Thursday, July 22, 2010
The first expedition to search for deep-sea hydrothermal vents along the Mid-Cayman Rise has turned up three distinct types of hydrothermal venting, reports an interdisciplinary team led by Woods Hole Oceanographic Institution (WHOI) in this week's Proceedings of the National Academy of Sciences. The work was conducted as part of a NASA-funded effort to search extreme environments for geologic, biologic, and chemical clues to the origins and evolution of life.Hydrothermal activity occurs on spreading centers all around the world. However, the diversity of the newly discovered vent types, their geologic settings and their relative geographic isolation make the Mid-Cayman Rise a unique environment in the world's ocean."This was probably the highest risk expedition I have ever undertaken," said chief scientist Chris German, a WHOI geochemist who has pioneered the use of autonomous underwater vehicles (AUVs) to search for hydrothermal vent sites. "We know hydrothermal vents appear along ridges approximately every 100 km. But this ridge crest is only 100 km long, so we should only have expected to find evidence for one site at most. So finding evidence for three sites was quite unexpected -- but then finding out that our data indicated that each site represents a different style of venting -- one of every kind known, all in pretty much the same place -- was extraordinarily cool."The Mid-Cayman Rise (MCR) is an ultraslow spreading ridge located in the Cayman Trough -- the deepest point in the Caribbean Sea and a part of the tectonic boundary between the North American Plate and the Caribbean Plate. At the boundary where the plates are being pulled apart, new material wells up from Earth's interior to form new crust on the seafloor.The team identified the deepest known hydrothermal vent site and two additional distinct types of vents, one of which is believed to be a shallow, low temperature vent of a kind that has been reported only once previously -- at the "Lost City" site in the mid-Atlantic ocean."Being the deepest, these hydrothermal vents support communities of organisms that are the furthest from the ocean surface and sources of energy like sunlight," said co-author Max Coleman of NASA's Jet Propulsion Laboratory, Pasadena, Calif. "Most life on Earth is sustained by food chains that begin with sunlight as their energy source. That's not an option for possible life deep in the ocean of Jupiter's icy moon Europa, prioritized by NASA for future exploration. However, organisms around the deep vents get energy from the chemicals in hydrothermal fluid, a scenario we think is similar to the seafloor of Europa, and this work will help us understand what we might find when we search for life there."While vent sites occupy small areas on the sea floor, the plumes formed when hot acidic vent fluids mix with cold deep-ocean seawater can rise hundreds of meters until they reach neutral buoyancy. Because these plumes contain dissolved chemicals, particulate minerals and microbes, they can then be detected for kilometers or more away from their source as they disperse horizontally in the ocean. The chemical signatures of these plumes vary according to the type of vent site from which they originated.The three known types of vent sites are distinguished by the kinds of rock that host the sites. The first type of vents occur throughout the world's mid-ocean ridges and are hosted by rocks that are rich in magnesium and iron --called mafic rocks. The second and third types of vent sites are hosted in rocks called ultramafic that form deep below the seafloor and are composed of material similar to the much hotter lavas that erupted on Earth's very earliest seafloor, thousands of millions of years ago.The discovery of ultramafic-hosted vent sites such as those on the Mid-Cayman Rise could provide insight into the very earliest life on our planet and the potential for similar life to become established elsewhere," said German.For this mission, German and his colleagues used the plumes in the search for hydrothermal vents, employing sensors mounted on equipment and robotic vehicles to track the chemicals back to their source. This expedition used a CTD (conductivity, temperature, and depth) array augmented with sensors to detect suspended particles and anomalous chemical compositions (the latter sensor courtesy of Ko-ichi Nakamura from AIST in Tsukuba, Japan) mounted on both a water sampling rosette and the hybrid vehicle Nereus, a deep-diving robot that can operate in both in tethered and free-swimming modes.Using the CTDs and Nereus in "autonomous" or free-swimming mode, the team sniffed out deep-sea plumes originating from the seafloor hydrothermal vents. Using a combination of shipboard and shore-based analyses of water samples for both their chemical and microbial contents, the team was then able to track the plumes toward their sources as well as to determine the likely nature of the venting present at each site. The ultimate goal was to switch Nereus into tethered or "remotely operated" (ROV) mode during the latter stages of the cruise and dive on each vent site to collect samples using Nereus' robotic manipulator arm."Part of the excitement of this NASA-funded project was the success of deploying a full-ocean-capable tethered vehicle to search for vents at 5000 m from the R/V Cape Hatteras, which, at 41 meters in length, is one of the smallest ocean-going ships in the national fleet. This is a first," said Cindy Lee Van Dover, co-author on the study and director of the Duke University Marine Laboratory.The first two sites the team identified are extremely deep and were named Piccard and Walsh in honor of the only two humans to dive to the Challenger Deep -- the deepest part of the world's ocean. The plume detected at the Piccard site -- 800 meters deeper than the previously known deepest vent -- was comparable to plumes from the "Type 1" vent sites, first found in the Pacific Ocean in 1977."We were particularly excited to find compelling evidence for high-temperature venting at almost 5000m depth. We have absolutely zero microbial data from high-temperature vents at this depth," said Julie Huber, a scientist in the Josephine Bay Paul Center at the Marine Biological Laboratory (MBL) in Woods Hole. Huber and MBL postdoctoral scientist Julie Smith participated in this cruise to collect samples, and all of the microbiology work for this paper was carried out in Huber's laboratory. "With the combination of extreme pressure, temperature, and chemistry, we are sure to discover novel microbes in this environment," Huber added. "We look forward to returning to the Cayman and sampling these vents in the near future. We are sure to expand the known growth parameters and limits for life on our planet by exploring these new sites."The Walsh plume also exhibited signals characteristic of a high temperature site, but with a chemical composition (notably the high methane-to-manganese ratio) typically found at a high temperature, ultramafic hosted "Type 2" vent site. The third site- which the team have named Europa, after the moon of Jupiter -- most closely resembles the "Lost City" vent site in the mid-Atlantic ocean -- to date the only confirmed low-temperature "Type 3" site.Half way through the six-day leg in which Nereus was converted into ROV mode, tropical storm Ida intervened and stopped the team from viewing or sampling the vent site. Though they had come within 250m of the vents at the seafloor, they had to ride out the storm for the last three days of the cruise and return to port frustrated. Happily, however, all was not lost the research team shared their findings with an international team led by Jon Copley of the National Oceanography Centre in Southampton, UK, who returned to the MCR in Spring 2010 and imaged active vents at both the Piccard and Europa locations using a deep-towed camera called Hybis."Given the range and diversity of systems present, and now that we have established exactly where the sites are and what they look like, we really can't wait to get back and collect first samples with our ROV Jason," said German. "This region has the potential to develop into an exciting natural laboratory with plenty of potential for repeat visits and long-term experiments over the decade ahead."By exploring this extreme and previously uninvestigated section of the Earth's deep seafloor, the researchers seek to extend our understanding of the limits to which life can exist on Earth and to help prepare for future efforts to explore for life on other planets.
Just as the growing numbers of cars on the road cause traffic "chokepoints," more ships traversing northern passageways can choke maritime traffic. These maritime traffic snarls occur when nautical charts are outdated, ships do not have sufficient information for navigation or changing maritime conditions -- like sea level rise or movements of the seafloor -- are not tracked.
"We have seen a substantial increase in activity in the region and ships are operating with woefully outdated charts," said Sen. Lisa Murkowski of Alaska. "I have introduced legislation that authorizes a significant increase in funding for mapping the Arctic, and I am pleased to see NOAA beginning the process. While this is a good start, we still need more resources to adequately map this region."
"Commercial shippers aren't the only ones needing assurances of safety in new trade routes," notes Captain John Lowell, director of NOAA's Office of Coast Survey. "The additional potential for passenger cruises, commercial fishing and other economic activities add to pressures for adequate response to navigational risks."
