1. Chemical and Physical Features of Seawater and the World Ocean

2. The “Weather” of the Marine Environment
Wind
Waves
Tides
Currents
Temperature
Salt

3. Where organisms are found in the marine environment is determined by the chemical and physical factors
To understand the biology of marine organisms, we must know something about the environment in which they live

4. The Waters of the Ocean

5. Marine organisms are mostly made of water
80% or more by weight in most cases
Jellyfish – 95%
Water makes life possible

6. The Unique Nature of Pure Water
All matter is made of atoms
Elements – made of a single kind of element
Molecules – two or more atoms joined together – ex. Water
Water molecules stick together because of their polarity
These weak bonds are known as hydrogen bonds

7. Hydrogen bonds make water different from any other substance on earth

8. Three States of Matter Solid, liquid, gas
Water is the only substance that naturally occurs in all three states on earth

10. Special Characteristics of Water
In liquid water hydrogen bonds hold most of the molecules together in small groups
Temperature is a reflection of the average speed of the molecules – faster they move the higher the temperature
When the molecules move fast enough they escape the hydrogen bonds and enter the gaseous phase (evaporation)

11. In water vapor the molecules are not held together by hydrogen bonds
As water cools the molecules pack closer together and take up less space
Therefore the density of water increases as water cools until it reaches 4oC
Below 4oC water becomes less dense
Cool seawater will sink since it is denser

12. Once water cools hydrogen bonds reform
Ice crystals (solid made of regular patterns of molecules)
Water molecules are spaced farther apart than in liquid water making ice less dense than water
Ice will float on top of water – special property that makes life in the water possible – insulates water below

13. Heat and Water It takes a large amount of heat to melt ice
As heat energy is added and the temperature of ice rises, the molecules vibrate faster, breaking some of the hydrogen bonds that hold the crystal together

14. Latent Heat of Melting
Amount of heat required to melt a substance

15. Melting Ice
Once ice begins to melt added heat breaks more hydrogen bonds rather than increasing the speed of molecular motion
Any heat put in goes into melting the ice, not into raising the temperature

16. Heat Capacity
Amount of heat needed to raise a substance’s temperature by a given amount
How much heat a substance can absorb
Water has one of the highest heat capacities of any substance

17. Importance of Water’s High Heat Capacity
Most marine organisms are not subjected to the rapid and sometimes drastic temperature changes that occur on land

18. Latent Heat of Evaporation
The amount of heat energy that is needed to evaporate a substance
Change from a liquid to a gas
Water absorbs a great deal of heat when it evaporates

19. Water as a Solvent Universal solvent
Especially good at dissolving salts
Salts are made of combinations of particles that have opposite electrical charges
The polarity of water allows it to break down the salts

21. Ion – electrically charged particles
Ions have stronger charges than the ends of water molecules
When a salt enters water the ions break apart and become surround by water molecules which break there hydrogen bonds to surround the ion
Ions pull apart or dissociate and the salt dissolves

22. Seawater
Characteristics of seawater are due both to the nature of the pure water and to the material dissolved in it

23. Solids Dissolved in Seawater
Come from the chemical weathering of rocks on land and are carried to the sea by rivers
Earth’s interior
Hydrothermal vents
Volcanoes

24. Salt Composition Solutes – dissolved materials
6 ions compose over 99% of the solids dissolved in seawater
Na and Cl account for 85% of the dissolved solids in seawater

25. Salinity Total amount of salt dissolved in seawater
Usually expressed as the number of grams of salt left behind when 1,000 grams of seawater are evaporated
1 = dissolved trace elements

26. Ions are good conductors of electricity
Electrical conductivity of seawater therefore reflects the concentration of dissolved ions
Practical Salinity Units – psu – measurement of salinity determined from conductivity measurements

27. Importance of Salinity
Salinity of water greatly affects the organisms that in it

28. Rule of Constant Proportions
Percentage of various ions in seawater remains constant even though the total amount of salt in the water can vary slightly

29. Oceans are chemically well mixed and ocean salinity varies almost entirely as a result of the addition or removal of pure water rather than the addition or removal of salt

30. Addition and Removal of Water
Water is removed from the ocean primarily by evaporation and to a lesser extent by freezing
Water is added to the ocean by precipitation

31. Average Salinity of the Ocean
35 ppt (parts per thousand)
Red Sea 40 ppt
Baltic Sea 7 ppt (from river runoff)

32. Salinity, Temperature and Density
The saltier the water the denser it is
The density of seawater therefore depends on its temperature and its salinity

33. Measuring Temperature and Salinity
Can be measured by lowering specially designed bottles and thermometers on a wire to the desired depth
A weight called a messenger is released to slide down the wire, triggering the bottles to snap shut and trap a water sample

34. Temperature Profile
A graph that shows the temperature at different depths in the ocean
Water column – vertical shaft of water

36. Modern Technology
Oceanographers usually use electronic sensors to quickly and accurately record salinity, temperature and depth throughout the water column, rather than at certain depths
CTDs – Conductivity Temperature Depth meters
XBTs – Expendable bathythermographs – measure temperature

