Monitoring of sublittoral sites within Sandown Bay

Sandown Bay lies on the eastern side of the Isle of Wight, off the south coast of England. It is within the South Wight Maritime Special Area of Conservation (SAC). One of the notified features of the SAC are its sublittoral reefs.

In the mid-1990s, a very large infrastructure project was envisaged by Southern Water plc for the whole of the Isle of Wight, in which a number of untreated waste water outfalls were to be dismantled and re-routed into one long (3 km) sea outfall in Sandown Bay. As the construction work for this outfall would likely have an impact on the featured sublittoral reefs of the SAC, English Nature insisted that Southern Water establish a monitoring programme of reef communities.

D3.13_Milford H 2003_Amphipod tubes_LR D3.16_Milford H 2003_Pagurus berhardus_crpT2.03_Milford H 2003_Ophiura_crp

Sandown Bay is a depositional area which allows for large amounts of silt to settle out of suspension, particularly during neap tides and periods of calm weather. Animals which thrive in these conditions include the unusual tube-building amphipod Ampelisca spp., the large hermit crab Pagurus bernhardus and the brittlestar Ophiura ophiura (above).

Sandown IoW 2002_Carpet tile_2Sandown IoW 2002_Carpet tile_1

Together with our colleagues at EMU Ltd., Sea-Scope assisted with the design and implementation of a novel monitoring strategy. This involved using 25 cm x 25 cm squares of doormat (above) fixed to horizontal rock surfaces which were able to contain settling silt in a similar way to the biotic communities around them. The doormat tiles were lifted (and replaced with ‘clean’ ones) on a weekly basis during the 8-week construction phase. The dry weight of the trapped silt was measured and compared to doormat tiles positioned some distance away at control sites.

The report written at the end of this project was:

Thomas, N., Irving, R.A. & Weir, J. 2000. Sandown seabed – construction impacts study – sediment report. Report by Emu Ltd. for Southern Water Services. Report No. 00/22120/206.