Home | Contact ST  



Marine Resources

2012:  JAN | FEB | MARCH | APRIL | MAY | JUNE | JULY | AUG | SEPT | OCT | NOV | DEC
2011:  JAN | FEB | MARCH | APRIL | MAY | JUNE | JULY | AUG | SEPT | OCT | NOV | DEC

May 2011 Issue

Antarctic Icebergs Play Role in Carbon Cycle, Research Finds
Icebergs cool and dilute the ocean water they pass through and also affect the of distribution carbon-dioxide-absorbing phytoplankton in the Southern Ocean, according to a team of researchers from University of California, San Diego, and the University of San Diego.

Scientists said the effects are likely to influence the growth of phytoplankton in the Atlantic sector of the Southern Ocean. Enhanced phytoplankton growth would increase the rate at which carbon dioxide is removed from the ocean, said the leaders of the study. The results were published in Deep-Sea Research II earlier this year.

The findings document a persistent change in physical and biological characteristics of surface waters after the transit of an iceberg. The change in surface water properties such as salinity lasted at least 10 days, far longer than scientists said they expected.

Sampling was conducted by a surface-mapping method used to survey the area around an iceberg more than 32 kilometers long. The team surveyed the same area again 10 days later, after the iceberg had drifted away, and observed increased concentrations of chlorophyll a and reduced concentrations of carbon dioxide compared to nearby areas without icebergs. For more information, visit www.nsf.gov.

Massive Trauma Found in Squid, Octopus from Ocean Noise
Noise pollution in the oceans, such as from large-scale offshore activities, has already been shown to cause physical and behavioral changes in marine life, especially in dolphins and whales. New research has found low-frequency sound causes harm to other marine life as well.

Michel André from the Technical University of Catalonia in Barcelona and his colleagues examined the effects of low-frequency sound exposure in four cephalopod species. All of the exposed squid, octopus and cuttlefish species tested exhibited massive acoustic trauma in the form of severe lesions in their auditory structures, as reported in April in Frontiers in Ecology and the Environment.

The researchers exposed 87 individual cephalopods to short sweeps of relatively low-intensity, low-frequency sound between 50 and 400 hertz and examined their statocysts, the fluid-filled, balloon-like structures that help these invertebrates maintain balance and position. The scientists' results confirmed that statocysts indeed play a role in perceiving low-frequency sound in cephalopods.

They also found that, immediately following exposure to low-frequency sound, the cephalopods showed hair cell damage within the statocysts. Over time, nerve fibers became swollen and, eventually, large holes appeared. All of the individuals exposed to the sound showed evidence of acoustic trauma, compared with unexposed individuals that did not show any damage.

With increasing offshore drilling, cargo ship transportation, excavation and other large-scale, offshore activities, the scientists said it is becoming more likely that these activities will overlap with migratory routes and areas frequented by marine life. For more information, visit www.sciencedaily.com.

Eyes of Aragonite Let Simple Mollusks See Predators
Using eyes made of a calcium carbonate crystal, a simple mollusk may have evolved enough vision to spot potential predators, scientists say.

Lead author Daniel Speiser, a postdoctoral fellow at University of California, Santa Barbara, published the results in April in Current Biology.

The three-inch-long mollusks, called chitons, have hundreds of eye-like structures with lenses made of aragonite, which cover clusters of light-sensitive cells beneath. It's the first time scientists have found an animal that makes eye lenses from aragonite and not calcite.

Scientists discovered the chiton's unique eyes decades ago, but it wasn't clear whether chitons used these eyes to see objects overhead or simply to sense changes in light.

To test the creature's vision, Speiser placed individual chitons on a slate slab. When left undisturbed, they lift part of their armored, oval-shaped body to breathe. Speiser then showed them either a black disk ranging from 0.35 centimeters to 10 centimeters in diameter or a corresponding gray slide that blocked the same amount of light.

When shown the gray screens, the chitons did not respond. But they clamped down when shown a black disk three centimeters or larger in diameter. Because they responded to the larger disks and not the gray slides, they seem to be seeing the disk and not simply responding to a change in light, said University of Sussex biologist Michael Land, an expert on animal vision not involved in the research. For more information, visit www.sciencedaily.com.

2,000-Year-Old Black Corals Found Deep in Gulf of Mexico
For the first time, scientists have been able to validate the age of deep-sea black corals in the Gulf of Mexico. They found the gulf is home to 2,000-year-old deep-sea black corals, many of which are only a few feet tall.

These slow-growing, long-living animals thrive in very deep waters—300 meters and deeper.

"The fact that the animals live continuously for thousands of years amazes me," said Dr. Nancy Prouty of the U.S. Geological Survey (USGS) Pacific Coastal and Marine Science Center. Prouty analyzed the coral samples that were collected by the USGS and colleagues as part of several ongoing deep-sea coral ecosystem studies between 2003 and 2009.

Scientists used the manipulator arms on the manned submersible Johnson-Sea-Link to collect samples from the gulf sea floor. The skeletons that these animals secrete continuously over hundreds to thousands of years offer a window into past environmental conditions, scientists said.

Scientists confirmed that black corals are the slowest growing deep-sea corals. They grow eight to 22 micrometers per year, as compared to the shallow-water reef-building coral often found in the tropics, which grow about one millimeter per year, or 65 times as fast as black coral. For more information, visit www.usgs.gov.


2012:  JAN | FEB | MARCH | APRIL | MAY | JUNE | JULY | AUG | SEPT | OCT | NOV | DEC
2011:  JAN | FEB | MARCH | APRIL | MAY | JUNE | JULY | AUG | SEPT | OCT | NOV | DEC

-back to top-

Sea Technology is read worldwide in more than 110 countries by management, engineers, scientists and technical personnel working in industry, government and educational research institutions. Readers are involved with oceanographic research, fisheries management, offshore oil and gas exploration and production, undersea defense including antisubmarine warfare, ocean mining and commercial diving.