EstuariesEstuaries::

Where Where Rivers Meet Rivers Meet

the Seathe Sea

The Nature of an EstuaryThe Nature of an Estuary Collision of fresh Collision of fresh

river water flowing river water flowing seaward and ocean seaward and ocean water pushing water pushing inland.inland.

From the Latin verb From the Latin verb aestuareaestuare which which means “to heave, means “to heave, boil, surge, or be in boil, surge, or be in commotion”commotion”

Are All Estuaries the Are All Estuaries the Same?Same?

Common on Common on passive marginspassive margins of of continents.continents.

Four types:Four types: drowned river valleys (coastal plain drowned river valleys (coastal plain

estuaries)estuaries) bar-built bar-built tectonictectonic fjordsfjords

http://www.onr.navy.mil/focus/ocean/habitats/estuaries1.htm

Geologic History of our Geologic History of our Chesapeake BayChesapeake Bay

Only two river valleys, Only two river valleys, Susquehanna & James Susquehanna & James RiverRiver

These ancient river These ancient river channels today are channels today are shipping channels in the shipping channels in the Chesapeake Bay.Chesapeake Bay.

The two underwater The two underwater portions of the Chesapeake portions of the Chesapeake Bay Bridge-Tunnel are Bay Bridge-Tunnel are sunk into these ancient sunk into these ancient river valleys.river valleys.

500,000 years ago to 10,000 years 500,000 years ago to 10,000 years ago ago

Chesapeake Bay Bridge Tunnel

Geologic History of the Geologic History of the BayBay

10,000 years ago10,000 years ago Current Current interglacialinterglacial period begins. period begins. Glaciers and polar ice caps melt.Glaciers and polar ice caps melt. Sea level rises more than 325 feet Sea level rises more than 325 feet

backing up freshwater flowing from backing up freshwater flowing from Susquehanna and James at the Susquehanna and James at the mouth of the present bay.mouth of the present bay.

9,000 years ago9,000 years ago Head of the current bay had almost Head of the current bay had almost

reached Baltimore.reached Baltimore.

The Bay on the RiseThe Bay on the Rise

3,000 years ago3,000 years ago The Chesapeake Bay, as The Chesapeake Bay, as

we know, it had formed.we know, it had formed. Since then sediments Since then sediments

begun to fill it in begun to fill it in forcing the Bay upward forcing the Bay upward and outward.and outward.

As sea level continues As sea level continues to rise approximately 1-to rise approximately 1-3 mm each year, the 3 mm each year, the Bay continues to Bay continues to inundate its shoreline inundate its shoreline and continues to grow.and continues to grow.

Sharps Island, MD ca. 1950. This is all that remains of an island that 100 years before was nearly 600 acres.

Now the Sharps Island lighthouse (top) is the only thing that remains to mark its position

The Present Day BayThe Present Day Bay

The Bay is in a The Bay is in a dynamic statedynamic state, , ever changing ever changing due to global due to global climatic factors climatic factors as well as local as well as local physical factors.physical factors.

Physical Characteristics of Physical Characteristics of EstuariesEstuaries

The following factors are highly The following factors are highly variable in estuaries:variable in estuaries: SalinitySalinity Dissolved OxygenDissolved Oxygen Water level (tidal range)Water level (tidal range) TemperatureTemperature Light penetrationLight penetration

SalinitySalinity

Decreases as one moves upstream from ocean Decreases as one moves upstream from ocean to freshwater source.to freshwater source.

Denser seawater flows into the estuary along Denser seawater flows into the estuary along the bottom.the bottom.

Freshwater flows seaward along the surface.Freshwater flows seaward along the surface. Creates a Creates a salt wedgesalt wedge that moves back and that moves back and

forth and/or mixes according to other physical forth and/or mixes according to other physical factors.factors.

SalinitySalinity – – total amount of dissolved materials (salts) in total amount of dissolved materials (salts) in seawater. It is measured in parts per thousand (ppt).seawater. It is measured in parts per thousand (ppt).

SalinitySalinity – – total amount of dissolved materials (salts) in total amount of dissolved materials (salts) in seawater. It is measured in parts per thousand (ppt).seawater. It is measured in parts per thousand (ppt).

Different Mixing Patterns of Different Mixing Patterns of EstuariesEstuaries

Well-mixed

FjordSalt wedge

Partially mixed

Seasonal Salinity Seasonal Salinity VariationsVariations Lines of like salinity Lines of like salinity

can be represented can be represented with with isohalinesisohalines. . These form a picture These form a picture of increasing salinity of increasing salinity as one looks from as one looks from north to south.north to south.

SpringSpring – snow-melt – snow-melt and spring rains and spring rains wash into bay wash into bay pushing fresh pushing fresh isohalines southward.isohalines southward.

FallFall – summer heat – summer heat and less rainfall force and less rainfall force salty isohalines salty isohalines northward.northward.

Fig. 1-4: Salinity: Spring and Fall

TidesTides periodic rise and fall of the sea surfaceperiodic rise and fall of the sea surface caused by the gravitational pull of moon caused by the gravitational pull of moon

and sun and sun andand the rotation of the earth, the rotation of the earth, moon, and sun.moon, and sun.

http://www.oceanservice.noaa.gov/education/kits/tides/http://www.oceanservice.noaa.gov/education/kits/tides/ Castro text pp 56-61Castro text pp 56-61

Tidal EffectsTidal Effects Two high tides, two low tides every dayTwo high tides, two low tides every day Mixed semi-diurnal patternMixed semi-diurnal pattern

University of Florida, School of Natural Resources and the Environment, retrieved April 13, 2004.

But the Wind Will Have But the Wind Will Have Its WayIts Way

Prevailing winds disrupt the tidal pattern.Prevailing winds disrupt the tidal pattern.

NorthNorthwestwest winds push winds push water out the mouth of the water out the mouth of the estuary.estuary. Reduces the effect of high Reduces the effect of high

tides.tides. Accentuates the low tidesAccentuates the low tides

NorthNortheasteast winds pile water winds pile water up in sections of the bay.up in sections of the bay. High tides cause flooding of High tides cause flooding of

many low-lying shorelinesmany low-lying shorelines

Eastbound Pratt St. after Hurricane Isabel – Sept. 2003

Too Much Wind – Not a Good Too Much Wind – Not a Good ThingThing

Certain winds triggerCertain winds trigger seichingseiching, or , or sloshing, that forces water from the sloshing, that forces water from the eastern shore to the western shore.eastern shore to the western shore. Forces deeper oxygen-poor waters to Forces deeper oxygen-poor waters to

the surface of shallower areas.the surface of shallower areas.

““Blowin’ in the Wind”Blowin’ in the Wind” A story of winds, tides, and blue crabsA story of winds, tides, and blue crabs

Blue crabs hatch Blue crabs hatch near the mouth of near the mouth of the Bay.the Bay.

Helpless blue crabHelpless blue crab larvae, orlarvae, or zoeazoea, are , are at the mercy of at the mercy of winds and tides.winds and tides.

Larval crabs drift Larval crabs drift out to the Atlantic, out to the Atlantic, unless winds and unless winds and tides work at the tides work at the right time and in right time and in the right direction the right direction to bring them back to bring them back into the into the Chesapeake.Chesapeake.

DID YOU KNOW?

•The Chesapeake Bay accounts for over 50% of the nation’s annual blue crab production.

•75% of the adult blue crabs in the Chesapeake Bay are harvested each year.

DID YOU KNOW?

•The Chesapeake Bay accounts for over 50% of the nation’s annual blue crab production.

•75% of the adult blue crabs in the Chesapeake Bay are harvested each year.

Blue Crab Life CycleBlue Crab Life Cycle

Blue Crab Life CycleBlue Crab Life Cycle

Two Directions at OnceTwo Directions at OnceAs mentioned earlier…As mentioned earlier… Freshwater flows seaward on the Freshwater flows seaward on the

surface.surface. Salty water flows northward Salty water flows northward

underneath.underneath.

----------------------------------------------------------------------------------

Tides reverse these Tides reverse these flows temporarily, flows temporarily, but…but…

……the the netnet movement movement for particles at the for particles at the surface is south, surface is south, while particles near while particles near the bottom move the bottom move north.north.

