FLANDERS MARINE INSTITUTE
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.
 A Model of Annual Plankton Cycles
A model is presented that exhibits a spring phytoplankton bloom as one feature of a steadily repeating annual cycle of plankton populations. Populations respond to seasonal changes in light (which are gradual) and in mixed layer depth (which may be rapid). The occurrence of a bloom does not require a shallowing of the mixed layer; it does require a low rate of primary production in winter. The lack of phytoplankton blooms in the subarctic Pacific can be explained in terms of this model.
Analysis of a simplified version of the model shows that a bloom is a deviation from quasi-equilibrium behavior and explains why this will occur when winter production rates are low.
 A Simple Plankton Model
Data on plankton ecosystems in large enclosures are used as a basis for consideration of the role of deterministic and random processes in these systems. Using a simple model, it is proposed that the exclusion of random variations in predators can lead to greater extremes in the phytoplankton/herbivore populations in enclosures compared with those outside. These results depend on the relative rates of internal and exogenous changes, and comparisons are made with results for a forest ecosystem.
 Fish Yields in Relation to Water Quality and Plankton Production in Managed and Unmanaged Fresh Water Ponds
Managed and unmanaged (unmanaged) extensive culture fisheries systems in small village ponds in the district of Kurukshetra, Haryana, India were explored and analyzed focusing on the relationship amongst water quality, production of fish food organisms, fish yields and management actions. In unmanaged ponds, fish growth/yield and dissolved oxygen were low and ammonia, chlorides, calcium, total hardness, magnesium, phosphates and biochemical oxygen demand were higher when compared against managed ponds. The differences are likely due to higher organic load in the unmanaged ponds arising from domestic sewage and cattle entry from non-point sources. Variations observed in the phytoplankton population for the unmanaged and managed ponds were insignificant, however, zooplankton were high in unmanaged ponds. The NPP was higher in the unmanaged ponds in contrast to managed ponds. From the finding it seems that Fish production does not tends to depend significantly on the extent of primary production. Significant direct relationship between fish production and primary productivity could not be determined in this study. However, multivariable relationships were detected through multivariate statistical analysis. Such relationships are not straightforward as a variety of factors including ammonia production, organic loading and the quantity and quality of fertilizers play important roles in influencing such relations.
 Evaluating the Physico-chemical Characteristics and Plankton Diversity of Nwaniba River, South-South Nigeria
The physicochemical characteristics and plankton diversity of Nwaniba River, Uruan, Akwa Ibom, Nigeria were studied between April and September 2013. Surface water samples were collected for physicochemical parameter and plankton analysis according to standard methods. The results of the physicochemical parameters were within recommended limits of the National Environmental Standards and Regulations Enforcement Agencies (NESREA) for aquatic life. Twenty plankton species belonging to five taxa were encountered in the following order of dominance; Bacillariophyceae (69.23%) > Chlorophyceae (18.38%) > Cyanophyceae (11.97%) > Dinophyceae (0.85%) > Rotifera (0.43%). The most abundant phytoplankton was Coscinodiscus radiates, accounting for 47.7%, the least were Peridinium bipes, Pediastrum duplex, Rivularia spp, Gonatozon monalaenum, Navicular peroltelti, Tabelaria spp, Epithemia zebra and accounting for less than 1% respectively, while Lacane bulla was the only species for zooplankton. High Diversity indices values were recorded for Chlorophyceae =1.36 while the least was Cyanophyceae = 1-21. The presence of certain plankton-pollution tolerant species such as Anabaena circularis, Navicula peroltelti, and Peridinium bipes suggests a low level of organic pollution in the river.
 Cassie, R.M., 1963. Microdistribution of plankton. Oceanography and marine biology: an annual review.
 Evans, G.T. and Parslow, J.S., 1985. A model of annual plankton cycles. Biological oceanography, 3(3), pp.327-347.
 Steele, J.H. and Henderson, E.W., 1981. A simple plankton model. The American Naturalist, 117(5), pp.676-691.
 Singh, G., Bhatnagar, A., Alok, K. and Ajay, S.A., 2016. Fish Yields in Relation to Water Quality and Plankton Production in Managed and Unmanaged Fresh Water Ponds. Journal of Experimental Agriculture International, pp.1-10.
 Esenowo, I.K., Ugwumba, A.A.A. and Akpan, A.U., 2017. Evaluating the physico-chemical characteristics and plankton diversity of Nwaniba River, South-South Nigeria. Asian Journal of Environment & Ecology, pp.1-8.