Algae and Other Undesirables: Getting Rid of Yuck

31 Pages·2012·0.72 MB·English

Algae and Other Undesirables:
7
Getting Rid of Yuck
Introduction that do not mix easily. In relatively deep lakes, these
layers become less distinct during the spring and fall
Aquatic macrophytes, or rooted aquatic plants vex months and mix together in the process known as
many New York State lake users, but they are not destratifcation or turnover. See Chapter one, “Lake
the only signifcant in-lake problem. Algal blooms, ecology” for a full discussion of stratifcation and
nuisance species, and poor water quality may be related terms. Figure 1-7 illustrates stratifcation and
nearly as, or more, troublesome than macrophytes. turnover.
This chapter describes immediate and sometimes During stratifcation, the bottom water, or
short-term techniques for coping with these three hypolimnion, receives little or no exposure to the
common concerns. atmosphere, which can lead to oxygen depletion.
The in-lake management strategies presented in This is usually much more severe in the summer
this chapter and in Chapter six, “Aquatic plants,” stratifcation, during the four warmest months of the
are the primary mechanisms for correcting the most year. The hypolimnion is the location for reactions
prevalent water-quality problems. Those solutions with the sediment, degradation of organic materials
may alleviate the symptoms but do not solve the that have settled out of the water column, and
underlying cause. Approaches that deal with the un- signifcant biological activity. This combination of
derlying problem will lead to solutions that last longer oxygen depletion and chemical reactions can lead to
than those that only address symptoms. Chapter nine, deoxygenated, high-nutrient conditions.
“Watershed management,” will discuss the long-term,
watershed-based strategies that are the best way to
Artificial circulation
address the real cause of in-lake problems. Dealing
with “the big picture,” however, requires much ef- Principle
fort and time. The interim methods for dealing with
the symptoms usually keeps lake users happy while Artifcial circulation is the process which injects
longer-term solutions are being developed. compressed air from a pipe or ceramic diffuser into
the hypolimnion. With some circulators, water is
Algae control by physical means moved through the use of solar-powered impellors.
Either method can eliminate thermal stratifcation and
Algal blooms are among the most signifcant and improve the fow and movement of water within a
common lake problems encountered in New York lake. This may improve fsheries and reduce taste and
State lakes and, therefore, algae management is odor problems associated with ammonia, iron and
discussed frst. Techniques are grouped by physical, manganese by changing them to a reduced state. It
chemical and biological control. may also lower algae levels by inhibiting the release
The three management techniques that control of phosphorus from oxygen-depleted bottom sedi-
most algae through physical means all involve lake ments. A reduced state is the opposite of an oxidized
stratifcation. Lakes in New York State may stratify in state, changing the oxidation state of an atom by
summer and winter. When a lake is stratifed, colder, gaining electrons.
heavier water sinks to the bottom and lighter, warmer There are several ways that artifcial circulation
water rises to the top. This creates distinct layers can correct algae problems. Lake sediments may
169
Diet For A SmAll lAke
release bound phosphorus under low-oxygen condi- a distinct epilimnion and hypolimnion. Artifcial
tions, which encourages algal blooms when the lake circulationi sa p opulart echniques incei ti sb estu sed
turnso verin th ef alIl. ncreasedc irculationw ilrl estore alone. Many of the benefts in algae control, such as
sufciento xygent ob otomw atersa ndm inimizet his light-limitationa ndlo werp Ha, ren oet asilya chieved
nutrient release. In a lake with light-limited algae, by other restoration techniques.
mixingt hate xtendst ot hel akeb otomw ild ecrease Complete mixing by artifcial circulation wil
the time that individual algae cels are exposed to increaset het emperaturei nt heh ypolimniona sm uch
light, thus restricting their growth. This is referred as 15ºF to 20ºF. This could have disastrous efects,
to as the “critical depth” concept. Circulation may however, on the cold-water fsh species that thrive
improve zooplankton survival and increase preda- in the hypolimnion.
tion, which can reduce algae levels. Algae species Artifcial circulation may adversely afect lakes
mays hifft romb lue-greento le ssn oxiousg reena lgae that are not thermaly stratifed. Its use, therefore,
from the increased surface water contact with the should be limited to stratifed lakes. Portions of the
atmosphere, a lowering of the pH and incorporation lake, such as shalow coves or bays, are not good
of carbon dioxide-rich botom waters. candidates for this treatment if they are separated
The rising column of bubbles from the aerator, if from mixing with the stratifed layers in the rest of
suffcientlyp oweredw, ilp roducel ake-widem ixing the lake; if there is a signifcant litoral zone; and if
thate liminatest emperatured iferencesa ndr esultsi n the algae growth is nutrient-limited.