37. Problem
Measurements can only be made at one place at one time – difficult to get information over a large area
Ship had to move to a new place to make more measurements
Conditions change because of currents or weather
Many ships would help but it is expensive

38. Part Solution
Make measurements with automated instruments that are left in the ocean
Satellites can measure surface conditions

39. Dissolved Gases
Gases are dissolved in seawater as well as solid materials
The 3 most important gases are: oxygen, carbon dioxide and nitrogen
Found in the atmosphere and dissolve at the sea surface

40. Gas Exchange
movement of gases between the atmosphere and the ocean surface

41. Gases dissolve better in cold than warm water
Dissolved gas concentrations are higher in polar waters than in the tropics

43. Oxygen Not very soluble 0 to 8 milliliters per liter of seawater
On average 4 to 6 ml/L
Air has 210 ml/L

44. Carbon Dioxide
More soluble than oxygen because it reacts chemically when it dissolves
80% of the dissolved gas in the ocean
.04% in air
Stores more than 50 times as much total CO2 as the atmosphere

46. Transparency Biologically important property
Sunlight can penetrate into the ocean
Allows for photosynthesis
Not all colors penetrate seawater equally well
Water is most transparent to blue light

47. As depth increases more colors are filtered out
Red is the first to be filtered out
Something that is red at the surface looks black or gray at depth because there is no red light to reflect off them and be seen
At depths of 1000 m or 3300 ft there is total darkness

51. Turbidity
Transparency of water is strongly affected by material that is suspended and dissolved in the water
Ex. Muddy water, lots of plankton

53. Pressure Factor that changes dramatically with depth
On land – 1 atm of pressure
With each 10m (33 ft) of increased depth another atmosphere of pressure is added
As the pressure increases the gases are compressed – limits range of orgs – ex. Swim bladder

55. Water Density and the Three Layered Ocean

56. Much of the three dimensional structure of the sea, especially in relation to depth is controlled by the density of the water

57. Stability and Overturn
Densest water sinks so the ocean is usually layered or stratified
Deep water – cold and dense
Surface water – warm and light

58. Water Column Stability
Stable Water Column - Less dense on top, dense on bottom
Low stability – surface water is only slightly less dense
Highly stable – large density difference
Unstable – surface water more dense than bottom water

59. Downwelling – when surface water sinks
Overturn – when dense surface water displaces deeper water
Temperature and density profiles are vertical straight lines for water columns experiencing overturn

61. Overturn usually occurs in temperate and polar regions during the winter when the surface water cools
The water descends to a depth determined by its density

62. The processes that change salinity in the open ocean (precipitation, evaporation and freezing) occur only at the surface
Temperature changes occur only at the surface

63. Water Mass Once surface water has sunk its properties do not change
The volume of water has a “fingerprint”, a characteristic combination of temperature and salinity
Oceanographers can tract the movement or circulation of water masses

64. Thermohaline Circulation
Circulation driven by changes in density which in turn is determined by temperature and salinity
Extend throughout the ocean depths
Important in regulating earth’s climate and chemically mixing the oceans
Brings dissolved oxygen to the deep sea
Helps determine the abundance of life in the deep sea

65. The Three-Layered Ocean

66. Surface Layer 100 to 200 m thick (330 to 660 ft)
Mixed by wind, waves and currents
Also known as the mixed layer

67. Thermocline Sudden changes in temperature over small depth intervals
seasonal

68. Intermediate Layer Below the surface layer of around 1500 m (5000 ft)
Contains the main thermocline

69. Main Thermocline
zone of transition between warm surface water and cold water below
lies in the intermediate layer
rarely breaks down
feature of the open ocean

70. Deep and bottom layers Below 1,500 m or (5,000 ft) Uniformly cold
Typically less than 4oC (39 oF)

71. Motion in the Ocean

72. Surface Circulation
Most intense motion of the ocean occurs at the surface in the form of surface currents and waves
Driven by wind which is driven by heat from the sun
Coriolis effect also strongly influences

73. Coriolis Effect
Earth is round and rotating so anything that moves over its surface tends to turn a little rather than moving in a single straight line
Mostly effects winds and ocean currents that move over large distances

75. Northern Hemisphere – deflects things to the right
Southern Hemisphere – deflects things to the left

76. Winds Patterns
Winds in our atmosphere are driven by heat energy from the sun
Most of the solar energy is absorbed near the equator
Warm air rises at the equator
Air from adjacent areas gets sucked in to replace the rising equatorial air creating wind

77. The wind does not move straight to the equator but are bent by the Coriolis effect – approach at a 45 angle

80. Trade Winds winds near the equator (northeast and the southeast)
steadiest winds on earth
between 0 and 30 degrees

81. Westerlies driven by solar energy more variable
between 30 and 60 degrees
move in the opposite direction to the trade winds

82. Polar Easterlies
Most variable
Between 60 and 90 degrees

83. Surface Currents
The major wind fields of the atmosphere push the sea surface creating currents
All major surface currents of the open ocean are driven by the wind

