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Unformatted text preview: Estuaries
Where the river meets the ocean • An estuary is defined as a semienclosed coastal body of water in
which the ocean water is significantly
diluted by freshwater from rivers or
• Estuaries are important for
commerce & recreation and are
highly productive in a biological
• Important as fishery nursery
areas. • Estuaries have Four different types
of salinity distributions depending
on their topography and their inputs
of salt and freshwater.
• Vertically-mixed estuary.
• Slightly stratified estuary.
• Salt Wedge Estuary.
• Fjord Estuary. Vertically mixed estuary. These are shallow-low volume estuaries in which
the vertical distribution of salinity is uniform . Have strong tidal mixing
with low river flow. Chesapeake & Delaware Bay are examples. Note - in estuaries in the N.
Hemisphere the saltier
water is deflected to the
right due to the Coriolis
force. Chesapeake Bay is
an example. Slightly stratified estuary. A shallow estuary in which salinity
increases from the head to the mouth. There is a less saline upper
layer and a salty lower layer. Strong seaward flow of freshwater
and strong inflow of seawater at depth. Example is San
Francisco Bay & Puget Sound Salt wedge estuary. A salty wedge of water intrudes from the
ocean below that of the river water. The surface water is
essentially fresh and there is a high volume of freshwater flow.
Columbia, Hudson & Mississippi River estuaries. Columbia
estuary is a
estuary. In a Fjord-like estuary usually there is a sill at the mouth and
anoxic (no oxygen), denser salty water builds up in the
estuary behind the sill. Lots of organic matter falls from the
surface to deep water and bacteria in deep water respire
and use up the oxygen. Fjords are common in New Zealand
and Norway. In some estuaries, especially long
narrow ones, the flooding tide
creates a tidal bore that rushes in
tidal The Tidal Bore (Pororoca) on the
Amazon can be surfed.
Amazon Filming for Nissan commercial Record surfing for Pororoca is 37
minutes and 12.5 km. Occurs
February & March
February Occur when water flow is low and spring tides occur
Biggest is “Silver Dragon” on Qiantang River in China (29ft high) (Right) Some estuaries have extremes in
tidal ranges and others very little
tidal Bay of Fundy • Estuaries are highly productive. Nutrients run off
from the land and are plentiful. Phytoplankton grow
rapidly but the water is often turbid from sediment
runoff from the land , and light availability often limits
• Currents mix the nutrients up from the bottom and
this stimulates productivity.
• Benthic organisms are often plentiful, and deposit
and suspension feeders eat phytoplankton that drop
out of the water column and drop to the bottom.
• It is not unusual for the suspension feeders to filter the
entire water content of the estuary in a few days.
Oysters, mussels and barnacles are very abundant in
estuaries. Estuarine organisms
must be able to
changes in salinity.
You see a gradient in
species going from
upstream to brackish
water species (able to
tolerate large salinity
changes) in the middle,
to marine species at
the mouth. Most organisms must osmoregulate the salinity of
their bodily fluids. They keep their body’s salt
content fixed, no matter what the surrounding salt
level Organisms that can tolerate a wide range of salinities are EURYHALINE Those that can only tolerate a narrow range are STENOHALINE. These usually live at the upper (near freshwater) or lower (near the ocean) regions of the estuary Some organisms such as many molluscs and polychaetes don’t osmoregulate, and their body fluids conforms to the ambient salinity. They are called OSMOCONFORMERS Let’s Review
Let’s Bony fishes in the sea have a blood salinity about one third that of seawater. They drink seawater constantly, and release salts from their gills and also through their urine and feces, and they retain the lower salinity water How do salmon do it?
How Salmon in freshwater (left) and salmon in seawater (right)
To offset the dehydrating effects of salt water, the salmon drinks copiously (several liters per day), but in fresh water (where water loading is the problem) the salmon doesn't drink at all. The only water it consumes is that which necessarily goes down its gullet when it feeds. Kidney function also differs between the two habitats. In fresh water, the salmon's kidneys produce large volumes of dilute urine (to cope with all of the water that's diffusing into the salmon's body fluids), while in the ocean environment, the kidneys' urine production rates drop dramatically and the urine is as concentrated as the kidneys can make it. The result of this is that the salmon is using relatively little water to get rid of all of the excess ions it can (due to structural and functional limitations, the salmon's kidney cannot make its urine anywhere near as concentrated as humans can, but they do their best).