The U.S. Exclusive Economic Zone includes 568,000 square nautical miles of U.S. Arctic waters. The majority of charted Arctic waters were surveyed with obsolete technology dating back to the 1800s. Most of the shoreline along Alaska's northern and western coasts has not been mapped since 1960, if ever, and confidence in the region's nautical charts is extremely low.
"In Alaska we are seeing the effects of climate change more rapidly than anywhere else in the U.S.," said Sen. Mark Begich of Alaska. "As Arctic sea ice recedes, economic activity in the region is going to expand dramatically. Alaskans rely on NOAA to help us make sure that things like oil and gas development and marine transportation are done safely and responsibly. The 21st century mapping technology the Ketchikan-based Fairweather brings to this important charting mission is a great example of what the federal government needs to do as activity in the Arctic grows."
About a third of U.S. Arctic waters are considered navigationally significant. Of that area, NOAA's Office of Coast Survey has identified 38,000 square nautical miles as survey priorities. NOAA estimates that it will take well more than 25 years to map the prioritized areas of the Arctic seafloor.
"President Thomas Jefferson ordered a survey of the East Coast in 1807, when our country was losing more ships to unsafe navigation than to war," explains Capt. David Neander, commanding officer of the Fairweather. "Today, we have better maps of the moon than of our own oceans. Our46-person crew is amassing ocean data that directly affects our economy and our ecosystems."
The vessel is equipped with the latest in hydrographic survey technology -- multi-beam survey systems; high-speed, high-resolution side-scan sonar; position and orientation systems; hydrographic survey launches; and an on-board data-processing server.
Fairweather is part of the NOAA fleet of ships and aircraft operated, managed and maintained by NOAA's Office of Marine and Aviation Operations, which includes commissioned officers of the NOAA Corps and civilian wage mariners.
Updated charts for commercial and recreational navigation are available on Coast Survey's Web site, http://www.nauticalcharts.noaa.gov/.
Wednesday, July 21, 2010
What is more, the orcas seem to be particularly choosy about which bits of the penguins they eat; being inclined to take only the best cuts of penguin breast meat.
Details are published in Polar Biology.
They seemed to be mainly interested in eating just the breast muscles, rather like humans would do
Marine biologist Dr Robert Pitman
Marine biologists Dr Robert Pitman and Dr John Durban of the US National Marine Fisheries Service based in La Jolla, California, made the discovery while researching orca foraging behaviour around the Antarctic peninsula.
"We had expected to see killer whales taking Antarctic minke whales and seals, which we did," Dr Pitman told the BBC.
"But we were quite surprised to find them catching penguins also."
Three type of orca are known to live in Antarctic waters, each differing in size, colouration and the prey they hunt.
Type A orcas are the largest, are black and white and look most like orcas found elsewhere in the world. Type As hunt minke whales.
Type B orcas are smaller and have a yellow tinge. They also prey on minke and perhaps humpback whales but tend to prefer to hunt seals.
Type C orcas are also smaller, with different markings, and prefer to live within inshore waters and among the pack ice, and to date have been recorded only feeding on Antarctic toothfish.
Biologists have long questioned whether any of these orcas take penguins, which are also abundant on the continent, but until now there has been no evidence.
That was until Drs Pitman and Durban witnessed several instances of predation on two different species of penguins: chinstraps and gentoos.
The attacks occurred over three separate days, and were instigated by type B orcas, with some evidence that type A orcas may also have hunted and fed on a penguin.
During each attack the orcas chased a penguin, which porpoised out of the water and erratically changed direction under water in a bid to avoid capture.
Surprisingly, when the orcas did catch a penguin, they often refrained from eating the whole bird.
"We were surprised to find killer whales eating 4 to 6kg penguins, and even more surprised to find that they seemed to be mainly interested in eating just the breast muscles, rather like humans would do," says Dr Pitman.
Often the orcas handled their prey with meticulous care, removing skin and feathers to expose the breast muscle, sonetimes working cooperatively to do so.
The breast tissue may be particularly nutritious, but it is still unclear how much nutritional benefit a 3000kg orca would get eating selective cuts of a penguin weighing just a few kilograms.
"Penguins have enormous breast muscles to power winged flight through the water, but it is still a small part of an already small prey item. It would be like us chasing around after individual peanuts," says Dr Pitman.
"Ours is the first clear documentation of penguin predation in Antarctic waters but we don't know how commonly it occurs."
If it is common, then predation by orcas could have a significant impact on penguin populations in Antarctica.
In the past, biologists have suspected that orcas may have been responsible for a 50% decline in numbers of emperor penguins residing at Adelie Land, eastern Antarctica during the 1970s.
But no penguin remains were found inside the stomachs of orcas in the area.
The observations of Dr Pitman and Durban, however, suggest that these whales may have also been fussy eaters, removing breast tissue and not bones, which would leave little trace in an orca's stomach. By Matt Walker
Tuesday, July 20, 2010
"Originally there were sardines in the area but over fishing caused the sardine population to collapse in the 1960s and 1970s," said Victoria A. Braithwaite, professor of fisheries and biology, Penn State. "The sardines never recovered and jellyfish became a huge and serious problem, eating what the sardines had eaten."
Jellyfish are considered a dead end food source because, while they eat lots of small fish and other sea creatures, they have few predators. However, the research team found that the bearded goby, Sufflogobius bibarbatus, a 4-to-6-inch long, 1.5 inch-wide fish, eats jellyfish. Larger fish like hake and mackerel, sea mammals like sea lions and porpoises, and sea birds, like gannets and gulls, eat gobies, putting jellyfish back into the food cycle.
"We don't know if they are eating dead jellyfish from the bottom, or if they are coming up to oxygen-filled layers to eat jellyfish, but they are eating jellyfish," said Braithwaite.
Even stranger than a jellyfish diet is the gobies' use of the dead zone in the area. One reason there were so many sardines and now so many jellyfish is a large area of up-welling water off the southwest coast of Africa from Namibia to South Africa. This deep cold water brings with it large amounts of nutrients. When plankton voraciously eat the nutrients, their populations increase massively. Excess nutrients and dead plankton then fall to the ocean floor.
"A horrible toxic sludge forms, and very few things can live in it except for some bacteria and nematodes," said Braithwaite. "Somehow the gobies can withstand the toxic environment, but we don't know exactly how they are doing it."
Remarkably, the gobies cope without oxygen for hours at a time while they rest on the muddy seabed but remain alert.
"When we touch them with a rod, they show rapid escape responses," said Braithwaite.
Gobies can stay in the anoxic or oxygen-depleted area for at least 10 to 12 hours at a time. The researchers suggest they may be able to remain there even longer. The mud is not just lacking oxygen, but the bacteria that live there use sulfur for energy and produce high levels of hydrogen sulfide, a toxic gas. The researchers report the results of their study in the journal Science.
"Normally, other animals cope with anoxia by anaerobic respiration, which causes a build up in lactate," said Braithwaite. "But something else is going on in these gobies as the lactate build up declines after an hour or so without oxygen. Our next step is to look to see what they are doing to cope with anoxia."
For the goby, the anoxic, toxic mud is a perfect hiding place because no predators are willing to enter that environment. The gobies, however, are happy fish in the mud.
"It is a win-win situation where the gobies are using a resource that is usually a dead end in the ocean, the jellyfish," said Braithwaite. "And they are using the toxic mud as a refuge. Together this seems to explain why their population is growing despite the fact that they are now being the main prey species in this unusual ecosystem."
Saturday, July 17, 2010
This analysis was published in the journal Ecology by Michael Behrenfeld, a professor of botany at Oregon State University, and one of the world's leading experts in the use of remote sensing technology to examine ocean productivity. The study was supported by NASA.
