Macroinvertebrate Community Index Research Articles

TICI: a taxon-independent community index for eDNA-based ecological health assessment.

Global biodiversity is declining at an ever-increasing rate. Yet effective policies to mitigate or reverse these declines require ecosystem condition data that are rarely available. Morphology-based bioassessment methods are difficult to scale, limited in scope, suffer prohibitive costs, require skilled taxonomists, and can be applied inconsistently between practitioners. Environmental DNA (eDNA) metabarcoding offers a powerful, reproducible and scalable solution that can survey across the tree-of-life with relatively low cost and minimal expertise for sample collection. However, there remains a need to condense the complex, multidimensional community information into simple, interpretable metrics of ecological health for environmental management purposes. We developed a riverine taxon-independent community index (TICI) that objectively assigns indicator values to amplicon sequence variants (ASVs), and significantly improves the statistical power and utility of eDNA-based bioassessments. The TICI model training step uses the Chessman iterative learning algorithm to assign health indicator scores to a large number of ASVs that are commonly encountered across a wide geographic range. New sites can then be evaluated for ecological health by averaging the indicator value of the ASVs present at the site. We trained a TICI model on an eDNA dataset from 53 well-studied riverine monitoring sites across New Zealand, each sampled with a high level of biological replication (n=16). Eight short-amplicon metabarcoding assays were used to generate data from a broad taxonomic range, including bacteria, microeukaryotes, fungi, plants, and animals. Site-specific TICI scores were strongly correlated with historical stream condition scores from macroinvertebrate assessments (macroinvertebrate community index or MCI; R2=0.82), and TICI variation between sample replicates was minimal (CV = 0.013). Taken together, this demonstrates the potential for taxon-independent eDNA analysis to provide a reliable, robust and low-cost assessment of ecological health that is accessible to environmental managers, decision makers, and the wider community.

Groundwater Diversity across New Zealand: From micro to macro-scale

Groundwater is home to a diverse range of organisms, both small and large, which form a complex ecosystem that helps to purify the water and keep it flowing smoothly. However, much of the processes that occur in this ecosystem are still a mystery and there are many important services that we have yet to fully understand. Our goal is to create a groundwater health index that can be used to monitor the health of groundwater, similar to the macroinvertebrate community index used for surface water systems. We are investigating both the macroinvertebrates and microbial diversity in our research. To gather data, we are collecting groundwater environmental (e)DNA samples and biofilm samples using in-situ biofilm bags from various sites in New Zealand across multiple seasons. We then analyze the water chemistry and sequence data for bacteria, archaea, eukaryotes, and fungi to determine the status of the groundwater source. Our findings show that there is a complex diversity present in both the groundwater itself (e.g., Fig. 1) and the attached microbial biofilm. We have also discovered variations between the attached and groundwater across all sites studied, with significant differences in the Shannon richness indicator in Canterbury. Additionally, we have observed differences in microbial populations depending on the lithology and water chemistry present. Our research aims to identify key species, both micro and macro, that can potentially act as a tool for predicting the health of groundwater. Furthermore, understanding the biological processes occurring in our groundwater may lead to the discovery of beneficial organisms capable of remediation.

Evaluating restoration success in a Great Lakes embayment: A case study for addressing beneficial use impairments

Aquatic habitats within the St. Louis River estuary were impacted when developing the Duluth-Superior Harbor (MN/WI USA) and through decades of unregulated industrial and municipal discharge. An effort to remediate and restore sediment quality in the harbor began by implementing projects designed to address Beneficial Use Impairments (BUI) identified in this Area of Concern. Habitat restoration in the 21st Avenue West project site was implemented to improve overall aquatic community health and address a degradation of benthos BUI. Restoration objectives focused on creating more complex bathymetric surfaces and mitigating contaminant exposure by capping with clean dredged material. Before and after construction, samples were collected to assess the benthic community within 21st Avenue West compared to results from least-impaired, reference locations. A scaled trimetric index (s-TMI), scored between 0 and 1, was used to track an impaired benthic community before and after construction.A median s-TMI value for 21st Avenue West prior to construction (value = 0.51) improved following restoration (site median = 0.65), reaching a site-wide value that was not significantly different from the least impaired removal target (reference median = 0.68, when calculated from pooled reference data). Results from post construction sample collections at 21st Avenue West suggest macroinvertebrate community index scores increased by more than 10% two years following construction. These results indicate that the 21st Avenue West habitat restoration effort successfully reached a degradation of benthos BUI goal and demonstrates that dredge material is a cost-effective alternative for construction.

