Saturday, March 7, 2020

Image of the week : cloud streets over the Labrador Sea

NASA Earth Observatory image by Joshua Stevens, using VIIRS data from NASA EOSDIS/LANCE and GIBS/Worldview and the Suomi National Polar-orbiting Partnership.

From NASA by Adam Voiland

As sea ice in far northern latitudes approached its annual maximum extent, the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite acquired this false-color image of the Labrador Sea on March 2, 2020.
Chunks of sea ice hugged the coast of Baffin Island, while cloud streets streamed over the sea.

With this combination of visible and infrared light (bands M11-I2-I1), snow and ice appear light blue, and clouds are white.
The orientation of the cloud streets indicate that strong, cold winds were blowing from north to south.
As the cold air moved over the comparatively warm ocean water, the air warmed and picked up the moisture needed to form cumulus clouds.

On March 2, 2020, GOES-16 (GOES-East) spotted ribbon-shaped cloud streets streaming over the Labrador Sea from the sea ice edge in the Davis Strait.
As frigid air moves over relatively warmer water, the warmer air rises, bringing moisture with it.
As it cools, it gradually condenses and sinks in rows of horizontal counterclockwise-rotating air cylinders that line up with the prevailing direction of the wind.
As that wind sweeps around the southern tip of Greenland, the clouds are blown in a new direction, losing their “streamer” shape.
The Advanced Baseline Imager (ABI) on NOAA’s GOES-16 (GOES-East) geostationary satellite also acquired imagery of the cloud streets on March 2, 2020. 
Imagery credit: CIRA/NOAA

Cloud streets form when columns of heated air—thermals—rise through the atmosphere and carry heat away from the sea surface.
The moist air rises until it hits a warmer air layer (a temperature inversion) that acts like a lid.
The inversion causes the rising thermals to roll over on themselves, forming parallel cylinders of rotating air.
On the upward side of the cylinders (rising air), water vapor condenses and forms clouds. Along the downward side (descending air), skies remain clear.
Arctic ice normally reaches its annual maximum extent in mid or late March.
Sea ice extent this winter has been below average, according to tracking charts published by the National Snow & Ice Data Center.

Friday, March 6, 2020

Microbes point the way to shipwrecks

Marine organisms colonizing the bow of a yacht called Anona, which sank in the Gulf of Mexico in 1944.
Credit : Deep Sea Systems International's Global Explorer ROV and the Bureau of Ocean Energy Management.

From NYTimes by Katherine Kornei

Distinct microbiomes flourish around sunken ships as they become artificial reefs, new research in the Gulf of Mexico reveals.

Off the coast of Mississippi, under 4,000 feet of water, a luxury yacht is slowly disintegrating.
Marine creatures dart, cling and scuttle near the hull of the wreck, which has been lying undisturbed for 75 years.

But there’s more than meets the eye when it comes to this shipwreck and others, researchers have now shown — distinct assemblages of microbes inhabit the seafloor surrounding these structures, helping to turn shipwreck sites into artificial reefs rich in life.

Shipwrecks are trespassers on the bottom of the ocean, human-made structures decidedly out of their element.
But a wreck’s intrusion gradually becomes welcome as various forms of marine life seek refuge among the steel and wood.

The macroscopic animals that inhabit shipwrecks are only there thanks to much smaller forms of life, said Leila Hamdan, a marine microbial ecologist at the University of Southern Mississippi.

That’s because microbes like bacteria and archaea coat surfaces in a sticky layer, a biofilm, that functions as a chemical and physical come-hither call for larger creatures such as barnacles and coral, Dr. Hamdan said.
“A shipwreck can never become an artificial reef unless the microorganisms are there first.”

Her team is researching how the presence of a shipwreck affects microbial communities.
This field of research, shipwreck microbial ecology, is a niche area of study that spans archaeology, biology, ecology and marine science, she said.
“As far as we know, we’re the only ones doing it right now.”

In September 2018, Dr. Hamdan and her colleagues departed from Gulfport, Miss., aboard the research vessel Point Sur.
Roughly 70 miles off the coast, the team lowered a remotely operated vehicle called Odysseus into the 80-degree water.
Within 45 minutes, Odysseus’ seven thrusters had propelled it to the seafloor.
There, it began emitting sonar pings to locate Anona, a shipwreck first discovered in the 1990s that the team knew was nearby.

