Incorporating Lakes within the River Discontinuum: Longitudinal changes in Ecological Characteristics in Stream–lake Networks

Researchers: Nick Jones

Project Description: Streams are typically thought of as long channels of continuously moving water that drain watersheds, yet for many parts of the world e.g., Canada, United States, Sweden, Finland, Norway, Russia, Argentina, streams and lakes are intimately connected. For example, the Canadian Shield occupies an area of 4.6 million sq km (1.8 million sq mi) or nearly half the land area of Canada and is densely populated with lakes and interconnecting streams.  The mainstem of the Petawawa River, Ontario, has 26 large lakes on its 200 km length. The Churchill River, Manitoba and Saskatchewan, has 52 large lakes on its 1300 km length and many unnamed lakes representing wider reaches of the river. In addition, ephemeral beaver ponds within watersheds are often not mapped. Streams flow through small and shallow thaw lakes that are abundant in lowland ice-rich permafrost in many parts of Alaska, Canada, and Russia.

Abstract: Lakes and rivers are intimately connected in an alternating series of lentic and lotic reaches in many regions. The study of lakes and their outlets in hierarchical and branching river networks has not gained the attention of stream ecologists, and little effort has been focused on synthesizing the ecology of lake–stream interactions within a drainage network. Rapid and predictable changes in the ecological characteristics of streams occur at the interface with lakes. The influence that a lake might have on a stream is dependent on its position within the stream, stream type and size, lake size and shape, and the inlet and outlet positions. Little is known about the influences of multiple lakes within stream–lake networks and how these influences are determined by network shape and pattern. Fruitful collaborations and novel insights will come from the combined efforts of limnologists, stream ecologists, and landscape ecologists. Geographic information systems and network analyses will play an important role in summarizing aquatic landscape characteristics and creating a predictive science of aquatic networks. Lakes need to be more explicitly incorporated into ecological concepts in stream ecology, and reciprocally, streams need to be incorporated into ecological concepts involving lakes for the successful management and conservation of our aquatic resources.

Jones, N.E. Incorporating Lakes within the River Discontinuum: Longitudinal Changes in Ecological Characteristics in Stream-Lake Networks. Canadian Journal of Fisheries and Aquatic Sciences 67: 1350-1362.