The momentous Trans-Pacific expedition concluded following Legs 5 and 6 in January 2024. Leg 5 led by Professor Alan Jamieon transited from Ensenada, Mexico to Honolulu, Hawaii covering 3608 nm. Leg 6 led by Heather Stewart transited from Honolulu to Papeete, Tahiti (French Polynesia) covering 3581 nm. Joined by Dr Jess Kolbusz, Dr Brett Gonzalez, Dr Georgia Nester and Alfredo Marchio these final legs continued with seabed mapping, lander deployments and for the first time submersible dives and eDNA extraction from water samples.
Expedition Summary Legs 1 - 6 June 2023 to January 2024
A total of 373,732 km2 of seafloor maps were produced, which is roughly the same size as Japan. In total 123 scientific lander deployments occurred across 40 sites. The landers Magna, Cranch and Omma each recorded 8-10 hours of high-definition video footage, acquired bottom water samples, and collected crustacean samples at each location. The lander Chiro also collected water samples and recorded 20-120 minutes of high-definition video data at 6 sites across Legs 5 and 6. Between all four landers 1,209,630 m (the equivalent to ~137 times the height of Everest) of data on the depth, temperature and salinity of the water from the surface to the seafloor were also acquired. Five submersible transects were completed resulting in more than 20 hours of high-definition video data of the seafloor, traversing a combined lateral distance of around 9 km.
These combined data will allow the scientific team to statistically investigate large scale patterns of species distribution at abyssal depths and how this is controlled by factors such as depth, temperature, habitat type, geomorphology, food supply from the surface, longitude/latitude and distance from shore. The scale of this expedition, at abyssal depths, has seldom been attempted before.
Above: Dr Jess Kolbusz and pilot Tim McDonald dive the subersible Bakunawa to 4950m.
Bakunawa (above), designed and built by Triton Submarines, is a two-person submersible vehicle operated from RV Dagon and supported by a number of small surface craft and the complement of full-ocean-depth-rated scientific lander systems.
Video data acquired by Bakunawa will give a unique insight into the understudied geo- and biodiversity of the abyssal plains, and the overlying water masses. During seafloor transects Bakunawa collected visual accounts of the seafloor habitat and substrate, as well as its associated benthic fauna. The manipulator arm was used to collect a single test push core from the seafloor.
In total 5 scientific submersible transects took place at five sites located in the eastern Pacific Ocean during Legs 5 and 6. Four transects were located across the abyssal plains, and one transect comprised a vertical ascent up the flank of an unnamed seamount. More than 20 hours of high-definition video footage were recorded.
Examples of benthic megafauna at abyssal depths, images from the submersible.
Environmental DNA (eDNA) refers to any genetic material sourced from organisms present in environmental samples (water, soil, sediment, air etc). Sources of this genetic material includes shed skin cells or tissue, blood, mucous, or faeces. As eDNA degrades relatively quickly in oceanic environments, sampling eDNA provides a snapshot of all organisms present in the environment at the time of sampling.
Pictured above Dr Georgia Nester from The Minderoo Foundation.
Peniagone sp. at 5200m (TP5) Pacific Ocean
Ctenophore at 4800m (TP5) Pacific Ocean
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