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The Problem With Estuaries

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

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The Problem With Estuaries

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  1. The Problem With Estuaries

  2. 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

  3. 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).

  4. 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

  5. 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 rise

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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

  11. Estuarine Water Quality Assessment 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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