4 March 2010
Barnacle Dinner in the Galapagos
Working at an expansive range of underwater sites in the Galapagos, marine ecologist Jon Witman and his team found that at two sub-tidal depths, barnacle larvae had latched onto rock walls, despite the vertical currents. In fact, the stronger the vertical current, the more likely the barnacles would colonize a rocky surface.
The researchers also documented the presence of whelks and hogfish, which feast on barnacles. This predator-prey relationship shows that vertical upwelling zones are “much more dynamic ecosystems in terms of marine organisms than previously believed,” Witman said.
Scientists who study coastal marine communities had assumed that prey species such as barnacles and mussels would be largely absent in vertical upwelling areas, since the larvae, which float freely in the water as they seek a surface to attach to, would more likely be swept away in the coast-to-offshore currents. Studies of the near-surface layer of the water in rocky tidal zones confirmed that thinking. But the field work by Witman and his group, in deeper water than previous studies, told a different tale: Few barnacles were found on the plates in the weak upwelling zones, while plates at the strong upwelling sites were teeming with the crustaceans. Flourishing barnacle communities were found at both the 6-meter and 15-meter stations, the researchers reported.
The scientists think the free-floating larvae thrive in the vertical-current zones because they are constantly being bounced against the rocky walls and eventually find a tranquil spot in micro crevices in the rock to latch on to.
Further Reading
Coupling between subtidal prey and consumers along a mesoscale upwelling gradient in the Galápagos Islands. Jon D. Witman, Margarita Brandt, Franz Smith. Ecological Monographs 2010 80:1, 153-177
Brown University News, Barnacles Prefer Upwelling Currents, Enriching Food Chains in the Galapagos
Labels: Galapagos, marine biology, research, SCUBA News
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22 February 2010
Sea of Cortez Threatened
Life in the Sea of Cortez is endangered by destructive new fishing methods.Ten years ago graduate students Octavio Aburto-Oropeza and Gustavo Paredes surveyed the marine life of the Sea of Cortez (also known as the Gulf of California). In 2009 they went back and were shocked at how things had declined. Sixty percent of the surveyed sites showed signs of degradation, according to Aburto-Oropeza, and many are now missing the top predators normally present in healthy, functioning ecosystems.
"Ten years later we can actually measure the effects of not putting conservation measures in place," Paredes told Explorations Magazine. "Some of us had been conducting surveys in certain sites every year, but until this year we didn't know the whole story of what was going on."
The changes have occurred because of fishing. Traditional hook-and-line fisherman have been put out of business by vastly more damaging gill net fishing and "hookah" diving. Hookah fishermen use surface-supplied air through piping that allows them to walk along the seafloor for long periods of time. The technique is typically conducted at night when fish are resting, allowing the hookah fishermen to spear or grab large numbers of vulnerable fish and invertebrates.
In the most dramatic example of fishing impacts observed on the 2009 expedition a survey of San Esteban Island in the north revealed reefs devoid of fish and instead covered by mats of cyanobacteria.
There are areas which have flourished, though. One example is Cabo Pulmo near the southern tip of the Baja peninsula. Fishing restrictions there since 1995 have ensured that Cabo Pulmo retains a mix of sea life and flourishing fish populations. Other successes include Coronado Island inside the Loreto marine park and Los Islotes inside Espiritu Santo marine park.
Using compressed air has been banned in Mexico for sports fishermen for 40 years, but since commercial fishermen weren’t named specifically they had been allowed to use compressed air to clean the reef. In May 2009 this changed: the use of hookahs have now been outlawed for any type of fishing. Illegal fishing still goes on though, and environmental organisation Sea Watch is asking people to report any that they encounter at http://seawatch.org/en/Resource-Library/359/report-illegal-fishing
Further Reading:
Scripps Institution of Oceanography
Labels: dive destination, environment, research, SCUBA diving, SCUBA News, SCUBA Travel
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20 January 2010
Red Grouper create home for many animals
Researchers from Florida State University have found that Red Grouper (Epinephelus morio) dig out and maintain complex structures at the bottom of the sea. They remove sand, exposing hard rocks that are crucial to corals and sponges and the animals that rely on them. The work demonstrates that Red Groupers modify their environment, much as beavers do, creating habitat for many other animals including lobster and commercially important fish."Watching these fish dig holes was amazing enough,” says Felicia Coleman, lead researcher, “but then we realised that the sites served to attract mates, beneficial species such as cleaner shrimp that pick parasites and food scraps off the resident fish and a variety of prey species for the Red Grouper. So it's no surprise that the fish are remarkably sedentary. Why move if everything you need comes to you?”
“The research is incredibly valuable because it demonstrates how interconnected species are in the sea,” says Dr. Susan Williams, a professor at the University of California, Davis. “Red Groupers are the 'Frank Lloyd Wrights' of the sea floor because they are critical habitat architects. The species that associate with them include commercially valuable species- such as vermilion snapper, black grouper, and lobsters. If the groupers are overfished, the suite of species that depends on them is likely to suffer.”
Working along the West Florida Shelf, the authors observed the excavating behaviour of the Red Grouper during both their juvenile stage in inshore waters as their adult stage at depths of 100 m. The study serves to document this behaviour and its apparent impact on the biological diversity of the ocean. Their article on the study, “Benthic Habitat Modification through Excavation by Red Grouper, Epinephelus morio, in the Northeastern Gulf of Mexico,” is published in the most recent issue of the journal The Open Fish Science Journal.
Red Grouper (Epinephelus morio) is an economically important species in the reef fish community of the southeastern United States, and especially the Gulf of Mexico. It is relatively common in karst regions of the Gulf.
As juveniles, Red Grouper excavate the limestone bottom of Florida Bay and elsewhere, exposing “solution holes” formed thousands of years ago when sea level was lower, and freshwater dissolved holes in the rock surface. When sea level rose to its present state, these solution holes filled with sediment. By removing the sediment from these holes, Red Grouper restructure the flat bottom into a three dimensional matrix.
Spiny lobsters are among the many species that occupy these excavations, especially during the day when they need refuge from roving predators.
“What are the consequence of overfishing these habitat engineers?” asks co-author Koenig. “You can't remove an animal that can dig a hole five meters across and several meters deep to reveal the rocky substrate and expect there to be no effect on reef communities. The juveniles of a species closely associated with these pits, vermilion snapper, are extremely abundant around the offshore excavations. It is possible that the engineered habitat is significant as a nursery for this species, which other big fish rely on as food. One could anticipate a domino effect in lost diversity resulting from the loss of Red Grouper-engineered habitat.”
Red Grouper clearly remove sufficient sediment to transform an otherwise two-dimensional area into a three-dimensional structure below the seafloor, providing refuge for themselves and for other organisms. In the process, they expose hard substrate, thus creating settlement sites for corals, sponges, and anemones, allowing the creation of three-dimensional structure above the seafloor as well. Addition of these roles to their contribution as resident top predators suggests that they might have a disproportionately large per capita influence on the ecosystem within which they live.
Red Grouper have been harvested in the United States since the 1880s and are currently the most common grouper species landed in both commercial and recreational fisheries of the Gulf of Mexico.
Excessive fishery removals can and often do have cascading effects in marine communities that ultimately result in the loss of many species. This situation arises when the captured species has a disproportionately large influence on the system within which it lives. The Red Grouper has been shown to be one such species.
Further Reading:
Benthic Habitat Modification through Excavation by Red Grouper, Epinephelus morio, in the Northeastern Gulf of Mexico
pp.1-15 (15) Authors: Felicia C. Coleman, Christopher C. Koenig, Kathryn M. Scanlon, Scott Heppell, Selina Heppell, Margaret W. Miller
doi: 10.2174/1874401X01003010001
Florida State University
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Labels: America, coral, fish, marine biology, research, SCUBA News
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19 January 2010
Minke Whales Should Not be Culled
Antarctic minke whales are among the few species of baleen whales not decimated by commercial whaling during the 20th century, and some scientists have hypothesised that their large numbers are hampering the recovery of deleted species, such as blue, fin and humpback, which may compete for krill.
