properties of ocean water

Question 1

what are the properties of water? (5)

Answer 1

Transparency = clarity; clearness
- Light can reach photosynthetic organisms e.g.
phytoplankton & seaweeds
- Organisms can see through water

Cohesion and adhesion = water sticks to itself
and to other materials
- Surface tension
- Organisms can ‘walk’ on water e.g. sea
slugs, water strider

Solvent (almost universal – most substances will
dissolve in water)
- Salinity of oceans
- Dissolved nutrients & gases

High specific heat capacity (a lot of energy is
required to change the temp. / state of water)
- Relatively little variation in ocean temperature
- Ocean is involved in moderation of climate
- Ocean can store more heat than land surfaces

Density of ice (solid water) is less than liquid
water
- Ice floats and provides protection for aquatic
organisms living under the ice
- Oceans (and lakes) will not freeze solid

neutral ph

low viscosity

• Water flows easily
• Organisms can swim through water

Question 2

at what temperature the water is 1.00 dense?

Answer 2

3.98

Question 3

Where on earth is the water?

Answer 3

Atmosphere 
Ocean 
Ice caps 
Land plants 
Animals 
Soil 
Rocks (igneous) 
Bodies of freshwater

Question 4

how does water transformation influence the climate?

Answer 4

When water evaporates, it takes energy
from the surroundings

When water condenses, it adds heat energy
to the environment

Question 5

how was the ocean created?

Answer 5

Off-gassing of igneous rocks via volcanoes,
followed by condensation, precipitation and
accumulation of liquid water

Comets (rocks & ice) brought water to earth

Question 6

what were the conditions of early earth?

Answer 6

4.6 billion years old - red, hot snowball

Early atmosphere formed by volcanism

Composition: mostly CO2, with little or no
oxygen

Also, smaller proportions of water vapour,
ammonia and methane

Evidence from ice cores

Question 7

what’s seawater and what does it contain?

Answer 7

A solution of dissolved solids and gases

One liter (1000 g) of seawater contains
about 35 g of dissolved materials

35 parts per thousand (ppt) or 3.5 %

Question 8

which ions are in seawater?

Answer 8

Chloride (Cl-) 55.04

Sodium (Na+) 30.61

Sulphate (SO42- 7.68

Magnesium (Mg2+) 3.69

Calcium (Ca2+) 1.16

Potassium (K+)

Question 9

why is the ocean salty?

Answer 9

Inputs / sources of salt:

Freshwater run-off does contain ions from the
erosion of rocks / soil

Volcanism / hydrothermal vents / uplift

Input from the atmosphere

Outputs from the ocean to atmosphere and
into ocean sediments & mantle

Transformations within the ocean

Different residence times of ions

Question 10

Why are the proportions of ions in freshwater and in seawater different?

Answer 10

Oceans are not just passive receptacles of water, there is a nutrient process

Some organisms use these ions and nutrients for themselves

Question 11

what is the residence time of ions?

Answer 11

average amount of time that an ion spends in the ocean:

• Most abundant ions, long residence time
• Least abundant ions, short residence time

Question 12

how to measure seawater temperature?

Answer 12

Thermometer – alcohol or mercury
Reversing thermometer (depth)
Bathythermograph / XBT
Thermistor
- Temperature probe & meter
- CTD
Acoustic tomography / sound (ATOC)
Satellite remote sensing (SST)
Ocean surface topography

Question 13

how to measure seawater salinity?

Answer 13

Evaporation
Chloride titration
Conductivity
- Salinity probe & meter
- CTD
Refractometer
Satellite remote sensing (SSS)

Question 14

how to measure seawater ph?

Answer 14

Universal indicator / pH paper / litmus paper

Chemical titration

pH probe & meter

Ocean pH sensor

Question 15

how to measure seawater oxygen?

