Understanding how physical and biological factors shape community structure is a topic of longstanding interest to ecologists.  Previous research has shown that lake size, connectivity, and primary productivity all influence zooplankton community structure, but few studies have compared all three.  To see which of these factors best predicted zooplankton effective richness, we sampled fifteen lakes in the Boundary Waters Canoe Area Wilderness (BWCAW) over a one-week period in September 2007 as part of a field ecology course.  Zooplankton were sampled using vertical net tows, lake productivity was estimated with Secchi depth, and lake size and connectivity were determined using maps and a Minnesota DNR database.  One hundred zooplankton individuals were identified to species for each of the fifteen lakes and zooplankton effective richness (e^H) was calculated.  Linear regression was used to determine relationships for factor and a principle components analysis was used to compare factors. 

Results/Conclusions

The strongest relationship was seen between effective richness and primary productivity (p=0.002, r²=0.50), followed by lake size (p=0.02, r²=0.30).  Connectivity was not a significant predictor (p=0.10, r²=0.13).   The data showed that lakes having greater productivity had the lowest effective richness, whereas lakes having intermediate productivity had the highest.  By contrast, lakes size was positively correlated with zooplankton richness.  These data corroborate other studies that have shown a strong link between lake trophic status and zooplankton richness.  This study was unique in that it examined relatively pristine meso-oligotrophic lakes that had little human impact.