Image of the week : Bahamas blue

The beauty of the Bahamas is surreal; every blue that exists.

Taken on New Year's Day, 2013 by Chris Hatfield, commander on the International Space Station

pic.twitter.com/cnNPh8Xl

Where is the picture ?
Explore the Bahamas islands with the Marine GeoGarage 
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Flying sailing : Oracle Team USA AC72 - Progress and Evolution

Now that ORACLE TEAM USA "17" is comfortably back on it's boards and flying high,

attention turns to the constant state of development for both sailors and shore crew alike.

Image of the week : satellite’s view of ship pollution

This map is based on OMI measurements acquired between 2005 and 2012.

The NO2 signal is most prominent in an Indian Ocean shipping lane between Sri Lanka and Singapore, appearing as a distinct orange line against (lighter) background levels of NO2.

Other shipping lanes that run through the Gulf of Aden, the Red Sea and the Mediterranean Sea also show elevated NO2 levels, as do routes from Singapore to points in China.

From NASA

For more than a decade, scientists have observed “ship tracks” in natural-color satellite imagery of the ocean.
These bright, linear trails amidst the cloud layers are created by particles and gases from ships.
They are a visible manifestation of pollution from ship exhaust, and scientists can now see that ships have a more subtle, almost invisible, signature as well.

Data from the Dutch and Finnish-built Ozone Monitoring Instrument (OMI) on NASA’s Aura satellite show long tracks of elevated nitrogen dioxide (NO2) levels along certain shipping routes. NO2, is among a group of highly-reactive oxides of nitrogen, known as NOx, that can lead to the production of fine particles and ozone that damage the human cardiovascular and respiratory systems. Combustion engines, such as those that propel ships and motor vehicles, are a major source of NO2 pollution.

The map above is based on OMI measurements acquired between 2005 and 2012.
The NO2 signal is most prominent in an Indian Ocean shipping lane between Sri Lanka and Singapore, appearing as a distinct orange line against (lighter) background levels of NO2.
Other shipping lanes that run through the Gulf of Aden, the Red Sea, and the Mediterranean Sea also show elevated NO2 levels, as do routes from Singapore to points in China.
These aren’t the only busy shipping lanes in the world, but they are the most apparent because ship traffic is concentrated along narrow, well-established lanes.

The Atlantic and Pacific Oceans also have heavy ship traffic, but OMI doesn’t pick up NO2 pollution tracks because the shipping routes are less consistent.
The shapes of landmasses force ships into narrow paths in the Indian Ocean, while ships in the Atlantic and Pacific tend to spread out over a broad areas as they navigate around storms.

In addition, the air over the northeastern Indian Ocean is relatively pristine.
Heavy NO2 pollution (dark red in the map) from cities and off-shore drilling activity along the coasts of China, Europe, and the United States obscures the ship tracks that might otherwise be visible to OMI.
In the map, the Arctic is gray because the lack of light during the winter and frequent cloudiness during the summer prevented OMI from collecting usable data in the area.

Urban areas and industrialization aren’t the only source of NO2 in the map. Agricultural burning in southern Africa and persistent westerly winds make an elevated band of NO2 that stretches from southern Africa to Australia.
(In central Africa, easterly winds push pollutants from fires toward the Atlantic, keeping NO2 levels comparatively low over the northern Indian Ocean.)
Lightning, which produces NOx, also contributes to background NO2 levels.

Just how much shipping contributes to overall NOx emissions remains an open question for scientists.
Research suggests that shipping accounts for 15 to 30 percent of global NOx emissions; scientists are using satellite observations to reduce the uncertainty in such estimates.

OMI is not the only satellite instrument observing NO2 levels in the atmosphere. The Global Ozone Monitoring Experiment (GOME) instruments on the European Space Agency’s ERS-2 and MetOp-A satellites, as well as the SCIAMACHY instrument on the Envisat satellite, have made similar measurements.
In 2012, Dutch scientists published a study combining data from all four instruments to show that the NO2 signal over major shipping increased steadily between 2003 and 2008, then dropped sharply due to the global recession and reduction in ship traffic.

Magnetic memories may guide salmon home

Map: Oregon State University/NSF

From Wired

After years at sea, sockeye salmon returning to their freshwater homes may be guided by an early memory of the Earth’s magnetic field, encoded at the site where natal streams empty into the Pacific Ocean, according to a study published today in Current Biology.

“Lots of folks have been wondering for decades how salmon and other animals, like sea turtles or seals and whales, go out in the ocean for a couple of years and then return with remarkable accuracy back to their home,” said study coauthor Nathan Putman, a marine biologist at Oregon State University.
“The magnetic field is an important part of the [salmon's] migratory decision."

Photo: Current Biology, Putman et al

To study salmon navigation, Putman and his colleagues took advantage of a serendipitous natural experiment.
Near the mouth of British Columbia’s Fraser River is 460-kilometer-long Vancouver Island. Salmon returning from sea and aiming for the river face a choice: swim north around the island, or go around to the south.
Putman pored over 56 years of data from federal fishery scientists who tracked salmon in both waterways, then matched that up with measurements of the Earth’s geomagnetic field, which shifts predictably in strength and orientation over time.
He found that fish tended to choose the path where the field strength was more similar to that of the river mouth when they’d left, two years before.

“The magnetic field at each route predicts the proportion coming in,” Putman said.
He speculates that reaching saltwater triggers the fish to remember the magnetic field at the river’s mouth when they first head to sea — and then seek that same field on the return journey.

