Objectives 1.Understand the basic chemical and physical properties of water & seawater. 2.The origin of the seas

Global Water Distribution Estimate (Scroll down to global water distribution table)

What percentage of the human body consists of water? Babies: 78% One Year old: 65% Adult men: 60% Women: 55% Why do women have less water? –They have a higher percentage of fat --> hold less water

What about marine organisms? Most consist of about 80% of water Jellyfish? –Over 95%!! Recently discovered species of sea anemone, Aleutian Islands Nomura Jellyfish, Japan

Water is unique. Why? Naturally occurs in all three states: –Solid, liquid, and gas No other substance on earth does this

Element vs. Molecule What’s the difference? Element: –Composed of a single type of atom (only about 118 of these in the world) Molecule: –Combination of two or more atoms What does water consist of?

Molecular Makeup: H 2 O Opposite charges Oxygen is (-) Hydrogen is (+) Draw a water molecule Forms weak hydrogen bonds Why is it important that water has weak bonds??

Hydrogen bonds This is what allows water to go from state to state Molecules in constant motion What happens when they speed up? They get warmer and then... ?

Fast and Slow molecules The bonds break and water enters the vapor state What about when it cools? Movement slows down, becomes dense until is slows down so much that...

It freezes! What temperature is water at it’s most dense form? 4º C. Is it frozen at this temperature? Why is this important? What if ice were water’s densest state?

The Changing Molecular Structure of H 2 O What do you notice about the structure of each state?

Bottom line Seawater becomes denser as it cools, until it freezes. Ice is less dense than liquid water

Heat and Water Water has the highest latent heats of melting and evaporation How does ice keep our drinks cold? –It takes a lot of heat to melt ice –Heat breaks hydrogen bonds in ice instead of heating up your drink --> drink stays cold –Why do we sweat? H 2 O has high heat capacity –Absorbs a lot of heat w/ a relatively small increase in temp Why is this important for marine organisms? –Not subject to drastic temp change

The Universal Solvent Why can water dissolve more things than any other substance? It’s both (-) and (+) charged! Pulls apart salt – Sodium (Na + ) Chloride (Cl - )

What Makes up Seawater? Ions (charged particles) enter the sea from different places

Composition of Seawater There’s a little bit of everything 6 ions compose over 99% of dissolved solids in seawater NaCl make up over 85% This composition stays relatively the same –Rule of constant proportions Why is this important? Sea organisms rarely have to deal with changes in the ratios of various ions --> easier to control their internal water/salt balance

How Salty is the Ocean? Seawater has a salinity of 35 parts per thousand (ppt) –For every 1000 g of seawater --> 35 g of salt

That’s a lot of salt... If salt were removed from ocean and spread evenly over earth’s land surface, it would form a layer about 500 feet thick (the height of a 40- story office building) How do the seas get so salty? How did the seas get here in the first place?

Origin of the Oceans 4 bya earth was large, hot rock w/out a trace of water Outgassing –Releasing of gasses from mantle through volcanic activity –Comets and meteorites brought gasses as well –Methane, ammonia, water vapor, carbon dioxide 3.8 bya, earth’s surface cooled below 100°C --> water condensed into rain and poured onto land for centuries Water filled basins and gravity kept it there

The Water Cycle Quick review of the water cycle. What does this mean?

Cleopatra Your drinking the same water Cleopatra bathed in over 2000 years ago!

Salinity Salinity, Temperature, and Density Halocline: –A layer of cold, salty water that acts as a barrier Sea ice forms --> releases salt --> denser water sinks Keeps warmer water from melting ice *Icicle of Death Clip

Temperature Salinity, Temperature, and Density Thermocline: –Layer of water where the temp changes rapidly What causes this? –Solar radiation absorbed and mixed (waves and turbulence) evenly in the first m –90% of total ocean volume is below thermocline –Avgerage SST? 62°F –Average temp of the rest of ocean (below thermocline)? 32°-37° F

Density Salinity, Temperature, and Density Temp decreases --> ? –density increases Salinity increases -->? –density increases Pycnocline: –Layer where there is a rapid change in density *underwater lake clip

Bottom Line Temp and salinity of seawater determine it’s density: It gets denser as it gets saltier, colder, or both How do scientists get these measurements?

How do we get this data? CTD: –Conductivity-temp- depth meters Fig. 3.9 in text Red arrow for water samples Yellow arrow: electronic instruments (temp, salinity, light, clarity) CTD description

Dissolved Gases How do fish breathe? What are they filtering out of the water? Dissolved oxygen Seawater has dissolved gasses: O 2, CO 2 (80%!), N 2 How much O 2 in seawater? –4-6 ml/l (less than 1%) –In the air we breathe? –210 ml/l of air or 21%

Transperency Seawater is relatively transparent. Why is this so important? So photosynthetic organisms can grow What colors are in sunlight? Do they all travel equal distances?

True colors Fig 3.12 in text: at 30m (90ft) only blue light remains With an electronic flash you see sea star’s true colors Can a plant photosynthesize at this depth if only blue light is present?

Pressure At surface, how much pressure? –Tin can demo –1 ATM or 14.7 lbs/in 2 Every 10m (33ft) of increased depth --> 1 ATM How much pressure on a organisms that dives to 100m? –14.7psi x 11 = 161 psi What happens if that organisms surfaces too quickly?

Fig 3.15 in text: swim bladder blows up like a balloon because of decreased pressure.