Answer 15

Oxygen probe & meter

Colorimetric method

Winkler titration: a sample bottle is filled completely with water(no air). the dissolved oxygen than is fixed by creating an acid compound through the addition of reagents which will be eventually titrated with a neutralizing compound that will change the color of water=> endpoint coincides with the amount of dissolved oxygen

Question 16

what’s pycnocline?

Answer 16

a layer in an ocean or other body of water in which water density increases rapidly with depth.

Question 17

what’s thermocline?

Answer 17

A layer in a large body of fluid in which temperature changes more drastically with depth than it does in the layers above or below

Question 18

what’s halocline?

Answer 18

, vertical zone in the oceanic water column in which salinity changes rapidly with depth

Question 19

how does the pycnocline act like a barrier to water circulation and organism movement?

Answer 19

Warmer, less salty upper layer is separated from colder, more salty lower layer

Low-density fluid floats on top of high-density fluid

System is very stable – requires a great deal of energy to overcome the stability

Question 20

what are three most abundant gases in seawater?

Answer 20

nitrogen (N2), oxygen (O2) and carbon dioxide

CO2

Question 21

what are the chemical processes affecting dissolved gases in seawater?

Answer 21

Oxygen produced by photosynthesis and
consumed via respiration

Carbon dioxide is consumed by photosynthesis and produced by respiration and can modify

Question 22

solubility of gases in water

Answer 22

The amount of gas that can be dissolved in water depends on the temperature of the water. More gas can dissolve in cold water than in hot water.

Question 23

what’s the mixed layer?

Answer 23

the above layer with lots of oxygen through diffusion from atmosphere and photosynthesis
Layer of water that exists between waters surface and the clines (steep gradients in abiotic factors)

Water temp and salinity remain constant in this mixed layer

Results from turbulence caused by wind and wave action

There is a deepening of the mixed layer with increasing wind strength and duration
Varies between 25-200m in depth

Question 24

what’s oxygen minimum layer and what are its characteristics?

Answer 24

high rate of O2
consumption by bacteria decomposers (of sinking
organic material e.g. phytoplankton)

Deep ocean has reasonable amount of oxygen
because rate of O2 consumption is minimal and
thermohaline circulation

Question 25

what’s pH?

Answer 25

a measure of how acidic the water is

Question 26

what’s the two-layered ocean?

Answer 26

mixed layer and oxygen minimum layer

Question 27

ocean acidification

Answer 27

Decrease in pH of oceans as a result of their uptake of anthropogenic carbon dioxide from the atmosphere

Question 28

how the transmission of light, sound

and heat through the ocean?

Answer 28

Near the equator, the sun’s rays strike the
ocean almost perpendicular to the ocean’s
surface – direct!

Near the poles, the sun’s rays strike the ocean
at an angle, rather than directly

More energy penetrates the surface of the water
at the equator than at the poles

Question 29

how the transmission of light through the ocean happen?

Answer 29

Near the equator, the sun’s rays strike the
ocean almost perpendicular to the ocean’s
surface – direct!

Near the poles, the sun’s rays strike the ocean
at an angle, rather than directly

More energy penetrates the surface of the water
at the equator than at the poles

Question 30

how does light manifest in the ocean?

Answer 30

Not affected by mixing & there is no cline of light.

Light decreases with depth because it is absorbed by sediment particles and plankton

Question 31

how does the transmission of sound through the ocean happen?

Answer 31

Sound waves travel faster in water than in air

• In air at 18oC, the speed of sound is ~341 m/s
• In salt water at 18oC, the speed of sound is ~1,524 m/s

Long wavelength sounds travel further than
short wavelength sounds

Low frequency, long wavelengths

Question 32

how can sound be used?

Answer 32

Sound can be used to measure ocean
temperature, salinity, depth, plankton (ZAP)
and to map the ocean floor ( A sonar device sends out a burst of ultrasound waves that travel through the water and strike the ocean floor or an object, causing them to reflect. The sonar device detects the reflected waves)