Catherine A. Duigan

The late-glacial and early-Holocene palaeoecology of cladoceran microfossil assemblages at Kråkenes, western Norway, with a quantitative reconstruction of temperature changes

Cladoceran microfossil remains were analysed from a sediment core taken from a lake basin at Kråkenes, western Norway. The sequence included immediate post-glacial conditions (ca. 12,300 14C BP), the Allerod, Younger Dryas, and early Holocene to approximately 8,500 14C BP. The interpretation of changes in the cladoceran assemblages is based on the known ecology of the taxa, the documented environmental history of the study sequence, the variations in the organic content of the sediment, the radiocarbon dates, and the results of analyses of other biotic groups, including diatoms, macrophytes, and chironomids. In addition, a quantitative reconstruction of changes in air temperature is presented for the study period. This reconstruction is based on transfer functions developed from a separate Swiss surface-sediment cladoceran data set.The cladoceran assemblages throughout the sequence are dominated by littoral chydorid taxa. Bosmina, Daphnia, and Simocephalus represent the open-water component of the zooplankton. Chydorus piger and Daphnia were the only immediate post-glacial pioneer taxa. A rapid proliferation of the open-water and littoral cladoceran taxa began with the onset of the Allerod and persisted for approximately 1,000 yrs. At the start of the Younger Dryas a local glacier formed and drained into the lake, causing a sudden decline in chydorid diversity, with only Chydorus sphaericus and Acroperus harpae persisting throughout this period. Chydorid diversity started to recover in the upper Younger Dryas and continued in the early Holocene. Progressive acidification and oligotrophication are also discernible from the cladoceran assemblages present in the Holocene.The reconstructed mean summer air temperature was from 8-21 °C, with prediction errors of 1.8-2.5 °C. The Allerod was only slightly warmer than the Younger Dryas period, but a progressive increase in temperature is apparent during the early Holocene. In conclusion, the results of this study provide a further demonstration of the value of cladocera as indicators of a variety of palaeoenvironmental parameters, including temperature.

The ecology and distribution of the littoral freshwater Chydoridae (Branchiopoda, Anomopoda) of Ireland, with taxonomic comments on some species

This paper is the first comprehensive review of the littoral freshwater Chydoridae (Branchiopoda, Anomopoda) of Ireland. It reports on a countrywide survey, during which a total of 316 samples was taken at 287 sampling sites between March, 1984 and June, 1986. Together with all previous records, the survey results provide baseline data on the ecology and distribution of this important animal group.A total of 41 taxa in 18 genera of the Family Chydoridae has been recorded in Ireland. Several taxa exhibit morphological differences from original descriptions and populations from other geographical regions, and the taxonomic significance of this variation is assessed. All the taxa encountered during this survey are illustrated by scanning electron micrographs. The distribution of each taxon is given and observations are made on regional trends.

The Krakenes late-glacial palaeoenvironmental project

Kråkenes is the site of a small lake on the west coast of Norway that contains a long sequence of late-glacial sediments. The Younger Dryas is well represented, as a cirque glacier developed in the catchment at this time. This site offers unique opportunities to reconstruct late-glacial environments from independent sources of evidence; physical evidence (glacial geomorphology, sedimentology, palaeomagnetism, radiocarbon dating), and biological evidence from the remains of animals and plants derived from both the terrestrial and aquatic ecosystems. This report describes the background to the site, and the international multidisciplinary project to reconstruct late-glacial and early Holocene environmental and climatic changes at Kråkenes.

A study of the distribution and ecology of littoral freshwater chydorid (Crustacea, Cladocera) communities in Ireland using multivariate analyses

The distribution and ecology of the littoral fresh- water Chydoridae in Irish waterbodies were investigated. A total of 316 samples was taken at 287 substrate classified sampling sites throughout the Republic of Ireland, and rep- resentatives of thirty-two chydorid taxa were collected. Minimum variance clustering and principal components analysis (PCA) of the data set allowed the recognition of three geographically distinct sampling site groups: Western, Central Lowlands and Countrywide. Seven groups of chydorid taxa were identified on the basis of their total frequencies of occurrence, the frequency of co- occurrence of the taxa and occurrence on substrates. Several taxa were shown to have distributions restricted to particular lake groups.

The Anglesey lakes, Wales, UK—A conservation resource

1. The environment of the island of Anglesey, North Wales, UK, is described and related to the ecology of the lake systems present.2. Estimates are given of the number and types of lakes present on the island. Sixteen biological Sites of Special Scientific Interest (SSSIs) have standing water as a recognized habitat feature and their reasons for receiving a conservation designation are discussed.3. Brief reviews are given of the lacustrine flora, invertebrates, fish and aquatic bird populations of Anglesey and their importance in assessing the conservation value of a site.4. These reviews are followed by detailed accounts of the current ecology of three of the islands lake systems - Llyn Coron, Llyn Dinam and Llyn Penrhyn - which occur within biological Sites of Special Scientific Interest. Original data are presented on their physical and chemical characteristics, diatom assemblages, macrophyte communities, littoral and open water zooplankton communities and macroinvertebrate assemblages.5. Artificial enrichment, the introduction of alien species, the legacy of metal mining operations and recreational pressures are identified as the main threats to lake conservation on Anglesey.6. The Anglesey Wetland Strategy, an informal operational level liaison procedure, is described. Using this mechanism, broad targets and indicative strategies are highlighted by the partner organizations active in wetland conservation on the island, and opportunities for collaboration are developed.