Assessment of urban river pollution using the water quality index and macro-invertebrate community index

Assessment of urban river pollution using the water quality index and macro-invertebrate community index

Responses of Macroinvertebrate Communities to Hydromorphological Restoration of Headwater Streams in Brittany

Indices of fauna communities, including macroinvertebrates, have been widely used as indicators of environmental changes in streams with great success. However, in the evaluations of in-stream restorations, results from the deployment of macroinvertebrate community indices as bio-indicators have been inconclusive, with scanty evidence for success. This study aims to determine if in headwater streams, and particularly according to the type of in-stream restoration studied (i.e., suppression of concrete pipe), bio-indicators based on macroinvertebrate can be relevant. We monitored three headwater stream reaches where artificial structures constituting hydromorphological impairments to the streams were removed. We collected macroinvertebrate samples from impacted stream sections and control sites established along the streams. Samples were collected before and after the restoration activities, in a before-after-control-impact (BACI) study design. We used two macroinvertebrate-based multimetric tools (I2M2 and ERA) to evaluate the ecological status of the streams, based on macroinvertebrate community indices, and to identify the relative contributions of watershed anthropic pressures to the ecological status. We found that the removal of the artificial structures and the restoration of natural flow were successful in reducing clogging. However, only taxonomic richness showed a positive significant change. The results indicate that the presence of confounding factors, not addressed by the restoration works, may have been responsible for this minimal success in biodiversity recovery. Although the multimetric assessment tools were able to differentiate between streams and disentangle the effects of multiple pressures contributing to degradation in the streams, they were limited to a level below the watershed scale. Our results showed that for a better outcome for macroinvertebrate biodiversity improvement, methods of in-stream restorations must consider the multiple pressures contributing to the degradation of fauna communities in watersheds.

Macroinvertebrate and diatom community responses to thermal alterations below water supply reservoirs

AbstractRiver impoundments have transformed river ecosystems globally due to the modification of various abiotic and biotic factors. This study provides rare evidence quantifying how water supply reservoirs alter water temperature regimes and its effects on macroinvertebrate and diatom communities over a 4‐year period. We obtained near‐continuous water temperature measurements upstream and downstream of three reservoirs and analysed thermal variables in association with macroinvertebrate and diatom community indices (including taxonomic richness, proportion of Ephemeroptera, Plecoptera and Trichoptera taxa [%EPT] and diatom ecological guilds). Reservoirs typically decreased downstream thermal variability, with reduced summer temperatures and increased winter temperatures, and a delayed timing of annual temperature extremes. Marked differences in thermal regime modifications between reservoirs were observed, including evidence of inter‐annual variation associated with inter‐basin water transfers downstream of one reservoir. Biomonitoring indices showed associations with thermal indices that differed between site types (regulated versus non‐regulated) and seasons (spring vs. autumn). Various macroinvertebrate and diatom indices capturing community diversity elements and sensitivities to different environmental pressures were associated with higher maximum summer temperatures and lower minimum winter temperatures, suggesting ecological effects of reduced thermal variation downstream of reservoirs. Different ecological responses to thermal indices were observed between seasons, likely due to organism life‐cycle effects and intra‐annual thermal variations. Contrasting macroinvertebrate and diatom communities were observed between regulated and non‐regulated sites, which may be driven by differences in the thermal regime and other abiotic factors at regulated sites, including nutrient, sediment and flow regimes. Long‐term continuous water temperature monitoring of both multiple regulated and non‐regulated river systems is necessary to better understand the environmental and ecological effects of river impoundments. Given the extent to which river impoundment has modified stream temperatures globally, the inclusion of thermal regime data in environmental flow studies alongside hydrological information may guide the implementation of mitigation measures on impounded waterbodies.

A comparison of genetically and morphometrically identified macroinvertebrate community index scores with implications for aquatic life use attainment.