In freshwater salmon gills also pump sodium (Na) & chloride (Cl )INTO the salmon’s blood and do the opposite in seawater. The estuarine ecosystem is
complicated (next slide)
complicated Note the role played by both detrital material and benthic invertebrates. Compare this food web with that offshore. In open ocean food webs detritus and benthic invertebrates are insignificant Detritus again occupies a central
role in estuarine food web
role Another characteristic of the estuarine food web is
that benthic organisms are important consumers.
important Estuaries are important “nurseries” and especially on the US east coast.
Typically fish or crustaceans spawn offshore. Next, the larvae swim to the
estuary and reside there for months or years where they develop and feed on
abundant food. After they are more mature they swim back to the open ocean.
Examples are almost every commercial species on the east coast...shrimp,
redfish, winter flounder, and menhaden.
On the west coast what fish use estuaries as nurseries? Menhaden Shrimp • Striped Bass migrate from the Ocean to freshwater
like salmon, but the larvae and juveniles live for long
periods as they mature before they swim back to sea.
• Blue Crab adults also live in estuaries but spawn
offshore. Herring in San Francisco Bay
Herring Herring spawn Dec
March in SF Bay in lower portions of the Bay. They lay eggs mostly in upper 10 ft of water and eggs attach to rocks, wood, macroalgae etc. Herring are caught in gill nets in SF
Bay Herring roe (ovaries) are shipped to Japan and they are called KAZUNOKO and eaten as a delicacy Estuaries are very vulnerable to
disruption of their ecosystems from…
• invasive species
• runoff from streets & agricultural areas.
• Industrial pollution, oil spills etc.
** A very large percentage of the US population
lives along the coasts and especially near
estuaries. Think of Boston, New York, Baltimore,
San Francisco, Seattle, etc. Because of the large
population, this puts even more stress on
estuaries. The high population in estuarine areas
results in sewage and agricultural runoff
results The nutrient input to estuaries promotes growth of phytoplankton and macroalgae. When these die, they drop to the bottom and decompose and this results in oxygen depletion in deep waters Distance from mouth of bay Km. Chesapeake Bay : comparison of dissolved oxygen levels in 1950
and 1980. In 1980 regions that are darker blue are anoxic. The Bay ecosystem consists of Suisun Bay, South Bay,
80,000 acre Suisun Marsh (purple) and the Delta
80,000 Each area is Unique
Lower salinity Upstream & Higher down
stream The Freshwater source for the Bay is primarily the
Sacramento and the San Joaquin Rivers
The Bay drains
Half of the state
These rivers provides 70% of
CA drinking water
& irrigates 4.5 million
acres In the Delta, levees keep Bay water
out of low lying land
out A break in the levee would flood low lying lands and suck seawater upstream, killing organisms that can’t tolerate higher salinities The Delta has 1700 km (1054 mi) of earthen levees.
Breaks from an Earthquake could make destruction caused
by Hurricane Katrina look tame
by Levees keep the water out of the farmland which has shrunk in height by up to 8 meters. If Levees collapse then 2.5 billion m 3 of seawater would be sucked in. This would shut down the pumps that carry Delta water to farmers & SoCal. Many organisms that can’t adjust to salt water would die Complex water system
Complex Water is pumped From Delta
To Southern Cal
Aqueduct Much water drained from SF Bay. The two right & left lines
bring drinking water. Delta Mendota Canal is for agriculture
and California Aqueduct brings water to So Cal
and Bay Area Problems
Bay Introduced nonnative species Selenium Methyl Mercury Dioxins PBDE Selenium
Selenium is a naturally occurring element in the Central Valley When farmers irrigate their crops, the selenium dissolves into the water and then drains into streams which run into the Bay. Selenium is an essential element for diets, but the problem is that there is just a small window between the required concentration and the toxic concentration Selenium is an element which primarily
enters the Bay from the San Joaquin River.