ac onstant emperaturet hroughout hew aterc olumn. Ins tratifedl akesw herea lgaea ren utrient-limited
Thed isintegrationo fth eth ermala yersa lowsm ixing in the epilimnion, artifcial circulation may increase
thate xposesb otomw aterst ot hea tmosphereW. hen the phosphorus levels in the upper layers, promot-
the temperature and density diferences between ing increased algae growth. This would decrease
upper and lower layers are nearly eliminated, wind transparency, and perhaps raise the pH, shifting the
and other natural mixing mechanisms wil assist in dominant algae from green to blue-green. The same
maintaining wel-mixed conditions. scenariom ayo ccurw heno nlyp artiald estratifcation
is achieved, especialy in lakes that do not possess a
distinct epilimnion and hypolimnion. These efects
Advantages and dsiadvantages
may be temporary since migration of nutrients from
Artifcial circulation can be used in most lakes sediment to hypolimnion to epilimnion may be
that exhibit summer thermal stratifcation and have r educed once deepwater oxygen levels rise.
Failure to achieve the desired objective with
artifciacl irculationm ayb ec ausedb yla kec hemistry,
insuffcientd esign,o re quipmentf ailure.C orrecta ir
fow pressure, system sizing, fow rate, and depth of
air release depend on the site conditions, and must
be properly designed to maximize success. Even
whena rtifciacl irculationis s uccessfult,h ep erceived
benefts are usualy delayed.
Costs
Costs for artifcial circulation are low, relative
Fig. 7–1.A rtifcial circulation using solar power, to other management techniques. The primary costs
showing compressor on the shore and pipe and hose to are for the compressor and instalation of pipes and
difusers siting on the lake botom. air difusers. The cost for artifcial circulation is
(C redit: ChriS Cooley) approximately $150 per acre of surface area.
170
AlgAe AnD other unDeSirAbleS: getting riD oF yuck
Regulatory issues
Case study: Artificial circulation
Circulators generally do not require permits, but in East Sidney Reservoir
the local New York State Department of Environ-
Lake setting: East Sidney Reservoir is a 210-acre
mental Conservation (DEC) Regional Offce should
impoundment in the north branch of the Susquehanna
be consulted to determine if wetland or other site-
River in south-central New York State.
specifc permits may be needed. The problem: High nutrient (phosphorus) concen-
trations resulted in excessive algal blooms, reduced
History and case studies water clarity, and hypolimnetic anoxia. Runoff from
a largely cattle and agricultural watershed increased
in New York State
nutrient loading in the lake.
Response: An artifcial circulation system was
Artifcial circulation was originally employed to
installed in 1989 to prevent anoxia in the bottom
reduce winter fshkills caused by oxygen depletion,
waters. The system consisted of a 15-horsepower
but is now commonly used to control eutrophication
compressor, 122 meters (m) of galvanized pipe,
problems in small ponds and reservoirs. It has been
305m of fexible hose, and eight 331m PVC pipe
rarely used in large New York State lakes, although
diffusers. The diffusers were joined, and a manifold
the frequency of use in recent years has increased.
and valve system controlled airfow to each section.
These projects have not been well documented. The diffusers were sited at a depth of about 9m from
1990 through 1992. The system was generally oper-
Hypolimnion aeration ated for 23 hours-per-day from late May through
mid-October. Airfow ranged from 0.3 to 1.1 cubic
Principle meters per minute during this period.
