Hydrological Cycle

1
Hydrological Cycle
2
Estuaries

• Estuary semi-enclosed body of water where
  freshwater from land drainage dilutes sea water.
• Fresh ? Brackish ? Marine extent of salinity
  types varies with stream discharge, wave action,
  tidal action, evaporation, etc. - VARIABLE

3
(No Transcript)
4
Types of Estuaries
partially mixed
salt wedge
well mixed
fjord-type estuary with a sill
5
Estuary Substrates

• Substrates is estuaries usually are dominated by
  the sediment and FPOM transported by the stream
  input. (low tide may revel mud flats)
• Sedimentation may form
• a delta if tidal and wave
• action is low enough.
• Mississippi delta

6
Estuary Sides
STREAM-SIDE Stream Discharge Freshwater Higher
Turbidity (FPOM, DOM, Sediment)
OCEAN-SIDE Waves Tides Marine Water Lower
Turbidity (usually)
7
Drought, Floods, Tides

• Drought less freshwater estuary becomes more
  saline and less sediment w/ FPOM.
• High Tide more marine water estuary becomes
  more saline.
• Floods lots of freshwater estuary becomes
  much less saline and sediment with FPOM may be
  deposited less in the estuary itself (blown out
  of the estuary)
• Low Tide less marine water estuary becomes
  less saline.

8
In-Estuary Primary Production

• High turbidity often reduces (or eliminates)
  in-estuary submerged photosynthesis closer to the
  stream input.
• Salt-tolerant marginal emergent macrophytes
  undergoes significant production, especially in
  higher order streams. (e.g., Spartina)
• Periphyton (microphytes) may be able to undergo
  in-stream photosynthesis on the substrate (mud)
  surface (often at low tide).
• Phytoplankton often important in more protected
  estuaries and at the seaward side.

9
Allochthonous Inputs

• In most estuaries the most nutrients come from
  surrounding terrestrial environments via stream
  discharge (allochthonous materials)
• Most enters as FPOM or DOM. Limited CPOM, but
  some from surrounding emergent macrophytes.
• Detritivores and decomposers are very important
  in most estuaries.
• The flats (mud flats) of estuaries often are very
  productive.
• Deoxygenation of sediments often occurs.

10
Estuary Food Web
11
Salt Marsh
12
Salt Marsh(Protected Shallow Estuary with
Spartina)
13
(Tropical) Mangrove Swamp Estuary(Shallow
Estuary with Rhizophora)
14
Estuary Animals

• Freshwater Animals Most have a low
  salinity-range tolerance (stenohaline) and are
  restricted to the upper estuary (salinity lt7).
• Stenohaline Marine Animals have a low range of
  salinity tolerance are restricted to the outer
  estuary (salinity gt25).
• Euryhaline Marine Animals have a high range of
  salinity tolerance and are found in most of the
  estuary (salinity gt15).
• Estuarine Animals All have a wide range of
  salinity tolerance and many can inhabit much of
  the estuary (including hypersaline isolated
  areas). Most in salinity 5-18.

15
ChesepeakeBay Species OxygenTolerances
16
Human Impacts Development

• Low land in the estuary protected from flood or
  tidal inundation and developed.
• Increases sedimentation in channel, water
  velocity, and estuary cleaning of water before
  it reaches the ocean.
• Similar to stream
• channelization.

17
Human Impacts Barrages

• Barrages block tidal and other increased water
  flow from entering from seaward.
• -May protect from storm or flooding surges.
• -May keep water fresh for use locally.
• Increase sedimentation.
• Change to more freshwater environment.
• May prevent or impede spawning migrations.

18
Human Impacts Pollution

• Many human population centers are in or drain to
  estuaries (sewage and other pollution).
• Heavy metals in sediments are of concern.
• Estuaries can be nutrient overloaded. Red
  Tides and other algal blooms.