Built for a Detroit industrialist in 1904, Anona was a 117-foot long yacht, with a steel hull.
A research team has been exploring the microbes and organisms that now inhabit Anona’s remains on the seafloor, where the shipwreck was discovered in the 1990s.
Credit...Bowling Green State University

The 117-foot yacht, built in the early 20th century for a Detroit industrialist, was once sumptuously appointed in mahogany and teak, with a social hall that featured a piano.
It sank in 1944, when the steel plates beneath its engines buckled during a voyage to the British West Indies.
(The structural failure sent the crew of nine scrambling into a raft, and they drifted for two days before being rescued.) Anona fell to the seafloor upright and intact, its bow pointing toward Cuba.

Dr. Hamdan and her colleagues directed Odysseus around the shipwreck.
The remotely operated vehicle, about the size of a small car, carried a payload of clear plastic tubes.
At predetermined distances from the shipwreck — ranging from about 300 to seven feet — one of the vehicle’s robotic arms plunged a tube the size of a water bottle into the fine gray sediment of the seafloor.
The team collected cores off the yacht’s bow, starboard side and port side.
(On previous research cruises, the team had collected cores as far away as 3,300 feet, including ones off Anona’s stern.)

In June and July of last year, the team conducted similar fieldwork at two other shipwreck sites that they discovered in the Gulf of Mexico.
Based on the shapes of the wooden sailing vessels and the artifacts found nearby, the ships were most likely built in the 19th century.
Like Anona, both vessels were upright and intact.
One rested in relatively shallow water, about 1,700 feet, and the other lay beneath more than 5,900 feet of water.

Back in the laboratory, the team extracted microbial DNA from the cores and sequenced the genetic material.
“We look both at who is present and what their abundance is,” Dr. Hamdan said.

The researchers found the largest diversity of microbes — several hundred types — roughly 160 to 330 feet away from Anona.
That makes sense based on the age of the shipwreck, Dr.
Hamdan said, since the structure is providing resources to microbes.
“Those resources begin to spread over time, and with the resource follows the microbes.”

The team also discovered that the seafloor’s microbiome varied with distance from Anona.
That’s something that had not been demonstrated before, Dr.
Hamdan said.
“A shipwreck sitting on the deep ocean floor is materially changing the biodiversity of the seabed.”

An anchor and some ceramic dishes were among the artifacts near the hull of a shipwreck.
Credit...Pelagic Research Service’s Odysseus ROV and the National Oceanic and Atmospheric Administration.

Near the wooden sailing vessels, the scientists found bacteria that degrade cellulose and hemicellulose, some of the primary components of wood.
“That gives us an idea that maybe they’re feeding on the shipwreck,” said Justyna Hampel, a biogeochemist at the University of Southern Mississippi who led the analysis of the two new shipwreck sites.

Because there is no light and only limited sources of energy in deep water, survival “defies the normal routes of life,” Dr. Hampel said.

The microbiomes of the two newly discovered shipwrecks are also distinct from each other, the team showed, which raises the question of whether water depth plays a role in dictating microbial communities.

It’s unknown whether these microbes were transported to the seafloor or they were there all along and conditions simply became conducive to their flourishing after a ship sank.
“That’s the million-dollar question in microbial ecology,” Dr. Hamdan said.

In support of the second idea, there’s a theory that “everything is everywhere, but the environment selects,” she added.
As an example, it’s entirely possible that an individual spore of bubonic plague is sitting on my desk right now, she said.
“It’s just there, waiting for the right conditions.” Similarly, shipwrecks create a new environment that is hospitable to some microbes but inhospitable to others, she said.

Dr. Hamdan’s students are doing experiments on the seafloor to investigate where the microbes came from, and where they go when they leave shipwrecks.

These results were presented this week at the Ocean Sciences Meeting in San Diego.

Magnificent ecosystems exist around shipwrecks, said Andrew Davies, a marine biologist at the University of Rhode Island who was not involved in the research.
But it’s been largely unknown how these artificial structures affect the surrounding seafloor, he said, so it’s good to see studies like this that are focused on “habitats of opportunity.”

In the future, Dr. Hamdan and her colleagues plan to study microbial communities around other shipwrecks.
There are plenty of possibilities — more than 2,000 shipwrecks in the Gulf of Mexico, she said.
“We absolutely need to go to more sites.”

Thursday, March 5, 2020

Norway (NHS) layer update in the GeoGarage platform

110 nautical raster charts updated

The world may lose half its sandy beaches by 2100. It’s not too late to save most of them

From The Conversation by John Church

For many coastal regions, sea-level rise is a looming crisis threatening our coastal society, livelihoods and coastal ecosystems.
A new study, published in Nature Climate Change, has reported the world will lose almost half of its valuable sandy beaches by 2100 as the ocean moves landward with rising sea levels.