Oil refineries also add selenium
Oil Selenium causes deaths or birth deformities in fish and birds
The San Luis Drain (closed at moment) pipes selenium away from farmland which has high selenium and into the Bay. The three scenarios are for 3 different selenium releases from the farmland The Sacramento Splittail is a small
fish that lives in the Delta
– Exposure to selenium (Se) at naturally occurring concentration of Se causes birth defects and increased mortality
– Effects are also seen in White Sturgeon Polybrominated Diphenyl Ether
PBDE PBDE is a flame retardant which are added to clothing, furniture, bedding, carpets, electronics and to plastics etc. Concentrations of PBDE in Bay Area humans and wildlife are highest in world. Bind to fat and can accumulate as they move higher up food chain PBDE concentrations in human breast milk
in Stockholm Sweden (where it was first
discovered as a contaminant)
discovered PBDE concentrations doubled every 5 yrs from 1972 to 1997 In SF Bay Harbor Seal PBDE has
doubled every 1.8 yrs from 1989-1998
– Halibut and Striped Bass PBDE doubled between 1997 – 2003
– PBDEs have been found to affect neurological development, thyroid hormone levels and immune function in laboratory animals Other effects
Early life exposure results in permanent changes in reproductive organs such as reduced sperm count and changes in ovaries Highest PBDE concentrations found in lower South Bay(103513 pg/L) Average concentration in US women is 90 ng/g Concentrations in California women are 310X higher than women from other parts of the world PBDEs currently do not have any
water quality guidelines
California in 2003 banned use of PentaBDE and OctaBDE and they were phased out in 2006. However they will leach into the environment for years to come DecaBDE was exempted from the ban because it breaks down in the environment BUT nobody knows much about how toxic the breakdown products are PBDE in US women
PBDE Reason for concern “Californians for Fire Safety” is an industry group
which has been placing ads to try to stop
legislation to restrict use of retardants
legislation Looks like everything is ready to blow up if they are banned Joke is that your generation will be
fire Sick joke, as there are serious side effects 2009 NSF funded summer research
program for undergraduates trough SFSU
Biology On a field trip on the Bay we used an “Otter Trawl” to collect fish and invertebrates Every one of the flounders we
caught had tumors
caught Possibly from toxic cancercausing chemicals in the sediments Mercury contamination of sediments resulted mainly from
gold miners who used mercury to extract gold. It also
comes from burning coal in power plants
comes Mercury exists in 3 States, elemental, di
valent, or methyl
The latter is highly toxic
because it can easily
Move across cell membranes Gold was mined with huge water
hoses Mercury was then added to the sluice way (left) to concentrate the gold Mercury Entered SF Bay Methylmercury affects neurobiology
Methylmercury The Mad Hatter in Alice in Wonderland was mad (crazy) because mercury was used in hat production and this affected the hatter’s brains. Methylmercury is a serious problem
in the Bay
in 74% of the Bay’s sediments have concentrations higher that the limit of 0.2 mg/kg. The threshold for human health is 0.3 ug/g in fish Striped Bass in the Bay have about 0.4 ug/g and Leopard Sharks 0.8 ug/g Dioxin & PCBs
Dioxin PCBs used in electrical insulators Dioxins are hundreds of different chemicals. Formed in paper manufacturing, waste incineration and pesticide manufacturing. These are among the most toxic chemicals known. Dioxins were also sprayed on Vietnam by the US to kill foliage Dioxins are present in SF Bay fish.
Don’t eat fish from the Bay.
Don’t Vegans have lowest Dioxin contamination (TEQ = toxic equivalents of dioxins). Viktor Yushchenko (Ukranian
President) poisoned with dioxins
after eating dinner with a Russian
after Level was 6000X normal Second highest concentration in history Exposure of fish to minute quantities (30 parts per
trillion) of dioxins leads to birth defects
trillion) PCBs can cause cancer in lab
– The threshold level in sport fish is 20 ng/g of fish
– In SF Bay, two sport fish examined (Shiner surfperch & White croaker) exceeded the limit by 100X and 130X Invasive species
Invasive San Francisco Bay has hundreds of non native species.
