Water Properties
75% of the earth’s surface is covered by water.
Water is vital to the existence of all life on
Earth.
Water is the only substance on Earth that can be found naturally in all 3 states. Solid, liquid, gas.
It expands as a solid.
Pure water is colorless, odorless, and tasteless.
It has a neutral PH. It is neither acidic nor basic.
It is the universal solvent (dissolves many substances).
Wherever it goes, it takes along valuable chemical, minerals, and nutrients.
Accounts for 70% of the weight of a cell (the building block of life).
It has high specific heat.
Water molecules are sticky and attach to each other (cohesion and surface tension).
Water is the most cohesive of all non-metallic liquids.
Has capillary action (pulling water up, against gravity).
We need to keep water pure and plentiful.
Why is the Ocean Salty?
Salt in the ocean is 90% the same chemical makeup as table salt.
The ocean salt is made up of magnesium, calcium, potassium, and sulfate.
Salt gets to the ocean from the rocks on land. Rainwater is acidic and dissolves rocks as it falls.
The dissolved minerals are carried to streams, lakes, rivers, and oceans.
Salt also gets to the ocean from volcanoes and hydrothermal vents.
The ocean stays salty because it accumulates there faster than it leaves.
The salinity of the ocean is 3.5%, compared to other water with levels below 0.5%.
It’s been speculated that water is trapped in the transition zone (the area between the upper and
lower mantle area), and scientists have been looking for it for decades.
How Pollution is Changing the Ocean’s Chemistry
Ocean acidification (evil twin of climate change).
Carbon dioxide is changing our ocean chemistry. The PH goes down and there is an increase in
ocean acidity.
Data samples are collected in winter using instruments with sensors on the bottom that collect
information about the surrounding water, such as temperature or dissolved oxygen. The seawater
is collected in large bottles at regular intervals up to the surface, and then analyzed on the ship or
taken back to the lab.
There has been an increase in ocean acidity of 26% since pre-industrial times, due to human
activities. Unless we can start slowing down our carbon dioxide emissions, we’re expecting an
increase in ocean acidity of 170% by 2100. This rate is 10 times faster than rate of acidification
for over 55 million years.
Marine life has never experienced such a fast rate of change and we do not know how they’re
going to cope. Some species are doing well, but many are showing a negative response.
As acidity increases, the concentration of carbonate ions in seawater decrease.
By the end of this century, 70% of all known cold-water corals in the entire ocean will be
surrounded by seawater that is dissolving their coral structure.
Ocean acidification is a global threat. We need to reduce our carbon dioxide emissions by
slowing down global warming and slowing down ocean acidification.
The Ocean is Earth's Oxygen Bank
Oxygen is like money for Earth and the ocean is like a bank.
Deposits are made in 3 ocean layers:
- Surface – through exchange with air
- Water – phytoplankton produce oxygen from sunlight and carbon dioxide
- Seafloor – where plants and corals live
Withdrawals occur when organisms consume
oxygen.
Oxygen is tightly connected to life in the ocean and can tell us a lot about an ecosystem’s healthy
and productivity.
This is why we need an ocean oxygen budget.
A scientist has developed several instruments to measure oxygen in all 3 layers, and the
instruments were deployed in 2 sites. A reef and eelgrass bed.
- Reef – oxygen measurements changed based on the time of day. Oxygen flooded
the water during daylight hours and was withdrawn at night.
- Eelgrass bed – same pattern, but 10 times more oxygen. Factors:
- eelgrass was shallower
- tides – when low tide occurred during high noon, the water became oxygen rich.
It bubbled from the eelgrass, making it appear to boil. Some bubbles reached the
surface, becoming withdrawals. A bubble trap helped measure these
withdrawals. The trap provides new insight about bubbling (ebullition). Bright
sunlight and shallow water meant an abundance of oxygen available to
organisms. As sunlight faded and the tide rose, oxygen deposits stopped.
But organisms continued to consume oxygen creating a hypoxic (low-oxygen)
environment.
Future studies can use this technology to observe the ocean oxygen budget of other locations.
Understanding oxygen budgets helps us understand hypoxia, ocean acidification, productivity,
and how an ecosystem will react to a changing ocean climate.
