Physical Changes in Physical Changes in Nearshore HabitatNearshore Habitat

Scudder D. Mackey, Ph.D.Scudder D. Mackey, Ph.D.University of Windsor/Habitat Solutions NAUniversity of Windsor/Habitat Solutions NA

Lake Erie Millennium Network Conference Lake Erie Millennium Network Conference April 2008April 2008

Windsor, OntarioWindsor, Ontario

Abiotic (Physical) Characteristics of HabitatAbiotic (Physical) Characteristics of Habitat

EnergyEnergy –– oscillatory and oscillatory and unidirectional flows, shear unidirectional flows, shear stress, turbulence.stress, turbulence.Substrate Substrate –– bedrock, bedrock, composition, texture, composition, texture, hardness, stability, hardness, stability, porosity, permeability, porosity, permeability, roughness.roughness.Water MassWater Mass –– depth, depth, temperature, turbidity, temperature, turbidity, nutrients, contaminants, nutrients, contaminants, and dissolved oxygen.and dissolved oxygen.HabitatHabitat –– when physical when physical characteristics meet the characteristics meet the needs of a species or needs of a species or biological community for a biological community for a given life stage.given life stage.

EnergyEnergy

SubstrateSubstrate WaterWater MassMass

““HabitatHabitat””

((ClimateClimate))

((GeologyGeology)) ((HydrologyHydrology))

Aquatic Habitats are Three Dimensional and DynamicAquatic Habitats are Three Dimensional and DynamicCoastal Margin 0 m to 3 m water depth; Nearshore 3 m to 15 m watCoastal Margin 0 m to 3 m water depth; Nearshore 3 m to 15 m water depther depth

Mackey 2005Mackey 2005

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Multiscalar Habitat AssessmentMultiscalar Habitat Assessment

RegionalCoarse-Scale

Lake BasinCirculation

BathymetrySubstrate

Slope(GIS Model)

Sidescan SonarRoxAnn

Hydroacoustics

Underwater VideoLakebed Sampling

LocalFine-Scale

103 -104 m2

102 - 103 m2

101 -102 m2

10-1 - 101 m2

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Nearshore Stressors and Habitat ImpactsNearshore Stressors and Habitat ImpactsShoreline AlterationsShoreline Alterations (coastal margin)(coastal margin)

•• Altered Flows (littoral and nearshore)Altered Flows (littoral and nearshore)•• Loss of Littoral Sand (beaches, “coarsening “of nearshore habitaLoss of Littoral Sand (beaches, “coarsening “of nearshore habitats)ts)•• Loss of Connectivity (habitat fragmentation)Loss of Connectivity (habitat fragmentation)•• Habitat DestructionHabitat Destruction

Degraded Water QualityDegraded Water Quality (watersheds, coastal margin)(watersheds, coastal margin)•• Turbidity (tributary loadings, resuspension)Turbidity (tributary loadings, resuspension)•• Nutrients (productivity, dissolved oxygen)Nutrients (productivity, dissolved oxygen)•• ContaminantsContaminants

Introduction of Invasive SpeciesIntroduction of Invasive Species (nearshore)(nearshore)•• Dressenids, Round GobyDressenids, Round Goby•• Altered Nutrient Dynamics (nearshore shunt Altered Nutrient Dynamics (nearshore shunt –– dissolved oxygen)dissolved oxygen)•• Lakebed habitat structure, interstitial spacesLakebed habitat structure, interstitial spaces

Changing Water LevelsChanging Water Levels (regulation, climate variability)(regulation, climate variability)•• WaterWater--Level Extremes (highs and lows)Level Extremes (highs and lows)•• Location of LandLocation of Land--Water interface (change in shoreline location)Water interface (change in shoreline location)•• LongLong--term Change (when do we hit the ecological “reset” button?)term Change (when do we hit the ecological “reset” button?)

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Coastal Erosion Coastal Erosion –– Shoreline AlterationsShoreline AlterationsWaveWave--Dominated ProcessesDominated Processes

BeachesBeachesBluffsBluffs

MassMass--Wasting ProcessesWasting ProcessesSoil CreepSoil CreepDebris FlowsDebris FlowsSlides and SlumpsSlides and Slumps

SurfaceSurface--Water ProcessesWater ProcessesSheet Wash and Rill WashSheet Wash and Rill WashGully and Ravine ErosionGully and Ravine Erosion

Beaches are a natural form of shore Beaches are a natural form of shore protection.protection.Wide beaches absorb wave energy Wide beaches absorb wave energy and protect upland areas from erosion.and protect upland areas from erosion.Hardening of the shoreline has Hardening of the shoreline has significantly reduced littoral sediment significantly reduced littoral sediment supplies reducing beach widths and supplies reducing beach widths and altering nearshore habitat structure.altering nearshore habitat structure.

Wide beaches provideWide beaches providenatural shore protectionnatural shore protection

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Lake Erie Shore Protection TrendsLake Erie Shore Protection TrendsOhio Counties from 1870 to 1990Ohio Counties from 1870 to 1990

Source: ODNR Source: ODNR -- Ohio Geological SurveyOhio Geological SurveyTime (Years)Time (Years)18701870 18801880 18901890 19001900 19101910 19201920 19301930 19401940 19501950 19601960 19701970 19801980 19901990 20002000

Per

cent

Pro

tect

ed S

hore

line

Per

cent

Pro

tect

ed S

hore

line

00

1010

2020

3030

4040

5050

6060

7070

8080

9090

100100

AshtabulaLake

CuyahogaLorainErieOttawaLucas

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Nearshore Lakebed DowncuttingNearshore Lakebed DowncuttingUpdrift shoreline armoring Updrift shoreline armoring reduces sediment supply, reduces sediment supply, beach widths, and nearshore beach widths, and nearshore sand cover.sand cover.Entire sand sheet becomes Entire sand sheet becomes mobilized and erodes cohesive mobilized and erodes cohesive clay substrate.clay substrate.Wave energy increases due to Wave energy increases due to deeper nearshore water deeper nearshore water depths.depths.Process is irreversible.Process is irreversible.

