Transcript Unit 4 Chemical Oceanography

Marine Science Unit 4:
umassmarine.net
Marine Science: Chemical Oceanography
Day 1 – Water Structure and Properties
Objectives:
 Explain the structure of a water molecule.
 What is a polar molecule?
 What “special” properties does water have because it is
a polar molecule?
 Why does ice float? Why is that important to Earth?
Chemical Oceanography
 The study of the chemical reactions that occur in sea
water
studydiscussions.com
Water Structure
 Water is made up of two elements
 Hydrogen
 Oxygen
ehe.osu.edu
 The chemical symbol for water is H2O
 This means that each molecule of water is composed of
two hydrogen atoms and one oxygen atom.
 Water Boy clip:
http://www.safeshare.tv/w/cAKmYDwOFS
Water Structure
 The hydrogen atoms are bonded to the oxygen atom
in water
 The type of bond that holds these atoms together is a
covalent bond.
 Covalent Bond: Type of chemical bond that involves
the sharing of electrons between two or more atoms
medicalsciencenavigator.com
cultivatecuriosity.com
Polarity of Water
 Water is a polar molecule
because it has an uneven
distribution of charges
 The oxygen atom attracts
the shared electrons close
towards its large nucleus –
making it slightly more
negative (-)
 The two hydrogen atoms
have more protons than
electrons – making them
slightly positive (+)
teachingphysics.wordpress.com
Water Molecules form Hydrogen Bonds
 Water’s polarity allows it to
bond with many other
molecules – including
+ +
itself
 Hydrogen Bonds form
+ +
between water molecules
because the slightly
+ - +
+ +
positive hydrogen end of
one water molecule is
attracted to the slightly
uic.edu
negative oxygen end of
another water molecule
 Hydrogen bonds are much
weaker than covalent
bonds
http://programs.northlandcollege.edu/biology/biology1111/animat
ions/hydrogenbonds.html
Why does ice float? How is it
important to the thermal
conditions on Earth?
Properties of Water
 Due to its polarity, water
has special properties…
 Water as a liquid
 Cohesion/Adhesion
 Viscosity
 Surface Tension
 Ice Floats
xsteam.sourceforge.net
Liquid Water
 Water is liquid at room
temperature because
hydrogen bonds hold the
molecules together
 More energy (heat) is
needed to break the
hydrogen bonds to turn
water from a liquid to a
gas (water vapor/steam)
whatscookingamerica.net
ga.water.usgs.gov
Cohesion and Adhesion
Cohesion
 Water molecules stick to
each other
mylargescale.com
Adhesion
 Water sticks to other
materials
 Due to its polarity, the
partial positive and
negative charges of water
molecules are attracted
to positive and negative
forces of other
substances
nationstates.net
Viscosity
 The tendency of a fluid (gas or liquid) to resist flow
 Most fluids change viscosity as the temperature changes
 Hydrogen bonds hold water molecules together, they make
water more viscous
 As water cools, the viscosity rises more than other liquids
because the hydrogen bonds resists the tendency to move
molecules apart
 This is important for aquatic organisms because it affects the
amount of energy they expend:


For floating/drifting organisms like plankton need less energy to
keep from sinking
For swimming organisms because it requires them to use more
energy to move through it
Surface Tension
 Water’s resistance to
objects penetrating its
surface
 The polar nature of water
allows it to form a “skin”
 Caused by hydrogen
bonds holding the water
molecules together
 Many smaller animals use
surface tension and weight
distribution to “walk on
water”
defneapul-cive1170.wikispaces.com
gps.caltech.edu
Ice Floats?
 Most substances become dense and sink as they cool and
turn from liquid to solid
 Most substances lose density as they heat and turn from
liquid to gas
 Water also becomes less dense as it heats and becomes
denser as it cools… but only to a certain point
 As water cools enough to turn from a liquid to a solid, the
hydrogen bonds spread the molecules into a crystal structure
that takes up more space than liquid water
 With more volume, ice is less dense than water so it floats
 This property has a huge effect on Earth

