Transcript Mod24 Aquatic Restoration - Lakes

Aquatic Restoration
Lakes
Unit 6, Module 24
November 2003
Objectives
Students will be able to:
 differentiate between restoration, rehabilitation, and reclamation.
 compare and contrast functional restoration and structural
restoration.
 define lake restoration and describe its major goals.
 describe current statistics regarding lake stressors.
 identify special challenges encountered in lake restoration.
 define and identify ecoregions in Minnesota.
 indicate preventative steps used to control sources of water
pollution.
 describe the impact of phosphorus in a lake environment.
 discuss measures used to limit the impacts of phosphorus on
lakes.
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Objectives cont.
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assess the effectiveness of lake restoration through analysis of
site examples.
identify methods used to control levels of algal growth in lakes.
discuss the effectiveness and concerns of lake dredging.
describe the goals and principles of biomanipulation used in
lake restoration.
describe four types of zooplankton and explain their
importance.
discuss the effectiveness and concerns of using algicides.
identify physical methods used for controlling weed growth in
lakes.
discuss chemical and biological methods for controlling weed
growth in lakes.
relate the principles of lakescaping.
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Overview
Introduction
1. Lake Restoration
2. Stream Restoration
3. Wetland Restoration
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Restoration Defined
 “Return an ecosystem to a close approximation of
its condition prior to a disturbance” (Berger 1990)
 “Act of restoring to the original state or a healthy
or vigorous state” (Bradshaw 1996)
 Historic conditions previously existing on the site
will be re-established, including the entire function,
structure, and genetic composition
 Return of fundamental processes by which
ecosystems (biological and non-biological
elements) work
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Restoration, rehabilitation or reclamation?
Restoration to historic conditions as a goal is
often either impossible due to land use
changes in the watershed or too expensive
 Rehabilitation: returns certain functions and
structures of the natural ecosystem at a previous
state, but not the original condition
 Reclamation: provides services by returning certain
functions and structures bringing the ecosystem to a
useful state, but something other than the original
condition
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Function or structure? What are you trying
to restore?
Examples of Functions
 Surface and groundwater storage, recharge,
supply
 Floodwater and sediment retention
 Transport of organisms, nutrients, sediments
 Nutrient cycling
 Biomass production, food web support, species
maintenance
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Function or structure?
What are you trying to restore?
Examples of Structure
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Soil condition
Geological condition
Hydrology
Water quality
Topography
Morphology
Flora and fauna
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Ecosystem
Function
Reclamation
Original Ecosystem
Restoration
Rehabilitation
Degraded Ecosystem
(Modified from Bradshaw 1996)
Developed by: Axler and Reed
Ecosystem
Structure
Updated: 11/26/03 Lakes
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Setting Project Goals
“No one paradigm or context for setting
restoration goals” (Ehrenfeld 2000)
In the past, goals usually focused on:
• Single species
• Drawback: changes might be counterproductive for
other species
• Ecosystem functions
• Drawback: managers might either have specific
techniques in mind or only focus on obvious
degradations
• Services
• Drawback: could negatively impact functions or
species
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Basic Steps for Setting Goals
1. Identify stressors causing degradation
 Consider what scale should be used
2. Determine goals
 What are the ecological and socio-economic
limitations?
3. Develop techniques to reverse degradation
 What are the key processes involved with each
stressor?
4. Adaptive management
 What measurements should be taken during
the project to adapt restoration techniques?
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Lakes vs Rivers vs Wetlands
Lakes
 Major impacts affect water quality
 Most restoration methods focus on physical,
chemical and biological manipulation of the
water and sediments
Rivers
 Major impacts effect channel shape and bed
sediments
 Most restoration methods focus on manipulation
of the physical environment (channel)
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Lakes vs. Rivers vs. Wetlands
Wetlands
 Major impacts effect wetland hydrology
 Restoration methods focus on restoring original
hydrology
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Overview
 Introduction
 Lake Restoration
 Stream Restoration
 Wetland Restoration
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Lake Restoration – a definition
“Shift lake to a valuable,
resilient system in
which ecosystem
processes (structures
and functions) are
maintained for a given
state when subjected
to disturbance”
(Ludwig)
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Lake Restoration – another definition
“Emulate a natural,
self-regulating
system that is
integrated
ecologically with the
landscape in which it
occurs” (NRC 1992)
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Lake Restoration – and yet another
“To return the lake to a long-term, steady state
condition similar to its pre-disturbance condition
and in accord with reasonably attainable
conditions, as dictated by the characteristics of the
ecological region” (Cooke et al. 1993)
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Restoration vs Management vs Protection
 Restoration
 Return to a previously acceptable condition (or
as close as possible
 Management
 Improvement to enhance the stated beneficial
uses such as swimming, fishing, water supply,
wildlife habitat, etc
 Protection
 Prevention of adverse impacts
 Continued management and possible reapplication of restoration techniques
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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State of the Lakes
 Approximately 40.6 million acres of lakes in
U.S. (navigable waters including reservoirs)
 Great Lakes Status
 State of the Lakes Conference is a biennial
conference that presents estimates of the
environmental health of the Great Lakes
 http://www.epa.gov/glnpo/solec/
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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State of the Lakes
Of the 17.3 million acres assessed in 2000, 45%
impaired for one or more intended uses
 Aquatic life support, fish consumption, primary and
secondary contact, drinking water supply, agriculture
(irrigation and stock watering), industrial
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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EPA, 2000 Lake Stressors
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Lake stressors
STRESSOR
ACRES
Unknown
3,663,901
21.1
Agriculture
3,158,393
18.2
Hydro-modification
1,413,624
8.2
Urban runoff
1,369,327
7.9
Natural sources
1,066,925
6.2
Atmospheric deposition
983,936
5.7
Municipal point sources
943,715
5.4
Land disposal
856,586
4.9
Construction
691,100
4.0
Grazing
615,125
3.5
Habitat Modification
540,207
3.1
Developed by: Axler and Reed
PERCENT
Updated: 11/26/03 Lakes
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General classes of human activities and
the stressors associated with them
glei.nrri.umn.edu
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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How human activities link to specific stressors
glei.nrri.umn.edu
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Resultant problems
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Nuisance algae
Nuisance vascular plants
Acidification
Anoxia and related issues
Toxic substances
Pathogens
Non-algal color and
turbidity
 Sediment buildup
 Undesirable fisheries
 In other words ….
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Special challenges in lake restoration
1. Reservoirs
 Different hydrology and morphometry
 Large inflow tributary
 Generally large watershed, many shallow bays
 Many competing uses
