26 June, 2000
26 June 2000
My Name Is Mud
When Dr. Lisa Clough steps on a research ship, word quickly gets around that the “Mud Lady” is on board. Dr. Clough relishes playing in the muck that covers the bottom of the ocean and houses the critters that draw her interest. Her enthusiasm is contagious and a dredge or box core will get the deck crew looking through the mud - usually on the deck, but sometimes through mud covered eyes or glasses. Once the samples are collected and set aside, all’s fair in mud and war with any of the material left over. The key strategy in a mud fight according to Lisa is to go for the sunglasses - by the time they’ve cleared enough to see, you’ve gained the upper hand(fuls of mud)!
See, research can be fun! Once the mud has been hosed off people and the deck with fire hoses, what does Dr. Clough find in the samples set aside before the mayhem? In a word “worms”, in several words “head-down deposit-feeding capitellid polychaete worms”. Polychaetes are segmented marine worms in the same phylum, Annelida, as earthworms. This type of polychaete feeds on materials deposited in the seafloor with its head down in the sediments and its posterior end near the surface of the sediments. It takes some looking to find them, as they are only 5cm long and 2mm in diameter. As Lisa puts it, “They look like red threads”.
What is so special about these parcticular worms? They live in an environment that would kill most living organisms other than certain types of bacteria. Not only do they live in an environment with very limited oxygen availability, the sediment layers they are feeding in are very high in sulfides which themselves are often fatal to animals that require oxygen for cellular respiration. The type of sulfides the worms are exposed to bind with hemoglobin and block processes in the mitochondria. Hemoglobin is found in the worm’s blood and binds with oxygen to carry it through the body much as it does in humans. When the oxygen reaches mitochondria in the cells, it is used to help break down carbohydrates in the process of cellular respiration, resulting in the production of energy the body can use (in the form of ATP). Sulfides can block both these processes, killing most animals. Many people are familiar with the presence of sulfides in sediments. If you have ever stepped in mud that generated a smell of rotten eggs, you’ve released sulfides trapped in the sediments. In high concentrations, these chemicals can quickly overpower your sense receptors to them and then overpower you!
Other organisms live in areas of high sulfide concentrations, but these are near hydrothermal vents near spreading zones, and they have symbiotic bacteria living within them. The famous giant tubeworms (Riftia) of vent communities survive because they have specialized hemoglobin and bacteria living within them that process the potentially toxic sulfides and generate energy for themselves and the tubeworms. The worms Dr. Clough studies don’t appear to have any such assistance. They have evolved chemical processes and behaviors that allow them to survive, and thrive, in this typically lethal environment. In doing so, they are reclaiming some of the energy not claimed in this habitat by the sulfur reducing bacteria that also live in those sediments.
In addition to the worms she studies in hypoxic (low oxygen) and anoxic (no oxygen) environments, the Mud Lady has two other research interests. One of these is the ecology of man-made environments such as the wetland habitats mining companies create in her area to replace habitats altered by their operations. Dr. Clough can compare their community and energetic structure with those of natural wetlands of the area, and it gives her hands-on activities for her undergraduate students at East Carolina University in Greenville, North Carolina. Lisa is an Assistant Professor in the Department of Biology at ECU. She started there as a post-doctoral student after completing her PhD at SUNY at Stony Brook.
Her other research interest is the Arctic, and this is where USCGC Healy comes in. The ship will allow her and other researchers to fill in gaps in our understanding of the processes that take place during the year in the Arctic. Until the HEALY was built, U.S. researchers couldn’t get very far into arctic waters for most of the year. This limited access meant they couldn’t study what happens in the ecosystem for nearly ten months out of the year. Now Dr. Clough can try to answer such questions as “What is the role of ice algae in the Arctic?” and “What happens to Arctic marine systems during the period when the sun isn’t shining during the months-long arctic night of northern polar winter?” USCGC Healy will be the tool that the Mud Lady and others can use to reach those environments in order to unlock the secrets hiding under the icepack of the seas of the Arctic Ocean.
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