Underwater volcanoes, Great Lakes pollution, subseafloor life, more
NARRAGANSETT, R.I. – December 15, 2014 — The following research is among more than 40 projects that will be presented by scientists from the University of Rhode Island’s Graduate School of Oceanography at the American Geophysical Union’s fall meeting in San Francisco from Dec. 15 to 19:
Hydrothermal Venting at Kick’Em Jenny Submarine Volcano
The Kick’Em Jenny underwater volcano is the most active submarine volcano in the Caribbean. It erupts about every 10 years, but it has not done so since 2001, so scientists believe it is overdue. To determine its present state, URI Oceanography Professor Steven Carey led two investigations to the crater to collect water samples and take measurements of temperatures and gases from its hydrothermal vent system.
“It turns out that the gases bubbling out of the crater are almost pure carbon dioxide, which looks like it is contributing to acidification of the crater water,” Carey said. “It creates extremes of acidification that haven’t been observed at other hydrothermal sites. We wonder what kind of an effect it will have on the marine biological community.” Few large organisms were observed around the vents at Kick’Em Jenny, unlike at most other vent systems.
The researchers also found that the hydrothermal vent lacked the abundance of precious metals found at hydrothermal vents at mid-ocean ridges. Carey believes that because it is a lower temperature hydrothermal system, the minerals are being deposited subsurface rather than on the seafloor.
Radon and radium in the ice-covered Arctic Ocean, and what they reveal about gas exchange in the sea ice zone
Carbon dioxide and other gases are continually moving from the atmosphere to the sea and back again. Since the Industrial Revolution, the ocean has absorbed more carbon dioxide than it gives off; in total, about 35 percent of human-emitted carbon dioxide has been absorbed by the ocean. It is well understood that this gas exchange is driven by turbulence at the ocean surface. In the open ocean, this turbulence comes primarily from wind, but it is more complicated in polar regions where sea ice covers the ocean for much of the year. So URI Assistant Professor Brice Loose collected data on a Canadian icebreaker to determine the gas exchange rate in the sea ice zone.
“Sea ice blocks direct air-sea gas exchange, but it is also a source of turbulence. Imagine a flotilla of barges being dragged around by the wind and the water. This produces a lot of turbulence,” he said. “A multitude of other processes, such as water freezing and melting, also affect gas exchange. It’s not as simple as in the open ocean.”
Loose and colleagues estimated the gas exchange rate using the natural production of radon in the ocean. Radon is produced by the radioactive decay of radium, and scientists can compare the abundance of radon to radium – any difference in abundance is due to gas exchange. “We’re developing models of all of the processes that produce turbulence and influence the gas exchange rate,” he said. “If you don’t account for these other factors, it is possible to underestimate gas by almost half in some conditions and overestimate it by a lot in other conditions.”
Energetic Constraints of Subseafloor Life
Food is extremely scarce in subseafloor sediments, so microbial respiration rates are orders of magnitude slower there than in the surface world. And yet microorganisms have co-existed for millions of years in sediments hundreds of meters deep. According to Steven D’Hondt, URI professor of oceanography, the simplest explanation for their co-existence is that the various microbes are not competing with each other.
“We hypothesize that these organisms are actually cooperating with each other. They use different oxidation pathways that remove each others’ reaction products,” he said. “This allows them to live at an energetic minimum wage for millions of years.”
Based on measurements of pore water chemistry from several sediment coring expeditions, D’Hondt concludes that the microbes use so little energy that there is likely very little reproduction taking place. Instead, the microbes use all of the available energy for repairing and maintaining their cells. “This opens the possibility that the organisms may live for millions of years,” he said.
Air-Water Exchange of Legacy and Emerging Organic Pollutants across the Great Lakes
Measurements of organic pollutants in the air and water around Lake Erie and Lake Ontario have revealed that airborne emissions are no longer the primary cause of the lakes’ contamination. Instead, most of the lakes’ chemical pollutants come from sources on land or in rivers.
According to Rainer Lohmann, URI professor of chemical oceanography, water quality in the Great Lakes has been slowly improving for many years. Historic studies of the lakes have usually pointed to atmospheric deposition as the primary cause of pollution in the lakes – from industrial emissions, motor vehicle exhausts and related sources. But as air pollution has decreased, Lohmann has found a shift in the source of Great Lakes chemical pollutants.
“Some contaminants still come from the atmosphere, but it is now mostly from wastewater plants, contaminated industrial sites and inputs from major rivers,” Lohmann said. “It’s quite a bad mix, but it’s getting better.”