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The Nature of the Estuary

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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 Bay’s 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 Bay’s beauty

Subtle

Shoreline modest

Tides reserved

Sand, clay and water

not granite or ice

It’s 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 Bay’s " 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 feet

double 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

Nature’s 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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