The new research concludes that a theory first developed in 1953 called the "critical depth hypothesis" offers an incomplete and inaccurate explanation for summer phytoplankton blooms that have been observed since the 1800s in the North Atlantic Ocean. These blooms provide the basis for one of the world's most productive fisheries.
"The old theory made common sense and seemed to explain what people were seeing," Behrenfeld said.
"It was based on the best science and data that were available at the time, most of which was obtained during the calmer seasons of late spring and early summer," he said. "But now we have satellite remote sensing technology that provides us with a much more comprehensive view of the oceans on literally a daily basis. And those data strongly contradict the critical depth hypothesis."
That hypothesis, commonly found in oceanographic textbooks, stated that phytoplankton bloom in temperate oceans in the spring because of improving light conditions -- longer and brighter days -- and warming of the surface layer. Warm water is less dense than cold water, so springtime warming creates a surface layer that essentially "floats" on top of the cold water below, slows wind-driven mixing and holds the phytoplankton in the sunlit upper layer more of the time, letting them grow faster.
There's a problem: a nine-year analysis of satellite records of chlorophyll and carbon data indicate that this long-held hypothesis is not true. The rate of phytoplankton accumulation actually begins to surge during the middle of winter, the coldest, darkest time of year.
The fundamental flaw of the previous theory, Behrenfeld said, is that it didn't adequately account for seasonal changes in the activity of the zooplankton -- very tiny marine animals -- in particular their feeding rate on the phytoplankton.
"To understand phytoplankton abundance, we've been paying way too much attention to phytoplankton growth and way too little attention to loss rates, particularly consumption by zooplankton," Behrenfeld said. "When zooplankton are abundant and can find food, they eat phytoplankton almost as fast as it grows."
The new theory that Behrenfeld has developed, called the "dilution-recoupling hypothesis," suggests that the spring bloom depends on processes occurring earlier in the fall and winter. As winter storms become more frequent and intense, the biologically-rich surface layer mixes with cold, almost clear and lifeless water from deeper levels. This dilutes the concentration of phytoplankton and zooplankton, making it more difficult for the zooplankton to find the phytoplankton and eat them -- so more phytoplankton survive and populations begin to increase during the dark, cold days of winter.
In the spring, storms subside and the phytoplankton and zooplankton are no longer regularly diluted. Zooplankton find their prey more easily as the concentration of phytoplankton rises. So even though the phytoplankton get more light and their growth rate increases, the voracious feeding of the zooplankton keeps them largely in-check, and the overall rise in phytoplankton occurs at roughly the same rate from winter to late spring. Eventually in mid-summer, the phytoplankton run out of nutrients and the now abundant zooplankton easily overtake them, and the bloom ends with a rapid crash.
"What the satellite data appear to be telling us is that the physical mixing of water has as much or more to do with the success of the bloom as does the rate of phytoplankton photosynthesis," Behrenfeld said. "Big blooms appear to require deeper wintertime mixing."
That's a concern, he said, because with further global warming, many ocean regions are expected to become warmer and more stratified. In places where this process is operating -- which includes the North Atlantic, western North Pacific, and Southern Ocean around Antarctica -- that could lead to lower phytoplankton growth and less overall ocean productivity, less life in the oceans. These forces also affect carbon balances in the oceans, and an accurate understanding of them is needed for use in global climate models.
Worth noting, Behrenfeld said, is that some of these regions with large seasonal phytoplankton blooms are among the world's most dynamic fisheries.
The critical depth hypothesis would suggest that a warmer climate would increase ocean productivity. Behrenfeld's new hypothesis suggests the opposite.
Behrenfeld said that oceans are very complex, water mixing and currents can be affected by various forces, and more research and observation will be needed to fully understand potential future impacts. However, some oceanographers will need to go back to the drawing board.
"With the satellite record of net population growth rates in the North Atlantic, we can now dismiss the critical depth hypothesis as a valid explanation for bloom initiation," he wrote in the report.
Behrenfeld et al. Abandoning Sverdrup's Critical Depth Hypothesis on phytoplankton blooms. Ecology, 2010; 91 (4)
This study presents the first detailed observation of the transition from grounded to floating glaciers. Such a transition is currently taking place at Columbia Glacier, one of Alaska's many tidewater glaciers. Tidewater glaciers flow directly into the ocean, ending at a cliff in the sea, where icebergs are formed. Prior to this study, Alaskan tidewater glaciers were believed to be exclusively "grounded" (resting on the ocean floor), and unable to float without disintegrating.
However, Columbia Glacier unexpectedly developed a floating extension in 2007 that has endured far longer than researchers expected. The research team believes that this floating section may have been caused by the speed at which the glacier is receding. Columbia is one of the fastest receding glaciers in the world, having retreated 4 kilometers (2.49 miles) since 2004, and nearly 20 kilometers (12.43 miles) since 1980.
"We're seeing more tidewater glaciers retreat," Walter said. "As they retreat, they thin and that increases the likelihood that they'll come afloat."
The study, co-authored by U.S. Geological Survey (USGS) glaciologist and Scripps alumnus Shad O'Neel, is part of a larger effort to understand and include calving in large-scale glacier models, which are essential in producing accurate forecasts of sea-level rise. The research team conducted its study on Columbia Glacier by installing a seismometer, a sensor that measures seismic waves that are produced by shifts in geologic formations, including earthquakes, landslides, and glacier calving. They studied data collected from 2004-2005 and 2008-2009 that allowed them to compare the glacier's activity before and after it began floating.
The formation of icebergs, through a process known as "calving," is a leading source of additional water for the global ocean basin. As this study confirms, grounded glaciers and floating glaciers often show fundamentally different calving mechanics. However, iceberg calving is also one of the least understood processes involved in ice mass loss and consequential sea level rise. This study, which is funded by the National Science Foundation, sheds light on the process by comparing the size and frequency of icebergs calved by a glacier during both floating and grounded conditions.
Calving occurs when fractures in the ice join up and cause a piece of ice to completely separate from the main glacier to form an iceberg. Unlike the floating glaciers, grounded glaciers calve icebergs nearly continuously, but they are generally quite small.
Through this study, scientists can begin to analyze the mechanics of the calving process in glaciers (both floating and grounded) and ice shelves, which will allow them to better understand and predict iceberg production from glaciers and ice sheets. These predictions, in turn, will provide a more accurate estimate of sea-level rise in the coming years.
Materials provided by Scripps Institution of Oceanography / University of California, San Diego.
This is the second cruise this year to the study region. The first cruise took place over a period of 14 days in April-May 2010, with the aim of determining biological and chemical conditions in the ocean before the large annual spring phytoplankton bloom starts. On this first cruise the team took the opportunity to observe large Icelandic volcanic ash inputs to the ocean from Eyjafjallajökull, which was erupting at the time. The team's return to the Irminger and Iceland Basin region this summer will allow them to assess how phytoplankton blooms have developed. They will also investigate whether phytoplankton in the region are growth limited because of a lack of iron, or whether the volcanic ash inputs have supplied sufficient iron to sustain the spring blooms longer than usual.
The team will sample for atmospheric dust and nutrients in the seawater, and measure the activity of phytoplankton, microscopic plants that form the base of the marine food web and take carbon dioxide from the atmosphere. There is an expedition blog which can be viewed at: http://www.classroomatsea.net/D354/
In many regions of the ocean, the productivity of phytoplankton is limited by the availability of iron, which is essential for their growth. On a previous cruise in 2007, scientists from NOCS demonstrated that the high-latitude North Atlantic Ocean -- just south of Iceland and east of Greenland -- might be one such region. Consequently biological productivity, and ultimately the carbon cycle, may be sensitive to any changes in iron inputs there.
