1. Sentinel Lakes 2008 Zooplankton Update

2. Field Sampling MPCA staff collected 363 zooplankton samples. All 24 lakes were sampled monthly from April/May thru October. At least two vertical tows were taken from each lake at deepest location. What worked well: Samples delivered to lab periodically throughout season, preserved and labeled well. Improvements for next year: Better system for ordering supplies, removable bottle labels.

3. Sample Processing April thru August samples completed. Data includes: densities, biomass, percent composition by number and weight, mean length, mean weight, and counts for each taxonomic group. What worked well: ZCOUNT so far……. Improvements for next year: new zooplankton counting system?? (we’re working on it).

4. Data Analysis (April-August only) Grouped lakes by eco-region and plotted monthly densities and biomass. In general, the western corn belt/ plains lakes had the highest densities and biomass, while the border lakes had the lowest. Some overlap between eco-regions.

5. Western Corn Belt-Plains Mean Zooplankton Densities and Biomass

6. North Central Hardwood Forest

7. Mean Zooplankton Densities and Biomass Northern Lakes and Forests

8. Mean Zooplankton Densities and Biomass Border Lakes

9. Potential Indices –Mean Annual Densities (#/L) Range 1.46-124.48 TP↑ Density↑ –Mean Annual Biomass (µg/L) Range 5.87-1169.26 TP↑ Biomass↑ –Total # Taxa Range 8-18 TP↑ Total #Taxa ↓ –Cladoceran Mean Length (mm) Range 0.40-1.27 TP↑ mean length↓ –Ratio Calanoids/Cladocerans Range 0.02-3.59 TP↑ Ratio↓

12. Individual Species and Assemblages 37 different taxa in 24 lakes 10 taxa were common in most lakes (ubiquitous species) Three species of calanoids and one daphnia species appeared to be present in the deeper oligotrophic or mesotrophic lakes only. Two calanoid species appeared to be present only in shallow eutrophic lakes. Planning to analyze data using PC-Ord