Finding Nemo 6: Living By Vibration
Living By Vibration
|Norfanz vessel, see full image slide show|
To explore deep sea habitats and biodiversity in the Tasman Sea, a joint Australian-New Zealand research voyage carried leading Australian, New Zealand and other international scientists to uncover new marine species and habitats. The NORFANZ research voyage explored deep sea habitats around seamounts and abyssal plains around Lord Howe and Norfolk Islands through to northern New Zealand. The voyage collected biodiversity samples, DNA tissue samples, seabed habitat data, photographs and video on seamounts at depths between 200 meters and 1.2 kilometers, and surveyed free-swimming animals that live in the water masses above and around these seamounts. Australia’s National Oceans Office – the body responsible for developing and implementing Australia’s Oceans Policy – and the New Zealand Ministry of Fisheries supported the four-week voyage between 10 May and 8 June.
With cooperation from the National Oceans Office , the NASA-sponsored Astrobiology Magazine chronicles the scientific notes written by the researchers onboard. As the director of the Hayden Planetarium, Neil Tyson, wrote about the marvels of biodiversity: "I do not know whether biologists walk around every day awestruck by the diversity of life. I certainly do. On this single planet called Earth, there co-exist (among countless other life forms), algae, beetles, sponges, jellyfish, snakes, condors, and giant sequoias. Imagine these seven living organisms lined up next to each other in size-place. If you didn’t know better, you would be hard-pressed to believe that they all came from the same universe, much less the same planet".
The main goal of the summer expedition mirrored that sentiment: to provide baseline information on the, nature and potential vulnerability of these unique habitats and their biodiversity. The results will give scientists interested in biodiversity a much better understanding of the species that live on and around the deep seamounts and ridges throughout the Tasman Sea, many of which were new to science. The information will also enhance and contribute to international collaboration in oceans management.
Day 16, 25 May 2003.
Mark Norman , Museum Victoria
Low swell (~2 m), 18 knot E, 18 ° C
Beautiful unusually calm day yesterday. In the afternoon, the ratcatcher net lived up to its name and caught lots of rattails. The most common fish in the net was the Globe-headed Rattail, Cetonurus globiceps, a distinctive fish with a swollen soggy head and little narrow tail (hence the name). This catch also caught many basketwork eels, Synaphobranchus capensis . They get their name from the criss-cross pattern on their bodies visible when their skin is scraped off. One eel had a squid sticking out its mouth that proved to be as long as its own body. The third common group in this catch was again the slickheads. Amongst this haul was one of the stranger relatives of sharks, a Pacific Spookfish, Rhinochimaera pacifica.
|Viperfish, see full image slide show|
This catch also included a new species of small skate of the genus Notoraja. Skates differ from rays in that they have no barbs on the tail. This new species is dark underneath and light on top. Most fish in shallow ocean waters, such as tuna, have a dark upper surface and a silver reflective underside. This is called "counter-shading" and hides the animal from above by the top matching the dark water below, while the silver underside matches the bright sunlight above. Many creatures that live on the deep-sea floor (including this new skate species) have the opposite colours (dark below and light on top). This is known as "reverse counter shading". This stops them being obvious when seen from above against the light mud or from below against the dark sea.
We also caught another type of rare jelly-like fish from the family Aphyonidae. This one is a new species in the genus Sciadonus. Like the species caught yesterday, it is virtually blind and would find its prey by feeling vibrations in the water around it. Andrew Stewart of Te Papa, New Zealand found and identified the perfect specimen of this rare fish group which was caught much shallower than is normal for these fishes, 900 m deep when they normally occur >1700 m.
Between trawls we had a safety drill to test our mustering abilities and to test the foam fire hose needed in case of fire in our alcohol stores.
Overnight the rattail theme continued with an exciting catch, a massive 11 kg Giant Rattail, Coryphaenoides rudis, as big as one of our onboard experts on this group. Dr Tomio Iwamoto from the California Academy of Sciences in San Francisco held up this massive, rough-scaled fish. Rattails belong in the family Macrouridae, the biggest and most diverse family of mid- to deep-water fishes. They go under various names including grenadiers and whiptails. The grenadier name comes from one of the first to be described having a peak on its head shaped like the helmet of the grenadier soldiers.
The rattail catch yesterday also included two specimens of the species Coryphaenoides grahami: a special species as it was named by Dr Iwamoto after Ken Graham of NSW Fisheries. Both fish experts are onboard the NORFANZ cruise.
Today we trawled around 850 m deep over soft mud made of the dead bodies of billions of microscopic creatures known as foraminiferans: the mud is called "foram ooze". The soft seafloor must be good for foraging fish because we caught a large number of bottom-dwelling sharks. Included in this catch were numerous Black Sharks, Centroscymnus owstoni , which typically occur at depths from 600-1200 m deep.