Sandy beaches comprise about a third of the world’s coastline.
And Australia, with nearly 12,000 kilometres at risk, could be hit hard.

This is the first truly global study to attempt to quantify beach erosion.
The results for the highest greenhouse gas emission scenario are alarming, but reducing emissions leads to lower rates of coastal erosion.

Our best hope for the future of the world’s coastlines and for Australia’s iconic beaches is to keep global warming as low as possible by urgently reducing greenhouse gas emissions.
Losing sand in coastal erosion

Two of the largest problems resulting from rising sea levels are coastal erosion and an already-observed increase in the frequency of coastal flooding events.

Erosion during storms can have dramatic consequences, particularly for coastal infrastructure.
We saw this in 2016, when wild storms removed sand from beaches and damaged houses in Sydney.

A swimming pool washed away from a beachside property after wild storms in Sydney in 2016.
AAP Image/David Moir

After storms like this, beaches often gradually recover, because sand from deeper waters washes back to the shore over months to years, and in some cases, decades.
These dramatic storms and the long-term sand supply make it difficult to identify any beach movement in the recent past from sea-level rise.

What we do know is that the rate of sea-level rise has accelerated.
It has increased by half since 1993, and is continuing to accelerate from ongoing greenhouse gas emissions.

If we continue to emit high levels of greenhouse gases, this acceleration will continue through the 21st century and beyond.
As a result, the supply of sand may not keep pace with rapidly rising sea levels.

Projections for the worst-case scenario

In the most recent Intergovernmental Panel on Climate Change (IPCC) report, released last year, the highest greenhouse gas emissions scenario resulted in global warming of more than 4°C (relative to pre-industrial temperatures) and a likely range of sea-level rise between 0.6 and 1.1 metres by 2100.

For this scenario, this new study projects a global average landward movement of the coastline in the range of 40 to 250 metres if there were no physical limits to shoreline movement, such as those imposed by sea walls or other coastal infrastructure.

Sea-level rise is responsible for the vast majority of this beach loss, with faster loss during the latter decades of the 21st century when the rate of rise is larger.
And sea levels will continue to rise for centuries, so beach erosion would continue well after 2100.

For southern Australia, the landward movement of the shoreline is projected to be more than 100 metres.
This would damage many of Australia’s iconic tourist beaches such as Bondi, Manly and the Gold Coast.
The movement in northern Australia is projected to be even larger, but more uncertain because of ongoing historical shoreline trends.

What happens if we mitigate our emissions

The above results are from a worst-case scenario.
If greenhouse gas emissions were reduced such that the 2100 global temperature rose by about 2.5°C, instead of more than 4°C, then we’d reduce beach erosion by about a third of what’s projected in this worst-case scenario.

Current global policies would result in about 3°C of global warming.
That’s between the 4°C and the 2.5°C scenarios considered in this beach erosion study, implying our current policies will lead to significant beach erosion, including in Australia.

Mitigating our emissions even further, to achieve the Paris goal of keeping temperature rise to well below 2°C, would be a major step in reducing beach loss.

Why coastal erosion is hard to predict

Projecting sea-level rise and resulting beach erosion are particularly difficult, as both depend on many factors.

For sea level, the major problems are estimating the contribution of melting Antarctic ice flowing into the ocean, how sea level will change on a regional scale, and the amount of global warming.

The beach erosion calculated in this new study depends on several new databases.
The databases of recent shoreline movement used to project ongoing natural factors might already be influenced by rising sea levels, possibly leading to an overestimate in the final calculations.

The implications

Regardless of the exact numbers reported in this study, it’s clear we will have to adapt to the beach erosion we can no longer prevent, if we are to continue enjoying our beaches.

This means we need appropriate planning, such as beach nourishment (adding sand to beaches to combat erosion) and other soft and hard engineering solutions.
In some cases, we’ll even need to retreat from the coast to allow the beach to migrate landward.

And if we are to continue to enjoy our sandy beaches into the future, we cannot allow ongoing and increasing greenhouse gas emissions.
The world needs urgent, significant and sustained global mitigation of greenhouse gas emissions.

Links :

Wednesday, March 4, 2020

How 'dark fishing' sails below the radar to plunder the oceans

It is estimated one in five fish brought to markets is illegally caught, often by a so-called “dark” fishing fleet.
This refers to vessels that switch off their satellite tracking to hide their activities in far-flung parts of the world’s oceans.
Now a Greenpeace investigation has uncovered the scale of the problem and the need for greater ocean protection.

