The class Bivalvia is of interest to ecologists studying pollution as it comprises sedentary filter-feeding invertebrates which accumulate pollutants from the environment. In particular mussels have been popular material for experimental studies. They are resistant to a wide variety of environmental conditions and they show a marked capacity to adapt to extremes of environmental change. Some aspects of the physiology of the mussel (Mytilus edulis) were studied in the first part of this thesis. The methods available to determine mussel pumping rate and filtration rate were modified and the resultant data compared with published information. These studies showed that the two bacteria Serratia marcescens and Bacillus subtilis var. niger were retained efficiently by Mytilus edulis during laboratory experiments. M. edulis from a mussel bed on a sewage polluted shore were sampled after separate release of the same two tracer bacteria and the temporal and spatial distribution from the point source were determined. The concentration by the mussels of S. marcescens and of B. subtilis var. niger was compared with their concentrations in the overlying water and with coliform distribution in the same area. Tracer bacteria were present in mussel tissue at higher levels than those existing in the water and detectable numbers were isolated from the shellfish for much longer periods. The higher numbers of tracer bacteria in mussel tissue were often associated with the higher coliform densities in the mussel tissue. These results were discussed in relation to some seasonal and climatic factors. Some aspects of the physiology of the tracer bacteria were studied, in particular the production of black pigment by B. subtilis var. niger L. Several media ingredients and cultural conditions were varied in an attempt to enhance this black pigmentation. In particular, the effects produced by yeast extract, trace elements, low nutrient levels and the absence of tyrosine were noteworthy. The new media which were devised caused all three strains of B. subtilis var. niger to yield maximum pigment density by all colonies within 48-72 hours. Pigment production was enhanced for spread plate, pour plate and membrane filtration technique.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:635718 |
| Date | January 1980 |
| Creators | Al-Salihi, S. B. S. |
| Publisher | Swansea University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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