Coarsening of nearshore Coarsening of nearshore habitats due to the loss of habitats due to the loss of protective sand sheets.protective sand sheets.“Lag instead of Sand”“Lag instead of Sand”

Irreversible downcuttingof nearshore profile

Bluff Recession

Cohesivematerial

Downcutting of Cohesive Nearshore Profile

"Small" volume of loose sand and gravel

Blu f f

sand cover consisting of isolated bars and small beachfrequent exposure of the cohesive material and availability of sand for abrasionfaster downcuttinghigher recession rates

DESCRIPTION:

Cohesi vemater i al

Courtesy Pete Zuzek Courtesy Pete Zuzek -- Baird & AssociatesBaird & Associates

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Sidescan SonarSidescan Sonar

SandSand

CoarseCoarsePavementPavement

(Boulder/Cobble Lag)(Boulder/Cobble Lag)

BedrockBedrock

SandSand

Bedrock areas are stable.Bedrock areas are stable.Lakebed downcutting notLakebed downcutting notan issue.an issue.

Port Maitland Port Maitland –– Grand RiverGrand River

Port Maitland Port Maitland –– Grand RiverGrand River Possible Ancestral ChannelPossible Ancestral Channel

1860 1880 1900 1920 1940 1960 1980 2000 2020 2040 2060 2080 2100 2120173.5

174.0

174.5

175.0

175.5

176.0

Wat

er L

evel

(m, I

GLD

85)

Year

Long-Term Climatic Cycles (Lake St. Clair)

Lake St. Clair Water Levels1918 – 2005 (USACE)

Predicted water levels with climate change effects and long-term cycles superimposed

Source: R. Nairn, W.F. Baird & Associates in Mackey et al. 2006

Scenarios

Changing Water LevelsChanging Water Levels Lake St. ClairLake St. Clair

Up to 1 m drop in lake level by Up to 1 m drop in lake level by 2050 (worst2050 (worst--case scenario)case scenario)22,000 ha (54,000 Ac) exposed22,000 ha (54,000 Ac) exposed

Change in shoreline locationChange in shoreline locationShallowShallow--water areas will be water areas will be exposedexposedLittoral sand trapped onshoreLittoral sand trapped onshoreWetland complexes will be Wetland complexes will be hydraulically isolated and hydraulically isolated and disconnecteddisconnected43 spawning sites, 33 species43 spawning sites, 33 species28 sites high and dry28 sites high and dryMore than 60 % of shallowMore than 60 % of shallow--water habit (< 1 meter) will be water habit (< 1 meter) will be lostlost

Newly exposed land surfacewith 1 m drop in Lake Level

Reported fish spawning sites(Goodyear 1982)

0 3 6 9 12 Kilometers

Lake St. Clair Bathymetry

> 6 m5 – 6 m

4 – 5 m3 – 4 m2 – 3 m1 – 2 m0 – 1 mNavigationChannel

N

EW

S

Mackey et al. 2006

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Use physical models to predict new Use physical models to predict new coastal margin and nearshore coastal margin and nearshore environmentsenvironmentsUse biophysical linkages to place Use biophysical linkages to place communities in suitable communities in suitable environments (habitat)environments (habitat)Identify areas and processes in need Identify areas and processes in need of protectionof protectionUse scenarioUse scenario--based approach based approach --uncertainties may be high due to uncertainties may be high due to nonnon--linear ecosystem response, linear ecosystem response, inadequate physical and biological inadequate physical and biological datadataAdaptive managementAdaptive management

We have “nothing to lose” as models We have “nothing to lose” as models can be used to more effectively can be used to more effectively manage existing resources under manage existing resources under “best“best--case” no change scenarios.case” no change scenarios.

0 2 4 6 81 Miles

Lake St. ClairPotential Coastal Marginand Nearshore Habitats

0 3 6 9 121.5 Kilometers

1 – 2 m

> 5 m4 – 5 m3 – 4 m2 – 3 m

Submerged AquaticsCoastal MarshEmbayed Wetlands

Integrated models can be used to predict the distribution of coastal hydrogeomorphic features and associated nearshore, coastal margin, and wetland habitats.

Beach and Barrier System

Protected Embayments

Emergent Aquatic Vegetation

Navigation Channel

0 2 4 6 81 Miles

Potential Coastal MarginNearshore Habitats

0 3 6 9 121.5 Kilometers

1 – 2 m

> 5 m4 – 5 m3 – 4 m2 – 3 m

Submerged AquaticsCoastal MarshEmbayed Wetlands

Integrated models can be used to predict the distribution of coastal hydrogeomorphic features and associated nearshore, coastal margin, and wetland habitats.

Beach and Barrier System

Protected Embayments

Emergent Aquatic Vegetation

Energy

W

N

S

E

What might the future What might the future look like?look like?

Mackey et al. 2006LEMN 2008LEMN 2008

SummarySummaryNearshore and coastal margin habitats are Nearshore and coastal margin habitats are severely altered and degraded.severely altered and degraded.Anthropogenic actions have modified flow paths Anthropogenic actions have modified flow paths and disrupted natural coastal processes.and disrupted natural coastal processes.Reductions in sediment supply has lead to the Reductions in sediment supply has lead to the “coarsening” of nearshore substrates.“coarsening” of nearshore substrates.Climate variability and changing Lake water Climate variability and changing Lake water levels will be major factor affecting nearshore levels will be major factor affecting nearshore and coastal margin habitats.and coastal margin habitats.