Scientists hope the finding will help solve the mystery of how salmon find their way home from thousands of miles away, across an ocean with no lanes or landmarks. It’s already accepted that in the final stages of the journey to their breeding grounds, salmon use odors to guide them back to the stream or inlet where they hatched.
But how the fish find their target river is still a mystery, although scientists have suspected for a while that magnetic cues play a role.
Last summer, a team reported that rotating magnetite crystals in a fish nose responded to magnetic field orientation, providing a possible biological mechanism for this sensory capability.

 Sockeye Salmon from Fraser River in British Columbia typically spend two to four years at sea, feeding on zooplankton.

Credit: Current Biology, Putman et al.

“In general, we know much less about how salmon complete the ocean part of their migration compared to fresh water,” said quantitative ecologist Chloe Bracis, a graduate student at the University of Washington who also studies geomagnetic salmon navigation.
“The authors cleverly take advantage of spatial differences in a salmon migration route to provide the first solid evidence that salmon use geomagnetic cues to direct their oceanic migration.”

Putman now hopes to investigate this correlation in experiments with captive fish subjected to artificial magnetic fields.

But even if those experiments bolster the case that salmon use geomagnetic cues, these cues can’t be the whole story.
The new study also revealed that sea surface temperature is an important guide for the fish — but even the interaction of water temperature and magnetic cues can’t explain all of the fishes’ knack for navigation.
Temperature, olfaction and magnetoreception, while clearly important, may be just some of the tools salmon use to find their way home.
“They might use … a sun compass or other cues,” Bracis said.
“Geomagnetic cues could guide them to the vicinity of the river, then they would need to switch to other local cues to navigate the rest of the way to the river mouth or through the estuary.”

Links :

• NationalGeographic : Mystery solved: salmon navigate using magnetic field 
• GeoGarage blog : Turtles use the Earth’s magnetic field as a global GPS / Some sharks use mental maps to navigate; others do not

Is it love? Why some ocean animals (sort of) mate for life

Two waved albatrosses, the only tropical albatross species, courting one another on the Galapagos Islands.
Photo by Flickr User James Preston

From Smithsonian

We often hear stories of animal love—tales of rare monogamy in the animal kingdom where life-long love is implied. But there is a distinction between romantic love and an efficient mating system. Here’s a look at some ocean animals to see what is really going on.

Albatrosses Get ‘Romantic’ to Increase Chick Survival

Albatross relationships seem especially relatable to humans.
These long-lived and highly-endangered birds will court each other through ritual dances for years. Albatrosses are slow to reach sexual maturity, and some species even delay breeding for several years to learn specific mating rituals and to pick the perfect partner.
The courtship behavior slows down once the pair bonds (an all too familiar aspect of human relationships).
Once a pair is comfortable and breeding commences, they will return to each other and the same spot each year; for most albatross species, the bond lasts their entire life.

So is it love?
The biological reality is that albatrosses only lay a single egg a year.
With both parents fully invested in chick survival, their genetic heritage is most likely to survive.
It may seem like love, but with those low reproduction rates no parents can afford to be deadbeats.

A waved albatross looks after its chick on the Galapagos Islands.
Photo by Flickr user James Preston

Seahorses Bond to Improve the Odds of Birth

If albatross relationships are reminiscent of fairytale romance, seahorses might be considered the swingers of the sea.
Many seahorse species will bond with a mate, but that bond often lasts only through a single breeding season or until a more attractive female comes along.
But, monogamy in this case is useful since it can be hard to find fellow seahorses due to poor swimming skills and low densities.

There is evidence that the longer that partners are together, the more successful at breeding they become and the two are able to produce more offspring per brood.
One species of seahorse does appear to stick with a single mate for life: the Australian Hippocampus whitei.
Practice makes perfect!

Two thorny seahorses (Hippocampus histrix), tails intertwined.
Photo by Bettina Balnis/Guylian Seahorses of the World 2010, Courtesy Project Seahorse

Two Angelfish Make a Strong Defense

Typically in pairs, French angelfish (Pomacanthus paru) help each other defend their territory against other fish.
The couples have been observed spending extended periods of time together, exhibiting more of a monogamous social structure.
Genetic monogamy (i.e. testing fertilized eggs to confirm they come from a single father) hasn’t been confirmed, but there have been observations of pairs traveling to the water’s surface to release their eggs and sperm together.
Monogamy is not that common in fishes, and it is mostly found in tropical and subtropical waters. Care needed from two parents, joint defense of territories, and difficulties in finding a mate all can play a role.

A pair of French angelfish off the coast of Brazil.
Photo by Barry Peters

A Permanent Glass Home for Shrimp

These intriguing glass sponges, called Venus’s flower-baskets (Eupectella aspergillum), are made of flexible silica that can better transmit light than our man-made fiber-optic cables.
And many of these beautiful deep-sea sponges are also home to a monogamous pair of shrimp.

Several species of shrimp find refuge in these sponges, but due to the limited space found within the fine-mesh silica, only two adult shrimp can fit inside—and they are stuck there for life.
The two spend their days cleaning the sponge and eating whatever bits of food manage to flow through.
After they breed, their small offspring can squeeze through the holes in the mesh to escape, but eventually they will settle into a new home with their own imprisoned mate.

The silica home of a male and female shrimp – the deep-sea sponge Venus’s flower-basket.
Photo via NOAA

The gift of this sponge, taken from the deep with the two dead shrimp still trapped inside, is considered good luck for couples marrying in Japan.
It seems as though young human couples are not the only ones to share tight living spaces.