This shark is taken in commercial deep-sea trawls off eastern Australia and is sold in Melbourne as "flake" and Sydney as "deep-sea boneless fillet". Members of this genus are the deepest occurring of the sharks, having been recorded down to 3.6 km deep. Other sharks included lantern sharks (genus Etmopterus) and long-snouted dogfish (genus Deania ). This catch also included pretty cup corals, long coiled whip corals and some very snotty slimy sea cucumbers.
A subsequent trawl came up with more sharks and three excellent squid species: a hooked squid (family Onychoteuthidae), a flying squid (family Ommastrephidae) and a jewel squid (family Histioteuthidae).
We are now steaming west towards our next site.
Day 17, 26 May 2003.
Mark Norman, Museum Victoria
Low swell (~2 m), 14 knot SE, 18 ° C
It’s 6.30 am and the Sherman sled is down sampling the top of a small seamount several hundred nautical miles south east of Lord Howe Island (1 nautical mile = 1.85 kilometers). It is an old volcano formed millions of years ago with an obvious crater on top. This follows an earlier orange roughy trawl on the sides of this seamount.
|Colorful Alfonsino, see full image slide show|
The nets that we use sample in different ways. The captain, Andrew Leachman, bosun Mike Steele and crew members Craig Robinson and Barry Fleming helped explain to me how all the nets work and all the terminology. The biggest net is the "orange roughy trawl", the same as those used by deep-sea commercial trawlers. It has a long conical net with wing-like extensions going out from each side.
At the end of the wings there are two large steel plates known as "doors" or "otter boards". As the net is towed, these doors glide outwards and hold the net mouth open. The mouth of this net is about 16 m across and 7 m high. Along the top of the rectangular net mouth is the "head line", held up by a row of large floats. Along the bottom edge is the "ground rope" loaded with large steel balls known as "roller bobbins". The orange roughy net samples along the seafloor, the large bobbin balls rolling over irregular ground. This net has quite a large mesh size and is used to catch larger and faster fish.
The "ratcatcher net" is a slightly smaller modified orange roughy net with two basic changes: a ground rope with small rubber rollers and a finer mesh rear-end of the net (the "cod end"). This net is towed slower and samples more from the seafloor, including smaller fish and more invertebrates. It is used on flat bottom, sand or mud. Sensors on the doors and head line of both these net types send up signals on the depth of the doors and whether the net is trawling in the right way.
The next net is the "beam trawl". This net has a round pine beam four meters long that joins two steel frame skids together. The net is towed from this frame. The lower edge of the net mouth has a ground rope with small rubber disks. It has two net cones, one inside the other: a fine mesh outer net and a super fine mesh inner liner. This trawl is used to sample seafloor life such as corals and bottom-living invertebrates and fishes. The wooden beam is used to hold the two metal skids apart and keep the net open without needing doors. Wood is used instead of stell because it can break. Under pressure the wood snaps and the net and two steel skids can still be brought to the surface, complete with the fish catch inside. The ship carries replacement beams.
The toughest sampling device on board is the "Sherman sled", named after the Sherman tank. This steel-framed sled weighs 1.5 tonnes and is used on especially difficult bottom types. It has thick steel skids to slide over rocks and can sample both ways up. It tows a short net with a fine mesh liner. In case the sled gets stuck, it has four sets of "weak links". These are chain links of known breaking strain that break when the sled becomes wedged. As they break, it shifts the point of attachment to different corners of the sled to pop it out of any jam. The sled also has "sacrificial chains" in front of the scraping blades, which will break if they hit any rocks or else pulverise the rock.
After catching quite a few sharks yesterday lunchtime, a trawl at similar depths last night got very few sharks. Ken Graham of NSW Fisheries suggested that this made sense as sharks such as brier sharks (genus Deania) feed mainly on lanternfishes (family Myctophidae), one of the many groups of fishes and free-swimming invertebrates that rise up into shallower waters at night to feed. It is likely the sharks swim up with their prey. These vertical migrations happen every night in oceans worldwide. Free-swimming creatures move on mass up towards the surface to feed under the cover of darkness. They get so thick that they can be picked up on echo-sounders as a distinct layer in the sea. Dr Malcolm Clark, a fisheries scientist onboard from the National Institute for Water and Atmospheric Research in New Zealand explained that this is known as the "scattering layer", where high densities of zooplankton and midwater fishes move together in a mass from depths of around 700 meters up towards the surface.
|Slender Lanternfish, see full image slide show|
Their exact depth each night depends on how much night light there is, on black moonless nights many species come right up to the surface. With a full moon, they may stay several hundred metres down. It’s all about having enough light to see food but not be easily seen by predators. Many of these creatures, particularly the fishes and squids produce light, just enough on their undersides to hide their silhouette from nasties below.
