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Energy Flow and Food Webs

1) What was R. Lindemans contribution to ecology?

2) How can food chain length be determined?

3) What is bioaccumulation and biomagnification?

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Individual

Population

Community

Ecosystem

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Raymond Lindeman changed the way we think about

ecosystems

Died at age 27

Cedar Creek Bog, MN

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In 1941 arrived at Yale for a post-doctoral position with

Hutchinson.

Final chapter of his

Ph.D. thesis was an

essay on the

trophic-dynamic

aspect of ecology

Originally, rejected

for publication in

Ecology

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Trophic levels a subset of the community. Includes

species that acquire energy in the same way.

Primary producer

Primary consumer

Secondary consumer

Top carnivores

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Food Chains

vs.

Food Webs

nutrientswww.vacadsci.org/ jsr/tlist2.htm
http://www.vacadsci.org/jsr/tlist2.htmhttp://www.vacadsci.org/jsr/tlist2.htm

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Neo Martinez

Simple food chains are rarely found in nature

But can still ask questions about food chain length

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Long standing question in ecology....

What determines food chain length?

What are the main hypotheses?

Primary productivity

Ecosystem size

Productivity-size interaction

Why care?

Influences community structure

Ecosystem functionsContaminant concentration

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How to determine an

organisms trophic

position and

consequently food chainlength?

For example, what is thetrophic position of perch

adults in this food web?

Can use stable isotopes

to determine trophic

position

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Stable isotopes

Naturally occurring non-radioactive isotopes of N and C

15N 13C

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Stable isotopes

15N increases 3-4 with each

trophic level

13C does not change, so can be used to determine

source of carbon (e.g., littoral production vs. pelagic

production)

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Post et al. (2002) sampled

25 lakes

These lakes ranged in size

and TP

Ecosystem size and

TP were notcorrelated

Used stable isotopes to

determine trophic position of

the dominant piscivore

(bass, pike, walleye or trout)

What did they conclude

determines food chainlength?

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Food chain length is also an important

determinant of contaminant concentrations in

organisms.

Several types of toxic chemicals in the

environment, many are harmful to both aquatic

organisms and people

Some contaminants are unstable in the environment

and degrade quickly, others are persistent

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Neurotoxins- attack nerve cells

Heavy Metalskill nerve cells

Chlorinated Hydrocarbons (e.g., DDT)

disrupt nerve cell membranes.

Organophosphates and Carbamates

(organic insecticides)inhibit signal

transmission between nerve cells.

Carcinogens- cause cancer

Mutagens cause mutations in DNA

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Bioaccumulation - an accumulation of a contaminant

in an organism

Biomagnification -

increase inconcentration of

the contaminant

from one link in a

food chain toanother

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Polychlorinated biphenyls (PCBs)

PCBs a group of 200+ synthetic chemicals that

were used as insulating fluid for electrical

equipment like capacitors and transformers

Banned by the USEPA in 1979

Still present in many products made prior to 1979, and take a

long time to break down.

Health effects - changes in liver activity, possible effects onimmune, endocrine and reproductive systems, classified as

probable human carcinogens

Can be stored in human fat tissue for years

V d Z d d R 1996

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Vander Zanden and Rasmussen 1996

M

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Mercury in the environment is primarily the result of

human activities.

In lake and river sediments, bacteria create an organic

form of mercury methylmercury.

Methylmercury is very persistent in the environment and

biomagnifies.

Mercury

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below 0.05 unrestricted

0.05 - 0.2 1 meal per week

0.2 - 1.0 1 meal per month1.0 - 2.0 6 meals per year

above 2.0 no consumption

http://www.idph.state.il.us/envhealth/fishadv/fishadvisory04.htm

PCB Concentration (parts per million) Advisory Category

In order to protect the most sensitive populations, pregnant or nursing women,

women of childbearing age and children younger than 15 years of age are

advised to eat no more than one meal per week of predator fish. Since women

beyond childbearing age and males older than 15 years of age are at less risk

for the effects of methylmercury, these groups may continue to enjoy as manymeals of predator fish as they please.

Also concerns about mercury

L k Mi hi http://www idph state il us/envhealth/fishadv/lakemichigan htm
http://www.idph.state.il.us/envhealth/fishadv/fishadvisory04.htmhttp://www.idph.state.il.us/envhealth/fishadv/fishadvisory04.htm

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Lake MichiganCook and Lake Counties

Species and Meal Frequency

http://www.idph.state.il.us/envhealth/fishadv/lakemichigan.htm

Chinook Salmon

All Waters

Less than 30"

1 meal/month- or -

Larger than 30"

6 meals/year

Contaminant - PCBs

Coho Salmon

All Waters

All Sizes

1 meal/monthContaminant - PCBs

http://www.idph.state.il.us/envhealth/fishadv/fishadvisory_qa_pcb.htmhttp://www.idph.state.il.us/envhealth/fishadv/fishadvisory_qa_pcb.htmhttp://www.idph.state.il.us/envhealth/fishadv/fishadvisory_qa_pcb.htmhttp://www.idph.state.il.us/envhealth/fishadv/fishadvisory_qa_pcb.htm

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Rainbow Trout Brown Trout

All Waters

Less than 22"

1 meal/week

-or-

Larger than 17"1 meal/month

Contaminant

PCB

All Waters

Less than 22"

