Chemical and Physical Features of Seawater

1
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 earths 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 earths temperature range.
• Less than 1 of the earths 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 waters 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

• http//www.etap.org/demo/biology_files/lesson6/ins
  truction4tutor.html

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
• Waters 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.
23
(No Transcript)
24
(No Transcript)
25
What implications does waters 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).
Waters 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
• http//www.youtube.com/watch?vDVCYlST6mYQ

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 33-37 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

• Osmosis
• 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. 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???

• http//www.whfreeman.com/Catalog/static/whf/phelan
  preview/doc/01_fish.pdf

51
Osmoregulation
52
(No Transcript)
53
The problem of osmolarity
salt water 35 ppt
fresh water 0-5 ppt
54
The problem of osmolarity
Hyper-osmotic
salt water 35 ppt
fresh water 0-5 ppt
FISHES
Hypo-osmotic
55
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

• http//www.youtube.com/watch?vqfWx8msgHqM
• Only first 3 minutes 50 seconds

59
Bull shark-osmoregulation

• http//www.youtube.com/watch?vE9kkfX1d6N4
• National geographic video 253

60
Earth The Water Planet

• http//www.youtube.com/watch?vmoSBExlLu2M

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

67
(No Transcript)
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

• http//www.youtube.com/watch?viSJggIWlH9w

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

72
(No Transcript)
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. 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

88
(No Transcript)
89
Temp, density, climate

• http//www.youtube.com/watch?vqeZgJzt3m04

90
(No Transcript)
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

93
(No Transcript)
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

98
(No Transcript)
99
14.7 psi every ATM
480 ATM at 3 miles down for 7,056 psi
100
(No Transcript)
101
(No Transcript)
102
(No Transcript)
103
Acidity and Alkalinity

• pH measures
• Relative concentration of positively charged H
  ions and negatively charged OH
• Acidicmany 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

• http//www.youtube.com/watch?v_Ww6BIy3nc0
• (red water, blue water, explaining density and
  currents)