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One of the most obvious effects of eutrophication in sheltered coastal areas and estuaries is enhanced growth of opportunistic macroalgae, which may form extensive mats over intertidal mudflats during the spring and summer. In the Ythan estuary, densities of the amphipod Corophium volutator (Pallas) in the sediment underlying weed mats were significantly lower than those in weed-free sediments, and are dominated by species characteristic of organically enriched, low oxygen environments such as Capitella capitata. Long-term data sets on Corophium abundance in the Ythan suggest that this species has declined dramatically throughout those parts of the estuary affected by weed mats.

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This is an open access article under the terms of the Creat ive Commo ns Attri butio n-NonCo mmerc ial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

The intertidal and subtidal soft-sediment macrofauna of the upper Forth estuary, eastern Scotland, UK has been examined. The intertidal fauna was sampled in 1977, and again in 1988/89, at up to twelve stations along the salinity gradient. The subtidal fauna was sampled in 1982 and in 1988/89 at up to 15 stations. The stations span the region of the freshwater-seawater interface, and area of the turbidity maximum. Large spatial and temporal variations in macrofaunal abundance and species composition were observed. Sites at the head of the estuary with low salinity were dominated by oligochaetes, but more saline areas were characterised by a depauparate estuarine fauna. The area has historically received large quantities of organic waste both from sewage and industrial discharges which supported very high abundances of oligochaetes of up to 500,000 m-2 in the upper reaches of the estuary. Reductions in the organic inflow to the area since the early-1980's have begun to cause reductions in oligochaete populations and also allowed the further penetration intertidally of non-oligochaete species into the upper and middle reaches of the estuary. No comparable upstream penetration by the non-oligochaete subtidal fauna has been observed, possibly on account of the greater sediment instability in the estuary's main channel.

The majority of realignment schemes undertaken in the UK to date have involved breached realignment. However, banked realignment schemes can offer benefits in terms of creating habitats that have greater physical and biological connectivity with the wider estuary. These benefits are illustrated through a case study of a scheme at Welwick in the Humber Estuary, which is one of the few recent managed realignment schemes to involve the wholesale removal of the fronting flood embankment rather than the creation of breaches. In this example, the scheme design was heavily influenced by the requirement to create a compensatory mudflat habitat and, in this regard, the methods used to assess the future evolution of the scheme are described. The paper goes on to discuss the generic design issues relevant to managed realignment schemes at other locations, including the target habitat to be created. It is suggested that the benefits of banked realignment schemes, in terms of delivering more sustainable estuary morphologies, merit increasing consideration by developers in the future.

This paper contains a summary of the key considerations required when designing and implementing a monitoring programme for habitat creation schemes. The success of habitat creation projects can be defined as progress towards the achievement of targets or objectives. The objectives for an individual scheme vary; thus every scheme poses specific information needs, and monitoring efforts need to be tailored to provide this information. Most of the habitat creation schemes which have been implemented to date have incorporated very different monitoring programmes. To maximize the potential functional gain and understanding of habitat creation schemes a consistent approach is required. Guidance is therefore provided on the selection of appropriate parameters to monitor and the associated monitoring techniques. The results of such monitoring will not only enable the evaluation of current objectives but will inform the design and management of habitat creation schemes in the future.

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