Journal of the Marine Biological Association of India

Volume 14 Issue 1

Assessing similarity between samples of plankton.


The study of the distributions of species of plankton organisms relative to each other within a confined sea area is emerging as an important and difficult problem. Much interest is attached to the comparison of pairs of entire samples rather than comparing the data from pairs of species. There is a considerable advantage in reducing the complex data, frequently consisting of counts of individuals of all species occurring in each sample, to a form in which they can be examined pictorially. This would then allow groups of similar or dissimilar samples to be more readily related spatially or temporally to each other.

Several data treatments which have been reported to do this have been examined and compared in this investigation. Samples of hypo plankton were taken in Loch Etive, Argyll, Scotland and the numbers of individuals of different species counted. The data were then analysed by several methods and the results presented in the form of trellis diagrams, a relatively old and attractive form of presentation. The different analyses produced slightly different results but they do present the investigator with several methods of treating complex data. The specific method selected depends on what information is required from the samples and, to some degree, on whether further and more detailed statistical tests are going to be made. These forms of analyses can indicate possible groupings of samples which might be selected as starting points in a larger multiple correlation analyses.

Other possible methods of treating the data, although not used in this paper, are mentioned and the authorities quoted because the literature on this subject is scattered and could usefully be listed.

Date : 30-06-1972