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  • Writer's pictureJennifer Depew

Oxygenating the ocean's dead zones.

Updated: Dec 23, 2018

Oceans need oxygen to support fish and marine mammals and to help keep a balance of other types of life. Areas of the ocean where oxygen has been depleted don't support typical species and instead may shift to sulfur loving bacteria which don't need oxygen - and don't produce it like other photosynthesizing algae or sea plants. This is a continuation of a previous post, references are in the first in the series: Oceans need oxygen.

Sulfur loving bacteria ruled the Earth - in a way for hundreds of thousands or billions of years in early stages of Earth's history. (11) They grow in oxygen free areas in a variety of temperatures and ranges of pH (acidity/alkalinity). They can thrive in hotter or more acidic environments than many species that are currently a larger part of the marine environment. Species also commonly exist in more alkaline, brackish, waters and bogs, and some types even survive in ice covered areas of Antarctica. Some types are useful in sewage treatment. (10)

The Baltic Sea is an extension of the Atlantic Ocean but with less direct circulation due to land masses that surround it. Mankind has been living in areas surrounding the Baltic Sea for centuries and farming and fishing have led to changes in fish species and an oxygen free, dead zone, has been expanding in size towards the center. Sulfur loving bacteria have been growing in the oxygen free area as other species have died off or swam away.

The nations in the surrounding area have made significant progress towards protecting the Baltic Sea and yet will it be enough to stop the oxygen free zone from continuing to expand?

Simple solutions include decreasing agricultural and landscaping use of fertilizers containing nitrogen and phosphorus and/or farmed aquaculture that uses the extra nutrients.

  • Excess agricultural nutrients can run-off into the sea and lead to the algal blooms which die off, and which then provide nutrients for decomposition bacteria which use up any available oxygen in the process of consuming the algae nutrients. More precise timing of fertilizer application and methods of applying it can help reduce the risk of excess run-off - the plants use more during some stages of growth than others, and when it is more available to the roots, within the soil rather than just on the surface.

  • Aquatic farming of mussels, shellfish smaller than oysters, and more tolerant of slightly acidic waters than oysters, has been found to be a relatively easy way to produce a protein rich food for humans which grows from the excess nitrogen and phosphorus of agricultural runoff. Other farmed fish require grain feed or smaller fish products that have to caught and fed to the farmed species (ring like barriers are used within open ocean waters to keep the farmed species in a contained area).

  • Aquatic planting of seaweed beds or seagrasses also can be a way to use the extra nutrients. The seaweed can be farmed for human use and both seaweed and seagrasses can provide habitats for other small marine life and protect coastal areas from some erosion risk and help buffer the area against waves.

These ideas are being used in various areas already. A more direct solution for the oxygen free zones where sulfur loving bacteria have started to take over may be more expensive but allowing the problem to get worse may be more expensive. The Baltic Sea would make a smaller test ground to try ideas that might then be helpful in areas of the Pacific Ocean where oxygen free zones have also been found.

Adding oxygen - so simple, yet how? Fish tanks use a pump with tubing to draw air from the exterior down into the base of the tank where it then bubbles upward. Question - could marine based windmills be used to power an underwater oxygen bubbling system? I like windmills - previous ideas: Imagining Windmills: Solar Sail Revolving Ones. The current large three blade windmills have been found to need large amounts of grease for maintenance of the spinning mechanism applied to help keep the gears working smoothly.

Somewhat closeup image of giant three blade windmills.
Large three blade windmills need grease occasionally to keep the gears working smoothly.

Each of those windmill blades are very big, longer than a semi truck, it may be an overestimate but in the image below the windmill blade next to the building looks like it might be three to four times taller than the three story building.

One blade of a large modern windmill mounted pointing upward like a pillar, near a rest area building, in Iowa. It is roughly 12 stories tall in comparison to the 3 story building next to it.
Each of the three windmill blades are very, very tall.

Each of the three windmill blades on modern windmills are very, very tall. The internal gear mechanisms need barrels of grease applied on a regular maintenance schedule in order for the mechanism to continue working properly and to prevent break down from excess friction.

(To be continued.)

/Disclaimer: This information is provided for educational purposes

within the guidelines of fair use./

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