This “Krill Surplus Hypothesis” postulates that the killing of some two million whales in the Southern Ocean during the early- and mid-20th century resulted in an enormous surplus of krill, benefiting the remaining predators, including Antarctic minke whales.
But the new analysis, published this week in the journal Molecular Ecology, estimates that contemporary populations of minke whales are not “unusually abundant” in comparison with their historic numbers.
The Southern Ocean is one of the world’s largest and most productive ecosystems and in the 20th century went through what Scott Baker, a whale geneticist at Oregon State University, called “one of the most dramatic ‘experiments’ in ecosystem modification ever conducted.” The elimination of nearly all of the largest whales – such as the blue, fin and humpback – removed a huge portion of the biomass of predators in the ecosystem and changed the dynamics of predator-prey relationships.
Blue whales were reduced to about 1-2 percent of their previous numbers; fin whales to about 2-3 percent; and humpbacks to less than 5 percent. “The overall loss of large whales was staggering,” Baker said.
“It is possible that the removal of the larger whales would have meant more food for minkes,” Baker said, “but we don’t know much about the historic abundance of krill and whether the different whale species competed for it in the same places, or at the same time. It is possible that there might have been enough krill for all species prior to whaling.”
The scientists also say that current minke whale populations may be limited by other factors, including changes in sea ice cover.
“The bottom line is that the Krill Surplus Hypothesis does not appear to be valid in relation to minke whales and increasing hunting based solely on the assumption that minke whales are out-competing other large whale species would be a dubious strategy,” Baker said.
Further Reading: Oregon State University
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10 December 2009
IUCN warns of acid oceans
Increased release of carbon dioxide in the atmosphere is making seawater more acidic and is threatening ecosystems and species. It is also reducing the ocean’s ability to absorb carbon dioxide and regulate climate. According to IUCN (International Union for Conservation of Nature), deep and immediate cuts in emissions are needed to stall the acidification of oceans and prevent mass extinction of marine species.There can be little doubt that the ocean is undergoing dramatic changes that will impact many human lives now and in coming generations, unless we act quickly and decisively. Previous episodes of ocean acidification were linked to mass extinctions of some species and it is reasonable to assume that this episode could have the same consequences.
The ocean provides about half of the Earth’s natural resources and humankind takes direct advantage of this through our fisheries and shellfisheries. The ocean also absorbs 25 percent of all the carbon dioxide we emit each year, and produces half the oxygen we breathe.
Ocean acidity has increased by 30 percent since industrialisation began 250 years ago. If CO2 levels in the atmosphere continue to rise, sea water acidity could increase by 120% by 2060 – greater than anything experienced in the past 21 million years. By 2100, 70% of cold water corals may be exposed to corrosive water.
Given the lag between CO2 emissions and a stabilisation of acidification, it could take tens of thousands of years before the ocean’s properties are restored and even longer for full biological recovery. This demands immediate and substantial emissions cuts and technology that actively removes CO2.
“There is an increasingly real and very urgent need to dramatically cut emissions. The ocean is what makes Earth habitable and different from anywhere else we know in our solar system and beyond – now’s the time to act to minimise the impacts on our life support system while we still have time,” says Carl Gustaf Lundin, Head of IUCN’s Global Marine Programme.
Further Reading
Ocean Acidification - The Facts.
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7 December 2009
King Crab Family Grows
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The new species are Paralomis nivosa from the Philippines, P. makarovi from the Bering Sea, P. alcockiana from South Carolina, and Lithodes galapagensis from the Galapagos archipelago – the first and only king crab species yet recorded from the seas around the Galapagos Islands.
King crabs were first formally described in 1819. They include some of the largest crustaceans currently inhabiting the Earth. They are known from subtidal waters in cooler regions, but deep-sea species occur in most of the world’s oceans, typically living at depths between 500 and 1500 metres.
Many more species of King Crab remain to be discovered. “The oceans off eastern Africa, the Indian Ocean and the Southern Ocean are all particularly poorly sampled,” said Hall: “We need to know which king crab species live where before we can fully understand their ecology and evolutionary success.”
Further Reading
National Oceanography Centre, Southampton
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2 December 2009
'Shocking' 95% Decline of Fish Populations
Populations of numerous migratory fish species - those that move between freshwater and saltwater during the course of their lives - have declined by more than 95 percent in the North Atlantic . This threatens food supplies and economic systems, and is worse than was thought as people have tended to compare numbers over too short time scales, according to a paper published this month in the journal BioScience. "It's shocking," said Dr. Karin Limburg, a fisheries ecologist at the SUNY College of Environmental Science and Forestry in Syracuse, N.Y., who is the paper's lead author.
Limburg and her co-author report that a combination of habitat loss (caused largely by the construction of dams that prevent fish access to traditional spawning areas), urban sprawl, overfishing, pollution and climate change have led to the precipitous decline. Compounding the problem, they say, is the evolving knowledge of the humans who make decisions about how natural resources are managed.
"We're looking at shifting baselines here," Limburg said. "Every human generation gains knowledge about the world and establishes a baseline for what's normal. But there is no institutional memory about how things used to be."
As an example, Limburg pointed to a graph that depicts the status of the American shad between 1887 and 1997. It indicates the species was more than 10 times as plentiful during most of the early years of that period as it was during the middle of the 20th century. But a second chart shows that the levels in the 1880s were just 10 percent of what they had been 50 years earlier.
"We can't envision salmon being a thing of the past," she said. "That was once the case with shad. It was the most important fish in U.S. fisheries, after cod." In fact, the shad's Latin name (Alosa sapidissima) reflects the species' high status as a food fish: "sapidissima" means "most delicious."
In their findings, the authors wrote: "Loss of historical baselines contributes to marginalization of the species, as social customs relating to bygone (collapsed) fisheries also perish, and ecosystems unravel at rates that go unnoticed."
Declines were seen in all but two of the fish populations studied. Striped bass, already the subject of protective measures, increased in North America, and lampreys were found to be more abundant in some rivers in France.
The analysis showed that the once-abundant allis shad, a member of the herring family that lives most of its life in coastal waters but migrates into rivers to spawn, plummeted by 99.9 percent in the Rhine River in the Netherlands between 1886 and 1933; the same species dropped by 99.4 percent in the Minho River in Portugal between 1925 and 1988. The European eel's population plunged 95.4 percent in the Ems River, which flows through the Netherlands and Germany, and in the Vidå River in Denmark between 1960 and 1997; it decreased by 99.5 percent in the Yser River in Belgium between 1974 and 2004
When viewed as a group, the magnitude of the migratory species' declines appears even more serious than that of marine predatory fishes, which has received far more attention, Limburg said.
She said the study highlights the importance of a relatively new school of thought in the scientific community: ecosystem services.
"We want to put this in the context of the new way many ecologists are now thinking, to say that ecosystems have a value by themselves," Limburg said.
In particular, she said, the study highlights the interwoven relationship between marine and freshwater ecosystems. The two are linked in the North Atlantic by the 24 species of fish whose populations were analyzed; they are migratory fish that move between freshwater and saltwater during the course of their lives. "Sadly, the links are largely broken today because of the enormity of declines in abundances," she said.
The findings were reported after Limburg and Waldman analyzed data formerly reported in scholarly literature and collected over the years by government agencies and management organizations in nations whose waters flow into the North Atlantic basin, which includes the Atlantic Ocean north of the equator, plus the Caribbean Sea and the Gulf of Mexico.
Further Reading:
SUNY College of Environmental Science and Forestry
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Labels: fish, research, SCUBA News
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11 November 2009
Swarms of ocean robots to monitor oil spills
Swarms of miniature robotic ocean explorers that could one day help predict where ocean currents will carry oil spills, and which marine areas should be protected.These autonomous underwater drifters will trace the fine details that can determine underwater ocean currents of a few kilometers. These are important for understanding marine protected areas, algal blooms, oil spills and the path sewage takes after it is pumped into the ocean.
"Maybe there has been an oil spill in the ocean and we want to establish very quickly how and where the spill might move. We are developing the algorithms that will keep a swarm of autonomous underwater explorers (AUEs) coordinated so they can follow the flow of the ocean currents and give us data on the spill as it is moving around," explained Jorge Cortes, a professor in the Mechanical and Aerospace Engineering Department at the UC San Diego Jacobs School of Engineering.
