|Microdistribution of plankton|
Cassie, R.M. (1963). Microdistribution of plankton. Oceanogr. Mar. Biol. Ann. Rev. 1: 223-252
In: Oceanography and Marine Biology: An Annual Review. Aberdeen University Press/Allen & Unwin: London. ISSN 0078-3218, more
The term 'microdistribution' is to some extent self-explanatory and itis undesirable to define too rigidly the size of the physical dimensions at which distribution is considered to become 'micro' since this would restrict discussion of some of the more significant implications of the subject. The concept of microdistribution, though sometimes studied for its own sake, first arose in connection with the estimation of sampling errors in large-scale geographical investigations. Since it is hoped that every plankton sample is representative of the population of a very much larger volume of water, the range of variation in samples taken within this volume is of importance in evaluating the differences between more widely spaced samples. Thus, the study of microdistribution will involve the use of statistical techniques and will be concerned rather more with quantitative than qualitative changes in the plankton. The question of error in sampling estimation of plankton probably first arose in the latter part of the nineteenth century in the works of Hensen and Haeckel which are reviewed by Hardy (1935). Hensen (1890) believed that the distribution of oceanic plankton was very 'even' in the ocean and hence that errors of estimation were low, whereas Haeckel (1890) claimed the very opposite and considered that estimation was impossible. Thus, the first matter to be discussed in this review concerns the appropriate statistical criteria to be used in an objective assessment of even and uneven distribution. Once it is established that unevenness is the general rule, the factors responsible for this condition can be discussed. At the same time, it is possible, not only to find means of improving sampling and estimating techniques, but also to introduce a newer, but equally important aspect of microdistribution, the study of plankton behaviour . Since many of the appropriate mathematical and statistical concepts have been developed in geographical investigations, even outside the field of plankton altogether, it will be desirable at times to discuss work which would, in the strictest sense, be outside the scope of the review. On the other hand, two topics of some relevance will be considered only briefly, since they seem to be of such magnitude as to warrant separate review treatment. The first of these is the phenomenon of vertical distribution and migration of plankton, which is controlled by relatively gross gradients of light, pressure, etc., even though the spatial interval involved may be relatively small. Here attention will be concentrated on statistical concepts, and on factors which may modify in detail the overall pattern. The second is the behaviour of aquatic invertebrates as studied under laboratory conditions. There is little doubt that much experimental work in this field has direct relevance to microdistribution, although it has seldom been carried out with this object in mind.