The Nature of the Estuary
Chesapeake Bay
The Nature of the Estuary
Captain John Smith
1608 charted shorelines
Meet Chesepiuc Indian tribe
Algonquin Indians
" Chesepiooc " great shellfish bay or great river
Most productive
1986 harvested - in the entire USA
20 % of oysters
50 % of blue crab and soft shell clams
200 million pounds of seafood annually
value of exceeding $ 100 million
no coastal fishery rival
only Atlantic and Pacific Oceans surpass the Bay
" Immense protein factory "
Size does not make it great
Other coastal regions are larger
Gulf Coast, New England states, Alaska
Special because
The Bays chemistry and mechanics
Estuary
Definition: is a semi-enclosed coastal body of water that has a measurable salinity gradient from its freshwater drainage to its ocean entrance.
The Chesapeake Bay qualifies as an estuary.
So does:
Delaware Bay to the north
Pamlico Sound to the south ( Outer Banks )
Cook Inlet in Alaska
Puget Sound the port of Seattle
Fjord
Most spectacular
Trondheims-fjord and Oslofjord in Norway
steep granite walls
deep blue water from the last ice age
Nova Scotia
ice carved Minas Basin off the Bay of Fundy
record tides
Newfoundland coast has estuary system - rugged
1,200 - foot valleys where northern ice sheet once roamed
Estuary Characteristics
Minimum criteria:
Daily tides
Seasonally variable flow and salinity
Two-layer circulation pattern:
salty deepwater layer that flows landward and a fresh surface layer travelling seaward that produces a net flow downstream.
Mixing is promoted by wind, friction and tides
850 such basins are found in the USA alone.
The Bays beauty
Subtle
Shoreline modest
Tides reserved
Sand, clay and water
not granite or ice
Its moderation is key to teeming productivity
Finely sloped and shallow waters
Sunlight: the beginning
Allows nurturing of rooted aquatic plants
marshlands are footholds along shorelines
plant life provides oxygen, detritus, habitats
unlike fjords, the Chesapeake Bay promotes life
Healthier estuaries
Because:
open aperture to the sea
tidal flushing is vigorous
promotes circulation of oxygen and nutrients within brackish water
receives influx of freshwater from several rivers
Rivers provide
Detritus
dissolved gases
nutrients
minerals
important for plant growth and dual food chain intrinsic to estuaries
high river flow drives estuarine circulation
yielding a net discharge towards the ocean
Sharing estuary assets
Along Atlantic seaboard
a number of freshwater tributaries
shallowness
low-lying wetlands
wide portal to the sea
The Bays " Greatness "
Historically
The Chesapeake Bay has been the greatest shell - and finfish bay in Northern America. Second to none.
Stressful Environment
Trademark of the Bay -
average depth 21 feetdouble edge sword
shallow water enhance aquatic growth
exposes to winds and temperature
Bay waters
colder in winter
warmer in summer
Transition zone - freshwater and marine species
limits efforts to spawn and feed
few residents, many seasonal visitors
A Stressful Environment continued
Temperature and salinity oscillations
Fluctuating conditions
unstable environment for organisms
for most plants and animals, residents or visitors, estuarine species- the Bay is a stressful place
seasonal
265 fish species summer months
29 resident endure winter months
Very few plant and animals can survive but the ones that do flourish in the Bay greater than anywhere else on Earth.
Estuarine Productivity
Organisms like:
grass shrimp, blue crab, soft-shelled clam, some killifishes, copepods, polychaete worms grow and multiply
create more biomass, than found acre for acre than in the open Atlantic ocean and coastal waters
connected to aquatic plant yield (base of food pyramid)
more plants - the greater the number of consumers
seafood industry, cultured and harvested for market
Estuarine Productivity continued
Powerhouse of photosynthetic activity:
Come from - Fresh, brackish and saltwater wetlands
phytoplankton, benthic algae, epiphytic algae, SAV
Salt marshes produce 10 tons of organic matter / acre each year
Most tonnage is consumed by wetland bacteria and higher animals
half of the crop is flushed by tidal action into shallow waters surrounding the marsh.
Compared to avg. yield of wheat (stems, leaves) = 1.5 tons/acre/yr.
Estuarine Productivity continued
Detritus consumed by aquatic organisms
some reclaimed by marsh on the next turn of the tide.
Salt marshes are highly productive
enormous quantities of nutrients flowing into the basin form land, riverine, wetland, tidal sources
Estuary out produces marine ecosystems
Open ocean phytoplankton production = 1/6 of an estuary's.
Coastal waters are the breadbasket of the Atlantic
the deep ocean is a desert
while inshore estuaries are very fertile supported by rich soil and fresh water
maybe as rich as a tropical forest
Nursery Grounds
An area where commercial fish species use to feed
they find few competitors, plenty of food
phytoplankton, marsh detritus, invertebrates
Anadromous species: herring, shad leave the ocean each spring
traverse the estuary and swim up freshwater rivers to spawn
return to the sea offspring matures and feed in the Bay
Semi-anadromous species
striped bass (rockfish) spawn in brackish water along Bay tributaries
Estuarine species
white perch live their entire life in the Bay
Marine species
croaker, menhaden
spawn in the Atlantic
larvae flow into the Bay by deep water currents
mature in juvenile and adults
Predators ( bluefish, marine carnivores)
enter the Bay to feed on these fish
Wetlands and Wildlife
Surrounding the Bay is 498,000 acres of emergent wetlands
shrub swamps, cattail marshes
find them along secluded stream and open salt marshes of the lower Bay
Natures purifiers
act like sponges
enhance water quality
provide hydrological benefits
reservoirs of productivity
habitats for crustaceans, fishes, reptiles, birds, mammals
flood control, ground water recharge
Wetland and Wildlife continued
Flocks of nesting birds very visible
shelter and food
Stop over for migratory waterfowl
" Atlantic flyway " a winter home
500,000 Canada geese
40,000 tundra swans
250,000 ducks
25 species
marsh ducks, bay ducks, sea ducks
All organism prefers its own piece of the Bay
Physical
Characteristics
Length 195 miles
Width 4 to 30 miles
Average Depth 21 feet
Greatest Depth 174 feet
Drainage Area 64,000 sq. miles
Wetlands 498,000 acres
Surface Area
Bay Proper 2,500 sq. miles
Bay and tributaries 4,400 sq. miles
Shoreline
Bay Proper 4,000 miles
Bay and tributaries 8,100 miles
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