By floating, ice insulates the water below, allowing to retain heat and
remain a liquid – if ice sank the oceans would be entirely frozen or at
least much colder – this would drastically change the Earth’s climate
Marine Science: Chemical Oceanography
Day 2 – Chemistry of Water
Objectives:
 What are the differences between solutions and
mixtures?
 What is the “universal solvent”? Why?
Solutions and Mixtures in Water
 What is a solution?
 When the molecules of
one substance are evenly
(homogenously) dispersed
among molecules of
another substance.
 Water is the universal
solvent due to its polarity
 What is a mixture?
 Two or more substances
are closely intermingling ,
yet retain their individual
characteristics
 Ex. India ink in water =
can be mixed together but
if left alone ink settles out
 Solvent: the substance
that dissolves the solute
 Solute: the substance that
is dissolved in another
water.me.vccs.edu
clearscience.tumblr.com
Water as a Solvent
physicscentral.com
 Salt dissolves in water due
to water’s polarity
 Water’s polarity pulls
apart/dissociates the salt
crystals (NaCl)
 In the process, the
dissociated sodium and
chloride become charged
particles/ions and are
attracted to the positive
hydrogen atoms and the
negative oxygen atoms of
water molecules
 These bonds tend to keep
salt in the solution
elmhurst.edu
Water as a Solvent
 Substances that do not separate into ions can still
dissolve in water through other mechanisms
 Ex. Sugar is not ionic but can dissolve in water when it is
broken down into its individual molecules
 Because so many substances dissolve in water, it is
known as the “universal solvent”
 A few substances do NOT dissolve in water…
 Non-polar substances like oil do not dissolve in water
 This is why oil spills float on top of the water…
A Tasty Solution Activity
Marine Science: Chemical Oceanography
Day 3- Salinity
Objectives:
 What is salinity?
 What are the major sea salts?
 What are the colligative properties of seawater?
 What is the principle of constant proportions?
 What are the most abundant chemicals in seawater?
 Where do sea salts come from?
 How do temperature and salinity affect seawater?
 What factors affect seawater pH?
planet-science.com
Salts and Salinity
 Salinity: The total quantity or concentration of all
dissolved inorganic solids (ions) in seawater.
 Dissolved Salts: Any salt dissolved in seawater
 Salinity is expressed in parts per thousand (‰)
because even very small variations are significant
 To convert parts per thousand into percent you divide by
10, so that 35 ‰ = 3.5%
 How do scientists measure salinity?
 Methods vary but usually involve the conduction of
electricity
Major Sea Salts
 Only six elements and compounds comprise about 99% of
sea salts:
 chloride (Cl-)
 sodium (Na+)
 sulfur (SO4-2)
 magnesium (Mg+2)
 calcium (Ca+2)
 potassium (K+)
 The chloride ion makes up 55% of the salt in seawater.
©HRW
Why are the oceans salty?
 Weathering/Erosion
 Evaporation
 Hydrothermal Vents
 Biological Processes
 Volcanic Activity
Are the Oceans Getting Saltier?
oceanclassrooms.com
Why are the oceans salty?
 When it rains on land, some of the water dissolves
minerals, like salt, in rocks. That water flows in rivers
to the sea. It carries the minerals with it. When water
evaporates back out of the ocean, it leaves the
minerals behind. The minerals make sea water salty.
palomar.edu
Variations in Oceanic Salinity
 The proportion of dissolved sea salts does not
change, only the relative amount of water
 There is variation in specific areas:
 Mouth of River – near zero
 Red Sea - 40 ‰
 Brackishwater (freshwater mixes with seawater in
estuaries) - 0.6 ‰ to 30 ‰
 Brine Water (areas with high evaporation and little
inflow of freshwater or where salt domes dissolved on
the seafloor – Gulf of Mexico) – Saturated or nearly
saturated
Salinity of Ocean Water
©HRW
Colligative Properties of Seawater
 Colligative Properties: The properties of a liquid that may be
altered by the presence of a solute
 The strength of the colligative properties depends on the quantity of solute
 The colligative properties of seawater are:
 Raised Boiling Point – boiling point of seawater is slightly higher than
pure fresh water
 Decreased Freezing Temp – freezing point of seawater is slightly lower
than that of pure fresh water
 Ability to Create Osmotic Pressure – see next slide
 Electrical Conductivity – Salts act like conductors and conduct
electricity
 Decreased Heat Capacity – It takes less heat to raise the temperature
of seawater than to raise freshwater
 Slowed Evaporation– The attraction between salt ions and water keeps
seawater from evaporating as fast as freshwater
Ability to Create Osmotic Pressure
 Osmosis: Movement of
water through a semipermeable membrane
from areas of HIGH
concentration to areas of
LOW concentration
 Crucial to many
biological processes
sparknotes.com
http://www.youtube.com/watch?v=w3_8FSr
qc-I
Principle of Constant Proportions
 Principle of Constant
Proportions: Principle
that the proportions of
dissolved elements in
seawater are constant
 Only the amount of
water (and therefore the
salinity) changes
 Conservative
Constituents: Dissolved
Salts
 No matter how much the
salinity varies, the
proportion of key
elements and
compounds don’t change
 Useful b/c if you know
the amount of one
element, you can
determine how much
there is of others.
Dissolved Solids in Seawater
 Besides hydrogen and oxygen (H2O) the most
abundant chemicals in seawater are:
 Chloride 18.98 g
 Sodium 10.56 g
 Sulfate 2.65 g
 Magnesium 1.28 g
 Bicarbonate 0.14 g
 Calcium 0.40 g
 Potassium 0.38 g
 Other 0.16 g
*Remember Average Salinity
is 35‰ = 3.5% = 35 g
Determining Salinity
 Using the principle of constant proportions, if you know how
much you have of one seawater chemical, you figure out the
salinity.
 The formula for determining salinity is based on all the chloride
compounds (not just sodium chloride)
Salinity ‰ = 1.80655 x chlorinity ‰
 Example: You have a seawater sample that tests 19.2 ‰ chlorinity –
What is the salinity of this water sample?