The past, present and future of Llangorse Lake - a shallow nutrient-rich lake in the Brecon Beacons National Park, Wales, UK

1. This paper provides an introduction to the ecology and conservation status of Llangorse Lake, a shallow nutrient-rich lake in the Brecon Beacons National Park, Wales, UK. The lake has been designated as a Site of Special Scientific Interest in Britain and was recently proposed as an internationally important conservation site under European Community legislation.2. The water chemistry and biota are indicative of alkaline, nutrient-rich conditions. Water transparency is low and there is evidence of deoxygenation above the surface sediments.3. The epilithic diatom flora exhibits the most diverse assemblage of taxa. Cocconeis placentula and Achnanthes minutissima dominate the epiphytic diatom flora, whilst the surface sediment diatom assemblage is largely composed of planktonic taxa.4. Phragmites australis and Typha latifolia are the dominant components of the emergent stands of marginal vegetation, which is flanked on the open water side by floating-leaved plant communities. Several species of Potmogeton are recorded as parr of the diverse submerged flora.5. The open water and littoral zooplankton assemblages are composed of a small number of cladoceran and copepod species. In contrast, a diverse assemblage of macroinvertebrates with large numbers of individuals is recorded. Oligochaetes are the most numerous group but the Mollusca, Hirudinea, Malacostraca and insects are also well represented.6. Artificial enrichment, power boating and fishery management are highlighted as key considerations for the future conservation of the lake. A number of non-indigenous plant and animal species are reported.7. The organizations that can play a role in the future management of the lake are identified and a number of management planning initiatives are discussed. Copyright (C) 1999 John Wiley & Sons, Ltd.

The ecology and conservation of Llyn Idwal and Llyn Cwellyn (Snowdonia National Park, North Wales, UK)—two lakes proposed as special areas of conservation in Europe

1. This paper gives a comprehensive account of the ecology of Llyn Idwal and Llyn Cwellyn, two nationally well known and internationally important conservation lakes in Snowdonia National Park, North Wales. Idwal has a small but precipitous catchment with relatively large areas of heathland and base rich bare rock. Cwellyn has a larger catchment with a substantial proportion of woodland, including coniferous plantations, and a long history of human activity. 2. The chemistry of the waters in both lakes is indicative of nutrient-poor conditions but Idwal exhibits relatively high alkalinity and pH values. 3. The diatom floras are typical of nutrient-poor upland waters, with species composition reflecting the alkalinity differences. Isoetids form a dominant component of the macrophyte floras, with the most diverse assemblage recorded at Idwal. 4. The zooplankton communities are distinctive, with only a small number of species occurring in both lakes. The macroinvertebrate faunas are dominated by insect taxa typical of stony shores. Supplementary stocking of the Idwal trout population has been reported. 5. The conservation importance of the sites lies primarily in their representation of nutrient-poor mountain lake systems and the macrophyte assemblages which include a number of rare species. In addition, a genetically unique arctic charr population is present in Cwellyn. 6. Impoundment, water abstraction, acidification, eutrophication and the recreational use of the sites are identified as potential environmental impacts. The conservation management of the sites is related to the extent of the reserve boundaries and catchment activities. Aspects of the future management and environmental monitoring of Idwal and Cwellyn as Special Areas of Conservation under the European Community Council Directive on the conservation of natural habitats and of wild fauna and flora are discussed.

Aquatic macrophyte classification, distribution, and traits in British lakes

Aquatic macrophytes are key ecological components of lake systems reflective ofthe environmental conditions. Surveys of lake macrophyte communities underpin nature conservation strategies in Great Britain, with representative plant assemblages and rare plants used as justification for the selection of statutory conservation sites of national and international importance. A recent TWINSPAN analysis of a Joint Nature Conservation Committee data set was used to identify a suite of representative lake groups based on their submerged and floating vegetation (DuiGAN et al. 2006, 2007). Separate ecological descriptions of 11 distinct lakes groups were produced (Table l) anda Plant Lake Ecotype Index (PLEX) was developed. This paper presents the results of supplementary analyses of this dataset, especially relationships between taxon richness and environmental variables. Trait analyses and PLEX scores are used to provide insights into lake ecology and conservation trends.

An appreciation of the life and work of David G. Frey (1915–1992)

The Third International Symposium on Cladocera met without one of its founding figures, Prof . David G . Frey, who passed away on 1 April 1992. Tribute should be paid to him as he was a founding member of the International Symposium on Cladocera and actively involved in all subsequent meetings . As we all appreciate, his outstanding lifes work was dedicated to the study of the taxonomy and ecology of Cladocera, especially the chydorids, and he continually promoted their potential in palaeolimnological studies .