Mericia Whitfield

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.

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.