Results: Deepwater oxygen levels in the reservoir
Hypolimnion aeration is used to increase oxygen increased during the course of the study, resulting
circulation within a lake and increase oxygen content in lower phosphorus and metals concentrations in
of the deep waters without causing enough turbulence the bottom waters of the reservoir. Maximum total
to disrupt the stratifed layers. Aeration of the lake phosphorus levels in the hypolimnion ranged from
bottom waters uses an air-lift device to pump or lift 130 to 170 parts-per-billion (ppb) before and after
the study, but only reached about 50 ppb during
the deep, stagnant water layer for exposure to the
most of the study. Surface phosphorus readings
atmosphere. This results in aeration and the loss of
were actually higher in 1991. Average deepwater
some gases such as carbon dioxide and methane.
phosphorus readings also dropped from about 70
Then the water sinks back to the hypolimnion.
ppb before the artifcial circulation to about 40 ppb
H ypolimnetic aeration may also be accomplished by
during the study. Similar reductions occurred in
injecting pure oxygen or air into the bottom waters or
manganese and iron concentrations. Summer water
by using an air-lift device along with injection.
clarity and chlorophyll a readings were essentially
When the hypolimnion has suffcient oxygen, unchanged as a result of the artifcial circulation, and
release of phosphorus from oxygen-depleted bottom weak thermal stratifcation still occurred, resulting
sediments will be minimized, and this may result in in intermittent dips in dissolved oxygen levels and
decreased algae levels. Aeration also allows the lake occasional nutrient and metals release from bottom
to maintain suffcient oxygen levels for coldwater sediments.
Lessons learned: Artifcial circulation systems
fsh such as trout, without adversely increasing the
can be successful for minimizing some water-quality
water temperature or destratifying the lake. It can also
effects associated with deepwater anoxia, but these
reduce taste or odor problems associated with ammo-
systems must be carefully designed to assure full
nia, iron and manganese, an important consideration
circulation and to assure destratifed conditions
if deep water is being withdrawn for drinking water
during the peak stratifcation period of late spring
purposes. Aeration may also improve the quality of
through mid-fall (Barbiero et al, 1996).
hypolimnetic water discharged downstream.
171
Diet For A SmAll lAke
Advantages and disadvantages Regulatory issues
Hypolimnetic aeration is appropriate when lakes Permits to install and operate an aerator are re-
are stratifed and have a large hypolimnion. Aera- quired by DEC under Article 15 of the Environmental
tion systems are generally used only during summer Conservation Law (ECL), and by the Adirondack
stratifcation and not used during winter stratifcation Park Agency (APA) if the lake is within the boundar-
due to the decreased biological activity and higher ies of the Adirondack Park.
solubility of oxygen in cold waters.
The use of hypolimnetic aeration in shallow lakes History and case studies
and reservoirs with only partial stratifcation should
in New York State
be considered with great caution. Shallow lakes
without hypolimnion do not beneft from summer There have been very few attempts to aerate the
aeration. Some type of winter aeration might be ben- hypolimnion of lakes in New York State. The only
efcial in preventing fshkills in the most productive major project was Lake Waccabuc in Westchester
shallow lakes and ponds because ice cover that lasts County (see Case study on aeration). This project was
for months can prevent natural aeration. somewhat successful at increasing oxygen levels at
Although the stratifed layers are usually main- the sediment-water interface and reducing the migra-
tained during deep-water aeration, nutrients may tion of pollutants out of the lake sediment, but these
diffuse from the hypolimnion to the epilimnion dur- benefts were neither sustained nor extended higher
ing the process. This may increase the algae levels in the water column.
in the epilimnion and the thermocline.
Another potential disadvantage to hypolimnetic
aeration is the supersaturation of bottom waters with Case study:
nitrogen gas, which can lead to “gas-bubble disease” Aeration in Lake Waccabuc
in fsh. Since the nitrogen-rich gas cannot be dis-
Lake setting: Lake Waccabuc is a 140 acre lake in
sipated through exposure to the atmosphere, nitrogen
Westchester County, just north of New York City.
build-up can be signifcant in lakes that remain strati-
The problem: The lake experiences water-quality
fed for several months.
problems and invasive plant growth typical of eutro-
phic lakes with high nutrient loads entering the lake
Costs
through stormwater drains and other sources. The lake
thermally stratifes in the spring, and exhibits anoxic
Costs of aeration are dictated by the amount of
conditions throughout the hypolimnion during much
compressed air required to fully aerate the hypolim-
of the summer, resulting in an internal phosphorus
nion. This is a function of the lake’s hypolimnetic
loading that represents nearly half of the overall
area, the rate at which oxygen is used up, and the
nutrient loading to the lake (Martin, 2004).
extent to which the lake is stratifed.
Response: The Three Lakes Council represents
Aeration projects can be extremely expensive.
