Penny Williams

Comparative biodiversity of rivers, streams, ditches and ponds in an agricultural landscape in Southern England

Information about the relative biodiversity value of different waterbody types is a vital pre-requisite for many strategic conservation goals. In practice, however, exceptionally few inter-waterbody comparisons have been made. The current study compared river, stream, ditch and pond biodiversity within an 80 km2 area of lowland British countryside. The results showed that although all waterbody types contributed to the diversity of macrophytes and macroinvertebrates in the region, they differed in relative value. Individual river sites were rich but relatively uniform in their species composition. Individual ponds varied considerably in species richness, with the richest sites supporting similar numbers of taxa to the best river sections, but the poorest sites amongst the most impoverished for all waterbody types. At a regional level, however, ponds contributed most to biodiversity, supporting considerably more species, more unique species and more scarce species than other waterbody types. Streams typically supported fewer species and fewer unique species at local and regional level than either ponds or rivers. Ditches (most of which were seasonal) were the least species-rich habitat, but supported uncommon species, including temporary water invertebrates not recorded in other waterbody types. Multivariate analysis indicated that permanence, depth, flow and altitude were the main environmental variables explaining invertebrate and plant assemblage composition. The findings, as a whole, suggest that ponds and other small waterbodies can contribute significantly to regional biodiversity. This contrasts markedly with their relative status in national monitoring and protection strategies, where small waterbodies are largely ignored.

Temporary and permanent ponds: An assessment of the effects of drying out on the conservation value of aquatic macroinvertebrate communities

Abstract This study was designed to investigate whether temporary ponds were markedly different from more permanent ponds in terms of their species richness, species rarity and community type. Macroinvertebrates were recorded from six temporary ponds in Oxfordshire, and the resulting data were compared with species data from 33 Oxfordshire ponds of a more permanent character. Classification and ordination using TWINSPAN and DECORANA suggest that there were marked differences in the macroinvertebrate assemblages of temporary and permanent ponds. Overall, temporary ponds had similar rarity indices to permanent ponds. However, four of the five highest rarity index values were from temporary or semi-permanent sites. The number of aquatic species was significantly lower in the temporary ponds.

A comparison of the catchment sizes of rivers, streams, ponds, ditches and lakes: implications for protecting aquatic biodiversity in an agricultural landscape

In this study we compared the biodiversity of five waterbody types (ditches, lakes, ponds, rivers and streams) within an agricultural study area in lowland England to assess their relative contribution to the plant and macroinvertebrate species richness and rarity of the region. We used a Geographical Information System (GIS) to compare the catchment areas and landuse composition for each of these waterbody types to assess the feasibility of deintensifying land to levels identified in the literature as acceptable for aquatic biota. Ponds supported the highest number of species and had the highest index of species rarity across the study area. Catchment areas associated with the different waterbody types differed significantly, with rivers having the largest average catchment sizes and ponds the smallest. The important contribution made to regional aquatic biodiversity by small waterbodies and in particular ponds, combined with their characteristically small catchment areas, means that they are amongst the most valuable, and potentially amongst the easiest, of waterbody types to protect. Given the limited area of land that may be available for the protection of aquatic biodiversity in agricultural landscapes, the deintensification of such small catchments (which can be termed microcatchments) could be an important addition to the measures used to protect aquatic biodiversity, enabling ‘pockets’ of high aquatic biodiversity to occur within working agricultural landscapes.

Restoration of the rivers Brede, Cole and Skerne: a joint Danish and British EU‐LIFE demonstration project, V—short‐term impacts on the conservation value of aquatic macroinvertebrate and macrophyte assemblages

1. This paper describes the short-term effects of river restoration on the wetland macrophyte and aquatic macroinvertebrate assemblages of two rivers, the R. Brede (Denmark) and the R. Cole (UK). The effects of the restoration work were assessed in terms of changes in species richness, rarity and abundance on (i) the restored sections and (ii) potentially impacted sections downstream of the restoration works. 2. In the restored areas of both rivers the species richness of wetland macrophyte assemblages recovered to at least pre-restoration levels 1–2 years after restoration. Macroinvertebrate species richness recovery was more variable. The abundance of macroinvertebrates and wetland macrophytes generally recovered less rapidly than species richness. For wetland macrophytes, the recovery process was enhanced by the presence of refugia. 3. Uncommon invertebrates were slower to recolonize the restored sections in the year after restoration (monitored on the R. Cole only). The number of uncommon wetland macrophyte species recorded was similar throughout the restoration and recovery period. 4. Potentially impacted sections of the river up to 1.2 km downstream of the restored area showed a relative decline in invertebrate species richness 1–2 months after the physical works were completed, but little difference from pre-restoration levels after 1 year. Plant surveys downstream of the restored area showed no evidence of a significant change in species richness, neither was there evidence that uncommon plant or invertebrate species were affected by downstream impacts (sediment or nutrient release) due to restoration.

