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Lake ClassificationandCultural Eutrophication

1) How are lakes classified in regards to trophicstatus?

2) What is cultural eutrophication?

3) What are the success stories and continuingproblems of cultural eutrophication?

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Originally, lakes were classified as either oligotrophicor eutrophic, unless they were dystrophic—browncolored water due to dissolved humic substances

(tannins)

We have already talked about

oligotrophic vs. eutrophic

clear vs. green

orthograde vs. clinograde

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Ultraoligotrophic <5 ug/lOligotrophic 5-10 ug/lMesotrophic 10-30 ug/lEutrophic 30-100 ug/lHypereutrophic > 100 ug/l

Now classify lakes and their productivity based on TPduring spring circulation

http://resac.gis.umn.edu/lakeweb/wquality.htm

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Originally thought that lakes were all createdoligotrophic, but became eutrophic over time

Thought there was a natural ontongeny to lakes

Less productive

More productive

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Productivity strongly related to basin morphometry.

This progress through trophic states may be true forsome lakes, but some lakes were “born” productive.

August Thienemann (1882-1960) compared the ratioof the volume of the epilimnion to the volume of the

hypolimnion

epi/hypo < 1

oligotrophic

epi/hypo >1

eutrophic

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Cultural Eutrophication —increases in phytoplanktondue to human-induced increases in nutrient (P) input

But, humans alter lake productivity

By the late 1800s, and early part of the 1900s, itbecame clear that some lakes were becomingeutrophic much faster than was predicted

Lakes that had historically been clear were gettingdense blooms of blue-green algae and fish were dying

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This was happing to several large lakes

Lake Zurich, Switzerland Lake Constance, Germany

Lake Erie

europeforvisitors.com

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Dilution was thought to be thebest solution for wastes

Chicago Ship and Sanitary Canalreversed the flow of the

Chicago River

Chicago originally pumped itsraw sewage into Lake Michigan

Why was this happening???

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Why was this happening???

Both human waste and early

synthetic detergents(prevalent after WWII) werehigh in phosphorous

But in the 1960s, the limiting nutrient for algalgrowth was still a subject of debate

Most lakes are P limited, add

more P, increase algal growth

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Detergent industry argued that there was noevidence that excess P was harmful to lakes

This argument was far from being just academic,lots of money involved (taxpayers, municipalities,industry)

In 1960s and 1970s, huge debates over whatlimited algal growth—some said P, others N,

others C (CO2)

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Why phosphates in detergent?• softens the water• aids in cleaning

• keeps dirt particles in suspension

Developing alternatives was expensivefor the detergent industry

Took until 1994 to be eliminated

from most major laundry detergents(but still common in detergents forautomatic dishwashers)

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ELA Lake 226

D. Schindler 1974

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The LakeWashingtonStory—An Urban

Lake

Edmondson 1991The Uses of Ecology: Lake

Washington and Beyond

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Primary sewage treatment -- removes solidmaterial by filtering and settling.

Does not

removedissolvedmaterial

(nutrients)

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Secondary sewage treatment-- removesthe dissolved organic material.

Bacteria andothermicroorganismsconsume thedissolvedorganic

material

Does not remove the dissolved inorganicnutrients

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Tertiary sewage treatment--The final, mostcostly (and often not completed) stage in

sewage treatment

Removesphosphates

and nitratesfrom thewater

L k W h b l h l k

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1922 30 outfalls took sewage into Lake Washington

Lake Washington began as an oligotrophic lake

1851 The settlement that would become Seattle wasfounded

1883 The Seattle Sewerage agency constructed aseries of pipes to pump raw sewage out into the lake(outfalls) (this was a problem because most peoplestill got their drinking water from the lake)

1936 A i l di i l d

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1941 Secondary Sewage Treatment plants installed

1936 A partial diversion system was completed totake the raw sewage into Puget Sound (From 1956-1966, 70 million gallons per day of raw sewage was

pumped into Puget Sound).

