1. Chemistry of Water

2. Salinity
An expression of the amount of salt in a fixed amount of seawater.
Expressed as ppt (parts per thousand) 0/00
Parts per thousand literally means “x” amount of solutes per thousand parts of water.
Remember that solutes are the ;substances being dissolved by water , which is the universal solvent. A Salts are hydrophillic meaning they love water!
Salinity varies over the surface of the oceans. The salinity at any particular spot depends on what processes or factors are operating at that location that either add or remove water.

4. Factors Affecting Salinity
Salinity decreases when water is added
High amounts of rain, melting sea ice, river input)
Salinity increases when water is removed
High evaporation, sea-ice formation

5. Salinity
At depth, salinity remains the same in all oceans. Between the sruface and deep water however, is a region called a halocline. This is the area of the water where salinity gradulally increases or decreases with depth.
Salinity is also high in enclosed or partially-enclosed basins (such as the Mediterranean)

6. Where does the Salt come from???
Salt in oceans exist in the form of dissolved ions, some positively charged, and some negatively charged.
There are 6 types of salt ions found in the ocean:
Most common (85% of sea salt): Na (sodium), Cl (chloride), both components of table salt.
Sulfate (SO4)
Magnesium (Mg)
Calcium (ca)
Potassium (K)
Regardless of how salty the water is… they are all found in definite proportions….

7. Principle of Common Proportions
Discovered by Alexander Marcet in 1819 ( ), a swiss chemist and doctor who performed some of the earliest research in marine chemistry
Stated that all the main chemical ions in seawater are present in exactly the same proportions throughout the world’s oceans.

8. Where does the salt come from?
Salts have gotten into oceans in the following ways:
Dissolved out of rocks on land and were carried to oceans in surface run-off
From underwater hydrothermal vents
From dust or volcanic ash blown from land

9. Sinks There are also “sinks” for every type of ion.
SINKS: processes that remove dissolved ions from seawater, such as salt spray onto land, or the falling of ions onto the seafloor as mineral deposits.
Each type of ion has a certain length of time in which it will stay dissolved in water before it is removed, or sinks.
The MOST COMMON ions in seawater will remain dissolved for a FEW HUNDRED years to hundreds of MILLIONS of years!

10. Temperature
Surface temperatures vary widely across the globe according to the amount of heating from the sun
Tropical areas are warmer than polar areas, and remain warmer throughout the year because of constant heating from the sun.
In the middle latitudes, there is more seasonal changes in surface temperature.
In hugher latitudes and polar oceans, the water is constantly cold, often below 32 degrees F.

12. Thermocline
Below the surface: the water drops quickly to about degrees F at 3,300 feet.
3300 ft. down - Region of steep decline in temperature (called the thermocline)
Temperature drops more as you go deeper, but at a slower rate, until the sea floor (constant 36 degrees around the globe)

13. Density Depends on two things:
Temperature – as water warms, it expands, decreasing density, below 4 degrees C, water becomes a little less dense (remember it freezes at 0 degrees C, and floats on water)
Salinity – as salinity rises, density increases, because the salt molecules can occupy spaces between the water molecules
Density increases with depth because of changing temperatures of the water
This drives the ocean currents: It drives large scale circulation of water in the oceans between the surface and deep water.
The Denser/Cooler masses sink and move slowly toward the equator. The colder, high density deep and bottom waters comprise 80% of the total volume of the ocean!

14. Seawater in the world's oceans has a salinity of about 3
Seawater in the world's oceans has a salinity of about 3.5% (35 g/L, or 599 mM). This means that every kilogram (roughly one liter by volume) of seawater has approximately 35 grams (1.2 oz) of dissolved salts (predominantly sodium (Na+) and chloride (Cl−) ions).
Average density at the surface is g/ml. Seawater is denser than both fresh water and pure water (density °C (39 °F)) because the dissolved salts add mass without contributing significantly to the volume.
The freezing point of seawater decreases as salt concentration increases. The coldest seawater ever recorded (in a liquid state) was in 2010, in a stream under an Antarctic glacier, and measured −2.6 °C (27.3 °F).[2]
The most saline open sea is the Red Sea, where high rates of evaporation, low precipitation and river inflow, and confined circulation result in unusually salty water. The salinity in isolated bodies of water (for example, the Dead Sea) can be considerably greater still.

