A Case Study Examining Mercury Bioaccumulation and Biomagnification
Tuna for Lunch? A Case Study Examining MercuryBioaccumulation and Biomagnification By Caralyn B. Zehnder Department of Biological and Environmental Sciences Georgia College and State University, Milledgeville, GA 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. 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) Methylmercury (MeHg) Highly toxic Gets into the food web Snail
Largemouth bass Phytoplankton (algae) Herbivorous fish Zooplankton Small fish 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) 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, 19982005: U.S. Geological Survey Scientific Investigations Report 20095109, 74 p. 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 homogenizedand 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 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 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. 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 Where in the U.S. were the highest concentrations of mercury in fish found?
EPA Fish Advisories The relationship between trophic position and mercury in the food web of Lake Washington. Methods collect fish, crustaceans, & zooplankton and measure methylmercury levels.
Mysid Daphnia (zooplankton) Crayfish Stickleback Pikeminnow Trout Caddisfly Smallmouth bass Sockeye salmon (fry) 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. Algae (phytoplankton)
Smallmouth bass Trout Pikeminnow Stickleback Mysid Sockeye salmon (fry) Crayfish Daphnia (zooplankton) Caddisfly Algae (phytoplankton) Algae (phytoplankton)
Daphnia (zooplankton) Stickleback Trout Caddisfly Crayfish Mysid Sockeye salmon (fry) Smallmouth bass Pikeminnow Hg Hg Hg 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. 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: