Observations on the Epifauna of the Deep-Water Muds of the Clyde Sea Area, with Special Reference to Chlamys septemradiata (Muller)

Abstract

In the sublittoral survey of the Clyde Sea Area from 1949 onwards it became evident that there is an epifaunal association on the deep-water muds of this area consisting mainly of animals living on the shells of molluscs, particularly Chlamys septemradiata. It also appeared that this deep-water mud epifauna differed in different regions of the Clyde, and that the populations of C. septemradiata themselves differed somewhat. A series of samples were taken in 1951 over a period of seven months (May to December) from different parts of the area. Over 2200 shells were examined and the results analysed. These not only gave details of the epifauna as a whole, but also gave information on the length of life and growth-rate of C. septemradiata and some of the attached animals. The most detailed work on epifauna is that of Gislen (1930). He made a detailed study of Gullmar Fjord and refers to 'epibioses' as he considers both the flora and the fauna. He points out that Petersen's division of infauna and epifauna as corresponding to soft and hard bottoms respectively is not entirely true, and that there is an epifauna of soft bottoms and an infauna of hard bottoms. Thus epibioses are described as biocoenoses of animals and plants which occur entirely above the bottom surface or only have an anchoring organ in the bottom. On soft bottoms in deep water Gislen recognizes three associations; a Pennatula association with no other epifaunal species, a Virgularia association with Cerianthus lloydi Gosse and Bougainvillea ramosa Allman, the latter being found on the naked