Measures of aquatic macroinvertebrate communities are often used to characterize water quality and indicate whether waterbodies are meeting management expectations. The accuracy of these measures depends on the skill and experience of the person identifying the macroinvertebrates, and obtaining these measures can be relatively expensive due to the time necessary for identification. Utilizing genetic identification of macroinvertebrate taxa has the potential to reduce the time of sample processing, identify a greater number of taxa, and increase the resolution of identification. We compared Colorado multi-metric index (MMI) scores from seven locations in the Big Thompson River, CO, based on genetic and morphometric identification and estimated the ability of MMI scores based on genetic identification to characterize aquatic life use attainment management thresholds. We found a significant linear relationship (p = 0.002, R2 = 0.87) between MMI scores generated by genetic and morphological identification. MMIs support the following aquatic life use designations as defined by the Colorado Water Quality Control Commission: Impaired < 40, Attaining > 48, and Ambiguous 40-48. These values correspond to MMIs based on genetic identification as Impaired < 20, Attaining > 64, and Ambiguous = 21-63 based on the prediction interval of the regression equation. Our results suggest that using genetically identified macroinvertebrates to estimate MMI scores can provide some degree of certainty regarding aquatic life use designations, and while it may be inappropriate at the current time to entirely replace morphologically based biotic integrity measures with those based on molecular identification, there are opportunities in their use.

Assessing the Quality of Amazon Aquatic Ecosystems with Multiple Lines of Evidence: The Case of the Northeast Andean Foothills of Ecuador.

We assessed the quality of Andes-Amazonia streams in Ecuador impacted by gold mining (GM), discharges from inefficient sewage network in urban areas (UA), wastes from fish farming (FF) and from non-functional landfill (LF) and other few threats (FT). We selectedthree lines of evidence (LOE)that were used separately and integrated into a index: water quality (WQI) and macroinvertebrate community (AAMBI) indices and phytotoxicity tests. Streams affected by UA and LF had the lowest scores to WQI and phytotoxicity, and by GM had the lowest scores to AAMBI. Macroinvertebrate absence in GM should be considered as a warning signal of long-term mining impacts in the area. The integrated LOE index showed that sites with identified threats had 30%-53% stream quality decline compared to FT sites. The use of the selected LOE seems to be auseful tools for long-term monitoring and evaluation of this sensitive aquatic ecosystem.

Current state of water quality indicators in urban streams in New Zealand

ABSTRACT National assessments have highlighted that urban streams have some of the poorest water quality in New Zealand, yet there has been no analysis focussing on these streams. In this study we defined urban streams as >15% catchment urban land cover and used monitoring data to assess several indicators of water quality including dissolved metals, nutrients, bacteria and the macroinvertebrate community index. We investigated associations between the indicators and urban land cover, imperviousness and geographic location. Water quality was highly variable, within and between monitored sites; and invariably poor when compared to water quality criteria. Dissolved zinc was positively related to the proportion of urban land cover and imperviousness in the upstream catchment. There were significant differences in ammoniacal-N, nitrate-N, turbidity, MCI, dissolved zinc and E. coli between geographic locations. The analysis indicates that if urban development continues in its current form, increases in urban land cover around New Zealand can be expected to result in further declines in water quality and a reduced likelihood that water quality objectives will be achieved at impacted locations.

The key role of increased fine sediment loading in shaping macroinvertebrate communities along a multiple stressor gradient in a Eurasian steppe river (Kharaa River, Mongolia)

AbstractAquatic communities across the Eurasian steppe face increasing anthropogenic pressures due to rapid population growth, catchment‐wide land‐use changes, and climate change. The particular type, intensity, overlay, and legacy of impacts along longitudinal gradients of Eurasian river networks provide a unique setting to investigate ecological responses in identifiable multiple stressor environments. We studied macroinvertebrate communities along the Kharaa River, Mongolia, which display a distinct, downstream gradient of moderate nutrient enrichment, disturbed bank morphology, reduced riparian vegetation, elevated turbidity, increased fine sediment substrate proportions, and fine sediment intrusion into the hyporheic zone. Within the encountered ranges of physical and chemical environmental factors (TP 0.02–0.09 mg/L, TN 0.33–0.96 mg/L, conductivity 167–322 µS/cm, formazin nephelometric units 0.62–5.43) and hyporheic fine sediment intrusion (0.9–1.6 g dry weight [DW]·L−1·day−1) the population densities and biomass of macroinvertebrates were high (5,313 ± 410 individuals/m2 and 2,656 ± 152 mg DW/m2) and notably stable. In contrast, macroinvertebrate community structure showed strong and statistically significant negative linear relationships (Pearson's r) with turbidity, that is, for taxa richness (r = −.83), Shannon index of diversity (r = −.89), Evenness (r = −.86), the relative abundance of Ephemeroptera, Plecoptera, and Trichoptera (EPT) individuals (r = −.93) and relative biomass of hard substrate colonizers (r = −.86). The relative biomasses of fine substrate colonizers, as well as Chironomidae and Oligochaeta (both r = .76), were positively correlated with mean turbidity values. In addition, the Proportion of Sediment‐sensitive Invertebrates (PSI) methodology was adjusted for local application and the resulting index scores followed a similar pattern, with PSI also being significantly correlated (r = .66) with the relative abundance of EPT individuals, the latter being the most sensitive macroinvertebrate community index. We conclude that fine sediment load is the key factor for shaping macroinvertebrate community structure in the multistressor setting of the Kharaa River followed by hydromorphological habitat complexity determined by shear stress, substrate, and grain size distributions. We suggest that the implementation of effective regional management strategies aiming at the reduction of fine sediment pollution should be given the highest priority.