 results in diverse restoration goals
2. Ecoregion concept
 Not all lakes are created equally
 Some lakes will always be more productive
than others
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Special challenges in lake restoration
Reservoirs
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Different hydrology and morphometry
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Large inflow tributary from far upstream
Generally large watershed, many shallow bays
Many competing uses
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Results in diverse restoration goals; more recently
this includes actual dam removal
Ecoregion concept
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Not all lakes are created equally
Some will always be more productive than others
Productive lakes are not necessarily “bad”; they
may be naturally more eutrophic and support
better fisheries
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Increased algae isn’t always bad…
Increased algal growth leads
to decreased water clarity
(secchi depth)
BUT
More food at base of food web
leads to increased fish yield
BUT
Not always the fish you want
Schematic from NALMS. 1990. The lake and reservoir
restoration guidance manual. 2nd edition. North American
Lake Management Society and USEPA Office of Water,
Washington, D.C. EPA-440/4-90-006 August 1990.
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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What are Ecoregions ?
 Areas with similar:
 Climate
 Landuse
 Soils
 Topography
 “Potential” natural vegetation
 Minnesota has seven major ecoregions
 Four ecoregions contain most of the lakes
 Water quality varies greatly from south to north
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Minnesota’s Ecoregions
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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1.0-3.3 ft
8-15 ft
5-11 ft
1.6-3.3 ft
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Source control – Prevention - 1
Prevention: The First Step
• Ensure that point sources are controlled by best
available technologies (BATs)
• Regulated by the National Pollutant Discharge
Elimination System – NPDES Permits
• Improve on-site wastewater collection and
treatment systems
• Leaky systems add nutrients, organic matter and
pathogens to lakes
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Fix problem septics systems and leaky
sewer lines (infiltration & exfiltration)
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Onsite wastewater treatment - Minnesota Issues
• 30% of Minnesotans use onsite (decentralized)
septic treatment systems; ~25% nationally
• ~50% failing or improperly designed (>250,000
residences in Minnesota)
• ‘Limited’ soils, wet spring, high water table,
frozen soils, small lots, sensitive water supplies
• Immediate public health hazards
• Longer-term nutrient issue (eutrophication)
• Development pressures on lakes increasing
• Conventional systems may be ineffective with
few or no available alternatives; unique cold
climate problems
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Source control – Prevention - 2
 Control urban and
agricultural runoff
 Control erosion
 stabilize the shoreline;
protect the riparian zone
 Maintain vigorously
growing filter zone of
grass, shrubs and trees
next to water surface
 Stabilize eroding bluffs
 Route drainage away
 Establish vegetation
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Source Control - 3
 Capture pollutants
(retention and detention
basins, constructed
wetlands)
 Control fertilizer usage
and grass clipping runoff
 “Manage” hydrology to
reduce peak flows
 Reduce impervious
surface
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Lake Restoration
General goals:
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Control excessive plant growth
Control nuisance algae
Improve clarity (algae and/or suspended
sediment)
Improve habitat for desirable species
Remove or control nuisance organisms
Alleviate oxygen depletion
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Lake restoration methods
Methods
•
Physical Controls
• Mechanical manipulation of water and/or sediment
• Chemical Controls
• Precipitants and herbicide addition to control
“limiting nutrients (P), suspended sediment,
acidification or organisms (algae, invasive
“weeds”, “trash” fish)
• Biological Controls
• Introduction or removal of organisms for
controlling algal blooms, invasive weeds, or other
aquatic nuisance species (exotic and invasive)
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Phosphorus review
 The next eight slides are duplicates from Unit 1
Modules 2+3 (Lake Ecology)
 They review the basic characteristics of
phosphorus and its distribution in lakes before the
next set of slides that focus on in-lake P control
 They discuss the link between anoxia, sediment P-
release and algal blooms using examples from
WOW lakes in the urban Twin City region of
Minnesota. Lake Onondaga, NY and Shagawa
Lake, MN are other good examples
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Where does phosphorus come from?
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Phosphorus – external sources
 Watershed discharge from tributaries (Non-point)
 Strongly tied to erosion (land use management)
 Stormwater (urban and rural) runoff
 Agricultural & feedlot runoff
 On-site domestic sewage (failing septic systems)
 Sanitary sewer exfiltration (leaky sewer lines)
 Atmospheric deposition in more pristine areas from
dust, soil particles and waterfowl (Non-point)
 Municipal wastewater (treated), combined sewer
overflows (CSOs) and sanitary sewer overflows
(SSOs); industrial discharges – mostly Point Source
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Phosphorus – internal sources
 Mixing from anoxic bottom waters with high PO4-3
 tied to Fe redox reactions
 at “high” O2 (just > ~1 mg/L), Fe forms insoluble ferric salts
(Fe+3 ) that precipitate, settle to the bottom, and adsorb PO4-3.
This prevents much from diffusing up into the hypolimnion
 under anoxic, reducing conditions (O2 <1 mg/L), the ferric ion
is reduced to the soluble ferrous ion (Fe+2 ) which dissolves –
allowing sediment phosphate to diffuse up into the water
 wind mixing from storms and during fall destratification can reinject this high-P water to the surface causing algal blooms
• Where lakes have been historically polluted by high Pinputs, this reservoir of P can exceed annual watershed
inputs (see Halsteds Bay & Shagawa data)
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Phosphorus – lake budget
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Halsteds Bay late summer mixing events
•
Run the color mapper from April 1999 through 2002 focusing on storm
events in mid August 1999 and 2000
•
START with MAP = TEMP and plot = DO to show variable stratification
•
Then switch to MAP = DO and PLOT = TEMP to show anoxic events and
discuss the release of P from sediments that swamps annual P-inflow
from watershed
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Medicine Lake– Algal blooms & mixing events - 1
Background:
• Medicine Lake is extremely productive because of
historically high nutrient enrichment from its watershed
(go to http://lakeaccess.org/lakedata/lawnfertilizer/mainlawn.htm)
• Major blooms of algae can be detected in the RUSS
data set as:
• supersaturated O2 (why ?)
• increased pH (why ?)
• increased chlorophyll-a or turbidity (why ?)
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Medicine Lake – Algal blooms & mixing events-2
Thursday
Color = O2
Saturday
Line = pH
Sunday
Friday-midnight
STRATIFY
RE- STRATIFY
MIX
Developed by: Axler and Reed
MIX
Updated: 11/26/03 Lakes
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Halsteds Bay – Algal blooms & mixing events- 3
Why did the phosphorus in the bottom water drop so
dramatically in August 1999 in Halsteds Bay ?
P levels drop
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Halsteds Bay – Algal blooms & mixing events- 4
First, focus on the ice-free season water quality
• relatively high epilimnion (surface)TP ~ 75-150 ugP/L
• chlor-a (algae ) builds up steadily to levels > 50 ug/L
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Halsteds Bay – Algal blooms & mixing events- 5
See how secchi drops as chlorophyll increases ?
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Halsteds Bay – Algal blooms & mixing events- 6
Now see how much TP is in the hypolimnion
