic ecosystems using decision tree forest and group method of data handling

In this study, the performances of the decision tree forest and group method of data handling for evaluation scale of the severity (SEV) of ill effect for fishes were investigated. The independent variables were concentration of suspended sediment (SS), species, life stage, and duration of exposure. This study is based on 198 data of aquatic ecosystem quality over a wide range of sediment concentrations (1–500,000 mg SS/L) and durations of exposure (1–35,000 h). Results showed that exposure duration is the most important factor on SEV, and based on the results, this alternative approach is better than traditional regression models with a higher recognition rate, forecast accuracy, and strong practical value.

Biometric parameters of the bream (Abramis brama) as indicators for long-term changes in fish health and environmental quality--data from the German ESB.

Piscifaunal health depends upon the state and quality of the aquatic environment. Variations in physical condition of fish may therefore be attributed to changes in environmental quality. Based on time series of up to 20 years of biometric data of bream from multiple sampling sites of the German environmental specimen bank (ESB), this study assessed whether changes in biometric parameters are able to indicate long-term alterations in fish health and environmental quality. Evaluated biometric parameters of fish health comprised length and weight of individuals of a defined age class, the condition factor, lipid content and hepatosomatic index (HSI). Although there are negative trends of the HSI, the overall development of health parameters can be interpreted as positive. This seems to suggest that health parameters conclusively mirror the long-term improvement of water quality in the selected rivers. However, the applicability of the condition factor as well as lipid content as indicators for fish health remained subject to restrictions. Altogether, the results from the ESB confirmed the high value of biometric parameters for monitoring of long-term changes in state and quality of aquatic ecosystems.

Can excluding non-insect taxa from stream macroinvertebrate surveys enhance the sensitivity of taxonomic distinctness indices to human disturbance?

Taxonomic distinctness (TD) indices are increasingly recognized as promising measures of diversity for assessing the quality of aquatic ecosystems. TD indices have a number of desirable properties due to their insensitivity to variations caused by sampling settings (e.g. sampling size and sampling efforts) and natural habitat types. But which TD indices are effective at determining anthropogenic effects is currently under debate. Here, we address this issue by calculating average taxonomic distinctness (Δ+) and variation in taxonomic distinctness (Λ+), the two aspects of TD indices considered to be the most powerful ecological indicators, using datasets of entire macroinvertebrate assemblages, insect-only assemblages and EPT taxa obtained from central Chinese running-water habitats. We examined the performances of TD indices based on the three datasets as ecological indicators in detecting anthropogenic stress, and tested the relationships between three Δ+ and environmental variables including land use and water quality. We found that they were all weakly correlated with traditional diversity indices. In distinguishing reference and disturbed sites, Δ+ of insect taxa performed much better than Δ+ of the entire macroinvertebrate and EPT dataset. In general, three Δ+ were related to land-use and water-quality variables, but particular environmental variables accounting for Δ+ were quite different in three datasets. The Δ+ of insect taxa responded more readily to anthropogenic stress than did that of all macroinvertebrate and EPT taxa. We argue that the widespread distribution of some tolerant non-insect taxa (Oligochaeta and Mollusca) in impaired sites but absence in reference sites adds too much “noisy” information for the entire-taxa TD index to distinguish man-made variation from natural variation. Moreover, using only EPT taxa resulted in lowering the sensitivity of Δ+ because too few taxa at species or higher taxonomic levels were available. Thus, we propose that Δ+ of insect taxa may be a more effective biodiversity measure for estimating anthropogenic disturbance on stream macroinvertebrate assemblages.