Lake Waccubuc, Lake Oscaleta, and Lake Rip-
Typical operating costs for six months of operations
powam. In the early 1970’s, the Council and Union
are estimated to be at least $2,500 per acre of surface
Carbide utilized local interest in protecting water
area. The capital cost for the equipment tends to be
quality and their desire to conduct an aeration study
very high, and the operating costs increase propor-
to develop a project in these three lakes. In 1972 two
tionally to the size of the lake. Most hypolimnetic
hypolimnetic aerators were installed at a depth of 45
aeration projects are funded by a research institute
feet on the bottom of Lake Waccabuc. Lake Oscaleta
or corporation. The funds necessary to carry out an
and Lake Rippowam were untreated in order to serve
aeration project are usually well beyond the means
as control studies.
of most lake associations.
172
AlgAe AnD other unDeSirAbleS: getting riD oF yuck
Results: The study conducted by Union Carbide It is not clear from an evaluation of these data (Fig.
reported the following (Three Lakes Council, 2001): 7–2) that coldwater fsheries could thrive as a result of
aeration. In-lake nutrients, such as deepwater phospho-
• a decrease in the in-lake nutrient concentrations
rus, hydrogen, sulfde, iron and manganese levels may
which otherwise would have been available for algae
have dropped due to the elimination of anoxia near the
production;
lake bottom. It also appears that by 2003, these aerators
• an improvement in water-quality conditions by were not functioning as effciently as they had in the
eliminating or decreasing hydrogen sulfde, iron and 1970’s and early 1980’s.
manganese levels; and Once the two-year experiment was completed, Union
Carbide funded the operation of the aerators by the lake
• creation of a suitable environment which can support
association for several years, after which local contribu-
a coldwater (trout) fshery.
tions covered the $15,000 per year cost of the system.
The lake association and local community also engaged
in septic and stormwater management activities to reduce
external nutrient sources to the lake. They developed
multiple water-quality monitoring programs to evalu-
ate long-term changes in the lake. In 2004, the aerators
operated at a cost of about $9,000 annually. In 2005, the
Three Lakes Council planned to conduct an additional
feasibility study for upgrading the aeration system.
Lessons learned: It is not clear from this study if aera-
tion would be successful in other lakes in oxygenating all
of the hypolimnion, and if it would be adequate to support
the stocking of coldwater fsh. These data do indicate
that some of the problems associated with an anoxic
Fig. 7–2. Temperature / Oxygen profles in Lake hypolimnion will be reduced, mostly those related to
Waccabuc August of 1972, 1982, and 2003. formation of hydrogen sulfde and related compounds.
green algae capable of regulating their buoyancy, may
Hypolimnetic withdrawal
also be selectively removed with this strategy.
The withdrawal serves to decrease oxygen defcits
Principle
and elevated nutrient (phosphorus) concentrations
Hypolimnetic withdrawal is most often accom - in the hypolimnetic waters of lakes. In time, the
plished through the installation of a pipe or siphon oxygen and nutrient conditions in the bottom waters
along the bottom of the lake, usually at the outlet. signifcantly improve, and the supply of nutrients
Water fows out of the hypolimnion by gravity, past available for release from the sediments may be
the outlet to the receiving waters. If there is insuf- ultimately exhausted. The hypolimnetic withdrawal
fcient elevation for gravity fow, an auxiliary pump takes a dvantage of the higher solubility of oxygen in
can be installed. cooler water to help restore oxygenated conditions to
The benefts from hypolimnetic withdrawal should the lake bottom. It may also help preserve the cold-
be greatest during the months of signifcant stratifca- water fsheries that may exist, or allow restoration of
tion and nutrient release, usually June through August. one that historically existed in the bottom waters.
Summertime hypolimnetic withdrawal serves to Hypolimnetic withdrawal can be used in strati-
remove the high-nutrient waters, thus reducing the fed lakes or small reservoirs with oxygen-poor or
potential for algal blooms when the epilimnion and nutrient-rich bottom waters. It has been particularly
hypolimnion mix during fall turnover. Some coldwa- effective for lakes where reductions in external nutri-
ter algae species common to New York State lakes, ent loading have been made but internal lake loading
including some species of Oscillatoria and other blue- has not been addressed.
