Estuaries: Definition

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The Problem With Estuaries
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Why Are Estuaries So Important?

• Interface between land, ocean, and rivers
• Vital habitat for fish, shellfish, waterfowl
• Contain some of the most productive ecosystems on
  the planet
• Transportation routes and recreational
  opportunities for humans
• Some of the most densely populated coasts in the
  world

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Importance of Estuaries
Estuaries provide habitat for more than 75 of
America's commercial fish catch, and for 80-90
of the recreational fish catch (5).
Estuarine-dependent fisheries are among the most
valuable within regions and across the nation,
worth more than 1.9 billion in 1990, excluding
Alaska (4). Nationwide, commercial and
recreational fishing, boating, tourism, and other
coastal industries provide more than 28 million
jobs (2). Commercial shipping alone employed more
than 50,000 people as of January, 1997 (5). There
are 25,500 recreational facilities along the U.S.
coasts (5)- almost 44,000 square miles of outdoor
public recreation areas (4). The average American
spends 10 recreational days on the coast each
year. In 1993 more than 180 million Americans
visited ocean and bay beaches- nearly 70 of the
U.S. population. Coastal recreation and tourism
generate 8 to 12 billion annually (5) In just
one estuarine system- Massachusetts and Cape Cod
Bays- commercial and recreational fishing
generate about 240 million per year. In that
same estuary, tourism and beach-going generate
1.5 billion per year, and shipping and marinas
generate 1.86 billion per year (3).
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Problems Facing Estuaries

• Nutrients have increased manyfold, causing
  harmful algal blooms and depletion of oxygen
  (hypoxia and anoxia)
• Intertidal and tidal habitats have been filled
  and dredged
• Landscape alterations, water diversions, damming
  of rivers
• Changes to amounts and seasonal patterns of
  freshwater and transported sediments sometimes
  too much sediment
• Overexploitation of natural resources (fisheries)
• Industrial pollution trace metals, PAHs, PCBs,
  etc.
• Invasive species and non-indigenous animals
  habitat change and loss, displacement of native
  species

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Estuaries Definition

• Estuary where river meets the ocean, and
  salinities vary from 35 ppt to lt5 ppt
• -substantial river inflow and influence not
  just a bay with a river flowing into it
• -are protected waters, no long period swell
• Classic estuaries are drowned river valleys where
  sediment inputs from the river and other sources
  cannot keep pace with sea level rise

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Estuarine Types Mixing

• Stratified where a large river dominates the
  system, adding a greater volume of water than the
  tide
• -essentially where river discharge (Q) gtthe
  tidal prism (TP)
• Tidal Prism the height of the tide from MW to
  HT
• -salt wedge highly stratified where river water
  overrides incoming saltwater, with the only
  mixing occurring at the interface. Potomac River,
  isohalines bend strongly at zone mixing
• Isohalines lines of equal salinity
• Partially mixed considerable river inflow, but
  tidal volume about the same. Q TP. Chesapeake
  Bay

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Estuary Types Mixing

• -isohalines bend gently upestuary, with not as
  great a difference in salinity with depth between
  surface and bottom
• Fully Mixed volume of saltwater from tides
  greater than river inflow. TPgtQ
• -mixing by strong tidal currents and waves
• -in Bay of Fundytidal currents do the mixing
• -in Delaware Bay, currents and wave
• -isohalines run straight up and down

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Estuary Types Tidal Height Changes

• Hypersynchronous bottom friction and shoreline
  convergence causes a loss of tidal energy
• -tide rises in amplitude, amplification, before
  falling at the mouth of the river. Bay of Fundy
• Synchronous essentially very little change in
  tidal amplitude upestuary, or very slow decline.
• -slow rise in the bottom, and gradual shoreline
  convergence. Chesapeake Bay
• Hyposynchronous very shrp decrease in amplitude
  upestuary from high bottom friction and shoreline
  convergence. Delaware Bay

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Estuarine Deposition Surface

• Flocculation small clay particles bound together
  by electrical attraction supplied by cations in
  seawater (Ca, Mg, Na)
• -generally occurs in mid-estuary,where neither
  river currents or tidal currents produce much
  turbulence
• -varies in spatial position by seasonal river
  flow
• -advection mass movement of sediment

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Estuarine Deposition Bottom

• Postma model
• -landward or seaward transport
• -bedload sand-size particles
• -ripples bigger and more widely spaced, the
  stronger the currrent
• -tidal flats often exposed, especially MLWS
• -contain burrowing organisms, like clams

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Estuarine Water Quality Assessment
Physical Chemical Sampling Biological -Dissolve
d Oxygen -Water Quality -Salinity -Habitat
Quality -pH -Benthic Organisms -Turbidity -
Planktonic -Water Temperature -Intertidal
-Stream Discharge -Fecal Bacteria