Hydrological Cycle. 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. Types of Estuaries.
Fresh Brackish Marine – extent of salinity types varies with stream discharge, wave action, tidal action, evaporation, etc. - VARIABLE
fjord-type estuary with a sill
a delta if tidal and wave
action is low enough.
(FPOM, DOM, &
Waves & 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.
stream FPOM & DOC
collecting & grazing
some small fishes
& fish (juv.)
Fishes and Birds
Freshwater Animals – Most have a low salinity-range tolerance (stenohaline) and are restricted to the upper estuary (salinity <7).
Stenohaline Marine Animals –have a low range of salinity tolerance are restricted to the outer estuary (salinity >25).
Euryhaline Marine Animals –have a high range of salinity tolerance and are found in most of the estuary (salinity >15).
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.
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
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.
Change to more freshwater environment.
May prevent or impede spawning migrations.
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.