Environmental Quality Assessment of Selected Sites in Bolgoda North Lake Using Three Environmental Quality Determining Indices

The Index of Biotic Integrity (IBI) based on fish has been identified as a reliable biomonitoring tool that can be used to assess the quality of aquatic ecosystems. This tool wasapplied to evaluate the habitat quality of three selected sites of the Bolgoda North Lake (6"40'-49' N: 70" 54'-58' E), a brackish water estuarine system located in the western province ofSri Lanka. In order to compare and contrast the accuracy of IBI based habitat qualityassessment, two other common indices, Water Quality Index (WQI) based on selectedenvironmental parameters and Shannon Weiner Diversity Index (SWDI) based onzooplankton and phytoplankton were determined for the three sites.Three selected sites, namely, Thuduwa, Borupana and Attidiya were sampled for fish,selected environmental parameters and zooplankton and phytoplankton over a period of 6months from February to July 2012. Using 12 metrics that reflected taxonomic composition,habitat composition, tropic composition and fish health, 3 separate fish based Indices ofBiotic Integrity were calculated for these three sites.The environmental quality of the three sites based on the calculated fish based Indices ofBiotic Integrity concluded that the condition at Thuduwa site was “good”; at Borupana“poor-very poor” and at Attidiya site “very poor”. The calculated WQI values for Thuduwasite qualify it as a site having “good” water quality, Borupana site having “medium” waterquality and Attidiya site having “bad” water quality. Results of both indices were generallysimilar for the three sites. The Shannon Wiener Diversity Index, on the other hand did notshow a significant difference between 3 sites, which could be clearly attributable to thehigh/low evenness values. However, differences shown in the occurrence of indicator speciesgenerally agreed with both IBI and WQI. For instance phytoplankton indicators of pollutionsuch as Microcystis sp, Pediastrum sp, Scenedesmus sp, Actinastrum sp were found in highnumbers at Attidiya, in moderate numbers at Borupana and only the latter two species in lownumbers at Thuduwa.When all three indices were compared, IBI can be considered as the best index to describethe overall habitat quality, as it reflects the consequences of a long term habitat degradationdue to change in environmental parameters at sites shown by changes in fish assemblageswhereas WQI reflects the precise level of specific pollutants and SWDI reflects thezooplankton and phytoplankton assemblage at any given time (as they are short lived).

Connectivity influences on nutrient and sediment migration in the Wartburg catchment, KwaZulu-Natal Province, South Africa

Non-point-source (NPS) pollution of surface and groundwater by sediment and nutrient loads emanating from agricultural catchments is a prominent environmental issue, with major consequences on water supply and aquatic ecosystem quality. The concept of connectivity has proved invaluable in understanding migration of NPS pollutants in catchments. Observations of sediments or suspended solids (SS), nitrate (NO3) and phosphorous (P) fluxes alongside stable water isotope sampling were made on a nested basis at field and catchment (41km2) scales for a series of events in the Wartburg catchment, South Africa. The nested catchment scale sampling was focused on control features in the stream network, including road crossings, farm dams and wetland zones. The analyzed stable water (δ18O and δ2H) isotopes results were used to interpret the connectivity of the contributing land forms and the stream network. The results reveal the dominant influences of farm dams and wetlands in limiting the downstream migration of sediment and nutrients for all but the most intense events. Certain events resulted in mixing in the dams and larger resultant outflow than inflow loads. These occurrences appear to be as a result of combinations of reservoir status, catchment antecedent conditions and rainfall depth and intensity. The nutrients loads between Bridge 1 and Bridge 2 stations reflect the bedrock control, where contributions from sugar cane hillslopes between these stations are not retained, even in the short wetland upstream of Bridge 2. Isotope analyses reveal that the headwaters, comprising 70% of the catchment area, contribute as little as 29% of the total catchment discharge, due to impoundments in this area. However, this contribution varies significantly for different events, reaching a maximum of 78% of the catchment discharge. It can therefore be concluded that nutrients and sediment migration in the Wartburg catchment is greatly influenced by connectivity. The δ18O and δ2H water isotopes can be used to assess the contributions of different sources of water which impact the transport of nutrients and sediments in catchments.

The integrated biomarker response revisited: optimization to avoid misuse.