The sub-polar Atlantic Ocean is a globally important ocean region, as it is a sink for atmospheric CO2, and an area where deep-water formation takes place. Potential iron limitation of CO2 fixation by phytoplankton in this region would represent an inefficiency in atmospheric CO2 uptake by the ocean.
Volcanic ash is thought to be capable of providing a significant source of iron for phytoplankton, so the recent eruption of Eyjafjallajökull presented an unexpected opportunity to study a 'natural experiment' where the system has potentially been alleviated from the normal potential iron-limited condition.
Dr Mark Moore from SOES, who led the first cruise, says: "it will be really interesting to return to the region where we observed significant ash inputs earlier in the year. We are very fortunate to be able to go back and see whether there is an effect on ocean productivity."
Professor Eric Achterberg, also from SOES and leading the second cruise, says: "We will be doing further biological experiments at sea in the Iceland and Irminger Basins during this five-week cruise. In particular we will add volcanic ash collected on the first cruise to seawater samples (and also add iron separately) to study the response of phytoplankton. This work is built into our original programme and provides a unique opportunity to determine the biological effects of volcanic ash inputs to the ocean."
The team, which also includes scientists from the Universities of Portsmouth, Cape Town, East Anglia and Seville, set sail from Avonmouth on July 4 and is scheduled to return to the UK on August 11.
Materials provided by National Oceanography Centre, Southampton, via AlphaGalileo.
The gelling agent developed by his team is environmentally benign. It uses a sugar-based molecule that can be obtained from renewable sources and is biodegradable. In addition, only a relatively small amount of the agent -- five percent of the volume of the oil being recovered -- is required for the process, which handles a range of oil from crude to vegetable oil, to work.
The BP oil spill, which began April 24, has been pouring oil into the Gulf of Mexico at the rate of 40,000 barrels per day. Current clean-up methods, which have been in use for more than 40 years, include burning, skimming oil and using chemical dispersants. The latter can be toxic to marine life and may have unknown long-term cumulative effects on the environment, Professor John pointed out.
Besides Professor John, the team included: Swapnil R. Jadhav, a graduate student in Professor John's laboratory; Dr. Praveen Kumar Vemula, a former post-doc in Professor John's lab now at Harvard-MIT Division of Health Sciences & Technology; Dr. Srinivasa R. Raghavan, Associate Professor and Patrick & Marguerite Sun Chair in Chemical and Biomolecular Engineering at University of Maryland, and Rakesh Kumar, a graduate student in Professor Raghavan's laboratory.
The team's findings will be reported July 15 in the journal Angewandte Chemie International Edition.
Materials provided by City College of New York.
In a remarkable demonstration, which made its way onto YouTube, the Chinese nanoscientists stuck a sheet of nanotubes onto the side of a flag, and attached it to an mp3 player. They used the nanotube-coated flag to play a song while it flapped in the breeze. But they did not test its ability to operate under water.
Aliev's group took that step, showing that nanotube sheets produce the kind of low-frequency sound waves that enable sonar to determine the location, depth, and speed of underwater objects. They also verified that the speakers can be tuned to specific frequencies to cancel out noise, such as the sound of a submarine moving through the depths.
Materials provided by American Chemical Society, via EurekAlert!, a service of AAAS.
Tiny Marine Microbes Exert Influence on Global Climate: Microorganisms Display a Behavior Characteristic of Larger Animals
"We found that ecological interactions and behavioral responses taking place within volumes of a fraction of a drop of seawater can ultimately influence important ocean chemical cycling processes," said Seymour.
Using microfluidic technology, the team of researchers led by Professor Roman Stocker of the Massachusetts Institute of Technology's Department of Civil and Environmental Engineering, recorded microbes swimming toward the chemical dimethylsulfoniopropionate (DMSP) as it was released into a tiny channel occupied by the microbes.
The fact that the microbes actively moved toward the DMSP indicates that the tiny organisms play a role in ocean sulphur and carbon cycles, which exert a powerful influence on Earth's climate. How fast the microorganisms consume DMSP -- rather than converting it into DMS -- is important because DMS is involved in the formation of clouds in the atmosphere. This in turn affects the heat balance of the atmosphere.
Seymour, Stocker, Professor Rafel Simó of the Institute for Marine Sciences in Barcelona, and MIT graduate student Tanvir Ahmed carried out the research in the MIT laboratory of Stocker, who pioneered the use of microfluidics and video microscopy in the study of ocean microbes. The new study is the first to make a visual record of microbial behaviour in the presence of DMSP.
"It's important to be able to directly look at an environment in order to understand its ecology," Stocker said. "We can now visualize the behavior of marine microorganisms much like ecologists have done with macro-organisms for a long time."
To do this, the team recreated a microcosm of the ocean environment using a microfluidic device about the size of a flash drive with minuscule channels engraved in a clear rubbery material. The scientists injected DMSP into the channel in a way that mimics the bursting of an algal cell after viral infection -- a common event in the ocean -- then, using a camera attached to a microscope, they recorded whether and how microbes swam towards the chemical.
The researchers found that some marine microbes, including bacteria, are attracted to DMSP because they feed on it, whereas others are drawn to the chemical because it signals the presence of prey. This challenges previous theories that this chemical might be a deterrent against predators.
"Our observations clearly show that, for some plankton, DMSP acts as an attractant towards prey rather than a deterrent," said Simó, an expert on the role of DMSP in the sulfur cycle, "By simulating the microscale patches of the chemical cue and directly monitoring the swimming responses of the predators towards these patches, we get a much more accurate perception of these important ecological interactions than can be obtained from traditional bulk approaches."
"These scientists have used impressive technology to study interactions between organisms and their chemical environment at the scales they actually take place," said David Garrison, director of the National Science Foundation (NSF)'s biological oceanography program. "The research will give us new insights on the workings of microbial assemblages in nature."
The research also indicates that marine microorganisms have at least one behavioral characteristic in common with larger sea and land animals: we're all drawn to food.
The team plans to extend the research from the laboratory to the ocean environment; the team is working on an experimental system that can be used on board oceanographic ships working with bacteria collected directly from the ocean.
Source: "Chemoattraction to Dimethylsulfoniopropionate Throughout the Marine Microbial Food Web," by Justin R. Seymour, Rafel Simó, Tanvir Ahmed and Roman Stocker. Science, 16 July 2010.
Thursday, July 15, 2010
Near the spill site, researchers have documented a massive die-off of pyrosomes - cucumber-shaped, gelatinous organisms fed on by endangered sea turtles.
Along the coast, droplets of oil are being foundinside the shells of young crabs that are a mainstay in the diet of fish, turtles and shorebirds.
And at the base of the food web, tiny organisms that consume oil and gas are proliferating.
If such impacts continue, the scientists warn of a grim reshuffling of sealife that could over time cascade through the ecosystem and imperil the region's multibillion-dollar fishing industry.
Federal wildlife officials say the impacts are not irreversible, and no tainted seafood has yet been found. But Rep. Ed Markey, D-Mass., who chairs a House committee investigating the spill, warned Tuesday that the problem is just unfolding and toxic oil could be entering seafood stocks as predators eat contaminated marine life.
"You change the base of the food web, it's going to ripple through the entire food web," said marine scientist Rob Condon, who found oil-loving bacteria off the Alabama coastline, more than 90 miles from BP's collapsed Deepwater Horizon drill rig. "Ultimately it's going to impact fishing and introduce a lot of contaminants into the food web."
The food web is the fundamental fabric of life in the Gulf. Once referred to as the food chain, the updated term reflects the cyclical nature of a process in which even the largest predator becomes a food source as it dies and decomposes.
What has emerged from research done to date are snapshots of disruption across a swath of the northern Gulf of Mexico. It stretches from the 5,000-feet deep waters at the spill site to the continental shelf off Alabama and the shallow coastal marshes of Louisiana.
