Altering the Abyss: Deep-Sea Ecosystems Affected By Climate Change

The abyssal plains, regions of the ocean below 2000 meters, cover 60% of the Earth’s surface. Scientists have long believed that the ecosystems located at these depths are relatively isolated and stable, immune to the dramatic changes rocking shallower ocean regions due to global warming. However, a recent paper* by Ken Smith, a marine ecologist at the Monterey Bay Aquarium Research Institute (MBARI) and his colleagues, suggests that changes in the Earth’s climate can cause unexpectedly large changes in the deep-sea.

Smith conducted a time-series study at two deep-sea stations: one located 220 km off the Central California coast, the other on the Porcupine Abyssal Plain, several hundred km southwest of Ireland. The seafloor at these sites is a flat, muddy plain that lies between 4000 and 5000 m below the surface. The small amount of food available at these depths takes the form of tiny bits of organic debris that drift down from the surface. The amount varies over time. Over the period of the study, two of the dramatic changes that researchers observed were the doubling from 1989 to 2004 of the grenadiers, an important Pacific seafloor fish and the virtually disappearance of a common species of sea cucumber after 1998. Scientists speculate that both of these events were linked to changes at the surface, such as El Nino and commercial fishing, which may have affected the availability of food.

A grenadier, an important deep-sea fish.
A small grenadier fish swims over the seafloor at Station M off Central California. Image © 2007 MBARI

“Essentially, deep-sea communities are coupled to surface production,” said Smith. “Global change could alter the functioning of these ecosystems and the way that carbon is cycled in the oceans.” However, deep-sea carbon cycling is left out of most climate models. This could be corrected using remote, automated monitoring technologies, including seafloor moorings and robots that could provide continuous data about short- and long-term changes in deep-sea ecosystems.

For more on Smith’s abyssal time series research, check out his website.

A study published earlier this year by MBARI researchers Peter Brewer and Edward Peltzer in the journal Science** suggests another way that deep-sea life may be affected by climate change. The combination of increasing carbon dioxide and decreasing oxygen concentrations brought on by increasing GHG emissions may make it harder for organisms to “breathe” – extract oxygen from the water around them.

And while I’m touting MBARI’s excellent science and deep-sea discoveries, check out this bizarre fish, the barreleye, with tubular eyes and a transparent head!

Other recent MBARI news: microbiologist and harmful algal bloom (HAB) specialist Chris Scholin has been appointed President and CEO of the Monterey Bay Aquarium Research Institute (MBARI). I got to know Chris when I ran a grants program for HAB research at NOAA and can say that MBARI is in excellent hands.

* Smith, K.L., Jr., H.A. Ruhl, B.J. Bett, D.S.M. Billett, R.S. Lampitt and R.S. Kaufmann (2009) Climate, carbon cycling, and deep-ocean ecosystems. Proceedings of the National Academy of Sciences 106: 19211-19218.

** P. G. Brewer, E. T. Peltzer. Limits to marine life. Science. 2009. Vol 324, Issue 5925. April 17, 2009.


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