In addition to predicting where oil will travel, scientists can use this information on the flow of ocean currents in order to improve their models—and ultimately their understanding—of how ocean currents operate on the scale of kilometers and what this means for ocean life and for determining where marine protected areas should be established.
According to Jules Jaffe and Peter Franks, the two Scripps Institution of Oceanography researchers, the robot swarms could aid in science’s development of marine protected areas by following currents for determining critical nursery habitats and for tracking harmful blooms of algae.
The project differs from related work on networks of underwater robots in that the robot swarms the UCSD researchers are developing are significantly smaller and less expensive. At the same time, these robot swarms will be far more capable of making use of the information they collect on the fly in order to improve the accuracy of their task at hand.
Small armies of such robots will concurrently map currents and sense the environment. The robots relay their sensed data when they surface.
The robots will work through a system under which several football sized devices are deployed in conjunction with many—tens or even hundreds—of pint-sized underwater explorers. As they move about the ocean, the smaller-sized robots will use acoustic transmissions from the "motherships" to ascertain their positions. Collectively, the entire swarms of robots will help track fine ocean currents and flows that organisms at the small scale, tiny abalone larvae, for example, experience in the ocean.
"AUEs (Autoonomous Underwater Explorers) will give us information and statistics to figure out how the small organisms survive, how they move in the ocean and the physical dynamics they experience as they get around," said Franks. "AUEs should improve our ocean models and eventually allow us to do a better job of following the weather and climate of the ocean, as well as help us understand things like carbon fluxes."
Franks, who conducts research on marine phytoplankton, among other areas, says the new concentration on dense sampling at small scales will help resolve some of the patchiness in understanding the physical and biological properties on those scales.
"Plankton are somewhat like the balloons of the ocean floating around out there," he said. "We are trying to figure out how the ocean works at the scales that matter to the plankton. You put 100 of these AUEs in the ocean and let 'er rip. We'll be able to look at how they spread apart and how they move to get a sense of the physics driving the flow."
Further Reading:
UC San Diego Jacobs School of Engineering
National Science Foundation
Ocean Research Robots: A Future Vision for Ocean Observation
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Labels: environment, research, SCUBA News, technology
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5 November 2009
Tags reveal Great White Sharks' Beat
"White sharks are a large, highly mobile species," said researcher Salvador Jorgensen. "They can go just about anywhere they want in the ocean, so it's really surprising that their migratory behaviors lead to the formation of isolated populations."
Scientists with the Tagging of Pacific Predators (TOPP) program combined satellite tagging, passive acoustic monitoring and genetic tags to study great white sharks (Carcharodon carcharias) in the North Pacific. Details of their study are published in the Proceedings of the Royal Society B.
The fact that the northeastern Pacific white sharks undergo such a consistent, large-scale migration, and that they are all closely related and distinct from other known white shark populations, suggests that it is possible to conduct long-term population assessment and monitoring of these animals.
Barbara Block, professor of marine sciences at Stanford and a coauthor of the paper, said, "Catastrophic loss of large oceanic predators is occurring across many ecosystems. The white sharks' predictable movement patterns in the northeastern Pacific provide us with a super opportunity to establish the census numbers and monitor these unique populations. This can help us ensure their protection for future generations."
The researchers used a combination of satellite and acoustic tags to follow the migrations of 179 individual white sharks between 2000 and 2008. The tags reveal that the sharks spend the majority of their time in three areas of the Pacific: the North American shelf waters of California; the slope and offshore waters around Hawaii; and an area called the "White Shark Cafe," located in the open ocean approximately halfway between the Baja Peninsula and the Hawaiian Islands.
Genetics techniques were used to examine the relationships of the California sharks to all other white sharks examined globally. Studies of maternally inherited mitochondrial DNA sequences show that the populations are distinct, and suggest that the northeastern Pacific population may have been founded by a relatively small number of sharks in the late Pleistocene – within the last 200,000 years or so. The other populations of white sharks are concentrated near Australia and South Africa.
Depletion of top oceanic predators is a pressing global concern, particularly among sharks because they are slow reproducers. White sharks have been listed for international protection under the Convention on International Trade in Endangered Species (CITES) and the World Conservation Union (IUCN). Despite these precautionary listings, trade in white shark products, primarily fins, persists. Information on population and distribution of oceanic sharks is critical for implementing effective management efforts and the absence of such data impedes protection at all scales. Combining electronic tagging and genetic technologies can help protect sharks.
Further Reading:
Salvador J. Jorgensen, Carol A. Reeb, Taylor K. Chapple, Scot Anderson, Christopher Perle, Sean R. Van Sommeran, Callaghan Fritz-Cope, Adam C. Brown, A. Peter Klimley, and Barbara A. Block
Philopatry and migration of Pacific white sharks
Proc R Soc B 2009 : rspb.2009.1155v1-rspb20091155.
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Labels: marine biology, research, SCUBA News, sharks
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9 October 2009
Albatrosses feed with Killer Whales
A miniature digital camera was attached to the backs of four black-browed albatrosses (Thalassarche melanophrys). Results are published online this week in the open-access journal PLoS ONE.
Albatrosses fly many hundreds of kilometers across the open ocean to find and feed upon their prey. Despite the growing number of studies concerning their foraging behaviour, relatively little is known about how albatrosses actually locate their prey. The still images recorded from the cameras showed that some albatrosses actively followed a killer whale (Orcinus orca), possibly to feed on food scraps left by this diving predator. The camera images together with the depth profiles showed that the birds dived only occasionally, but that they actively dived when other birds or the killer whale were present. This association with diving predators or other birds may partially explain how albatrosses find their prey more efficiently in the apparently ‘featureless’ ocean, with a minimal requirement for energetically costly diving or landing activities.
The camera, developed by the National Institute for Polar Research in Tokyo, is removed when the albatross returns to its breeding ground after foraging trips. It is small and weighs 82g. Although the camera slightly changes the aerodynamic shape of the albatross, it didn’t affect the breeding success of the study birds.
Dr Richard Phillips from British Antarctic Survey (BAS) says, “These images are really interesting. They show us that albatrosses associate with marine mammals in the same way as tropical seabirds often do with tuna. In both cases the prey (usually fish) are directed to the surface and then it’s easy hunting for the birds."
The study took place at the breeding colony of black-browed albatrosses at Bird Island, South Georgia in January 2009, as part of a UK-Japan International Polar Year 2007-9 project.
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21 September 2009
Arctic Sea Ice Reaches 2009 Low
While this year's September minimum extent was greater than each of the past two record-setting and near-record-setting low years, it is still significantly below the long-term average and well outside the range of natural climate variability, said NSIDC Research Scientist Walt Meier. Most scientists believe the shrinking Arctic sea ice is tied to warming temperatures caused by an increase in human-produced greenhouse gases being pumped into Earth's atmosphere.
Atmospheric circulation patterns helped the Arctic sea ice spread out in August to prevent another record-setting minimum, said Meier. But most of the 2009 September Arctic sea ice is thin first- or second-year ice, rather than thicker, multi-year ice that used to dominate the region, said Meier.
The minimum 2009 sea-ice extent is still about 620,000 square miles below the average minimum extent measured between 1979 and 2000 -- an area nearly equal to the size of Alaska, said Meier. "We are still seeing a downward trend that appears to be heading toward ice-free Arctic summers," Meier said.
Further Reading:
National Snow and Ice Data Center
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11 September 2009
Rare Algae Saves Caribbean Coral
A rare opportunity has allowed a team of scientists to evaluate corals--and the essential, photosynthetic algae that live inside their cells--before, during, and after a period in 2005 when global warming caused sea-surface temperatures in the Caribbean to rise.The team, led by Penn State biologist Todd LaJeunesse, found that a rare species of algae that is tolerant of stressful environmental conditions proliferated in corals at a time when more sensitive algae that usually dwell within the corals were being expelled.
