SPATIAL AND TEMPORAL DIFFERENCES IN TRANSPORT OF MACRO AND MICROZOOPLANKTON IN 
THE SCHOOLCRAFT LAKE-RIVER SYSTEM.

Debbie L. Guelda and Erich Westrich
Department of Biology, Bemidji State University.  Bemidji, MN  56601.

During the summer and fall of 2002, macro and microzooplankton were collected at 
both river and lake sites along the Schoolcraft River, a tributary of the 
Mississippi River in northern Minnesota.  Sites included the inlet and outlet of 
lakes Plantagenet, Marquette, Irvine and Bemidji.  Species diversity was much 
higher at all sites during the fall sampling period with calanoid and cyclopoid 
copepods, Daphnia retrocurva and the rotifer Keratella cochlearis being the 
dominant species present.  Total zooplankton density was highest (31.6 ind L-1) 
in the spring when diversity was lowest.  Spring communities were dominated by 
Bosmina and K. cochlearis.  At all sites and times zooplankton density increased 
between lake input (11.5 ind L-1) and output (27 ind L-1) suggesting that in-
lake production was high enough to offset predation.  Zooplankton densities 
decreased during riverine transport (net loss of 19 ind L-1) suggesting that 
production was low due to decreased food availability, greater predation or 
physical stress.  The Schoolcraft River serves as a source of zooplankton to the 
Mississippi River (16.3 ind L-1), although species diversity of exports remains 
low.

Keywords:  Zooplankton, River, Lake, Budget, Transport