Something Fishy…Do Now

How much seafood do you eat in the average week? What

types?

Are there any dangers associated with eating seafood?

Objective

Students will be able to…-explain how mercury enters the food chain-list health effects of high levels of mercury on humans -Explain the difference between bioaccumulation and biomagnification.

Mercury

The Minimata Diseasehttp://www.youtube.com/watch?v=ihFkyPv1jtU

Tuna for Lunch? A Case Study Examining Mercury Bioaccumulation and BiomagnificationBy Caralyn B. ZehnderDepartment of Biological and Environmental SciencesGeorgia College and State University, Milledgeville, GA

Lesson Outline- Key Questions

1. How does mercury get into the food chain?

2. What is the EPA limit for mercury?

3. What are the factors that determine how much mercury an animal has in it?

4. What part of the population needs to be the most careful about ingesting mercury?

5. Is mercury the only substance with this type of problem?

How does mercury get into the food chain?

• ___________is the most common source of mercury pollution

• Natural sources of mercury are: _____

Group 2

Group 2

Coal-burning power plants most common source

Coal contains mercury naturally burned released into the air.

How does mercury get into fish?

Group 2

Group 2

Hg – in emissions (smoke)

50-75% from human sources

Hg - Deposited on land and into water

Methyl-mercury (MeHg)

Bacteria

Phytoplankton (algae)

MeHg

Zooplankton

MeHg

MeHg

MeHg

Small fish

Large fish

Start

Here!

Start

Here!

What’s the deal with MeMg?

Form of Mg determines toxicity.

Effects:-Immune system-Alters genetic enzymes-Damages nervous system

- Sense of touch, taste, and sight.

Doesn’t eliminate quicklyDoesn’t eliminate quickly

Each and every fish tested from nearly 300 water streams in the

U.S. was found to contain mercury.

Group 1

Group 1 Fish to look out for?...Help us out!

Figure 1: Mercury concentrations (ug/g) found in fish tissues of commonly sampled fish species.

Group 2

Group 2

Mercury concentrations (ug/g) found in fish tissues of commonly

sampled fish species.

US EPA criterion for

human health.

Factors that determine mercury concentration…

• How much food containing mercury the animal eats– Eating food without mercury

• How long the animal has lived– Biaccumulation

• How high in the food chain it is– Biomagnification

Group 3 & 4

Group 3 & 4

Bioaccumulation: The buildup of substances, such as pesticides or heavy metals, in an organism.

Absorbing faster than excreting

Mercury inMercury out

Bioaccumulation

Group 4

Group 4

An increase in concentration of a pollutant from one position in the food chain (trophic level) to the next.

If a substance can biomagnify:animals (predators) at the top can have higher concentrations than animals lower on the food chain.

Biomagnification

Group 4

Group 4

Just another way to look at

it…

Just another way to look at

it…

What does the relative size of each rectangle

represent in this diagram?

An anchovy eats zooplankton that have tiny amounts of mercury in them.

The anchovy eats many zooplankton, accumulating the mercury of each over its life.

A tuna then eats many of these anchovies over its life, accumulating the mercury of each of those anchovies into its body.

This continues up the food chain, with the concentration increasing each time.

Which would you predict to have a higher level of

mercury?

Size vs. Trophic level

Why might two types of animals that are very different in size have the same level of contamination?

They are on the same

level of the food chain

Group 3&4

Group 3&4

Bioaccumulation vs. Biomagnification

Bioaccumulation is the increase of toxins within an organism

Biomagnification is the increase of toxins between organisms of different trophic levels.

Group 3

Group 3

Who should be most careful?

Because…Possibility for nerve damage in developing

brains

Group 1 &

2

Group 1 &

2

Is Mercury the only example of bioaccumulation?

DDT insecticide

Birds ate infected bugs ->largest birds were

harmed the most

Eagle Egg shells too weak to protect the growing eaglet.

How much mercury do you have in you?

Calculate your mercury intake:http://www.nrdc.org/health/effects/mercury/calculator/start.asp

Write a 3 sentence explanation of this picture using the terms

bioaccumulation and biomagnification.