84. When pushed by the wind the uppermost layer of water begins to move
The water does not move in the same direction as the wind but at a 45o angle because of the Coriolis effect
The top layer pushes the water below but at a 45o angle and so on

85. Ekman Spiral
Spiral change in the movement in the water column when the water is pushed by the wind
At a depth of a few hundred meters the wind in not felt at all
Ekman Layer – upper part of the water column that is affected by the wind

87. Ekman transport – taken as a whole the Ekman layer moves at 90o from the wind direction

88. Consequence of the Coriolis Effect
Trade winds move towards the equator the equatorial currents that these winds produce move parallel to the equator

89. Gyres
Wind driven surface currents combined into huge more less circular systems
Under the influence of the Coriolis Effect

90. Transportation of Solar Heat
Warm currents on the western sides of the gyres carry vast amounts of solar heat from the equator to higher latitudes
Cold currents flow in opposite direction on the eastern sides
Ocean currents act as a giant thermostat warming the poles and cooling the tropics

92. Large scale fluctuations in current patterns can dramatically effect weather around the world - El Nino

93. Role of Surface Currents
Surface water temperatures are higher on the western sides of the oceans where currents carry warm water away from the equator

94. Waves

95. Waves Wind causes Most familiar of all ocean phenomena
Affect the organisms that live on the shore

96. Wave Parts Crest – highest part of a wave
Trough – lowest part of a wave
Wave Height – vertical distance between trough and crest
Wavelength – distance between two successive crests or troughs
Period – time a waves takes to go by any given point

98. Water Movement In a wave crest, water moves up and forward
In a wave trough, water moves down and back
On the whole water particles do not go anywhere at all – just move in circles
Waves carry energy across the surface, not water

100. Formation of waves Begins when the wind starts to blow
The faster and longer the wind blows the larger the waves get
Fetch – span of open water over which the wind blows – determines size of waves

102. Seas
waves that have sharp peaks and relatively flat wave troughs

103. Swells Waves with smooth rounded crests and troughs
Similar to ideal waves

104. Surf
Waves that becomes so high and steep as it approaches the shoreline that it breaks
Waves become closer together
Energy is released on the shoreline when the wave breaks

105. Tsunamis Deadly waves Japanese word for “harbor wave”
Produced by earthquakes, landslides, volcanoes, and other disturbances of the sea floor
Tidal waves – properly called – seismic sea waves

106. Long fast moving waves
Wavelengths of 240 km (150 mi)
Travel 700 km/hr (435 mi/hr) – as fast as a jet plane
Open ocean – not very high – 1 m

107. Warning
Worldwide network of seismic monitoring stations that provide instant notice of an earthquake or other seismic disturbance
System has saved lives but is far from perfect
Can’t predict which earthquakes produce killer tsunamis
Also many people in developing countries do not get the warnings

108. Tides

109. Tides Dominant influence on near shore sea life
Expose and submerge organisms on the shore
Drive the circulation of bays and estuaries
Triggers spawning

110. Causes of the Tides
Caused by the gravitational pull of the moon and sun by rotations of the earth moon and sun
Earth and the moon rotate around a common point (their combined center of mass)
This rotation produces a centrifugal force

111. The centrifugal force just balances the gravitational attraction between earth and the moon
The centrifugal force and the moon’s gravity are not in perfect balance everywhere on earth’s surface

112. On the side nearest the moon, the moon’s gravity is stronger and pulls the water toward the moon
On the side away from the moon the centrifugal force dominates and pushes the water away from the moon

113. If earth were completely covered with water, the water would form two bulges on opposite sides of the planet
Water would be deep under the bulges and shallower away from the bulges

114. Earth is spinning like a top on its own axis
As it does this any given point would be under the bulge and then away from the bulge
High tide occurs when a point is under a bulge and low tide occurs when it is away from a bulge

115. The earth rotates on its axis every 24 hours so a point will have two high tides and two low tides
The moon advances on it orbit each day so a full tidal cycle takes 24 hours and 50 minutes

118. The Sun’s Bulge Sun produces a bulge like the moon but is it smaller
When the sun and the moon are in line there bulges add up and when they are at right angle to one another they cancel each other out

119. Tidal Range
Difference in water level between successive high and low tides

120. Spring Tide When the sun and moon bulge add together
High high tides and low low tides
Named because they seem to surge up like spring water
Occur when there is a full or new moon

121. Neap Tide Occur when sun and moon are at right angles to one another
Moon is in the 1st and 3rd quarters
Average tides
Low high tide and a high low tide

123. Variations in Tides
Tides vary from place to place depending on the location and on the shape and depth of the basin

124. Bay of Fundy, Canada

128. Tide Terms Semidiurnal tides – two high and two low tides
Mixed semidiurnal tides- successive high tides of different height
Diurnal Tides – one high and one low - uncommon

129. Tide Tables Give the predicted time and height of high and low tides
Very accurate

130. The End