Factors Influencing the Distribution of Phytoplankton in 97 Headwater Lakes in Insular Newfoundland

Abstract

Phytoplankton samples collected from 97 headwater lakes throughout insular Newfoundland were analyzed and used as a basis for a statistical evaluation of the environmental factors influencing species distributions. A selected subset of 77 taxa were clustered using a complete-linkage cluster analysis. The final 12 clusters represent the associations of species found occurring together in insular Newfoundland. Physical, chemical, and morphometric data collected with the phytoplankton served to characterize the environment. Factor analysis simplified the original variables, many of which were highly correlated and uninterpretable, into seven derived environmental factors: dystrophy, hardness, salinity, lake size, season, watershed influence, and orthophosphate enrichment. The resulting orthogonally rotated (VARIMAX) scores comprising these seven factors were correlated with species abundances. Spearman correlations showed several relationships between species distributions and the seven derived environmental factors. Although the analysis identified a subset of naturally acidic, dystrophic lakes, it failed to reveal any evidence of anthropogenic acidification in the lakes studied. For the most part, the members from each of the cluster groups demonstrated similar relationships with the derived environmental factors. The evidence suggests that the cluster groups may represent species associations; groups of species that co-occur because of their common requirements for specific environmental conditions. Phytoplankton autecological findings resulting from this study of insular Newfoundland lakes correspond well with conclusions derived independently from a comparable study of 95 headwater lakes in Labrador.