The Water Framework Directive requires all EU Member States to improve, sustainably manage and protect water quality in all surface waterbodies. To achieve this goal the ecological status of all our ...streams, rivers and lakes must be assessed against type-specific reference conditions. A number of distinctive or rare river types were not adequately represented in the development of the existing national river typology in 2005, and so it is not known whether they are sufficiently characterised by the current 12-type river typology or represent distinct types. ‘Rare’ in this context refers to systems with a naturally variable or unusual combination of environmental conditions (e.g. naturally low pH) rather than a limited distribution. The rare or distinctive river types highlighted were: (1) groundwater-dominated rivers; (2) highly calcareous rivers with calcium precipitation; (3) low conductivity, naturally acidic rivers; and (4) rivers strongly influenced by lakes (lake outlets). Whether or not these river types host distinct biological communities has yet to be established. While there is a large body of research on the macroinvertebrate communities, research on other biological quality elements such as diatoms is limited. This paper summarises the literature available on the biological characteristics of these rare or distinctive river types.
A wide range of methods are commonly used to measure deposited fine sediment and quantify substrate quality in rivers as part of bioassessment or monitoring programmes. In this laboratory-based ...experi- ment known amounts of three sediment types （sand, topsoil, peat） were added to mesocosms and four methods of measuring deposited fine sediment; turbidity, estimation of released sediment, Turner-Hillis deposited sediment sampler （DSS） and visual estimation of % surface cover were evaluated. The objective of the study was to evaluate which of these methods for estimating deposited sediment best discriminates between levels of deposited fine sediment added and assesses the effects of inter-observer variability between % surface cover estimations. While turbidity measurement and the resuspension method were strongly related to levels of added sediment, it proved difficult using the two methods to resolve differences between adjacent levels of added sediment e.g. 50 g and 100 g. Surface cover estimations were also strongly related to added sediment levels and were better able to distinguish between adjacent levels of added sediment. Furthermore, we found no significant differences between the % surface cover estimations between observers. Results from this laboratory experiment strongly endorse the use of visual estimation of surface cover in field studies. Further work evaluating the turbidity and resuspension methods under field conditions would also be beneficial.
Multiple stressors affect stream ecosystems worldwide and their interactions are of particular concern, with gaps existing in understanding stressor impacts on stream communities. Addressing these ...knowledge gaps will aid in targeting and designing of appropriate mitigation measures. In this study, the agricultural stressors fine sediment (ambient, low, medium, high), phosphorus (ambient, enriched) and nitrogen (ambient, enriched) were manipulated simultaneously in 64 streamside mesocosms to determine their individual and combined effects on the macroinvertebrate community (benthos and drift). Stressor levels were chosen to reflect those typically observed in European agricultural streams. A 21-day colonisation period was followed by a 14-day manipulative period. Results indicate that added sediment had the most pervasive effects, significantly reducing total macroinvertebrate abundance, total EPT abundance and abundances of three common EPT taxa. The greatest effect was at high sediment cover (90%), with decreasing negative impacts at medium (50%) and low (30%) covers. Added sediment also led to higher drift propensities for nine of the twelve drift variables. The effects of nitrogen and phosphorus were relatively weak compared to sediment. Several complex and unpredictable 2-way or 3-way interactions among stressors were observed. While sediment addition generally reduced total abundance at high levels, this decrease was amplified by P enrichment at low sediment, whereas the opposite effect occurred at medium sediment and little effect at high sediment. These results have direct implications for water management as they highlight the importance of managing sediment inputs while also considering the complex interactions which can occur between sediment and nutrient stressors.
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•Effect of multiple stressors on invertebrate communities is still poorly understood.•Sediment, phosphorus and nitrogen were manipulated simultaneously.•Sediment was the most pervasive stressor particularly at high cover levels.•Multiple stressors interacted in complex ways for several invertebrate metrics.•Improving river ecological quality requires improved management of sediment inputs.
The purpose of this study was to consider the relative importance of several habitat variables in explaining the patterns in the structure of macroinvertebrate assemblages in open-water habitats, in ...relatively intact bogs and fens, which should inform conservation strategies. It was hypothesised that variables relating to the size of the water body would differentiate the communities and that some species would be unique to certain conditions. The macroinvertebrate communities from pools >100 m
2
, 10.1–100 m
2
and
Sphagnum
hollows were characterised using sweep sampling for eight intact peatland sites across four bog types, and related to habitat variables including pool size,
Sphagnum
cover and hydrochemistry. Results showed community composition and structure differed significantly between deep, permanent pools and shallow, drought-sensitive
Sphagnum
hollows, with larger invertebrates, such as Odonates and Dytiscinae, rarely found in the hollows.
Sphagnum
cover accounted for a substantial amount of the variation in community composition. An examination of life-history strategies found species dependent on predictable conditions for juvenile development to be more abundant in pools. In contrast, taxa that could delay juvenile development until conditions were favourable were more abundant in
Sphagnum
hollows. These results highlight the importance of habitat heterogeneity in maintaining macroinvertebrate diversity in peatlands.
Peat is more than 90% water (Shotyk 1988), but the chemical composition of that water can be affected by a number of environmental factors, including geology and hydrology (Shotyk 1988). The ...vegetation present may also affect how quickly and effectively nutrients are utilised (Shotyk 1988), and seasonal changes may determine the amount of nutrients present for the vegetation to use, particularly in ombrotrophic bogs, which rely solely on rainwater for their supply of nutrients (Proctor 1994; Vitt et al. 1995; Tahvanainen et al. 2003). Many of the studies outside of Ireland have focused on the interaction between the chemical composition of bog water and the vegetation present (Clymo 1964; 1973; Hayward and Clymo 1982; Vitt and Bayley 1984; Vitt and Chee 1990; Tahvanainen 2004). Other studies have investigated a possible link between water chemistry and vegetation along a mineral-rich to mineral-poor gradient (Bendell-Young and Pick 1997; Bendell- Young 1999; 2003; Tahvanainen 2004). Numerous studies have examined seasonal variation in water chemistry (Gorham 1956; Clymo 1984; Proctor 1994); however, little has been published in relation to Irish bogs.
