2008 Shallow Lake Ecology Crooked Lake Annual Meeting
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Transcript of 2008 Shallow Lake Ecology Crooked Lake Annual Meeting
Shallow Lake Ecology
Crooked Lake
Anoka County, MN February 2008
Coon Creek Watershed DistrictWenck Associates, Inc.
Presentation Objectives
Understanding Lake EcologyPhysical Lake Properties Biological Characteristics Water Quality
Drivers Diagnostic Tools
Shallow Lakes
Introduction to Management Tools
Crooked Lake Watershed
Physical DataParameter Crooked
Lake
Surface Area (ac) 114
Average Depth (ft) 9
Maximum Depth (ft) 26
Volume (ac-ft) 1,021
Residence Time (years) 7.4
Littoral Area (ac) 83
Littoral Area (%) 73%
Watershed (ac) 260
Watershed area does not include the lake surface area
http://waterontheweb.org/under/lakeecology/index.html
What is a Shallow Lake?
Generally, any lake that does not stay stratified throughout the summer season is a shallow lake.
MPCA defines a shallow lake as lakes with a maximum depth of 15 feet or less, or with 80% or more of the lake area shallow enough to support emergent and submerged rooted aquatic plants.
Presentation Objectives
Understanding Lake EcologyPhysical Lake Properties
Biological CharacteristicsWater Quality
Understanding DriversDiagnostic Tools
Shallow Lakes
Introduction to Management Tools
Aquatic Communities –
Plankton & Fisheries
Lake Zones
Pike
Clear-water state
Carp, minnows
Invertebrates
Algae
Submergedplants
SedimentResuspension
Turbid-water state
Trophic Cascades
Adapted from Metropolitan Council Environmental Services
Biomanipulation of Fish Community – Round Lake, MN
Rotenone was used to eliminate planktivorous fish in 1980
Restocked with Bass and walleye to control planktivores
Increase in water clarity for 2 years after manipulation
Shapiro and Wright 1984
Carp Exclusion
Crooked Lake Fish Community
0
500
1000
1500
2000
2500
3000
3500
Fis
h A
bu
nd
an
ce
1951 1969 1973 1979 1984 1986 1989 1991 1993 1994 1996 1998 1999 2004
Survey Year
Crooked Lake Trophic Group Total Abundance Historical Catch Summary for DNR Surveys
Forage Species Rough Fish
Pan Fish Top Predators
Crooked Lake Fish Community
0
50
100
150
200
250
300
350
400
Fis
h B
iom
as
s (
lbs
)
1951 1969 1973 1979 1984 1986 1989 1991 1993 1994 1996 1998 1999 2004
Survey Year
Crooked Lake Trophic Group Total Biomass Historical Catch Summary for DNR Surveys
Forage Species Rough Fish
Pan Fish Top Predators
Refuge for small invertebrates (especially Cladocera) against fish
predations
AQUATIC PLANTS
“Services” to people through bank edge protection against
erosion, products, (reed, sedge, biomass, fish and fowl),
amenity and conservation
Absorb wind and wave energy, minimizing turbidity caused by
sediment resuspension
High production creates sediment conditions
favoring nitrogen loss by denitrification and
phosphate availability through release
Food for invertebrates
Food for adult fish
Habitat, food cover and nesting materials for birds
Provide habitat for attached algae
Refuges for small fish against predators
Cover and habitat for piscivorous fish
Spawning habitat for fish
Maintenance of clear water
Maintenance of clear water
Moss et al. 1996
Typical Littoral Zone Vegetation
Graphic from: Smith, R.L. Elements of Ecology. 1992 Third Addition.
Crooked Lake Aquatic Vegetation
Frequency of Submersed Aquatic Plants in Crooked Lake
0.0%
5.0%
10.0%
15.0%
20.0%
25.0%
30.0%
35.0%
40.0%
Najas f
lexilis
P. am
plifo
lius
P. illin
oenis
P. pec
tinat
us
P. pus
illus/
folio
sus
Zannic
hellia
palu
stris
Zoste
rella
dub
ia
P. zos
terif
orm
is
Myr
ophy
llum
spic
atum
P. cris
pus
Species
Fre
qu
ency
Presentation Objectives
Understanding Lake EcologyPhysical Lake PropertiesBiological Characteristics
Water QualityWater Quality Conditions and DriversDiagnostic Tools
Shallow Lakes
Introduction to Management Tools
Water Quality Drivers
NutrientsTotal phosphorus is a limiting nutrient
The availability of phosphorus controls the amount of algal growth in a lake
Nutrient sourceStormwater runoffDirect deposition from precipitationInternal loading from lake sedimentsGeeseSeptic or Wastewater Discharge or Wastewater Discharge
Trophic States in LakesHypereutrophic - A very nutrient-rich
lake characterized by frequent and severe nuisance algal blooms and low transparency.
Eutrophic - A high level of plant nutrients and biological productivity and low oxygen content.
Mesotrophic – A moderate level of nutrients and photosynthetic productivity.
Oligotrophic - nutrient-poor , low photosynthetic productivity.