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Halsteds Bay – Algal blooms & mixing events- 7
Summary slide without animation
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Medicine Lake - Storm mixing events
•This sequence
runs from 1-5 from
Aug 29-30, 1999
C
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Phosphorus inactivation
Goals:
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Control algal blooms and
noxious algae
Increase water transparency
Mechanisms:
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Decrease water column Pconcentration
Decrease internal P-loading
from sediments
Decrease suspended particle
concentration (due to algae
and/or inorganic silt and clay)
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Phosphorus inactivation assumptions
Assumptions:
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P concentration limits algal growth
Reducing ortho-P and particulate- P will result in
significantly reduced algal growth
 The water quality benefits outweigh the cost of
the treatment
 The beneficial effects of the treatment will persist
for some number of years
 this includes public perceptions as well as
actual water quality improvements and
economic costs
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Phosphorus precipitation and inactivation
Summary of method:
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Aluminum, iron or calcium salts are added
Floc forms an adsorptive lattice that binds
orthophosphate and small suspended particles
(algae, silts and clays)
Floc coagulates and settles to the bottom
Overall effect:
• Improved clarity
• Reduced water column P-concentration
• Reduced rate of P-release from the sediments
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Alum treatment - reactions
Chemical Reactions:
• Aluminum salts such as alum (Al2(SO4)3. 14H2O)) and
sodium aluminate (Na2Al2O4) form an insoluble,
hydroxide floc that adsorbs strongly charged anions
such as phosphate (-3) particularly well:
Al+3 (from dissolved salt) + H2O  Al (OH)3 + H+
• Some orthophosphate binds directly to the salts to
form insoluble aluminum phosphate that precipitates
out of solution:
Al+3 + HnPO4-3  AIPO4 (solid precipitate) + nH+
where n = 1 or 2 depending on pH
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Alum and Lime Lab - dosage rates
• Jar tests to estimate
dosage
• Adapted from drinking
water treatment
methods for particle
removal
• Boat application
• Surface propwash or
deep injection via hose
• Barge for surface or
deep delivery
Developed by: Axler and Reed
www.teemarkcorp.com/sweetwater/
Updated: 11/26/03 Lakes
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Alum application - notes
• Dosage: typically 50-500 gallons/acre depending on
• Ratio of internal to external P-loading
• Sediment-P levels
• Morphometry (volume, thermocline, sediment area, etc)
• Liquid alum contains 4.4% Al+3
• Liquid sodium aluminate contains 10.4% Al+3
• Buffering: 1 part sodium aluminate : 2 parts alum (vol)
• Project managers assume <50% efficiency in terms of
the expected removal of P based on theoretical removal
and on how evenly the floc blankets the lake bottom
• Effectiveness 7~10 years typically
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Alum treatment - summary
Effectiveness:
•
•
•
•
Widely used, high success
Rapid, fairly long-term (<10-15 years)
Needs to be buffered (pH 6-8) to reduce toxicity
Not effective if external loading and sedimentation
are not controlled
• Works well for lakes with extensive littoral and
wetland areas
• Effective in spite of anoxia which decreases the
effectiveness of iron treatment
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Other coagulants - Iron
Iron
 Usually added as ferric chloride (FeCl3) at 3-5 mg Fe/L
 Forms an insoluble ferric hydroxide complex [Fe(OH)3.nH2O]
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that precipitates as a rusty floc
Adsorbs phosphate and also reacts with phosphate to form
Fe(PO4) that is insoluble
However - the floc dissolves and P is released under
anoxic, reducing conditions where Fe+3 (ferric ion) is
reduced to Fe+2 (ferrous ion) which is soluble
Very effective in water treatment plants where oxygenated
conditions prevail
Also shown to be effective in shallow, eutrophic lakes in the
Netherlands despite occasional anoxia
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Other coagulants - Calcium
 Usually added as either lime [Ca(OH2)], powdered
limestone [CaCO3], or a mixture
 At high pH and high Ca+2, the lime dissociates to form
small particles of calcium carbonate that precipitates
Ca(OH)2 + CO2  CaCO3 + H2O (lime reaction)
 Large surface area for adsorbing PO4 and particles
 Demonstrated effectiveness in small agriculturally
impacted lakes in Alberta, Canada (called dugouts)
 Naturally hard water
 Drinking water problems associated with blooms of blue-green
algae (cyanobacteria)
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Calcium – acid rain mitigation
 Calcium minerals
have also been
added to lakes,
streams and even
watersheds to
buffer the effects
of acid rain
www.epa.gov/airmarkets/acidrain/index.html
 “Liming” neutralizes the acid which improves the
pH and causes aluminum to convert to an inert,
nontoxic form. It is not a “cure” for the problem.
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Calcium – Thrush Lake, MN liming
 Acid deposition
sensitive streams,
lakes and
watersheds were
limed as tests of
strategies for
mitigating potential
acidification impacts
May, 1988
• +4.5 tonnes of
powdered CaCO3
doubled alkalinity
• Too small a dose to
affect TP
 Acid Precipitation Mitigation (APMP) Program funded by
the US Fish and Wildlife Service (late 1980’s)
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Coagulants - safety issues
 Handling large quantities of chemicals
 Liquid alum and ferric chloride are acidic and
corrosive. Buffered alum, either with sodium
aluminate or calcium carbonate is more
convenient
 Quick-lime, CaO is sometimes used but it is very
caustic and dangerous to handle
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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Phosphorus precipitation examples (alum)
Example: West Twin
Lake, Ohio
• Dimictic
• Area: 30 ha
• Max. depth: 11 m
Impacts:
• Frequent algal blooms
Goal:
• Lower P in epilimnion by
reducing hypolimnetic P
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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West - East Twin Lake experimental design
Treatment methods (dosed in summer 1975)
• Divert wastewater inputs (1971-1972) at both sites
to minimize external P-loading
• Treat West Twin Lake hypolimnion with alum
(26 mg Al/l in the form of liquid aluminum sulfate)
• Use East Twin Lake as a “control”
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
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West - East Twin Lake results
Rates of release in bottom meter of water
“Control”
West Twin Lake
(mgP/m2.d)
East Twin Lake
(mgP/m2.d)
1973
4.24
2.83
1974
1.51
2.80
1975
2.68
2.67
1976
0.37
1.76
1978
0.67
3.34
1980
0.00
1.06
1989
2.02
4.05
“Alum”
Developed by: Axler and Reed
• P-release
decreased for
about 7 yrs
• Possibly until
1989 (~16 yrs)
Updated: 11/26/03 Lakes
U6-m24a-s67
West - East Twin Lake - more results
Evaluation:
• Initial increase of P in the treatment lake was most
likely from an untreated littoral-wetland area
• Internal loading was reduced for > 6 years
• Even with the so-called “control” lake, the success
of the combination of techniques used (diversion
and alum treatment) was not clear for the long-term
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s68
Mirror Lake, WI - alum treatment
Background:
Hypereutrophic urban
lake
• Area: 13 ac (5.3 ha) Zmax:
13 m
• Major cause: stormwater-P
(>50% of P-inputs)
Developed by: Axler and Reed
Mirror Lake,
Waupaca
County, WI
Updated: 11/26/03 Lakes
U6-m24a-s69
Mirror Lake alum treatment - results
VOLUME WEIGHTED MEAN PHOSPHORUS
Graph from Holdren, C., W. Jones, and J. Taggart. 2001
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s70
Mirror Lake - results
Restoration strategy:
• 1976- divert storm sewers;decrease P-loading >50%
• 1978- alum application to bind sediment-P and fall
re-aeration to prevent winter-kill of fish from low O2
Interval
TP-water (ug/L)
P-release (mgP/m2/d)
Re-alum 1978
>80
1.3
Alum 1978-1981
~ 20
0.07
Post-alum 1990
Developed by: Axler and Reed
~ 20-32
0.20
Updated: 11/26/03 Lakes
U6-m24a-s71
Dilution flushing
Goal:
Control Nuisance Algae
Method:

