The bottom of the ocean is dark all of the time, is nearly freezing, and the pressure of the water above pushes down with a force of up to 16,452 psi in the deepest part. Without sunlight, much of the food on the seafloor comes from particles of dead plant and animal matter that trickles down from above.
It is difficult to access the deep seafloor, but we are rewarded greatly when we explore this seemingly inhospitable realm. Life in the deep is weird and wonderful. Some fish evolve giant gills to take in as much oxygen as possible. Some have tiny bodies and move slow, minimizing their energy needs since food is so scarce. Entire biological communities rely on chemicals seeping from within the earth (instead of sunlight) to produce energy. Corals, sea stars, sponges, and crabs decorate a sometimes desolate-looking terrain of sediment and rocks.
The landscape of the deep-sea is ever-changing. Canyons have sediment tumbling down their steep walls, volcanoes erupt with flowing lava, and chimneys spew black or white “smoke,” made from the seawater’s interaction with magma beneath the earth’s crust. Gases rise to the surface in bubbles, or are frozen in place by the extreme low temperature and high pressure. Tectonic plates move against each other, causing underwater earthquakes.
It is one of MBARI’s fundamental missions to use and create sophisticated technology to study the deep ocean. We use remotely operated vehicles (ROVs) that are capable of diving to depths of 4,000 meters (about 2.5 miles). These ROVs are fitted with different tools depending on what is being sampled. Researchers studying biology use tools that can gently collect animals from the seafloor, and soft-sediment push-cores to get information about the conditions of the seafloor. Geologists use vibracores to sample deeper into the mud and rocks, and strong containers for collecting lava and other rock. Chemists use laser Raman systems to study the compositions of gases emanating from the seafloor, and specialized tools for imaging bubbles.
We use other technologies to study the seafloor as well. We have autonomous vehicles specializing in high-resolution mapping, enabling us to clearly see different features of the seafloor, and track changes over time. We also use a benthic rover, sediment traps, and deep-sea camera systems. These stay at sea for long stretches of time, and observe the activity of benthic animal communities, and measure how much organic matter reaches the seafloor to support these communities.