mesoscope FROM THE FIELD
Understanding Ecosystems off the Hawaiian Islands

Deep thoughts from the Deep Blue Sea

by |July 6, 2017

By Gwenn Hennon

Tara Clemente, Rob Palomares, Time Burrell, Ryan Tabata and Paul Den Uyl pulling samples from the depths of the North Pacific

Tara Clemente, Rob Palomares, Time Burrell, Ryan Tabata and Paul Den Uyl pulling samples from the depths of the North Pacific

As far as I can see from the ship to the horizon there is nothing but deep blue sea. Not a single ship has passed within sight since we left the north shore of Oahu. We are only a day’s steam away from the Hawaiian Islands, yet in the vast Pacific Ocean we could go weeks without seeing another ship. The ship is nothing more than a tiny speck on a massive blue marble. This is one of the dwindling places on earth where I feel truly alone with my thoughts.

The sea is a deep blue, so clear that you might think it was devoid of life. We have seen only a few seabirds circling the ship and playing in the air currents we generate. We haven’t seen any whales or sharks, only an occasional flying fish taking to the air in front of our bow wake. In this apparent desert, microbial life is king. Microbes here can persist off of little more than sunlight and gasses in the air. Marine microbes are expert recyclers, rapidly scavenging the precious little nitrogen and phosphorous fertilizers in the surface ocean. Some of these microbes can even take nitrogen directly from the air to use as fertilizer. Chemists figured out how to make fertilizer from nitrogen gas by using incredible heat and pressure, but these microbes can do it at ambient temperature and pressure. Billions of years of evolution has given these tiny cells better technology than the accumulated efforts of every chemist in the history of humanity (I note with more than a little envy as a
chemistry major).

Very little gets wasted in this hyper-efficient ecosystem, but a little waste is inevitable. Some of these microbes die, killed by viruses or damaged by UV rays. Instead of being recycled or passed up the food chain a tiny fraction of them will sink into the deep. A slow rain of this waste falls from the surface ocean into the perpetually
dark “twilight zone” of ocean. Carried down with this waste is carbon, nitrogen and phosphorous from the surface. At depth, these elements are released by yet more microbes, munching away on the pieces of the dead and dying cells. About three miles directly below us on the sea floor a very small fraction of this waste will be buried in sediments and preserved for millions of years. In the enormous warehouse of sediment cores drilled from the ocean floor in Lamont-Doherty Earth Observatory, I have seen first-hand how the remains of ancient microbes allow researchers to look into the deep past.

In the next few days, the MESOSCOPE team will set traps to collect freshly sinking material. Our estimates of how much carbon and other elements sink out of the surface ocean every year are still very uncertain. We do not yet understand the factors that allow particles to sink out and escape the gauntlet of scavengers. Carbon carried to depths by dead microbes is estimated to be on the same order of magnitude as the yearly global emissions from fossil fuel burning. So far, the ocean has absorbed about half of the carbon dioxide emitted into the atmosphere from human activity, but we can’t yet predict how the equation might change in the future.

Standing on the back deck of the Kilo Moana, the deep blue sea makes me feel both insignificantly small and reminds me of the power of microbial life to shape our planet. In a million years how many atoms of carbon from my exhaled breath or from the smoke stack of the Kilo Moana will be trapped in deep sea sediments? Not sure I could calculate that yet… but give me some time.


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