AN AQUATIC INVERTEBRATE SURVEY OF ICKWORTH PARK, SUFFOLK
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AN AQUATIC INVERTEBRATE SURVEY OF ICKWORTH PARK, SUFFOLK DAVID J. LEEMING AND STUART WARRINGTON Introduction Aquatic invertebrates are a particularly valuable suite of species for the assessment of the habitat quality of wetland sites. This is because their life cycles are relatively long, they live in intimate contact with the water and sediments, they are relatively sedentary and they exhibit a range of tolerances to pollutants and habitat change. In addition, for many aquatic taxa there is a good level of knowledge about their habitat requirements, their distribution and rarity and, importantly, there are good identification keys available. Ickworth Park, owned by the National Trust, in west Suffolk is probably most renowned for its parkland habitat with many veteran trees, especially oaks. However, it does also have a number of wetland habitats. The main wetland feature is the River Linnet, a small river which enters the park in the south-east corner, and sweeps through a wide valley turning clockwise to exit the park to the north. The River Linnet has been dammed in two places to create the Fairy Lake and The Canal. In addition, there are numerous ponds around the estate, both in the woodland and in the grassland. The aim of the survey was to examine a range of the wetland habitats at Ickworth for their aquatic invertebrate assemblage to help in the assessment of these habitats and to inform possible management. The species included in the survey were macroinvertebrates that complete all or part of their lifecycle underwater. Methods The survey was carried out on 6th August 2003. At each sample site, the collection of aquatic invertebrates was by the active use of a long-handled pond-net, employing a combination of kick-sampling and net-sweep techniques, for a total duration of three minutes, supplemented by a hand search of appropriate surfaces or objects (where necessary). All parts of a site (centre, margins and extreme edges) were sampled, except where a combination of deep water or deep silt precluded access. Care was taken to ensure collection of invertebrates from both open-water and densely vegetated areas. Attention was given to sampling amongst different vegetation types and/or detrital habitats that were present. Sweeps of the net were also used to collect surface-dwelling invertebrates on arrival at the site, prior to disturbance of the sampling area, or whenever such taxa were seen during sampling. Open water areas were sampled by broad, swift sweeps of the net. Soft silts, including muddy edge habitats, were sampled by skimming their surface with the pond net (to a depth of 2–5 cm). The extreme edges or undercut banks of particular ponds were sampled by splashing and subsequent netting of displaced macroinvertebrates. Wet areas of reed or fen litter were sampled by creating puddles through trampling, followed by sweep netting. The sampling approach followed is capable of collecting perhaps 60–80% of the taxa actually present at the time of the sampling (Furse et al, 1981).
Trans. Suffolk Nat. Soc. 40 (2004)