Bellringer

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

types?

Are there any dangers associated with eating seafood?

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

Key Questions to answer

• How does mercury get into the food chain?

• What is the EPA limit for mercury?• What are the factors that determine

how much mercury an animal has in it?• What part of the population needs to be

the most careful about ingesting mercury?

• 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: _____

Coal-burning power plants are the most common source of mercury pollution.

Coal contains mercury naturally, and when it is burned, the mercury travels up the smokestack and is released into the air.

Mercury Methylation

Bacteria convert inorganic mercury (Hg) to the organic form methylmercury (MeHg)

Hg – in emissions (smoke)

50-75% from anthropogenic (human) sources

Hg - Deposited on land and into water

Methyl-mercury (MeHg)

Bacteria

Methylmercury (MeHg)

•Highly toxic•Gets into the food web

Phytoplankton (algae)

Zooplankton

Snail

Largemouth bass

Herbivorous fish

Small fish

Hg – in emissions (smoke)

50-75% from anthropogenic (human) sources

Hg - Deposited on land and into water

Methyl-mercury (MeHg)

Bacteria

Phytoplankton (algae)

MeHg

Zooplankton

MeHg

MeHg

MeHg

Small fish

Large fish

291 fish from streams nationwide.

Largemouth bass were targeted for collection; but 34 different fish species were collected.

Fish caught by electrofishing, rod & reel, and gill nets.

Fish fillet analyzed for mercury

Methods to study mercury contaminationFish Sediment Water

A plastic scoop was used to remove the upper 2 to 4 cm of bed sediment from 5 to 10 depositional areas; samples were composited into a single sample for each site.

Each sample washomogenized and mercury levels were measured.

Stream-water samples were collected by dipping Teflon® or PETG (Nalgene) bottles in the centrer of streamflow by use of trace-metal clean techniques.

Samples analyzed for mercury.

Each and every fish tested from nearly 300 water streams in the U.S. was found to contain mercury.

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

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

US EPA criterion for human health.

What are the primary factors that determine how much mercury an

animal has in it?

• 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

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

Bioaccumulation occurs when an organism absorbs a substance faster than it excretes it.

Bioaccumulation results in the organism having a higher concentration than the surrounding environment.

Mercury inMercury out

Bioaccumulation

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

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

Biomagnification

Producers Algae/Plankton

Consumers Invertebrates

Consumers small fish

Consumers Large fish

Humans??

What happens to contamination level for each organism

as you move up the food chain?

30ppb

300ppb

700ppb

2000ppb

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.

Hg

Hg

Hg

Algae (phytoplankton)

Daphnia (zooplankton)

Stickleback

Trout

Caddisfly

Crayfish

Mysid Sockeye salmon (fry)

Smallmouth bass

Pikeminnow

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

Bioaccumulation vs. Biomagnification

• Bioaccumulation is the increase of toxins within an organism

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

How much mercury do you have in you?

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

Is Mercury the only example of bioaccumulation?

DDT was an insecticide that built up in birds that ate infected bugs. The largest birds were harmed the most

Eagle Egg shells too weak to protect the growing eaglet.

DDT nearly drove the American Eagle extinct

Licensed photo of school of tuna: ©Tommy Schultz | Fotolia.com, #4843675.Coal fired power plant: http://commons.wikimedia.org/wiki/File:Dominion_Power_Plant.jpg Bacteria: : www.nature.com/.../v2/n2/full/ngeo428.htmlWater sampling: http://www.usgs.gov/themes/factsheet/146-00/Largemouth bass: www.dfw.state.or.us/.../largemouth_bass.aspHerbivorous fish: http://en.wikipedia.org/wiki/RutilusFish electroshocking: www.epa.gov/esd/land-sci/water/fig9.htmLake Washington: .: www.fs.fed.us/r6/mbs/photo_gallery/index.php?...Sockeye salmon fry: http://cybersalmon.fws.gov/sockeye.htmDaphnia magma: http://upload.wikimedia.org/wikipedia/commons/c/c0/Daphnia_magna.pngSignal crayfish: www.tdsfb.org/crayfish.htmMysid shrimp: reefkeeping.com/issues/2004-02/rs/index.phpStickleback: pond.dnr.cornell.edu/.../stickleback.htmlCutthroat trout: www.usbr.gov/mp/lbao/native_american.htmlNorthern pikeminnow: fishandgame.idaho.gov/ifwis/fishingplanner/ht...Smallmouth bass: pond.dnr.cornell.edu/.../smallmouth_bass.htmlCaddisfly larvae: www.slnnr.org.uk/sitedescription/freshwater.htmlMercury biomagnification: pubs.water.usgs.gov/fs-216-95Vermont mercury fish advisory: www.neiwpcc.org/mercury/advisories_materials.asp

Image credits