Fig. 1-3: Mixing and Flows of Water in the Estuary

Coping with the ClassicsCoping with the Classics This two-layered flow is This two-layered flow is

termed termed “classic” bay “classic” bay circulationcirculation.. Susquehanna dominates flow in Susquehanna dominates flow in

north while ocean dominates in north while ocean dominates in south.south.

As a result, bay follows “classic” As a result, bay follows “classic” pattern, most often, but less than pattern, most often, but less than half of the time.half of the time.

Organisms, must cope with both Organisms, must cope with both the “classic” pattern and the the “classic” pattern and the uncertain perturbation that uncertain perturbation that occurs.occurs.

Ebb

Flood

N S

N S

Organisms swim up.

Carried south.

Organisms swim down.

Carried north.

Anadromous FishesAnadromous Fishes

Spend most of adult life in Spend most of adult life in oceansoceans

Migrate to freshwater to Migrate to freshwater to breedbreed

Young fry often rear in Young fry often rear in estuariesestuaries

Include:Include: ShadsShads HerringsHerrings Salmon (on Pacific Coast)Salmon (on Pacific Coast)

Catadromous Catadromous FishesFishes

Spend adult Spend adult life in life in freshwater.freshwater.

Migrate to Migrate to saltwater to saltwater to breedbreed

Include:Include: American eelsAmerican eels Chinese Chinese

Mitten crabs Mitten crabs (invasive species in (invasive species in Bay)Bay)

Life Cycle of the American EelLife Cycle of the American Eel

If You Farm the Bay, Pray for If You Farm the Bay, Pray for Drought…Drought…

Nutrient Inputs in Wet vs. Nutrient Inputs in Wet vs. Dry YearsDry Years

Fig. 1-5: Wet and Dry Years Affect Bay Pollution

In For the Long HaulIn For the Long Haul Because bay recovery is so affected by wet and Because bay recovery is so affected by wet and

dry years, it requires long-term monitoring to dry years, it requires long-term monitoring to establish a establish a baselinebaseline – or average – condition. – or average – condition.

Fig 1.6: Historic Variations in the Bay’s Freshwater Stream flow

Low Freshwater FlowLow Freshwater Flow If the bay were drained If the bay were drained

and the ocean stopped, and the ocean stopped, rivers would have to run rivers would have to run for 6 months to fill the bayfor 6 months to fill the bay..

This small input, This small input, energizes the energizes the system and in system and in essence creates essence creates the bay’s the bay’s circulation and its circulation and its capacity for capacity for productivityproductivity..

Rich With Life – Despite the Rich With Life – Despite the OddsOdds

Why, with all the stress to the system, is Why, with all the stress to the system, is this tiny bay so rich with life?this tiny bay so rich with life?

Consider the following statistics:Consider the following statistics:

The Bay produces:The Bay produces:100 million pounds of seafood each year. (400 million if you count menhaden)50% of nation’s blue crabs90% of nation’s soft crabs15% of nation’s oysters70% of the spawning grounds for striped bass $678 billion to the economies of MD and VA alone.

The Bay produces:The Bay produces:100 million pounds of seafood each year. (400 million if you count menhaden)50% of nation’s blue crabs90% of nation’s soft crabs15% of nation’s oysters70% of the spawning grounds for striped bass $678 billion to the economies of MD and VA alone.

The Answer to the Bay’s The Answer to the Bay’s ProductivityProductivity

Scientists compare primary Scientists compare primary production – the production of production – the production of ‘plant life.’‘plant life.’

Forms the foundation of the Forms the foundation of the food chain – allows bay to food chain – allows bay to support a high fish support a high fish production.production.

The reason:The reason: You can touch You can touch bottom almost everywhere!bottom almost everywhere!

Top: Bernie Fowler Top: Bernie Fowler wades into the wades into the Patuxent. Right: Patuxent. Right: 2000 Patuxent 2000 Patuxent Wade-In.Wade-In.

Shallowness PaysShallowness Pays Even though the bay is large, all the water Even though the bay is large, all the water

is spread very thin – average depth is 21 is spread very thin – average depth is 21 feet -- well within thefeet -- well within the photic zonephotic zone..

This allows phytoplankton andThis allows phytoplankton and submerged submerged aquatic vegetation (SAVs)aquatic vegetation (SAVs) to flourish.to flourish.