From Al'Jazeera by Nick Clark

Billions of dollars in illegal and unregulated fish supplies are mixed with legal catches and smuggled into the market.

In September last year, the Greenpeace campaign ship Arctic Sunrise was scanning the mid-Atlantic ocean, thousands of kilometres from anywhere.
On board, investigators were looking for vessels that were doing their best not to be found.

One of them was Taiwanese fishing boat, the Hung Hwa - a longliner capable of running baited lines more than 100 kilometres (62 miles) in length, targeting mainly tuna species.
It had turned off its satellite locator, the Automatic Identification System (AIS).

It had "gone dark".

A fishing vessel might do that to avoid competition from other boats or to prevent attack by pirates.
But often it coincides with a transhipment at sea - the offloading of a fishing boat's catch onto what is known as a reefer, or a giant refrigerated cargo ship.
The transhipment loophole

Transhipping is the lifeblood of the distant water fishing industry.
It allows fishing boats to stay at sea without returning to port for months because they can offload their catch on to what are effectively colossal floating freezers.

As part of the process, the fishing vessels are refuelled and resupplied by the reefers, allowing them to get straight back to doing what they do - catching fish relentlessly.

The problem is that transhipping fish mid-ocean presents a major loophole in monitoring fishing activities.

By offloading at sea, vessels are able to smuggle illegal, unreported and unregulated (IUU) catches into the market by mixing them with legal catches.

This makes it exceedingly difficult to detect fraud or trace a shipment back to the vessel that caught it.
It also allows entire fleets to operate out of sight, where they can hide illegal catches and operate without returning to port.

Under the radar

On the bridge of the Arctic Sunrise, the Greenpeace investigators were scrutinising the navigation screens, following the satellite tracks of vessels in their sector of the ocean.
Their suspicions were raised when a Taiwan-owned, Panama-registered reefer vessel called the Hsiang Hao, appeared to be sailing slowly in a loitering pattern - effectively circling for several hours.

There was no other vessel present, at least none displaying AIS.

But the next day the Arctic Sunrise intercepted the Hsiang Hao and there, alongside, was the Hung Hwa, still "dark" - not transmitting its satellite location.

And from the Hung Hwa's hold, dozens upon dozens of deep-frozen tuna and shark - frosted and steaming in the humid equatorial air - were being hoisted on to the reefer ship.

Greenpeace’s lead investigator, Sophie Cooke, said there are many reasons vessels may not want to appear on satellite.

"Some of them might be legitimate," she said.
"But a lot of the time, it's because they want to avoid detection or want to go into areas they are not allowed.
Or they want to meet up with another vessel at sea and do not want to be seen."

"If ships turn off their satellite tracking it means no one sees what's happening out at sea and it makes the high seas a black hole of fishing activity," Cooke added.

Second mate Helena De Carlos Watts and lead investigator, Sophie Cooke, right, watch the radar screen as the Arctic Sunrise approaches a target vessel in the southern Atlantic ocean [Tommy Trenchard/Greenpeace]

The Investigation

In 2017, Greenpeace set out to understand the scale and misuse of AIS by the global reefer industry.
They investigated the movements, behaviour and owner structures of more than 400 reefers identified as being capable of taking part in transhipments at sea.

In the resulting report just published, the investigating team said what was most striking was how much transhipment is happening between fishing vessels that have gone dark because of their involvement in illegal fishing.

"It’s very hard to know the exact amount of IUU fishing activity that’s going on," said Will McCallum, Greenpeace's head of oceans, "but what we do know is that transhipment allows vessels to stay far out at sea where they are out of scrutiny, out of mind and out of sight."

McCallum said they can track exactly where the global fleet of refrigerated cargo vessels is operating.

"For example, we can see they're in the southwest Atlantic, which is a part of the world where there is very little, to the point of almost no fisheries management for a lot of fishing vessels," he said.

'Flags of convenience'

The Greenpeace report highlights how the global fleet of reefers hides behind complex ownership structures and "flags of convenience" that reduce accountability and transparency.

The single most active fleet of reefers involved in transhipments on the high seas is owned by the Greek shipping magnate Thanasis Laskaridis, whose vessels ply the seas the world over, from the North Atlantic to the South Pacific.

Investigators also discovered that because transhipment allows fishing boats to spend months or even years at sea without returning to port, it leaves crews open to abuse.
Being so far from scrutiny and the prying eyes of port inspectors for so long raises the possibility that boat owners can effectively enslave their crew.

Many cases have been documented, the report said, of fishermen being forced to work exhausting shifts in unsafe conditions, having their pay withheld and documents confiscated.
There are even reports of crew being denied access to clean food and drinking water.