Dilute the
concentration of
nutrients within the
lake by adding nutrientpoor water, reducing
growth

Flush algae out of the
lake faster than they
can reproduce
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s72
Dilution flushing - limitations
Limitations:

Finding an economically affordable source of low
nutrient water for flushing

Potential impacts to downstream structures and
ecosystems due to increased discharge

Usually feasible only for small systems
 Commonly used for small urban park and golf
course ponds
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s73
Aeration & Circulation– Goals & Methods
Goals:
 Improve habitat for fish and invertebrates
 Disrupt algal buildup and growth
 Drinking water improvement (taste/odor/staining)
Methods:
 Add air or O2 to epilimnion, hypolimnion or under ice
 Sustain fish during O2 stress
 Inhibit P release from sediments
 Precipitate P from anoxic hypolimnetic water
 Oxidize organic matter and toxic H2S and NH3
 Oxygenation may use gas bubbling or liquid (LOX)
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s74
Aeration and Circulation – systems
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s75
Aeration and Circulation – methods (cont)
Methods:
 Circulate water horizontally to alleviate low oxygen
or disperse localized algal scums (bays and coves)
 Mix water vertically for aeration and/or to light limit
algae where nutrient control is not feasible
 Mix high CO2 water into epilimnion to retard scum-
forming species of blue-green algae
(cyanobacteria)
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s76
Aeration and Circulation - problems
“Side” effects:
 May exacerbate algal and turbidity problems by re-
suspending:




