1. Chemical and Physical Features of Seawater
Chapter 3
Chemical and Physical Features of Seawater

2. Water for life…

3. Water facts… Most cells are 70-95% water
Three-quarters of the earth’s surface is covered by water.
Water is the only common substances that can be found in all 3 physical states (solid, liquid or gas) within earth’s temperature range.
Less than 1% of the earth’s water is freshwater.
Water makes life possible, as we know it, on earth.

4. What is it about water that makes it a suitable medium for life?
Most of the properties that make water suitable for life are related to water’s ability to form hydrogen bonds

5. Hydrogen bonding
Water is polar because of the unequal sharing of electrons in the bond between H and O in a water molecule.
dipoles
The attraction between opposite dipoles of separate water molecules is a hydrogen bond.

6. Recap important features…
Polar covalent bonds
Hydrogen bonds
electronegativity

7. Water cycle

8. Discovery education- cycles

9. What role does water play in the carbon cycle??

10. Ocean is called a carbon sink
Carbon dioxide is dissolved in large amounts in the ocean
Source is primarily cellular respiration and burning fossil fuels

11. Phases of water Solid- ice (molecules not moving around)
Liquid- water (molecules moving around with some speed)
Gas- water vapor (molecules moving around very fast, too fast to form H bonds)

12. Organisms depend on the cohesion and adhesion of water molecules
Surface tension!

13. Cohesion- H bonds attract water molecules to each other
Adhesion- water “sticks” to other materials

14. Surface tension “skin like” surface of water.
Due to H-bonds- HIGH surface tension
Water’s resistance to objects attempting to penetrate its surface
Individual H bonds are weak compared to covalent bonds but the bonds have cumulative strength in numbers

15. Viscosity- the tendency for a fluid to resist flow (colder, the “thicker” it is because more molecules in a space). This allows plankton to use less energy to stay afloat

16. The cohesive nature of water molecules allows water to resist temperature change…
Specific heat is the amount of heat needed to change the temperature of a substance by 1 degree Celsius.
Specific heat of H2O = 1 calorie (cal) to raise 1 g by 1 degree C

17. Specific heat of water HIGH due to hydrogen bonds
Water will change its temperature less when it absorbs or loses a given amount of heat
WHY? Much of the heat is used to break the H bonds before molecules can begin moving faster

18. High specific heat relevance to life
1. A large body of water can absorb and store a huge amount of heat from the sun in the daytime and during summer while warming only a few degrees. At night and during the winter, the gradually cooling water can warm the air

19. 2. stabilizes ocean temperatures creating favorable environment for marine life
3. since organisms are made primarily of water, they are better able to resist changes in their own temperature than if they were made of a liquid with a lower specific heat

20. Sssooooo…….
Water that covers the earth keeps temperature fluctuations on land and in water within limits that permit life

21. Heat Capacity
Water has the highest latent heats of melting and evaporation and one of the highest heat capacities of any natural substance.
Latent Heat of Melting and Evaporation
Fastest molecules (with most energy) break free of bonds. Slower ones left behind = lower temp.

22. How does H-bonding affect temperature change?
Water molecules tend to “stick together” through H-bonding. Much of the energy that goes into a body of water must first go into breaking these bonds before temperature (i.e. “molecular movement”) can increase.

25. What implications does water’s high specific heat have for living systems?
Large bodies of water can absorb lots of heat from the sun and change temp. very slowly!
Living organisms are made mostly of water which stabilizes body temperature.

26. Water has a high heat of vaporization…
…it takes a great deal of heat to get water to boil (go from liquid to gas phase).
Water’s heat of vaporization = 580 cal/g/0C
Evaporative cooling!

