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An Investigation into changes in the phytoplankton community in Loch Creran, a Scottish sea loch

Whyte, Callum T.

Authors

Callum T. Whyte



Abstract

Short term and irregular sampling in Loch Creran over recent decades suggested that changes may be occurring in the phytoplankton community in the loch. This study sought to confirm this suggestion. After instigating a regular sampling regime during 2008 and 2009 it became clear that significant changes had occurred, relative to information from the 1970s, in both the numbers of phytoplankton in the loch and in their biomass, particularly during the time of the spring bloom. Utilising a tool to assess change in the phytoplankton community, it also became clear that significant changes had occurred in the composition of the phytoplankton in Loch Creran. Work was undertaken to explore possible explanations behind these changes.
The effect that toxic, anti-fouling compounds, arising from an increase in leisure boating in Loch Creran, were having on the productivity of phytoplankton in the loch was considered by adapting an existing assimilative capacity model for phytoplankton growth. It was found, that at present levels of boating activity, the concentration of anti-fouling products present in the loch, would not be great enough to significantly impact on phytoplankton growth.
Nutrient samples collected during 2009 showed no significant changes in the concentration of silicate or nitrate in the loch, but phosphate levels were found to be significantly lower. A review of the effects of grazing on phytoplankton by farmed mussels in Loch Creran indicated that, at current levels, this would not account for the decrease in phytoplankton numbers observed in the loch.
Significant changes were observed in the water temperature in the loch and in the intensity and pattern of local rainfall. Increased levels of rainfall in the first three months of the year were found to be high enough to influence the rate of flushing and the rate of phytoplankton washout from the loch. A correlation was found between the availability of light in the surface layers of the loch and the concentration of phytoplankton present in these layers. This correlation was found to exist, throughout the year and not only, as previously thought, during the winter months.
In conclusion, the observed decline in phytoplankton numbers in Loch Creran, was attributed to changes in local weather patterns, that had an impact on the physical structure of the water column, washout rates, the pattern and intensity of heterotrophic grazing and the availability of light.

Thesis Type Thesis
Deposit Date Oct 24, 2012
Peer Reviewed Not Peer Reviewed
Keywords phytoplankton; weather patterns; environment; Loch Creran;
Public URL http://researchrepository.napier.ac.uk/id/eprint/5696
Contract Date Oct 24, 2012
Award Date 2012

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