Understanding Declining Offshore Productivity in the Great Lakes

Session: 23. - The IJC's Science Advisory Board Review of Current Priorities and Projects

John Bratton, Limnotech, [email protected]
Jennifer Daley, LimnoTech, University of Michigan, [email protected]
Doug Bradley, Limnotech, [email protected]
Robert Hecky, Editor, Journal of Great Lakes Research, [email protected]
Joseph DePinto, retired, [email protected]
Mark Burrows, International Joint Commission, [email protected]

Abstract

A topical review of information on the relationship between nutrient levels and upper food web productivity was conducted in cooperation with a work group of the International Joint Commission Science Advisory Board. Components of the study included a global literature review, updating of water quality and fish biomass datasets from approximately 2010 through 2015 for each lake, review of ecological food web models, and development of a synthesis of findings, gaps, and policy recommendations. Initial review of new data generally indicated persistence of patterns observed in a previous synthesis by Bunnell et al. (2014), which showed major changes associated with dreissenid mussel invasion, followed by a period of reduced but relatively stable productivity, at least in the lower food web. Patterns across the Great Lakes for piscivorous fish and prey fish were more complex, but generally showed continued reduced biomass relative to earlier periods with some exceptions. Policy recommendations regarding fishery impacts of nutrient management under Annex 4 of the Great Lakes Water Quality Agreement are in development, and may benefit from simulations using whole ecosystem models such as Ecopath with Ecosim or Atlantis, which have recently been applied by researchers to some of the lakes. 

1. Keyword
fish

2. Keyword
ecosystems

3. Keyword
productivity

4. Additional Keyword
nutrients

5. Additional Keyword
mussels

6. Additional Keyword
management