27. Ice is less dense then liquid water…

28. Why ice floats Less dense as a solid than as a liquid
Water expands when freezing

29. Density Density = mass / volume Density is affected by Temperature
Pressure
Salinity
Water is less dense as a solid

30. Lower density and LIFE…
If ice sank, then eventually all ponds, lakes, and oceans would freeze solid making life as we know it impossible
During summer, only the upper few inches of the ocean would thaw

31. INSTEAD……
When a deep body of water cools, the floating ice insulates the liquid water below, preventing it from freezing and allowing life to exist under the frozen surface

32. Salinity and Density Salinity varies with depth
Density differences cause water to layer
High density lies below low density

33. Water: the solvent of life
Solution- a liquid that is a completely homogeneous mixture of two or more substances
Solvent- dissolving agent
Solute- substance that is dissolved
Not “universal solvent”- if it were, it would dissolve any container in which it was stored. “versatile solvent” due to polarity

34. Water is a versatile solvent…
table salt

35. Review- 4 Emergent Properties of water
Cohesive behavior
Ability to moderate temperature
Expansion upon freezing
Versatility as a solvent

36. BozemanBiology Properties of Water

37. Seawater Nature of pure water Materials dissolved in it
Seawater contains a little of almost everything
Solutes = dissolved materials (ex. ions in seawater)
Solvent = liquid doing the dissolving

38. Rule of Constant Proportions
The relative amounts of the various ions in seawater are always the same!
For seawater; no matter how much salinity varies, proportions of key inorganic elements stays the same
Only water amount and therefore salinity changes

39. Salt composition in seawater
Salinity- the total amount of salt dissolved in seawater
Salinity is expressed in the number of grams left behind when 1,000 g of seawater are evaporated
Ex. 35g left from evaporating 1,000g water (35ppt) 35%

40. Average salinity of the ocean is about 35 ppt
Open ocean varies at ppt depending on the balance between evaporation and precipitation

41. Salinity of water greatly affects the organisms that live in it
Most marine organisms die in fresh water
Even slight changes in salinity harm them

42. Pg 72: salinity, osmosis and diffusion
Concentration gradient
Hypertonic
Hypotonic
Isotonic

43. WHY DO FISH DRINK SEAWATER???
Answer in caption figure 4.14

44. Many marine organisms are highly affected by changes in salinity
Many marine organisms are highly affected by changes in salinity. This is because of a process called osmosis which is the ability of water to move in and out of living cells, in response to a concentration of a dissolved material, until an equilibrium is reached. In general the dissolved material does not easily cross the cell membrane so the water flows by osmosis to form an equilibrium. Marine organisms respond to this as either being osmotic conformers (also called poikilosmotic) or osmotic regulators (or homeosmotic).

45. Did you write this?????
Marine organisms respond to this as either being osmotic conformers (also called poikilosmotic) or osmotic regulators (or homeosmotic).

46. Page 74: regulation of salt and water balance
Osmoconformers- internal concentrations change as the salinity of the water changes
Osmotic conformers have no mechanism to control osmosis and their cells are the same salt content as the liquid environment in which they are found (in the ocean this would be 35 o/oo salt). If a marine osmotic conformer were put in fresh water (no salt), osmosis would cause water to enter its cells (to form an equilibrium), eventually causing the cells to pop (lysis). If a marine osmotic conformer were put in super salty water (greater than 35 o/oo salt) then osmosis would cause the water inside the cells to move out, eventually causing the cells to dehydrate (plasmolyze).

47. Hagfish- osmo conformers

48. Osmoregulate- control their internal concentrations to avoid osmotic problems. Adjust solute concentration in their body to match that of the environment

49. Osmotic regulators have a variety of mechanisms to control osmosis and the salt content of their cells varies. It does not matter what the salt content is of the water surrounding a marine osmotic regulator, their mechanisms will prevent any drastic changes to the living cells. Marine osmotic regulators include most of the fish, reptiles, birds and mammals. These are the organisms that are most likely to migrate long distances where they may encounter changes in salinity. An excellent example of this is the salmon fish. The fish is about 18 o/oo salt so in seawater it tends to dehydrate and constantly drinks the seawater. Special cells on the gills (called chloride cells) excrete the salt so the fish can replace its lost water. When a salmon migrates to fresh water its cells start to take on water so the salmon stops drinking and its kidneys start working to produce large amounts of urine to expell the water.

