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Estuary:
- place where FW&SW-Usually a river mouth (espc in TX)
- Can have mixing: shallow, wind blown
- Stratification common: by temp and salitinity
- Salinity greater deeper
- Halocline:abrupt change in salinity
- Coriolus force: in large estuary, tides create higher water levels on 1 side
- Not seen in TX
- Better developed on Us east and gulf coasts than on West coast
- Biggest u.s. estuary is Chesapeake Bay
- San Francisco Bay-only big west coast estuary
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SALINITY in estuaries
- Can have mixing: shallow, wind blown
- In gulf, 28% is common
- Lower saline limit for estuaries water =7%, below is FW
- Gradual salinity change going seaward-if have mixed estuary
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Mixed estuary
Gradual salinity change
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Stratified estuary
- has salt wedge
- Area of salty water
- In drought salt wedge may go way up stream-blue crabs in Houston
- Flood-> goldfish in bay
- Tend to get seasonal changes: more Fresh water in winter, less in summer
- Isohaline line=area of similar salinity
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How to tolerate Salinity changes
- Move
- Seasonal reproductive cycles
- Dig into sediment
- osmoregulation
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Take advantage estuary salinity change
- Anadromous: salmon spawn in fresh water, grow up in Salt water
- C atadromous: spawn in slat water, grow up in freshwater ie AMERICAN eel
- River shrimp: Macrobrachium
- Many species that spawn in oceans/gulf but grow in bays and lower regions of estuaries
- Don't go up in to full freshwater, but do reproduce in salt water
- Blue crab, commerical shrimps
- Juveniles in bays, adults go out
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Osmoregulation in estuary fauna
- Some species just tolerate large salinity range
- Enteromorpha
- Osysters:Crassostrea; Osmoconformers
- True osmoregulators have excretory sytem (Kidneys)
- Excretion=> pump out liquid
- So NOT THROUGH ANUS; THROUGH kidneys, uretors etc
- Active transport involved (uses ATP)
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What happens in true osmoregulation?
- Water travels from area of higher concentration to area of less concentrations
- If outside water is salty, is less concentration
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Osmoregulation and Marine fish
- Hyposaline=lesser salinity= higher water
- Hypersaline=higher salinity
- Salt water
- Body fluids are lesser; SW is greater
- Drinks SW water likely to be lost excretes slats, retains water
- Fresh water
- Body fluids are greater
- Water likely to flow in
- => fish burst if doesn't excrete water
- Retains salts from food; gill glands retain salts
- Fish don't osmoregulate immediately
- Have to take time at each place to allow for switch
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Osmoregulation and Estuary fishes
- Some estuarine fishes that tolerate greater range of salinity: euryhaline
- Ie Molly fishes
- Stenohaline:
- Tolerates only a certain limit of salinities
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Euryhaline
Tolerate greater range of salinity
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Common conditions in estuary
- Usually muddy
- From salty area going upstream, more insects
- Intermediate parts of estuaries-insects are prime choice of for food
- Water is turbid
- High primary productivity
- Nutreints high
- Much detritus
- Export detritus-important food source
- How far goes-depends on how fast flow and how big river
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Texas
- In texas, fw input from rivers to bays is a major source of argument
- Fresh water ecosystmes move inland
- Cattail marsh moves first
- Not many woody plants (trees)
- Many species can't migrate to reproduce
- Many bay species are exposed to SW predators and parasites if salinity increases
- Ex Oyster
- Eaten by oyster drills (Stamonita)
- Murrex snail-glomps oysters
- Stone crab (Menippe)-don't pick up-can crush oyster shell=destroy fingers
- Parasite: vampire snail (Boonea); carries disease MBX
- Can have salt water invasion of coastal aquifers
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