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Science Notebook: Great Lakes Coastal Wetlands

Catch some big fish (and some really little ones, too) with scientists from EPA's Mid-Continent Ecology Division in Duluth, Minnesota. They're trying to see how fish larvae can serve as indicators of the ecological health of Great Lakes coastal wetlands. After taking samples to determine

  • how they use Great Lakes coastal wetlands as habitat,
  • what types of wetlands support which species, and
  • how the wetlands support the production of larvae,

they identify which species are present, measure how abundant they are, and analyze their tissue to figure out what's in their diet. Pack your foul-weather gear, though -- you may need it!

Sound Science: Coastlines, Larvae and EPA CSI: Oh My!

Dr. Joel Hoffman

In this podcast, Science Notebook Coordinator Dr. Dale Haroski and Dr. Joel Hoffman from EPA's Mid-Continent Ecology Division discuss what Great Lakes coastal wetlands are, why we care about them, and what fish larvae can tell us about the health of these critical wetlands.

(MP3, 22 MB, runtime 23:23)

Tools of the Trade

How do you take samples in something as huge as the Great Lakes coastal wetlands? With lots and lots of tools! Go sampling with some of our scientists and learn their tools of the trade (and see what they catch too!)

If You Were the Scientist

Can you think like a scientist? Put yourself into a scientist's shoes by taking this quiz.

You've been called-up to recommend a new test for assessing the health of Great Lakes coastal wetlands. The assay will be to test the chemical composition of fish larvae as a way to measure the relative health of a coastal wetland – you will be measuring the carbon and nitrogen stable isotope ratios in the fish tissue.

The carbon stable isotope ratio, C-13, will track the energy flow through the ecosystem – in impacted systems energy primarily flows through phytoplankton because other sources of primary production are light-limited in degraded, turbid environments.

The nitrogen stable isotope ratio, N-15, will track the amount of excess nutrients because septic systems and sewage processing plants give-off nitrogen with a different isotopic ratio than is naturally found in the environment.

What type of signal do you propose will be associated with degraded wetlands?

  1. Atmospheric carbon is relatively enriched in C-13 compared to respired carbon from aquatic sediments.
  2. Ground water with atmospheric nitrate has lower N-15 amounts than ground water with nitrate derived from human and animal wastes.

Less C-13 and less N-15

Less C-13 and more N-15

More C-13 and less N-15

More C-13 and more N-15


Who's Your Daddy?

Joel Hoffman and his colleagues sample fish larvae because they prefer these wetlands as habitat and because larvae are important to the health of fish populations. The larvae look a whole lot different as babies than they do as adults. Can you match the larvae with the correct adult fish? Answer key

Photo of mature fish A   a Photo of larval fish
Photo of mature fish B   b Photo of larval fish
Photo of mature fish C   c Photo of larval fish
Photo of mature fish D   d Photo of larval fish
Photo of mature fish E   e Photo of larval fish
Photo of mature fish F   f Photo of larval fish
Photo of mature fish G   g Photo of larval fish
Photo of mature fish H   h Photo of larval fish
Photo of mature fish I   i Photo of larval fish

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