The distribution of pond snail communities across a landscape: separating out the influence of spatial position from local habitat quality for ponds in south-east Northumberland, UK

Ponds support a rich biodiversity because the heterogeneity of individual ponds creates, at the landscape scale, a diversity of habitats for wildlife. The distribution of pond animals and plants will be influenced by both the local conditions within a pond and the spatial distribution of ponds across the landscape. Separating out the local from the spatial is difficult because the two are often linked. Pond snails are likely to be affected by both local conditions, e.g. water hardness, and spatial patterns, e.g. distance between ponds, but studies of snail communities struggle distinguishing between the two. In this study, communities of snails were recorded from 52 ponds in a biogeographically coherent landscape in north-east England. The distribution of snail communities was compared to local environments characterised by the macrophyte communities within each pond and to the spatial pattern of ponds throughout the landscape. Mantel tests were used to partial out the local versus the landscape respective influences. Snail communities became more similar in ponds that were closer together and in ponds with similar macrophyte communities as both the local and the landscape scale were important for this group of animals. Data were collected from several types of ponds, including those created on nature reserves specifically for wildlife, old field ponds (at least 150 years old) primarily created for watering livestock and subsidence ponds outside protected areas or amongst coastal dunes. No one pond type supported all the species. Larger, deeper ponds on nature reserves had the highest numbers of species within individual ponds but shallow, temporary sites on farm land supported a distinct temporary water fauna. The conservation of pond snails in this region requires a diversity of pond types rather than one idealised type and ponds scattered throughout the area at a variety of sites, not just concentrated on nature reserves

Spatial distribution of bivalves in relation to environmental conditions (middle Danube catchment, Hungary)

The spatial distribution of bivalves in relation to environmental conditions was studied along a second- and third order stream – medium-sized river (River Ipoly) – large river (River Danube) continuum in the Hungarian Danube River system. Quantitative samples were collected four times in 2007 and a total of 1662 specimens, belonging to 22 bivalve species were identified. Among these species, two are endangered (Pseudanodonta complanata, Unio crassus) and five are invasive (Dreissena polymorpha, D. rostriformis bugensis, Corbicula fluminea, C. fluminalis, Anodonta woodiana) in Hungary. The higher density presented by Pisidium subtruncatum, P. supinum, P. henslowanum and C. fluminea suggests that these species may have a key role in this ecosystem. Three different faunal groups were distinguished but no significant temporal change was detected. The lowest density and diversity with two species (P. casertanum and P. personatum) occurred in streams. The highest density and diversity was found in the River Ipoly, in the side arms of the Danube and in the main arm of the Danube with sand and silt substrate, being dominated by P. subtruncatum and P. henslowanum. Moderate density and species richness were observed in the main arm of the Danube with pebble and stone substrate, being dominated by C. fluminea and S. rivicola. Ten environmental variables were found to have significant influence on the distribution of bivalves, the strongest explanatory factors being substrate types, current velocity and sedimentological characteristics.The project was financially supported by the Hungarian Scientific Research Fund under the contract No. OTKA T/046180. Special thanks to the DanubeIpoly National Park for the help in field work.info:eu-repo/semantics/publishedVersio

Malacocoenoses of large lowland dam reservoirs of the Vistula River basin and selected aspects of their function

Spatio-temporal variation in qualitative and quantitative occurrence of malacofauna was analysed in three large lowland dam reservoirs. Differences between the malacofauna of flooded land areas and former river beds persist even in middle-aged reservoirs. Quick turnover of water has a positive effect on mollusc abundance and species richness of the whole reservoir, and on the frequency of occurrence in the former river bed. Considerable dynamics of the malacocoenoses and a possibility to revert to earlier development stages, as a result of considerable disturbance, were observed at an advanced stage of biocoenosis development. Besides water dynamics and composition and distribution of bottom deposits, a significant effect on the malacocoenoses is exerted by dominant species, especially D. polymorpha. Abundance and dominance structure of malacocoenoses determine their role in the ecosystem, including accumulation of phosphorus and heavy metals, and their cycling as a result of filtration activity, faeces production, excretion and trophic transfer. Generally, the quantities of elements, especially heavy metals, accumulated in molluscs, are much smaller than the quantities which flow through the malacocoenoses. A large part of the pool of these elements contained in the shells is excluded from circulation for many years. Food chains seem to have relatively little effect on the transfer of heavy metals in the reservoir

Diversity of aquatic malacofauna of temporary water bodies within the lower Bug River floodplain

This study analyses the composition, species richness and diversity (H’) of aquatic molluscan communities in temporary water bodies within the valley of the lower Bug River in eastern Poland. The investigations were carried out in 2007–2009 within the section of the valley located between 190th and 50th km of the river course in 50 water bodies. Relatively rich and diverse malacofauna was found in the investigated habitats: 32 snail species and 6 bivalve species. Species diversity (H’) in individual water bodies ranged from 0.44 to 3.48. About 40% of all mollusc species showed frequencies of _10%. Dominance patterns varied much among the water bodies. Mollusc abundance ranged from 20 to over 1,800 indiv./m2. Considerable species richness and diversity were found both within the active floodplain and the former one. This was probably related to the long duration of many of the investigated water bodies, as well as their periodical hydrological connectivity with permanent ones or river channel. From 9 to 12 samples should be enough to compile representative species list of molluscs inhabiting temporary water bodies, but as many as 28–40 samples would be necessary to obtain complete dataset

Sampling intensity in biodiversity assessment: malacofauna of selected floodplain water bodies

The assessment of completeness of mollusc species lists in selected permanent and temporary floodplain water bodies located within the lower Bug River valley, as well as estimation of the minimum number of samples required to obtain an acceptable efficiency of inventory in individual water bodies, was carried out using sample-based rarefaction curves and non-parametric estimator Chao2. The effect of sampling effort on different measures of species diversity (species richness, Shannon diversity exp(H’)) was examined. Dependence of sampling effort, inventories completeness and diversity measures on habitat stability was analysed by comparing permanent and temporary water bodies. Mollusc assemblages of the investigated water bodies showed high temporal and spatial variability, as well as inter-habitat differences (relatively low Jaccard’s similarity coefficient, J). Significant differences in diversity and composition of mollusc assemblages were found between permanent and temporary habitats, whereas species richness was similar in both permanence groups. In general, both species richness and diversity increased similarly with growing sampling effort. Total richness accuracy reached at least 90% of the predicted value (calculated with Chao2) with 5 to 14 random samples, depending on the water body (10–14 samples in permanent habitats and 5–10 samples in temporary ones)