The Arctic Sunrise [Tommy Trenchard/Greenpeace] 

Closing gaps in ocean governance

McCallum said the investigation demonstrates the urgent need for greater scrutiny.

"Reefers should have observers on board to track where the catch is coming from and make sure we are not muddying the global supply chains." The ultimate goal would be for transhipment at sea to be phased out.

There is no question of the severity of the grave assault that is taking place on our oceans and everything that lives in it.
Overfishing is wreaking havoc on marine life while threatening the food security and livelihoods of billions of people.

This year will be a significant one for the world - from the crucial climate conference in Glasgow in November to a landmark biodiversity summit in October in China.
But, for the Greenpeace oceans team, all eyes right now are on New York in March when maximum effort is being focused on the implementation of a global ocean treaty at a vital UN conference.

"We need a strong ocean treaty," said McCallum.
"We need a single holistic way to manage these international waters, that are so far from land they’re very hard for a single country or group of countries to monitor and regulate.
So a global ocean treaty would plug some of the governance gaps that we are seeing at the moment."

The goal is to ensure 30 percent of the world’s oceans become off-limits to any kind of exploitation - from fishing to deep-sea mining.
And that way those far-flung waters that are often home to pristine ecosystems, would be better protected from the fleet that goes dark to pursue and dispatch its catch.

Links :

Tuesday, March 3, 2020

Introducing Tidal : Fishial recognition tech

 Google’s parent company Alphabet has today launched a new initiative called Tidal aimed at changing that, with an overarching objective to use a better understanding of the ocean to better protect the marine environment.
A moonshot to protect the ocean and feed humanity sustainably

From Blog X by Neil Davé

One of the biggest barriers to protecting the ocean — and our future — is that we don’t know much about what’s going on under the water.
Even though it covers around 70% of the planet, most of it remains unexplored.
We know more about the surface of the moon than we do about the deepest parts of the ocean floor.
This is partially because it’s an incredibly challenging environment for technology.
The pressure is crushing, communication is extremely difficult (GPS and WiFi don’t work underwater!), and saltwater kills electronics, which makes long-term monitoring challenging.

This is a critical issue: humanity is pushing the ocean past its breaking point, but we can’t protect what we don’t understand.
Pollution and unsustainable fishing practices mean that there will soon be more plastic than fish in the sea, while rapid acidification is killing corals and sea creatures.
This is driving upheaval in ecosystems all over the world, from coral reefs to the Arctic, leading to chain reactions of damage that are threatening human food and economic security.

That’s why today we’re announcing Tidal: a team at X working on a moonshot to protect the ocean and preserve its ability to support life and help feed humanity, sustainably.
Our initial area of focus is on developing technologies that bring greater visibility and understanding of what’s happening under the water.

We decided to start working on a small corner of this problem: exploring new tools that could provide useful information to fish farmers looking for environmentally friendly ways to run and grow their operations.
Fish have a low carbon footprint relative to other sources of animal protein and they play a critical role in feeding 3 billion people today, so helping fish farmers could prove critical both for humanity and for the health of the ocean.

Getting our feet wet

Over the last three years we’ve consulted with fish farmers around the globe and learned how eager they are to minimize food waste, catch diseases earlier, and reduce their use of chemicals.
Today, the health and welfare decisions for thousands of fish are based on observing a few individual fish that are taken out of the water and manually inspected — a data-gathering process that’s time-consuming, unreliable and impossible to scale.
We thought we could help.

Research and development north of the Arctic Circle
The idea is that observing the fish and their behaviors in this kind of unprecedented detail, can help farmers manage their pens in more efficient ways, through the smarter use of fish food, for example. 

After spending lots of time out on the water, we’ve developed an underwater camera system and a set of machine perception tools that can detect and interpret fish behaviors not visible to the human eye.
Our software can track and monitor thousands of individual fish over time, observe and log fish behaviors like eating, and collect environmental information like temperature and oxygen levels.
This kind of information gives farmers the ability to track the health of their fish and make smarter decisions about how to manage the pens — like how much food to put in the pens, which we hope can help reduce both costs and pollution.

Fish farming as a diving off point

Earth is a unique planet — because it’s the blue planet.
We must work harder to protect it, and that’s what motivates the Tidal team.
The ocean provides food and livelihoods for billions of people as well as every second breath we take.
A natural carbon sink, it’s the planet’s air filter, temperature regulator and food basket rolled into one.