Much of the spill - estimated at up to 182 million gallons of oil and around 12 billion cubic feet of natural gas - was broken into small droplets by chemical dispersants at the site of the leaking well head. That reduced the direct impact to the shoreline and kept much of the oil and natural gas suspended in the water.
But immature crabs born offshore are suspected to be bringing that oil - tucked into their shells - into coastal estuaries from Pensacola, Fla., to Galveston, Texas. Oil being carried by small organisms for long distances means the spill's effects could be wider than previously suspected, said Tulane professor Caz Taylor.
Chemical oceanographer John Kessler from Texas A&M University and geochemist David Valentine from the University of California-Santa Barbara recently spent about two weeks sampling the waters in a six-mile radius around the BP-operated Deepwater Horizon rig. More than 3,000 feet below the surface, they found natural gas levels have reached about 100,000 times normal, Kessler said.
Already those concentrations are pushing down oxygen levels as the gas gets broken down by bacteria, Kessler and Valentine said. When oxygen levels drop low enough, the breakdown of oil and gas grinds to a halt and most life can't be sustained.
The researchers also found dead pyrosomes covering the Gulf's surface in and around the spill site. "There were thousands of these guys dead on the surface, just a mass eradication of them," Kessler said.
Scientists said they believe the pyrosomes - six inches to a foot in length - have been killed by the toxins in the oil because there have no other explanation, though they plan further testing.
The researchers say the dead creatures probably are floating to the surface rather than sinking because they have absorbed gas bubbles as they filtered water for food.
The death of pyrosomes could set off a ripple effect. One species that could be directly affected by what is happening to the pyrosomes would be sea turtles, said Laurence Madin, a research director at the Woods Hole Oceanographic Institution in Cape Cod, Mass. Some larger fish, such as tuna, may also feed on pyrosomes.
"If the pyrosomes aredying because they've got hydrocarbons in their tissues and then they're getting eaten by turtles, it's going to get into the turtles," said Madin. It was uncertain whether that would kill or sicken the turtles.
The BP spill also is altering the food web by providing vast food for bacteria that consume oil and gas, allowing them to flourish.
At the same time, the surface slick is blocking sunlight needed to sustain plant-like phytoplankton, which under normal circumstances would be at the base of the food web.
Phytoplankton are food for small bait fish such as menhaden, and a decline in those fish could reduce tuna, red snapper and other populations important to the Gulf's fishing industries, said Condon, a researcher with Alabama's Dauphin Island Sea Lab.
Seafood safety tests on hundreds of fish, shrimp and other marine life that could make it into the food supply so far have turned up negative for dangerous oil contamination.
Assuming the BP gusher is stopped and the cleanup successful, government and fishing industry scientists said the Gulf still could rebound to a healthy condition.
Ron Luken, chief scientist for Omega Protein, a Houston-based company that harvests menhaden to extract fish oil, says most adult fish could avoid the spill by swimming to areas untainted by crude. Young fish and other small creatures already in those clean waters could later repopulate the impacted areas.
"I don't think anybody has documented wholesale changes," said Steve Murawski, chief scientist for the National Marine Fisheries Service. "If that actually occurs, that has a potentially great ramification for life at the higher end of the food web."
The study, which combined sea surface measurements going back to the 1960s and satellite observations, indicates anthropogenic climate warming likely is amplifying regional sea rise changes in parts of the Indian Ocean, threatening inhabitants of some coastal areas and islands, said CU-Boulder Associate Professor Weiqing Han, lead study author. The sea level rise -- which may aggravate monsoon flooding in Bangladesh and India -- could have far-reaching impacts on both future regional and global climate.
The key player in the process is the Indo-Pacific warm pool, an enormous, bathtub-shaped area of the tropical oceans stretching from the east coast of Africa west to the International Date Line in the Pacific. The warm pool has heated by about 1 degree Fahrenheit, or 0.5 degrees Celsius, in the past 50 years, primarily caused by human-generated increases of greenhouse gases, said Han.
"Our results from this study imply that if future anthropogenic warming effects in the Indo-Pacific warm pool dominate natural variability, mid-ocean islands such as the Mascarenhas Archipelago, coasts of Indonesia, Sumatra and the north Indian Ocean may experience significantly more sea level rise than the global average," said Han of CU-Boulder's atmospheric and oceanic sciences department.
A paper on the subject was published in Nature Geoscience. Co-authors included Balaji Rajagopalan, Xiao-Wei Quan, Jih-wang Wang and Laurie Trenary of CU-Boulder, Gerald Meehl, John Fasullo, Aixue Hu, William Large and Stephen Yeager of the National Center for Atmospheric Research in Boulder, Jialin Lin of Ohio State University, and Alan Walcraft and Toshiaki Shinoda of the Naval Research Laboratory in Mississippi.
While a number of areas in the Indian Ocean region are showing sea level rise, the study also indicated the Seychelles Islands and Zanzibar off Tanzania's coastline show the largest sea level drop. Global sea level patterns are not geographically uniform, and sea rise in some areas correlate with sea level fall in other areas, said NCAR's Meehl.
The Indian Ocean is the world's third largest ocean and makes up about 20 percent of the water on Earth's surface. The ocean is bounded on the west by East Africa, on the north by India, on the east by Indochina and Australia, and on the south by the Southern Ocean off the coast of Antarctica.
The patterns of sea level change are driven by the combined enhancement of two primary atmospheric wind patterns known as the Hadley circulation and the Walker circulation. The Hadley circulation in the Indian Ocean is dominated by air currents rising above strongly heated tropical waters near the equator and flowing poleward, then sinking to the ocean in the subtropics and causing surface air to flow back toward the equator.
The Indian Ocean's Walker circulation causes air to rise and flow westward at upper levels, sink to the surface and then flow eastward back toward the Indo-Pacific warm pool. "The combined enhancement of the Hadley and Walker circulation form a distinct surface wind pattern that drives specific sea level patterns," said Han.
The international research team used several different sophisticated ocean and climate models for the study, including the Parallel Ocean Program -- the ocean component of NCAR's widely used Community Climate System Model. In addition, the team used a wind-driven, linear ocean model for the study.
"Our new results show that human-caused changes of atmospheric and oceanic circulation over the Indian Ocean region -- which have not been studied previously -- are the major cause for the regional variability of sea level change," wrote the authors in Nature Geoscience.
Han said that based on all-season data records, there is no significant sea level rise around the Maldives. But when the team looked at winter season data only, the Maldives show significant sea level rise, a cause for concern. The smallest Asian country, the Maldives is made up of more than 1,000 islands -- about 200 of which are inhabited by about 300,000 people -- and are on average only about five feet above sea level.
The complex circulation patterns in the Indian Ocean may also affect precipitation by forcing even more atmospheric air down to the surface in Indian Ocean subtropical regions than normal, Han speculated. "This may favor a weakening of atmospheric convection in the subtropics, which may increase rainfall in the eastern tropical regions of the Indian Ocean and increase drought in the western equatorial Indian Ocean region, including east Africa," Han said.
The new study indicates that in order to document sea level change on a global scale, researchers also need to know the specifics of regional sea level changes that will be important for coastal and island regions, said NCAR's Hu. Along the coasts of the northern Indian Ocean, seas have risen by an average of about 0.5 inches, or 13 millimeters, per decade.
"It is important for us to understand the regional changes of the sea level, which will have effects on coastal and island regions," said Hu.