Salinity ‰ = 1.80655 x 19.2 ‰
Salinity ‰ = 34.68 ‰
 Likewise, when you know salinity you can determine chlorinity:
 Example: You have a seawater sample that tests 34.68 ‰ salinity –
What is the chlorinity of this water sample?


34.68 ‰ =1.80655 x chlorinity ‰
19.2 ‰ = chlorinity ‰
Practice Using The Principle
of Constant Proportions
Salinity ‰ = 1.80655 x chlorinity ‰
1. If the cholorinity of a
seawater sample is 21.3g,
what is the salinity?
2. If the salinity of seawater
sample is 41.06g, what is
the chlorinity?
Determining Salinity, Temperature,
and Depth
 Scientists measure salinity,
temperature, and depth using
special instruments and
procedures:
 Salinometer: Determines the
electrical conductivity of
water
 Conductivity, Temperature,
and Depth Sensor (CTD):
Sensor that can be attached
to a submersible or deployed
by itself to profile
temperature, depth and
salinity. Data are transmitted
to a ship/vessel

Temperature and salinity are
used to determine density
sardi.sa.gov.au
decagon.com
Salinity, Temperature, and Water
Density
 Most of the ocean’s surface has an average salinity of 35 ‰
 Waves, tides, and currents mix waters of varying salinity and
make them more uniform – so, even surface salinity varies with
the season, weather (especially rainfall and evaporation), and
location (bays, semi-enclosed seas, and mouths of large rivers)
 Rainwater and water flowing from freshwater rivers lowers
salinity while evaporation increases salinity
 Salinity and temperature also vary by depth
 Density differences cause water to separate into layers
 High density layers like beneath lower density layers
 Warmer, lower density surface waters are separated from cool,
high density deep waters by the thermocline
 Thermocline: The zone at which the temperature changes rapidly
with depth
lincolninteractive.org
Thermocline Activity
Acidity and Alkalinity
 Acidity and alkalinity are measured on the pH Scale.
 The pH scale measures the amount of positive hydrogen
ions (H+) and negative hydroxide ions (OH-) in a liquid


Acid: A solution high in H+ ions is considered (0-7)
Base: A solution high in OH- ions is considered to be alkaline (714)
Increasingly Acidic
Increasingly Basic
Acidity and Alkalinity
 pH of Seawater:
 Pure seawater has a
pH of 7 (7 is neutral)
 Typical seawater has
a pH range of 7.8 –
8.3
 Carbon dioxide in
seawater acts as a
buffer and prevents
changes in the pH of
the ocean
nature.com
Carbon Compensate Depth
 Although seawater pH is relatively stable it changes with
depth b/c the amount of carbon dioxide varies by depth
 Upper Depths - generally 8.5 pH– warmer and have
photosynthetic organisms with less CO2
 Middle Depths - more carbon dioxide present from
respiration of marine organisms – more acidic with lower pH
 Lower Depths