While we started developing our technology with fish farmers, this is just one area in which we hope to help.
As we validate our technology and learn more about the ocean environment, we plan to apply what we’ve learned to other fields and problems, with the help of ocean health experts and other organizations eager to find new solutions to protect and preserve this precious resource.
If Tidal’s mission sounds like something you’d like to be part of, please get in touch.

Links :

Monday, March 2, 2020

The divers rescuing a drowning island

Vaan Island in India’s Gulf of Mannar

From BBC by Kamala Thiagarajan

Vaan Island in India’s Gulf of Mannar has been rapidly disappearing into the Laccadive Sea.
But a team of marine biologists is working to save it.

Hundreds of fishing boats bob on the bright blue waters surrounding Vaan Island, a tiny strip of land between India and Sri Lanka.
The island marks the beginning of a fiercely protected fragile zone, the Gulf of Mannar Biosphere Reserve.
These waters are home to India’s most varied and biodiverse coastlines.
Teeming with marine life, it is home to 23% of India’s 2,200 fin fish species, 106 species of crab and more than 400 species of molluscs, as well as the Indo-Pacific bottlenose dolphin, the finless porpoise and the humpback whale.

 Vaan Island in India’s Gulf of Mannar (NGA nautical chart) with the GeoGarage platform

Nearly 150,000 fishermen depend on the marine reserve for their livelihoods.
And Vaan Island is the gateway to this world.
Half an hour by boat from the mainland and easily accessible to the 47 villages that are the backbone of this heavily populated coastline, Vaan has always been a refuge from storms for fishermen and a hotspot for researchers.
But for the past 50 years it has been rapidly shrinking.

Hundreds of fishing boats bob on the bright blue waters surrounding Vaan Island, a tiny strip of land between India and Sri Lanka.
The island marks the beginning of a fiercely protected fragile zone, the Gulf of Mannar Biosphere Reserve.
These waters are home to India’s most varied and biodiverse coastlines.
Teeming with marine life, it is home to 23% of India’s 2,200 fin fish species, 106 species of crab and more than 400 species of molluscs, as well as the Indo-Pacific bottlenose dolphin, the finless porpoise and the humpback whale.

Nearly 150,000 fishermen depend on the marine reserve for their livelihoods.
And Vaan Island is the gateway to this world.
Half an hour by boat from the mainland and easily accessible to the 47 villages that are the backbone of this heavily populated coastline, Vaan has always been a refuge from storms for fishermen and a hotspot for researchers.
But for the past 50 years it has been rapidly shrinking.

In 1986, 21 such islands in this region were protected when the Gulf of Mannar Biosphere Reserve, the first of its kind in Asia, was established in the Laccadive Sea.
Now there are only 19.
Two have been submerged and Vaan Island is the next at risk of vanishing.
In 1973, Vaan was 26.5 hectares (65 acres), shrinking to just 4.1 hectares (10 acres) in 2016.
At that point the erosion was so extreme that researchers estimated that it would be entirely underwater by 2022.

Fishing is a crucial source of income in the coastal towns and villages of Tamil Nadu state in southern India
(Credit: Getty Images)

The reason that small, ecologically rich islands like Vaan are vanishing is a combination of unsustainable fishing practices, rising sea levels due to climate change and historic coral mining, which has now been banned in the area.
Artificial reefs were deployed to help buffer waves reaching the islands, and they were effective.
But to give Vaan and its neighbours a longer-term future, the ecosystem as a whole needed replenishing.

Gilbert Mathews, a marine biologist at the Suganthi Devadason Marine Research Institute (SDMRI) in the nearby coastal town of Thuthukudi in southern India, turned to seagrass, a plain and innocuous-looking type of marine plant, as a way to save the island ecosystem.
Often mistaken for seaweed, seagrasses are plants that grow underwater and have well-defined roots, stems and leaves.
They produce flowers, fruits and seeds, and play a vital role in maintaining a marine ecosystem.

“Like corals, these tufts of grass provide a habitat to many splendorous sea-creatures, such as seahorses and lizard fish, which can be found in seagrass throughout the year,” says Mathews.
Seagrass provides the right environment for young fish and invertebrates to conceal themselves, while absorbing dissolved carbon dioxide and creating an oxygen and nutrient-rich environment.
With its ability to trap sediments, seagrass also acts as a natural filter, clearing the waters and slowing erosion.

Mathews first surveyed the seagrass around Vaan Island in 2008, diving into the shallow waters twice a month, for up to eight hours a day.
With a sense of dismay, he saw many tufts of seagrass floating in the water around him.
These islands were home to the most luxuriant seagrass meadows of the Indian sub-continent, but they were coming loose.

