The benthic ecology of Loch Linnhe and loch eil, a sea-loch system on the west coast of Scotland. I. The physical environment and distribution of the macrobenthic fauna

Abstract

Loch Linnhe and Loch Eil form the inner part of an extensive sea-loch system on the west coast of Scotland. Brief descriptions of the topographical and hydrographical characteristics of the area are given together with information on the granulometry and total organic carbon content of the sediments. A detailed quantitative faunal list of the macrobenthic species is given and their distribution over twenty-four stations throughout the system is described. The fauna may be roughly sub-divided into four major groups: 1. 1) the deep-mud fauna, approximating to the Amphiura chiajei sub-community of the boreal Amphiura communities, 2. 2) the sandy-mud fauna, approximating to the Amphiura filiformis sub-community of the boreal Amphiura communities, 3. 3) the sand fauna, a mixture of species from the boreal Syndosmya and Venus communities, 4. 4) the gravel and pebble fauna, approximating to the Modiolus epifauna communities. There is considerable intermingling of these groups at many stations and, in addition, a number of ubiquitous species are predominant over a wide range of stations. It is concluded that distinct faunal communities do not exist in the system. Important environmental factors affecting the distribution of species are thought to be sediment-type, bottom current speed and, to a lesser extent, total organic content of the sediment. Depth appears to have little effect on distribution. Possible reasons for the blurring of distinctions between communities in enclosed and inshore areas are discussed.