With legs 3 and 4 recently concluded, the ambitious expedition exploring the abyssal plains of the Pacific Ocean onboard the RV Dagon resulted in a total of 13,478 nautical miles of transit, 258 307 km2 of maps, and 81 lander deployments.
Dr Todd Bond and Dr Jessica Kolbusz led legs 3 and 4 respectively, continuing the work completed on legs 1 and 2. They were joined by Megan Cundy and Dr Yakup Niyazi. As explained previously, the purpose of this expedition is to study the diversity of the deep-sea life, habitat, and environmental conditions over the eastern Pacific Ocean.
From Tahiti, RV Dagon returned north, towards Hawaii but took a route further west of Leg 2. After a couple of days in port, the vessel continued eastward for leg 4 – bound for Ensenada, Mexico. Leg 4 was approximately 18° south of Leg 1, with cooler seafloor temperatures.
The videos collected from the baited landers provided more high-definition footage of the abyssal flora and fauna communities. From this, we can investigate biodiversity, abundances, and the behaviours of observed species, and use the high-resolution images to determine habitat and substrate types. In addition to the commonly observed species seen throughout legs 1 to 4 - such as the deep-sea grenadiers (Coryphaenoides), cusk eels (Bassoazetus), deep sea decapods (Benthesicymus crenatus and Cerataspis monstrosus) and amphipods (Paralicella) – we also observed a deep-sea urchin at 5400 metres (Echinothurioida), and a stunning looking silver cusk eel (Bassozetus sp.).
Above: Deep sea urchin (Echinothurioida) observed at 5400m from Leg 4
Oceanographic data is not frequently collected over basin-wide scales, let alone with complementary species and habitat information. The fundamental environmental conditions in temperature, salinity, and pressure (depth) collected allow us to make comparisons between these environmental conditions on the seafloor and the observed species and habitat captured by the landers and the mapping team. The preliminary data collected already shows meridional and zonal variations in bottom temperature and details consistent with mean conditions on the seafloor. We observed cool temperatures around Hawaii which is consistent with cooler waters originating from the South Pacific.
Preliminary average bottom water conditions at each site for legs 1 – 4 of the Trans-Pacific Expedition. The locations are approximate and plotted using the m_map toolbox. The bathymetry is the basic default elevation database within the m_map toolbox for ease of reproducibility.
Bassozetus Sp. at 4700m (TP3) Pacific Ocean
Cerataspis monstrosus at 4700m (TP3) Pacific Ocean
𝘊𝘪𝘳𝘳𝘰𝘵𝘩𝘢𝘶𝘮𝘢 𝘤𝘧. 𝘮𝘢𝘨𝘯𝘢 captured on lander cameras at 4,800m