When researchers first investigated the seabed around Vaan Island, they found its sea meadows to be in a poor state
(Credit: SDMRI)

The sprigs had been pulled out by fisherman operating trawler boats, who rig two or more nets to scour the shallow waters.
Fishing along shallow waters and the disruption of seagrass beds is illegal in India, but because of poor monitoring, the law is not strictly enforced.
Along with trawlers’ haul of crustaceans and fish, they would pull out hundreds of green sprigs of seagrass that were later discarded in heaps along the shore.
By destroying the seagrass, the trawlermen were inadvertently destabilising the ecosystem on which they relied – without seagrass as the base of the ecosystem, fish stocks dwindled.

In studies between 2011 and 2016, Mathews found that 45 sq km (17 sq miles) of seagrass cover had been degraded in the Palk Bay, where the waters of the Indian Ocean meet the Bay of Bengal.
In the Gulf of Mannar, 24 sq km (9 sq miles) had died.
“We believed that by restoring the seagrass meadows along these waters, we could strengthen the island and possibly save this and prevent others from submerging into the sea,” he says.

Mathews knew that restoring seagrass would be a challenge.
A global assessment of 215 studies, led by marine biologist Michelle Waycott of the University of Adelaide, Australia, found that seagrass had been rapidly disappearing all over the globe.
Meadows spread over an area of 110 sq km (42 sq miles) – equivalent to an area the size of the Indian city of Chandigarh – have been vanishing every year since 1980.
Overall, 29% of seagrass has been lost since records began in 1879.

The seagrass around Vaan Island was patchy and brown before the transplants took place
(Credit: SDMRI)

But if the seagrass meadows could be reinvigorated around Vaan Island, they could also act as a carbon sink.
“Plantation and restoration provide a growing solution towards mitigating climate change and affording some protection in this very fragile part of the world, which is often shaken by hurricanes and strong winds,” says Edward J.K.
Patterson, director of the SDMRI.

At first, the researchers tried pulling up tufts directly from the sandy bottom of the seabed, and moving them to sites that had been badly depleted.
But it didn’t work – the trawlers still pulled them out, undoing their painstaking work.
It became evident that the team needed to find another way, but most of the usual rehabilitation techniques used in other parts of the world were expensive, even more labour-intensive and therefore not viable.
For instance, one well-known method was the dispersal and sowing of seagrass seeds.
But this wasn’t practical: the beds had to be dug out underwater and each seed planted by hand.

Mathews and his colleagues spent the next eight years trying to work out a better way to save the seagrass.
Meanwhile, the erosion continued and in 2013 Vaan Island split in two as the sea encroached.
In 2016, the Gulf of Mannar experienced its worst ever coral bleaching episode, losing 16% of its coral cover.
Restoring corals and seagrass were twin projects, as both corals and seagrass act as natural barriers, affording some protection from strong waves and reducing erosion.

The marine biologists brought hefty sacks of fresh seagrass to the surface for transplantation to weaker spots
(Credit: SDMRI)

Scientists from the SDMRI had by then perfected a better transplantation technique for restoring seagrass.
Mahalakshmi Bupathy, a researcher specialising in soft corals, joined the team in 2016 along with her “diving buddy”, coral sponge scholar Arathy Ashok, to try out this new method.

Several times a month, Bupathy and Ashok’s day began at 5am with a dive down to the seabed.
First, they surveyed the sites along the 19 remaining islands of the Gulf of Mannar and the Palk Straight and noted which underwater areas needed more seagrass and which harboured luxuriant growth.
The latter could be promising “donors” to replenish the weaker sites.
They also took stock of the area’s biodiversity, recording the vegetation and the fish population.
Where there was plenty of seagrass, the ocean life was surprisingly rich.
“I found giant barrel sponges that had been last sighted in these waters 30 years ago,” says Ashok.
“These are such enigmatic creatures.”

Next, the pair collected mature seagrass sprigs from chosen donor sites.
“One had to be particularly careful while digging them out,” says Bupathy.
The sprigs have two kinds of roots – one set that grew vertically and other horizontally, which needed to be teased out without damaging them.

Before dropping the sprigs into the bags, Bupathy and Ashok washed them thoroughly in seawater to clear away any sediment.
The initial unsuccessful attempts had revealed that replanting with excessive sediment blocked the sunlight and prevented photosynthesis, stunting the sprigs’ growth.
The team then put the bags on the boats where the other team members were waiting with containers filled with seawater.
Immersed in these containers, the seagrass then had to be transported to the transplant sites within an hour, or the sprigs would die.