Chesapeake Bay – Original Chesapeake Bay – Original RecyclerRecycler

The bay is adapted to do more with less.The bay is adapted to do more with less.

Phytoplankton absorb Phytoplankton absorb nutrientsnutrientsPhytoplankton absorb Phytoplankton absorb nutrientsnutrients

Nutrients re-enter water.Nutrients re-enter water.Nutrients re-enter water.Nutrients re-enter water.

Bacteria decompose Bacteria decompose phytoplankton remains.phytoplankton remains.Bacteria decompose Bacteria decompose phytoplankton remains.phytoplankton remains.

Phytoplankton die or are Phytoplankton die or are consumed – remains fall consumed – remains fall to bay floor.to bay floor.

Phytoplankton die or are Phytoplankton die or are consumed – remains fall consumed – remains fall to bay floor.to bay floor.

..But it Cannot Do Less ..But it Cannot Do Less with Morewith More

EutrophicationEutrophication – excess nutrient – excess nutrient build-up in an ecosystem.build-up in an ecosystem.

What are some contributing factors What are some contributing factors to eutrophication in the Chesapeake to eutrophication in the Chesapeake Bay?Bay?

How is the bay itself prevented from How is the bay itself prevented from reversing this eutrophication?reversing this eutrophication?

What can be done to stop this What can be done to stop this problem?problem?

Nutrient PollutionNutrient Pollution Natural sources of nutrientsNatural sources of nutrients

wastes from Bay organismswastes from Bay organisms death and decay of organisms in the Baydeath and decay of organisms in the Bay ““natural” run-off from landnatural” run-off from land

Human affected sources of nutrientsHuman affected sources of nutrients Point source pollutantsPoint source pollutants

sewage outfallssewage outfalls industrial outfallsindustrial outfalls stormwater run-offstormwater run-off

Non-point source pollutantsNon-point source pollutants fertilizers fertilizers excess sediment run-off excess sediment run-off pet wastespet wastes

Natural sources of nutrientsNatural sources of nutrients wastes from Bay organismswastes from Bay organisms death and decay of organisms in the Baydeath and decay of organisms in the Bay ““natural” run-off from landnatural” run-off from land

Human affected sources of nutrientsHuman affected sources of nutrients Point source pollutantsPoint source pollutants

sewage outfallssewage outfalls industrial outfallsindustrial outfalls stormwater run-offstormwater run-off

Non-point source pollutantsNon-point source pollutants fertilizers fertilizers excess sediment run-off excess sediment run-off pet wastespet wastes

point source

Work CitedWork CitedSkagit Valley College, "Anadromous Life Cycle." 2006. Skagit Valley College. Skagit Valley College, "Anadromous Life Cycle." 2006. Skagit Valley College.

11 Sep 2007 <http://www.skagit.edu/news3.asp_Q_pagenumber_E_1978>. 11 Sep 2007 <http://www.skagit.edu/news3.asp_Q_pagenumber_E_1978>.

Pacific Northwest Fisheries Program, "Kid's Corner, Fish & Life Cycles." Pacific Northwest Fisheries Program, "Kid's Corner, Fish & Life Cycles." PNFC, USDAPNFC, USDA. Pacific Northwest Fisheries Program. 11 Sep 2007 . Pacific Northwest Fisheries Program. 11 Sep 2007 <http://www.fs.fed.us/r6/fishing/regional/enveducation/kidscorn-<http://www.fs.fed.us/r6/fishing/regional/enveducation/kidscorn-fish.html>. fish.html>.

Jessop, B.M.. "American Eel." Jessop, B.M.. "American Eel." Underwater WorldUnderwater World. 2006. Fisheries and Oceans . 2006. Fisheries and Oceans Canada. 11 Sep 2007 <http://www.dfo-mpo.gc.ca/zone/underwater_sous-Canada. 11 Sep 2007 <http://www.dfo-mpo.gc.ca/zone/underwater_sous-marin/american_eel/eel-anguille_e.htm>. marin/american_eel/eel-anguille_e.htm>.

http://www.nativefish.org/articles/Migratory_Fish_Restoration.phphttp://www.nativefish.org/articles/Migratory_Fish_Restoration.php