The deep sea is home to a variety of understudied, otherworldly ecosystems that are in need of human understanding if they are to have any protection from encroaching deep sea fishing and mining activities. These systems support the global marine environment though habitat creation, nutrient cycling, and maintenance of biodiversity. However, they also happen to be found in areas with rich stores of oil, gas, minerals, and potential new pharmaceuticals. Understanding what ecosystem processes generate these key services is fundamental to their protection.

Characterizing Methane Seeps and Seamounts

The Pacific margin of Costa Rica is an area of seamount subduction where methane seeps, thermal anomalies, and non-subducting seamounts intersect and presumably interact. Despite several research expeditions to this region, scientists still know very little about how these types of ecosystems may be connected to communities in the rest of the oceans including the soft sediment background communities and deep-sea corals. To characterize these interactions, Dr. Erik Cordes, from Temple University, and his team of interdisciplinary researchers will use a framework coupling benthic sampling, near-bottom chemical sensor and photographic profiling, along with vertical characterizations through the water column from deep to shallow.

The 22-day expedition will visit multiple low-oxygen seep areas along the margin, and seamount sites out to the protected Isla del Coco National Park. The team will look to see how sites differ by depth, oxygen dynamics, pH, seep intensity, and the available substrate. At each site, a suite of sensors, instruments, and statistical methods will be used to combine biological and oceanographic surveys, transplant experiments, and vertical water column characterizations that will provide a full biogeochemical understanding of the area.

Exploring possible connections

Scientists believe there to be both chemical and biological linkages between seep sites, seamounts, and the surrounding environment. Corals and bivalves use calcium carbonate to build their skeletons and shells, which is less available in seawater with lower pH. It is possible that the oxidation of methane at the seep sites is a supplemental source for calcification to deep animals. Additionally, larger mobile animals may travel from site to site taking advantage of local chemosynthetic productivity, and congregating near topographic features such as seamounts.. This expedition will work to better understand how these habitats influence the animal life around it.

ROV SuBastian will explore the deep habitat collecting high resolution ocean chemistry measurements while performing video transects and obtaining sediment, rock, and animal samples. Along with the ROV, a custom ship-towed autonomous vehicle called “The Wire Flyer,” will get high resolution ocean sensing data vertically through the water column. Additionally, DNA and RNA sequencing will be used to compare animal and microbial communities from different habitats and substrates, and quantitative methods will be used to assess microbial activity.

This expedition will likely reveal new habitats, species, and possibly even new biogeochemical pathways. The chemical analyses that will be completed will help to improve our understanding of carbon cycling in the deep ocean, which has important implications not just for the surrounding deep ocean environments, but also for global climate cycling. Biological surveys of these environments will also help to resolve the relative similarity of fauna along a continuum of community types from hydrothermal vents to cold seeps and reefs. Finally, the data will provide baselines for these communities and support conservation efforts in Costa Rica that seek to protect these unique systems from the impacts of increasing human activities.

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