Update from David Needham and Charlotte Eckmann:

The work of MBARI’s Marine Microbial Ecology Group included these experiments:

• One was designed to study the influence of the high pressure and cold temperatures on surface organisms that may find themselves stuck in the deep sea for long periods of time (think: “I’ve fallen and I can’t get up, but what are the implications if I do?”) Such experiments have important implications because deep-sea currents connect the polar regions of the oceans and, in these regions, ocean circulation is such that it gives free rides to the cold, sunless deep ocean to large magnitudes of non-motile algae. What happens if algae take this “conveyer belt” and come up on the other side (think: Elon Musk’s hyperloop, but colder, global, and way slower). On this cruise, we collected the experiments and brought them back to the surface for resuscitation (or not!)
• A second experiment collected sediments which had been “spiked” with algae which had been grown with substrates (stable isotope labeled) that would allow detection of their incorporation into other organisms, mostly bacteria, which degrade them in the deep-sea sediments. It is valuable to do these experiments at the same conditions as the microbes typically live, which is at a pressure over 300 times that at the surface!

Additionally, the team took several profiles of the ocean waters and deep-sea sediments to collect nucleic acids from the microorganisms to contextualize and characterize the microbial diversity present and how it compares with past and future collections.

The Stanford research team studies enigmatic microbes that inhabit the deep ocean and deep-ocean sediments and their interactions with the surrounding chemical environment. On this cruise, Professor Anne Dekas and Nicolette Meyer studied a microbial process called nitrogen fixation in deep-sea sediments. Nitrogen fixation is a microbially mediated process that converts ubiquitous, but generally inert, nitrogen forms into forms of nitrogen accessible to cellular processes and other organisms. Only certain microorganisms can perform this function, and when the ratio of usable forms of carbon to nitrogen is tilted towards carbon in the deep sea, beware of nitrogen fixation! While it’s known that deep-sea nitrogen fixation is occurring, the rates, environmental controls, and exact microbes responsible for this process in deep seafloor sediments are still a mystery.

Like the MBARI team, CalTech researcher Sujung Lim was mainly retrieving past cultivation experiments from the seafloor. Over 10 years ago, a dead whale (named “Francisco” by the research team) was set out on the deep seafloor to study the successional patterns involved in its degradation. The whale is nothing but bones now, though its effects on the seafloor environment can still be detected in surrounding sediments. The large influx of organic matter from the whale has long-reaching effects; for example, the accumulation of crustacean scavengers whose carapaces could supply can supply nutrients to the otherwise relatively nutrient-poor seafloor. We still don’t understand the microbial community structure that helps to mediate the decomposition of chitin in sediments lacking oxygen. To address this, Sujung retrieved experiments which aim to isolate and culture microbes that degrade chitin and its related breakdown products.