Seawater
Lecture 2: Marine Biology (Honors)
England/Brown
1
What is it?
Seawater is …..
- 96.5% Water.
- 3.5% Dissolved solids.
2
What are the dissolved solids?
Na+, Cl-, K+, Ca2+, Silica, H2SO4,
OH-, and many Trace
Elements.
The Measure of these dissolved
solids in seawater is called
Salinity.
3
Salinity
Salinity is measured in parts
per thousand (ppt or 0/00).
What is the salinity of the
Oceans (i.e. Atlantic)?
- 35 0/00 (or 3.5 %).
Is the salinity of Long Island
Sound more or less?
- 26 0/00 to 28 0/00.
4
5
What causes salinity to Change?
1. River Runoff
- Add Freshwater,
decrease
salinity.
- Connecticut,
Housatonic, Thames
Rivers.
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2. Precipitation
- Add Freshwater,
decrease
salinity.
- Snow, Rain, etc..
7
What causes salinity to Change? (con’t)
3. Evaporation
- Water evaporates,
leaves salts.
- Remove freshwater,
increases salinity.
4. Freezing/Thawing of Sea Ice
- Water freezes, salts
remain.
- Freeze increase salinity
- Thaw decrease salinity.
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9
How does Salinity Affect Water
Temperature?
1. Freezing Point
At what temperature does freshwater freeze?
Pure freshwater freezes at 0 degrees Celsius.
How does salinity affect?
-Salinity makes freezing point go down.
-Seawater of 35 0/00 freezes at -1.91 C.
We rarely see saltwater freeze due to temperature and
currents pushing water around.
Sea Ice
10
Let’s try a Multi-flow Map
• Use the information you’ve learned so far in
this lecture to make your multi-flow map.
Affects
Salinity
How does Salinity Affect Water
Density?
2. Density
How does salinity affect density?
-Saltwater has more mass, so density increases.
So/and…..
- Since saltwater is more dense, it will sink
below freshwater.
This is related to another property, Buoyancy, which
will be discussed in a later lecture.
More Multi-flow maps
• Make a multi-flow map for the last slide
(expand to 4 boxes) –
Water
Density
H
How does Salinity Affect Water
Pressure?
3. Vapor Pressure
-Vapor Pressure is the pressure
exerted on a liquid surface from
the liquids own gas. Resistance
to evaporation.
- Equilibrium – balance and
stability
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- Saltwater will increase Vapor
Pressure, so salty water is more
difficult to evaporate than
Multi-flow map time…
• Make a multi-flow map for the last slide- How
does density affect water pressure
(expand to 4 boxes)
Water
Pressure
Affect of Salinity on Water Layers
Remember, more
salt causes water to
be more dense,
dense water sinks
below less dense.
If conditions are
right, water will
layer.
Halocline: gradients
of salinity
22
Affect of Temperature on Water Layers
Remember, colder
temp. causes water
to be more dense,
dense water sinks
below less dense.
If conditions are
right, water will
layer.
Thermocline
23
Affects of Density on Water Layers
The combination of
salt and temp will
change density, but
dense water
always sinks below
less dense.
If conditions are
right, water will
layer.
Pycnocline: gradient
in density (temp. and
salinity)
25
One more time…
• Make a multi-flow map using the information
from the last 3 slide (last one for today )
Water Layers
Gases in the Water
Question: What are the two important gasses in
the water?
- Oxygen (O2) and
Carbon Dioxide (CO2)
How do they get there?
Oxygen
1) Photosynthesis
2) Aeration and
Diffusion
Carbon Dioxide
1) Respiration
2) Aeration and
Diffusion
The Oxygen (-Carbon) Cycle
12
Affect of Temperature on Gases in
Water
What can affect the amount of dissolved gas in
water? - Temperature
Demo: You have a Warm
Soda, Cold Soda. Both
are opened. Which
fizzes more? - Warm can.
13
So….what holds more gas? Warm Water or Cold
Water?
- Increasing Temperature
decreases water’s ability to
hold gases.
Affect of Other Dissolved Gases
Acids (H+) and Bases (OH-).
H2O (Water)  H+ (hydrogen) + OH- (Hydroxide)
Review: What is the amount of hydrogen (hydroxides)
measure called?
pH
Review: What is the Range?
1.0 - >7 is Acid,
7.0 is Neutral,
>7 – 14.0 is Base.
Normal pH of Seawater is steady between 7.8 and 8.2.
Why is pH steady?
Seawater is resistant to changes in pH due to the
Buffering action of specific chemicals.
What does the term buffer (pH) mean?
The nature of a mixture of compounds that react in
such a way, that the pH resists sudden changes. Add
or remove H+ and/or OH- when need.
What chemical is responsible for this action?
(Hint: not O2)
CO2
Seawater rarely swings past a pH of 7.5 to 8.5;
How does it work?
H
Why is pH steady? (Con’t)
H
When CO2 dissolves in water, the following happens:
CO2 + H20  H2CO3  HCO3- + H+  CO3-2 + 2H+
This Equation can go both ways.
This is called Carbonate Buffer.
The CO2, H2CO3, HCO3-, CO3-2 and H+ are all in
proportion, Shifts in pH (or other concentrations) drive
the reaction to reestablish equilibrium.
