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August 2016 Issue

Acoustic Camera Monitors
Marine Animals

Halfway between Hawaii and American Samoa lies a group of small islands and inlets. Among them is Palmyra Atoll, an almost 5-sq-mi. ring of coral.

The lagoons of Palmyra, part of the Pacific Remote Islands Marine National Monument, provide sanctuary for a variety of mobile species including sharks, manta rays and turtles.

In a new study, UC Santa Barbara marine biologists applied existing technology in a novel way to monitor animals coming into and going out of a lagoon via a deep channel dredged during World War II. Their work confirmed that the route was an important “highway” for sharks and highlighted the magnitude of their channel usage. It also highlighted the time of day when shark traffic peaks. It turns out rush hour for sharks is between 7 and 8 p.m.

The researchers used dual-frequency identification sonar, an acoustic camera originally designed for the U.S. Navy by Sound Metrics Corp., to create a sound gate through which the sharks traveled. Marine animal traffic was monitored for 443 hr. for a month.

Acoustic cameras use sonar technology to produce fast-frame, detailed imaging even in low-light, turbid environments. The results surpass the range capture and clarity of traditional optical cameras.


Studying Leak Risk
Of Carbon Reservoirs

Southampton researchers are playing a key role investigating the risks of leaks from carbon dioxide storage reservoirs situated under the seabed. Academics from the University of Southampton will work with colleagues at the University of Edinburgh and the National Oceanography Centre Southampton (NOCS) on a NERC-funded project to understand the risks involved in the storage of carbon dioxide in depleted oil and gas reservoirs and saline aquifers in the North Sea.

A key element in the safety of such storage is to fully understand the risks of any leakage. The location and potential size of any possible carbon dioxide leakage at the seafloor is critically dependent on the distribution and permeability of fluid pathways in the marine sediments overlying any proposed storage reservoir.

The four-year project aims to develop better techniques to locate these subseafloor structures and determine the permeability of the pathways so that they can be better constrained and quantified.

Among other equipment specified for the project, the Applied Acoustics’ DTS-500 deep-tow sparker will be used to survey the geology beneath the seabed to determine, in high resolution, the geophysical stratigraphy of the sedimentary basins.


Free AZFP Use for
Renewables Study

An ASL Acoustic Zooplankton Fish Profiler (AZFP) will be deployed in the strong tidal waters off the coast of Wales, free of charge as the result of a successful application to ASL’s AZFP Award Program for early-career scientists.

Dr. Timothy Whitton from the Centre for Applied Marine Sciences at Bangor University won for his proposed study on the biological processes in areas of marine renewable energy development. Whitton will get the use of a 125-, 200-, 455- and 769-kHz instrument for four months starting September 2016 to conduct his research. This will progress research conducted by him during the SEACAMS project that collaborated with the Welsh marine renewable sector.

The wide range of frequencies on the AFZP will allow the observation of fish, zooplankton and even sediments.


Soft Rock Allows
Smooth Plate Tectonics

Detailed recordings of earthquakes on ultraslow midocean ridges are being made for the first time. The earthquake distribution on ultraslow midocean ridges differs fundamentally from other spreading zones. Water circulating at a depth up to 15 km leads to the formation of rock that resembles soft soap. This is how the continental plates on ultraslow midocean ridges may move without jerking, while the same process in other regions leads to many minor earthquakes, according to geophysicists of the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI).

Ultraslow ridges can be found under the sea ice in the Arctic and south of Africa along the Southwest Indian Ridge in the notorious sea areas of the Roaring Forties and Furious Fifties. Because these areas are so difficult to access, earthquakes have not been measured there. Until now, little was known about the structure and development of about 20 percent of the global seabed.


Mars May Have Had
Oxygen-Rich Past

The discovery of manganese oxides in Martian rocks might tell us that the Red Planet was once more Earth-like than previously believed. AGU reported that a new study reveals NASA’s Curiosity rover observed high levels of manganese oxides in Martian rocks, which could indicate higher levels of atmospheric oxygen once existed there. This hint of more oxygen in Mars’ early atmosphere adds to other Curiosity findings—such as evidence of ancient lakes—revealing how Earth-like Mars once was.

These high-manganese materials can’t form without lots of liquid water and strongly oxidizing conditions. Earth had lots of water but no widespread deposits of manganese oxides until after the oxygen levels in our atmosphere rose due to photosynthesizing microbes.

In Earth’s geological record, the appearance of high concentrations of manganese is an important marker of a major shift in our atmosphere’s composition, from relatively low oxygen abundances to the oxygen-rich atmosphere we see today. The presence of the same types of materials on Mars suggests something similar happened there.

The Los Alamos-developed ChemCam instrument that sits atop Curiosity was used to “zap” rocks on Mars and analyze their chemical make-up for this study. In less than four years since landing on Mars, ChemCam has analyzed roughly 1,500 rock and soil samples.



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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.