This diversion was just for the outfalls that were

closest to Puget Sound. Which, at that time, wasmost of the people, but as Seattle expanded, sodid the sewage problem

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1955 G C A d t PhD d t

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Algae is Oscillatoria rubescens , a blue-green that

had been forming denseblooms in Lake Zurich.

1955 George C. Anderson, a recent PhD graduatefrom the University of Washington goes sailing.

Brings back a beer bottle full of algae to TommyEdmondson

www.ucmp.berkeley.edu/bacteria/ oscillatoria2.jpg

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Changes cost money:

1. To industry, which ispasses along to theconsumer

2. To the taxpayer

Public action can make

a difference

Edmondson recognizedthe problem andargued for diversion

1958 P bli t f

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1976 Recordtransparencies—Hugeincreases in Daphnia populations

1958 Public vote fortotal diversion of sewagefrom Lake Washington

1968 Total Diversion

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Wh did D h i i ?

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Why did Daphnia increase?

Oscillatoria interferes with Daphnia feeding, so

fewer Daphnia during peak eutrophication

Prior to eutrophication, Daphnia had traditionally

suffered heavy predation pressure by Neomysis ,www.delta.dfg.ca.gov/ baydelta/neompic.gif

Where did all the

Neomysis go?

Wh did ll th N m sis ?

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Where did all the Neomysis go?

Neomysis are a preferred prey for juvenile longfin

smelt

dnr.metrokc.gov/wlr/waterres/ lakes/fishmort.jpg

Reasons for smeltincrease are notobvious, but maybe linked to

improvements inbreeding habitat inthe Cedar River

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But, not all lakes recover this quickly, often due tointernal loading or lack of success with top-down

control

Lake Washington recovered as a result of both

bottom-up control (reduced nutrients) and topdown control (reduced predation on the grazers)

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Good Professor Edmondson(to the tune of “Good King Wenceslaus”)

Good Professor Edmondson looked outside one nooning,Looked out on Lake Washington, noticed it was blooming.All the other scientists asked what was polluting.Some said it was CO2; he said it was soo-oo-age.

The lake had turned a muddy brown from Oscillatoria,

Reminded of Lake Zurich, then, he was in euphoria.All of the Seattleites looked on with aversion.They believed their lake was dead, he called for diver-er-sion.

Voters took a public stand to make their lake look pretty.

Their task began in ’63; it ended with Lake City. They harkened to his learned words, pollution dropped to zero.Good Professor Edmondson had become a he-ee-ro.

By J.T. Lehman

Cultural eutrophication is still a problem

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Cultural eutrophication is still a problem

Mandatory sewage treatment and diversion (mostly)solved the problem of point-source pollution

Now cultural eutrophication is often caused by non- point source pollution

Use of fertilizer, changes in land use and climatechange interact to create new problems

Lake Tahoe Hatch et al 2001

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Lake Tahoe Hatch et al. 2001

Human impact began to increaseafter the 1960 Winter Olympicsat Squaw Valley

https://reader009.{domain}/reader009/html5/0427/5ae206fcb47d3

http://www.ilec.or.jp/database/nam/NAM02-01.gif Since 1968, transparency (Secchidepth) has declined by about 30cm/year

Streams are brining anincreasing amount of PP into the

lake after snowmelt

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Concepts to know

Is there a natural ontongeny to lakes?

What happened in Lake Washington?

Lake Erie and Lake Washington are twoexamples of lakes that were “saved”. Willall lakes respond to diversion? Why orwhy not?

Do we still need to worry about culturaleutrophication?

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Practice question

It is well established that many lakes in industrializedregions have experienced cultural eutrophication,primarily as the result of sewage pollution. Lake

Washington, USA, serves as a dramatic example of howdiversion of that sewage (and subsequent reduction inphosphorus pollution) can restore lake clarity. In otherlakes, however, reversal of the effect of phosphoruspollution has been slow to appear, primarily due to

internal loading. Please explain the process of internalloading, including a consideration of what types of lakesare most likely to be influenced by internal loading, andwhy it can slow down lake recovery from sewage pollution.

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