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Title: The effects of pollutants, in particular copper, on the zooplankton of a Scottish west coast sea loch
Author: Foster, Richard W.
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 1976
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Abstract:
The feeding and respiratory behaviour of zooplankton, in partioular the copepods, was examined and the effect of copper and mercury on their feeding studied. Feeding rate is expressed as the volume swept clear by an animal per day and termed 'filtering rate' or 'grating rate') respiration is expressed as the weight of oxygen used per day by the animals. Preliminary work to derive suitable experimental conditions showed that filtering rates were affected by the number of animals in feeding containers but were apparently unaffected by the size of the feeding container. The longer an experiment was run, the lower were the filtering rates. Respiration rates were not affected by the duration of an experiment or the density of animals in an experimental container. The means of agitation employed during an experiment affected respiration rates but not feeding rates. The gracing and respiration rates of a natural population of copepods from Loch Ewe, Hester Ross, Scotland, grazing in natural population phytoplankton from Loch Ewe were measured at three weekly Intervals throughout 1971. Feeding rates were estimated by measuring changes of ohlorophyll and concentration in the grazed phytoplankton samples: chlorophyll a, gives a good indication of the amount of plant material present in natural sea water. Respiration rates were measured using the Winkler technique. The experiments showed that both feeding and respiration rates, even if corrected for the differences in weight of the animals during the year, rose during the spring outburst in phytoplankton production, fell and then rose again during the second rise in plant production in late late summer. Experiments confirmed that the filtering rates of the copepods rise in response to increased food supplies, although this response may be seasonally adjusted. aWhen the filtering and respiration rates of the copepod were combined with information obtained by other workers at Loch Ewe on primary production and standing stock of particulate carbon and of zooplankton throughout the year, it was found that the experimentally derived filtering rates would enable the copepods to catch enough food to meet their respiratory requirements, except during the winter However, the copepods appeared to have eaten only approximately 40% of the primary production compared with an expected value of twice this percentage. Further studies showed that if the uneven distribution of the animals and plants in the water column were taken into account, the grazing estimate was close to that expected. It was also confirmed that the animals fed at a higher rate on larger particles in sea water. In experiments to determine the effect of heavy metals on the feeding of copepods, it was found that 10 /g copper/litre significantly reduced the copepods' filtering rates in natural and synthetic media. The growth and size distribution of plants in natural sea water grown in the presence of 10 /g copper/litre was also affected. In the presence of a chelating substance, the copper became relatively innocuous even at concentrations higher than 10 g/litre this lends weight to the hypothesis that only ionic copper affects the feeding of copepods and that when it becomes bound to large organic molecules, it becomes harmless. The copepods also recovered from previous exposure to/to copper when they wore removed to fresh sea water, Estimates were made of the likely effect of pollution by copper on the production in a sea Lochs grazing by copepods was estimated to fall by as much as 70% in the presence of 10 /ug copper/ litre. The sources of discrepancies in making these' estimates is' a discussed. 3 g mercury/litre in sea water affected the feeding of copepods, but some difficulty was experienced in measuring the effect on feeding in natural phytoplankton as the mercury seemed to enhance the growth of some phytoplankters in sea water.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.455807  DOI: Not available
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