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Ocean Research


June 2015 Issue

Pocket Shark Discovery In Gulf of Mexico
A BOEM-NOAA study of Gulf of Mexico sperm whales has led to the discovery of a 5.5-inch pocket shark (Mollisquama sp.), a very rare species. The only other known specimen (Mollisquama parini) was found off the Peruvian/Chilean coast 36 years ago.

The pocket shark is named for a mysterious pocket-like orifice behind its pectoral fin.

NOAA Fisheries Pascagoula Lab fisheries biologist Mark Grace made the discovery in 2013 while conducting a long-term analysis of more than 3,500 deep-sea samples collected from a 2010 BOEM-NOAA Gulf of Mexico sperm whale acoustic prey survey. The specimen is being studied by the science community, including the American Museum of Natural History in New York, New York, and the Smithsonian National Museum of Natural History. It will be permanently archived at Tulane University’s Biodiversity Research Institute.

Arctic Cod Spawned Successfully in Lab
NOAA Fisheries scientists have successfully spawned and hatched Arctic cod in a laboratory, representing another step forward toward understanding how these bellwether fish in the Arctic marine ecosystem may fare with a warming ocean and climate change. It also opens up a new frontier to study cod development in a laboratory setting. Up until now, this type of research was restricted to the short, ice-free summer period in the Arctic.

Arctic cod are a key component of the Arctic marine ecosystem as an important food source for seabirds, ringed seals, narwhals, belugas and other fish.

New research shows that Arctic cod may be the most vulnerable to warming ocean waters.

In general, Arctic marine species require colder water to survive than populations further south, but determining just how cold is tricky and requires specialized laboratory space to simulate the Arctic environment.

Plus, there are sometimes big surprises. Saffron cod, another species of cod in the Arctic, can grow and survive well in water temperatures as high as 20° C. This suggests that there will be both winners and losers as the Arctic continues to warm.

West Antarctic Ice Core Shows Historical Climate Link
A new study using evidence from a highly detailed ice core from West Antarctica shows a consistent link between abrupt temperature changes on Greenland and Antarctica during the last ice age.

Greenland climate during the last ice age was very unstable, characterized by a number of large, abrupt changes in mean annual temperature that each occurred within several decades. These so-called “Dansgaard-Oeschger events” took place every few thousand years during the last ice age. Temperature changes in Antarctica showed an opposite pattern, with Antarctica cooling when Greenland was warm, and vice versa.

In this study, published in Nature, the researchers discovered that the abrupt climate changes show up first in Greenland, with the Antarctic climate response delayed by about 200 years. The researchers documented 18 abrupt climate events during the past 68,000 years.

The abrupt events of the ice age were regional in scope and likely tied to large-scale changes in ocean circulation. Warming today is global and primarily from human carbon dioxide emissions in the Earth’s atmosphere.

The key to the discovery was the analysis of a new ice core from West Antarctica, drilled to a depth of 3,405 meters and spanning the last 68,000 years.

Pond Water as Potential Source for Algal Symbionts
The authors of an article published in Phycologia investigated the possibility of environmental symbiont acquisition on yellow spotted salamanders and their symbionts, a type of single-celled green algae called Oophila (“egg lover”) amblystomatis.

The authors collected undisturbed pond water from previously identified salamander breeding habitat, filtered it, extracted DNA, then sequenced and analyzed the DNA.

They found that the pond water contained free-living cells whose DNA sequences were identical, or nearly identical, to those sequences from green algae harvested directly from egg masses. These pond-dwelling algae were present both before and after the salamanders laid their eggs. Therefore, the pond water can be considered a potential source of the algal symbionts.

Microseismic Waves Cause Earth to Oscillate
Earthquakes can cause the Earth to oscillate, or ring, for days or months, but the planet constantly vibrates at very low frequencies, even when there are no earthquakes. This ever-present background tremor is able to be detected only by sensitive seismic instruments.

One theory for the continuous tremor suggests it’s generated by ocean waves moving in opposite directions. When the waves collide, they create very weak, microseismic waves that add up to a generalized ringing.

A group of French researchers have now tested this theory by using models to calculate how ocean waves could generate seismic waves. They found that opposing ocean waves could initiate a particular kind of seismic wave that takes 13 seconds or less to complete one oscillation.

But, when it came to even slower oscillating seismic waves, the theory did not hold up. These very slow waves, with periods greater than 50 seconds, are at the heart of the planet’s bell-like resonance.

Another theory suggests the movement of ocean waves over the bottom of the ocean generates these slower oscillating, very long waves. As they make their way back and forth to the open ocean from the coast, the pressure of these waves on the seafloor generates seismic waves that cause the Earth to oscillate. Researchers found this theory could explain the longer microseismic signals, ranging up to 300 seconds.

The researchers concluded that both theories are needed—one to explain the shorter seismic waves and another to explain the longer seismic waves responsible for the Earth’s hum.

The results were published in Geophysical Research Letters.


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