16. WHICH IS SALTIER?? ATLANTIC OR PACIFIC
On average, the Atlantic is the saltiest of the world's major oceans; the salinity of the surface waters in the open ocean ranges from 33 to 37 parts per thousand ( %) by mass and varies with latitude and season.
Surface salinity values are influenced by evaporation, precipitation, river inflow, and melting of sea ice. Although the minimum salinity values are found just north of the equator (because of heavy tropical rainfall), in general the lowest values are in the high latitudes and along coasts where large rivers flow into the ocean.
Maximum salinity values occur at about 25° north and south of the equator, in subtropical regions with low rainfall and high evaporation.
The Pacific ocean Salinity also varies latitudinally.
Water near the equator is less salty than that found in the mid-latitudes because of abundant equatorial precipitation throughout the year.
Poleward of the temperate latitudes salinity is also low, because little evaporation of seawater takes place in these frigid areas.

17. SALTIEST WATER IN WORLD???
The saltiest water in the world is in the Red Sea (that is actually a lake) where the high atmospheric temperatures causes rapid evaporation. Its salt content is 40 parts per thousand.
The saltiest ocean in the world is the Atlantic. Along the Atlantic coast the salinity ranges from 33 parts per thousand off Cape Cod to about 36 off the coast of Florida.
The saltiest part of the Atlantic is an area of about two million square miles south of Bermuda called the Sargasso Sea. The only sea in the world completely surrounded by an ocean. Its salinity content is a bit below that of the Red Sea.
The average salinity of all the oceans is about 3.49 parts per thousand.

18. Gases and Nutrients in Bodies of Water

19. Gas Exchange What are the main gases in H2O?
Dissolved gases such as;
nitrogen, oxygen, and carbon dioxide.
Why is Oxygen highest near the surface?
Levels of oxygen and carbon dioxide vary depending on how many phytoplankton- microscopic organisms that perform photosynthesis, and the activity of other aquatic animals in the area that are respiring.

20. Oxygen: Most soluable in colder water
Highest levels are near the surface
1. oxygen in the atmosphere is diffusing into the water
Diffuses into colder surface waters, so higher oxygen
2. Phytoplankton found living in the top layers, and in high numbers here, producing oxygen from photosynthesis
Levels drop as you go deeper, but then rise again once you get past 3300 ft.
Click here for simulation

21. Carbon Dioxide: The ocean stores 50 times more Carbon dioxide than the atmosphere does
Highest levels are at depth, and lowest levels are at the surface
1. phytoplankton live in high numbers at the surface and use large amounts of carbon dioxide for photosynthesis
2. Carbon dioxide diffuses out of the water and into the atmosphere
3. Carbon sink: Many aquatic organisms make shells out of carbonate, a compound of carbon and oxygen. When they die, their shells may fall to the ocean floor, and become sediments and rocks over time.
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23. Carbon Cycle

24. The Ocean Carbon Cycle
1. Physical Pump: due to CO2 dissolving into sea water, CO2 dissolves into cold ocean water at high latitiudes. It is carried to the deep ocean by sinking currents, where it stays for hundreds of years. Eventually, mixing brings the water back to the surface. The ocean emits CO2 into the atmosphere in tropical areas. This system of deep ocean currents is a “physical pump” for carbon, it helps pump carbon from the atmosphere into the sea for storage.

25. 2. Biological Pump: due to Phytoplankton converting CO2 into carbohydrates from photosynthesis. Animals eat phytoplankton, dead animals and the phytoplankton dink towards the bottom of ocean “marine dnowfall” and some lands on the floor, along with other matter… dead fish, fecal matter, etc… and a small amount of carbon is eventually buried and stored in the sediments and can remain for millions of years. This is called the carbon sink.
BUT some of the carbon is used by animals and bacteria for making shells, reefs, etc… and is eventually returned to the deep ocean part of the carbon cycle… this is the biological pump.

26. Phytoplankton What are they? Why are they important?
Microscopic floating life-forms that obtain energy by photosynthesis, they need nitrates, iron, and phosphates to grow and multiply.
Why are they important?
Form the base of every aquatic food chain
Provide 80% of the world’s oxygen
Continue the nutrient cycle flow

27. Green areas indicate high plankton numbers
Green areas indicate high plankton numbers. What does this say about the type of water plankton prefer? (shallows)

28. Phytoplankton Growth What determines their rate of growth?
The amount of available nutrients in the water (nitrates, iron, and phosphates)
Blooms occur if the supply of nutrients rapidly increases.
Sometimes, Red Tides occur, which can cause mass fish kills.

