As nice as it would be to harness the energy of the ocean to do our dirty work for us, sometimes outsourcing can cause bigger problems than the ones it's intended to solve. That could very well be the case with ocean pipes, because while enhancing the Earth's natural carbon cycle could theoretically help to reduce levels of the gas, it could also cause several unintended consequences.
One of the main areas of contention is whether the carbon dioxide pulled out of the atmosphere by the algae would actually stay out. The intention, of course, is for the algae to take up the CO2 and carry it to the bottom for good as the organisms die. Another option is for it to sink to the bottom as fecal matter after marine animals consume and digest the carbon-soaked algae. However, there's no guarantee either of those scenarios will happen. Often, the carbon and nutrients consumed by the algae simply go back into the ocean after the organisms die. Alternatively, marine life that eats the algae might simply release the CO2 during respiration.
Another area of uncertainty lies in the simple fact that, as a natural carbon sink, the ocean already stores significant levels of carbon dioxide. This means that when the pipes pump up cold water full of nutrients, they'll also be pumping up carbon dioxide that could initially contribute to global warming. Whether the final tally would be in favor of carbon release or carbon sequestration remains to be seen.
There's also uncertainty about how much CO2 the oceans are capable of holding before they reach the tipping point. While it's true that the ocean was a sink for CO2 before we got involved, tampering with its natural cycle could prove disastrous for marine life. Regardless of the water's temperature, as CO2 levels in the water rise, the ocean's acidity also rises, which endangers its inhabitants. An added consequence of higher carbon dioxide levels in the water is a decrease in the amount of calcium carbonate available for corals and shellfish to incorporate into their shells. Indeed, coral reefs have already suffered significantly due to rising CO2 levels [source: Kloeppel].
Yet another concern with the ocean pipes deals with the algae they're designed to encourage. While the pipes' proponents argue that the ocean surface is currently deprived of algae because warming waters have stalled the natural upwelling process that brings nutrients to the upper layers, detractors point out that if the algae get out of hand, they could contribute to dead zones -- areas where bacteria feed on algae and suck up all the water's oxygen. It doesn't take a scientist to know that low oxygen levels are detrimental to resident marine life.
Whether the benefits of using ocean pipes to pull CO2 out of the atmosphere would outweigh negative side effects has yet to be determined. Only time will tell if this global warming solution works or is just another crazy pipe dream.
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