Estuaries Definition

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					The Problem With Estuaries
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
           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).
      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
• 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
               Estuaries: Definition

•Estuary: where river meets the ocean, and salinities vary from 35
ppt to <5 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
          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) >the 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
           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. TP>Q
       -mixing by strong tidal currents and waves
       -in Bay of Fundy:tidal currents do the mixing
       -in Delaware Bay, currents and wave
       -isohalines run straight up and down
       Estuary Types: Tidal Height
•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
      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
      Estuarine Deposition: Bottom

•Postma model
       -landward or seaward transport
       -bedload: sand-size particles
       -ripples: bigger and more widely spaced, the stronger the
       -tidal flats: often exposed, especially MLWS
       -contain burrowing organisms, like clams
      Estuarine Water Quality
Physical & Chemical Sampling   Biological
-Dissolved Oxygen              -Water Quality
-Salinity                      -Habitat Quality
-pH                            -Benthic Organisms
-Turbidity                     -Planktonic “
-Water Temperature             -Intertidal   “
-Stream Discharge              -Fecal Bacteria

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