JOURNAL OF PLANKTON RESEARCH | VOLUME 11 | NUMBER 2 | PAGES 173-184 | 1989
© Oxford University Press
research-article |
Zooplankton patchiness in enclosed and unenclosed areas of water
Freshwater Biological Association, Windermere Laboratory Ambleside, Cumbria, UK
Received on June 1, 1987; accepted on October 23, 1988 Indices of patchiness based on the concept of mean crowding are used to compare the dispersion patterns of crustacean zooplankton in an area of open water and in two experimental endosures of different size. In all situations the distribution of the animals was primarily determined by their behavioural response to water movements. In the copepod Cyclops strenuus abyssorum this behaviour changed systematically as the animals grew and became capable of independent movement. Statistical tests showed that the lowest levels of patchiness were recorded in the open water and the highest in the smaller enclosure. These results can be explained by the animals' tendency to accumulate in areas of downwelling water. In the open water the animals can drift horizontally for hundreds of metres before encountering a downwelling. In the small enclosure the open water is soon traversed and the animals are forced to respond to a sudden vertical displacement. The results are discussed in relation to the general problems of experimental design and the specific problems of scaling in a fluid environment.