Analysis of seasonal succession of attached algae in a mountain stream, the North Alouette River, British Columbia

Seasonal succession of attached algae in the North Alouette River over 1 year is described and analyzed in relation to physicochemical characteristics. An attempt is made to consider quantitatively both diatom and nondiatom species using a multivariate method, principal coordinates analysis (P-Co-A).Stream water was slightly acidic and nutrient poor, the order of dominance in anions being SO42− > SiO2 > Cl− > NO3− > PO43− and metals plus ammonium [Formula: see text]. P-Co-A of seasonal succession revealed a cyclic pattern with sequences of gradual and abrupt changes in species composition. Flow, temperature, Cl−, and SO42−, which fluctuated abruptly, were significantly correlated with most of the seasonal change in species summarized by P-Co-A. A smaller amount of the variation, which was more smoothly patterned, correlated with fluxes in dissolved cations. Methods of enumeration and analysis used, although not sensitive to differences in absolute abundance of algal populations, were useful in describing successional patterns in species composition, where both macrophyte and microphyte forms were encountered.Major species tended to wax and wane seasonally, but exhibited long periods of overlap. Such a pattern supports one idea from the "river continuum concept," that generally species are merely shifting along temporal and spatial axes, while the total exclusion or absence of a population is indeed rare. It is suggested that this form of community structure differs from that typically understood for plant succession.