Community dynamics of Desmids (Chlorophyta) in peatland pools of the North Harbour Peninsula : the significance of habitat variation

Howell, E. Todd (1983) Community dynamics of Desmids (Chlorophyta) in peatland pools of the North Harbour Peninsula : the significance of habitat variation. Masters thesis, Memorial University of Newfoundland.

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Abstract

Three primary gradients of pool habit variation have been identified for twelve pools within adjacent slope fen and basin bog environments on the North Harbour Peninsula, Newfoundland. Those gradients correspond to : a minerptrophic gradient 2) a permanency gradient and 3) a surface water flow gradient. The dynamics of desmid communities associated with the Sphagnum fringes of these pools have been examined and are strongly modified by the gradients. -- Fifty-eight of the desmid species observed were distributed with the minerotrophic gradient and range from those endemic to minerogthrophic pools (43%) to those endemic to ombrotrophic pools {16%) Pool dominants were heterogeneously distributed and comprised associations with few shared species at extremes of the gradient. The determining factor in relation to minerbtrophy appears to be changes in water chemistry. Positive correlations were found with pH, Ca, Mg, Fe, N03- and silicate and negative correlations with tannins + lignins C0D and P043- (P >-.01) . -- Thirty-eight of the desmid species were restricted to permanent pools. The less-species-rich temporary pools shared most all dominant species with permanent pools but lacked many of the permanent pool dominants. Dominant species of temporary pools showed a greater unevenness of abundance than in permanent pools. The determining factor with respect to pool permanency appears to be differential desiccation tolerance by vegetative cells in desmid species. -- Pool water flow lowered total desmid population densities and induced a high degree of temporal variability, apparently by washing away portions of the loosely adhering desmid growths. -- No systematic temporal variation, other than seasonal total population changes, was observed in the desmid communities over the study period. Pools not subject to water flow or temporary drying showed persistance in the importance of dominant species groups. The high degree of temporal consistency in the desmid communities was in contrast to a high degree of temporal variation in pool water quality.

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