Interactions Between Marine Benthic Invertebrates and Sediments in Intertidal and Deep Sea Environments

West, Fraser James Craig (1999) Interactions Between Marine Benthic Invertebrates and Sediments in Intertidal and Deep Sea Environments. PhD thesis, University of Glasgow.

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Section I investigated the potential use of Mytilus edulis as an environmentally friendly method of protecting intertidal soft sedimentary coastal zones. The section comprises of four main experiments and one set of joint experiments conducted with BSc Honours students. Experiment 1 was a preliminary study of the attachment of Mytilus edulis on to sand (particle size < 500mum), gravel (particle size range between 4mm and 8mm) and a 1:1 mix of sand and gravel. The results showed that in general mussels on gravel produce more threads than mussels on bare sand. This also means that potentially mussels on sand with underlying gravel will be less likely to be washed away by currents as they will attach to underlying gravel thus anchoring themselves. Experiment 2 developed the findings of experiment 1. The experiment involved allowing Mytilus edulis to form clumps on gravel and sand substrates in the laboratory, along with mussels stored in buckets as an un-clumped condition. The mussels from the laboratory were then transported to an intertidal bay, Ardmore Bay in the Clyde Estuary. The results showed that fewer mussels were lost from gravel substrates on the shore than from sand substrates. The effectiveness of using Mytilus edulis as a way of protecting intertidal soft sedimentary coastal zones can be determined by the numbers of mussels remaining on top of the sediment. The more mussels covering the sediment surface will mean that less of the sediment's surface is exposed to currents that would cause erosion. The results would indicate that some kind of artificial substrate is required to allow mussels to remain in situ on a sandy intertidal coastal zone. Experiment 3 was designed to investigate a novel artificial substrate to allow mussels to be introduced to intertidal soft sedimentary environments. The chosen substrate was plastic mesh with fibres measuring 1mm and 2mm and a square aperture measuring 14mm x 14mm. The experiment was conducted in the laboratory to measure the attachment force of the mussels' byssus threads. The results showed that there was no difference in the attachment strength of mussels on to plastic netting or on to other mussels' shells. This suggests that the attachment onto plastic netting would be as secure as the attachments made in the large mussel beds present along most coastlines in the intertidal zone. So this type of substrate could potentially be used to introduce mussels onto intertidal soft sedimentary environments in an attempt physically to reduce erosion. Experiment 4 developed the research of experiment 3. The plastic mesh was used in place of the gravel used in experiment 2. The results were similar to those found in experiment 2. Mussels that had been exposed to the plastic mesh substrate prior to being laid on to the field sand were less likely to be washed away by currents. The result shows that the method and the substrate used in this experiment have a potential to be developed into a large-scale method of environmentally friendly method of protecting intertidal soft sedimentary environments. The set of joint field experiments simply develops the work conducted in experiments 1 to 4 and investigates aspects not covered in experiments 1 to 4. Experimental set 1 investigated the attachments on and around isolated boulders within a 30m x 10m transect line at both the upper and lower intertidal on Ardmore Bay. There were three experiments conducted within this set. The experiments showed that in general there were more mussels lost from the lower intertidal site than the upper intertidal site. This highlights the need for a suitable substrate to allow mussels to withstand higher energy environments. Experimental set 2 investigated the behaviour of mussels laid on to sand substrate on the shore. The mussels were laid with no space between mussels, 1cm gap between mussels and pre-clumped. The results of the three experiments in the set showed differences to those of experiment 2 and 3. The results showed that mussels that had been allowed to form clumps in the laboratory lost fewer mussels than those simply placed on to the sand on the shore. Again, this serves to re-emphasise the need for a suitable artificial substrate to allow mussels to remain in high-energy environments. Section II investigates the affects of an Oxygen minimum zone present off the coast of Oman in the Arabian Sea. The study focuses on the biological mixing, geochemistry and geotechnical properties of the sediments of the area. The parameters measured were Eh, pH, shear strength, biological mixing, water content, carbonate and total organic matter of the sediment samples. Sediment samples from box cores taken at sites both within and below the OMZ were compared. The samples from within the OMZ showed low redox conditions and high carbonate. The geotechnical properties and biological mixing structures within the OMZ also differed to those outside the OMZ. The differences were related to the level of anoxic conditions and water depth.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: Peter S Meadows
Keywords: Biological oceanography
Date of Award: 1999
Depositing User: Enlighten Team
Unique ID: glathesis:1999-76005
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 19 Nov 2019 17:08
Last Modified: 19 Nov 2019 17:08

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