Environmental Laboratory, US Army Engineer Waterways Experiment Station,
Limitations and Concerns
Carpenter and Adams (1977) have reviewed the environmental impacts of
Macrophyte removal constitutes habitat removal for organisms such
as snails, insects, and young fish, and the abundances of these animals can be
The evidence of a negative impact on fish is conflicting.
(1980) found that harvesting removed about 85 kg
of fish per hectare (76 lb per
and Mikol (1984) found that fish populations of
At Saratoga Lake (Mikol 1984) and
lakes remained stable during harvesting.
New York, small sunfish, perch, and
bullheads were the dominant fish removed by the harvester.
another possible benefit of harvesting.
Removal of sunfish and perch also
means removal of the organisms that can have a significant role in
selective predation on the zooplankton species that graze algae.
a significant removal of these small fish may mean lake improvement with
regard to algae as well, since herbivorous zooplankton may have increased
population density when fish predation on them is lowered.
Some investigators have been concerned about the initiation of algal
blooms following extensive plant removal.
This has been found in some lakes
and reservoirs (Neel, Peterson, and Smith 1973; Nichols 1973; Anderson 1984;
but not in others (Wile,
and Beggs 1979).
The causes of this phenomenon are very poorly understood.
(1986) found much higher phosphorus concentrations in a bay after harvesting,
although there is no evidence that this caused the algal bloom.
been many suggestions of an antagonistic effect between algae and macrophytes
et al. 1983) so that removal of macrophytes "releases" algae
from these restraints, and blooms occur.
The inhibition postulated by these
investigators could include shading, release of an inhibitory substance, or
removal of cover for algae-grazing zooplankton species.
Normally this problem
will not occur on large reservoirs where complete vegetation removal is
neither desirable nor feasible, and could therefore be an environmental
problem only in some coves or bays.
Another more significant impact of