Surface sediments
Sediment- P
Hypolimnetic- P, NH3, and H2S
Anoxic water
 View August 1999 Halsteds Bay, MN sequence to see how
surface water quality can be affected
 Resting blue-green algae “spores”
 Many species of noxious bloom formers form resting stages
that settle to the bottom and are re-introduced during mixing
events that bring them and nutrients into the euphotic zone
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s77
Hypolimnetic Aeration
Goals:
 Introduce O2 into
hypolimnion for:
 Habitat improvement for fish
 Eliminate taste and odor
problems in drinking water
sources (especially
reservoirs)
 Precipitate Fe and Mn (to
reduce staining)
 Inhibit sediment P-release
Developed by: Axler and Reed
anoxia
Updated: 11/26/03 Lakes
U6-m24a-s78
Hypolimnetic Aeration
 Either avoid
destratification
•0
•Eutrophic
 To maintain thermal
regime for a “2-story”
fishery
 To avoid introducing
excessive nutrients and
toxic H2S and NH3 into
surface waters
 Or destratify if desirable
to overall goals
Developed by: Axler and Reed
T
NO3
anoxia
NH4
PO4
Updated: 11/26/03 Lakes
U6-m24a-s79
Hypolimnetic aeration with destratification
Holdren, C., W. Jones, and J. Taggart. 2001. Managing Lakes and Reservoirs. NALMS. EPA 841-B-01-006.
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s80
Case study: Camanche Reservoir, CA
“Speece” cones are one of many
commercial systems available
for aerating reservoir hypolimnia
and reservoir tailwaters
Comanche Reservoir Issues
•
•
•
•
Drinking water and irrigation
Salmon and trout fishery
Hydropower and flood control
Downstream discharge problems
associated with low
hypolimnetic O2 and high H2S
Developed by: Axler and Reed
www.eco2tech.com
Liverpool Water
Updated: 11/26/03 Lakes
Witch Barge
U6-m24a-s81
Hypolimnetic withdrawal- goals
Goals:
• Remove nutrient-rich water from hypolimnion
• Reduce overall nutrient levels to control algae
• Improve O2 levels in hypolimnion to provide fish
habitat, further reduce P-loading, and reduce
sediment of toxic metals, ammonia, and H2S
Method
• Discharge the water in the bottom layer of a lake by
siphoning, pumping, or selective release (dam)
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s82
Hypolimnetic withdrawal- summary
Summary:
•
•
Relatively inexpensive
Potential for long-term effectiveness by
increasing O2 and reducing internal P-loading
• May need for > 3-5 years to measure success
• Removing too much water may destratify lake
• May adversely impact stream water quality!
• Creates downstream impacts due to low O2, H2S,
high nutrients, thermal changes
• May entrain and harm sensitive organisms
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s83
Sediment oxidation - goals
Goals:


Promote denitrification to reduce sediment BOD
and ultimately P-release
 Depletes organic matter in sediments reducing
internal phosphorus loading
 Improves P-binding with iron hydroxide complexes
 Prevents sulfate reduction (eliminates H2S)
Oxidize the top 10-20 cm of lake sediments
NO3-