The growing need to evaluate the quality of aquatic ecosystems led to the development of numerous monitoring tools. Among them, the development of biomarker-based procedures, that combine precocity and relevance, is recommended. However, multi-biomarker approaches are often hard to interpret, and produce results that are not easy to integrate in the environmental policies framework. Integrative index have been developed, and one of the most used is the integrated biomarker response (IBR). However, an analysis of available literature demonstrated that the IBR suffers from a frequent misuse and a bias in its calculation. Then, we propose here a new calculation method based on both a more simple formula and a permutation procedure. Together, these improvements should rightly avoid the misuse and bias that were recorded. Additionally, a case study illustrates how the new procedure enabled to perform a reliable classification of site along a pollution gradient based on biomarker responses used in the IBR calculations.

Understanding the impact of crop and food production on the water environment—using sugar as a model

The availability of fresh water and the quality of aquatic ecosystems are important global concerns, and agriculture plays a major role. Consumers and manufacturers are increasingly sensitive to sustainability issues related to processed food products and drinks. The present study examines the production of sugar from the growing cycle through to processing to the factory gate, and identifies the potential impacts on water scarcity and quality and the ways in which the impact of water use can be minimised. We have reviewed the production phases and processing steps, and how calculations of water use can be complicated, or in some cases how assessments can be relatively straightforward. Finally, we outline several ways that growers and sugar processors are improving the efficiency of water use and reducing environmental impact, and where further advances can be made. This provides a template for the assessment of other crops.

Effect of water quality and confounding factors on digestive enzyme activities in Gammarus fossarum

The feeding activity and subsequent assimilation of the products resulting from food digestion allow organisms to obtain energy for growth, maintenance and reproduction. Among these biological parameters, we studied digestive enzymes (amylase, cellulase and trypsin) in Gammarus fossarum to assess the impact of contaminants on their access to energy resources. However, to enable objective assessment of a toxic effect of decreased water quality on an organisms' digestive capacity, it is necessary to establish reference values based on its natural variability as a function of changing biotic and abiotic factors. To limit the confounding influence of biotic factors, a caging approach with calibrated male organisms from the same population was used. This study applied an in situ deployment at 23 sites of the Rhone basin rivers, complemented by a laboratory experiment assessing the influence of two abiotic factors (temperature and conductivity). The results showed a small effect of conductivity on cellulase activity and a significant effect of temperature on digestive enzyme activity but only at the lowest temperature (7 °C). The experimental conditions allowed us to define an environmental reference value for digestive enzyme activities to select sites where the quality of the water impacted the digestive capacity of the organisms. In addition to the feeding rate, this study showed the relevance of digestive enzymes as biomarkers to be used as an early warning tool to reflect organisms' health and the chemical quality of aquatic ecosystems.

Development of reference conditions for suspended solids in streams

Our aim was to develop protective physical and biological thresholds that identify the upper limit of the least disturbed (reference) condition for total suspended solids (TSS). The study focuses on streams in agricultural regions across Canada from which we collected contemporary TSS and benthic invertebrate data, and compiled long-term TSS data sets. Reference conditions for TSS were analyzed by five approaches previously applied in Canada, Australia and New Zealand, and the USA. In addition, ecological reference conditions for TSS were developed using regression-tree analysis to determine change-points along TSS gradients for three invertebrate metrics (percentage Ephemeroptera-Plecoptera-Trichoptera, total richness, and modified family biotic index). Increased agricultural land-cover was linked to higher TSS in most agricultural regions which, in turn, was associated with degraded environmental conditions and a reduction in the relative abundance of pollution-intolerant taxa. The five physical approaches produced a narrow range of regional TSS reference condition values (2.7 to 6.2 mg L–1). Ecological reference conditions for TSS ranged from 3.5 to 11.1 mg L–1 across Canada. We conclude that long-term TSS databases may serve to generate interim sediment criteria because ecological reference conditions were similar to those calculated from physical data alone. These interim sediment criteria may be appropriate targets for use in evaluation of restoration programs designed to improve environmental quality of aquatic ecosystems (e.g., beneficial or best management practice applications).