Certain species of algae have evolved over millions of years to live in symbiotic relationships with species of corals. These photosynthetic algae provide the corals with nutrients and energy, while the corals provide the algae with a place to live.
"There is a fine balance between giving and taking in these symbiotic relationships," said LaJeunesse.
Symbiodinium trenchi is normally a rare species of algae in the Caribbean, according to LaJeunesse. "Because the species is apparently tolerant of high or fluctuating temperatures, it was able to take advantage of a 2005 warming event and become more prolific."
Symbiodinium trenchi appears to have saved certain colonies of coral from the damaging effects of unusually warm water.
"As ocean temperatures rise as a result of global warming, we can expect this species to become more common and persistent," said LaJeunesse. "However, since it is not normally associated with corals in the Caribbean, we don't know if its increased presence will benefit or harm corals in the long term."
If Symbiodinium trenchi takes from the corals more than it gives back, over time the corals' health will decline.
In 2005, sea surface temperatures in the Caribbean rose by up to two degrees Celsius above normal for a period of three to four months, high enough and long enough to severely stress corals.
The process of damaged or dying algae being expelled from the cells of corals is known as bleaching because it leaves behind bone-white coral skeletons that soon will die without their symbiotic partners.
Although Symbiodinium trenchi saved some corals from dying in 2005, LaJeunesse is concerned that the species might not be good for the corals if warming trends continue and Symbiodinium trenchi becomes more common.
"Because Symbiodinium trenchi does not appear to have successfully co-evolved with Caribbean coral species, it may not provide the corals with adequate nutrition," he said.
The research was published in the online version of the journal Proceedings of the Royal Society B on September 9, 2009.
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Labels: Caribbean, coral, environment, marine biology, research, SCUBA News
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15 August 2009
Warming Ocean Contributes to Global Warming
Scientists at the National Oceanography Centre Southampton working in collaboration with researchers from the University of Birmingham, Royal Holloway London and IFM-Geomar in Germany have found that more than 250 plumes of bubbles of methane gas are rising from the seabed of the West Spitsbergen continental margin in the Arctic, in a depth range of 150 to 400 metres.
Methane released from gas hydrate in submarine sediments has been identified in the past as an agent of climate change.
The data were collected from the royal research ship RRS James Clark Ross, as part of the Natural Environment Research Council’s International Polar Year Initiative. The bubble plumes were detected using sonar and then sampled with a water-bottle sampling system over a range of depths.
The results indicate that the warming of the northward-flowing West Spitsbergen current by 1 degree over the last thirty years has caused the release of methane by breaking down methane hydrate in the sediment beneath the seabed.
Professor Tim Minshull, Head of the University of Southampton’s School of Ocean and Earth Science based at the National Oceanography Centre, says: “Our survey was designed to work out how much methane might be released by future ocean warming; we did not expect to discover such strong evidence that this process has already started.”
Graham Westbrook Professor of Geophysics at the University of Birmingham, warns: “If this process becomes widespread along Arctic continental margins, tens of megatonnes of methane per year – equivalent to 5-10% of the total amount released globally by natural sources, could be released into the ocean.”
Journal Reference:
Westbrook, G. K., et al. (2009), Escape of methane gas from the seabed along the West Spitsbergen continental margin, Geophys. Res. Lett., 36, L15608, doi:10.1029/2009GL039191.
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21 July 2009
Fish surveys could be inaccurate
Fish surveys are often conducted by SCUBA divers or snorkellers. A study in the journal Environmental monitoring and assessment has found that these surveys may be inherently inaccurate as snorkellers frighten away the fish they are supposed to be counting.Researchers from at the University of Victoria, Canada, used an underwater video camera to assess how fish abundance, family richness and community composition were affected by snorkellers and divers on a coral reef in Thailand. They found that snorkellers significantly disturbed the fish they were supposed to be recording. The SCUBA divers didn't provoke the same disturbance. However, only 6 divers were involved in the study so the results are not conclusive.
The researchers suggest that the use of a stationary video camera may help cross-check data that is collected by divers and snorkellers to assess the true family composition and document the presence of rare and easily disturbed species.
Journal Reference:
Environ Monit Assess. 2009 Apr 8
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25 June 2009
Third of Pelagic Sharks Threatened with Extinction
The first study to determine the global conservation status of 64 species of open ocean (pelagic) sharks and rays reveals that 32 percent are threatened with extinction, primarily due to overfishing, according to the IUCN Shark Specialist Group.“Despite mounting threats, sharks remain virtually unprotected on the high seas,” says Sonja Fordham, Deputy Chair of the IUCN Shark Specialist Group and Policy Director for the Shark Alliance. “The vulnerability and lengthy migrations of most open ocean sharks mean they need coordinated, international conservation plans. Our report documents serious overfishing of these species, in national and international waters, and demonstrates a clear need for immediate action on a global scale.”The report comes days before Spain hosts an international summit of fishery managers responsible for high seas tuna fisheries in which sharks are taken without limit. It also coincides with an international group of scientists meeting in Denmark to formulate management advice for Atlantic porbeagle sharks.
The study reports the Great Hammerhead (Sphyrna mokarran) and Scalloped Hammerhead (Sphyrna lewini) sharks, as well as Giant Devil Rays (Mobula mobular), as globally Endangered and facing a very high risk of extinction in the wild. Smooth Hammerheads (Sphyrna zygaena), Great White (Carcharodon carcharias), Basking (Cetorhinus maximus), Oceanic Whitetip (Carcharhinus longimanus), two species of Mako (Isurus spp.) and three species of Thresher (Alopias spp.) sharks are classed as globally Vulnerable to extinction ( facing a high risk of extinction in the wild).
Scalloped hammerhead (Sphyrna lewini)
(Image: Simon Rogerson)
Many open ocean sharks are taken mainly in high seas tuna and swordfish fisheries. Once considered only incidental “bycatch”, these species are increasingly targeted due to new markets for shark meat and high demand for their valuable fins, used in the Asian delicacy shark fin soup. To source this demand, the fins are often cut off sharks and the rest of the body is thrown back in the water, a process known as “finning”. Finning bans have been adopted for most international waters, but lenient enforcement standards hamper their effectiveness.
Oceanic Whitetip (Carcharhinus longimanus)
(Image: Simon Rogerson)
Sharks are particularly sensitive to overfishing due to their tendency to take many years to mature and have relatively few young. In most cases, pelagic shark catches are unregulated or unsustainable.
The IUCN Shark Specialist Group is calling on governments to set catch limits for sharks and rays based on scientific advice and the precautionary approach. It further urges governments to fully protect Critically Endangered and Endangered species of sharks and rays, ensure an end to shark finning and improve the monitoring of fisheries taking sharks and rays.
Silky (Carcharhinus falciformis)
(Image: Jeremy Stafford-Deitsch)
The IUCN uses a series of categories to classify species
| EXTINCT | The last individual has died |
| EXTINCT IN THE WILD | Only survives in captivity or cultivation |
| CRITICALLY ENDANGERED | Facing an extremely high risk of extinction in the wild |
| ENDANGERED | Facing a very high risk of extinction in the wild |
| VULNERABLE | Facing a high risk of extinction in the wild |
| NEAR THREATENED | Likely to qualify for, a threatened category in the near future |
| LEAST CONCERN | Does not qualify for any of the above |
is the world’s largest global environmental network. It is a
membership union with more than 1,000 government and
non-governmental member organisations and almost 11,000
volunteer scientists in more than 160 countries.
Further Reading:
The Conservation Status of Pelagic Sharks and Rays: Report of the IUCN Shark Specialist Group Pelagic Shark Red List Workshop
IUCN Red List Categories and Criteria booklet
Related Stories:
EU launches shark protection plan
Caribbean Big Fish Disappearing
Mediterranean Sharks Declining Fast
Mexico Passes Shark Finning Ban
Four Times more Sharks caught than Officially Reported
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Labels: fish, marine biology, research, SCUBA News, sealife, sharks
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21 May 2009
Endangered right whales found where they were thought extinct
Using a system of underwater hydrophones that can record sounds from hundreds of miles away, a team of scientists has documented the presence of endangered North Atlantic right whales in an area they were thought to be extinct.The discovery is particularly important, researchers say, because it is in an area that may be opened to shipping if the melting of polar ice continues, as expected.
