The spatial pattern of Polychaeta in soft sediments and the influence of food supply on their patchiness
Volckaert, F.A.M.J. (1983). The spatial pattern of Polychaeta in soft sediments and the influence of food supply on their patchiness. MSc Thesis. Dalhousie University: Halifax. 95 pp.
The Manna model of Wangersky & Wangersky (1981) suggests for a benthic community of detritivores that: 1) High levels of food input from the overlying watercolumn result in an infaunal spatial distribution consisting of numerous small patches. 2) Low levels of food input are accompanied by more patches of single animals and larger sized patches. To test the hypothesis, micro-scale patchiness (i.e. proportional to the sphere of influence) of polychaetes was investigated at several subtidal sites which differed in surface productivity and presumably food input to the benthos. Seven box core samples (each 0.25 m²) from three sites off Nova Scotia (Canada) were completely subsampled as 25 contiguous 0.01 m² cores and analyzed for their polychaetous fauna. Dispersion chi-square and autocorrelation analysis were performed on adult herbivore and detritivore infaunal Polychaeta. The inshore fauna is more strongly clumped than the offshore fauna with patchiness at several scales smaller than 10 cm in diameter, equal to 10- 50 cm (30% of the species), and larger than 50 cm. Polychaetes in samples from offshore stations tend to be randomly dispersed. The results conform with the present understanding of infaunal spatial patterns. A correlation between the organic carbon flux and the degree of clumping existed at a low level of statistical significance. The complexity of benthic interactions hampers a detailed assessment of the nature of the observed patchiness in relation to the Manna model. Adequate testing of the model was restricted by an insufficiently large data base, the problem of separating the influence of the random input of food from other environmental variables and the theoretical nature of the Manna Model.
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