SEAWEED COMMUNITIES ON THE ARTIFICIAL COASTLINE OF SOUTH EASTERN ENGLAND 1. RECLAIMED SALINE WETLAND AND ESTUARIES IAN TITTLEY
The coastline of south eastern England between northern Kent and Suffolk comprises a complex of estuaries. Since the last glaciation these have undergone considerable changes in coastal configuration, largely due to the effects of rising sea level on soft coastal strata. Man has long inhabited this region and has attempted to stabilise the coastline, originally to prevent flooding, but more recently to improve the coastal environment for industrial, agricultural and amenity uses. Early attempts at sea-wall construction relied on local naturally available materials, usually earth walls with seaward sides stone-pitched. Modern structures employ concrete paving or stepping on the seaward faces; this ensures stability, imperviousness and resistance to abrasion (Minikin, 1963; Barnes, 1977). These and other additions such as groynes and pilings, slipways and quays have created new or alternative habitats for plants and animals. Published accounts of the benthic algal Vegetation on seawalls in the reclaimed wetlands of south eastern England are scant; they include: Price, et al. (1977), Lincolnshire; Chapman (1937), Norfolk; Milligan (1963), Blackwater estuary, Essex; Nisbet (1960), Skippers Island, Essex; Clarke and Tittley (1980), Seasalter, north Kent. The importance of this habitat in England has generally been undervalued; sea-walls in the Netherlands by contrast, have been comprehensively studied (den Hartog, 1959). This project records algal communities on artificial structures and identifies the main differences between these and those in saltmarsh; it augments recent studies in riverine (Tittley, 1985) and open-sea habitats (Tittley, in press). Sites selected for investigation were located in Suffolk, Essex, Kent and Sussex (Figure 1). The north Kent coast site was a wetland area designated by IUCN as internationally important; many of the others of were national or local importance for conservation. Artificial shores were mainly concrete, sometimes boulders, giving way at lower levels to extensive mud-flats. One site (Felixstowe ferry) was a wooden breakwater. Study-areas in adjacent saltmarsh were usually Puccinellia (Common saltmarsh grass) turf, Spartina (Common cord-grass) or Halimione (Sea-purslane) stands.
Methods Algal cover at all artificial sites was studied by belt-transect. Species were sampled and recorded at intervals of 50mm along the transect and at 5 points 100mm apart across the transect; sampling intervals along the transect were extended to 100mm on the more gently sloping and extensive Burnham and Canvey walls, and to 300mm intervals at Upnor. Natural habitats were investigated by sampling 50 points (five 100mm apart, across; ten 50mm apart, down) in a placed 0-25m 2 quadrat.
Trans. Suffolk Nat. Soc. 21