Results of the study were presented this week at a meeting of the Acoustical Society of America.
The scientists from Oregon State University and the National Oceanic and Atmospheric Administration are unsure of exactly how many whales were in the region, which is off the southern tip of Greenland and site of an important 19th-century whaling area called Cape Farewell Ground. But they recorded more than 2000 right whale vocalizations in the region from July to December of 2007.
“The technology has enabled us to identify an important unstudied habitat for endangered right whales and raises the possibility that – contrary to general belief – a remnant of a central or eastern Atlantic stock of right whales still exists and might be viable,” said David Mellinger, chief scientist of the project.
“We don’t know how many right whales there were in the area,” Mellinger added. “They aren’t individually distinctive in their vocalizations. But we did hear right whales at three widely space sites on the same day, so the absolute minimum is three. Even that number is significant because the entire population is estimated to be only 300 to 400 whales.”
Only two right whales have been sighted in the last 50 years at Cape Farewell Ground, where they had been hunted to near extinction prior to the adoption of protective measures.
The pattern of recorded calls suggests that the whales moved from the southwest portion of the region in a northeasterly direction in late July, and then returned in September – putting them directly where proposed future shipping lanes would be likely.
Right whales are the most endangered large whale and vulnerable to collisions with ships as they ignore general ship sounds. Alarm sirens intended to scare them away from ships may actually be more likely to cause a collision, as the whales have been shown to rush to the surface when they hear the alarm.
Related News:
Lawsuit Filed to Protect World's Most Endangered Whale
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19 May 2009
Basking shark mystery solved
"While commonly sighted in surface waters during summer and autumn months, the disappearance of basking sharks during winter has been a great source of debate ever since an article in 1954 suggested that they hibernate on the ocean floor during this time," said Gregory Skomal of Massachusetts Marine Fisheries. "Some 50 years later, we have helped to solve the mystery while completely re-defining the known distribution of this species."
Using new satellite-based tagging technology, the researchers found that basking sharks make ocean-scale migrations through tropical waters of the Atlantic Ocean during the winter, travelling at depths of 200 to 1,000 meters. Their data show that the sharks sometimes stay at those depths for weeks or even months at a time.
"In doing so, they have completely avoided detection by humans for millennia," Skomal said
The discovery was the result of marking 25 basking sharks off the coast of Cape Cod with satellite tags and studying their movements. The migratory paths of the sharks were then estimated by coupling tag data with a novel geo-positioning technology technique.
Several factors had made basking sharks a challenge to study. On top of the fact that they disappear for long periods of time, they also feed exclusively on plankton. That means they can't readily be captured with traditional rod-and-reel methods. And even when the sharks are found closer to the ocean surface, they spend their time in the cool-temperature, plankton-rich waters that limit underwater visibility and make diving difficult.
The basking shark is the second largest shark after the whale shark. It filters plankton through its gills whilst swimming with its huge mouth open.
Journal Reference:
Transequatorial Migrations by Basking Sharks in the Western Atlantic Ocean. Skomal, Gregory B.; Zeeman, Stephen I.; Chisholm, John H.; Summers, Erin L.; Walsh, Harvey J.; McMahon, Kelton W.; Thorrold, Simon R.
doi:10.1016/j.cub.2009.04.019
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18 May 2009
World's Largest Leatherback Turtle Population Found
An international team of scientists has identified a nesting population of leatherback sea turtles in Gabon, West Africa as the world's largest.The research, published in the May issue of Biological Conservation, involved country-wide land and aerial surveys that estimated a population of between 15,730 and 41,373 female turtles using the nesting beaches.
The study highlights the importance of conservation work to manage key sites and protected areas in Gabon.
Leatherbacks are of profound conservation concern around the world after populations in the Indo-Pacific crashed by more than 90 percent in the 1980s and 1990s. The International Union for Conservation of Nature (IUCN) lists leatherback turtles as critically endangered globally, but detailed population assessments in much of the Atlantic, especially Africa, are lacking.
During three nesting seasons between 2002 and 2007, the team’s members carried out the most comprehensive survey of marine turtles ever conducted in Gabon. This involved aerial surveys along Gabon’s 600 km (372 mile) coast, using video to capture footage for evaluation, and detailed ground-based monitoring. By covering the entire coastline, they were not only able to estimate the number of nests and nesting females, but also to identify the key sites for leatherback nesting, data which are crucial to developing conservation management plans for the species. Leatherbacks were first described nesting in Gabon in 1984.
The study also revealed that around 79 percent of the nesting occurs within National Parks and other protected areas. This gives added hope that Gabon can continue to be one of the world’s most important countries for these magnificent creatures.
Dr Angela Formia of the Wildlife Conservation Society, a co-author of the paper, said: “These findings show the critical importance of protected areas to maintain populations of sea turtles. Gabon should be commended for creating a network of National Parks in 2002 that have provided a sanctuary for this endangered species as well as other rare wildlife.”
The leatherback is the largest sea turtle, reaching up to nearly two metres (6.5 feet) in length and 540kg (1190 pounds) in weight. Unlike other sea turtles, the leatherback does not have a hard shell. Its shell is made-up of a mosaic of small bones covered by firm, rubbery skin with seven longitudinal ridges. Leatherbacks are the most widely spread marine turtles, and are found in the Pacific, Indian and Atlantic oceans, particularly in tropical regions. They are also the deepest diving of all sea turtles. The deepest recorded dive is 1.2 kilometres (3/4 mile), which is slightly more than the deepest known dive of a sperm whale.
As with other reptiles, the sex of leatherbacks is determined by the temperature of eggs during incubation. With leatherbacks, temperatures above 29 degrees centigrade (84 degrees Fahrenheit) will result in female hatchlings.
Leatherbacks are strong swimmers and tagged individuals have been known to cross ocean basins and are known to travel many thousands of kilometres in search of their jellyfish prey.
To see turtles currently being tracked from Gabon see: http://www.seaturtle.org/tracking/?project_id=340
The research was led by the University of Exeter working in collaboration with the Wildlife Conservation Society (WCS) which spearheads the Gabon Sea Turtle Partnership, a network of organisations concerned with the protection of marine turtles in Gabon.
Related News:
California waters for leatherback turtles?
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Labels: Africa, research, SCUBA News, sealife, turtles
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6 May 2009
Caribbean Big Fish Disappearing
Sharks, barracuda and other large predatory fishes disappear on Caribbean coral reefs as human populations rise, endangering the region's marine food web and ultimately its reefs and fisheries, according to a study published today in the journal PLoS One.While other scientists working in the Caribbean have observed the declines of large predators for decades, the new study by Chris Stallings documents the ominous patterns geographically in much more detail than other research to date.
“I examined 20 species of predators, including sharks, groupers, snappers, jacks, trumpetfish and barracuda, from 22 Caribbean nations,” said Stallings, a postdoctoral associate at the FSU Coastal and Marine Laboratory. “I found that nations with more people have reefs with far fewer large fish because as the number of people increases, so does demand for seafood. Fishermen typically go after the biggest fish first, but shift to smaller species once the bigger ones become depleted. In some areas with large human populations, my study revealed that only a few small predatory fish remain.”
Stallings said that although several factors — including loss of coral reef habitats — contributed to the general patterns, careful examination of the data suggests overfishing as the most likely reason for the disappearance of large predatory fishes across the region. He pointed to the Nassau grouper as a prime example. Once abundant throughout the Caribbean, Nassau grouper have virtually disappeared from many Caribbean nearshore areas and are endangered throughout their range.
“Large predatory fish such as groupers and sharks are vitally important in marine food webs,” Stallings said. “However, predicting the consequence of their loss is difficult because of the complexity of predator-prey interactions. You can't replace a 10-foot shark with a one-foot grouper and expect there to be no effect on reef communities. Shifts in abundance to smaller predators could therefore have surprising and unanticipated effects. One such effect may be the ability of non-native species to invade Caribbean reefs.”
