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Ocean Research


June 2013 Issue

Oxygen Content of Sand May Affect Oil Breakdown in Seabed
The Gulf of Mexico Research Initiative (GoMRI) has investigated the effects of dispersants on the movement of crude oil through water-saturated marine sand and found that dispersants potentially facilitate penetration of oil components into the seabed, where oxygen concentrations may affect the degradation of the oil.

Experiments using sand-filled columns ranging from 10 to 50 centimeters in length found that the addition of dispersants caused hydrocarbons such as oil to penetrate deeper into sediment layers and potentially extend the time the hydrocarbons stay in the environment.

Based on these experiments, researchers postulate the deeper penetration of hydrocarbons may slow their degradation due to a decrease in oxygen in deeper sediment layers and, thus, extend the time the hydrocarbons remain in the environment. However, in fully oxygenated sand, a deeper penetration may increase the number of microbes involved in the biodegradation and decomposition of the hydrocarbons.

Researchers also concluded from the experiments that the presence of dispersants allow oil components to permeate faster and deeper into sands.

“There is relatively little information on the effects of dispersants on oil deposition and transport in water-saturated sandy sediments,” said Florida State University researcher Markus Huettel. “This study shows that the use of dispersants can potentially have both positive and negative impacts, depending on the oxygen content of the sand.”

Huettel is among a number of GoMRI scientists studying the impact of the Deepwater Horizon oil spill.

AWI Does Field Research in Tundra With Help of Samoylov
The Alfred Wegener Institute (AWI), Helmholtz Centre for Polar and Marine Research is conducting a multiweek spring expedition to the Lena Delta to study the interaction between the atmosphere, snow cover and the tundra. They are making use of the new Russian research station Samoylov.

The AWI permafrost researchers seek to understand how heat from the atmosphere penetrates the ground. They will examine closely how the snow distributes on the island; the profile, thickness and crystal structure of the snow blanket; and how the thawing process functions.

This research is intended to improve understanding of the physical processes in the permafrost soil and to enable more precise prediction of the future development of the tundra.

Ancient Plankton Show Sensitivity to Climate, Humans
The Woods Hole Oceanographic Institution (WHOI) has mined vast amounts of genetic data from the Black Sea sediment record, which shows the variety of past plankton species that left behind their genetic makeup (i.e., the plankton paleome).

The semi-isolated Black Sea is highly sensitive to climate-driven environmental changes, and the underlying sediments represent high-resolution archives of past continental climate and concurrent hydrologic changes in the basin.

The dynamics of the environmental changes from the Late Glacial into the Holocene (last 10,000 years) remain a matter of debate, and information on how these changes affected the plankton ecology of the Black Sea is sparse.

Using a combination of advanced ancient DNA techniques and tools to reconstruct the past climate, researchers have determined how communities of plankton have responded to changes in climate and the influence of humans over the last 11,400 years.

Specifically, researchers used DNA pyrosequencing to look for the overall plankton changes in the Black Sea from deglaciation to recent times. Pyrosequencing of ancient DNA signatures allows reconstruction of a large part of ancient oceanic life, including organisms that are not preserved as fossils.

Researchers also reconstructed past changes in salinity and temperature as the possible causes for plankton community shifts in the Black Sea.

To reconstruct the salinity, WHOI analyzed sediments containing highly resistant organic compounds called alkenones, which are uniquely produced by Emiliania huxleyi—the same photosynthetic organism oceanographers study to determine past sea surface temperatures. By examining the ratio of two hydrogen isotopes in the alkenones, researchers were able to map the salinity trend in the Black Sea over the last 6,500 years.

The study revealed that 150 of 2,710 identified plankton showed a statistically significant response to four environmental stages since deglaciation. The most drastic changes in plankton occurred over the last century, associated with recent human disturbances in the region.

The new findings show how sensitive marine ecosystems are to climate and human impact.

Midocean Ridges Found Not to Increase Biological Productivity
Midocean seamounts and ridges have been viewed as areas where marine life is plentiful, compared with other offshore regions, making them attractive to commercial fisheries.

An eight-year study, published in PLOS ONE, of the Mid-Atlantic Ridge, the world’s longest mountain range, rising 3,500 meters from the floor of the Atlantic Ocean, used a range of sampling techniques and satellite imagery to study marine life in the Charlie-Gibbs Fracture Zone, where two vast canyons cut across the ridge. Many animals such as birds, dolphins and whales feed here.

The ridge effectively compresses marine life together into a thin layer, so that the attaching animals, such as corals, sponges and sea lilies, the burrowing and crawling animals, such as worms, sea cucumbers, brittle stars, star fish, crabs and sea spiders, as well as the swimming animals, such as fish, all crowd over the summits, slope and terraces that make up the ridge.

  If there were no ridge, there would be different animals, such as free-floating and swimming creatures, including deep-sea luminescent fishes, jellies, krill and squid, which would be distributed throughout 3.5 kilometers water depth, the researchers said.

They argue that the ridge does not increase biological productivity of the midocean, a point they believe should be considered when fishing in these areas.


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