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PROPERTIES OF
SEAWATER
2016-2017
WATER
80 to 90 % of the volume of most organisms
Buoyancy and support
Pure water 3 forms:
Liquid
Gas – atmosphere
Solid – snow and ice
•Molecules
•1 atom of oxygen
2 atoms of hydrogen
•H2O
•Bent
•Polar
•Bond is shared
•Hydrogen bond – one end of a molecule attracts
the oppositely charged end of another molecule .
VISCOSITY
•The resistance of water molecules to external
forces that would separate them.
•Floating and swimming
•Reduces sinking tendency of some organisms
•Magnifies problems with drag
SURFACE TENSION
The mutual attraction of water molecules at the
surface of a water mass that creates a flexible
molecular “skin” over the water surface.
DENSITY –
TEMPERATURE
RELATIONSHIP
Water at 4 degrees Celsius or above –
density increases with decreasing temp.
Below 4 degrees the pattern reverses.
Ice is 8% less dense than water.
HEAT CAPACITY
Heat – form of energy.
In water, heat is transferred from place to place
by convection and conduction.
Heat energy measured in Calories
CALORIE
Amount of heat needed to raise the temperature of 1
gram of water 1 degree Celsius.
HEAT CAPACITY
The measure of heat energy required to change
the temperature of 1 gram of a substance 1
degree Celsius.
Water has the highest heat capacity.
LATENT HEAT OF
FUSION
The heat that must be extracted from a liquid to freeze it
to a solid at the same temperature.
Water = 80 cal/g.
LATENT HEAT OF
VAPORIZATION
The heat energy required to convert a liquid to a gas at
the same temperature.
Water = 540 cal/g.
The high heat capacity and the large amount of heat
required to evaporate enables large bodies of water to
resist extreme temp. fluctuations.
Provides a temp. moderating effect for the marine
environment and adjacent land areas.
SOLVENT ACTION
Water – being small and having polar charges allows it to
interact with and dissolve most naturally occurring
substances, especially ions.
DISSOLVED SALTS
Account for the majority of dissolved substances in
seawater.
SALINITY
Total amount of dissolved salts
Measured in parts per thousand
Average ~ 35 ~
Range from 0 at river mouths to ~ 40 at Red Sea
Primary mechanism of salt and water addition or
removal are:
Evaporation
Precipitation
River run off
Freezing and thawing of sea ice
Salts dissolve and produce ions:
Major and minor ions
Major accounts for 98% of total salt conc.
LIGHT AND
TEMPERATURE IN
THE SEA
Organisms in upper portion use light for:
Vision
photosynthesis
Amount of energy reaching surface depends on:
Dust
- clouds
-gases
Organisms that are photosynthetic must live in the
Photic Zone.
Things that diminish photosynthetic activity- decrease
depth are:
--dissolved substances
--suspended sediments
--plankton population
Seawater rapidly absorbs the violet and orange-red
portions of spectrum.
blue and green penetrate deeper
Red usually absorbed in top 10 m.
10% of blue penetrates to 100 m.
When sunlight is absorbed by water molecules – it is
converted to heat energy – motion of water molecules
increases.
Temperature is used to measure the change in molecular
motion.
SALINITY – TEMP. –
DENSITY
RELATIONSHIPS
Density increases when temp. decreases or salinity
increases.
Temp. fluctuates more than salinity so it has a greater
influence.
THERMOCLINE
A subsurface zone to rapid temp.
decrease with depth. (~1 degree
Celsius / meter)
PYCNOCLINE
•Ocean layer, usually near the bottom
of the photic zone, marked by a sharp
change in density.
•Large density difference on either side
of the thermocline separates ocean into
2 layers.
•This inhibits mixing and exchange of
gases, nutrients, and organisms.
PRESSURE
At sea level
1 atm.
In sea pressure increases 1 atm/
10 m depth.
DISSOLVED GASES
Dissolved gases and acid/base buffering:
Solubility of gases in sea water is a function of
temp.
Greater solubility at lower temp.
MOST ABUNDANT GASES IN
SEAWATER
Nitrogen
Carbon dioxide
Oxygen
ACIDITY OF THE OCEAN
Abundance of hydrogen ion controls acidity
and alkalinity of the solution.
- carbonic acid – bicarbonate- carbonate
system in seawater acts as a buffer – limit
changes in pH.
Open ocean pH 7.5 to 8.4
OXYGEN
Oxygen concentration influences distribution of
organisms.
Oxygen introduced into seawater two ways:
1. transfer of oxygen from atmosphere to
seawater.
2. production of excess oxygen by photosynthesis.
Oxygen consumed near the bottom can
only be replaced by oxygen at the surface.
Oxygen replenished by:
Very slow diffusion process from oxygen
rich surface layers downward.
Downward vertical water movement.
OXYGEN MINIMUM ZONE
At intermediate depths animal
respiration and bacterial decomposition
use oxygen as fast as it is replaced.
DISSOLVED NUTRIENTS
Nitrates
Phosphates
Used by photosynthetic
organisms.
OCEAN IN MOTION
•Constantly in motion
•Enhances mixing and minimizes variations in salinity
and temp.
•Also disperses swimming and floating organism, eggs,
spores, and larvae.
•Toxic body waste are carried away while food, nutrients,
and essential elements are replenished.