A case in point, said Stallings, is the ongoing invasion by Pacific lionfish, which were introduced by aquarium releases.
“Lionfish are minor players on their native Pacific reefs, yet they are undergoing a population explosion and overeating small fishes in the greater Caribbean region,” said Professor Mark Hixon of Oregon State University, Stallings' doctoral advisor at OSU. “Preliminary evidence suggests that lionfish are less invasive where large predatory native fishes are abundant, such as in marine reserves,” Hixon said.
The study also demonstrates the power of volunteer and community research efforts by non-scientists. Stallings used data from the Reef Environmental Education Foundation's (REEF) online database, which contains fish sightings documented by trained volunteer SCUBA divers, including more than 38,000 surveys spanning a 15-year period.
Further Reading:
Fish predators of the Caribbean: the curse of too many people, Florida State University
Fishery-Independent Data Reveal Negative Effect of Human Population Density on Caribbean Predatory Fish Communities, PLoS One
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Labels: Caribbean, research, SCUBA News, sharks
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22 April 2009
Ocean-Going Robotic Submarine Returns
Under the joint CSIRO Wealth from Oceans National Research Flagship and Integrated Marine Observation System (IMOS) project, the underwater ocean glider was launched in February on a two-month, 1,500 kilometre voyage.
With its porpoising motion and an ability to descend to a depth of nearly 1,000 metres, the $A200,000 robotic glider is being trialled in the Tasman Sea and the Indian Ocean as the latest tool in Australia’s $A94 million marine observing network.
The glider’s sensors measure temperature and salinity, as well a range of biological parameters including oxygen and turbidity.
Senior CSIRO Wealth from Oceans Flagship researcher Ken Ridgway, says the Tasman Sea trial has generated new confidence among scientists broadening the array of instruments available to them to better understand the East Australian Current and Leeuwin Currents.
“Ocean currents around Australia are critical to so many aspects of nature and human activity,” Mr Ridgway says. “With the East Australian and Leeuwin Currents, we need to understand how they change from season to season and year to year, and the extent of their influence on local coastal conditions, as this affects climate, weather, fisheries, shipping and more.
Together with data from research vessels, satellites and moored, drifting and expendable instruments, the glider will add a new dimension to profiling the oceans around Australia. But there are still challenges to be overcome.
“In a lot of ways this first deployment is as much learning how to pilot the glider and guide it through and around the eddies of the East Australian Current as it is getting about the data we want,” Mr Ridgway says.
A recent innovation in oceanography, the winged gliders are programmable and guided by Global Positioning Systems. They glide during depth changes, driven by an inflated oil filled chamber. However, because the ocean currents can be faster than the glider’s speed, ensuring they are not swept away has been a difficult process.
“The appeal of these instruments is that they are out working while the scientist can be assessing what is near-real time information about ocean conditions,” Mr Ridgway says.
Stories like this:
Robotic sea glider flies through water
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27 March 2009
Crabs feel and remember pain
New research published by a Queen's University academic has shown that crabs not only suffer pain but that they retain a memory of it.The study, published in the journal Animal Behaviour, looked at the reactions of hermit crabs to small electric shocks. It was was carried out by Professor Bob Elwood and Mirjam Appel from the School of Biological Sciences at Queen's University Belfast.
Professor Elwood, who previously carried out a study showing that prawns endure pain, said his research highlights the need to investigate how crustaceans used in food industries are treated.
Hermit crabs have no shell of their own so inhabit other structures, usually empty mollusc shells. When the crab becomes to large for its current shell, it looks for another. When it finds a likely looking one, it will try it on. If the shell doesn't fit, or is too heavy, the crab returns to its old shell and continues it search. Where there is a large population of hermit crabs and a shortage of shells, the crab will accept a sub-standard home: maybe a cracked or uncomfortable shell. But in good conditions it will be very particular about the new shell it chooses.
During the research wires were attached to shells to deliver the small shocks to the abdomen of the some of the crabs within the shells.
The only crabs to get out of their shells were those which had received shocks, indicating that the experience is unpleasant for them.
Hermit crabs are known to prefer some species of shells to others and it was found that that they were more likely to come out of the shells they least preferred. This shows that central neuronal processing occurs rather than the response merely being a reflex. They traded-off between keeping a good shell and acceptance of the shock.
Crabs that had been shocked but had remained in their shell appeared to remember the experience of the shock because they quickly moved towards the new shell, investigated it briefly and were more likely to change to the new shell compared to those that had not been shocked.
Professor Elwood said: “There has been a long debate about whether crustaceans including crabs, prawns and lobsters feel pain. “We know from previous research that they can detect harmful stimuli and withdraw from the source of the stimuli but that could be a simple reflex without the inner ‘feeling’ of unpleasantness that we associate with pain.
“This research demonstrates that it is not a simple reflex but that crabs trade-off their need for a quality shell with the need to avoid the harmful stimulus.
“Such trade-offs are seen in vertebrates in which the response to pain is controlled with respect to other requirements.
“Humans, for example, may hold on a hot plate that contains food whereas they may drop an empty plate, showing that we take into account differing motivational requirements when responding to pain.
“Trade-offs of this type have not been previously demonstrated in crustaceans. The results are consistent with the idea of pain being experienced by these animals.”
Professor Elwood says that in contrast to mammals, little protection is given to the millions of crustaceans that are used in the fishing and food industries each day. He added "Millions of crustacean are caught or reared in aquaculture for the food industry. There is no protection for these animals (with the possible exception of certain states in Australia) as the presumption is that they cannot experience pain.
Journal Reference:
Robert W. Elwood and Mirjam Appel, Pain experience in hermit crabs?, Animal Behaviour (2009), doi:10.1016/j.anbehav.2009.01.028.
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24 March 2009
Deep-sea corals live thousands of years
Deep-sea corals are found on hard substrates on seamounts and continental margins worldwide at depths of 300 to around 3000 m. Deep-sea coral communities are hotspots of living things, both in terms of numbers and diversity of species. They provide critical habitat for fish and invertebrates. According to research published this week in the Proceedings of the National Academy of Sciences, newly applied radiocarbon dating of the deep water corals Gerardia and Leiopathes species show that their growth rates are extremely low, and that individual colonies live for thousands of years. The longest-lived specimens were Leiopathes species (black corals) at 4265 years old.
The coral specimens were collected with submersibles off the coast of Hawaii. The authors measured the age of the corals' proteinaceous skeleton and found that the corals grew much more slowly than previous dating techniques had shown.
The management and conservation of deep-sea coral communities is challenged by their commercial harvest for the jewellery trade and damage caused by deep-water fishing practices.
The scientists conclude that in light of the corals' unusual longevity, we need to better understand their ecology and relationship with other bottom-dwelling creatures before forming a coherent international conservation strategy for these important deep-sea habitat-forming species.
Black Corals
Leiopathes black corals have a dark skeleton, after which they are named. The black skeleton forms irregularly branching, tree-like structures. Gorgonian-like, the skeleton is covered with polyps. Leiopathes corals are listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), which means that they are not necessarily now threatened with extinction now but that may become so unless trade is closely controlled. Gerardia species are sometimes known as False Black Corals. Not all of these are deep sea: colonies are found in the Mediterranean between 50 and 80 m.
Journal References:
E. Brendan Roark, Thomas P. Guilderson, Robert B. Dunbar, Stewart J. Fallon, and David A. Mucciarone. Extreme longevity in proteinaceous deep-sea corals. PNAS 2009 : 0810875106v1-pnas.0810875106.
E. Brendan Roark, Thomas P. Guilderson, Robert B. Dunbar and B. Lynn Ingram. Radiocarbon-based ages and growth rates of
Hawaiian deep-sea corals. MARINE ECOLOGY PROGRESS SERIES, Vol. 327: 1–14, 2006
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Fins evolved from gills, research suggests
Andrew Gillis, lead author of the paper, says "This new finding is consistent with an old theory, often discounted in science textbooks, that fins and (later) limbs evolved from the gills of an extinct vertebrate. A dearth of fossils prevents us from definitely concluding that fins evolved from gills. Nevertheless, this research shows that the genetic architecture of gills, fins and limbs is the same.”
