Estuary Where the River meets the Sea

Importance:  Nursery Ground  Filters Pollutants  Absorbs excess Rainfall (run- off)  Nutrient Trap  Sediment Trap (captured in grasses)  Overwintering (resting) Stop for Birds

Mobile Bay:Bar-built  Barrier Island (Dauphin Island) protects bay from wave action  Mobile’s Delta- formed when sediments from upstream are deposited at the mouth of the river as it enters the bay.

Physical Characteristics  River flow slows as it enters bay & nutrient rich sediments fall out of suspension  Flushing- time it takes to move water out to the sea River flow, tides, wind & salinity gradient affected by time Nutrients, trash, young animals & detritus flushed

 Salt Wedge: Salinity is higher on the bottom waters of an estuary (NaCl more dense than fresh water) Water movement forms a wedge of high salinity water in the Estuary

Abiotic Environment of Estuary:  Nutrients: Phosphates, Nitrates, Sulfates from fresh water run-off Flocculation-nutrients dissolved in fresh water become insoluble in salt water and precipitate out, clouding the water BOD-Biochemical Oxygen Demand- high demand (low oxygen levels in water) when nutrients are too high

Abiotic Environment of Estuary  Sediment (benthos): Low oxygen levels or may even be ANAEROBIC in mud Salinity is relatively constant, about 30 ppt (Flushing doesn’t disturb the sediment)

 Benthic organisms: Oysters:  Need solid substrate to attach Mud suffocates oysters  Close shell & quits feeding when salinity drops…allowing bacteria to multiply in stomach…DANGEROUS to eat!

 Clams & Annelid worms Live buried in mud  Mussels Byssal Thread used to attach to solid substrate  Marsh Periwinkle Snails eats algae growing on grasses  Bacteria Decomposer Food source

Descriptions of Organisms:  Stenohaline-require constant salinity near 30 ppt  Euryhaline-adapt to changes in salinity  Osmoregulator-able to regulate osmotic balance.Ex. fish  Osmoconformer-unable to control osmotic flooding of tissues. Ex. Sea Anemone  Partial Osmoregulator- Crab

Estuarine Communities  Mudflats-exposed at low tide Diatoms give mud “golden” color No grasses (or very few!) Anaerobic Atmosphere- bacteria give off H2S (rotten) Provides shelter for clams & worms  Protects from sun (dessication)  Protection from predators  Provides constant salinity

 Wetlands-partially flooded by tides Saltmarsh- Temperate climate  Plants:Cord Grass (Spartina), Pickleweed (succulant)= halophytes  Bacteria- cyanobacteria= photosynthetic, nitrogen fixers  Animals- fiddler crabs, marsh snails

 Wetlands continued Mangrove- Tropical climate  Mangrove shrubs Prop roots & pneumatophores

 Subtidal- Seagrass Beds Always underwater Plants- Eel grass, Turtle grass  Habitat for young fish & larvae  Nutrient pump- takes nutrients from sediments for growth & later releases them into the water when they die  Trap sediments

Uses & Abuses of Estuaries  2/3 of Commercial fish spend some part of their life in an Estuary!  Pollution-75% Estuaries have been destroyed in USA!! Development Dredging Wastes Dumped Piers & Pilings altered flow of water

Food Chain in a Typical Estuary:  Primary Producers – Consumers –Detritivores – Planktivores - Carnivores

Mobile Bay Environmental Issues:  Gas Wells ~20 natural gas wells in Mobile Bay area Fear of leaks hurt tourism… now not within 15 miles of shore Artificial habitat for marine life

 Growth on Eastern Shore Population increased >50% in past 20 years  Sewage treatment facilities above capacity(>160 gal treated water added to Bay DAILY) Hypoxia caused by sewage in water….leads to fish kills  Sediment from building runs into Bay Suffocates grassbeds (habitat & natural filter)

 Biodiversity of Bay Alabama ranked #1 in N.America for number of fish species Alabama ranked #2 for number of extinct species…… due to dams and interference of water flow

 Pollution of Alabama Water DDT pesticide widely used in 1960’s, banned in 1972, caused death of Brown Pelican & ALL predatory birds AL is the 5 th MOST polluted state Heavy metals such as Mercury and toxic chemicals have BIOACCUMULATED in the fish Bay conditions monitored by Alabama Dept Enviromental Management (ADEM)

 Alabama has adopted the EPA’s MINIMUM Water quality standards!

Nonpoint Source Pollution  Source of pollutant can not be identified Drainage from surface runoff within a WATERSHED (all the land that contributes runoff to a given point)  Sediments,nutrients,chemicals (toxins), organic sewage