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  Ecovision > State of Lake Superior: Health, Integrity & Management > Summaries
 


Trophic linkages in the Lake Superior food web: A synthesis of empirical and modelling studies 1970-2003

Timothy B. Johnson

Aquatic Research and Development Section, Ontario Ministry of Natural Resources 320 Milo Road, Wheatley, Ontario, N0P 2P0 Canada

*Corresponding author: tim.johnson@mnr.gov.on.ca

Summary

         Ecological studies describing the food web of Lake Superior are reviewed and synthesised from 1970 through 2003. Basic information on lower trophic levels (phytoplankton, zooplankton, and benthos) is much weaker than knowledge of economically important fishes. Extensive spatial and temporal (multi-year and seasonal) databases exist for diets and growth of dominant prey and predatory fishes. Bioenergetic analyses commenced in the mid-1990s to link predator demand with prey supply from invertebrates (zooplankton and benthos) to small (forage) fishes to piscivores. All studies concluded data were collected with inadequate spatial (vertical and horizontal) and temporal intensity to fully address questions of system carrying capacity. Stable isotopes and contaminants have proven useful for identifying pathways of material transfer from atmospheric sources, tributaries and coastal wetlands through to offshore feeding relationships between predators and prey. Recent surveys have extended further offshore, providing valuable information on the biota, their behaviour and interrelationships. Whole lake hydroacoustic surveys and food web models have recently been developed on Lake Superior, providing managers and scientists alike with information needed to understand the structure and productive potential of this Great Lake as it responds to anthropogenic stresses associated with climate change, invasion by non-indigenous species, and development of its watershed.

Keywords: stable isotope, bioenergetics, model, diet, growth, contaminant

 

 

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