Heat from the sun is the driving force
behind oceanic circulation.
Circulation processes beneficial to all life
forms:
1. wave action
2. tides
3. currents
-4. vertical water motion
WAVES
•-
up and down movements of ocean surface.
•Heating of earth’s atmosphere produces winds.
•Winds produce waves and surface currents.
•Waves are periodic vertical disturbances of the
sea surface.
SIZE AND ENERGY OF WAVE
DEPENDS ON:
1. wind velocity
2. duration
3. fetch – distance over which the wind
blows in contact with the sea surface.
WAVES ARE CHARACTERIZED BY:
Height – Vertical distance between a wave crest
& the adjacent trough
Wavelength - horizontal distance between 2
successive wave crests or 2 successive wave
troughs
Period – time required for two successive wave
crests or troughs to pass a fixed point.
ROGUE WAVES
•Huge lone wave with very high crests and
low troughs.
–Formed when 2 or more large waves unite.
or
–When waves meet opposing currents.
SWELLS
More rounded crests and longer periods and
extend beyond area they were generated.
TIDAL BORE
Occur in river and estuaries
Black Dragon Tidal Bore
BREAKER
When water depth is less than ½
the wavelength, top of wave
moves faster than bottom --pitches forward, crashes.
WHITE CAPS
Wind produces steep waves with
narrow crests – crest are easily
blown off by wind.
TSUNAMIS
Created by sudden disturbance.
Energy transferred to water
when it reaches surface and
creates high velocity waves.
TIDES
Very long period waves, periodic rise
and fall of sea surface.
Most coast lines have 2 high and 2 low
tides each day.
Time between 2 consecutive high and
low tides is approx. 6 hrs. 20 min.
TIDAL RANGE
Vertical difference between
consecutive high tides and low
tides.
• Moon has twice as much force on
tides than sun.
• Moon completes 1 orbit around the
earth each lunar month (27.5 days)
• Two equal high and 2 equal low
tides every 24 hours and 50 min.
(a lunar day)
Solar tides half as big as lunar
tides.
SPRING TIDES
Sun, earth and moon are in
alignments
(new and full moon)
These are extra high-high tides,
etc.
NEAP TIDES
Occur a week later, sun and moon at
right angles.
Moderate tides
During a lunar month get 2 spring and
2 neap tides.
SEMIDIURNAL TIDES
Two high tides - two low tides
each lunar day.
DIURNAL TIDES
One high and one low each day.
MIXED SEMIDIURNAL TIDES
2 high and 2 low but the successive
high tides are different from each other.
SURFACE CURRENTS
Occur in regions where winds
blow over the ocean with a
reasonable constancy of
direction and velocity
3 MAJOR WIND BELTS IN
N. HEMISPHERE
1. Trade winds
2. Westerlies
3. Polar easterlies
OCEAN CURRENTS
A current – large mass of
continuously moving ocean water.
GLOBAL OCEAN CURRENTS
Largest currents that move across the ocean
1. S. Equatorial
2. Gulf Stream
3. California current
GYRES
Currents that move in giant circles
Also called surface currents
Wind driven
COUNTER CURRENTS
Deeper, slow move in opposite
directions from wind driven
currents.
UNDERTOE
Returning current or backwash
Strong current caused by wave
action.
TIDAL CURRENTS
Swift moving currents, runs
parallel to the shore.
WHIRLPOOL
Rapid movement of surface water in a
circle.
Formed between islands or result of
strong winds.
LONGSHORE CURRENTS
Waves break at an angle and produce
current that moves parallel to the beach
SANDBAR
Long hill of sand that is deposited a short
distance from the shore
•Forms parallel to the beach and acts like a dam.
•If pressure is great enough – ma break and
create a rush of water seaward = called rip
currents = fast narrow currents of water
traveling seaward.
CORIOLIS EFFECT
Currents deflected to the (right) in N. hemisphere
and west (left) in S. hemisphere.
Deeper water layers sit into motion by water
above them – experience the Coriolis effect and
spiral downward.
EL NINO
Prominent warming of the equatorial Pacific
surface waters.
Occurs irregularly every few years…usually at
Christmas time.
Occurs when pressure difference across the
tropical Pacific relaxes and both surface winds and
ocean currents either cease or reverse.
VERTICAL WATER MOVEMENT
Produced by sinking and upwelling processes.
Upwelling – rising water masses
Brings deeper nutrient rich waters to the surface.
Produces area of high biological productivity.
CLASSIFICATION OF MARINE
ENVIRONMENTS
Photic zone
Aphotic zone
50 – 100m.
below 100 m
Light
no light
CLASSIFICATION OF MARINE
ENVIRONMENTS
CONT.
Benthic division:
Environment on sea bottom
Continental shelf
Littoral system:
Supralittoral
Eulittoral
Sublittoral
CLASSIFICATION OF MARINE
ENVIRONMENTS
CONT.
Deep Sea System:
Bathyal zone = continental slope
Abyssal zone = abyssal plains and other
ocean bottom areas.
Hadal zone = below 6,000 m. - trenches
CLASSIFICATION OF MARINE
ENVIRONMENT:
CONT.
•Pelagic division:
–Includes the entire water mass.
2 provinces:
1. Neritic - water over continental shelf
2. Oceanic - water over deep ocean
Know diagram.