173
Diet For A SmAll lAke
Advantages and dsiadvantages Costs
This is a relatively passive lake management For lakes with suffcient elevation to generate
tool. Withdrawal valves and water fow are mostly gravity fow (head), hypolimnetic withdrawal can be
inconspicuousa ndc ana chieveo xygenationa nda lgae one of the least expensive lake restoration techniques
controlw ithout heu seo fa lgae-kilingc hemicalso r available. For lakes with poor gravity fow, it may
large, artifcial circulation or aeration equipment. be necessary to install pumps and a piping system,
Them ost ignifcanat dversee fectso hf ypolimnetic which signifcantly increases the costs. The costs
withdrawal involve the discharge waters. Important can be low to moderate even with the cost of the
fshery streams below the lake outlet are particularly pumps and associated plumbing. Typical installation,
susceptible. Hypolimnetic waters with low oxygen maintenance, and operation costs for a pumped and
and high nutrient content can cause oxygen depletion, pipe withdrawal system has run from $35,000 to
algal blooms, and taste or odor problems in receiving $130,000 capital costs, and about $10,000 per year
waters. There may be noxious odors in the discharge operating cost.
waters due to the production of hydrogen sulfde in
the hypolimnion, rendering the mixture aesthetically
Regulatory issues
unpleasant for downstream residents. Hypolimnetic
waters may also contain elevated levels of ammonia, The DEC requires a State Pollution Discharge and
arsenic, or other dangerous compounds. The down- Elimination System (SPDES) permit for hypolimnetic
stream side-effects generally occur if the receiving discharges. Special attention is given to preserving
waters are nutrient-limited, or if the fow from the the quality of the receiving waters. Freshwater wet-
discharge constitutes a large percentage of the receiv- land permits would also be required by the APA for
ing waters. The fow associated with the discharge, lakes within the Adirondack Park.
like that from a surface discharge, may need to be
suffciently large to meet downstream fow and water- History and case studies
quality needs. This may dictate the sizing of the pipes
in New York State
and valves used to regulate this discharge.
Conversely, there may be some benefts for The use of hypolimnetic withdrawal as an in-lake
downstream waters, such as coldwater conditions management tool has not been attempted in any New
to support fsh propagation, but the additional need York State lake, although it has been proposed for
for high water quality may require treatment of the several large lakes. Galway Lake in Saratoga County
discharge. As more hypolimnetic waters are released has used a controllable gate about 20 feet below the
from the lake, the water quality of the discharges surface of the lake to reduce overall phosphorus
should improve as oxygen conditions in the hypolim- concentrations in the lake. The gate is opened from
nion improve. two to eight inches during the summer for intervals
Hypolimnetic withdrawal can also produce thermal of up to two weeks.
instability and possibly destratifcation. This intro- Hypolimnetic withdrawal is occasionally used
duces nutrient-rich anoxic water to the epilimnion, in New York State lakes and reservoirs for other
causing algal blooms, odor and taste problems, and objectives, such as supporting trout populations in
recreational and aesthetic impairments. If withdrawal downstream rivers and streams. Bottom water from
rates are greater than infow rates, withdrawal may the Ashokan Reservoir in the Catskills, for instance, is
cause an unintended lake drawdown. This is less released to support trout fsheries in Esopus Creek.
of an issue when using surface withdrawals, since One of the few well-documented instances of a
these are often self-regulated by the height of the hypolimnetic withdrawal in a New York State lake
boards, depth of the weir, or physical constraints of is an innovative project by Cornell University. Cold,
the control structures. hypolimnetic water from Cayuga Lake acts as a heat
174
AlgAe AnD other unDeSirAbleS: getting riD oF yuck
sink and provides air conditioning and refrigeration Some formulations of algacides use chelated
to portions of the Cornell Universitiy campus. This copper, which consists of copper combined with
is not a lake-management strategy since the benefts other agents to prevent staining. Compared to copper
associated with the project are not conferred to the sulfate, chelated copper tends to be less toxic, takes
lake itself. Environmental beneft associated with the longer to work and persists in the water longer.
utility heat exchange comes from the reduction of Not all algacides are copper based. Non-copper
contributions to global warming, since the alterna- algacides, usually involving an oxidizing agent,
tive would be the continued burning of fossil fuels are use to remove algae from the water and from
for campus cooling. Cornell benefts from reduced hard surfaces such as boats and docks. Chlorine can
energy costs. Questions remain regarding potential serve as an algacide in controlling fagellated algae
impacts to the lake with respect to: that move with the use of a whip-like tail, includ-
ing dinofagellates species common to many New
• Increased primary productivity associated with York State lakes. In very small ponds, non-copper
the introduction of nutrient-enriched hypolim- algacides may be used to oxidize algae cells, but
netic waters into the shallow, southern end of will generate hydrogen peroxide when the active
the lake; and ingredient reacts with water. Algacides using sodium
carbonate peroxyhydrate have been registered for use
• Aquatic ecosystem concerns related to damage
in New York State.
to small crustaceans (mysids) at the intake (Cal-
linan, 2004).