1 meal/month

- or -

Larger than 22"6 meals/year

Contaminant

PCBs

Yellow Perch

All Waters

All Sizes

1 meal/week

Contaminant

PCBs

http://www.idph.state.il.us/envhealth/fishadv/fishadvisory_qa_pcb.htmhttp://www.idph.state.il.us/envhealth/fishadv/fishadvisory_qa_pcb.htmhttp://www.idph.state.il.us/envhealth/fishadv/fishadvisory_qa_pcb.htmhttp://www.idph.state.il.us/envhealth/fishadv/fishadvisory_qa_pcb.htmhttp://www.idph.state.il.us/envhealth/fishadv/fishadvisory_qa_pcb.htmhttp://www.idph.state.il.us/envhealth/fishadv/fishadvisory_qa_pcb.htm

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Channel Catfish Lake Trout Carp

All Waters

All Sizes

Do Not Eat

ContaminantPCBs

All Waters

Less than 23"

1 meal/month

- or -

23" to 27"6 meals/year

- or -

Larger than 27"

Do Not Eat

ContaminantPCBs

All Waters

All Sizes

Do Not Eat

ContaminantPCB

S i l M Ad i
http://www.idph.state.il.us/envhealth/fishadv/fishadvisory_qa_pcb.htmhttp://www.idph.state.il.us/envhealth/fishadv/fishadvisory_qa_pcb.htmhttp://www.idph.state.il.us/envhealth/fishadv/fishadvisory_qa_pcb.htmhttp://www.idph.state.il.us/envhealth/fishadv/fishadvisory_qa_pcb.htmhttp://www.idph.state.il.us/envhealth/fishadv/fishadvisory_qa_pcb.htmhttp://www.idph.state.il.us/envhealth/fishadv/fishadvisory_qa_pcb.htm

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Special Mercury Advisory

Water Body Species SensitivePopulations

Others

Ohio River Largemouth bass, all sizes 1 meal/month 1 meal/week

Rock River

(Rockford to Milan Steel Dam)

Flathead Catfish, larger than 29" 1 meal/month 1 meal/week

Arrowhead Lake Largemouth Bass, all sizes 1 meal/month 1 meal/week

Campus Lake

(Southern Illinois University)

Largemouth bass, all sizes 1 meal/month 1 meal/week

Cedar Lake Largemouth bass, all sizes

White crappie, all sizes

1 meal/month

1 meal/week

1 meal/week

Unlimited

Devil's Kitchen Lake Largemouth Bass, all sizes 1 meal/month 1 meal/week

Kinkaid Lake Largemouth bass, all sizes

White crappie, all sizes

1 meal/month

1 meal/week

1 meal/week

Unlimited

Lake In the Hills Largemouth bass, greater than 15" 1 meal/month 1 meal/week

Midlothian Reservoir Largemouth bass, greater than 14" 1 meal/month 1 meal/week

Monee Reservoir Lar emouth bass all sizes 1 meal/month 1 meal/week

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Q:

What are the potential health effects for people who eat fishcontaminated with methylmercury?

A:

A: The developing nervous systems of fetuses and children could

be damaged if exposed to even small amounts of methylmercury. At

high doses, methylmercury can affect the central nervous system(causing such health problems as memory loss and slurred speech)

and can cause kidney damage and failure, and gastrointestinal

damage. The possible health effects depend on how much

methylmercury is stored in the fish and how much fish is eaten over

a period of time. Based on the amounts of methylmercury detectedin predator sport fish in Illinois, it is unlikely that people would

experience adverse health effects associated with exposure to high

doses.

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Q:

What about the fish I buy in the grocery store? Should I beconcerned that they may be contaminated with mercury?

A:

Fish such as shark, swordfish, king mackerel and tilefish contain high

levels of methylmercury. The U.S. Food and Drug Administration (FDA) is

advising pregnant women, women of childbearing age and children not toeat these fish. The FDA advisory acknowledges that seafood can be an

important part of a balanced diet for pregnant women and women of

childbearing age. The FDA advises these women to select a variety of

other kinds of fish, such as shellfish, canned fish (including tuna),

smaller ocean fish or farm-raised fish. These women can safely eat 12ounces per week of cooked fish. A typical serving of fish is from 3 ounces

to 6 ounces.

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Concepts to Know

What was the major contribution of

Lindemans trophic-dynamic concept?

Why do we care about food chain length?

How is trophic position estimated?

What are some major contaminants of

freshwater?

How do these contaminants influence

human health?

Practice question

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Practice question

In the first lab, you were introduced to depth-volume curves, which provide information on both

the size and shape of a lake. From a depth-volume curve, you can determine the maximum

depth of a lake (last point on the curve), how much water the lake holds (total volume), and

whether or not most of the water is in shallow or deep water (the shape of the curve providesinformation about the bathymetry).

Below are the depth-volume curves for Fair Lake and Clear Lake. Both lakes are located in

central Wisconsin, just three miles apart. Imagine you are at a dinner party and you must choose

to have your meal prepared from either a 25 lake trout from Fair Lake or a 25 lake trout from

Clear Lake. The lake trout is the top predator in both lakes. If you are concerned about your

health, from which lake should you select your fish dinner ? Please explain your choice.

2

4

6

8

10

12

0100 200 300 400

Depth(m)

Volume (m3 x 1010)

2

4

6

8

10

12

0100 200 300 400

Volume (m3 x 105)

Depth(m)

Fair Lake Clear Lake

09. foodwebs04

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