Aspects of the composition, pigments and carbon fixation of marine phytoplankton

Omran, Adel Shamsedin Ben (1989) Aspects of the composition, pigments and carbon fixation of marine phytoplankton. PhD thesis, University of Glasgow.

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Abstract

The seasonal variation of phytoplankton biomass in terms of total number of algal cells, chlorophyll a levels and phytoplankton productivity was investigated in the years 1984, 1985, 1986 and 1987 for samples collected from the photic zone (surface and 5 metres depth) at stations 11 and 9, at the Fairlie Channel in relation to the changes in nutrient levels and weather conditions. The seasonal variation in the phytoplankton composition was assessed using microscopic examination of the samples and the qualitative analysis of the different algal pigments. Also investigated was the contribution of the different phytoplankton size fractions to the total photosynthetic activity, including that of net -, nano - and picophytoplankton. Although there is a year to year slight variability in weather conditions and nutrient concentrations during the course of this investigation, certain features recurred annually: 1) The spring diatom increase (spring bloom) occurred in March or early April. 2) The phytoplankton biomass during the summer fluctuated about intermediate levels, althoughon certain occasions they were comparable or higher than those observed during the spring diatom increase and during this period the minimum nutrient levels were recorded. The maximum photosynthetic activities were found during the summer period (1986) in reflection of the favourable weather conditions marking this period. 3) Small to relatively high standing crop levels were recorded during the autumn period with photosynthetic activities comparable to those found during the summer. Relatively high nutrient levels were recorded during the autumn. 4) Low phytoplankton biomass (representing the year minimum) and high nutrient concentrations (representing the year maximum) were found during winter. There was no regular recurring autumnal bloom. With the exception of the findings on 25 May and 6 June, 1984 when the benthic organisms represented a large part of the total population, these organisms were found to be most numerous during autumn and winter months, coinciding with the prevailing conditions. Diatoms were the most dominant fraction of the population mainly during the spring diatom increase of which Skeletonema costatum and Thalassiosira nordenskioldii were the most dominant species; also observed in considerable numbers was Navicula spp. The largest levels of contribution by dinoflagellates to the total phytoplankton biomass were recorded during the autumn months; the dinoflagellate fraction was predominantly composed of the genus Ceratium. Green flagellates were found in considerable numbers during the summer months although they were common in the autumn and winter months of 1986. The seasonal variations of the total phytoplankton biomass and nutrient levels were similar to those observed in the past in the Fairlie Channel. (Abstract shortened by ProQuest.).

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: A D Boney
Keywords: Microbiology, Biological oceanography
Date of Award: 1989
Depositing User: Enlighten Team
Unique ID: glathesis:1989-72301
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 24 May 2019 15:12
Last Modified: 24 May 2019 15:12
URI: http://theses.gla.ac.uk/id/eprint/72301

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