Alvin, Please Deploy My Trap There
The East Pacific Rise (EPR) is a mid-ocean rise at
a divergent tectonic plate boundary and a fast-spreading mid-ocean ridge. Along this
axis, there is a lot of hydrothermal venting activity. However, this venting is ultimately transient,
leaving only the sulfide mineral-rich deposits after the fluid flow
stops. These inactive sulfides are beautiful and distinct features on
the seafloor. They aren't teeming with the iconic life present on active vents,
but they are not devoid of life either.
I spent January and February on a
team, led by Dr. Lauren Mullineaux from WHOI and Dr. Jason Sylvan from Texas A&M,
exploring some inactive sulfides. We are using the human-occupied submersible
(HOV) Alvin to image, collect animals living on the rocks, and retrieve rocks!
This is my first experience working with Alvin or a vehicle with manipulator arms.
From planning sample collection, sorting samples, diving in Alvin, and seeing
the deep ocean with my own eyee, this experience has been formative as a deep-ocean
scientist.
One element that has transformed
my thinking is the ability to choose where and when samples are collected. This
concept is novel because my PhD focused on the ocean's deepest zone – the hadal
zone. The hadal zone is depths from 6,000 to nearly 11,000 m at Challenger Deep
in the Mariana Trench. For reference, the depth of the EPR is ~2500 m. Studying
the hadal zone is even more challenging than other parts of the deep ocean due
to these extreme depths. Our primary tool for biological sampling is autonomous
free-landers with traps baited with smelly fish, like mackerel, to attract andhopefully catch scavengers. The scavengers that I focused on were amphipods, a
type of crustacean. We had a targeted depth. But they landed where they landed.
As part of this cruise, I used
two baited traps to examine the scavenging amphipod community of the active and
inactive vents. Both baited traps have a similar design – a PVC tube with a
funnel and a cap and mesh on the other. One trap was mounted on a lander. This
lander was deployed for 24 hours, carried a McLane Pump to sample live larvae
in the water column for a pressure chamber experiment onboard, and was placed
on the edge of a vent by Alvin. The second trap was deployed and recovered by
Alvin – and has lovingly been named the Amphipod Handbag. The Handbag is the
same tube and funnel design but modified with weights on the horizontal side to
keep it weighted down and a rope handle for Alvin's manipulator arm to set it
down and pick it up. While the design is simple, plenty of thought went into
making sure the Handbag fit into a biobox with the lid closed, it laid down
nicely, and the trap was vertical when picked up. Also, the exciting part was
deciding where precisely to place the Handbag – like on the edge of a Riftia
bush and mussel bed and at the top of Lucky's Mound – to capture a different
niche than the trap on the lander. Excitingly and primarily, I spotted
differences across deployments and potentially even a new species.
My highlight happened on January
26, 2024, when I was the starboard observer on Alvin Dive 5224 to an inactive
vent called Lucky's Mound. I got to see with my own eyes the deep ocean and
deploy and recover the Handbag. Seeing the deep seafloor after many years of
thinking about it was utterly magical, profound, and nearly indescribable. Beautiful,
alive, and so complex. Truly, it was a privilege to see this small part of the
deep ocean in person. This experience's mark on me will likely propel the
questions I ask for the rest of my career.
As the cruise winds down and we
steam to Costa Rica, I am reflecting on my growth thanks to Alvin and its
Amphipod Handbag. More importantly, I am ready to get back to WHOI and uncover the
results and meaning of this new data.
The EPR Biofilms4Larvae project is support by a
multi-institutional NSF grant: OCE-1948580 (Arellano), OCE-1947735
(Mullineaux), OCE-1948623 (Vetriani).
The Inactive Sulfides project is support by a
multi-institutional NSF grant: OCE-2152453 (Mullineaux & Beaulieu) and
OCE-2152422 (Sylvan & Achberger).
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Wide
view of the first deployment of the Amphipod Handbag deployed by Alvin at the
base of a Riftia bush (tube worms) at an active vent named Tica Mound. Credit:
Shawn Arellano, Chief scientist, Western Washington University; Alvin Operations
Group; National Science Foundation; ©Woods Hole Oceanographic Institution
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| Looking on to the recovery of the Amphipod Handbag by Alvin. Credit: Shawn Arellano, Chief scientist, Western Washington University; Alvin Operations Group; National Science Foundation; ©Woods Hole Oceanographic Institution |
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Wave goodbye at the Alvin hatch before the commute to work
on the seafloor. Credit: Costantino Vetriani. |
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