Relationship between TPand Transparency
Oligotrophic Mesotrophic Eutrophic Hyper-Eutrophic
Total Phosphorus (µg/L)
MPCA StandardsEcoregions
North Central Hardwood Forest
Western Corn Belt Plains
Parameters Shallow1 Deep Shallow1 Deep
Phosphorus Concentration (g/L)
60 40 90 65
Chlorophyll-a Concentration (g/L)
20 14 30 22
Secchi disk transparency (meters)
>1 >1.4 >0.7 >0.9
1 Shallow lakes are defined as lakes with a maximum depth of 15 feet or less, or with
80% or more of the lake area shallow enough to support emergent and submerged rooted
aquatic plants (littoral zone).
Total Phosphorus and Chlorophyll-a
Crooked Lake
Crooked Lake
05
1015202530354045
2000 2002 2003 2005 2006
Co
nce
ntr
atio
n [
ug
/L]
Summer Average TP [ug/L] Summer Average Chl-a [ug/L]
Secchi Depth Crooked Lake
Crooked Lake
0
1
2
3
4
5
6
7
2000 2002 2003 2005 2006
Sec
chi
Dep
th [
ft]
Summer Average SD [ft]
Lake Response Models
Internal LoadingNurnburg Approach
for Sediment Anoxia
Calculate anoxic factor
Sediment release rate
BATHTUBAnnual model
Phosphorus Sources
Crooked Lake
0
50
100
150
2000 2002 2003 2005 2006Tota
l Pho
spho
rus
Load
[lb
/ yr]
Watersheds Atmosphere Internal Load1
Lake Response Model
Crooked Lake
0
20
40
60
2000 2002 2003 2005 2006
In L
ake
Tota
l P
hosp
horu
s C
once
ntra
tion
[ug/
L]
Model Predicted TP [ug/L] Observed TP [ug/L]
Presentation Objectives
Understanding Lake EcologyPhysical Lake PropertiesBiological CharacteristicsWater Quality
Understanding DriversDiagnostic Tools
Shallow LakesIntroduction to Management Tools
Turbid and Clearwater States
Competing Equilibria in Shallow Lakes
Turbid StateHigh algal productivityLow aquatic plant
productivityLow grazer (zooplankton)
productivity
Clearwater StateLarge aquatic plant
communityLow algal productivityLarge grazer
populationScheffer 2004
Shallow Lake SwitchesDrivers that cause a lake to shift
from either the turbid or clear water state to the opposite stateClear scientific understanding of
forward switchesUnclear understanding of reverse
switches
More Development
(impervious surface)
= More Runoff
Invasive SpeciesCurly-leaf Pondweed Purple LoosestrifeZebra Mussels
Eurasian Watermilfoil
McComas, Unpublished data
Boating Impacts
Boat wakes contribute to shoreline erosionProp disturbance
Especially in shallow areasSediment scouring prevents plant establishment
(Asplund and Cook 1997)
Direct damage to plantsAreas with boat traffic demonstrate lower biomass
yields (Asplund & Cook 1997)
Turbidity and light limitationsScientific understanding is limited
Wave stress
Shoreline Development
Impacts
Additional runoffNutrients, herbicides,
pesticides
Overwater structures reduce light availability
Shoreline erosion
Loss of vegetation and habitatLower songbird density
(Lindsey et al. 2001)Lower green from density
(Woodford and Meyer 2002)Loss or disturbance of fish
spawning, feeding and rearing
Loss of wood structure from tree fall
Lower diversity of fish species in developed shoreline areas (Brazner 1997)
Reduction in vegetation abundance (66% Radomski 2005)
Crooked Lake Shoreline
Characteristics
Presentation Objectives
Understanding Lake EcologyPhysical Lake PropertiesBiological CharacteristicsWater Quality
Understanding DriversDiagnostic Tools
Shallow Lakes
Introduction to Management
Changing View of Lake Management
OLD VIEWSimple Cause
Effect RelationshipIncreased
Phosphorus resulted in Decreased water quality
NEW VIEWComplex Adaptive
SystemsHard to predict
Focus on Adaptive ManagementLearn by doingDiversity of
knowledge
Dietz et al. 2003. Science.
Strategy for Restoring Shallow Eutrophic Lakes
Forward switch detection and removal
External and internal nutrient control
Biomanipulation (reverse switch)
Plant establishment
Stabilizing and managing restored system
Lake Response to Restoration
Twin Lakes W.Q. Response Model
020406080
100120140160180
0% 10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Percent Load Reduction
Lak
e T
ota
l P
ho
sph
oru
s [u
g/L
]
Upper Twin
HypotheticalResponse
Lake Response to Restoration
Twin Lakes W.Q. Response Model
020406080
100120140160180
0% 10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Percent Load Reduction
Lak
e T
ota
l P
ho
sph
oru
s [u
g/L
]
Upper Twin
HypotheticalResponse
Competing Management Goals
Design Strategy
Implement
Monitor
Evaluate
Assess Progress
AdaptiveManagement
Implementation Depends on Cooperation
Guide implementation through:PartnershipsProgramsActivitiesAreas
Supports watershed planning:Enhanced description of water
quality concernsImproved understanding of key
processesFocus on solution development
Adaptive Management