Diving Thoughts

Scientists believe that American lobsters are using jet assistance to travel faster across the ocean floor. Lobsters have small paddle-like structures called pleopods on their abdomen, and they can fan these pleopods to create a wake which propels them forward.

A graduate student and a professor at St Francis Xavier University in Antigonish, Canada, who presumably had nothing better to do, took the abdomen of a lobster, emptied out the tissue, and installed 8 small servomotors to fan the pleopods at the same rate that a lobster would. The pleopods pulled in water from around the lobster’s body and directed it out as a jet behind. This produced a surprisingly large wake and therefore thrust, which could help the lobsters move faster while walking along the bottom of the sea.

Pleopod shapes vary among different species of lobster, so the size of this effect is also likely to vary.

There’s more information and a good video of a lobster moving its pleopods on the BBC’s website.

In 1928, renowned Norwegian explorer, Roald Amundsen, was on a Latham 47 flying boat which disappeared on its way to Spitzbergen. He was attempting an expedition to rescue Umberto Nobile, an Italian, whose airship had crashed on a return journey from the North Pole. He and the surviving crew were marooned on pack ice. No-one knows exactly what had happened, although the plane had flown into foggy conditions, and it’s possible they had to put down on the water, which may have been too rough for the flying boat.

Now an expedition is going to try and find the plane. They believe that the last radio message was received while the Latham 47 was 19 miles south of Bear Island. Two ships are going to search 45 square miles of seabed using state of the art technology. They hope to find the engines, as the rest of the plane was made mainly of perishable materials.

You can read more in this BBC article, from which the above photo was taken.

Last year, after 3 months of marriage, Aleki Taumoepeau was working in Wellington harbour when he dropped his wedding ring. He quickly threw an anchor in to try and mark the site. Three months later he did a dive but couldn’t find it. This year, 16 months later, he went back to try again, armed with GPS coordinates. As he was getting cold and tired, he spotted the anchor at around 3 metres depth, with the ring lying really close to it. They’re now calling him Lord of the Ring.

Maybe Big-Ears at our dive Club could try something similar in the hope that, if he’s trying to recover his wedding ring, his missus might actually let him out to go diving.

The story is on the BBC website.

Last week a Tongan ferry, the Princess Ashika,  sank  with the loss of 73 passengers. 56 people were rescued. The ferry has been located and is at a depth of 110 metres. This week a New Zealand navy dive has managed to use an ROV to find and formally identify the vessel. The New Zealand Herald has some photographs and video from the navy on their website, which shows the ferry sitting upright on the seabed.

A salvage expert has said that it may cost several million dollars to salvage the ferry, and it is unlikely to happen.  The navy dive team can only carry out recovery missions to 60 metres, so unless specialist divers are brought in, it is unlikely that the human remains will be recovered either.

You can see some video here, or some photographs here.

There’s more on the Arctic methane story in this article from New Scientist.

Methane is a powerful greenhouse gas, so if large quantities of it are released into the atmosphere it could make climate change even worse.That may be starting to happen as researchers have found 250 plumes of methane bubbles that are rising from the sea bed off Norway.

Vast quantities of methane are trapped as methane hydrate in sediment under the Arctic seabed. Methane hydrate is a frozen substance made up of water and methane, which is stable under high pressure and low temperature. But as temperatures rise, the hydrate is starting to break down which can result in the methane being released.

The lower the temperature is, the less pressure is required to keep the methane hydrate stable.  Data collected over 30 years shows that it used to be stable at a depth of 360 metres, but recent evidence shows that it is now stable at depths of over 400 metres.  This is probably because this area of the ocean is now 1 C. warmer than it used to be.

Researchers have found that most of the methane is dissolving into the seawater and they have not yet detected any evidence that the gas is breaking the surface and getting into the atmosphere, although they emphasise that this doesn’t mean that it isn’t doing. But even if it’s not getting into the atmosphere, it is making the ocean more acidic, as it is combining with oxygen in the water to form CO2, which in sea water forms carbonic acid.

The full BBC story can be found on their website.

The following comes from a WWF Hong Kong email which I received this morning:

© Lindsay Porter / WWF Hong Kong

The Highways Department has recently released the environmental impact assessment (EIA) of the Hong Kong Zhuhai Macau Bridge (the Bridge) for public consultation. The Bridge cuts right through the middle of a major dolphin habitat. The impact on the dolphins of such a massive development is expected to be significant but difficult to measure, so the project represents a dangerous experiment to the dolphin’s very survival in our waters. WWF is now calling for your support to ask for more marine protected areas for dolphins, which should include:

• The two marine parks endorsed by the Country and Marine Park Board in 2002 at Southwest Lantau and Soko Islands and;
• The waters around the Brothers Islands and Tai O which are confirmed to be hotspots of dolphin occurrence.

Please submit a letter to the Environmental Protection Department (EPD) on or before 12 September 2009 when the public consultation ends.

The BBC website has a video of hundreds of turtles being released into the sea off Thailand by the Thai navy, to try and boost their population.  You can see the video here.

Fish eating killer whales (Orcinus orca) in the Avacha gulf off the coast of Russia tend to live in pods of 10-20 whales. But scientists have now observed 8 such pods coming together to form a super-pod of over 100 animals. This behaviour has also been seen in other parts of the world, such as Alaska, Antarctica, British Columbia and Iceland.

Observations have now shown that the whales rarely forage or feed in these large concentration, and since they have very few natural predators, it is unlikely that they are gathering for mutual protection. Instead it seems that the whales are using these large groups to socialise, and perhaps to assess potential mates.

The above photograph comes from this BBC article.

This from Mares:

Please be informed that we have discovered a quality issue on the O-ring assembled on the Nemo Air Quick Connector.

Under certain circumstances the O-ring can fail and consequently Nemo Air may start leaking through the Quick Connector. As a result, there is a continuous, albeit slow, loss of breathing gas. This situation could potentially lead to an accident, hence Mares has decided to issue a product recall. The solution already exists in the form of an O-ring of different material and hardness which can be retrofitted onto the Quick Connector of your current Nemo Air.

You can find out more from the Mares Home Page, where you can download a PDF with the full safety notice.

On 3rd August two divers died after getting into difficulties on a dive 8 miles off Filey in North Yorkshire. They were airlifted to Hull Royal Infirmary by an RAF Search and Recovery helicopter, but were pronounced dead on arrival.

Divernet has some more information.

Scientists have found that the yellow-lipped sea krait uses markings and movement into fooling predators into thinking that their tail is a second head. Sea snakes are highly venomous, but are still vulnerable to larger fish, sharks and birds. The markings and the way they move their tail may increase their chances of survival if they are attacked, by exposing the less vital tail instead of the head. But it could also be to deter attacks in the first place if predators mistake the tail for the venomous head, particularly while the snake’s real head is busy searching among coral for food.

Arne Rasmussen, from the Royal Danish Academy of Fine Arts’ School of Conservation in Copenhagen, Denmark, led a team studying the sea snakes off Bunaken in Indonesia. They have published their findings in Marine Ecology.

The above photo from Arne Rasmussen is taken from this BBC article.