Abstract

Densities of 5 taxa along with 7 environmental variables were measured monthly with 4 replicates at each of 3 stations over a period of 5 years. The 720 observations of density for each taxon were analyzed by General Linear Models with density as the dependent variable. Differences among stations, years, seasons and their interactions are all significant. When treated as covariates environmental variables contributed little to explaining the observed variability in densities. However, the observed densities of the taxa are highly correlated and when a single taxon is treated as a covariate most of the variability in the density of a related taxon is explained. There are no significant differences among replicates (taken within a square meter) or their interactions. Consequently, the biotic or abiotic factor(s), although unknown, responsible for the simultaneous density variation of the taxa operate on a relatively small spatial scale. Based on these observations and previous studies, we propose a model wherein individual foraminifers are spatially distributed as a heterogeneous continuum forming patches with different densities that are only meters apart; reproduction is asynchronous causing pulsating patches that vary in space and time. Thus, we would expect significant differences among stations, years, seasons and their interaction. At the same time, no long-term increase or decrease in density for any of the taxa is observed. Evidently, long-term stability is achieved through considerable short-term variability in space and time. Although observations at a single station are not indicative of a larger area at any particular time, the concept of pulsating patches indicates that observations at a station will in the long-term give an assessment of a larger area.

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