1,000 meters = more alkaline/basic
3,000 meters and deeper = more acidic again b/c the decay of sinking
organic materials produces CO2

Carbonate Compensation Depth (CCD): The depth at which calcium
carbonate dissolves as fast as it accumulates
 Generally occurs around 4,500 meters
 Water below the CCD is acidic enough to dissolve sinking shells (which
are made of calcium carbonate)
Marine Science: Chemical Oceanography
Day 4 – Biogeochemical Cycles
Objectives:
 How do the proportions of organic elements in seawater
differ from the proportion salts?
 What is the biogeochemical cycle?
 What elements is fundamental to all life?
 What are the roles of carbon in organisms?
 What are the roles of nitrogen in organisms?
 Why is phosphorous important to life?
 What is the role of silicon in marine organisms?
 What are the roles of iron and other trace metals in marine
organisms?
Organic Dissolved Solids
 Although the majority of dissolved solids are
inorganic salts, there are many other types of organic
solids that are also found in seawater
 Organic: Compound that contains carbon and is
associated with living things
 The Principle of Constant Proportions does not
pertain to organic solids
 Concentrations and proportions of organic material
varies widely
Biogeochemical Cycle
 All life depends on materials from the non-living
(abiotic) part of the Earth
 Organisms require specific elements and compounds to
stay alive.
 Ex. Humans require oxygen gas, water, etc
 Biogeochemical Cycle: The continuous flow of
elements and compounds between organisms and the
earth
Fundamentals of Biogeochemical
Cycles
 All matter cycles...it is neither created nor destroyed...
 As the Earth is essentially a closed system with respect
to matter, we can say that all matter on Earth cycles .
 Biogeochemical cycles are basically the movement (or
cycling) of matter through a system
The Cycling Elements
 Macronutrients: Required in relatively large amounts
 “BIG SIX": carbon , hydrogen , oxygen , nitrogen ,
phosphorous, sulfur
 Other Macronutrients: potassium , calcium , iron ,
magnesium
 Micronutrients: Required in very small amounts, (but
still necessary)
 boron (green plants)
 copper (some enzymes)
 molybdenum (nitrogen-fixing bacteria)
Generalized Biogeochemical Cycle
 Five cycles that we will focus on in Marine Science:
 The nitrogen cycle
 The phosphorus cycle
 The carbon/oxygen cycle
 The water cycle
 The silicon Cycle
 The circulation of chemicals in these biogeochemical
cycles and interactions between cycles are critical for the
maintenance of terrestrial, freshwater and marine
ecosystems. Global climate change, temperature,
precipitation and ecosystem stability are all dependent
upon biogeochemical cycles
Nitrogen Cycle
 Organisms require nitrogen for organic compounds like proteins, DNA,
and chlorophyll (the plant pigment used in photosynthesis)
 Nitrogen makes up 78% of the air and 48% of all dissolved gasses in
seawater… gaseous nitrogen must be converted into a chemically usable
form before living things can use it
 Nitrogen Fixation: Bacteria in the soil can convert gaseous
nitrogen into ammonium (lightning also fixes small amounts of
nitrogen)
 Nitrificaiton: Nitrifying bacteria convert ammonium ions into
nitrite and nitrate (some plants can use ammonium ions others
need nitrates)
 Ammonification: Breaking down nitrogen compounds in the
remains of organisms into ammonia – this is preformed by
decomposers
 Denitrification: Conversion of ammonia, nitrite, or nitrates into
N2 gas. Denitrifying bacteria take nitrogen compounds in the soil
and convert them intro free nitrogen/N2 gas
earth.rice.edu
earth.rice.edu
NITROGEN CYCLE
Woods Hole Interactive
Nitrogen Cycle
 http://www.whoi.edu/page.do?pid=83516
Carbon and Oxygen Cycle
 The main phases of the cycle are:
 Photosynthesis: During this process plants and algae take in carbon
dioxide and release oxygen gas
 Cellular respiration: During this process organisms take in oxygen
and release carbon dioxide
 Decay/Decomposition: When organisms die they are decomposed
and any remaining carbon atoms are released into the
atmosphere/ground
 Fossil Fuels: Rich fuel composed of dead plant and animal matter
 Combustion: Burning of plant or animal matter, burning of fossil
fuels, volcanic eruptions, etc. releases gasses into the atmosphere,
ocean, and ground
 Ocean Storage: Large amounts of carbon are stored in the ocean in
various forms
http://www.whoi.edu/main/topic/
carbon-cycle slide of Carbon Cycle
 http://www.whoi.edu/main/topic/carbon-cycle video
of ocean rock in Oman
Carbon in the Ocean
 Seas have plenty of carbon in many different forms:
 Carbon dioxide in the atmosphere dissolves into the ocean
 Certain carbon containing rocks and minerals can be eroded
and their sediments dissolve in ocean water
 Animals wastes and the decomposition of dead organisms
and their wastes release carbon into the ocean
 Biological pump tends to concentrate carbon and other
nutrients with depth – action by bacteria decomposing
organic material. This pump transfers carbon from the
atmosphere to the deep sea where it concentrates and
remains for centuries
Carbon and Oxygen CycleHuman Impact
 Humans are impacting the carbon cycle in various
ways…
 Burning of fossil fuels- releases excessive amounts of
CO2 that is causing global warming/global climate
change
britannica.com
 Deforestation
 Pollution
windows2universe.org
Oxygen Cycle
glogster.com
edhsgreensea.net
Water Cycle
 Main Phases:
 Evaporation: Liquid water stored in lakes, rivers, streams, and
oceans is heated and forms water vapor
 Condensation: Water Vapor in the atmosphere attaches to particles
in the atmosphere like dust and condenses to form liquid water
droplets
 Precipitation: Water in form of rain, snow, sleet, hail etc. fall from
clouds
 Groundwater: Precipitation infiltrates the soil/rocks and is stored in
the ground
 Run-Off: Precipitation that is not absorbed into the ground flows
into rivers, lakes, streams, and the ocean
 Transpiration: Water is taken up by the roots of plants and can be
used to cool the plant as it evaporates from small holes in the leaves
of plants
Water Cycle Rap
 http://www.youtube.com/watch?v=i3NeMVBcXXU
pmm.nasa.gov
http://quercus.igpp.ucla.edu/research
/projects/res_fr_main_silicon.htm
Silicon Cycle
 About three quarters of the primary production in coastal and
nutrient replete areas of the world oceans is carried out by diatoms.
 Diatom: A phytoplankton that needs silicon (Si) for the build up of their
opaline (silicate) shells.
 In low nutrient areas diatoms still contribute to about one third of the
marine primary production.
 Silicic acid is the biologically available form of silicon in the marine
environment and its surface water concentration can severely limit diatom
biomass build up.
 The silicious tests (skeletons/shells) produced by diatoms tend to be
much heavier than water and sink which provides for the transport of
organic carbon (which is another element found in their shells) from
the surface ocean into the deep ocean(the biological carbon pump).
 Once in the deep ocean, their shells/skeletons form sediments like
rocks and sand (silica is a major component of sand).MUCH later,
these sediments are moved and may become exposed and eroded…
Silicon Cycle
nature.com
Phosphorus Cycle
 Phosphorus is important to marine life in a number of ways… it is
component of ATP and ADP (energy for cells) and also a part of
DNA (genetic information)
 Phosphorus is cycled through marine ecosystems in a number of
ways:
 Plants obtain phosphorous from the soil or water in which they live
 Animals obtain it by eating plants