Macrophytes are an essential biological element of freshwater aquatic ecosystems and are well known to reflect prevailing ecological conditions in rivers. Their use as bioindicators of nutrient ...status in river systems is widespread yet their reliability is hotly debated. The aim of this investigation was to assess whether macrophytes are reliable indicators of nutrient levels or better applied as indicators of other non-nutrient environmental conditions. The importance of two water-column nutrients; nitrates (N) and orthophosphates (P) were assessed in terms of their influence on macrophyte species richness and diversity in relation to other non-nutrient environmental factors using 395 river plots from Ireland. Then, in this context, the efficiency of macrophytes to detect nutrient levels was assessed by selecting two macrophyte-based water quality assessment tools; the Mean Trophic Rank (MTR) and the Predictions And Classification System for river macrophytes (LEAFPACS2). Finally, the ability of phytosociological communities within these rivers to reflect trophic levels was examined using the same two water quality assessment tools. It was shown that water-column nutrients N and P have a minor influence on macrophyte richness and no significant influence on macrophyte diversity and that MTR and LEAFPACS2 were only weakly correlated with N and P levels. It was concluded that macrophytes are sensitive to environmental changes but respond to a combination of ecological factors rather than N or P alone. Therefore, this study suggests that macrophytes are not the most efficient taxon group to apply when assessing trophic changes in isolation of other non-nutrient factors.
Freshwater acidification continues to be a major problem affecting large areas of Europe, and while there is evidence for chemical recovery, similar evidence for biological recovery of freshwaters is ...sparse. The need for a methodology to identify waterbodies impacted acidification and to assess the extent of biological recovery is relevant to the EU Water Framework Directive, which requires methods to quantify differences in biology between impacted and unimpacted or reference sites. This study presents a new WFD-compliant metric based on diatoms (Diatom Acidification Metric: DAM) for assessing the acidification status of rivers. A database of 558 benthic diatom samples and associated water chemistry data was assembled. Diatom taxa were assigned to one of 5 indicator classes on the basis of their pH optimum, assessed using Gaussian logistic regression, and these indicator values used to calculate a DAM score for each site using weighted averaging. Reference sites were selected on the basis of their acid neutralising capacity (ANC) and calcium concentration, and a regression model developed to predict expected DAM for each site using pH and total organic carbon (TOC) concentration. Site-specific DAM scores were used to calculate ecological quality ratios ranging from ≥1, where the diatom assemblage showed no impact, to (theoretically) 0, when the diatom assemblage was indicative of major anthropogenic activities. The boundary between ‘high’ and ‘good’ status was defined as the 25th percentile of Ecological Quality Ratios (EQRs) of all reference sites. The boundary between ‘good’ and ‘moderate’ status was set at the point at which nutrient-sensitive and nutrient-tolerant taxa were present in equal relative abundance. The methodology was evaluated using long-term data from 11 sites from the UK Uplands Waters Monitoring Network and is shown to perform well in discriminating naturally acid from acidified sites.
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•A new diatom metric for assessing the acidification status of rivers is proposed.•Metric calibrated using reference sites and EU Water Framework Directive-compliant.•Validated at sites with long-term biological and chemical data•Good agreement between diatom ecological status class and long-term data
Rivers are a key part of the hydrological cycle and a vital conduit of water resources, but are under increasing threat from anthropogenic pressures. Linking pressures with ecosystem services is ...challenging because the processes interconnecting the physico-chemical, biological and socio-economic elements are usually captured using heterogenous methods. Our objectives were, firstly, to advance an existing proof-of-principle Bayesian belief network (BBN) model for integration of ecosystem services considerations into river management. We causally linked catchment stressors with ecosystem services using weighted evidence from an expert workshop (capturing confidence among expert groups), legislation and published literature. The BBN was calibrated with analyses of national monitoring data (including non-linear relationships and ecologically meaningful breakpoints) and expert judgement. We used a novel expected index of desirability to quantify the model outputs. Secondly, we applied the BBN to three case study catchments in Ireland to demonstrate the implications of changes in stressor levels for ecosystem services in different settings. Four out of the seven significant relationships in data analyses were non-linear, highlighting that non-linearity is common in ecosystems, but rarely considered in environmental modelling. Deficiency of riparian shading was identified as a prevalent and strong influence, which should be addressed to improve a broad range of societal benefits, particularly in the catchments where riparian shading is scarce. Sediment load had a lower influence on river biology in flashy rivers where it has less potential to settle out. Sediment interacted synergistically with organic matter and phosphate where these stressors were active; tackling these stressor pairs simultaneously can yield additional societal benefits compared to the sum of their individual influences, which highlights the value of integrated management. Our BBN model can be parametrised for other Irish catchments whereas elements of our approach, including the expected index of desirability, can be adapted globally.
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•We modelled a diverse set of aquatic ecosystem services against human stressors.•Weighted expert judgement and data analyses informed the model.•Non-linearity of biological processes is common, but frequently overlooked.•Stressor interactions influence ecosystem-service responses.•Case studies showed similarities and differences in ecosystem service responses.
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