Seasonal changes in secondary production, faunal similarity and biological accomodation, related to stability among the Gastrotricha of two semi-enclosed Scottish beaches
Hummon, W.D. (1976). Seasonal changes in secondary production, faunal similarity and biological accomodation, related to stability among the Gastrotricha of two semi-enclosed Scottish beaches, in: Persoone, G. et al. (Ed.) Proceedings of the 10th European Symposium on Marine Biology, Ostend, Belgium, Sept. 17-23, 1975: 2. Population dynamics of marine organisms in relation with nutrient cycling in shallow waters. pp. 309-336 In: Persoone, G.; Jaspers, E. (Ed.) (1976). Proceedings of the 10th European Symposium on Marine Biology, Ostend, Belgium, Sept. 17-23, 1975: 2. Population dynamics of marine organisms in relation with nutrient cycling in shallow waters. European Marine Biology Symposia, 10(2). IZWO/Universa Press: Wetteren. ISBN 90-6281-002-0. 712 pp., more In: European Marine Biology Symposia., more |
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| Abstract | Collections were made at bimonthly intervals over the past year from low to high tide transects in two semi-enclosed scottish beaches -one at Irvine Bay in the Firth of Clyde, Ayrshire, and the other at Firemore Bay, in Loch Ewe, Wester Ross. Both beaches are comprised of well-sorted, fine to medium sands, extending 200-300 m from low to high spring tide levels, both are occupied by variants of the Tellina tenuis macrobenthos community, and both function as flatfish nursery grounds. In the former beach, representing a habitat polluted primarily by domestic sewage, Gastrotricha rank second in numerical dominance among Micrometazoa, exceeded only by the Nematoda; in the latter beach, representing an unpolluted habitat, Gastrotricha rank fourth in numerical dominance among Micrometazoa, behind Nematoda, Harpacticoida and Turbellaria. Observed H' species diversity was 0.31-0.63 bits for 9-14 species in Irvine Bay collections (J' evenness. 0.07-0.15), compared to 2.69-3.56 bits for 25-32 species in Firemore Bay collections (J' evenness, 0.51-0.67). Mean similarity between collections, based on shared species diversity, was 47.7 (SD, 10.8) % for Irvine Bay and 61.4 (SD, 7.5) % for Firemore Bay. Geometric mean adjusted numbers of gastrotrichs per 10 sq. cm ( = x 10³/sq. cm) were 98-567 (highest station values, 1,244-6,260) for Irvine Bay collections and 137-213 (highest station values, 503-783) for Firemore Bay collections. Geometric mean adjusted gastrotrich biomass in pg dry weight per 10 sq. cm surface ( = mg/m²) was estimated to be 48-274 (highest station values, 620-3,127) for Irvine Bay collections and 63-95 (highest station values, 279-384) for Firemore Bay collections. Weighted mean numbers of additional gastrotrich species co-occurring in the same sample per individual, one of two measures of biological accommodation among Gastrotricha, were 0.83- 1.68 (SD values, 0.59-0.83) for Irvine Bay collections and 1.78-4.61 (SD values. 1.63-2.29) for Firemore Bay collections. Covariances among all gastrotrichs and among intra-familial species of each family were slightly negative in all collections from Irvine Bay, except December, when a slight positive value was observed among members of the entire subcommunity. By contrast, covariances among all gastrotrichs of Firemore Bay oscillated from positive in August to significantly negative in December to significantly positive in June. Covariances among intra-familial species were negative for all families save the Chaetonotidae, in which a comparable oscillatory pattern to that of the entire subcommunity was observed. Temporal stability, as measured in each of two ways, showed lower values for the gastrotrich subcommunity from the Irvine Bay transect than from that of the Firemore Bay transect. Covariance oscillations are assessed in light of these findings. Aside from overall numbers and biomass estimates, little overlap was observed between the gastrotrich fauna of the two beaches, or between values derived from these fauna. Yet, among collections from each beach over an annual cycle, the data were relatively consistent. It is suggested that because of their important position in the decomposer-based foodweb, as bacteriophagous feeders, and their usual presence in and occasional numerical significance among micrometazoa of intertidal beaches, the Gastrotricha are worthy of increased consideration in bionomic analyses of this habitat. |
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