When the animals die they decompose and the phosphorous is returned to
the soil
When animals defecate (waste) phosphorus is also released. For example,
bird guano is a primary source of phosphorus in seawater
 Phosphorous is also washed into the sea from the weathering of rocks
 Humans are disrupting this cycle…
 Organic fertilizers and human pollution from detergents can release
extra phosphorous into the environment and cause problems for fresh
water and inshore marine ecosystems
 Extra phosphorous can cause algae blooms – the algae will bloom out
of control and when they die the bacteria that decompose them will use
all of the oxygen in the water killing fish and other freshwater
organisms
Phosphorus Cycle
Chemical Factors Affect Marine
Life’s Homeostasis
 Homeostasis mechanisms protect an animal’s
internal environment from harmful fluctuations
 Cellular Transport: living things must obtain materials
from their environment and cellular transport is how
living cells obtain materials/nutrients that they need
 There are two types of cellular transport:
 Passive Transport
 Active Transport
Passive Transport
 Passive Transport: Type of cellular transport that does
not require energy because materials are being
transported with the concentration gradient
 Concentration Gradient: when materials are moved across a
membrane from higher concentrations to lower
concentrations
 3 Types of Passive Transport:
 Diffusion – movement of materials from high to low
concentrations
 Osmosis – diffusion of water across a semi-permeable
membrane
 Facilitated Diffusion – use of protein channels to move
materials from high to low across a cell membrane
Osmotic Solutions
 Hypertonic Solution
When the osmotic pressure of the solution outside the cells is higher
than the osmotic pressure inside the cells, the solution is hypertonic.
The water inside the cells exits the cells in an attempt to equalize the
osmotic pressure, causing the cells to shrink
 Isotonic Solution
When the osmotic pressure outside the cells is the same as the pressure
inside the cells, the solution is isotonic with respect to the cytoplasm.
This is the usual condition of red blood cells in plasma.
 Hypotonic Solution
When the solution outside of the cells has a lower osmotic pressure
than the cytoplasm of the cells, the solution is hypotonic with respect
to the cells. The cells take in water in an attempt to equalize the
osmotic pressure, causing animal cells to swell and potentially burst.
Plant cells swell and the cell wall pushes against the cell membrane
creating turgor pressure. This is the usual condition of plant cells.
Osmotic Solutions
Active Transport
 Active Transport: Type of cellular transport that does
require energy because materials are being
transported against the concentration gradient (low
to high)
 2 Types of Active Transport:
 Bulk Transport: Transporting large materials into or out
of the cell membrane