Advantage and disadvantages
Algae control with chemicals Algacides are one of the few algae control strate-
gies that work very quickly. These can be useful in
Algacides providing short-term relief while management plans
are developed for the long-term problem of control-
Principle ling nutrient in-fow. The quick action and low cost of
algacides accounts for its popularity. Copper sulfate
Algacides are generally copper-based chemicals could, theoretically, be effective on any lake with
used to kill algae cells, and to reduce the use impair- a fushing time greater than a few weeks since the
ments associated with excessive algal growth. The contact time to destroy algae using copper is very
copper inhibits the photosynthetic ability of the algae low. Copper sulfate has been used in a wide variety
cells, and may affect the way nitrogen compounds of lakes, from small swimming ponds and lakes to
are metabolized within the cell. Copper is sometimes the swimming beaches of very large lakes.
combined with some herbicides to reduce standing The use of algacides is also a multi-use control
populations of rooted plants as well as algae. strategy. It can be applied to waters used for recreation
Copper sulfate is the most common algacide and and it can even help control swimmers itch. Some of
one of the most popular algae control techniques. the copper compounds have been approved for use
Copper sulfate is usually applied in granular form, in drinking-water supplies, and may help to reduce
often dragged in burlap bags behind an applicator algae populations that can produce toxins or taste and
boat to ensure slow release. Liquid forms of copper odor compounds. This advantage may become more
sulfate can be applied where other copper formula- prominent as municipalities become increasingly
tions might bind with suspended particles, dissolved aware that chlorinating water supplies with heavy
organic matter, or carbonate ions, rendering them algae concentrations produces trihalomethanes and
ineffective for algae control. Copper sulfate can be other carcinogens. Use of algacides may be limited
used to control algal blooms, and in extreme situa- in lakes supplying drinking water since copper can
tions, to control excessive rooted plant growth. impart an unpleasant taste. Oxidizing algacides, such
175
Diet For A SmAll lAke
as those using sodium carbonate peroxyhydrate, can- quality testing and measurements and qualitative
not be used in treated drinking-water reservoirs. measures, through resident surveys and an assessment
Copper sulfate application may be restricted to of changes in recreational uses of the lake.
particular sites within a lake. This is due to the mixing Algae usually grow faster than zooplankton. Cop-
capabilities of the treatment lake, the dose rate, and per sulfate treatment may cause a “rebound” effect
the proximity to the treatment site of any signifcant shortly after application when algae levels increase
recreational sites, infow-outfow streams and water- faster than zooplankton levels. For many lakes,
intake pipes. multiple treatments may be required to keep algae
There are only limited data on the toxicologi- levels in check through the growing season and the
cal effects of copper on either humans or aquatic summer recreational season. Due to the potentially
organisms. Nearly all of these data consider only signifcant ecological side effects and limited effec-
the acute or short-term toxicity effects. Non-target tiveness of the treatment, however, it is likely that is
organisms may be adversely affected by copper sul- has achieved its popularity as an algacide primarily
fate treatments. Some fsh species and amphibians due to its immediate control and low cost.
are particularly sensitive to even moderate copper While copper can have a detrimental effect on
levels. Copper levels as low as fve ppb may have target and non-target organisms, certain species of
adverse effects on some aquatic organisms. Copper blue-green algae may be tolerant to copper, including
sulfate will also kill zooplankton, the microscopic the noxious species Aphanizomenon, Oscillatoria,
animals that feed on algae. Snails are susceptible and Anabaena. This may result in blue-green algae
to copper, and this has been exploited as a means concentrations greater than those that occurred before
for addressing swimmers itch problems as discussed treatment.
later in this chapter. Many of the potentially observable changes
Studies in New York State and Vermont have within the ecosystem after copper application may be
shown conficting results about the effect of copper masked by other water-quality changes. Many lakes
on benthic organisms. The DEC study of lakes treated experiencing algal blooms are also affected by other
with copper sulfate found elevated copper levels in the problems that previously altered the ecosystem. The
sediments, and some effect on the macroinvertebrate potential side effect associated with algacides may
diversity, particularly mayfies. These effects could not be easily detectable.