Keeping an Eye on Wild Brown Trout (Salmo trutta) Populations: Correlation Between Temperature, Environmental Parameters, and Proliferative Kidney Disease.

Proliferative kidney disease (PKD) is an emerging disease of salmonids caused by the myxozoan parasite Tetracapsuloides bryosalmonae, which plays a major role in the decrease of wild brown trout (Salmo trutta) populations in Switzerland. Strong evidence demonstrated that water temperature modulates parasite infection. However, less knowledge exists on how seasonal water temperature fluctuations influence PKD manifestation under field conditions, how further environmental factors such as water quality may modulate the disease, and whether these factors coalesce with temperatures role possibly giving rise to cumulative effects on PKD. The aims of this study were to (1) determine the correlation between seasonal course of water temperature and PKD prevalence and intensity in wild brown trout populations, (2) assess if other factors such as water quality or ecomorphology correlate with the infection, and (3) quantitatively predict the implication of these factors on PKD prevalence with a statistical model. Young-of-the-year brown trout were sampled in 45 sites through the Canton of Vaud (Switzerland). For each site, longitudinal time series of water temperature, water quality (macroinvertebrate community index, presence of wastewater treatment plant effluent) and ecomorphological data were collected and correlated with PKD prevalence and intensity. 251 T. bryosalmonae-infected trout of 1,118 were found (overall prevalence 22.5%) at 19 of 45 study sites (42.2%). Relation between PKD infection and seasonal water temperature underlined that the mean water temperature for June and the number of days with mean temperature ≥15°C were the most significantly correlated parameters with parasite prevalence and intensity. The presence of a wastewater treatment plant effluent was significantly correlated with the prevalence and infection intensity. In contrast, macroinvertebrate diversity and river ecomorphology were shown to have little impact on disease parameters. Linear and logistic regressions highlighted quantitatively the prediction of PKD prevalence depending on environmental parameters at a given site and its possible increase due to rising temperatures. The model developed within this study could serve as a useful tool for identifying and predicting disease hot spots. These results support the importance of temperature for PKD in salmonids and provides evidence for a modulating influence of additional environmental stress factors.

Macroinvertebrate community responses to river impoundment at multiple spatial scales

River impoundment by the construction of dams potentially modifies a wide range of abiotic and biotic factors in lotic ecosystems and is considered one of the most significant anthropogenic impacts on rivers globally. The past two decades have witnessed a growing body of research centred on quantifying the effects of river impoundment, with a focus on mitigating and managing the effects of individual large dams. This study presents a novel multi-scale comparison of paired downstream and control sites associated with multiple water supply reservoirs (n = 80) using a spatially extensive multi-year dataset. Macroinvertebrate community structure and indices were analysed in direct association with spatial (e.g. region) and temporal variables (e.g. season) to identify consistent patterns in ecological responses to impoundment. Macroinvertebrate communities at monitoring sites downstream of water supply reservoirs differed significantly from those at control sites at larger spatial scales, both in terms of community structure and taxa richness. The effect was most significant at the regional scale, while biogeographical factors appeared to be important drivers of community differences at the national scale. Water supply reservoirs dampened natural seasonal patterns in community structure at sites downstream of impoundments. Generally, taxonomic richness was higher and %EPT richness lower at downstream sites. Biomonitoring indices used for river management purposes were able to detect community differences, demonstrating their sensitivity to river regulation activities. The results presented improve our understanding of the spatially extensive and long-term effects of water supply reservoirs on instream communities and provide a basis for the future implementation of mitigation measures on impounded rivers and heavily modified waterbodies.

