Fish – It’s What’s for Dinner

The oceans of Earth play an essential role in making our planet habitable for life as we know it. In fact, scientists are still unable to fully explain how the oceans affect the planet’s biogeochemical cycles, upon which all life depends. Changes in the oceans, such as pH and oxygen content, could have profound implications for the future of Earth’s climate and habitability. Astrobiologists hope to gain insight into the delicate links that exist between the oceans, climate and biosphere. Their work could be essential understanding climate change – and could help identify potentially habitable planets beyond our own solar system.


 

Change in sea surface pH caused by anthropogenic CO2 between the 1700s and the 1990s
Credit: Wikipedia Commons

Like it or not, ocean acidification will reverberate through our economy and food supply, in the form of lost habitat, and drastic changes in kinds and densities of certain species. Plankton, which are the backbone of the marine food chain, have been severely affected. As the bellweather species of the ocean ecosystem, the fate of plankton – there are thousands upon thousands of varieties – determines the fate of all sea-dwelling life.

I stopped eating sushi a few years ago when I began learning about ocean acidification and the decline of the world’s fisheries. The NOAA Fisheries Office of Science and Technology reports that the United States is the third largest seafood consumer in the world. Americans ate a record of nearly 17 pounds of seafood per person in 2004, while total consumer spending for fish and shellfish topped $62 billion. In that year alone, coastal and marine commercial fishing generated $32 billion for the economy and employed over 67,000 people.

Regardless of whether you eat fish or not, the image of an octopus trying to climb a fishing line in an attempt to escape anoxic water, reported by The Times (UK) has a way of making an impression.

Anoxic water occurs in parts of the ocean where the concentration of oxygen has been so diminished that marine life cannot breathe. Low-oxygen areas occur naturally near the west coasts of all continents, where near the surface there is sufficient sunlight to support photosynthesis. In these environments, photosynthetic plankton flourish; and at the surface, oxygen is plentiful enough. But when insufficient oxygen at the surface causes a die-off in plankton, their nutrient-rich remains drift to lower depths, causing a secondary bloom in microscopic animal life – the kind that does not contain chlorophyll and does not photosynthesize. Instead of contributing to deep-sea oxygen stores, these microorganisms are oxygen consumers.

The water becomes oxygen-starved. The sea life that relies on it suffocates.

The astonishing diversity of phytoplankton as seen under a microscope.
Credit: Smithsonian Environmental Research Center

A long time ago, I saw a television program about a marine biology lab. It housed among other things, tanks of tropical fish, as well as a tank containing an octopus. Over the course of several days, scientists began to notice that the population of fish were diminishing. They were not dying – there were no bodies floating on the water’s surface in the morning. Fish were simply vanishing, one by one. Other than a mysterious wet spot on the floor, nothing in the lab seemed, well, fishy.

Determined to solve the mystery, the research staff resorted to espionage. They mounted a video camera in the lab before they left for the evening.

In the morning, the tape revealed all. As soon as the door closed behind the last scientist, the octopus hefted itself out of its tank, slid noiselessly onto the lab floor (hence the wet spot), climbed up the shelf to the fish tank, helped itself to a tropical fish or two, then slid calmly back to its own quarters, where it was, as always, found in the morning.

Whenever I think about the preternatural intelligence of the octopus, sliding out of its tank to purloin a snack, I can’t help but smile.

I myself suffer from asthma. Once paramedics had to be summoned in the middle of the night because I couldn’t breathe. Not being able to breathe is most frightening sensation in the world. Imagine trying to pull piece of inner tube through a narrow pipe. That’s what asthma is like. I think of the octopus, trying to breathe, its audacious will to survive forcing it to climb a tightrope that will only lead it to an even more inhospitable world. No paramedics will force an oxygen tube down its throat and save its life. We’re the ones responsible for its breathing, and for its suffocation.