The study was funded by a number of organizations, including NCAR, the National Science Foundation, NASA and the U.S. Department of Energy. University of Colorado at Boulder (2010, July 13). Sea levels rising in parts of Indian Ocean; Greenhouse gases play role, study finds. ScienceDaily. Retrieved July 15, 2010, from http://www.sciencedaily.com /releases/2010/07/100713101412.htm
Tuesday, July 13, 2010
Research into the behaviour of shrimps exposed to the antidepressant fluoxetine, showed that their behaviour is dramatically affected. The shrimps are five times more likely to swim toward the light instead of away from it -- making them more likely to be eaten by fish or birds, which could have devastating effects on the shrimp population.
"Crustaceans are crucial to the food chain and if shrimps' natural behaviour is being changed because of antidepressant levels in the sea this could seriously upset the natural balance of the ecosystem," said Dr Alex Ford from the University of Portsmouth's Institute of Marine Sciences.
"Much of what humans consume you can detect in the water in some concentration. We're a nation of coffee drinkers and there is a huge amount of caffeine found in waste water, for example. It's no surprise that what we get from the pharmacy will also be contaminating the country's waterways."
The research is published in the journal Aquatic Toxicology. The study found that the shrimps' behaviour changes when they are exposed to the same levels of fluoxetine found in the waste water that flows to rivers and estuaries as a result of the drugs humans excrete in sewage.
Dr Ford's research was motivated by a species of parasite which can alter the behaviour of aquatic creatures through changing serotonin levels within the brains of the organisms. Serotonin is a neuro-hormone found in many animals, including humans, known to control types of behaviour, such as modulating mood and decreasing anxiety.
Drugs to combat depression in humans are often designed to target levels of serotonin which led to the question of whether they could also alter the behaviour of marine organisms.
Dr Ford said: "Effluent is concentrated in river estuaries and coastal areas, which is where shrimps and other marine life live -- this means that the shrimps are taking on the excreted drugs of whole towns."
Prescriptions for antidepressants have risen rapidly in recent years, according to the Office for National Statistics. In 2002, there were 26.3 million antidepressant prescriptions handed out by doctors in England and Wales -- yet the environmental effect of pharmaceuticals in sewage has been largely unexplored.
Dr Ford is hoping to carry out future research on a number of other prescribed drugs on the market known to affect serotonin.
Head of the School of Biological Sciences, Professor Matt Guille, said: "Dr Ford has conducted some beautifully simple research, which potentially shows huge ecological consequences. I hope it will lead the way for further study of prescribed drugs and other substances impacting on the country's marine-life." Yasmin Guler, Alex T. Ford. Anti-depressants make amphipods see the light. Aquatic Toxicology, 2010; DOI:10.1016/j.aquatox.2010.05.019
Antarctic penguins come on land for just a few short months each summer to breed and raise their chicks. Raising a family in the coldest place on earth is no small feat. Adelie penguins pull it off by tag-team parenting, the researchers explained. Males and females take turns incubating the eggs and guarding the chicks while their mate forages for food.
Males arrive first to claim a territory and build a nest. When the females arrive, the males serenade prospective mates by throwing their heads back, pointing their beaks to the sky, and emitting a series of hoarse trills and squawks.
"They're not musical calls -- they sound like a cross between a donkey and a stalled car," said author Emma Marks of the University of Auckland. Penguin calls may not be music to our ears, but to penguin females they hold clues to a male's paternal potential, Marks and colleagues report.
After choosing a mate the female lays two eggs and returns to sea, leaving the male alone to tend the egg until she returns to take the next shift. For the first two weeks penguin dads do the bulk of babysitting duty without breaking to eat. By relying on stored fat reserves, father penguins can lose more than 20% of their body weight over the course of the summer breeding season, the researchers said.
"It's a pretty arduous task, especially for the males," said Marks. "If a male doesn't have enough fat to last these fasts, he may have to abandon the eggs and go to sea before the female can make it back. So it's imperative that the female pick a male in good condition," she added.
The researchers wanted to know how courtship calls help a penguin female choose the father of her chicks. "We knew that females preferred some males over others. But we didn't know what traits females were using to choose a good mate," said co-author Dianne Brunton of Massey University in New Zealand.
"If she chooses a male with a particular kind of call, does she have a better chance of successfully raising chicks?" Marks asked.
To find out, Marks traveled to Antarctica's remote Ross Island, summer home to half a million Adelie penguins. Over the course of the next three months she weighed dozens of males and recorded their calls with a handheld microphone. She also noted how successful they were at attracting mates and raising chicks.
When the researchers examined the calls, they found that steady frequency over the longest part of the call -- an extended chattering in the middle of the male's display -- best predicts male buffness and breeding success. "It's as if females are listening to the stability of the call," said Marks.
Males with more consistent pitch were snatched up more quickly. These males were also heavier and more successful at raising chicks, the researchers found. "The fat surrounding the male's voice box changes what his call sounds like," said Brunton. "We don't yet know the physiological mechanism for call production, but body fat appears to stabilize their calls," Marks added.
By listening to male courtship calls, a female can tell how fat a male is and what kind of father he'll be, Brunton explained. Fatter males make better fathers because they have the energy reserves to endure long fasts, so are less likely to leave the nest and desert their chicks.
"A fat male is a good choice for a female because males do so much of the offspring care," said Brunton. "They're able to incubate the eggs for longer and use up their fat stores, while skinny males aren't able to do that."
The researchers also wondered if males were always honest about their potential as caring fathers, or merely bluffing to attract a mate. "What if the guy calls, and it turns out he's a skinny bird pretending to be a fat bird, making himself sound better than he really is?" said Marks.
"Females can't judge how fat a male is just by looking at him," said Brunton. "How fat he looks depends on how he's standing and how fluffed up his feathers are."
A male who lies about his paternal commitment might increase his chances of passing on his genes, said co-author Allen Rodrigo, Director of the National Evolutionary Synthesis Center in Durham, North Carolina. For that reason, females are likely to be on the lookout for the most honest indicators of paternal potential, he explained.
As penguin dads lost weight over the chick-rearing season, their calls changed too, Marks found. "So a skinny male is unlikely to be able to pretend he's a big fat male. He can't fake it," said Marks. National Evolutionary Synthesis Center (NESCent) (2010, July 12). Penguin males with steady pitch make better parents. ScienceDaily. Retrieved July 13, 2010, from http://www.sciencedaily.com /releases/2010/07/100712102806.htm
The analysis of six years of data showed that people living near creeks with sewage overflows in lower-income neighborhoods of Southeast Atlanta had a seven times higher risk for West Nile virus than the rest of the city.
"The infection rate for mosquitoes, birds and humans is strongly associated with their proximity to a creek impacted by sewage," says Gonzalo Vazquez-Prokopec, the Emory disease ecologist who led the study. "And if the creek is in a low-income neighborhood, we found that the entire cycle of infection is even higher."
More affluent residents are more likely to have air-conditioning and use insect repellant and other protective measures, the researchers theorized.
The study, published in the current issue of Environmental Health Perspectives, was a collaboration of Emory, the Centers for Disease Control and Prevention, the Georgia Division of Public Health, the Fulton County Department of Health and Wellness, the National Institutes of Health, the Fogarty International Center and the University of Georgia.
According to the Environmental Protection Agency, about 850 billion gallons per year of untreated mixed wastewater and storm water are discharged into U.S. urban waters, mainly through combined sewer overflow (CSO) systems that are used in more than 700 cities. Under normal conditions, CSO systems channel wastewater to a treatment plant before it is discharged into a waterway. During periods of heavy rain or snowmelt, however, the wastewater flows directly into natural waterways after only minimal chlorine treatment and sieving to remove large physical contaminants.
Most of the available data on the human health impacts of sewage-affected waterways focuses on the effects of exposures to bacteria, heavy metals, hormones and other pollutants.
Previous research by Emory's Department of Environmental Studies has shown that the Culex mosquito -- a vector for West Nile virus and other human pathogens -- thrives in Atlanta streams contaminated with CSO discharges. The mosquitoes become more populous, breed faster and grow larger than those found in cleaner waters.