not be defnitively tied to sediment toxicity, since Algacides have been called “a temporary poison
lakes requiring copper treatments may suffer loss of for a permanent problem: (Stewart, 1986). It is “tem-
diversity due to the effects from eutrophication. porary” due to the resiliency and fast growth rate of
It is not clear that copper sulfate is acting as algae. It is “poison” due to the potentially toxic effects
anything but a placebo even if the side effects after of copper on several organisms within the food web.
copper sulfate treatment were either overestimated Copper serves as a micronutrient in the human diet,
or mistakenly tied to the treatment. Water-quality and is toxic to humans only at very large doses. It is a
data collected from several lakes that have been “permanent problem” because only the symptoms are
treated with algacides have not shown any signifcant addressed by copper sulfate treatments, not the causes
changes in either water transparency or algae levels or sources of excessive algae. While copper has an
after treatment (NYSDEC, 2004). The residents of immediate effect on existing algae concentrations,
the communities surrounding these lakes, however, the effect is usually temporary. Since this control
believe that the copper sulfate improved water quality strategy does not address the problem of excessive
in their lakes. It is unclear whether the same changes nutrient levels, or reduce internal or external nutri-
would have been perceived after the application of ent cycling, algae may return to pre-treatment levels
other control techniques or after no action at all. The within a short time. Some lake communities may fnd
effectiveness of any control technique should be it necessary to apply copper several times over the
verifed by both quantitative methods, through water- course of a summer.
176
AlgAe AnD other unDeSirAbleS: getting riD oF yuck
Case study: Algacides in Ballston and Kinderhook Lakes
Lake setting: Ballston Lake is a nearly 300-acre lake kg), and above the state sediment standard expected
in Saratoga County, just south of the southeast portion to result in “contaminated” sediment. Although these
of the Adirondack Park. Kinderhook Lake is a 350-acre, readings frequently result in toxicity for many benthic
12-meters deep impoundment of the Valatie Kill just macroinvertebrates, this was not found to be true in
south of the Capital District region of New York. Ballston Lake. It was found in many copper-treated
The problem: Ballston Lake suffers from frequent New York State lakes evaluated in this study, including
algal blooms, and the lake has relatively high phospho- Kinderhook Lake.
rus concentrations of about 25-30 In a typical year in Kinder-
ppb. Secchi disk transparency hook Lake, copper was applied
readings are typically about 2 to the lake in two-week intervals
meters, indicating low-water during the peak recreational
clarity. Like Ballston Lake, Kin- season, resulting in four cop-
derhook Lake has a long history per treatments. The impact on
of copper sulfate treatments, with blue-green algae levels and
regular and multi-year treatments water clarity can be seen in the
since 1960. The lake association following plots for copper treat-
became concerned over long- ments in 1998. (Collins, 2004;
term loading of copper in the lake NYSDEC, 2004)
Fig. 7–3a. Effect of copper treatments on
and sediments, and conducted an The results from the water-
Kinderhook Lake clarity.
experimental study of the use of quality monitoring indicate that
alum. blue-green algae levels dropped
Response: Copper sulfate has immediately after the treatments.
been regularly used to control This resulted in an increase of
excessive algae levels in Ball- about one foot in water clarity.
ston Lake since at least the early Within a week, clarity readings
1960s. There were whole-lake dropped again and blue-green
treatments after 1973, although algae levels increased. By the
treatments have not occurred time of the next treatment, both
since 1999. Typically, 1200 water-clarity and blue-green
pounds of copper sulfate were algae readings returned to the
applied in late June or early July, levels they had prior to the
resulting in application rates of treatment.
Fig. 7–3b. Effect of copper treatments on
about 0.3 parts-per-million. Lessons learned: Copper
Kinderhook Lake total phosphorus.
