Habitat point records from 1994 DWT Exmouth to Burton Bradstock (Lyme Bay) survey

The methodology followed that adopted by the regional National Rivers Authority (NRA) in their most recent surveys (National Rivers Authority, 1994a). Four replicates were taken at each site (although due to the smaller area of our corer, 3 closely spaced cores were used for each replicate). The surface area of each replicate was 0.01 square metre. Each core sample was taken to a depth of 15cm where possible (Photo 5b). Where stones prevented penetration to this depth the sample was taken as deep as possible and the actual depth noted. Samples were taken in the lower half of the shore (Mean Tidal Level to Mean Low Water Neap zone). The survey was carried out from 8-10 August 1994, during a period of spring tides. Most samples were taken within an hour of predicted low water; the only exception was Exmouth, where the samples were taken 1 hour 50 minutes before LW. The Ambios Health and Safety procedures were followed at all sites. Samples were carefully sieved through a 0.5mm mesh within 12 hours of sampling. All material retained by the sieve was preserved immediately in Industrial Methylated Spirits (IMS). No stain was added. All material retained by the sieve waas examined at a minumum of x7 magnification under a stereo zoom microscope. Specimens were identified to species level wherever possible (often using a compound microscope) and a reference collection for Lyme Bay was created. Difficult and unusual specimens were sent to independent specialists for confirmation or identification. These specialists were Dr Peter Garwood (polychaetes & crustaceans) Dennis Seaward (molluscs) and Dr Peter Kirby (groups usually encountered in terrestrial surveys.) The species list from this survey has been compared with other recent intertidal invertebrate data for Lyme Bay. This survey confirmed the high conservation value of the lower Exe estuary and Fleet Lagoon for marine invertebrates. Other sites had typical estuarine benthic communities, with a particularly good example near the mouth of the Otter estuary. Unusually impoverished benthic communities were present in the harbour sediments in West Bay and Lyme Regis. These results were probably due to pollution rather than natural causes. Considering that only 8 sites were surveyed, the number of taxa recorded (67) was unusually high for this estuarine/brackish intertidal soft sediment habitat. A very high propotion (42 out of 67) were found only at one site, often in very low numbers. The most unusual taxa recoreded were the polycheates Clymenura clypeata, Spio theeli, Armandia sp (possibly A.cirrhosa), and Syllis sp E (an undescribed species). The number of species recorded in the Fleet and Exe estuary increases with every specialist survey, reflecting the diverse nature of their invertebrate communities. Apart from mussel spat, the densities of the invertebrates were not exceptional when compared to results from other estuaries in the UK. Combined with data from surveys of the Teign, Exe, Otter and Axe by the National Rivers Authority, the data reported here provide a suitable quantative baseline for benthic invertebrates of sand and mud shores around Lyme Bay.

Organization: Joint Nature Conservation Committee