Inside or Outside: Quantifying Extrapolation Across River Networks

AbstractRegression techniques are often used to predict responses across landscapes or under scenarios describing changes in climate, management, or land cover. The ability of random forests (RFs) and multivariate adaptive regression splines (MARS) to predict flow variability, low flow, Escherichia coli, and a macroinvertebrate community index was compared. Cross validation was applied to test predictive performance across an induced spectrum of interpolation to extrapolation by splitting each data set into two geographical, environmental, and random groups. RF and MARS both represent nonlinear and interacting patterns but showed contrasting ability to interpolate and extrapolate. RF always performed better than MARS when interpolating within environmental space or extrapolating in geographical space. RF models for all four responses were transferable in geographic space but not to environmental conditions outside the training data. Neither technique was successful when extrapolating across environmental gradients, although RF out‐performed MARS, despite RF predictions being constrained by the training data. New methods to quantify interpolation versus extrapolation for predictions are demonstrated. Degree of extrapolation is calculated by transforming both the training data and new predictors in response turnover space. A decline in cross‐validation performance was related to an increase in degree of extrapolation regardless of whether extrapolating in geographical or environmental space. Degree of extrapolation is valuable. It identifies those predictions that are more reliable because they represent interpolation versus those that are more uncertain that represent extrapolation. For example, high degree of extrapolation under climate or land cover change indicates increased risk of producing misleading predictions from both RF and MARS.

Stream health, topography, and land use influences on the distribution of the Eurasian otter Lutra lutra in the Nakdong River basin, South Korea

In South Korea, Eurasian otter (Lutra lutra) habitat has increased since the 1990 s because of legal protection, forest development, and increased public awareness. Although otters have been detected throughout the country, a precise investigation of habitat conditions has not previously been undertaken. We hypothesized that higher values of stream health assessment programme (SHAP) indices would indicate better habitat for otters. Otter distribution based on spraint density was investigated along 600 m riverside transects at 250 sites in the Nakdong River basin. We defined four otter population categories (absent, rare, normal, and abundant) and compared the results with presence and absence data. Use of the four population categories provided more details about habitat conditions than presence and absence analysis. The highest spraint densities were found at higher altitudes, and densities declined in areas with high human density and urbanization. The benthic macro-invertebrate community index was highly positively related to the otter population indices. In terms of fish as prey items, the proportion of species tolerant to environmental change were negatively related to otter indices, otherwise number of species sensitive to environmental change positively related. Overall, stream health assessment indices provided the highest correlations with otter population numbers and distribution.

Finding reference: a comparison of modelling approaches for predicting macroinvertebrate community index benchmarks

ABSTRACTReference benchmarks are needed to assess the contemporary status of rivers and to establish restoration targets. We developed predictive models to estimate site-specific reference values for a macroinvertebrate community index (MCI), which is used to indicate a range of human impacts on wadeable streams. We compared three statistical modelling approaches – general linear, boosted regression tree (BRT) and random forest (RF) – and tested the effect of spatial scale on predictive accuracy by developing national and regional BRT models. Using fitted flexible models (BRT, RF) and resetting predictors to reflect natural state provided the most accurate predictions of reference condition. Variation in reference MCI predictions from national and regional models was within the range observed from methodological and temporal variability. The proportion of native vegetation in upstream catchments was the primary predictor of MCI scores in all models, while secondary predictors varied regionally.

Water quality in New Zealand rivers: current state and trends

ABSTRACTRiver water quality, particularly in lowland catchments, is a matter of concern to the New Zealand public. We assessed river water quality and biological state and trends using data from more than 900 monitoring sites. Parallel state and trend analyses were carried out using all sites and a subset of lowland river sites. Median water-quality state in urban and pastoral land-cover classes was poorer than in exotic forest and natural land-cover classes, and lowland sites in the urban and pastoral classes had the poorest water quality. Nutrient and Escherichia coli concentrations increased and visual clarity and Macroinvertebrate Community Index scores decreased as proportions of catchments in high-intensity agricultural and urban land cover increased. Ten-year trends (2004–2013) indicated recent improvements in ammoniacal nitrogen, dissolved reactive phosphorus and total phosphorus in the pastoral and urban classes, possibly reflecting improved land management. In contrast, trends in nitrate-nitrogen in the exotic forest and cool-dry/pastoral classes indicated worsening conditions.

