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Seafloor Ecology Expedition 2019

Jim Barry (right) and Senior Research Technician Chris Lovera (left) prepare the Benthic Respirometry System (BRS) for deployment at Sur Ridge.

Seafloor Ecology Expedition 2019

Bubblegum coral and elongate goiter sponge at Sur Ridge

MBARI Expedition #462

Expedition goal: Our cruise off the central California coast has several objectives related to three research themes in deep-sea ecology: 1) study the sponge and coral communities at Sur Ridge, 2) revisit a corn stover sunk to 3,200 meters depth in 2009 and sample the colonizing communities, and 3) begin a wood-fall experiment to see how species colonize these ephemeral sources in the deep sea.

Expedition dates: April 19 – April 24, 2019

Ship: R/V Western Flyer

Research technology:  ROV Doc Ricketts, benthic respirometer systemdeep particle image velocimetry (DeepPIV)

Expedition chief scientist: Jim Barry

Our primary goals focus on studies of deep-sea coral and sponge communities at Sur Ridge, a seamount about 60 kilometers (40 miles) off the coast of Monterey which rises to within 800-1,400 meters (2,600-4,600 feet) of the sea surface. This rocky ridge is rich with beautiful coral and sponge gardens containing centuries-old corals towering two-to-three meters tall like small oak trees, sponges one-to-two meters wide that may be even older, as well as a suite of fishes, sea stars, and other species that call these gardens home. The corals and sponges consume suspended plankton and drifting organic particles from currents sweeping over the ridge and must avoid being consumed by predators such as sea slugs and sea stars.

Some of the questions we have about the Sur Ridge sponge and coral communities include: Why are corals and sponges thriving on some parts of the ridge but sparse in others? Is this difference attributed to food and feeding success, predators, and/or competition with their neighbors? How vulnerable are sponges and corals to human activities like climate change, which is now penetrating the depths of the ocean? To begin answering these questions, we plan various activities for each day, such as deploying current meters, sediment traps (funnel shaped traps that capture sinking debris), and other sensors to measure water flow and suspended material that influence the type and abundance of food sweeping over the ridge and past corals.  We will also be measuring respiration rates of sponges and corals using novel sensors and instruments, tagging corals to monitor growth, and measuring rates of predation by sea stars—the deep-sea corals nemesis.

Our second goal is to revisit a large bale of corn stover (essentially a hay bale) that we sunk to a depth of 3,200 meters (10,500 feet) in 2009. We wanted to test one notion for deep-sea carbon sequestration that could mitigate climate warming by storing carbon in the deep-sea rather than allowing it to be emitted to the atmosphere. One idea for deep-sea carbon sequestration is to gather up crop residue (stalks, husks, and other plant material, package it, and sink it in the deep ocean where it will remain for many centuries, rather than allowing it to degrade in the soil and ultimately release COinto the atmosphere. This peculiar idea was suggested years ago and, in preparing for a cruise in 2009, we decided to sink one corn bale to test this notion. We’ll revisit the bale on this cruise to probe it with sensors to measure its rate of decay, giving us some idea of how long its carbon will remain in the deep sea before eventually making its way back to the atmosphere.

Our third goal for the cruise is to initiate an experiment measuring the diversity of animals that colonize wood falls in the deep sea. Logs and other woody debris are carried to the sea by rivers and eventually sink, some to great ocean depths. These wood falls can be a bonanza for some organisms living in the food-poor abyss. Wood-fall organisms—perhaps most notably wood-boring clams, are notorious for their damage to wooden ships, but several related species live in the deep ocean. Some are wood-fall specialists and are found nowhere else, while others are opportunists that use any food source they can find. Our experiment will place small wood falls, 10 x 10 x 45.5 centimeter wood blocks (4 x 4 x 18 inch wood blocks), on the seafloor across an area the size of 10 football fields to see if the assemblage of organisms (clams, snails, crustaceans, worms, etc.) that colonize each block are related to the distance between blocks. This will help us understand if larvae drifting over the seafloor may sense a wood fall or if the colonization process is more random. From this and similar experiments, we are building an understanding of how food limitation and the challenging conditions in the deep sea have shaped the evolution of species and their abilities to exploit ephemeral “food falls” (wood, whales, or anything in between).

About Seafloor Ecology Expedition 2019

April 19 to April 24, 2019 – The Benthic biology and ecology group is heading out to study deep-sea communities in three different environments.