Probability surveys as an approach for assessing zooplankton community and biomass trends in Lake Superior

Session: 32. - Long-Term Monitoring: Achievements, Challenges, and Solutions

Matthew Pawlowski, ORISE, [email protected]
Michael Sierszen, U.S. EPA, [email protected]
Peder Yurista, U.S. Environmental Protection Agency, [email protected]
Jack Kelly, US EPA Mid-Continent Ecology Division, [email protected]
Elizabeth Hinchey Malloy, U.S. EPA GLNPO, [email protected]
Jill Scharold, US EPA, [email protected]

Abstract

Detecting persistent changes in zooplankton biomass and community composition in large lakes can be challenging because these parameters vary by location, depth, and time of year. Under the Cooperative Science and Monitoring Initiative (CSMI), intensive, whole-lake surveys of Lake Superior were completed during late summer in 2006, 2011, and 2016 to assess stability in the lake’s lower foodweb. These surveys were designed using a random, depth-stratified probability approach to select spatially balanced sampling locations and to allow for survey results to be summarized by depth strata. We present estimates of average zooplankton density and biomass by depth strata from these surveys to identify potential trends. Results suggest that zooplankton community structure and biomass in Lake Superior have been stable within deeper depth strata since 2006 which is consistent with findings from GLNPO’s annual offshore summer surveys of Lake Superior. However, results also suggest that calanoid and cladoceran biomass have increased in nearshore areas since 2006, which is a change that that the annual surveys would not have captured. This monitoring approach provides foodweb data that may otherwise be unavailable and can facilitate long-term comparisons of foodweb structure by reducing the bias that results from sampling individual regions of the lake.

1. Keyword
zooplankton

2. Keyword
Lake Superior

3. Keyword
food chains

4. Additional Keyword
CSMI

5. Additional Keyword
Monitoring methods