N2 (gas) = denitrification (anoxic)
heterotrophic ("burn" organic matter using NO3-, not O2)
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s84
Sediment oxidation - procedure
Procedure:
•
Ca(NO3)2 (calcium nitrate) solution injected into
the sediment to stimulate denitrification
•
FeCl3 (ferric chloride) may be added to
precipitate H2S as FeS (ferrous sulfide) in anoxic
zones and to produce Fe(OH)3 (ferric hydroxide)
in oxic zones to adsorb phosphorus
•
Ca(OH)2 (lime) may also be added to raise pH to
an optimal level for denitrification
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s85
Sediment oxidation - summary
Summary:
• Potential to reduce phosphorus release from
sediments by 50-80% (but few case studies)
• Expected to be less effective if internal P-loading is
low relative to external (from the watershed)
• May require iron additions to enhance P-binding
• May decrease sediment oxygen demand (SOD)
• Nitrate addition may exacerbate eutrophication
• Relatively few studies so there have been few
comprehensive evaluations of the method
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s86
Dredging: Lake sediment removal
Goals:
•
Control excessive
macrophyte growth
•
Remove excess
nutrient-rich muck
•
Deepen and increase
lake volume
•
Remove resting cysts of
noxious algae
•
Remove contaminants
Developed by: Axler and Reed
In some cases it may be
necessary to remove
sediment rather than treat it
Updated: 11/26/03 Lakes
U6-m24a-s87
Dredge methods
 Dry – drain most of lake to be able to use conventional
heavy construction equipment
 Wet – partial drawdown with excavation done from
barges or shoreland cranes
 Hydraulic dredging – usually suction from a cutter head
mounted on a barge. Silt curtain may be used to
contain the transport of turbid water from site
 Usually only 10-20% solids in the pumped slurry
 Pneumatic dredging – air pressure to force sediment
out of the lake
 50-70% solids in the effluent stream
 Less impact from off-site transport of TSS
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s88
Dredging effectiveness and concerns
 Most effective if source of sediment controlled
 Better success with lakes that have:
 Smaller watersheds
 Lower sedimentation rates
 Shallow depths
 Long residence times
 Organically rich sediments
 May cause short-term algal blooms and clarity loss
 May resuspend and mobilize nutrients and toxic
substances
 Sediment and process water disposal must be
considered
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s89
Dredging schematics
Clamshell dredge scoops
sediments into scows
that are towed to a
designated disposal area
and dumped
Hydraulic cutterhead
suction- transfers sediment
slurry via connecting
pipeline to settling basin on
shore or adjacent basin
bottom
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s90
Biomanipulation - goals
Goals:
• Control algal abundance where nutrient regulation
is not feasible
• Increase herbivore density to lower algal biomass
• Manipulate food web to reduce #s of planktivorous
fish and enhance the biomass of large bodied
cladoceran zooplankton (e.g. Daphnia sp.)
• Limit abundance of fish that disturb sediments and
enhance internal P-loading and O2 depletion
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s91
Biomanipulation – principles
Principles:
• Noxious algal blooms in some lakes, usually urban, are
impossible to control by decreasing nutrients – at least
without enormous cost and decades to recover
• Managing algae by enhancing the zooplankton that eat
them sidesteps the more difficult nutrient issue
• Cladoceran zooplankton reproduce faster and are
better grazers than the smaller copepods and rotifers
• Cladocerans are more vulnerable to fish predation and
so planktivorous fish must be regulated or removed
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s92
Biomanipulation – zooplankton review
The next few slides are taken from Unit 1
Module 2+3: Lake Ecology and summarize the
characteristics of the major groups of
zooplankton
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s93
Zooplankton – major groups
Major groups
 Crustaceans
 Cladocerans
 Copepods
 Rotifers
 Ciliated protozoans
 many flagellated forms are photosynthetic
phytoplankton
 Insects
 Migrating benthos (Mysids, Neomysids, Diaporeia…)
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s94
Zooplankton – key features - cladocerans
 Cladocerans (e.g. water fleas)
 Size: 100 –300 microns
 Migration – can be 10’s of meters daily
 Slow moving (relative to copepods and hungry fish)
 Selective feeders (edible vs inedible algae)
 Parthenogenic – “r-selection”, rapid reproduction
 Very effective at clearing the water column
Daphnia
Bosmina
Developed by: Axler and Reed
Chydorus
Holopedium
Updated: 11/26/03 Lakes
U6-m24a-s95
Zooplankton – key features - copepods
 Calanoids, Cyclopoids and Harpacticoids:
 Size: wide range overlaping cladocerans
 Cyclopoids often predatory
 Faster moving – less affected by fish predation
 Selective feeders (edible vs inedible algae)
 Many lifestages and slower growing – “k-selection”
 Distributed more evenly over day, seasons, depth
Calanoid
Developed by: Axler and Reed
cyclopoid
harpacticoid
Updated: 11/26/03 Lakes
U6-m24a-s96
Zooplankton - rotifers
 Size: small <50 microns
 Migration – can be 10’s of
meters daily
 Slow moving but small
size offers some
protection from adult
planktivorous fish
 Less selective feeders
(algae, bacteria,
protozoans, detritus, ???;
not well understood)
 Parthenogenic – “rselection”, rapid
reproduction
Developed by: Axler and Reed
Keratella
Polyarthra
Kellicottia
Updated: 11/26/03 Lakes
U6-m24a-s97
Other regulators of lake productivity - Grazing
Top-down Model
Bottom-up Model
 High rates of nutrient driven algal
• Nutrient inputs
drive algal growth