Results: The range of water- treatments in both Ballston Lake
clarity readings in Ballston Lake and Kinderhook Lake have not
in the late 1970s was from 1.7m to resulted in long-term decreases in
2.4m, slightly more compressed algae levels, and increase in water
but approximately equivalent to clarity appeared to be short-lived.
the same range found from the Sediment toxicity did not appear
late 1980s through the present to occur in either lake. While the
day. Phosphorus and algae levels residents of Kinderhook Lake
were in the same range. A DEC have experimented with the use
study of the lake in the mid-1990s of other methods for reducing
found that sediment copper levels algae levels, copper continues
of 175 milligrams per kilogram to be used extensively in many
(mg/kg) were above copper levels Fig. 7–3c. Effect of copper treatments on New York State lakes, including
in untreated lakes (10–20 mg/ Kinderhook Lake blue-green algae. Ballston Lake.
177
Diet For A SmAll lAke
Costs Hsitory and case studeis
ni New York State
Copper sulfate is one of the least expensive con-
trol techniques. Costs consist of chemicals and fees Coppers ulfateh asb eenu sedf orm anyd ecadesi n
required by the licensed applicators. Chemical costs NewY orkS tatel akess, omeo na b iweeklyt oa nnual
area $5 to $25 per acre­foot (one acre of surface basis. It is used yearly on more than 300 lakes and
area to a depth of one foot). The applicator costs pondst hroughout hes tatem, ostlyo ns malp ondso f
usualya ren ost ubstantialC. ostsf orc ontrolings nail lesst hant hreea cresM. osto ft heses mal-pondt reat -
populations should be comparable to algae control ments have not been wel document. Case studies
costs. fromB alstonL akea ndK inderhookL akea ret ypical
of copper treatments (see Case study on algacides).
Regualtorys isues
Nutreint precpitaiotin andn iacvtiaotin
Copper sulfate use is governed by both state
law (6NYCRR Part 327) and approved pesticides
Prnicpiel
labels. Permits and licensed applicators are required
for treatment of public lakes with copper sulfate or Nutrientp recipitationu sesa c hemicala gents, uch
other algacides. Purchase permits suffce for ponds asa lumto, r emovep hosphorusf romth ew aterc olumn.
ofl esst hano nea crew ithn oo utletP. urchasep ermits Nutrient deactivation works by sealing the botom
alow for the use of copper sulfate by the general sediments to prevent the release of phosphorus to
public, rather than a licensed applicator, provided theo verlyingw aterw ithl owo xygenc oncentrations.
that the label instructions are folowed. When cop- These two actions reduce nutrient concentrations in
per sulfate is to be used for treatment of snails or the water and often result in decreased algae levels
macroinvertebrates, permits have not always been andi ncreasedw aterc larityP. hosphorusp recipitation
required, although that is curently under review by and inactivation are used primarily on lakes with
regulatory agencies. signifcant internal nutrient loading and where the
Treatments are generaly restricted to the time external nutrient loads have been reduced as much
period from May to September. Treatments after as possible. This method is also commonly used on
Labor Day require special authorization by DEC. smals wimmingp ondsa ndl akest hata rep laguedb y
Repeat reatmentsa ren ota loweda ti ntervalso fl ess nuisance algal blooms.
than two weeks, and use of the lake for bathing and In a process caled focculation, the chemical
livestock watering is prohibited for at least 24 hours agentb indst op hosphorusc, ausingi t of ormh eavier
folowinga t reatmentD. osagesa ren ot oe xceed0 .3 aggregates that precipitate out of the water column.
ppm copper sulfate or 0.2 ppm for chelated copper Aluminuma nd,l essf requentlyi rons altsa reu sedt o
in the upper six feet in ponds or lakes with over two focculate due to their high affnity for phosphorus.
acres of surface area. For lakes with low alkalinity, Aluminum sulfate, or alum, the most commonly
lower dosage rates are computed based on alkalin - used binding agent, can be used in either granular
ity measurements, and product labels indicate that it or liquid form.
shouldn otb eu sedi fc arbonateh ardnesso ft hew ater Alum added at smal dose rates can achieve
is less than 50 ppm. It must be applied as a liquid phosphorus precipitation but may not be suffcient
(spray) or solid (with burlap bags), not by direct top rovidei nactivationA. luma pplieda ta l arged ose
broadcasting of the crystaline form. can provide long-term inactivation that includes
Non-copper algacides are restricted-use pesti- sealing the botom sediments. This minimizes the
cides. They are available for use only by licensed releaseo fb iologicalya vailablep hosphorusf romth e
applicators, not by the general public, and thus are lake sediments when oxygen is depleted from the
subject to the same regulations as copper products. hypolimnionL. argerd osesa reo ftena ddedd irectlyto
178