Hydro biological Characteristics of Some Semi-intensive fish culture ponds of Lumding town of Nagaon district, Assam

Hydrobiological assessment is useful for assessing the ecological quality of aquatic ecosystem since biological communities integrate the environmental effects of water chemistry. Ten fish ponds from Lumding town, which were under semi-intensive culture practice, were selected for hydrobiological investigations. Physico-chemical properties were studied for a period of two years from July 2009 to June 2011.Some selected parameters like pH, dissolve oxygen, free carbon dioxide, TDS , total alkalinity, total hardness, sp. Conductivity, transparency and BOD were studied on some fish pond water. P H ranges from 6.1 to8.5. Temperature ranges from 18 0 C-32 0 C. Color shows light green to dirty green. Transparency ranges 17-42cm, dissolve oxygen ranges from 3.2- 8.0 ppm, total alkalinity ranges from 7.9-20.0ppm, Hardness ranges from 60-135 ppm, sp.conductance ranges from123-247µmhos/cm and BOD ranges from3.1-5.0ppm. The phytoplankton belonging to division Chlorophycae and Cyanophycae are predominant over the others and zooplanktons belonging to group Protozoa, Rotifers are predominant. . A total of 30 species of belonging to Chlorophycae. Cyanophycae were identified and a total of 20 species of Rotifera, 2 species of Cladocera and 1 genus of Copepods were found. The present study is expected to help achieve better and higher yield of fish by the fish farmer with increasing awareness regarding the hydrobiological feature of the pond and implement scientific management practices accordingly.

Seasonal and PAH impact on DNA strand-break levels in gills of transplanted zebra mussels

Genotoxicity endpoints are useful tools to biomonitor the physicochemical and biological quality of aquatic ecosystems. A caging study on the freshwater bivalve Dreissena polymorpha was planned to run over four seasons in the Seine River basin in order to assess whether DNA damage measured in transplanted mussels to polluted area vary according to seasonal changes. Three sites were chosen along the Seine River, one upstream from Paris and two downstream, corresponding to a chemical gradient of water contamination. The DNA strand break (comet assay) and chromosomal damage (micronucleus test) were measured in caged mussels at each site and in winter, spring and summer, along with PAH water contamination, PAH bioaccumulation, the mussel condition index (CI), the gonado-somatic index (GSI) and the filtration rate (FR). The level of DNA strand break measured in winter was low and increased in spring, concomitantly with FR and GSI. Over the same period, micronucleus (MN) frequency and PAH bioaccumulation decreased significantly in caged mussels, with both parameters positively correlated to each other. DNA strand-break levels and MN frequencies showed inter-site variations corresponding to the chemical contamination gradient. These two genotoxicity endpoints usefully complement each other in field studies. These results show that the MN test and comet assay, when applied to gill cells of caged zebra mussels, are sensitive tools for freshwater genotoxicity monitoring.

English

The aim of present study was to determine the LC50 value of in Caspian sea kutum. The results indicated that median lethal concentration (LC50) of Caspian sea kutum (Rutilus frisii kutum) for 24, 48, 72 and 96 h of exposure are 2.944, 2.756, 2.562 and 2.310 ppm, respectively and median lethal concentration (LC50) of lead to Caspian sea kutum (R. frisii kutum) for 24, 48, 72 and 96 h of exposure as 315.841, 298.456, 281.419 and 268.065 ppm, respectively. LC50 increased with decrease in mean exposure times for both metals. Physiological responses like rapid opercular movement and frequent gulping of air was observed during the initial stages of exposure after which it became occasional. All these observations can be considered to monitor the quality of aquatic ecosystem and severity of pollution. Hence, concluded that copper is more toxic than lead for Caspian sea kutum (R. frisii kutum).   Key words: Copper sulfate, lead nitrate, Rutilus frisii kutum, Caspian sea kutum, physiological responses, median lethal concentration (LC50).

