A seasonal study of phytoplankton in the photic and aphotic zones of the Firth of Clyde

Al-Harbi, Salim Marzoog (1989) A seasonal study of phytoplankton in the photic and aphotic zones of the Firth of Clyde. PhD thesis, University of Glasgow.

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Abstract

The seasonal variations of the phytoplankton in the photic and aphotic zones in the Fairlie Channel, Firth of Clyde, during the period April 1984 to April 1987 were determined by measuring the changes in chlorophyll a and phaeopigments, nutrient concentrations, total biomass in terms of cell numbers, total particulate matter, oxidizable organic carbon and carbon fixation rates. The phytoplankton composition was also determined in terms of the species present and the balance of planktonic and benthic species present in the suspended populations in both the photic and aphotic zones, as well as the pigment assay by chromatographic analysis. The presence of attached (benthic and epiphytic) diatoms in the suspended algal biomass could, on occasions, be correlated with preceding wind data. Fortnightly samples were collected from two stations in the middle of Fairlie Channel. The seasonal patterns of phytoplankton, nutrients and productivity for the photic zone in this Channel were similar to those obtained in the past studies. The general seasonal variations for this zone in the present study for cell numbers and carbon fixation followed the chlorophyll a changes with high values of these parameters during the peak periods of phytoplankton quantities in the spring, on some occasions in summer and autumn, whilst in the winter months these gave the very low measurements. Similar general trends of chlorophyll a, total cell numbers and carbon fixation rates were obtained in the aphotic zone throughout 1984-1987 with lower levels than that in the photic zone, although occasionally comparable high values were obtained during spring, summer and autumn, so reflecting the links between increases of the photic phytoplankton biomass and aphotic populations. The phytoplankton composition was always dominated by Skeletonema costatum in the spring outburst period constituting 92-98% of total biomass during 1985-1987 in the photic and aphotic zones, with a similar phytoplankton population in both zones. Nutrient levels were generally higher in the aphotic zone, indicating its likely role as a nutrient reservoir. The samples incubated in the laboratory for carbon fixation measurements during 1986 have given some indication of potential activity of phytoplankton in the natural environments. These studies have revealed the viability of the aphotic zone phytoplankton populations, with a retained capability of photosynthetic activity once returned to the lighted regions, although the stress effects of a prolonged residence in the dark regions would counteract this potential activity.

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:1989-72297
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/72297

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