Deep Coral Diversity at Emperor Seamount Chain 2019

Onward to "The Emperors"

Previous bathyal fauna like octocorals have been sampled along the Aleutian Islands off northern Japan and on parts of the Hawaiian Ridge. Scientists have found significant differences in the organisms living in these locations and suspect that currents play a role in this distribution. One current in particular may play the most important role in coral distribution, the North Pacific Intermediate Water.

In the North Pacific there is only one range of seamounts between the Aleutian Islands and the Hawaiian Island chain that harbors bathyal species: the Emperor Seamount Chain. The North Pacific Intermediate Water crosses the chain at what is known as the Main Gap. This location will help the multidisciplinary team of scientists on Falkor identify this ecosystem transition. Up until now, most of the bathymetric surveys conducted in this area have been the result of transits, therefore lacking quality coverage necessary to pinpoint precise locations of study. This is why Falkor’s first task will be mapping the geologic features of the selected seamounts.

Proving the Currents

During their time on Falkor, the science team will combine a series of holistic experiments at six seamounts along the Emperor Chain to see if their suspicions are correct. Using currents, mapping, and radio isotopes to track water masses - as well as genetic sampling of corals - the team will determine the driving force behind coral distribution in this region. They may even find a new species of coral.

The soft-touch manipulator arms of Schmidt Ocean Institute’s ROV SuBastian will come in handy when picking up invertebrates and corals for imaging and genetic study. SuBastian will also be used to collect rock samples from the seamount, offering hidden clues of the past including circulation, chemistry, biology, geology, sedimentation and productivity. The team will use this information to reconstruct past environmental conditions going as far back as the last Glacial Maximum. This information will shed more light on the historical motives for the distribution and differentiation between the two biogeographic regions being examined.

In addition to the ROV work, Falkor’s CTD rosette will be used to identify an assorted mix of water masses that affect the types of organisms found at specific locations. Dr. Watling’s team believes that there are three water masses dominating the water column in the area with distinct geochemical signatures.

Seamounts are fascinating features of our oceans and taking a closer look at them is always extraordinary. The team is hoping to better understand the distribution of octocoral species on each side of the Main Gap, as well as investigate the processes that influence these distributions. They will first produce detailed maps of the seamounts visited; these will be used to determine optimal dive locations for ROV SuBastian to collect octocoral samples for taxonomic and molecular analyses. Water samples will be collected to better understand the origin and characteristics of the environment in which the corals reside.