Other creatures collected overnight included lots of small flatfish known as tongue soles (Symphurus sp. B), silver roughies ( Hoplostethus intermedius) and some deep-sea batfish (family Ogcocephalidae).
This morning, Sherman brought up a few urchins and anemones while the orange roughy trawl brought up some deep-sea scorpionfishes (genus Helicolenus), more silver roughy, some Ribaldos ( Mora moro ) and anemone hermit crabs.
An orange roughy trawl just before lunch contained quite a few Alfonsino (Beryx splendens). This brightly coloured fish is an important commercial species elsewhere. Our material will provide important data on distribution of this species while tissue samples will aid population and stock assessment studies. This trawl also contained an especially weird stargazer, Pleuroscopus pseudodorsalis.
As I write this, the NIWA Seabed Mapping team are searching for good ground to put down the orange roughy trawl again.
Day 18, 27 May 2003.
Low swell (~2.5 m), 20 knot SE wind, 16 ° C
Mark Norman , Museum Victoria
Today is less frantic as we steam for 16 hours to our next site, site 11, on the south side of Wanganella Bank (also known as West Norfolk Ridge). So people are catching up on notes, databases, organization, gear, specimen storage, cruise T-shirt design and sleep.
We are cruising at around 13 knots. The "Tangaroa" is a very stable ship. This stability is maintained by an "anti-roll system". This consists of a long rectangular water tank under the floor of the bridge. It is 1.5 m high and the full width of the ship (16 m across). Inside this tank at either end are fixed steel plates in pairs with a narrow opening aimed at an angle towards the centre of the tank. Up to 20 tonnes of water can be held in this tank.
|Tangaroa vessel, see full image slide show|
When the ship rolls one way the water moves slower and counters the rolling action. By the time it leaks through to the other end it is in time to counter the roll the other way. It ends up giving a very smooth ride. The "Tangaroa" has travelled widely including cruises throughout the subantarctic islands and SWATH mapping in Antarctica. It is capable of rolling from side to side to a 60 degree angle without capsizing. As the captain Andrew Leachman says, "At this angle it is easier to walk on the walls than on the floor!" As the ship is only 70 metres long it can be a lumpy ride directly into big swell as the ship is not long enough to ride across several wave peaks at once, so that it can fall into the troughs in big seas. The bends in the plates above the bow show the landing can be rough, these bends coming from surviving an 18 m swell.
After leaving our small seamount yesterday, we moved out to do some sampling in deeper waters. At around 3 am last night we did the last of these deep sites at around 1100 m deep. The catch included some large black chimaeras, a different species of spookfish (long-nosed chimaeras), a rare eelpout, a Rudderfish (Centrolophus niger ) and a perfect Giant Hatchetfish (see "creature feature"). The invertebrates included some glass squids (family Cranchiidae), large anemones, a muscular bottom-dwelling octopus (genus Benthoctopus) and an excellent jelly-like finned octopus.
As we steam east, the crew are preparing the nets for sampling at around 8 pm tonight. Bruce Barker, Senior Technical Officer from CSIRO Marine Research is also preparing the headline still camera that is attached to the net. Bruce is onboard to oversee the operation of a Photosea camera, a modified Nikon in a special underwater housing that allows it to be sent down to 6 kilometres deep. This camera is on a timer so that it starts photographing once the net has reached the seafloor. It can then take 250 high resolution images at 12 second intervals.
The other camera system is a drop frame containing a Benthos camera (also based on a modified Nikon 35 mm camera) operated by Miles Dunkin and Richard Garlick of NIWA. It is lowered vertically, with a weighted line beneath it. When the line hits the seafloor, the camera takes an image. As the ship drifts and the cage bobs up and down it takes photos along the seafloor. It can take up to 800 images in one go. Both cameras use wide angle, 28 mm lenses. Bruce can process all images onboard and give direct feedback on seafloor types.
As I send this everybody is getting ready again. It will be a busy night ahead.
|Torpedo, see full image slide show|
The Commonwealth Scientific and Industrial Research Organisation (CSIRO) and the New Zealand National Institute of Water and Atmospheric Research Ltd (NIWA) are providing scientific support for the voyage. The NORFANZ voyage will use NIWA deep-sea research vessel, the R.V. Tangaroa (NORFANZ).
The expedition received considerable interest from scientists worldwide. Twenty four scientists from more than eleven research organisations will be represented onboard, including staff of CSIRO, Hobart; Museum Victoria; the University of Tasmania; Australian Museum; Queensland Museum; Northern Territory Museum; NSW State Fisheries; Te Papa, Wellington; National Institute of Water and Atmospheric Research, New Zealand; Institute de Recherche pour le Développement, Noumea; Natural History Museum, Paris; and California Academy of Sciences, San Francisco.