80% of all carbon compounds in seawater are
HCO3- (bicarbonate ions)
Relationship between:
Temp./Dissolved Gases/pH
Question: How does temperature affect dissolved
gasses and pH?
- Remember; Cold Water holds more gas.
And….
- An increase in CO2 causes a decrease
in pH (more H+ ions).
So….
- Cold Water increases CO2 which in
turns lowers pH.
Relationship between:
Temp./Dissolved Gases/pH (Con’t)
Question: What does this relationship mean to
ecosystems? What is difference between
Connecticut (N. Temperate) and Caribbean
(Tropics)? Deep/Shallow? Warm/Cold Water?
Cold or Deep Water
Holds more gas.
CO2 is a gas.
More CO2 = Lower pH.
H+ dissolves Calcium (Shells).
More Dissolved Shells (and
Adaptations to Protect).
Warm or Shallow Water
Holds less gas.
CO2 is a gas.
Less CO2 = Higher pH.
H+ dissolves Calcium (Shells).
Less Dissolved Shells, more
delicate adaptations.
Let’s try a Double Bubble Map
Sea Shells
Northern Moon Snail
(Lunatia heros)
Scorpion Conch
(Lambis scorpius)
Australia/Pacific
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17
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Northern Quahog
(Mercenaria mercenaria)
(Spondylus regius)
Philipines
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Tiger Cowerie
(Cypraea tigris)
Indo-Pacific
15
27
Channeled
whelk,
(Busycotypus
Canaliculatus)
Edible Periwinkle
(Littorina littorea)
16
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Venus Comb
(Murex pecten)
Indo-Pacific
Temp and Other Dissolved Gas
Question: What is the other important
dissolved gas? - Oxygen (D.O.)
How does it get into the water?
- Photosynthesis and Aeration (Diffusion)
How do environmental conditions affect its
concentration?
1) Higher temp, less gas, so less D.O.
2) No Wind, less aeration, so less D.O.
When do these conditions occur seasonally in
Connecticut? August
Temp and Other
Dissolved Gas
- Hypoxia
- Low levels of D.O.
that interferes
with normal life
process.
- Anoxia
- No D.O. resulting
in death of
living things.
20
Connecticut D.O. Problems?
21
Other important substances
Question: What else is important in the water?
- Nutrients
Where does it come from?
-Organic remains; the decomposition of
dead things and/or wastes.
-Runoff and Sewage.
Where is the highest levels?
- Near bottom; dead things sink.
D.O. and Nutrients in the
Environment?
28
Finally
Question: What do you think would
happen on late August days, near
places that had lots of extra sewage
and organic matter added?
Hot days, no wind, stratified water results
in low Oxygen in bottom water. Added
nutrients (Sewage and Organic matter)
removes more oxygen. Problem is
Hypoxia or Anoxia.
Let’s make a Flow Map on Hypoxia
Hypoxia
End
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http://www.tundracomics.com/default.asp
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http://www.fiddlersrest.co.za/seawater.jpg
http://lifestreamwater.com/images/wavetop.gif
http://www.kidscruz.com/seawater1.gif
http://www.orangesmile.com/ru/foto/oceans/atlantic-ocean-map.jpg
http://www.stonybrook.edu/soundscience/graphics/virtual/fromdistance/small/LISat.jpg
http://www.riversalliance.org/0v.gif
http://www.easttennesseewildflowers.com/albums/weather/Precipitation_types.jpg
http://library.thinkquest.org/C0126220/environment/photo/evaporation1.jpg
http://www.frost-mirror.com.ar/img/iceberg.jpg
http://calif.myhero.com/images/AP_Story/species/g1_u61370_articpolar.jpg
http://www.pharmacology2000.com/physics/Chemistry_Physics/vapor_pressure.jpg
http://www.nicerweb.com/doc/class/bio100/Locked/media/ch08/DB08010.jpg
http://www.campinglife.com/images/elements/1126459_icechest2.gif
http://images.enature.com/seashell/seashell_l/ss0047_1l.jpg
http://www.jaxshells.org/095bb.jpg
http://www.theseashore.org.uk/theseashore/SpeciesPages/Edible%20periwinkle.jpg
http://park.org/Guests/Shells/Shell_Catalogue/Shell_Pages/S/Shell_Lambis_scorpius_scorpius.html
http://en.wikipedia.org/wiki/File:Spondylus.jpg
http://en.wikipedia.org/wiki/File:Murex_pecten_shell.jpg
http://www.sunysb.edu/soundscience/background/hypoxia.html
http://www.stonybrook.edu/soundscience/graphics/sciencobjs/medium/wqaug02.jpg
http://dtc.pima.edu/blc/183/09_183/step3/images/halocline1.jpg
http://www.windows.ucar.edu/earth/Water/images/sm_temperature_depth.jpg
http://cimss.ssec.wisc.edu/sage/oceanography/lesson4/images/sm_salinity_depth.jpg
http://cimss.ssec.wisc.edu/sage/oceanography/lesson4/images/sm_density_depth.jpg
http://www.exoticsguide.org/images/b_canaliculatus_sl.jpg
http://en.wikipedia.org/wiki/File:Cypraea_tigris_1.jpg
Drawing by Mr. England using Promethean Board.
H
= Honors