Studies of burrows in recent sublittoral fine sediments off the west coast of Scotland

Pye, Malcolm Ian Anthony (1980) Studies of burrows in recent sublittoral fine sediments off the west coast of Scotland. PhD thesis, University of Glasgow.

Abstract

The burrows of the smaller macrofauna, principally polychaetes, bivalves and echinoderms are described from aquarium studies and from X-ray radiographs of boxcore subsamples obtained with a Reineck boxcorer from both sealochs and open marine sites encompassing a range of depths from 25-2l6m and sediments from sandy to fine muds. A model relating burrow types to depth is presented. Shallow sea loch sites are characterised by the deep U-burrows of the bivalve Thracia, deep sea lochs by a paucity of burrows due to the low oxygen levels found in the overlying waters. Shallow marine sites display a diverse suite of polychaete burrows and tubes and the burrows of the ophiuroid Amphiura. Two deep marine areas (>I00m) have been sampled, each characterised by capitellid polychaetes: in the Firth of Clyde the wavy burrows of Dasybranchus are found whereas in the Sound of Jura the spiral burrows of Notomastua are abundant.

Trophic group amensalism does not occur in these muds; the suspension feeding bivalves Thracia. Mya and Arctica are found as there is no tidal resuspension of the sediment.

From boxcores obtained in the vicinity of the Garroch Head Sludge Dumping Ground, Firth of Clyde and near a pulp-paper mill situated between Lochs Linnhe and Eil, a model relating burrow types to organic enrichment of the sediment is presented. In the transitory zone there is an increased number of burrows compared to the normal situation. In the polluted zone the normal fauna is replaced by opportunistic polychaetes, chiefly Capitella capitata. and the upper layers of the sediment are riddled with their burrows.

The method developed of serially X-raying boxcores allows quantitative studies of the density and depth distribution of burrows. The total length of burrows in a boxcore shows a peak of around 250cm in shallow sea loch and deep marine sites. The reduced length of burrows in shallow marine sites may be due to the presence of the burrowing echinoid Brissopsis which does not create a distinctive biogenic trace in these fine grained sediments. On average, burrows occupy 0.1% by volume of the top 5cm of the sediment but represent an increase in surface area of 10%.

Studies of the spatial distribution of burrow entrances, an important diversity regulating mechanism, reveal patches of various dimensions at some sites especially in the Arran Beep.

This ichnocoenose is compared to others from Recent sublittoral, fine sediments inhabited by brittle star communities in the Atlantic, Mediterranean and North Sea and to the ichnocoenoses of sheltered, intertidal sandflats in the U.S.A. The results of this study are used to suggest the possible producers of trace fossils commonly found in fine grained sediments: Chondrites and Planolites are ascribed to polychaetes, Scolicla to gastropods and Thalasainoides to crustaceans.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Geology
• Colleges/Schools: College of Science and Engineering > School of Geographical and Earth Sciences
• Supervisor's Name: Supervisor, not known
• Date of Award: 1980
• Depositing User: Enlighten Team
• Unique ID: glathesis:1980-82752
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 17 Mar 2022 16:23
• Last Modified: 08 Apr 2022 16:44
• Thesis DOI: 10.5525/gla.thesis.82752
• URI: https://theses.gla.ac.uk/id/eprint/82752