The main object of this investigation was to study the occurrence and distribution of the phytoplankton off the Mumbles, Swansea Bay and record changes in the physical and chemical factors in this area during the period 1990-1992. The data obtained will serve as a basis of comparison with the situation after the planned modification of the sewage outfall in Swansea Bay. Changes in nutrients (N, P, Si), salinity, temperature and rainfall, together with numbers and species composition of the phytoplankton were monitored fortnightly. Measurements were made of pigment concentrations and primary productivity estimated as <SUP>14</SUP>C uptake. Counts were also made of zooplankton. An attempt has been made to correlate phytoplankton parameters and environmental factors. The study revealed a cyclic increase of neoplankton cell numbers, chlorophyll and <SUP>14</SUP>C fixation in the spring. Weather conditions appear to determine the timing of the bloom. Nitrate appears to be the most important nutrient controlling the onset and possible size of the bloom. However, ammonium was present throughout the year, presumably derived from the sewage outfall. Ammonium probably also served as a nitrogen source, since laboratory experiments on isolated nanoplanktonic flagellates indicated low levels of nitrate reductase and analyses for amino acids in phytoplankton samples did not indicate nitrogen starvation even when the nitrate content of the seawater was low. Chlorophyll levels in the water indicated that nanoplankton showed maximum development in the summer, together with dinoflagellates. The occurrence of a nanoplanktonic flora was confirmed by <SUP>14</SUP>C fixation studies. Diatoms were dominant in the net plankton with <i>Skeletonema costatum</i> usually dominating during the spring.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:638362 |
| Date | January 1993 |
| Creators | Okus, E. |
| Publisher | Swansea University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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