Transcript Tuna for Lunch? A Case Study Examining Mercury Bioaccumulation

Bellringer
How much seafood do you eat
in the average week? What
types?
Are there any dangers
associated with eating seafood?
Mercury
The Minimata Disease
http://www.youtube.com/watch?v=ihFkyPv1jtU
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
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)
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
Herbivorous
fish
Phytoplankton (algae)
Zooplankton
Small fish
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)
Methods to study mercury contamination
Fish
Sediment
A plastic scoop was used to
remove the upper 2 to 4 cm of
bed sediment from 5 to 10
depositional areas; samples
Largemouth bass were
were composited into a single
targeted for collection; but
sample for each site.
34 different fish species
were collected.
Each sample was
homogenized and mercury
Fish caught by
levels were measured.
electrofishing, rod & reel,
and gill nets.
291 fish from streams
nationwide.
Fish fillet analyzed for
mercury
Water
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
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
Biomagnification
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.
Humans??
2000ppb
700ppb
Consumers 
Large fish
What happens to
contamination level for
each organism as you
move up the food
chain?
Consumers  small
fish
Consumers  Invertebrates
Producers  Algae/Plankton
300ppb
30ppb
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.
Trout
Hg
Pikeminnow
Smallmouth bass
Stickleback
Hg
Mysid
Sockeye salmon (fry)
Hg
Crayfish
Daphnia
(zooplankton)
Caddisfly
Algae (phytoplankton)
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
Image credits
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.html
Water sampling: http://www.usgs.gov/themes/factsheet/146-00/
Largemouth bass: www.dfw.state.or.us/.../largemouth_bass.asp
Herbivorous fish: http://en.wikipedia.org/wiki/Rutilus
Fish electroshocking: www.epa.gov/esd/land-sci/water/fig9.htm
Lake Washington: .: www.fs.fed.us/r6/mbs/photo_gallery/index.php?...
Sockeye salmon fry: http://cybersalmon.fws.gov/sockeye.htm
Daphnia magma: http://upload.wikimedia.org/wikipedia/commons/c/c0/Daphnia_magna.png
Signal crayfish: www.tdsfb.org/crayfish.htm
Mysid shrimp: reefkeeping.com/issues/2004-02/rs/index.php
Stickleback: pond.dnr.cornell.edu/.../stickleback.html
Cutthroat trout: www.usbr.gov/mp/lbao/native_american.html
Northern pikeminnow: fishandgame.idaho.gov/ifwis/fishingplanner/ht...
Smallmouth bass: pond.dnr.cornell.edu/.../smallmouth_bass.html
Caddisfly larvae: www.slnnr.org.uk/sitedescription/freshwater.html
Mercury biomagnification: pubs.water.usgs.gov/fs-216-95
Vermont mercury fish advisory: www.neiwpcc.org/mercury/advisories_materials.asp