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Chemical Oceanography

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1 Chemical Oceanography
Marine Science Unit 4:

2 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?

3 Chemical Oceanography
The study of the chemical reactions that occur in sea water

4 Water Structure Water is made up of two elements
Hydrogen Oxygen 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:

5 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


7 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 (+)

8 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 negative oxygen end of another water molecule Hydrogen bonds are much weaker than covalent bonds + + - + + - - + + + + -


10 Why does ice float? How is it important to the thermal conditions on Earth?


12 Properties of Water Due to its polarity, water has special properties…
Water as a liquid Cohesion/Adhesion Viscosity Surface Tension Ice Floats

13 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)

14 Cohesion and Adhesion Cohesion Water molecules stick to each other Cohesion and Adhesion Cohesion Water molecules stick to each other 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



17 Viscosity The tendency of a fluid (gas or liquid) to resist flow 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


19 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”




23 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


25 Marine Science: Chemical Oceanography Day 2 – Chemistry of Water
Objectives: What are the differences between solutions and mixtures? What is the “universal solvent”? Why?

26 Solutions and Mixtures in Water
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 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 Solvent: the substance that dissolves the solute Solute: the substance that is dissolved in another



29 Water as a Solvent Salt dissolves in water due to water’s polarity 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

30 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…

31 A Tasty Solution Activity

32 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?

33 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

34 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.

35 ©HRW

36 Why are the oceans salty?
Weathering/Erosion Evaporation Hydrothermal Vents Biological Processes Volcanic Activity

37 Are the Oceans Getting Saltier? Are the Oceans Getting Saltier?

38 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.

39 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) ‰ 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

40 Salinity of Ocean Water

41 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

42 Ability to Create Osmotic Pressure
Osmosis: Movement of water through a semi-permeable membrane from areas of HIGH concentration to areas of LOW concentration Crucial to many biological processes

43 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.

44 Dissolved Solids in Seawater
Besides hydrogen and oxygen (H2O) the most abundant chemicals in seawater are: Chloride g Sodium 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

45 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 ‰ = x chlorinity ‰ Example: You have a seawater sample that tests 19.2 ‰ chlorinity – What is the salinity of this water sample? Salinity ‰ = x 19.2 ‰ Salinity ‰ = ‰ Likewise, when you know salinity you can determine chlorinity: Example: You have a seawater sample that tests ‰ salinity – What is the chlorinity of this water sample? 34.68 ‰ = x chlorinity ‰ 19.2 ‰ = chlorinity ‰

46 Practice Using The Principle of Constant Proportions Salinity ‰ = 1
Practice Using The Principle of Constant Proportions Salinity ‰ = x chlorinity ‰ 2. If the salinity of seawater sample is 41.06g, what is the chlorinity? 1. If the cholorinity of a seawater sample is 21.3g, what is the salinity?

47 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


49 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


51 Thermocline Activity

52 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 (7-14) Increasingly Acidic Increasingly Basic


54 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

55 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)

56 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?

57 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

58 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

59 Fundamentals of Biogeochemical Cycles
All matter 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

60 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)

61 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

62 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



65 Woods Hole Interactive Nitrogen Cycle

66 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

67 slide of Carbon Cycle
video of ocean rock in Oman

68 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

69 Carbon and Oxygen Cycle- Human 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 Deforestation Pollution



72 Oxygen Cycle

73 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

74 Water Cycle Rap



77 http://quercus. igpp. ucla. edu/research/projects/res_fr_main_silicon
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…

78 Silicon Cycle

79 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

80 Phosphorus Cycle

81 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

82 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


84 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.

85 Osmotic Solutions

86 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

87 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 ‰, 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

88 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…

89 Osmoregulation: Sharks vs Bony Fish
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.

90 Osmoregulation in Fish

91 Osmoregulation in Sharks

92 Osmoconformer 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

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