Deep Mud Diaries: Exploring Seafloor Biodiversity on the Aleutian Arc Expedition
A USGS-led expedition in the Aleutian Arc off Alaska will provide critical information on energy resources, underwater earthquakes and other hazards, seafloor habitats, and biological resources, including key fisheries, as well as potential seabed minerals. Scientists aboard the expedition are studying the small but critical critters that make their home in the seafloor mud.
When many people think of the seafloor, they conjure up images of large corals, alien looking fish, or even hydrothermal vents that often populate the media. But most of the deep seafloor is covered by large expanses of soft sediments. Mud is everywhere! These sediments are home to diverse communities of tiny animals that provide an important link in transferring energy between the marine snow that rains down from surface waters to larger animals feeding at the seafloor and in the water column.
Although small in size (macro-infauna = 0.3 – 1mm), the communities in the mud are typically comprised of a variety of crustaceans (amphipods, isopods, cumaceans), worms (polychaetes), clams (bivalves), snails (gastropods), and other rarer taxa (e.g., brittle stars, sea cucumbers, other molluscs). The composition of the communities can provide clues about the physical and chemical environment they inhabit and typically differ among larger visible habitats, such as those near deep-sea corals or cold seeps.
On the Aleutian Arc, little is known about the macro-infaunal communities occurring within the 300 – 2,500-meter depth range. In addition to broad expanses of mud, this region is also home to deep-sea coral communities, cold seeps, and possible hydrothermal vents, with sediment infauna from these habitats likely representing a large portion of the regional biodiversity. To investigate these communities, we sample sediments using push cores from the U.S. Navy's human occupied vehicle (HOV) Alvin in targeted areas, such as adjacent to deep-sea corals. These sediment cores will be used to describe the community composition, with many taxa likely new to science, along with their environmental habitat, including grain size and food availability. This information will enable scientists to better understand the overall distribution of species across the region, their comparability to similar habitats worldwide, and the role these communities play in local ecosystem functioning, all of which help support the health of the ocean.