growth are decreased by intense
zooplankton grazing pressure
(usually cladoceran Daphnids)
Fishless lakes with low
invertebrate predation on grazers
Lakes where planktivorous fish
are regulated by predatory fish
(game fish) –usually managed
In these cases, algae are not
nutrient limited
management tool =
biomanipulation
Developed by: Axler and Reed
• Classic Pyramid
N+P
Updated: 11/26/03 Lakes
U6-m24a-s98
Potential Top-down effects on food chains
Low
Predators
HIGH
Predators
HIGH
Planktivores
Low
Planktivores
Low
Zoops
HIGH
Algae
= Smaller Zoops
less grazing
Low Secchi
O2 stress
high pH ??
Developed by: Axler and Reed
Larger Zoops
more grazing
HIGH
=
Zoops
Higher Secchi
less O2 stress
lower pH ??
Updated: 11/26/03 Lakes
Low
Algae
U6-m24a-s99
Biomanipulation – fish management
Methods
• Fish control
• Intensive netting
• Rotenone (poison)
• Stock increased #’s
of piscivorous fish
• Selective catch or
catch restrictions
• Control conditions
for fish and zoop
growth and survival
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s100
Biomanipulation- Summary
Summary:
• Considered experimental
• Requires complex knowledge of food
web processes (shallow lakes are
particularly poorly understood)
• Herbivores may not consume certain
blue-greens
• May be more successful in lakes
without large-bodied zooplankton
• May require external loading to also
be controlled
• Currently considered only a
management tool- not a restoration
technique
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s101
Lake Mendota Biomanipulation Project
Lake Mendota –large, urban,
limnologically “famous” lake
in Madison, WI
• Eutrophic with blooms of bluegreen algae
• Sewage effluents diverted out of
basin entirely by 1971
• Continued nonpoint pollution
from agricultural and urban
runoff
• 1987: attempt to control blooms
by a massive stocking of walleye
to reduce planktivorous fish
Developed by: Axler and Reed
1988 – hot summer causes
summerkill of Ciscos, the
major planktivore
 zoops increase and algae
decrease for few years
 Ciscos recover, anglers
hammer the walleye, zoops
decrease and algae are back
Updated: 11/26/03 Lakes
U6-m24a-s102
Algicide application – copper sulfate
Goal: Reduce or eliminate algae
CuSO4 application (“bluestone”) = most common
 Can be used in potable waters
 Inhibits photosynthesis and N2-fixation
 Often chelated to maintain solubility in alkaline or
hardwater, and in colored (I.e. high humic) water
 Widely used for periphyton control
 Dosage
 1-2 ppm in hard water and 0.3 –0.5 in soft water
 Usually surface applied to treat only the upper few
meters or small coves and bays or shoreline
 Application: broadcast granules, spray slurry, tow
mesh bags filled with granules or powder behind boat
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s103
Algicides – copper sulfate notes
 Heavily used to remove taste
and odor due to the
periphytic blue-green
Oscillatoria in many drinking
water reservoirs
 Concerns about
accumulation of copper in
sediments and impacts on
benthos
 Toxic to zooplankton and
young fish at pre-dilution
treatment concentrations
 Not equally toxic to all
species of algae, in
particular some of the
obnoxious target species are
less sensitive
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s104
Algicides – more about copper sulfate
 Will not prevent blue-green cyanobacterial “toxins”
– may actually release them during treatment
 May deplete O2 by creating sudden influx of
detritus
 Not a permanent solution!
 May need multiple applications throughout the year
and from year to year
 Although its use is generally not favored it has not
proven to be a major problem in most cases
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s105
Algicides – organic herbicides
 Few non-copper based algicides
 Endothallic acid in its Hydrothol formulation
 Can be effective, especially for blue-greens
 But is very toxic to zooplankton and is generally
used only for spot application
 Water use restricted for several days post-treatment
 Biodegrades rapidly and is a hydrocarbon that does
not persist and does not bioaccumulate
 Diquat
 Contact herbicide; sometimes applied with copper
 Usually spot application for periphyton
 Toxic to zooplankton but less so to fish
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s106
Aquatic herbicides – commonly used
•
Developed by: Axler and Reed
There are many formulations,
some marketed under several
different names. Check with
state and federal regulatory
agencies for specific
information
Updated: 11/26/03 Lakes
U6-m24a-s107
Algicides – barley straw
Mode of action:
 Not well understood but presumed to be phenolic
compounds that are by-products of
decomposition
 Decaying straw does not kill the algae already
present, but it prevents new algae from forming
 Barley straw is not considered detrimental to fish
health or production
 The anti-algal activity is only produced when the
straw is rotting in a well oxygenated environment.
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s108
Algicides – barley straw application
Typical dose:
100-250 kg/ha
(~90-220 lbs/acre)
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s109
Shading – dyes
Goal: Attenuate light to limit
algal growth
 Dyes are non-toxic but often
regulated as algicides
 Usually bluish gray
 How much tidy bowl is
needed to keep Tahoe blue ?
 Potential to affect
stratification, O2 , higher
plants and food webs
 Relatively expensive per
volume
 Surface covers used for some
drinking water reservoirs
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s110
Aquatic plant management – overview
 Nuisance growths of native and exotic macrophytes
(“weeds”) are often considered to be a major
problem and a focus for restoration
 They may be a problem because excessive growth
interferes with recreation, aesthetic values and even
habitat; they may also degrade water quality by
mobilizing sediment nutrients and by accelerating
O2 depletion during senescence (annual die-off)
 Because they are extremely important components
of aquatic ecosystems, initial efforts should focus
on defining the perceived problem, identifying the
potential negative impacts of “weed” removal and
then determining the “best” control measures
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s111
Plants – macrophytes – key features
Curlyleafed Pondweed
• Can be excessive from nutrient
enrichment – especially by exotic or
invasive species at disturbed sites
• Ecological importance:
• structural habitat & spawning site
• food (invertebrates, fish, wildlife)
• stabilize shoreline and sediments
• nutrient cycling (sed- N&P)
• may light-limit phytoplankton in
productive systems
• Difficult to re-establish
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s112
Watertransparency
transparency –– clear
state
Water
clearvsvsturbid
turbid
state
• Are they really a problem ?
• If not, leave them alone
because removing them
may create worse
problems that are difficult
and costly to reverse
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s113
Water
clearvs
vsturbid
turbidstate
state
Watertransparency
transparency –– clear
-2-2
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s114
Shallow lakes vs deeper lakes - “switches”
 Usually more productive – higher Aw:Ao ratio
 Plants vs algae
 Natural predominance of macrophytes over algae.
Human impacts can switch them from clearwaterplants to turbid water-algae state maintained by
 Poor fish management (carp, exotics, …)
 Inadequate shoreline protection of emergent veg
 Boat damage
 Pesticide and nutrient runoff (fish, grazers, plants)
 Susceptible to very obnoxious algal blooms
 Difficult to reestablish clearwater-macrophyte state
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s115
Aquatic vascular plants- key features
 Reproduce sexually by flowers and seeds and/or
asexually from stem fragments and shoots from
roots
 Need light therefore highly turbid lakes won’t have
dense beds of submergent plants
 Expansive shallow areas most conducive to
extensive beds
 Soft sediments and high energy shorelines can
limit rooting
 Mineral nutrition mostly via roots and so they are
difficult to control by water column nutrient
reduction
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s116
Weed control – physical methods
1. Benthic barriers
Goal: Smother and light-limit
plants; seal nutrients


Natural – adding sand, clay,
gravel
Artificial – plastic sheets,
geotextiles
Major issues:



Regulatory permits
Expense - usually small
beaches or dock areas
Porous versus non-porous
synthetic coverings
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s117
Weed control – physical methods
2. Dredging
Goal: Remove vegetation, seeds, substrate, nutrients
Dry – drain or drawdown water level
Wet – draglines, backhoes, scoops, etc
Hydraulic suction or cutterhead



Major issues:


Regulatory permits
Turbidity and nutrient release



May cause algal blooms
Extreme habitat disturbances
In-situ and off-site containment needed
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s118
Weed control – physical methods
3. Mechanical removal
Goal: Remove vegetation (shoots and/or roots)




