Restoration and Management of Lakes and Reservoirs - Hydro-Environmental Analysis: Freshwater Environments - page 476

green and blue-green algae and most diatoms. While it may be effective in the short term, there are
major negative impacts to nontarget organisms and an additional concern is the contamination of
sediments (Cooke et al. 2005). Holdren et al. (2001) reported that 58 years of copper sulfate treatment
of several Minnesota lakes led to the following:

• Depleted dissolved oxygen

• Increased internal nutrient cycline

• Occasional ish kills

• Accumulated copper in sediments

• Increased tolerance to copper by some nuisance algae

• Negative impacts on ish and zooplankton

This led Hanson and Stefan (1984) to conclude that a short-term control method had been traded
for the long-term degradation of lakes. Cooke et al. (2005) indicated that a search for a viable alter-
native algicide to copper with fewer negative effects has, to date, been unsuccessful.

17.4.9 f ood c HaIn M anIpuLatIon or b IoManIpuLatIon
The term biomanipulation was coined by Sharpio (1979, cited in Cooke et al. 2005) to represent
“a series of manipulations of the biota of lakes and their habitats to facilitate … reduction of algal
biomass, and in particular, of blue-greens.” Biomanipulation usually involves predator-prey rela-
tionships. An example would be altering the structure of the ish community. The irst example,
cited by Cooke et al. (2005), was the study by Caird (1945) where the introduction of largemouth
bass reduced phytoplankton biomass. An approach is to reduce the dominance of ish such as blue
gills and perch that feed on zooplankton, which, in turn, feed on algae, and replace them with bass,
pike, or walleye (Holdren et al. 2001). This reduces the pressure on the zooplankton community,
which then consumes greater quantities of algae. Cooke et al. (2005) summarize case histories of a
variety of biomanipulation projects.

17.4.10 r ouGH f ISH r eMoVaL
Rough ish include shad, carp, buffalo, carpsuckers, white perch, and other “undesirable” ish and
their removal can aid in reducing algal concentrations in two ways. First, these ish typically feed
on algae on the lake bottom, stirring up sediments and releasing nutrients into the water column.
Secondly, some of these ish, such as the gizzard shad, eat zooplankton. As with biomanipulation,
removing these ish may result in a larger population of zooplankton, which will consume greater
amounts of algae and provide increased food resources for juvenile, more “desirable” game ish
species.

17.4.11 H ypoLIMnetIc w ItHdrawaL
Hypolimnetic withdrawal refers to removing nutrient-rich and oxygen-depleted waters from the
hypolimnion of lakes and reservoirs. This also reduces the residence time of water in the hypo-
limnion, which can aid in reducing deoxygenation and internal nutrient loadings from sediments.
Cooke et al. (2005) evaluated reports of the use of hypolimnetic withdrawal in 21 lakes, 15 of which
were located in Europe and 2 in the United States (Lake Waramaug, CT, and Lake Ballinger, WA).
He found that after long periods (in excess of 5 years) there were documented substantial reduc-
tions in epilimnetic phosphorus, while the case of the reduction of hypolimnetic hypoxia was not
as strong.