Leg 1 (May 7th – May 23rd)

Leg 1 begins in the Malacca Strait, one of the busiest shipping lanes in the world. Onboard, the paleoceanography team utilized the ship’s sub-bottom profilers to identify areas of interest for collecting sediment cores to capture snapshots of historical oceanic conditions, nutrient levels, sediment composition and microbial life. Deploying a gravity core, a tool composed of a long collection cylinder, allowed researchers to autonomously collect sediment cores up to 3-meters long that are then frozen in the ship’s laboratories.Combining this data with water quality measurements from CTD castsgives researchers unique insights into the present and historical ocean and seafloor dynamics of this fluctuating region.

After exiting the Malacca strait, the OceanXplorer began mapping the Mergui basin – an area suspected to have evidence of a submarine landslide. The ROV pilots collected push cores for the geoscience team onboard, while submersibles collected footage of a unique aggregation of giant isopod burrows in the surrounding area. After transiting north of Banda Aceh, the search for hydrothermal vents began.Although two plume signatures were detected by the multibeam sonars, the ROV could not locate their source. However,the team was successful in finding a shallow vent field near the volcanic Weh Island and deployed a team of divers to conduct visual transects, sediment sampling, rock and water sampling as well as CTD casts. Most surprising was the discovery of dozens of Catshark eggs nestled in the crevices of the vent sites. It's suspected that this species is utilizing the heat from the vents to incubate and accelerate development of their young – a behavior that has also been reported in Pacific White Skates in the Galapagos Islands (Salinas-de-León et al., 2018).

The OceanXplorer transited to the offshore Simeulue Basin to conduct CTD casts and ROV dives in the Sunda Trench. The geoscience team onboard sent the ROV to the site of the suspected epicenter of the 2004 Indian Ocean earthquake and tsunami responsible for devastating damage along the Indonesian coastline, as well as the coastlines of Malaysia, Maldives, Seychelles, Thailand, Myanmar, Sri Lanka, India, and even across the Indian Ocean in Somalia. The ROV dive revealed the area is devoid of life compared to the high biodiversity found in the abyssal plain to the north, indicating potential ongoing geological disruption in the area.

On leg 2, OceanX partnered with researchers from Konservasi International (KI) to conduct biodiversity surveys within Indonesian Fisheries Management Area (FMA) 572 along the coast of Sumatra. FMA 572 is characterized by productive demersal and pelagic fisheries anddesignated as an Ecologically and Biologically Significant Area due to the seasonal upwelling that sustains these populations. OceanX worked with KI biodiversity experts to deploy BRUVS and submersible stakeouts toprovide updated data on regional fisheries stocks and assess the efficacy of current MPA sites located in the FMA seascape.

KI scientists deployed Baited Remote Underwater Vehicles (BRUVS) tocapture footage of biodiversity composition in shallow waters 30 meters deep. BRUVS were deployed at a total of 16 different stations collecting over 56 hours of footage. Initial BRUV footage revealed less biodiversity than expected at most sites with a noticeable lack of large commercial fish in particular. At most sites, red-toothed triggerfish (OdonusNiger) were the dominant fish population often appearing in large schools swarming the bait boxes. Large predatory fish such as groupers and snappers were noticeably absent. An overall lack of biodiversity applied to sites within Marine Protected Areas (MPAs) as well. In fact, there were no observational differences in overall abundance and biodiversity of fish or megafauna inside and outside MPA’s. This indicates the need for re-evaluation of MPA zonation and fisheries stock assessments

At deep stations (deeper than 30meters), the submersibles deployed bait bags and conducted one-hourlong stakeouts to monitorfaunal activity. The bait attracted a variety of organismsincluding gurnards, moray eels,and a curious six-gill shark. In parallel with the BRUV deployments, researchers also collected 298 water samples for eDNA analysis to serve as points of comparison with the observation results.

Understanding where commercial fish species are located is important work to determine an area’s estimated fish stocks. However, fish are highly mobile animals and utilize different habitats during different life stages as they grow. Fish start off life as eggs and develop into fish larvae (most are no longer than your thumbnail). At this stage, they are particularly vulnerable to predation and other environmental stressors. Knowing where these vulnerable life stages occur in the ocean is a crucial step to enacting protection policies to ensure these fish reach adult size.

KI Researchers assessed the composition of commercial fish larvae using bongo nets and plankton tows deployed at 100 meters, 200 - 300meters and 300 - 400meters. Most ichthyoplankton were located in inshore waters with plankton community composition varying by station. Certain locations were dominated by fish eggs while others were dominated by cephalopod larvae. Post-hoc eDNA and morphology analysis will confirm species identification as well as identify trends in population connectivity.

The oceanography of West Sumatra is influenced by water masses from the western and equatorial Indian Ocean. These water masses are characterized by their high saline and low-oxygen content, particularly along the coasts of Sumatra and Java. The region is also known for its internal waves of exceptionally high amplitude, which play a crucial role in various oceanic processes, including nutrient transport and primary productivity. Oceanographers onboard the OceanXplorer sampled these watersfor nitrate and chlorophyll-a content as well as microplastics content to understand circulation patterns within these dynamic water masses.

The oceanography of West Sumatra, is influenced by water masses from the western and equatorial Indian Ocean. These water masses are characterized by their saline and low-oxygenated content, particularly along the coasts of Sumatra and Java. The region is also known for its internal waves of exceptionally high amplitude, which play a crucial role in various oceanic processes, including nutrient transport and primary productivity. Oceanographers onboard the OceanXplorer sampled these waterfor nitrate and chlorophyll-a content as well as microplastics content to understand circulation patterns within these dynamic water masses.

OceanX collaborated with experts in coelacanth research and behavioral ecology from Aquamarine Fukushima, and an award-winning Japanese documentary filmmaking team from NHK to search and document the ecology of coelacanths in Sulawesi, eastern Indonesia. Sulawesi is home to the only known extant coelacanth species, the Indonesian coelacanth (Latimeria menadoensis) - the other coelacanth species, the Western Indian Ocean coelacanth (Latimeria chalumnae), is listed as critically endangered.Using 72-hour stakeouts, the teams deployed ROVs and submersibles to conduct continuous study of the rare animals. During these stakeout periods, researchers captured several distinct behaviors for the first time on film. Post analysis of the film revealed the distinct flexibility and movements of the coelacanth’s muscular fins which may offer clues into the biomechanics of the land-sea transition of vertebrates over time. All footage from this collaboration will be incorporated into the upcoming documentary “Deep Ocean: The Kingdom of the Coelacanth” narrated by David Attenborough, which will delve into the evolutionary secrets of these ancient living fossils.