1. A Case Study Examining Mercury Bioaccumulation and Biomagnification
Tuna for Lunch?
A Case Study Examining Mercury Bioaccumulation and Biomagnification By
Caralyn B. Zehnder
Department of Biological and Environmental Sciences
Georgia College and State University, Milledgeville, GA

3. 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.

4. Methyl-mercury (MeHg)
Mercury Methylation
Bacteria convert inorganic mercury (Hg) to the organic form methylmercury (MeHg)
Hg – in emissions (smoke)
Hg - Deposited on land and into water
50-75% from anthropogenic (human) sources
Bacteria
Methyl-mercury (MeHg)

5. Methylmercury (MeHg) Highly toxic Gets into the food web Snail
Largemouth bass
Phytoplankton (algae)
Herbivorous fish
Zooplankton
Small fish

6. Methyl-mercury (MeHg)
Hg – in emissions (smoke)
Hg - Deposited on land and into water
50-75% from anthropogenic (human) sources
Bacteria
Methyl-mercury (MeHg)
MeHg
Zooplankton
Large fish
MeHg
MeHg
Small fish
MeHg
Phytoplankton (algae)

7. Report Objectives:
Describe the nationwide occurrence and distribution of mercury in fish tissue.
Evaluate mercury in streambed (bed) sediment and stream water.
Scudder, B.C., Chasar, L.C., Wentz, D.A., Bauch, N.J., Brigham, M.E., Moran, P.W., and Krabbenhoft, D.P., 2009, Mercury in fish, bed sediment, and water from streams across the United States, 1998–2005: U.S. Geological Survey Scientific Investigations Report 2009–5109, 74 p.

8. Methods Fish 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 was
homogenized 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.
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

9. Figure 1: Mercury concentrations (ug/g) found in fish tissues of commonly sampled fish species.
US EPA criterion for human health.
Concern level for piscivorous mammals

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

11. Hg concentrations in fish were several orders of magnitude higher than in stream water.
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 out
Mercury in

12. Where in the U.S. were the highest concentrations of mercury in fish found?
EPA Fish Advisories

13. The relationship between trophic position and mercury in the food web of Lake Washington.

14. Methods – collect fish, crustaceans, & zooplankton and measure methylmercury levels.
Mysid
Daphnia (zooplankton)
Crayfish
Stickleback
Pikeminnow
Trout
Caddisfly
Smallmouth bass
Sockeye salmon (fry)

15. Table 3
*Arthropods are organisms with segmented bodies, hard exoskeletons and multiple pairs of jointed legs. Aquatic examples include shrimp, crayfish, crabs, and insect larvae including caddisflies.

16. Algae (phytoplankton)
Smallmouth bass
Trout
Pikeminnow
Stickleback
Mysid
Sockeye salmon (fry)
Crayfish
Daphnia (zooplankton)
Caddisfly
Algae (phytoplankton)

17. Algae (phytoplankton)
Daphnia (zooplankton)
Stickleback
Trout
Caddisfly
Crayfish
Mysid
Sockeye salmon (fry)
Smallmouth bass
Pikeminnow Hg Hg Hg

18. Biomagnification: An increase in concentration of a pollutant from one link in a food chain to another.
If a substance can biomagnify, then animals (predators) at the top of the food chain will have higher concentrations than animals lower on the food chain.
Even small concentrations of chemicals in the environment can find their way into organisms in high enough dosages to cause problems.  

20. Image credits
Licensed photo of school of tuna: ©Tommy Schultz | Fotolia.com, #
Coal fired power plant:
Bacteria: :
Water sampling:
Largemouth bass:
Herbivorous fish:
Fish electroshocking:
Lake Washington: .:
Sockeye salmon fry:
Daphnia magma:
Signal crayfish:
Mysid shrimp: reefkeeping.com/issues/ /rs/index.php
Stickleback: pond.dnr.cornell.edu/.../stickleback.html
Cutthroat trout:
Northern pikeminnow: fishandgame.idaho.gov/ifwis/fishingplanner/ht...
Smallmouth bass: pond.dnr.cornell.edu/.../smallmouth_bass.html
Caddisfly larvae:
Mercury biomagnification: pubs.water.usgs.gov/fs
Vermont mercury fish advisory: