POST FLOOD CHANGES IN AQUATIC MACROPHYTE BEDS OF LOWER
REACHES OF POOL 19, MISSISSIPPI RIVER

Richard V. Anderson, Dept. of Biological Sciences,
Western Illinois University, Macomb, IL 61455, David M.
Day, Illinois Department of Natural Resources,
Springfield, IL 62701, Jeff Arnold, 521 Sunset Ct.,
Abington, IL.

As sediments accumulated in Pool 19 following
completion of Lock and Dam 19 in 1913 water depths
decreased in much of the channel border habitat.  By
the late 1960's some areas were sufficiently shallow so
that aquatic macrophytes began to develop.  Rate of
development increased rapidly until the late 1980s when
population of submerged and emergent aquatic
macrophytes crashed.  During this period a drought and
infestation of the Lotus Borer, Ostrinia, occurred.  In
the early 1990's the aquatic macrophyte beds again
began to expand until the extreme flood in 1993.  This
flood resulted in the elimination of over 95% of the
aquatic macrophyte beds from Pool 19 and these
conditions persisted through 1994.  Some growth of
submerged plants and Lotus began to occur in many areas
in late summer of 1995.  By the summer of 1996 aquatic
macrophytes again occurred in most of the areas
occupied by the plants prior to 1993.  However, species
composition, plant density and distribution was similar
to that found in the early to mid 1980's.  It is
apparent that the plant beds are recovering at a
highter rate than during their initial colonization. 
While the effect of an extreme flood resets conditions
in the plant beds, sediment scour was not sufficient to
reduce the extent of the beds for a prolonged period of
time.






Richard V. Anderson
Dept. Biological Sciences
1 University Circle
Western Illinois University
Macomb, IL 61455

Phone: 309-298-155
FAX: 309-298-2270
email: randerso@ccmail.wiu.edu


Poster/yes