Field Sampling Methods

GLNPO's R/V Lake Guardian conducts two annual field surveys across all the Great Lakes. The Spring Survey collects samples when the lakes are isothermal, with low biological activity. The Summer Survey collects samples when the lakes are at peak biological activity.

Sampling Site Locations for GLNPO's Spring and Summer Annual Field Surveys on the Great Lakes

Aboard the R/V Lake Guardian, GLNPO implements two sampling methods for zooplankton collection.Collecting a Zooplankton Net Tow from R/V Lake Guardian

1. 20 meter net tows with a 63 micrometer net to collect species living in the surface waters
2. 100 meter (or 2 meters off the lake bottom) net tows with a 153 micrometer net to collect the full profile of zooplankton species, including those that migrate vertically, in the lake

Once collected, the zooplankton samples are preserved in formalin and analyzed by trained taxonomists to determine the zooplankton biomass and species density across each Great Lake.