Euro-limpacs Deliverables


Report providing a fuller description of the wetland sediment core analysis

This report, follows on from ?Deliverable 59: Report summarising preliminary analyses of wetland sediment cores? which was submitted in month 18 and summarised progress on the three activities planned for the first twelve months in Work Package 3, Task 3.2, Wetland palaeoecology: 1− Selection of wetland site, 2 − Reconnaissance and collection of cores, and 3 − Sampling and processing of cores. This task aims to study a single key site to develop a new palaeoecological method for exploring long−term, nutrient−climate change interactions from sediment records and long−term data−sets in wetlands. The selected study site is Boxford Water Meadows (UK grid reference SU 428719), a Site of Special Scientific Interest (SSSI) which comprises a series of flood pastures and disused water meadows along the River Lambourn, Berkshire, UK.

Deliverable 59 included very preliminary data as the cores were only collected in April 2005. Therefore, here we provide a fuller description of the wetland sediment core analysis (Activity 5). The report focuses on presentation of the preliminary diatom, cladocera and spheroidal carbonaceous particle (SCP) data from a 90 cm Russian sediment core, BOXF1.

Diatom analysis was undertaken at UCL on 18 sub−samples at approximately 5 cm intervals throughout the core. Diatoms were present in all samples although at varying degrees of preservation. Three zones were identified in the diatom record: Zone 1 was dominated by non−planktonic forms, Zone 2 saw higher abundances of planktonic taxa that may signal an increase in water level and Zone 3 saw the expansion of taxa that may reflect an increase in productivity. Cladocera analysis was undertaken at NERI on 10 sub−samples at 10 cm intervals throughout the core. The whole core was dominated by macrophyte associated and benthic chydorids indicating low water level through the period represented by the sediment record. Three zones were identified: Zone 1 contained very few cladocera fragments, Zone 2 saw higher abundances of Alona affinis and Acroperus which could indicate an increase in water level, and Zone 3 saw the disappearance of Alona affinis and expansion of Alona quarangularis which may indicate a reduction in plant cover typically associated with an increase in nutrient concentrations. There is reasonable agreement between the timing and nature of the main shifts in the diatom and cladocera assemblages although both sets of data are difficult to interpret in the context of hydrological fluctuations or productivity changes. A further search of the ecological literature is required to interpret the findings more fully. UCL have screened the core for ostracods and molluscs but unfortunately only a few shells and fragments were found and ostracods were generally rare and poorly preserved.

Analysis of SCPs in 16 samples has been completed by UCL in order to establish an approximate chronology for the core. Preliminary results indicate that the last 150 years lie in the top 25 cm. The SCP data will be verified and a full interpretation of the results will be available by month 36. Sub−samples are currently being prepared for radiometric dating to provide a further independent chronology for the core. The availability of instrumental records will be explored and there may be potential to compare outputs with the INCA nutrient models of the Lambourn catchment developed at University of Reading (link to WP6) and hydrological monitoring data from the LOCAR project.

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