Multiple Stable Configurations in Ordination of Phytoplankton Community Change Rates

Relationships between a phytoplankton community and its environment were found by multivariate analysis of not species occurrences but rather the first difference of species weekly occurrences. Principal component analysis of 55 sample first differences in a 103-dimensioned species first-difference space was performed. Successive sample points described a community trajectory in first difference ordination space. This trajectory oscillated in several discrete ordination regions. The discrete regions of oscillation were first defined subjectively but between-region discontinuities were verified by reconstruction according to simple objective criteria. The regions of oscillation are taken to represent centers of community structure in multivariate species first difference space. Similar patterns of oscillation found in an ordination in environmental state space were likewise interpreted as centers of multivariate environmental structure. The objectively defined discontinuities on the environmental ordination show close correspondence to those on the community ordination. There are structural forces intrinsic to the community, and the community composition moves from one center of community structure to another only by the intervention of intermittent shift in environmental structure. The shifts in the environment were indicated by the principal component analysis of estimates of the state of nine environmental parameters.