A novel bacterial community index to assess stream ecological health

Summary In stream ecosystems, bacterial communities play an important role in nutrient and energy cycling processes as they are among the most numerous and active organisms at the basal trophic level of the stream food web. Bacterial communities in stream biofilms have been shown to correlate well with different catchment land use and therefore provide an opportunity for the development of a novel ecological indicator of stream ecosystem health. In this study, a bacterial community index (BCI) model was developed and validated using a national data set of biofilm bacterial community profiles collected from 223 streams across seven geographical regions in New Zealand. The six‐component BCI model was generated using the partial least squares regression method to associate the multivariate bacterial community profile with the macroinvertebrate community index, which is a well‐established indicator of stream health. Despite strong regional clustering of the bacterial community profiles, the BCI was indicative of the level of disturbance in the catchment, as shown by significant correlations with a wide range of independent indicators of water quality, macroinvertebrate community data, ecosystem functioning and catchment land‐use data. The BCI was able to explain 35% of the variation in a multi‐metric index incorporating ten common ecological parameters, suggesting that the stream bacterial communities could provide useful information about the ecosystem integrity. The BCI provides a novel ecosystem assessment tool, which can be used to complement existing stream health measures in the management of anthropogenic impacts on freshwater streams and rivers.

Relationships between invertebrate communities and both hydrological regime and other environmental factors across New Zealand's rivers

AbstractRobust relationships between biological characteristics and hydrological indices are required to provide a quantitative basis for environmental flows. Data from 1075 river sites distributed across New Zealand were used to investigate relationships between invertebrate communities and flow regimes, whilst also including the influence of additional environmental factors. Variance decomposition analysis was used to investigate the proportion of variance explained by hydrological, geomorphological, land cover, and catchment characteristics for the community matrix and each of three biotic indices representing taxon richness, Macroinvertebrate Community Index, and percentage of species in the Ephemeroptera, Plecoptera, and Trichoptera orders. Results showed that hydrological regime contributes a unique component to the explainable variation in the community, but this contribution is overestimated if other explanatory factors are not considered. A gradient forest model comprised of 93 random forest models, each predicting the probability of occurrence of a taxon, indicated the importance of high flows and also other dimensions of hydrological variation for predicting invertebrate taxa and biotic indices. Although many freshwater invertebrates in New Zealand are well adapted to a range of flow conditions through resistance traits and/or rapid colonization, this study suggests that several aspects of the flow regime influence invertebrate communities. These results suggest that environmental flows may be designed to sustain or even optimize specific ecological attributes or taxa, but changes along several dimensions of hydrological variability are likely to disadvantage other taxa and change invertebrate community composition. Copyright © 2014 John Wiley &amp; Sons, Ltd.

A framework for coupling explanation and prediction in hydroecological modelling

Causal explanation and empirical prediction are usually addressed separately when modelling ecological systems. This potentially leads to erroneous conflation of model explanatory and predictive power, to predictive models that lack ecological interpretability, or to limited feedback between predictive modelling and theory development. These are fundamental challenges to appropriate statistical and scientific use of ecological models. To help address such challenges, we propose a novel, integrated modelling framework which couples explanatory modelling for causal understanding and input variable selection with a machine learning approach for empirical prediction. Exemplar datasets from the field of freshwater ecology are used to develop and evaluate the framework, based on 267 stream and river monitoring stations across England, UK. These data describe spatial patterns in benthic macroinvertebrate community indices that are hypothesised to be driven by meso-scale physical and chemical habitat conditions. Whilst explanatory models developed using structural equation modelling performed strongly (r2 for two macroinvertebrate indices = 0.64–0.70), predictive models based on extremely randomised trees demonstrated moderate performance (r2 for the same indices = 0.50–0.61). However, through coupling explanatory and predictive components, our proposed framework yields ecologically-interpretable predictive models which also maintain the parsimony and accuracy of models based on solely predictive approaches. This significantly enhances the opportunity for feedback among causal theory, empirical data and prediction within environmental modelling.

Macroinvertebrate Community and Pollution Tolerance Index in Edion and Omodo Rivers in Derived Savannah Wetlands in Southern Nigeria

We carried out a study of the macroinvertebrates community and pollution tolerance index (PTI) in Edion and Omodo Rivers in Agbede wetlands for eight months (from March to October, 2010). Two stations, upstream and downstream, were chosen for each river. Benthic fauna was sampled fortnightly, using the modified Ekman Grab designed for shallow waters. Eight major taxonomic groups comprising 33 taxa were collected in this study. The dominant groups by percentage density occurrence were Ephemeroptera (45.4%) > Diptera (24.7%) > Decapoda (24.03%). The number of taxa was least for station 2 (14) and was highest (23) for station 4, with highest population density recorded for station 1 (211 individuals). The heterogeneity indices revealed higher values for evenness across the stations except, for station 1 (0.3574). Meanwhile, PTI values showed moderate water quality with range of values from 7 to 16.