DPSIR conceptual framework role: a case study regarding the threats and conservation measures for caddisflies (Insecta: Trichoptera) in Romania

The implementation of some strategies such as DPSIR framework may lead to a better coordination at both local and national level with a view to maintaining biodiversity and quality of water bodies. The different sensibility of the benthic macroinvertebrates has been used in determining the manner in which these communities are being influenced by the socio-economic development, in the end modifying the biodiversity. The present study aims at presenting a list concerning the different species of caddisflies identified in the larva phase in Natura 2000 site Lower Gorge of Mures river, to draw attention on existing threats regarding the quality of aquatic ecosystems based on the indentified caddisflies species and also to propose a series of conservation measures considered essential to the sustainable development of socio-ecological complexes in the target area. The sample collecting points were represented by 13 stations used to identify the caddisflies species in the larva phase. There were identified 20 species included in a number of 7 families. The most frequent species were Hydropsyche instabilis and Hydropsyche fulvipes (qualitative samples), and Hydropsyche instabilis , Hydropsyche fulvipes and Ecclisopteryx madida (quantitative samples), respectively.

Modeling macrozooplankton and water quality relationships after wetland construction in the Wenyuhe River Basin, China

The biodiversity of macrozooplankton and physicochemical indices at eight sites in the Wenyuhe River Basin were analyzed from April 2010 to March 2011 to assess the water quality following construction of a wetland (CW). The association between biodiversity and physicochemical parameters was analyzed using a self-organizing map (SOM). The water quality in the upstream portion of the CW showed no overall improvement during this period based on biodiversity (H′) and physicochemical assessment (Pb/n). Both assessments indicated that the water quality in upstream of CW was partially improved and showed an evident time dependent relationship after CW. Although a sample site, which received water from two streams, showed higher biodiversity in an integrative manner, the physicochemical assessments were more heavily influenced by treated water from the Qinghe Sewage Treatment Plant, rather than upstream at the other river basin. This was a noteworthy demonstration that physicochemical and biological assessments were not in accord and addressed the separate functioning of river ecosystems under field conditions. Physicochemical assessment may represent water quality more conservatively with respect to drinking water maintenance than biodiversity assessment. Nitrogen pollution was the main cause for the decrease in physicochemical conditions. Overall, the results indicated that the association between biodiversity and physicochemical assessments determined from the SOM could reveal aquatic ecosystem quality in a comprehensive manner and therefore be a useful tool for defining water quality and ecological integrity in aquatic ecosystem management, especially for complex water environments.

Ecological assessment of groundwater trophic status by using artificial substrates to monitor biofilm growth and activity

The European water legislation highlights the necessity of developing ecological criteria for assessing the quality of aquatic ecosystem. While a multitude of ecological indicators has been proposed and validated for streams, rivers and lakes, these indicators are not available for groundwater ecosystems. In the present study, we developed a method based on the measurements of the growth and activity of microorganisms developed on artificial substrates (glass beads) incubated in wells to characterize the trophic status of groundwater. Incubation sites were selected in an urban aquifer where previous works showed contrasting trophic conditions in groundwater due to artificial groundwater recharge practices. Total proteins, total carbohydrates, dehydrogenase and hydrolytic activities were measured on glass beads incubated in wells for two periods of 2 months (October–December 2010 and April–June 2011). Biofilm measured on glass beads was significantly more developed and active in wells where groundwater was enriched with dissolved organic matter due to artificial groundwater recharge. Indeed, most microbial variables (total proteins and dehydrogenase activities for the two incubation periods and hydrolytic activities for the second incubation period) were significantly and positively correlated with the concentrations of dissolved organic carbon (DOC) in groundwater. The availability of phosphorus also tended to influence biofilm growth (assessed by total carbohydrates) when PO43− concentrations were lower than 50μg/l. Overall, our study clearly demonstrated that artificial substrates acting as colonisable area for microorganisms could be used to efficiently monitor nutrient enrichment in aquifers.

