Benthic Biology Winter 2013 Expedition
December 11-16, 2013
The benthic biology research group studies the biology and ecology of marine seafloor communities, with a goal of understanding interactions among environmental factors and biological adaptations that influence the survival, growth, and reproduction of organisms, ultimately determining their distribution and abundance. Their recent work emphasizes the influence of climate change on ocean animals and ecosystems. On this cruise, researchers will visit several sites to recover or resample experiments initiated during prior cruises, and to collect animals for ongoing studies. These range from recovering a respiration system measuring the metabolic rates of deep-sea ‘squat lobsters’ (galatheid crabs), to sampling an experiment to determine the effects of deep-sea urchins on other seafloor animals, to revisiting a large shipping container found on the seafloor in 2004, which had fallen from a ship during a storm.
Are deep-sea animals more sensitive to climate change and ocean acidification than shallow water animals? Could crop debris left in fields after a harvest be packaged and sunk to the deep waters of the ocean to help reduce the effects of carbon dioxide emissions to the atmosphere? What happens to the estimated 10,000 shipping containers per year that are lost over the side of container ships and sink to the deep sea floor? Do they affect the animal communities living on the seabed? Do deep-sea urchins plowing through the muddy bottom in the deep waters along the continental margin affect the macrofauna in the mud—the small worms, molluscs, and crustaceans that comprise the prey for many megafaunal animals? These are some of the research questions the benthic biology group is addressing on the December cruise on the Western Flyer as they continue studies initiated over the past several years.
Researchers’ top priority for the cruise is to measure the sensitivity of deep-sea crabs to ocean acidification and low oxygen levels, two consequences of fossil fuel emissions to the atmosphere—it is amazing to think emissions are affecting animals at the bottom of the sea. The benthic respiration system was deployed over the side of the ship during a cruise in October. As it slowly sank, the ROV Doc Ricketts was launched and followed the respiration system down to the bottom. The ROV pilots then used a suction sampler to slurp up small galatheid crabs, which were placed gently into the eight respiration chambers. Over the past six weeks, this deep-sea robot has automatically measured the respiration rates of the crabs under normal deep-sea conditions, as well as under more acidic, or lower oxygen conditions, or both. When the ship arrives on the site, now scheduled for the 12th of December, we will send an acoustic signal to the respiration system, commanding it to release the anchor weights that were used to sink it to the bottom. Once released, it will float slowly back to the surface. The transit requires about two and one-half hours. Once it reaches the surface, a radio beacon will be automatically activated and we will hear the transmission aboard the ship. The crew will attach a grappling line to the respiration system, then hoist it aboard. Ultimately results from these deep-sea studies at 3,200 meters depth will be compared to similar studies with shallower living crabs to increase our understanding of how sensitive these animals are to changing ocean conditions.
In 2006, researchers sank a large bale of corn stover—what remains from a corn plant when the cobs are harvested—into 3,200 meters water depth about 50 nautical miles from Moss Landing. They are returning to the bale to determine how rapidly it is decaying. If the rates are extremely slow, they might be able to consider sinking crop residue like this to the deep-sea to help offset rising carbon dioxide levels in the atmosphere. This idea sounds pretty wild, but we need to consider, and evaluate carefully, all available options to cope with climate change.
What happens to lost shipping containers? During a fierce storm in February 2004, 24 containers fell off the Chinese M/V Med Taipei container ship while it was transiting the central California coast. Just a few months later, one of these containers was found at a depth of 1,281 meters (4,202 feet) off Monterey during an ROV dive. Researchers from the Monterey Bay National Marine Sanctuary and MBARI have been studying the container and the surrounding seabed to follow changes in animal communities and potential contaminants to assess the effects of the container on deep-sea communities. They will revisit the container during this cruise to resample the biological communities on and around the container. One container may not be that important, but what about the accumulation of containers on the seafloor if roughly 10,000 are lost from ships each year?
Finally, the ROV Doc Ricketts will dive on sites at 200 and 600 meters depths where a deep-sea ‘caging’ experiment is underway to measure the effects that deep-sea urchin have on other seafloor animals. Caging experiments are a mainstay of ecology for intertidal and terrestrial studies, but are rarely attempted in the deep-sea. Three of six cages (two meters width by two meters length and 30 centimeters high) included approximately 15 urchins, and three cages had no urchins. The team will use the ROV to move the cages, then collect all of the urchins and any other megafauna using a suction sampler, as well as numerous sediment cores from beneath each cage. Once the samples are on board, the science team will sieve the sediment to separate the little animals—the macrofaunal worms, and the meiofauna, the microscopic animals. In the lab, these samples will be analyzed and comparisons will be made of the fauna sampled in cages with or without urchins to determine how important urchins are in controlling the distribution and abundance of the smaller animal assemblage.