Science

We have three teams of scientists aboard the RRS James Cook: the biologists, the geologists, and the chemists (including an engineer and a physical oceanographer). We are working together to explore and understand how these extraordinary vents form, and the impact that they have on our planet.

The Biology Team Objectives


Deep-sea vents are home to island-like colonies of marine life, and comparing what lives at different vents around the world shows us how species disperse and evolve in the deep ocean. We need to understand those processes because we are increasingly using resources of the deep ocean in our everyday lives, and thereby having an unseen impact on our planet’s largest realm. The Cayman Trough hosts the deepest known vents, and its vents are also quite isolated from vents known in the Atlantic Ocean. So far we have found several new species of deep-sea animals at these vents, which tell us more about what lives in this deep and isolated part of the Caribbean. But there are still plenty of species that we need to examine to gain a full picture, so we will be collecting specimens for further analysis. We also want to understand how biodiversity, reproductive development, and the genetic structure of populations vary between the two very different vent fields in the Cayman Trough, so we will also be mapping the patterns of life around them. Finally, we will be deploying experiments on the seafloor to examine how species colonise island-like habitats in the deep ocean.

The Biology Team are: Diva Amon, Jon Copley, Adrian Glover, Leigh Marsh, Verity Nye, Andrew Thaler and Paul Tyler.

Images below from the 2010 visit to the Cayman Abyss

(a) Aggregation of alvinocaridid shrimp on an active chimney at the Beebe Vent Field (BVF). (b) Anemones and microbial mats at the BVF. (c) Aggregation of dead mussel shells on the Mount Dent Oceanic Core Complex (OCC). (d) Empty tubes resembling those of siboglinid polychaetes on the Mount Dent OCC.

The Geology Team Objectives


Active hydrothermal vent fields on the seafloor give us insights into ancient mineral deposits in the geological record that are important sources for base and precious metals. The two Cayman Vent sites are unusual either due to their extreme seawater depth (Beebe site - BVF) or composition (Von Damm site - VDVF). We aim to understand the setting at each vent site and produce geological maps of both. The difference in the host rock, fluid temperature and seawater between the two sites provides an ideal study area for us to investigate formation of hydrothermal deposits. Supercritical conditions greatly enhance the mobility of base and precious metals in a hydrothermal fluid. The temperatures and pressures are so high at the Beebe that it could act as a natural laboratory to study these effects in a natural environment. The primary metal enrichments are enhanced further by secondary mineral formation and we would like to sample and understand this process in detail. Ultimately understanding how active mineral deposits form at the seafloor helps us interpret the global geological record and help us to find new, enriched deposits.

The Geology Team are: Bramley Murton, Steve Roberts, Veit Huhnerbach, Tim LeBas, Alex Webber, Matt Hodgkinson and Peter Talling

Images below from the 2010 visit to the Cayman Abyss

(a) Peak of sulphide edifice at the VDVF, depth 2,300 m, covered by an aggregation of alvinocaridid shrimp. (b) Clear vent fluids and alvinocaridid shrimp at the VDVF. (c) High-temperature venting at the BVF, depth 4,960 m. (d) Diffuser structures ornamenting sulphide chimneys at the BVF.

The Chemistry Team Objectives


Hydrothermal venting at the seafloor plays a key role in controlling the composition of the oceans. Hot, acidic, metal-rich fluids pump chemicals into the deep ocean to form large mounds of metal-rich sulfides and a plume of metal-rich particles that rises up through the deep water column. We know that the plume rises over 1 km from the seafloor at these deepest vents in the Cayman Trough; this is an extraordinary distance for plume particles to be transported upwards. Our goal in this expedition is to sample the extreme fluids, determine the temperature (in excess of 400°C), capture and measure the reduced gases emanating from the vents and assess where the Cayman Trough vents fall on the known spectrum of behavior on the seafloor. We aim to trace the metal-rich particles from where they are first formed at the vent orifice, upwards along the plume rise path and ultimately as they are dispersed and fall-out into the underlying sediments. Even after sedimentation these metals continue to be processed and react with overlying seawater. We want to know the inputs and fate of metals in this extreme environment and ultimately the impact on the ocean and life.

The Chemistry Team includes: Alain Castillo, Valerie Chavagnac, Jeff Hawkes, Will Homoky, Aly Lough, Rachel Mills and Kate Stansfield.


Deep sea hydrothermal vent chemistry diagram
Image courtesy of Wikimedia

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