Organic
matter retention by macrophyte beds in 2 southeastern USA,
low-gradient, headwater streams
PETER
KOETSIER Department of Biology, Boise State University, 1910 University Dr., Boise,
Idaho 83725 USA
J VAUN McARTHUR Savannah River Ecology Laboratory, University of Georgia, Drawer E, Aiken,
South Carolina 29802 USA
Abstract.We examined particulate organic matter (POM) storage and retention in
aquatic macrophyte beds (Sparganium americanum Nutt.) from 2,
first-order, blackwater tributaries of Tinker Creek,
South Carolina, USA.Measurements were made during the autumn (high litter input) and summer
(low litter input), in 100-m study readies, 1 with low macrophyte density (T-1)
and 1 with high
macrophyte density (T-2).Three
experiments assessed: 1) POM retention by individual plant beds,
2) short-term retention of leaf analogs in plant beds
and by other retention structures, and 3) benthic
and transported POM at the reach scale.Upon completion, all above ground macrophyte biomass
was removed and the experiments were repeated.At the scale of I bed, low plant density effectively
trapped and stored POM in summer and autumn.High-density beds stored POM in the summer
but during autumn POM output exceeded input.At the reach scale, both tributaries effectively retained coarse POM in
summer, but only high-density beds did so in autumn.Likewise, only high-
density beds trapped and retained fine POM.Following plant removal, both coarse and fine POM
were transported with minimal retention.When plants were present, beds played a major role in
leaf analog retention and increased the retentive capabilities of other channel
structures (debris dams,
overhanging vegetation).When beds
were removed, most analogs were retained by debris dams or
settled to the substrate.Macrophyte beds play a major role in POM retention and short-term storage
in low-gradient blackwater streams at several spatial scales and are linked to
retention by other
channel structures.The importance of macrophyte beds varies depending on bed density, total
surface
coverage, and timing of leaf fall.
Koetsier, P., and J. V McArthur.
2000. Organic matter retention by macrophyte beds in 2 southeastern USA,
low-gradient, headwater streams. Journal of the North American Benthological
Society 19:633-647.