Hand pulling (see Lake Smarts reference)
Cutting w/o collection
Harvesting w/collection
Rotatilling, hydroraking, …
Major issues:





Regulatory permits
Fragmentation may spread infestation and
decrease O2
Can be selective (or not)
Can increase turbidity, algae and disrupt habitats
Can increase chances for invasive and exotic sp
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s119
Weed control – physical methods
4. Water level control – Drawdown
Goal: Destroying vegetation by drying, freezing or
mechanical removal



Mostly used for modifying fish and waterfowl
habitat
May be intermittent or prolonged
Allows for shoreline manipulation and modification
Major issues:





Regulatory permits
Requires proper “plumbing” and disposal area
Shoreline erosion. habitat and aesthetics loss
Loss of water supply during drawdown
May promote undesirable growth of some species
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s120
Weed control – physical methods
5. Dyes and surface covers
Goal: Light limit vegetation


Dyes increase extinction coefficient for light
Covers may be on bottom or at surface
Major issues:





Regulatory permits – dye treated as an herbicide
Dyes may flush out – expensive in larger system
(useful in park and ornamental ponds)
Dyes – may affect aesthetics
Covers – interfere with recreation
Covers – can affect O2 exchange with atmosphere
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s121
Weed control – chemical methods
6. Herbicides (see also algicide slides)
Goal: Destroying vegetation

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Mostly used for fish and waterfowl habitat
May be intermittent or prolonged
Allows for shoreline manipulation and modification
Major issues:
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Regulatory permits; some have swimming,
drinking, fishing, irrigation, and water use
restrictions (check label and general permit)
Non selective removal may make matters worse
Toxicity to non-target invertebrates and fish
Habitat and aesthetics loss
Dissolved O2 depletion from rotting vegetation
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s122
Herbicides – the major chemicals used
 Copper sulfate – more often used for algae
 Endothall – non-selective contact herbicide
 Aquathol has lower toxicity to animals than
Hydrothol formulation, but is a poorer algicide
 Diquat – non-selective contact herbicide
 Low toxicity to fish but may be toxic to zoops
 Ineffective in muddy water
 Glyphosate - non-selective contact herbicide
 Low toxicity to fish but may be toxic to zoops
 Ineffective in muddy water
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s123
Herbicides – more chemicals
 Fluoridone – Systemic (kills entire plant) herbicide
that is potentially selective based on concentration
 Requires extended contact time (>30 days)
 Typically applied to whole lake, not smaller areas
 Recommended for selective control of Eurasion
watermilfoil
 midwest- mixed results because of difficulty in
controlling lake-wide dosage
 2,4-D – Systemic herbicide with some potential for
selectivity based on dose and timing
 Time delays for recreation and agriculture
 Not for use in water supplies
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s124
Aquatic herbicide application
www.ecy.wa.gov/
www.prolakemgt.com
www.aquaticanalysts.com
Developed by: Axler and Reed
•aquat1.ifas.ufl.edu/-intro.html
Updated: 11/26/03 Lakes
U6-m24a-s125
Weed control – biological goals
7. Fish, insects or pathogens
Goal: Consume or destroy vegetation; restore native
species
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Usually involves introducing non-native species
Fish - sterile grass carp used most often
Insects - weevils and other species targeting
Eurasian watermilfoil and other exotics
Microbial pathogens – fungi, bacteria, viruses
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Largely experimental in aquatic systems except for
fungal infection that may work well with herbicides
Re-establish native species, especially in disturbed
areas to restrict expansion of pest
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s126
Weed control – biological issues
7. Fish, insects or pathogens
Major issues:

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Regulatory permits – grass carp often banned
Unintended foodweb and vegetation alteration
may make matters worse (overgrazing and nontarget consumption by carp if densities are too
high)
Usually not expected to eradicate a pest species
Difficult to simulate ecosystem responses (control
species may become pests)
Integrated pest management involving
combinations of control strategies may work best
Re-establishing native plants and minimizing
disturbance may be a good long-term strategy
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s127
Weed control – biological methods
Triploid grass carp
(Ctenopharyngodon idella): the most
commonly used and effective
biological control currently available.
(www.aquat1.ifas.ufl.edu/mach2.jpg)
Milfoil weevil
(Euhrychiopsis lecontei): a native
insect that has a preference for the
exotic nuisance plant over its “natural”
plant food; being used to help control
the exotic Eurasian watermilfoil
(www.fw.umn.edu/research/milfoil/milfoilbc.html)
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s128
Lakescaping
Lakescaping is the process of restoring (re-vegetating) a
shoreline to correct an erosion problem or to improve
the fisheries and water quality of the lake or river
At the heart of the
lakescaping concept
is the creation of a
buffer zone along the
shoreline. A buffer
zone is a natural strip
of vegetation along a
property's frontage.
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s129
Lakescaping - principles
• Emergent vegetation, e.g. bulrushes and cattails,
reduce shoreline erosion caused by wind and boat
traffic and reduce sediment resuspension
• Plants provide a filter strip that helps absorbs lawn
fertilizer and pesticide runoff before it reaches the lake
• Buffer zones reduce lawn chemical usage because the
resulting lawn is smaller, and native plants in the buffer
zone do not need chemicals
• Unmowed shoreline wildflowers, grasses and sedges
are less hospitable to Canada geese- i.e. less bird feces
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s130
Aquatic plant control- field images
Hydroraking
www.aquaticanalysts.com
Rototilling
www.aquaticanalysts.com
Developed by: Axler and Reed
Lake Drawdown
www.dnr.cornell.edu/ext/wetlands
Clamshell Bucket Dredge
www.aquaticanalysts.com
Updated: 11/26/03 Lakes
U6-m24a-s131
Developed by: Axler and Reed
Updated: 11/26/03 Lakes
U6-m24a-s132