29. RED TIDES
Red tides, known as, Harmful algal blooms, or HABs, occur when colonies of algae—simple ocean plants that live in the sea—grow out of control while producing toxic or harmful effects on people, fish, shellfish, marine mammals and birds. These algae, known as phytoplankton, are single-celled protists, plant-like organisms Certain species of phytoplankton, dinoflagellates, contain photosynthetic pigments that vary in color from green to brown to red.
One of the best known HABs in the nation occurs nearly every summer along Florida’s Gulf Coast. This bloom, like many HABs, is caused by microscopic algae that produce toxins that kill fish and make shellfish dangerous to eat. The toxins may also make the surrounding air difficult to breathe. As the name suggests, the bloom of algae often turns the water red
Not all are harmful, most blooms, in fact, are beneficial because the tiny plants are food for animals in the ocean. In fact, they are the major source of energy that fuels the ocean food web.

30. Phosphate Distribution in Ocean
The growth of plants in the shallows use up available phosphates in the sediments.
The plants containing this phosphate are then eaten by other organisms. Most of these organisms the return to deeper water.
When they die, their bodies are decomposed by the actions of bateria, which releases the phosphates to these deeper parts of the ocean.
The phosphate in the deeper levels is returned to the depleted shallow waters by the process called upwelling. The longer a section of deep water stays within the deeper parts of the ocean, the more phosphate it will accumulate.

31. Nitrogen Distribution in Ocean
Atmospheric Nitrogen (N2) is the MOST abundant form of nitrogen on Earth.
However, most organisms can’t use it in that form
Bacteria exist in the water to switch the nitrogen gas (N2) into a usable form first as ammonia(NH3), in the process of nitrogen fixation, then changed into nitrates(NO3) in the process of nitrification. This usually occurs in high oxygen content areas such as in the surface layers of the ocean. NO3 is found in the surface waters and are used by phytoplankton.
The nitrogen is passed along the food chain and when the organisms die, the nitrogen in their bodies returns to the water as their bodies decay from bacteria actions. The nitrogen in deeper layers is returned through upwelling.
Denitrification: occurs in benthic or bottom layers of the ocean where there is little available dissolved oxygen. It involves bacteria using the NO3, rather than the O2, during respiration (fermentation), the end results is that the NO3 is returned to the form of N2 which cycles the nitrogen gas back into the atmosphere.

32. Nitrogen Cycle
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34. DEAD ZONES
Dead zones are areas where the bottom water (the water at the sea floor) is anoxic — meaning that it has very low (or completely zero) concentrations of dissolved oxygen.
These dead zones are occurring in many areas along the coasts of major continents, and they are spreading over larger areas of the sea floor.
Because very few organisms can tolerate the lack of oxygen in these areas, they can destroy the habitat in which numerous organisms make their home.

35. DEAD ZONES
The cause of anoxic bottom waters is fairly simple: the organic matter produced by phytoplankton at the surface of the ocean (in the euphotic zone) sinks to the bottom (the benthic zone), where it is subject to breakdown by the action of bacteria, a process known as bacterial respiration.
The problem is, while phytoplankton use carbon dioxide and produce oxygen during photosynthesis, bacteria use oxygen and give off carbon dioxide during respiration.
The oxygen used by bacteria is the oxygen dissolved in the water, and that’s the same oxygen that all of the other oxygen-respiring animals on the bottom (crabs, clams, shrimp, and a host of mud-loving creatures) and swimming in the water (zooplankton, fish) require for life to continue.

36. CAUSES OF DEAD ZONE
The apparent cause of the creeping dead zones is agriculture, specifically fertilizer. While fertilizer is necessary to foster bumper agricultural crops, it also runs off the fields into the streams and rivers of a watershed.
When the fertilizer reaches the ocean, it just becomes more nutrients for the phytoplankton, so they do what they do best: they grow and multiply. Which leads to more organic matter reaching the bottom, more bacterial respiration, and more anoxic bottom water.

37. OTHER CAUSES???
There is another interesting aspect to zones of anoxia—not all areas with anoxic bottom water are caused by pollution.
The largest "dead zone" on the planet is the entire Black Sea below a depth of about 150 meters.
Due to the fact that the exchange of water in the Black Sea with the Mediterranean Sea is limited to the flow through the narrow Bosporus, all of the mixing of freshwater and seawater takes place in the upper 150 meters, because the freshwater entering from rivers is less dense than seawater.
Below the pycnocline (a density boundary where the water density increases abruptly), the Black Sea water column is entirely anoxic, down to the bottom 2000 meters below. Special sea Cameras can’t see that deep, but it can get a good image of the Black Sea on a clear day.