The research builds on the breakthrough discovery of the fossil Tiktaalik, a "fish with legs," by Neil Shubin and his colleagues in 2006.
According to the researchers, the genetic circuitry that patterns paired appendages (arms, legs and fins) has a deep evolutionary origin that actually predates the origin of paired appendages themselves.
They found that treating a skate embryo (a relative of the shark) with Vitamin A's retinoic acid, affected the gill arch skeleton in the same way as an arm, leg or fin skeleton.
The deep structural, functional and regulatory similarities between paired appendages and developing gill rays, as well as the antiquity of gills relative to paired appendages, suggest that the signalling network that is induced by retinoic acid had a patterning function in gills before the origin of vertebrate arms, legs or fins, the research concludes. And this function has been retained in the gill rays of living cartilaginous fishes like skates, rays and sharks.
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17 March 2009
97% of Divers disturb seabed: Males worst offenders
Most SCUBA divers disturb the seabed, Spanish researchers say. A study published in the ICES Journal of Marine Science found that nearly 97% of divers in marine protected areas (MPAs) made contact with the bottom. Inexperienced, male divers carrying a camera or torch were the worst offenders.Creating a marine protected area tends to increase diving in that vicinity. Scientists from the University of Alicante studied the behaviour of divers in marine protected areas, the effects of diving on the natural environment and the characteristics that influence diver behaviour. They found that impacts caused by recreational scuba activity vary widely among different divers.
The scientists followed a total of 181 recreational divers in Mediterranean MPAs, recording the contacts they made with the seabed and the effects produced. They also made notes on the features of the dive. Their observations revealed that 175 of the divers observed (96.7%) made at least one contact with the seabed. Flapping was the most frequent type of contact, and the main damage by this action was to raise sediment.
Contact with the seabed was greater for males than for females, inexperienced divers than for experienced divers, camera or dive light users than for non-users, and divers unaccompanied by a dive leader or who had not been briefed about avoiding seabed contact before undertaking a dive than for accompanied or briefed divers.
The research team hopes that a greater understanding of the causes of harmful behaviour may be useful for stricter management, reducing diving damage and assuring the sustainability of diving in marine protected areas.
Journal Reference:
Luna, B., Valle Pérez, C., and Sánchez-Lizaso, J. L. 2009. Benthic impacts of recreational divers in a Mediterranean Marine Protected Area. – ICES Journal of Marine Science, 66: 000–000.
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16 February 2009
Ocean Survey Finds Identical Species at each Pole
Among many other findings, the scientists also documented evidence of cold waterloving species shifting towards both poles to escape rising ocean temperatures.
“The polar seas, far from being biological deserts, teem with an amazing quantity and variety of life,” says Dr. Ian Poiner, Chair of the Census Scientific Steering Committee.
Researchers say smaller marine species are replacing larger ones in some Arctic waters. The reasons behind the shift are obscure but the implications for the Arctic food web may be profound.
New technologies are dramatically speeding Census research into the abundance, diversity and distribution of marine biodiversity. Census researchers are using cell phone-like devices to learn about the distribution of large animals at both poles. For example, tracking devices fitted to narwhals, to record their Arctic migrations and provide as a byproduct a wealth of rich data on the status of polar oceans. SCUBA divers were deployed for observations in heavy Arctic ice and advanced, deep water optical systems on Remotely Operated Vehicles (ROVs) enabled detailed studies of delicate marine animals too fragile to collect. And DNA sequences, or barcodes, will dramatically accelerate the cataloguing of life’s diversity, helping to identify new and cryptic species.
The polar marine explorers were startled when molecular techniques revealed that glacial cycles over millions of years made the Antarctic the cold incubator of many species residing today in more northern waters.
Scientist theorise that the Antarctic regularly refreshes the world’s oceans with new varieties of sea spiders, isopods (crustaceans related to shrimp and crabs) and others. They believe the new species evolve when expansions of ice cloister Antarctica; when the ice retreats, they radiate northward.
Previously thought to be low in species diversity and abundance, researchers have amassed biological data from nearly 1 million locations. Those places include seafloors exposed to light for the first time in as much as 100,000 years when ancient ice shelf lids melted and disintegrated in recent years.
Further Reading:
Census of Marine Life
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8 January 2009
CO2 emissions harm jumbo squid
The researchers subjected the squids (Dosidicus gigas) to elevated concentrations of CO2 equivalent to those likely to be found in the oceans in 100 years due to anthropogenic emissions. They found that the squid’s routine oxygen consumption rate was reduced under these conditions, and their activity levels declined, presumably enough to have an effect on their feeding behavior.
Jumbo squid are an important predator in the eastern Pacific Ocean, and they are a large component of the diet of marine mammals, seabirds and fish.
According to Seibel, jumbo squid migrate between warm surface waters at night where CO2 levels are increasing and deeper waters during the daytime where oxygen levels are extremely low.
“Squids suppress their metabolism during their daytime foray into hypoxia, but they recover in well-oxygenated surface waters at night,” he said. “If this low oxygen layer expands into shallower waters, the squids will be forced to retreat to even shallower depths to recover. However, warming temperatures and increasing CO2 levels may prevent this. The band of habitable depths during the night may become too narrow.”
Carbon dioxide enters the ocean via passive diffusion from the atmosphere in a process called ocean acidification. This phenomenon has received considerable attention in recent years for its effects on calcifying organisms, such as corals and shelled mollusks, but the study by Seibel and Rosa is one of the first to show a direct physiological effect in a non-calcifying species.
The scientists speculate that the squids may eventually migrate to more northern climes where lower temperatures would reduce oxygen demand and relieve them from CO2 and oxygen stress. While it is possible, they say, that the squids could adjust their physiology over time to accommodate the changing environment, jumbo squids have among the highest oxygen demands of any animal on the planet and are thus fairly constrained in how they can respond.
“We believe it is the blood that is sensitive to high CO2 and low pH,” Seibel said. “This sensitivity allows the squids to off-load oxygen more effectively to muscle tissues, but would prevent the squid from acquiring oxygen across the gills from seawater that is high in CO2.”
While many other squid and octopus species have oxygen transport systems that are equally sensitive to pH, few have such high oxygen demand coupled with large body size and low environmental oxygen. Therefore the scientists believe that their study results should not be extrapolated to other marine animals.
Further reading: University of Rhode Island
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21 November 2008
Computers decide when to stop searches at sea
The Search and Rescue Survival Model has been designed to take the pressure off rescuers making difficult decisions about when a search and rescue mission should be stopped.
“Using this new computer model will take pressure off humans making very emotional and sensitive decisions about when to end a search,” said Professor Mike Tipton, human and applied physiologist, from the University of Portsmouth.
“When the model predicts that a victim can no longer survive, the search and rescue team can stop or redeploy the search.
“It will ensure that Coast Guard personnel are not exposed to the high risks associated with search and rescue operations any longer than necessary and will also help to save time and resources,” he said.
The US Coast Guard currently uses a software system known as SAROPS (Search and Rescue Optimal Planning System) to calculate how far a person will have drifted and how large the search area should be.
Data such as wind speed, sea state and water temperature is entered into SAROPS along with information about the victim’s sex, height, weight and what they were wearing to determine exactly how the search should be conducted.
“Calculating survival time will add another layer to SAROPS; it will be able to predict not only where a search should be conducted but when it should be stopped,” said Professor Tipton.
“The University of Portsmouth has been able to tap into and analyze data held by the Institute of Naval Medicine and the Royal National Lifeboats Institution, both critical to the development of this survival model. To our knowledge no other similar repository of this information exists - even in the US.
“The development of this technology is very exciting. It will be trialled in American waters in late 2009 and once thoroughly tested, the aim is to roll it out to the whole of the US,” he said.
Labels: America, research, SCUBA diving, USA
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12 November 2008
Sea snakes drink only freshwater
Sea snakes may slither in saltwater, but they sip the sweet stuff.
So concludes a University of Florida zoologist in a paper appearing this month in the online edition of the November/December issue of the journal Physiological and Biochemical Zoology.
