4. Ocean Made Earth Habitable

How did the ocean start?

How did life from the ocean start?

All life requires water, food, space, protection, and oxygen. Take in a deep breath. Now breath out, slowly. Due this twice. On average, half of the oxygen that we breathe comes from the ocean, so do all the other requirements for life.

It is not only the plants on land that are producing the oxygen we breathe. In the ocean, algae, and bacteria partake in photosynthesis. They all have special organelles within their sells called Chloroplasts. These organelles transform the carbon dioxide CO2, into food for everyone in the food web, and releasing oxygen.

During photosynthesis, sunlight energy is transformed and stored into compounds made of carbon, hydrogen, and oxygen. Photosynthesis is the conversion of light energy, into chemical energy. This is used to power life.

Photosynthesis: CO2 + H2O + Light Energy → Glucose (sugar) + O2

Respiration in our bodies, is the opposite reaction:

Respiration: Glucose + O2 → CO2+ H2O + energy release (heat)

Fossil Fuels like coal, oil, gasoline, and bitumen are also carbon compounds, going up into the atmosphere. Made by life long ago, fossil "fuels" were built up in long-term deposits that removed them from ‘rapid’ carbon cycling. It removed them until we started to dig them up and burn them at a rampant rate. All of life cycles carbon naturally but we are making record changes now, by rampantly burning fossil fuels. You can calculate you own carbon footprint with the Global Footprint Network

It is the burning that releases the carbon dioxide. The basic reaction for combustion (burning) takes the carbon compound and turns it into carbon dioxide and heat.

Our modern economy and way of life are built upon the combustion engine, clearing out vegetation and putting down a lot of concrete. Excessive production of CO2 emissions in the last 70 years are called rampant because they release and excessive amount of natural CO2 release.

The ocean stores about 90% of the extra heat from global warming. The ocean takes up about 30% of our fuel-burned emissions of CO2. Unfortunately, by absorbing all the excessive CO2, there has been another problem created, Ocean Acidification. The ocean is becoming more acidic. Loose hydrogen atoms that have been left over from the carbon dioxide CO2 react in water to make carbonic acid (CO3-2) and hydrogen atoms, and thus is changing the natural pH balance of the ocean.

CO2 + H2O ⇌ HCO3- + H+ ⇌ CO32- + 2H+

File:Ацидификација на океани.jpg

pH is the measure of how acidic or basic a solution is. This is determined by the level of free hydrogen ions in the water (the H+ that, when combined with oxygen, makes H2O). It is measured on a scale from 0 to 14, where 0 is the most acidic and 17 is the most basic. Seven is considered a neutral solution (pure water).

Water on the surface of the Earth is usually a little acidic or basic due to both geological and biological influences. For example, when algae naturally begin to increase in estuaries during warmer seasons as the water temperature rises, the pH levels tend to also rise. On the other hand respiration from organisms releases CO2 into the water which lowers the pH. Each living organism is adapted to survive in a particular pH range. Too acidic, or too basic, and critical biological processes may be disrupted in organisms.

This release of hydrogen (H+) into the ocean is increasing the water’s acidity. An acidic ocean can be corrosive, especially in temperate and polar waters, and globally it is significantly more acidic than it used to be. Ocean life and marine ecosystems that we depend on are highly adapted to living in a slightly alkaline and buffered ocean pH (pH is the measure of that acidity in the water).

Organisms that build a calcareous shell, such as clams, snails, and crabs, are at risk because the acidic breaks down their shells. This calcification breakdown threatens the survival of these animals. Corals are also affected by ocean acidification, in an event called coral bleaching. Normally coral polyps live in an endosymbiotic relationship with the algae that lives within their tissues. When the water is too acidic it causes the coral polyps to expel the algae living in their tissue which causes them to starve.

Coral Bleaching Infographic

Most of the life there will not be able to survive if the ocean is too acidic. Our survival, as well, is dependent on a healthy working ocean.

The less CO2 we emit, the less likely we are to pass a point of no return for either warming, or ocean acidification. We can reduce CO2 emissions and we can also remove carbon from the cycle by protecting habitats that bury carbon, long-term, in the sea floor. Carbon that is stored long term, and taken out of the short-term carbon cycle, is called Blue Carbon. Ecosystems with high blue carbon are much more effective at removing carbon than land ecosystems. Efficient examples of blue carbon are sea grasses, mangroves, phytoplankton, and kelp forests. By protecting the ecosystems that produce ‘blue carbon’ we reduce the amount of carbon that is in the warming and acidification cycles.

kelp forest

Ocean acidification is not the only threat to the habitability of the oceans and earth. Hypoxia is another growing concern. Hypoxia means there are low levels of dissolved oxygen. Marine organisms require sufficient levels of dissolved oxygen in order to survive. Oxygen enters the water either through (1) diffusion from the atmosphere or (2) photosynthesis from aquatic plants. Surface winds and waves can also increase the rate at which oxygen from the air is dissolved or absorbed into the water. The amount of oxygen fluctuates naturally, both seasonally and over time. There are some natural causes of hypoxia, as well as human-made causes.

Stratification, when less dense freshwater mixes with dense heavy salt water and creates two separate layers in the water column because the densities do not mix well. This division restricts the supply of oxygen from the surface to the bottom waters which leads to hypoxia conditions in those lower habitats.

The most common cause of hypoxia is from human-induced factors, especially nutrient pollution. This is when there is an excess of nutrients such as phosphorous, which is introduced into the ecosystem through agricultural run-off, urban run-off, fossil fuel burning, and wastewater treatment effluent. The phosphorus essentially "squeezes" out the oxygen, creating hypoxic conditions.

In some cases, large areas of open water can become hypoxic. No longer able to sustain life due to the lack of oxygen, these areas become dead-zones. Dead-zones are an area of little or no dissolved oxygen, which may cause die-off in fish, shell-fish, corals, and aquatic plants.

A map of the Dead Zones on Earth, as of 2010, from the NASA Earth Observatory

Even though the ocean made life on land habitable in the first place, there is a limit to what the ocean can do to keep Earth habitable. Reducing rampant CO2 emissions is a start, and protecting blue carbon sinks are the right things to do. Protection of these important ecosystems, and regulations for proper waste disposal, are vital. These actions can help the ocean continue to make Earth habitable and protect people, place, and life supporting ecosystems for us and future generations. You can make an impact today.

Complete the Ocean Acidification Experiment. Afterwards you may take the Ocean Made Earth Habitable Quiz to earn your badge.

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