Thermodynamic oriented ecological indicators: Application of Eco-Exergy and Specific Eco-Exergy in capturing environmental changes between disturbed and non-disturbed tropical reservoirs

Effective assessment of ecological quality in aquatic ecosystems has become an important issue for researchers and environmental managers worldwide. The potential of thermodynamic oriented ecological indicators in environmental assessment and management was tested and compared with diversity measures in three tropical reservoirs located in the basin of the Paraopeba River, Minas Gerais State-Brazil. We computed Eco-Exergy based indices (Eco-Exergy and Specific Eco-Exergy) and the Margalef and Shannon–Wiener indices and tested differences in their responses to change in benthic communities across reservoirs characterised by different degrees of anthropogenic disturbance. Indices were estimated based on biotic descriptors (macrofauna biomass, composition, and abundance) and their values analysed against abiotic descriptors (pH, conductivity, transparency, turbidity, nutrients concentration, dissolved oxygen, chlorophyll a, and total dissolved solids). The Margalef index showed significant differences between reference and impacted sites, with the highest values in the former type of sites, (Pseudo F2.719=24,506, p=0.001), while the Shannon–Wiener index values showed no significant differences between reference and impacted sites. Eco-Exergy values were significantly higher at stations located in more disturbed sites (Pseudo F2.719=80.319, p=0.001), but Specific Eco-Exergy did not show really significant differences between disturbed and non-disturbed sites, although values were higher in the non-disturbed sites type. This might be explained by the fact that opportunistic tolerant species present high biomass values in polluted sites, since Eco-Exergy values may vary due to changes in biomass or information. On the other hand, differences in information between disturbed and non-disturbed sites were more subtle (although the number of species was higher in the less disturbed sites, it was not clearly reflected in Specific Eco-Exergy values). Our results suggest that thermodynamic oriented indicators can capture coherent structural changes in biological communities, highlighting its indicator potential for assessing the ecological condition/integrity of highly modified water bodies, such as reservoirs.

Geologic processes influence the effects of mining on aquatic ecosystems

Geologic processes strongly influence water and sediment quality in aquatic ecosystems but rarely are geologic principles incorporated into routine biomonitoring studies. We test if elevated concentrations of metals in water and sediment are restricted to streams downstream of mines or areas that may discharge mine wastes. We surveyed 198 catchments classified as "historically mined" or "unmined," and based on mineral-deposit criteria, to determine whether water and sediment quality were influenced by naturally occurring mineralized rock, by historical mining, or by a combination of both. By accounting for different geologic sources of metals to the environment, we were able to distinguish aquatic ecosystems limited by metals derived from natural processes from those due to mining. Elevated concentrations of metals in water and sediment were not restricted to mined catchments; depauperate aquatic communities were found in unmined catchments. The type and intensity of hydrothermal alteration and the mineral deposit type were important determinants of water and sediment quality as well as the aquatic community in both mined and unmined catchments. This study distinguished the effects of different rock types and geologic sources of metals on ecosystems by incorporating basic geologic processes into reference and baseline site selection, resulting in a refined assessment. Our results indicate that biomonitoring studies should account for natural sources of metals in some geologic environments as contributors to the effect of mines on aquatic ecosystems, recognizing that in mining-impacted drainages there may have been high pre-mining background metal concentrations.

A macroinvertebrate multimetric index to evaluate the biological condition of streams in the Central Amazon region of Brazil

Managers, researchers and technicians involved in the conservation and management of water resources in the Central Amazonia need a robust tool to assess biological quality in aquatic ecosystems. To provide such a tool, we developed a multimetric index based on stream macroinvertebrate data. We collected samples from eight reference (undisturbed) streams and 12 streams altered by deforestation and domestic sewage during two distinct seasons (dry and rainy) in the municipality of Manaus, Brazil. Metric candidates to compose the index were tested for: Range, temporal variability (stability), sensitivity in separating disturbed from reference streams, correlation with the anthropogenic disturbance gradient and natural stream variability and redundancy between metrics. Our final index included seven metrics: family, Trichoptera and Ephemeroptera–Plecoptera–Trichoptera (EPT) richness as richness measures, EPT percent abundance as a measure of composition, EPT/Chironomidae ratio and sensitive-taxa richness as tolerance measures and percent abundances of gathering-collectors and shredders as trophic measures. All metrics were scored relative to their range quartiles. The final index, derived from the sum of all metric scores (0–70), was divided into five sub-ranges to represent distinct levels of biological quality in streams (bad, poor, regular, good and excellent).