Endocytosis: Taking material into the cell
Exocytosis: Taking material out of the cell
 Membrane Pump: Using proteins in cell membranes to
pump materials across the cell membrane
Osmoregulation in Different
Environments
 Each species has a range of environmental osmotic
conditions in which it can function:
 Stenohaline – Organisms that tolerate a narrow range of salinities in
external environment
 Euryhaline – Organisms that tolerate a wide range of salinities in
external environment:


short term changes:
 estuarine - 10 - 32 ‰, intertidal - 25 – 40‰
long term changes:
 Diadromous fishes -spend part of life in salt water,
part in freshwater
 Catadromous – live in freshwater and migrate seaward
to spawn ex. eels
 Anadromous – born in freshwater, live in sea, migrate
up river to spawn ex. salmon and sturgeon
Osmoregulators
 Osmoregulators: Organisms that can adapt to
changes in salinity of the surrounding seawater
 Osmoregulators use active transport to maintain a stable
internal salinity so this requires the use of energy
 Helps conserve loss of freshwater from their bodies
 Examples include most vertebrate fish, sharks, etc.
 B/c they can adapt to changing salinities they survive in
variations of salinities…
Osmoregulation:
Sharks vs Bony Fish
 SHARKS
 Maintain internal salt concentrations lower than seawater by pumping
salt out through rectal glands and through the kidneys, yet their
osmolarity is slightly hypertonic to seawater.
 Sharks retain urea as a dissolved solute in the body fluids.
 Sharks also produce and retain trimethylamine oxide (TMAO), which
protects their proteins from the denaturation by urea.
 Retention of these organic solutes (urea, TMAO) in the body fluids
actually makes the slightly hypertonic to seawater.
 Do not drink water, but balance osmotic uptake of water by excreting
urine.
 MARINE BONY FISH
 Marine bony fishes are hypotonic to seawater.
 Compensate for osmotic water loss by drinking large amounts of
seawater and pumping excess salt out with their gill epithelium.
 Excrete only a small amount of urine.
Osmoregulation in Fish
quia.com
Osmoregulation in Sharks
Osmoconformer
dangerous-animals-pets.blogspot.com
 Osmoconformers: Organisms that cannot adapt to
changing salinities.
 Internal salinities rises and falls with the waters surrounding
them
 Passive transport occurs in these organisms so no energy is
needed
 Some osmoconformers do well in changing salinities but
most do NOT
 Examples include many Hagfish and invertebrates like:




Mollusks
Jellyfish
Squid
Octopus
phys.org