Let’s look at the effects of a few of them
The Green Crab was introduced to SF Bay from Europe. Blue is native home, red is invaded area, green is area potentially invaded in future Effects?
Effects? Has reduced abundances of over 20 invertebrate species in SF Bay Native clam (Nutricola) and shore crabs have decreased 510 fold Invasive copepod (Limnoithona
tetraspina) from China first seen in
SF Bay 1993
SF Today in the low salinity zone it makes up over 95% of total adult copepod population. Size is very small (0.5 mm) and it has displaced the larger (3 mm) native species Thus much less food for native fish such as Delta smelt because it is so small they can’t see it. Asian clam introduced 1987
Asian Potamocorbula amurensis spread throughout the northernSan Francisco estuary in 1987, causing substantial effects on the plankton. Chlorophyll concentration since the introduction of P. amurensis is about 5fold lower than before, and the springsummer blooms that characterized Suisun Bay have since been absent. Several zooplanktonic species, including three species of copepod and the mysid shrimp Neomysis mercedis, declined sharply in abundance and in spatial extent following the spread of the clam. These effects on the base of the food web were expected to have a major influence on fish and other consumers. Yet, the numerical response of most species of fish has been weak or nonexistent. This apparent lack of response is probably due to the availability of alternative food supplies, spatial and temporal mismatches between the fish and the effects of P. amurensis, and the open connections between estuarine waters and waters unaffected by the clam, either landward or seaward of the affected region. Clam effects
Clam Clam abundance exceeds 2000/m2 Since its appearance the summer diatom bloom has disappeared Can filter entire water column 1x/day Shallows 13X/day Rate of filtration exceeds growth rate of phytoplankton and bacteria WETLANDS
• Wetlands are low lying coastal areas that are
intermittently submerged by salt water. They have
sediments with little or no oxygen.
• They consist of Salt Marshes and Mangrove Swamps.
Both plants survive in these salty areas by selectively
excreting the salt that is in the water that they take up in
their roots. SALT MARSHES
Marshes are inhabited by grasses that are able to
tolerate saline water. • Salt marshes are very important to fish because
they also serve as nursery areas for many
species. About half the species of commercial
fish in the SE USA live at some time in their life in
• Salt marshes are among the most productive
ecosystems in the world and equal that of
• The daily tidal flushing brings in new nutrients
for the plants and stimulates their growth.
• There is abundant sun.
•Marshes need a barrier to protect from wave
action. Primary productivity in salt marshes
exceeds that in tropical rainforests
exceeds Spartina (cordgrass) is the main
plant in marshes and it is able to
tolerate the anaerobic (no oxygen)
sediments by being able to pump
oxygen down into its root/rhizome
• N2 fixation by symbiotic
bacteria living in the root
system provides nitrogenous
nutrients to the plants. There is typically a zonation of plants in
a marsh based on salt tolerance and
height above sea level
height On the east coast we see Spartina alterniflora at lowest level Above that is Spartina patens Higher up are plants such as Pickle weed (Salicornia) On the west coast we see Spartina foliosa nearest the water followed by Pickle weed higher up East coast S. alterniflora has
invaded SF Bay (red)
invaded The invasive species colonizes
mudflats, which are needed by
shorebirds for feeding
shorebirds Geese won’t eat it because it is tougher to pull and chew Eradication is underway by spraying and digging it out Wading shore birds use the mudflats
for feeding. They can’t if the mud is
covered with Spartina
covered Their bill length and shape reflects their prey depth Spartina has salt glands which extracts
the salt and excretes it from its leaves
the The remaining fresher water is then used in metabolic activities. It can live in saltwater almost twice the salinity of seawater. Shown is another salt tolerant plant. Note the salt crystals. Pickleweed doesn’t have salt
glands to excrete salt
glands It stores the salt in vacuoles within cells. When the vacuole gets too big it ruptures and the cell dies Spartina has flowers and seeds but