The scientists had a short window to sort the delicate seagrass before transplanting it to its new home (Credit: SDMRI)

When they reached their target – barren areas of former meadows – the shoots were then tied to a 1 sq m (11 sq ft) plastic quadrat using jute twine.
A total of six pieces of twine could bind nearly 120 shoots to the squares.
The roots had to be left intact, so that they could embed in the soil when the transplant took place.
Depending on weather conditions, the team fixed up to 80 quadrats a day, each bound with the shoots that might, if they were lucky, hold Vaan Island together.

“It took two to three months for the roots to bind to the sandy and muddy underwater terrain,” says Ashok.
Once it had, they would dive back to retrieve the plastic quadrats.

They monitored the rehabilitated sites closely to see whether the seagrass was taking hold.
Every month the team measured environmental parameters that could affect seagrass growth, such as water temperature, salinity, acidity, turbulence, sedimentation and dissolved oxygen levels.

By the fifth month, the team began to see signs of success – it seemed the island’s seagrass was growing back.
The quadrats had given the sprigs the extra stability they needed to take root.
“We could visibly see an increase in biodiversity in these areas,” says Bupathy.
“We saw a great variety of fin fish, molluscs, horse fish, sea turtles.”
The seagrass meadows that had acted as donors had replenished the lost stock too and were as dense as ever.

The degraded seagrass meadows recovered with the help of the targeted transplant process, and the donor areas replenished their lost stock too
(Credit: SDMRI)

But, as fish and other marine life began to return, so too did the fishermen.
Nets from bottom-trawlers began to pull up the newly transplanted seagrass.

The team kept diving, reaffixing the shoots when they were pulled up.
Rough weather between April and September often impeded their work, but in the eight months when the seas were calm, the restoration project made steady progress.

The race against the trawlers often meant long hours underwater, with quick meals on boats.
Bupathy remembers one occasion when her nose started to bleed after she had dived despite having a cold.
Ashok recalls the small scratches and bruises from corals she brushed past.
Seeing the seagrass beds grow and thrive, however, made up for any discomfort.
“Watching the ecosystem take shape and grow diverse was very rewarding,” Bupathy says.

There was another reason besides preventing the erosion of Vaan Island that encouraged the researchers’ dogged persistence.
Losing seagrass meadows is akin to mass deforestation on land, and it can have a domino effect because seagrass is sensitive to changes in temperature.
“Rapid ocean warming in the recent decades have shrunk carbon-storing seagrass meadows, which in turn accelerates global warming,” says Roxy Mathew Koll, a climate change scientist at the Indian Institute of Tropical Meteorology in Pune.

All of which makes the efforts of Bupathy, Ashok and their colleagues more timely.
“The restoration of seagrass meadows along the Indian coast can help in saving the ecosystem,” says Koll.
“India has a large coastline, so if this is successful, it can be replicated for other similar environments along the coast – this will contribute to national effort to mitigate emissions and as much as possible, to reverse climate change.”

When the seagrass is restored, it is hoped that species such as the dugong will thrive again in the Gulf of Mannar, where it is currently under threat 
(Credit: Getty Images)

In the long run, enforcing India’s laws against disturbing seagrass will have to be part of the solution.
In 2019, a marine fisheries regulation management bill was proposed.
If it is passed into law, larger fishing vessels and mechanised trawlers would need to be registered and licensed under state departments.
They would need a permit to fish, which could lead to better monitoring and ultimately less destruction of the region’s seagrass and corals.

To date, the joint efforts to restore the coral and seagrass around Vaan Island and its neighbours has strengthened the degraded shoreline, making it less vulnerable to threats, says Patterson.
“This is the first attempt in India to fight to save a sinking island,” he says.
And it appears to be working – for now, Vaan island is stable.


The emissions from travel it took to report this story were 0kg CO2: the writer interviewed sources remotely, being familiar with the Gulf of Mannar area and having worked there several times in the past.
The digital emissions from this story are an estimated 1.2g to 3.6g CO2 per page view.
Find out more about how we calculated this figure here.

So far, nine acres of degraded seagrass have been rehabilitated in the Gulf of Mannar.
As well as at Vaan Island, other fast-eroding spots such as Koswari Island, Kariyachalli island and Vilanguchali have had successful transplants.
Two further acres have been restored around islands in Palk Bay.
The researchers are hoping that in time the restored seagrass will woo back endangered mammals like the dugong.

Sunday, March 1, 2020

Swath vs. Mono Hull

Challenge between SWATH tender "DÖSE" and two 30m mono hull vessels in 2013 :
what a difference in rough seas.