Ecohydraulics in the Mississippi River: Freshwater Mussels

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Ecohydraulics in the Mississippi River
Freshwater Mussels Modeling

• Joseph A. Daraio
• Larry J. Weber
• IIHR Hydroscience and Engineering
• Teresa Newton
• USGS Upper Midwest Environmental Sciences Center

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Freshwater Mussel Biology

• Most native mussels in the Mississippi are of the
  family Unioniidae
• They have an unique life cycle
• Larval Stage when they are parasitic on a host
  fish
• Attach to fish gills for several weeks
• Dependent on fish for survival and dispersal

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Mussels Role in Riverine Ecosystems

• Nutrient cycling Interact with both sediment
  layer and water column
• Remove soluble nutrients from water column and
  deposit it in sediment through feces and
  psuedo-feces
• Uptake sediment nutrients and release them as
  soluble nutrients into the water column
• Bioperturbation of sediment
• Provide physical habitat for other organisms
• Stabilize the river bed
• Because of their importance to the ecosystem,
  mussels are an indicator species

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Mussels in the Mississippi River

• Early reports suggest mussel beds spanning the
  entire river width
• In the 1800s mussels were harvested to find
  pearls

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Button Harvesting

• Harvesting intensified with the rise of the pearl
  button industry, circa 1890
• Machines developed to punch out buttons from
  mussel shells

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Impact of Lock and Dam system

• 29 Locks and Dams between St. Louis and
  Minneapolis-St. Paul
• Blocks migration of host fish vital to native
  mussel dispersion and survival
• Alters flow patterns and the hydraulics of the
  system
• Navigation system includes wingdams that direct
  the flow into the main channel and reduces flow
  into side channels (example next slide)
• This has a significant impact on conditions at
  the river bed where mussels make their home

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Wingdams in the river
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Current threats

• Water quality
• Chemical pollution (point and non-point source)
• Thermal pollution
• Excess nutrients (non-point source, e.g.
  agriculture, lawns)
• Sedimentation
• ZEBRA MUSSELS

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Zebra Mussels

• Native to Caspian Sea
• First introduced to the Great Lakes in the late
  1980s in ships ballast
• First documented in the Mississippi River in 1991
• Very efficient feeders and compete with native
  mussels for food
• Attach to substrate with byssal threads, and can
  attach directly to native mussels

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Imperiled Mussels

• As a result of over-harvesting, habitat
  alteration and loss, pollution, and the
  introduction of exotic species, mussels are a
  very imperiled group of organisms
• NO other group of animals in North America is in
  as much danger of extinction as freshwater
  mussels
• At least 1/3 (possibly as many as 43) of the 300
  known species of mussels in North America are
  imperiled, threatened, or endangered.
• Currently, 4 species in the Upper Mississippi
  River are federally protected under the
  Endangered Species act
• Higgins eye
• Fat pocketbook
• Scaleshell
• Winged mapleleaf

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Ecohydraulics Research

• Hydrodynamics modeling of pools of the
  Mississippi River
• Habitat Suitability Index model using physical
  flow characteristics and known mussel tolerances
  of physical conditions
• Population dynamics model of native and zebra
  mussels

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Questions or Comments?