AQUATIC INVERTEBRATE SURVEY OF OULTON MARSHES
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OULTON MARSHES – AN AQUATIC INVERTEBRATE SURVEY OF THE TURF PONDS AND DYKES ADRIAN CHALKLEY Four turf ponds were excavated in 2011 at the Suffolk Wildlife Trust Reserve, Oulton Marshes and six more in 2013 (Plates 8 & 9). These ten ponds were among 21 areas of the reserve surveyed between August 2013 and September 2014. The methodology followed that in the ISIS handbook produced by Natural England. In total 908 records were made comprising 174 distinct invertebrates, belonging to 19 orders. 34 of these were only found within the turf ponds. Five species were new county records. The results were analysed and compared to the same analysis carried out on an earlier survey from 2008. Water quality for the 5 sites in the earlier survey ranged from poor to good whereas the 21 sites from the current survey ranged from good to excellent. The invertebrate communities at each site were classified using the Environment Agency CCI metric. At the time of the 2008 survey all sites were of moderate conservation value. All 21 sites in this survey exceeded moderate and 8 were rated as of very high conservation value which equates to the rating an SSSI should achieve. Comparing species lists from each site showed that: Constructing the turf ponds has increased the range of distinct habitat types available to aquatic invertebrates within the reserve. The biodiversity of the aquatic invertebrate community has increased since the site was bought. The turf pond invertebrates did not mirror the general dyke community, they exhibited a more diverse range of species. The invertebrate communities in the turf ponds were formed only partly by dispersal from dykes across the site, they also came from outside the reserve. In the centre of the reserve are two old ponds whose invertebrate communities were found to be similar to that of the dykes but had little in common with those in the turf ponds. Ongoing management at Oulton, of which turf pond construction is part, has considerably increased the conservation value of the overall invertebrate community since the reserve was acquired. Introduction When the Suffolk Wildlife Trust purchased Oulton Marshes in 2008 an initial survey of the dykes and ditches was carried out by Derek Howlett and Roy Baker of the Wheatfen Partnership. After a programme of dyke dredging and re-profiling during 2009-2010 a repeat survey was carried out. The report on these surveys showed that biodiversity in the invertebrate fauna had increased and predicted that with sympathetic management it should continue to increase further. Meanwhile results from long term monitoring of turf ponds created, or re-created, by the Broads Authority since 1983 indicated that these shallow peat diggings could still be a good method of providing a richly improved, diverse fen vegetation once
Trans. Suffolk Nat. Soc. 51 (2015)