mainly spreads and reproduces
through its rhizomes
through The rhizome grows horizontally in the mud and sends out new shoots Salt Marshes of the SE USA have
recently experienced massive die-offs
recently Yellow are areas of “brown marsh in Louisiana It was thought that intense drought
was primary cause
was This is a factor However another major contributing factor is the Periwinkle snail
Grazes on Spartina and eats fungi, but as their radula scrapes the plant it opens the Spartina to infection from the fungus causing plant death • Marshes have abundant animals such as
Fiddler Crabs which hide in sediment holes at
high tide to escape predators then at low tide
they come out to feed. The male fiddler crab has one big
claw which can comprise 30% of
his body weight
his He must use the small claw for feeding and this means it takes longer for him to eat. Why have such a large claw? The claw is used for attracting
females for sex plus fighting with
other When a male waves its claw high, this attracts females. The bigger the claw, the greater the attraction! Why? Because usually the bigger the claw, the stronger and healthier the male and this should produce healthy and strong offspring If a male loses a claw in fighting, he
is in trouble….can’t mate or defend
himself The male will quickly grow a new “phony” claw The new claw is big so it can attract a female but it lacks muscles and would be poor in a fight. However, the new claw can attract females! • Other animals are ghost crabs, mussels, snails,
clams and many birds (clapper rail below). • Almost nothing eats Spartina when it is alive.
When it dies in the autumn it falls and bacteria
cover its surfaces and it breaks down into little
pieces. This detrital material is then eaten by
marsh animals and the bacteria provide extra
nutrients for those who consume the detritus. MANGROVES
• Mangroves occur in tropical areas. (Spartina can also
live in the tropics.) Mangroves need just the right
combination of tide, soil, low wave action and chemistry
to live. It is a spindly woody plant which provides a highly
productive habitat for other organisms. • The large root network provides hiding places
for crabs and fish and shellfish attach to the
• It constantly drops its leaves through the year
thus enriching the organisms living near it. These
leaves become detritus and are eaten by detritus
• The mangrove roots get oxygen by roots that
extend out of the sediment and water. These
roots conduct oxygen to the deeper roots.
• Mangrove ecosystems are being destroyed by
developers. This promotes erosion and destroys
the productivity of this productive ecosystem. In Summary, Wetlands and Estuaries are important as
spawning and nursery areas for fish and as habitat for
other organisms such as migrating birds, marine mammals
etc. These are nutrient rich and productive areas and as much as possible should be saved from developers
Also, it is clear that the Bay and its organisms are highly contaminated
Invasive species Study Guide
Study Know definition of estuary
Four different types of salinity distribution in estuaries
Type of estuary that has a tidal bore
What usually limits phytoplankton productivity in an estuary?
Benthic feeding types in an estuary
Euryhaline, Stenohaline, Osmoconformers
How do fish regulate blood salt content in ocean vs in freshwater
Importance of detritus in an estuary food web
Estuaries as nurseries for young of what organisms
What is Kazunoko
What are the two main freshwater sources for SF Bay More
Why are the Bay levees so important. What happens in they break? How does So. Cal get freshwater? Know about Selenium, Methyl Mercury, Dioxins & PBDE, sources and effects How does salt marsh productivity compare with rainforests? How does Spartina enter the estuarine food web? Invasive Spartina effects Fiddler crabs: why one big claw? Mangrove distribution and ecology That’s all!
That’s Worldwide Mangrove distribution
Worldwide Mangrove seeds actually germinate while on the tree so
that they are ready to penetrate sediments as soon as they
drop from the tree
drop Mangrove breathing roots
(pneumatophores) allow O2 to be
pumped down to roots.
Pneumatophores The mangrove ecosystem ...
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This note was uploaded on 11/07/2011 for the course BIO 160 taught by Professor Dr.jonstern during the Fall '08 term at S.F. State.
- Fall '08