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Response to roamer65 (Reply #6)

Wed Jun 5, 2019, 07:35 AM

13. Between deforestation and destruction of ocean phytoplankton by humans...

We're well and truly f*cked.

How much do oceans add to world’s oxygen?


Scientists agree that there’s oxygen from ocean plants in every breath we take. Most of this oxygen comes from tiny ocean plants – called phytoplankton – that live near the water’s surface and drift with the currents. Like all plants, they photosynthesize – that is, they use sunlight and carbon dioxide to make food. A byproduct of photosynthesis is oxygen.

Scientists believe that phytoplankton contribute between 50 to 85 percent of the oxygen in Earth’s atmosphere. They aren’t sure because it’s a tough thing to calculate. In the lab, scientists can determine how much oxygen is produced by a single phytoplankton cell. The hard part is figuring out the total number of these microscopic plants throughout Earth’s oceans. Phytoplankton wax and wane with the seasons. Phytoplankton blooms happen in spring when there’s more available light and nutrients.

Oceans Are Losing Oxygen, Just As They Did 94 Million Years Ago


What Is Causing Oxygen Levels To Decrease?

A number of factors are likely influencing the decrease in oxygen levels in oceans. However, the key culprits are likely an increase in fertilizer use and a warming planet.

Humanity has drastically increased the amount of fertilizer we use to produce ever higher crop yields. However, when that fertilizer runs off into our waterways it eventually makes its way to the ocean. When that happens, microbial communities and algae all of a sudden receive a massive delivery of food. Bacteria and algae colonies exponentially increase to feed on the newly delivered food and when that happens they respire, same as humans. As in, they take in oxygen and release carbon dioxide, removing dissolved oxygen from the ocean.

The second culprit to declining oxygen levels is a warming planet. This one is fairly straight forward. Basic principals of chemistry and physics dictate that colder liquid can hold more dissolved gas than a warmer liquid. You can witness this by opening two Coke cans, then leaving one out on your counter and the other in the fridge. Come back the next day and I bet the one in the fridge has more dissolved carbon dioxide (carbonation).

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roamer65 Jun 5 #6
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