50. Do fish drink water???

51. Osmoregulation

53. The problem of osmolarity:
salt water
35 ppt
fresh water
0-5 ppt

54. salt water fresh water 35 ppt 0-5 ppt FISHES
The problem of osmolarity:
Hyper-osmotic
salt water
35 ppt
fresh water
0-5 ppt
FISHES
Hypo-osmotic

55. salt water fresh water 35 ppt 0-5 ppt FISHES
The problem of osmolarity:
Hyper-osmotic
salt water
35 ppt
fresh water
0-5 ppt
FISHES
Hypo-osmotic
fishes are either:
stenohaline - tolerant of limited range of osmolarity
euryhaline - tolerant of wide range (where is this useful?)

56. How fish deal with being osmotic misfits
1. osmo-conformers (hagfishes)
2. salt supplementers (marine elasmobranches and coelacanths)
3. hyposmotics (marine teleosts)
4. hyperosmotics (freshwater fishes)
excrete large volumes of water
gill chloride cells pump in salts
often euryhaline (striped bass, tilapia, drum)

57. Osmoregulation example
Sharks
Adjust amount of urea in blood
Dunaliella can live in freshwater or water with 9 times saltier than normal seawater
single celled marine algae
Figure 4.15 Sea Turtle

58. BozemanBiology Osmoregulation Video
Only first 3 minutes 50 seconds

59. Bull shark-osmoregulation
National geographic video 2:53

60. Earth: The Water Planet

61. Colligative Properties of Seawater
Properties of a liquid that are altered by presence of solute
1. ability to conduct electrical current
2. decreased heat capacity (less heat to raise temp)
3. raised boiling point (boils at higher temp)

62. 4. decreased freezing temp (freezes at lower temp)
5. slowed evaporation (due to attraction between ions and water)
6. ability to create osmotic pressure (water exists in lower concentration than in freshwater)

63. Salinity review Page 44 Solutes Salinity Rule of constant proportions
*salinity is the total quantity of all dissolved INORGANIC solids, not just salt)

64. Salinity
Ocean salinity varies almost entirely as a result of the addition or removal of pure water rather than the removal of salts
Why are icebergs not salty?
Page 44

65. Water cycle review
Water is added to the ocean by precipitation (rain and snow) and to a lesser extent by the melting of glaciers and polar ice

66. Six solutes (ions) compose 99% of seawater: see table 3.1

68. Those 6 are….. Chloride (55% of total salinity)
Sodium (30.59% of total salinity)
Sulfate
Magnesium
Calcium
potassium

69. Why is the sea salty?
Freshwater minerals and chemicals dissolving and flowing to ocean via precipitation, erosion, waves, surf, and hydrothermal vents

70. Drinking ocean water

71. Ions in sea water figure 3.6
Not all ions in seawater enter the ocean at the same place
Positive ions like sodium and magnesium come from weathering rocks and are carried by rivers
Negative ions like chloride and sulfide enter at hydrothermal vents and volcanos

73. Average salinity The average salinity of the ocean is 35ppt
Open ocean is about 33ppt-37ppt

74. Variations in Salinity
Variations occur in ocean salinity due to several factors:
1. most common factor is the relative amount of evaporation or precipitation in an area. If there is more evaporation than precipitation then the salinity increases (since salt is not evaporated into the atmosphere). If there is more precipitation (rain) than evaporation then the salinity decreases

75. 2. Another factor that can change the salinity in the ocean is due to a very large river emptying into the ocean. The runoff from most small streams and rivers is quickly mixed with ocean water by the currents and has little effect on salinity. But large rivers (like the Amazon River in South America) may make the ocean have little or no salt content for over a mile or more out to sea.

