Exploring the Mariana Trench

Sink It – The First Lander Recoveries

SOI/ Paul Yancey
Nov. 13 2014

Sink it—bring it up, sink it—bring it up.  Sinking the equipment is fun, but bringing it back is the real thrill.

These small amphipods, showen by Dr. Stuart Piertney were captured in the amphipod traps and the fish trap.
These small amphipods, showen by Dr. Stuart Piertney were captured in the amphipod traps and the fish trap.SOI/ Linda Tatreau

A lander is a mechanical platform system that can independently hold instruments, carry tools, produce imagery, measurements, etc. for underwater observation and sampling. Every lander sinks with flotation devices and weights attached beneath it; the steel plates individually weigh 18 pounds.  Each lander holds up to 14 weights for a whopping total of 252 pounds.  At the first station of our expedition, at a depth of about 3 miles, the landers are left overnight or for up to two days.  When the landers are deployed, a series of information is recorded including the time of launch, depth, latitude and longitude.

Recovery

There are no tethers connecting the landers to the surface, so they are all alone.  An acoustic signal is sent to the lander when it’s time to surface, and the landers descend and ascend at about 30 meters/minute, day or night. Each lander is equipped with a tall red flag, colorful buoys (or the bright yellow lollypop), a VHF beacon (radio transmitter), and a strobe for recovery at night or during unfavorable conditions.  All of these features aid in finding the lander amongst the vast blue expanse of the ocean, often in high waves and chop.  If no radio signal is found, all available crew line the rails to keep on eye for the buoys.

Rock Grabber

Colorful flags and buoys are attached to the landers so they are visible from the ship when they are ready for recovery.
Colorful flags and buoys are attached to the landers so they are visible from the ship when they are ready for recovery.SOI/ Paul Yancey

The rock grabber was the first lander recovered on this expedition.  The instruments “jaws” were partially open upon surfacing, so unfortunately no rocks or sediments were collected.  However, the lander’s water sampling devices worked, so there are water samples currently undergoing chemical analysis.  Upon recovery of the rock grabber, two camera landers called the hadal and abyssal were also picked up.

Creatures from the deep

Both the hadal and abyssal cameras captured pictures of rattail fish, cusk-eels, and a lot of shrimp. The hadal lander also carry three PVC tubes to trap amphipods (shrimp-like creatures) common in the deep-sea.  The tubes have funnels on both ends that are baited with fish, which the amphipods can find their way into, but cannot find their way out. The most exciting recovery for many of us was the amphipod fish trap. The first recovery brought up about 200 small amphipods! Typically, shallow amphipods are tiny, but these deep-sea ones can be much larger.  The largest caught so far has been about two inches in length and completely white.  A few of the amphipods were a bit darker in color; and so far there have been at least four different species.

Two of the landers have bright yellow lollypops, made of syntactic foam used for both flotation and visibility.
Two of the landers have bright yellow lollypops, made of syntactic foam used for both flotation and visibility.SOI/ Linda Tatreau

Another type of fish trap is baited with mackerel on the inside of the trap, and squid baited to the exterior hooks. The trap has entry areas for large and small fish; however, the first recovery came up with no fish in the trap or on the hooks. Luckily, it was quickly re-baited for another deployment.

The scientists working with the coring respirometer (CR) (another lander) are filled the greatest anxiety.  They must wait two full days for recovery.  The CR has four clear tubes that drill a few centimeters into the sediment upon landing on the seafloor.  The water in the tube above the sediment is kept circulating and sensors measure the oxygen content of the water.  Oxygen consumption can give an indication on the amount of life in the sediments, both microbes, and larger life such as worms.

A Surprise Visitor

You can see the clear tubes that drill a short distance into the sediment on the coring respirometers shown here.  Sensors measure oxygen content in the water above the sediment to determine oxygen consumption of the organisms found in the sediment.
You can see the clear tubes that drill a short distance into the sediment on the coring respirometers shown here. Sensors measure oxygen content in the water above the sediment to determine oxygen consumption of the organisms found in the sediment.SOI/ Linda Tatreau

Hurray, a whale shark!  Not very big, but swimming alongside of the ship as we do another recovery.  Unfortunately, everyone was so entranced during this special and brief appearance that no one got a picture.  So far we have also encountered mahimahi and flying fish, and have heard dolphin clicks and whale moans on the hydrophone. Stay tuned as we are just a few hours from the CR recovery, and who knows what new species is around the corner.


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