Species point records from 1987 OPRU HRE Looe Estuary littoral survey

The Looe estuary is situated on the south coast of Cornwall due south of Liskeard. The banks of this small estuary have been straightened and protected by the construction of harbour walls, embankments for the railway on the east bank of the estuary, and the stabilization of the banks on bends with revetments of cobbles and boulders held in position by plastic coated wire. The western bank is more natural at the mouth with a steep bedrock shore down to about 1m ACD. The shores of the estuary are chiefly sedimentary with sand amongst small boulders and cobbles in the lower reaches, and sand banks near the junction of the two rivers. Areas where water currents are slower have muddier sediments with fringing saltmarsh appearing on the upper shores from Trenant Wood northwards. Although the fresh water inflow from the two rivers is small the estuary is also small and shallow so that at low water at spring tides the water in the channel is very brackish even at the mouth of the estuary which dries except for a residual channel. The estuary is scenically appealing and a very popular tourist destination. The present survey carried out in July 1987 aimed to collect information on the communities and habitats present in the estuary that had not previously been described. A total of four sites were visited. The abundance of species living on hard surfaces and visible on the surface of sediments were recorded in situ. Intertidal sediment fauna was collected in 0.01m2 cores and by digging, and samples were sieved over 1mm and 5mm mesh sieves. Animals were picked out of the sediments, identified and counted. Photographs were taken to illustrate habitats and communities. A series of aerial photographs was taken during a low water period of spring tides in April 1986. Within the estuary, Habitat diversity is relatively low with predominantly sedimentary lower shores bounded by walls, revetments and natural shores of rock, mixed substrates and marshes. Mid-tide regions of steep bedrock shores and walls in the south of the estuary were dominated by limpets, Patella sp and barnacles of which Chthamalus montagui was the most common species; other species were few. The lower shores were dominated by mussels, Mytilus edulis and green algae, Ulva sp and Enteromorpha sp. Here too species variety was low. Further upstream within the estuary, for example at Trenant Wood, stable hard substrate communities were dominated by fucoid algae and Enteromorpha sp with recorded macrofauna being restricted to Ligea oceanica on the upper shore and Littorina littorea and amphipoda indet. under weed and stones. Also in this area small patches of fringing saltmarsh have developed. The infauna from two different types of sediment on the lower W. Looe Estuary was characteristic of what might be expected in upper estuarine sediments. A sandy silt midshore bank was found to be dominated by Oligocheate worms, ragworms, Hediste diversicolor and amphipods, Corophium volutator. A few other species were very sparsely represented. In current-swept sand banks lugworms, Arenicola marina and the polycheate worm Pygospio elegans were the only species found in any numbers with a few individuals of a small number of other species. In the streambed, from the junction of the two rivers northwards, stable hard substrates were dominated by green algae, Ulva sp and Enteromorpha sp and Fucus ceranoides a fucoid algae indicative of low salinity conditions. The scientific and nature conservation importance of the area has been assessed using standard criteria. These have been applied to each of the habitats and communities identified which have then been provisionally graded as being of Local, Regional, National or International Importance. No species of particular scientific interest were found during this survey work. Of particular interest in this area, but not included in this survey, are the rocky shores around the mouth of the Looe Estuary and the lagoon known as the Millpond near the junction of the East and West Looe rivers.