76. 3. The freezing and thawing of ice also affects salinity
3. The freezing and thawing of ice also affects salinity. The thawing of large icebergs (made of frozen fresh water and lacking any salt) will decrease the salinity

77. Dissolved Gases Oxygen = O2 Carbon Dioxide= CO2 Nitrogen= N2
All Three are found in atmosphere and dissolve into ocean at surface

78. nitrogen Required for protein, nucleic acids and chlorophyll
Makes up 78% of air and 48% of gases dissolved in sea water
Nitrogen fixation- bacteria absorb nitrogen and put it into chemical compounds organisms can use

79. Gas exchange
When the reverse occurs and the sea surface releases gases to the atomosphere

80. Pg 47
Gases dissolve better at colder water (polar) – Why?

81. As the temperature decreases, so does the kinetic energy of any particle
The gas as a lower energy and thus cannot escape the water
Solubility decreases with increase of temperature

82. The concentration of dissolved oxygen and carbon dioxide are very important for marine life forms. Although both oxygen and carbon dioxide are a gas when outside the water, they dissolve to a certain extent in liquid seawater.

83. Gases in the Ocean page 47
CO2 makes up 80% of gases in ocean. In air it is only .04%. (reacts chemically when dissolved)
Most important gases are: oxygen, carbon dioxide, and nitrogen
“gas exchange” between atmosphere and ocean

84. Dissolved oxygen Oxygen is not very soluble
Less oxygen in water than in air
Susceptible to oxygen depletion by respiration

85. Gases dissolve better in cold than warm, so dissolved gas concentrations are higher in polar waters than the tropics

86. Dissolved oxygen is what animals with gills use for respiration (their gills extract the dissolved oxygen from the water flowing over the gill filaments). Dissolved carbon dioxide is what marine plants use for photosynthesis.

87. temperature
Temps in the open ocean varies between -2C and +30C (28 F and 86F)
Temp varies more than salinity
The temperature and salinity of seawater determine its density. It gets denser as it gets saltier, colder, or both

89. Temp, density, climate

91. Figure 3.10 page 46

92. Transparency
One of the most biologically important properties of seawater
All photosynthetic organisms need light to grow
Figure 3.11 show colors of the visible spectrum and the depths of penetration

94. What are the colors of the visible spectrum?
ROYGBIV
In clear ocean water, blue light penetrates the deepest, red light the least
Figure 3.12 page 47

95. Page 47
Photosynthesis equation
Cellular respiration equation

96. Pressure page 48 Pressure changes with depth
On land, we are under 1 atmosphere (14.7 pounds psi)
Marine organisms are under the weight of the water and the atmosphere…..and water is heavier than air

97. With each 10 m (33 ft) of increased depth, another atmosphere of pressure is added
Added pressure compresses gases
Figure 3.15

99. 14.7 psi every ATM
480 ATM at 3 miles down for 7,056 psi

103. Acidity and Alkalinity
pH measures
Relative concentration of positively charged H ions and negatively charged OH
Acidic=many H ions. pH less than 7
Alkaline- many OH ions. pH more than 7

104. pH…

105. pH changes with depth due to the amount of carbon dioxide
Shallow- pH 8.5
Middle- pH lower due to more carbon dioxide
Deep- more acidic due to no photosynthesis
At 3,000 M and deeper, it becomes even more acidic due to sinking organic material decay

106. The oceans are not, in fact, acidic, but slightly basic.
Acidity is measured using the pH scale, where 7.0 is defined as neutral, with higher levels called "basic" and lower levels called "acidic".
Historical global mean seawater values are approximately 8.16 on this scale, making them slightly basic.
To put this in perspective, pure water has a pH of 7.0 (neutral), whereas household bleach has a pH of 12 (highly basic) and battery acid has a pH of zero (highly acidic).
However, even a small change in pH may lead to large changes in ocean chemistry and ecosystem functioning. Over the past 300 million years, global mean ocean pH values have probably never been more than 0.6 units lower than today (6). Ocean ecosystems have thus evolved over time in a very stable pH environment, and it is unknown if they can adapt to such large and rapid changes.

107. journal http://www.ocean-acidification.net/FAQacidity.html#AcidicOA
Answer the 4 questions at the top

108. Density and temperature experiment
(red water, blue water, explaining density and currents)