"We wanted to know if the CSOs also raised the risk of getting infected with West Nile virus," said Uriel Kitron, chair of environmental studies and a co-author of the study.
An expert in geographic information systems (GIS) technology, Vazquez-Prokopec did a spatial analysis integrating the geographic coordinates of each CSO facility and associated streams, and six years of surveillance data on mosquito abundance and West Nile virus infections in mosquitoes, humans, blue jays and crows. (These birds are considered sentinels for the disease, due to their high West Nile Virus mortality and their proximity to humans.)
During 2001-2007, Georgia reported 199 human West Nile virus infections and 17 deaths. About 25 percent of the cases resided in Fulton County. The county forms the core of metropolitan Atlanta, and encompasses a range of socio-economic conditions, from the wealthiest neighborhoods in the state to those with the highest poverty rates in the country.
The analysis found that mosquitoes and birds near all seven of the CSO facilities and associated streams of Atlanta had significantly higher rates of West Nile virus infection than those near urban creeks not affected by CSOs. Humans residing near CSO streams also had a higher rate of infection if they lived in a low-income neighborhood with a greater proportion of tree canopy cover and homes built during the 1950s-60s. Residents of a wealthy northern Fulton County area did not experience an increase in West Nile virus cases, despite their proximity to two CSO streams.
In 2008, Atlanta completed an underground reservoir system designed to reduce the size and the number of CSOs. "In terms of mosquitoes, however, this remediation has the potential to make things worse instead of better by releasing slower flows of nutrient-rich effluent into streams," Vazquez-Prokopec notes. Emory University (2010, July 12). Sewage overflow promotes spread of West Nile virus. ScienceDaily. Retrieved July 13, 2010, from http://www.sciencedaily.com /releases/2010/07/100712103331.htm
The sea around Hawaii may be clear and blue, but it hides an enduring oceanographic mystery. Surface waters in this and other mid-ocean areas contain almost no nitrate or other plant nutrients. Yet each year, microscopic algae (phytoplankton) flourish in these vast, open-ocean areas. Although miniscule in size, these mid-ocean algae consume about one fifth of all the carbon dioxide taken up by plants and algae worldwide.
To solve this mystery, Johnson and his fellow researchers used a robotic drifter called an Apex float, which automatically moves from the sea surface down to 1,000 meters and then back again, collecting data as it goes. Researchers at the University of Washington outfitted this drifter with an oxygen sensor and a custom version of Johnson's In Situ Ultraviolet Spectrophotometer (ISUS), which measures nitrate concentrations in seawater.
The design and deployment of this custom drifter was funded by grants from the National Science Foundation, the Office of Naval Research, the National Oceanic and Atmospheric Administration, the Gordon and Betty Moore Foundation, and the David and Lucile Packard Foundation.
In December 2007, researchers from University of Hawaii placed the drifter in the ocean northeast of Oahu, where it collected ocean profiles once every five days for almost two years.
From January through October of each year, the instruments on the drifter showed a gradual increase in oxygen concentrations in the upper 100 meters of the ocean. At the same time, the float detected a gradual decrease in concentrations of nitrate in deeper waters, from 100 to 250 meters below the surface.
Johnson and his coauthors found that the amount of oxygen being produced near the surface through photosynthesis was directly proportional to the amount of nitrate that was being consumed in deeper water.
Based on the decline in nitrate concentrations at depth, the researchers estimated how much algal growth could have taken place during the year. They found that their estimates of algal growth were very similar to algal growth rates measured during the University of Hawaii's oceanographic cruises in that part of the Pacific.
Because there is not enough sunlight for algae to grow below 100 meters, the researchers conclude that algae growing near the surface somehow obtain nitrate from deeper water, and use this nitrate to grow and reproduce. But exactly how the algae obtain these deep nutrients is still unclear.
One possible mechanism is ocean eddies. Satellite and drifter data suggest that slow, swirling eddies occasionally form hundreds of meters below the surface of the Pacific. The ISUS data demonstrate that some of these eddies can carry nitrate up to about 70 meters below the ocean surface. Yet these pulses of nitrate do not appear to reach the upper 50 meters of the water column, where most of the algae grow.
Johnson and his coauthors speculate that dormant microalgae may inhabit the waters below 100 meters. Open-ocean eddies occasionally carry these algae upward, to depths of perhaps 70 meters. At this point, the algae may consume any available nitrate and then migrate farther up into the sunlit surface waters.
Johnson suggests that testing this hypothesis will provide an interesting challenge for marine biologists. Scientists already know that some algae can swim, using tiny, whip-like flagella. Other algae can actively change their buoyancy, just like the Apex float, and either sink or float upwards.
Over the next year or two, Johnson and his fellow researchers will outfit several groups of drifters with nitrate and oxygen sensors. Some of these drifters will be deployed around Hawaii. Others will be deployed near Bermuda in the mid-Atlantic. Still other groups of drifters will be deployed in the far North Pacific and in the Southern Ocean, where nitrate supplies and algal growth are typically much higher than in mid-ocean areas.
Such studies of tiny algae in the open ocean may seem remote from human activities on land. Yet the oxygen produced by mid-ocean algae is essential for the survival of life on earth. Furthermore, these algae move huge amounts of carbon dioxide from the atmosphere into the ocean, and thus play a significant role in controlling the earth's climate. As Johnson says, "The bugs you can't see with a microscope are doing all the work." Monterey Bay Aquarium Research Institute (2010, July 12). Source of essential nutrients for mid-ocean algae discovered. ScienceDaily. Retrieved July 13, 2010, from http://www.sciencedaily.com /releases/2010/06/100623132106.htm
Heart and skeletal muscle inflammation (HSMI), an often fatal disease, was first detected in salmon on a farm in Norway in 1999, and has now been reported in 417 fish farms in Norway as well as in the United Kingdom. The disease destroys heart and muscle tissue and kills up to 20 percent of infected fish. Although studies have indicated an infectious basis, recent efforts to identify the pathogen causing the disease have been unsuccessful. Now, using cutting-edge molecular techniques, an international team led by W. Ian Lipkin, MD, the John Snow Professor of Epidemiology and director of the Center for Infection and Immunity at Columbia University's Mailman School of Public Health, has found evidence that the disease may be caused by a previously unknown virus. The newly identified virus is related but distinct from previously known reoviruses, which are double-stranded RNA viruses that infect a wide range of vertebrates.
The full study findings are published online in the publication PLoS ONE.
"Our data provide compelling evidence that HSMI is associated with infection with a new reovirus," says Gustavo Palacios, first author of the study and assistant professor of Epidemiology in the Center.
"While there is no evidence that this could spread to humans, it is a threat to aquaculture and it has the potential to spread to wild salmon," added Dr. Lipkin.
To identify the virus, the Columbia University investigators used 454 high throughput DNA sequencing and bioinformatics, including a new tool called Frequency Analysis of Sequence Data (FASD), pioneered by Raul Rabadan of Columbia's Department of Biomedical Informatics. Investigators in Norway and the U.S. then looked for viral sequences in heart and kidney samples from 29 salmon representing three different HSMI outbreaks and 10 samples from healthy farmed fish. Twenty-eight of the 29 (96.5%) known HSMI samples and none of the 10 healthy salmon samples were positive. The investigators also tested 66 samples obtained from wild salmon living in nine coastal rivers in Norway. The virus was detected in sixteen of these samples (24.2%), though generally in lower concentrations than found in ailing farmed fish.
"The speed of this process, and the enthusiasm on both sides of the Atlantic created a very fruitful collaboration," says Espen Rimstad, a professor at the Norwegian School of Veterinary Science in Oslo. "Using the expertise of our colleagues at Columbia in high throughput sequencing and advanced bioinformatics, we had within a few weeks the whole genome sequence of a hitherto unknown virus."