Harvey Lillywhite says it has been the “long-standing dogma” that the roughly 60 species of venomous sea snakes worldwide satisfy their drinking needs by drinking seawater, with internal salt glands filtering and excreting the salt. Experiments with three species of captive sea kraits captured near Taiwan, however, found that the snakes refused to drink saltwater even if thirsty — and then would drink only freshwater or heavily diluted saltwater.
“Our experiments demonstrate they actually dehydrate in sea water, and they’ll only drink freshwater, or highly diluted brackish water with small concentrations of saltwater — 10 to 20 percent,” Lilywhite said.
Harold Heatwole, a professor of zoology at North Carolina State University and expert on sea snakes, termed Lillywhite’s conclusion “a very significant finding.”
“This result probably holds the key to understanding the geographic distribution of sea snakes,” Heatwole said.
The research may help explain why sea snakes tend to have patchy distributions and are most common in regions with abundant rainfall, Lillywhite said. Because global climate change tends to accentuate droughts in tropical regions, the findings also suggest that at least some species of sea snakes could be threatened now or in the future, he added.
“There may be places where sea snakes are barely getting enough water now,” he said. “If the rainfall is reduced just a bit, they’ll either die out or have to move.”
Sea snakes are members of the elapid family of snakes that also includes cobras, mambas and coral snakes. They are thought to have originated as land-dwelling snakes that later evolved to live in oceans. Most spend all, or nearly all, of their lives in seawater, including giving birth to live young while swimming. A minority, including the kraits that Lillywhite studied, lay eggs and spend at least a small part of their lives on land.
Lillywhite believes the sea snakes that spend their lives in the open ocean drink water from the “lens” of freshwater that sits atop saltwater during and after rainfall, before the two have had a chance to mix. That would explain why some seawater lagoons, where the waters are calmer due to protection from reefs, are home to dense populations of sea snakes — the freshwater lens persists for longer periods before mixing into saltwater.
Rather than helping sea snakes gain water, the snakes’ salt gland may help the snakes with ion balance — moving excess salts from the bloodstream, Lillywhite said.
Some sea snake species living in dry regions may already be suffering as a result of climate change. Lillywhite said a colleague in Australia, which is in the midst of a historic drought, has observed declines and possible extinctions in some species at Ashmore Reef, home to the most diverse and abundant population of sea snakes in the world.
“We are trying to look at rainfall in that region and see if there is a correlation,” Lillywhite said.
He added that his findings also raise questions about the accepted wisdom that other marine reptiles, including sea turtles, satisfy their freshwater needs by drinking saltwater.
Labels: environment, marine biology, research
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22 September 2008
The Secrets of Effective Communication beneath the Sea
If researchers can better understand how physical conditions like these distort sound as it travels through the ocean, they could send data underwater faster and with less power and could make it much easier for networks of sensors to talk to each other simultaneously. They could improve wireless communications from commonly used ocean instruments such as Doppler current profilers and potentially eliminate the need for vehicles and gliders to surface just to transmit modest amounts of data.
With these goals on the horizon, a science team led by Scripps Institution of Oceanography at UC San Diego researchers have completed a three-week study of waters west of the Hawaiian island of Kauai.
The research team inventoried the suite of conditions that can disrupt a signal as it travels between two underwater points. The team recorded wind speed and surface wave measurements to gauge the structure of the sea surface and temperature profiles to estimate sound speed (the colder the water, the slower sound travels), and measured the topography of the seafloor.
Principal investigator, Bill Hodgkiss, rated the experiment a major success and said its data could enhance computer models used to guide development of underwater acoustic modems-especially for use in places less accessible than Kauai.
"This experiment should improve prediction of the fluctuation characteristics in other environments that scientists don't necessarily have the resources to go and study," Hodgkiss said.
Further Reading: explorations
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19 September 2008
Reef Search Finds Hundreds of New Species
The expeditions, affiliated with the global Census of Marine Life, help mark the International Year of the Reef and included the systematic scientific inventory of spectacular soft corals.
The discoveries were made at Lizard and Heron Islands (part of the Great Barrier Reef), and Ningaloo Reef in northwestern Australia. The found about 300 soft coral species, up to half of them thought to be new to science; dozens of small crustacean species -- and potentially one or more families of species – likewise thought unknown to science; The beautiful, rare Cassiopeia jellyfish, photographed upside down on the ocean
floor, tentacles waving in the water column -- a posture that enables symbiotic
algae living in its tentacles to capture sunlight for photosynthesis.
Preparing for future discoveries, the divers pegged several layered plastic structures – likened to empty doll houses – for marine life to colonize on the ocean floor at Lizard and Heron Islands. Creatures that move into these Autonomous Reef Monitoring Structures (ARMS), which provide shelter designed to appeal to a variety of sea life, will be collected over the next one to three years.
"Corals face threats ranging from ocean acidification, pollution, and warming to overfishing and starfish outbreaks," says Dr. Ian Poiner, Chief Executive Officer of the Australian Institute of Marine Science (AIMS), which led the research. "Only by establishing a baseline of biodiversity and following through with later censuses can people know the impact of those threats and find clues to mitigate them."
Ningaloo Reef appears to be the least biodiverse of the three sites studied, which may be related to its comparative isolation from other reef systems.
Understanding these biodiversity gradients and the influence of connectivity will help scientists predict reef biodiversity worldwide.
Expeditions to the same three sites will be repeated annually over the next three years to continue their inventory and measure impacts of climate change and other processes over time.
The addition of perhaps as many as 150 new species to the global inventory of soft corals is a major addition to the knowledge of this group which, despite its high distribution worldwide, remains one of the most poorly understood groups.
The scientists' studies also included seaweeds, urchins, and lace corals. More formally known as Bryozoans, lace coral colonies consist of asexually budded (and therefore genetically identical) individuals. Colonies form large intricate structures which bear no resemblance to the structure of the individual.
The Census of Marine Life (www.coml.org) is a global network of researchers in more than 80 nations engaged in a 10-year initiative to assess and explain the diversity, distribution, and abundance of marine life in the oceans – past, present, and future. The network will release the first Census of Marine Life in 2010.
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20 August 2008
Seals help unlock ocean secrets
Sensors developed by the University of St Andrews have been employed by Antarctic researchers to collect otherwise inaccessible information about the climate. The small data logging transmitters have been attached to the heads of elephant seals.
Scientists usually collect data to characterise the ocean using satellite sensing, buoyant floats, and ship expeditions, but winter sea ice renders the Southern Ocean virtually impermeable to all three.
Professor Mike Fedak from the University's Gatty Marine Laboratory said, "The Southern Ocean is a hotspot for climate research because its circulation is critical to understanding the earths climate and its huge ice sheet is sensitive to climate change.
"Southern elephant seals are wide-ranging predators that roam all over the Southern Ocean, even under the sea ice in the wintertime - a time when conventional ocean observation methods are unable to gather data."
The instruments measure temperature, pressure, and salinity and transmit data as well as seal positions to satellites when the seals surface. From this, researchers are able to amass data for a vast range of hitherto inaccessible ocean, including areas deep within the sea-ice in winter while also learning about the animals themselves.
This new data has enabled them to follow the yearly rise-and-fall cycle of sea ice production, and should help scientists refine computer models of the Southern Ocean circulation.
Led by Dr Jean-Benoit Charrassin, a marine biologist at the Natural History Museum in Paris, researchers in France, the UK, Australia and the US have attached electronic dataloggers to 70 seals at the four most important breeding colonies of southern elephant seals.
The species can dive as deep as 2 km in search of food while ranging across much of the southern ocean. Thanks to this innovative technology, the only remaining area with limited coverage is the Pacific sector, which contains no islands for the seals to breed on.
Professor Fedak explained, "I think this is an extremely exciting new approach for ocean observation which has now been extended to seals roaming the seas around both Poles as part of the International Polar Year (IPY)."
The on-going MEOP project (Marine Mammals Exploring the Oceans Pole to Pole) has equipped 100 seals of 3 polar species with oceanographic sensors and these animals are now routinely sending large quantities of near real-time information from the undersampled polar regions.
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Labels: environment, research
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