Eutrophication in Water bodies

By: Kelly Toy

Overview① What is Eutrophication② Eutrophication management Experiments③ Nitrogen or Phosphorus control Debate④ Case Study: Baltic Sea⑤ Recommendations

1. What is Eutrophication?• Definition• Sources• Process • Importance

Definition - EutrophicationDegradation of water bodies from

overfertilization of nitrogen (N) and phosphorus (P), resulting in excess plant biomass and consequently oxygen and habitat depletion.

Removing microalgal blooms at the Olympic Sailing Venue, China.

Seagrasses covered with attachedalgae in a Danish estuary.

Excess N and P from Human ActivitiesN and P enters water

throughRunoffWastewater treatment and

industrial dischargesAgriculture

Excess fertilizers, manureCombustion of fossil fuels

N in air acid rain water

Eutrophication Process

Excess N +P

Growth of Plant biomass

Blooms die and sink to sediment

Fish and wildlife die

Anoxia (no O2) in deep waters

Bacteria consume oxygen to degrade dead

biomass

Denitrification (no N) occurs in

anaerobic conditions

N-fixing cyanobacteria

dominate

Internal loading of P, system is

N-deficient

Why does Eutrophication matter?Global expansion of dead zones

oxygen depleted areas where fish and wildlife are extinct

Decreased biodiversityNew species invasionToxic algal blooms (some cyanobacteria)Aesthetically unpleasingSevere impacts on fisheriesEconomic detriment industries relying on

water quality/ aquatic ecosystems (tourism)

2. Eutrophication Management Experiments• 1970’s Schindler Experiment• Response• Effects on Lakes and Estuaries

1970’s experimentation37-years long with entire-ecosystem lakes

D.W. Schindler found: P controls

phytoplanktonReducing N increased

cyanobacteria

Response:U.S. and Europe ban P

in detergentsRamp up P removal in

wastewater treatment plants

Experimental Lake 226Ontario, Canada

N + P inputs

Only N inputs

Effect on Lakes and EstuariesWater quality in lakes improved dramatically

Eutrophication in estuaries increasedN pollution grew tremendously since the

1970’sN contributes to eutrophication in estuaries

(no N-fixing cyanobacteria, N can limit growth)

DefinitonsLake- Freshwater surrounded by landEstuary- Freshwater inlet connects to ocean outlet

• Salinity varies throughout water body

Dead Zones in Estuaries146 coastal regions affected by anoxiaEliminating fish and bottom-feeding life

formsSize of dead zones growing

Gulf of Mexico dead zone- state of New Jersey

3. N or P Control DebateEvidence for each side

Debate: N or P control?Reducing P increased eutrophication in

estuariesReducing N increased N-fixing cyanobacteria

Expert Liminologists are still debating which nutrient controls eutrophicationcannot perform Schindler experiments in

estuaries

Each water body is condition specific Region and environment/ecosystem

4. Case Study: Baltic SeaDescriptionHigh Societal StakesRecommendations

Case Study: Baltic Sea 9 countries

borderingLow salinity

estuaryN-fixers abundantSpatial extent and

intensity of Hypoxia (low O2) growing

Dual Nutrient reduction strategyAbatement plan was signed by all Baltic Sea

countries in 2007 cost $4 billion/yearUpgrade P urban sewage treatment

decrease eutrophication to levels in 1900-1920

High Societal Stakes $$Swedish Department of Agriculture

calculates N reductions in the plan cannot be fulfilled unless a large part of Swedish agriculture is shut down

Damaging aquatic ecosystemEconomic detriment to fishing and water

industriesMany Countries input Many Countries affected

5. RecommendationsResults should be well testedExpensiveOther ways to mitigate Eutrophication

RecommendationAll beneficial effects of dual N and P control

must be robustly predicted before implementing high cost of nutrient reductions

N abatement is a very expensive pilot studyMay favor cyanobacteria instead of water

qualityDo not install N removal technologies at ww

treatment plant yetContinue P reductions to reduce

sedimentationReduce both N + P at the source

In the meantimeWe can reduce N and P inputs without expensive treatment

Control Measures for Runoff of both N and P:Decreased use of fertilizersContainment and treatment of manureTillage practices that conserve soilVegetative buffers along shorelineMaintenance and restoration of wetlandsConvert croplands sensitive to erosion to other uses

that do not pollute waterwaysEating less meat – fewer fertilizers needed to grow

grain for livestock and less manure

ConclusionEutrophication is destroying aquatic

ecosystemsExperiments and Observations

How do we manage N and P?

ExpensiveSocietal effects on Countries

References1. Carpenter, S.R. Phosphorus control is critical to mitigating eutrophication. PNAS 2008, 105,

11039-11040. 2. Conley, D.J. et al. Hypoxia-Related Processes in the Baltic Sea. Environmental Science and

Technology 2009, 43, 3412-3420.3. Schindler, D.W. et al. Eutrophication of lakes cannot be controlled by reducing nitrogen input:

Results of a 37-year whole-ecosystem experiment. PNAS 2008, 105, 11254-11258.4. Lewis, W.M.; Wurtsbaugh, W.A. Control of Lacustrine Phytoplankton by Nutrients: Erosion of the

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1015.6. Howarth, R.; Paerl, H.W. Coastal marine eutrophication: Control of both nitrogen and phosphorus

is necessary. PNAS 2008, 105, E103.7. Schindler, D.W.; Hecky, R.E. Reply to Howarth and Paerl: Is control of both nitrogen and

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on the dynamic mass balance. PNAS 2009, 106, E312.Schindler, D.W.; Hecky, R.E. Reply to Bryhn and Hakanson: Models for the Baltic agree with our

experiments and observations in lakes. PNAS 2009, 106, E4.13.Bryhn, A.C.; Hakanson, L. Eutrophication: Model Before Acting. Science 2009, 324, 723.14.Jacoby, C.A.; Frazer, T.K. Eutrophication: Time to Adjust Expectations. Science 2009, 324, 723-

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