Additional research will be needed to confirm that the reovirus is the cause of HSMI. Meanwhile work has already begun in Norway to develop a vaccine to protect farmed Atlantic salmon. Columbia University's Mailman School of Public Health (2010, July 12). What’s killing farmed salmon? New virus may also pose risk to wild salmon. ScienceDaily. Retrieved July 13, 2010, from http://www.sciencedaily.com /releases/2010/07/100709210823.htm
Sunday, July 11, 2010
What oceanography professors Markus Huettel and Joel E. Kostka learn will enable them to predict when most of the oil in the beaches will be gone. Their findings may also reveal ways to accelerate the oil degradation rate -- and speed matters, because toxic crude components that remain buried on Gulf Coast beaches may seep into the groundwater below.
"This enormous oil spill affects hundreds of miles of beaches in the Gulf of Mexico," Huettel said. "We can remove the oil from the beach surface, but oil is also carried deeper into the sand, and we need to understand what happens to that oil. Preventing groundwater contamination is crucial not only to Gulf Coast residents but also to coastal management and local economies like fisheries and tourism that depend on water quality."
"We will also study the effect of the dispersant known as Corexit on oil metabolism by natural microbial communities," Kostka said. "Through contacts in the field, my laboratory has acquired Corexit and source oil from the MC252 (Deepwater Horizon) well head for use in our experiments."
St. George Island, Fla., and Dauphin Island, Ala., have served as the primary research sites since early June, when the one-year study began. In addition, the researchers have obtained heavily oiled sand from Pensacola Beach, Fla., and from a barrier island off the Louisiana coast. If warranted by the oil's movement, they will also collect near-shore water and sediment samples from other Gulf beaches.
Funding for their collaborative research comes from a "RAPID" (Rapid Research Response) grant from the National Science Foundation.
Huettel and Kostka will analyze sediment cores collected from Gulf beaches to find out how much and to what depth oil washed onto the shore is carried into the sand; how rapidly microbes in the sand are breaking it down; and how the oil pollution may be impacting the structure and function of natural microbial communities that help to protect water quality on the coast.
"We'll also show how the oil itself alters the transport and filtration of oxygen-rich water into the beach by clogging the sand -- and how this clogging and resulting reduced oxygen availability in the sand affects the microbial community and degradation of buried oil," Huettel said.
Currents and winds carry the oil, and oil combined with dispersants -- chemicals that disperse the crude into very small oil droplets -- to the Gulf shores, where it washes up on sandy beaches.
Larger crude-oil accumulations such as pancake oil (round, flat accumulations of heavy crude oil) and tar balls (weathered crude oil accumulations that have been formed into ball-shaped structures) are deposited on the beach. Meanwhile, liquid oil (in the form of an oil sheen, or small dispersed droplets) can penetrate many feet deep into the permeable beach sand.
"Oil-filled water that washes up on the beach filters through the porous sediment and carries the oil with it into the sand," Huettel said. "In addition, the water-level drop between high and low tide causes a water-level drop within the beach sediment that can transport oil that has penetrated into the beach into even deeper sediment layers."
"Crude oil is a natural component that constantly seeps out of Gulf of Mexico sediments --obviously in much smaller quantities than those now caused by the drilling accident -- so native microbes have evolved that consume this oil and thereby degrade it," Kostka said. "These microorganisms include bacteria and also some microalgae that live in the water column and the sediments of the Gulf of Mexico."
Kostka said oil accumulations deposited on the beach surface are easily removed by, for example, scraping off the top layer of sand. However, the oil components that penetrate into the sand can only be removed by microbial degradation.
"If oxygen is present -- as it is in the water and in the upper layers of the beach sand -- the microbes decompose the oil aerobically (by using oxygen)," Kostka said. "This degradation process is much faster than the degradation under anaerobic conditions (when no oxygen is available), such as those found in deeper sediment layers of the beach. That's why at the site of the Exxon Valdez oil spill in Alaska, oil can still be found deeply buried in the gravel beach sediments, because anaerobic microbial degradation is slow and, in Alaska, slower still because of the cold climate."
"Unfortunately, said Huettel, "crude oil contains such harmful substances that even small amounts can kill fish larvae -- which means that oil stored in deep layers of beach sediment present a potential source of toxins to near-shore waters and groundwater."
Their NSF-funded study ("Rates and mechanisms controlling the degradation of crude oil from the MC252 spill in Gulf of Mexico beach sands") is the latest of several collaborations between Huettel and Kostka that have examined organic matter transport and degradation in Gulf sands. Florida State University (2010, July 8). How fast can microbes break down oil washed onto Gulf beaches?. ScienceDaily. Retrieved July 11, 2010, from http://www.sciencedaily.com/releases/2010/07/100707222312.htm
Although the Gulf of Mexico has been intensively surveyed by scientists and picked over by fishermen, it is still home to fishes that are waiting to be described. New research published in the Journal of Fish Biologydescribes two new species of pancake batfishes (Halieutichthys intermedius and H. bispinosus) and re-describes another (H. aculeatus), all of which live in waters either partially or fully encompassed by the recent oil spill.
"One of the fishes that we describe is completely restricted to the oil spill area," says John Sparks, curator of Ichthyology at the American Museum of Natural History. "If we are still finding new species of fishes in the Gulf, imagine how much diversity -- especially microdiversity -- is out there that we do not know about."
Pancake batfishes are members of the anglerfish familyOgcocephalidae, a group of about 70 species of flat bottom-dwellers that often live in deep, perpetually dark waters. Pancake batfishes have enormous heads and mouths that can thrust forward. This, combined with their ability to cryptically blend in with their surroundings, gives them an advantage for capturing prey. They use their stout, arm-like fins to 'walk' awkwardly along the substrate; their movements have been described as grotesque, resembling a walking bat. As most anglerfishes, batfishes have a dorsal fin that is modified into a spine or lure, although their lure excretes a fluid to reel in prey instead of bio-illuminating.
The pancake batfishes described by Sparks and colleagues, genus Halieutichthys , live in shallower waters than most batfishes and occur along the coasts of the Gulf of Mexico and Atlantic from Louisiana to North Carolina. Until now, the currently described three fishes had been lumped into one species, since they all have similar coloration and body shape.
But there are several differences. The three species are distinguished by the size, shape (blunt or sharp), and arrangement of tubercles on the body; the presence or absence of dark bands on the pectoral fin; and the unique reticulate pigmentation patterns on the dorsal body surface. H. aculeatus, the re-described species, is characterized by a comparatively sparse arrangement of spiny tubercles and is distributed along the northeastern gulf coast as well as along the Florida, Georgia, and Carolina coasts. H. bispinosus is a newly described species with a characteristic pattern of densely arranged spiny tubercles covering the body and a geographic distribution similar to H. aculeatus. Finally, H. intermedius, the second newly described species, has a smooth, non-spiny dorsal surface and a geographic distribution that mirrors the current range of the Gulf oil spill. This last species does not have a known population outside of the Gulf of Mexico.
"These discoveries underscore the potential loss of undocumented biodiversity that a disaster of this scale may portend," says Sparks.
In addition to Sparks, authors include Hsuan-Ching Ho of the Biodiversity Research Center of Academica Sinica in Taipei, Taiwan and Prosanta Chakrabarty of the Museum of Natural Science at Louisiana State University. The research was funded by the National Science Foundation, the Lakeside Foundation, and the Lerner-Gray Fund for Marine Research. American Museum of Natural History (2010, July 8). Two new species of pancake batfishes discovered from area engulfed by oil spill.ScienceDaily. Retrieved July 11, 2010, from http://www.sciencedaily.com/releases/2010/07/100708111206.htm