Ecological considerations in pesticide risk assessment for aquatic ecosystems

Risk assessment of pesticides for aquatic ecosystems is typically based on comparisons of exposure and effect concentrations at a variety of levels (tiers). At the highest tier, effects assessment can involve generating data under field conditions, typically in mesocosm experiments. However, interpreting the ecological significance of effects measured in these studies can be difficult because ecological factors can influence the outcome of perturbations in the real world. The influence of ecological factors is not readily addressed experimentally and so a strategic modelling approach is proposed which may aid in defining acceptability of effects.

The influence of simulated immigration and chemical persistence on recovery of macroinvertebrates from cypermethrin and 3,4-dichloroaniline exposure in aquatic microcosms

BACKGROUND Chemical dissipation and organism immigration are considered important factors that influence recovery potential from perturbation of aquatic macroinvertebrates. Experiments were conducted to investigate the effect of simulated immigration on recovery of aquatic macroinvertebrates exposed in outdoor microcosms to ecotoxicologically similar concentrations of the rapidly dissipating pyrethroid insecticide cypermethrin (70 ng L(-1)) or the more persistent herbicide intermediate and degradate 3,4-dichloroaniline (10 mg L(-1)). Microcosms were covered with light-permeable mesh to prevent recolonisation. Immigration was simulated by the regular addition of organisms after treatment. RESULTS Microcosms exposed to 3,4-dichloroaniline treatment suffered substantial loss of taxon richness and by 10 months after treatment had only recovered where invertebrates had been added. Those treated with cypermethrin underwent an initial decline in certain crustacean and insect populations. These populations showed some signs of recovery over a period of 5 months through internal processes alone. However, rate of recovery was further enhanced where immigration was simulated, and in this case recovery had occurred around 100 days after treatment. CONCLUSION Although not the only factors involved, simulated immigration and chemical fate clearly influence the ability of communities to recover from chemical exposure. Consideration of immigration processes and development of models will help to increase the realism of risk assessments.

Finding clean water habitats in urban landscapes: professional researcher vs citizen science approaches

This study investigated patterns of nutrient pollution in waterbody types across Greater London. Nitrate and phosphate data were collected by both citizen scientists and professional ecologists and their results were compared. The professional survey comprised 495 randomly selected pond, lake, river, stream and ditch sites. Citizen science survey sites were self-selected and comprised 76 ponds, lakes, rivers and streams. At each site, nutrient concentrations were assessed using field chemistry kits to measure nitrate-N and phosphate-P. The professional and the citizen science datasets both showed that standing waterbodies had significantly lower average nutrient concentrations than running waters. In the professional datasets 46% of ponds and lakes had nutrient levels below the threshold at which biological impairment is likely, whereas only 3% of running waters were unimpaired by nutrients. The citizen science dataset showed the same broad pattern, but there was a trend towards selection of higher quality waterbodies with 77% standing waters and 14% of rivers and streams unimpaired. Waterbody nutrient levels in the professional dataset were broadly correlated with landuse intensity. Rivers and streams had a significantly higher proportion of urban and suburban land cover than other waterbody types. Ponds had higher percentage of semi-natural vegetation within their much smaller catchments. Relationships with land cover and water quality were less apparent in the citizen-collected dataset probably because the areas visited by citizens were less representative of the landscape as whole. The results suggest that standing waterbodies, especially ponds, may represent an important clean water resource within urban areas. Small waterbodies, including ponds, small lakes<50ha and ditches, are rarely part of the statutory water quality monitoring programmes and are frequently overlooked. Citizen scientist data have the potential to partly fill this gap if they are co-ordinated to reduce bias in the type and location of the waterbodies selected.