Have you always thought of the underwater world as a serene and quiet place, occasionally punctuated by a few low whale calls and crashing waves? Well, actually it is a cacophony of diverse noises made by all kinds of animals (big and small), wave and tidal action, seismic activity and human use! We know about the role of acoustics for some mammals and fishes, but the sounds produced in deep-sea ecosystems remain a mystery - one that we hope to solve with your support!
Sound is a potentially rich source of sensory information for all marine organisms. The underwater soundscape is becoming known as an integral component of the sensory environment for a variety of fish and invertebrates. A multitude of shallow water species (not just mammals!), produce sounds during activities such as movement and feeding, or for the purpose of defense, reproduction or communication. Recently, sound associated with specific habitats (such as coral reefs and oyster reefs) has garnered interest as a larval orientation and settlement cue for fish and invertebrates. In the vast abyss of the deep-sea, where light cannot penetrate and productive habitats are scarce, sound detection could be especially adaptive as a navigation, habitat selection or recruitment aid, but this has yet to be studied.
“Cold seeps” are deep-sea habitats where hydrocarbon-rich fluid seeps out of the seabed, and, much like at hydrothermal vents, the energy-rich fluids fuel an abundant community of unique organisms in an otherwise inhospitable environment. These ecosystems are called “chemosynthetic” because they derive their energy from the chemical-rich fluids rather than the sun that supports photosynthetic ecosystems.
It is probable that the inhabitants of deep-sea vents and cold seeps produce and utilize sound in their activities, and that these highly productive communities have a unique bio-physical sound signature that could play a role in their ecology, but we have yet to “listen” to these habitats. This project is seeking funding to collect the first-ever sound recordings in these locations during research expeditions planned for summer 2012 and 2013 to cold seeps in the Gulf of Mexico and Western Atlantic Ocean. We also hope that we will be able to use the equipment purchased through this project to record the sounds of other deep-sea habitats such as hydrothermal vents!
Despite covering 95% of our planet, and regulating its temperature, weather patterns, and supporting much of its life, less than 5% of the ocean has been explored. Much of what is yet to be explored is in the deep ocean, and deep-sea scientists are continuously making exciting discoveries. Present methods used to obtain information about the deep-sea-floor ecosystem include cameras, trawls, corers, manned submersibles and ROVs, and sensors, but deep-sea researchers have rarely incorporated passive acoustic methods, particularly to monitor productive chemosynthetic habitats such as cold seeps. The addition of acoustic recording to seep moorings will provide the first ever characterization of the ambient soundscape of cold seeps, potentially transforming our understanding of process and pattern in these deep-sea environments. Submersibles and cameras are relatively intrusive to the deep-sea ecosystem and their noise and lights likely interfere with our ability to detect natural organism activity; sound recordings are done passively over long time scales, so acoustic data will certainly add to our understanding of what is going on down there!
In addition to geophysical sounds such as methane bubbling, and unique topographical features interacting with hydrodynamic flow, the biological community present is predicted to contribute to a seep soundscape distinct from surrounding environs. Planned submersible dives will allow a comparison of the sea life at the different sites where acoustic recording takes place and will thus enable the identification of biological influences on acoustic patterns.
Recording deep sea sounds requires specialized acoustic equipment in housing built to withstand the extreme pressures of the deep. Without $14,000 to construct the instrument, this work will not be possible and we will remain deaf to the deep-sea seep sounds! The current opportunity is unique in that I will have a chance to deploy the underwater hydrophone-recording system at deep-sea seep sites in the Gulf of Mexico and Western Atlantic as part of an ongoing deep-sea study; the costs of the single instrument pale in comparison to the costs of reaching the deep sea, but we have no mechanism to acquire the additional funds. This is a tremendous chance to collect potentially transformative exploratory data by leveraging the moorings and ship-time already in motion – an opportunity that does not come along often! Without the ability to add this project to an already financed study, finding the funds and opportunity to record sounds in chemosynthetic environments may be a long way off.
If this project is funded, we will have the opportunity to record never-heard-before sounds! Acoustic monitoring of deep-sea sites offers an exciting and novel method by which to gain high temporal resolution data that could reveal unanticipated cycles in seep activity (biological, physical and geological), which are not detectable with traditional deep-sea sampling methods. The use of passive acoustic technology in these systems has applications not only for biologists, but for geophysicists and climate scientists too, who want to measure the amount and variability of methane seepage from the seafloor.
Ashlee Lillis is a Ph.D. candidate in Marine Science at North Carolina State University, where she is studying the effects of underwater sounds on the behaviour and settlement of larval invertebrates. If this project is funded, she will use her expertise in characterizing shallow-water soundscapes and apply it to the study of deep-sea seep acoustics. Ashlee holds a Masters degree in Biology from Memorial University of Newfoundland and a Bachelors degree in Oceanography & Biology from the University of British Columbia. At NC State she works with Drs. David Eggleston, a marine ecologist, and Del Bohnenstiehl, a geophysicist, to integrate ecological processes and the physics of sound.
To carry out the research described in this proposal, Ashlee will join a team of top deep-sea scientists, marine ecologists and physical oceanographers for their 2012 and 2013 research expeditions. Along with NC State University researchers, the principal investigators involved with this project include Dr. Cindy Van Dover, Director of the Duke University Marine Lab who has been making submersible dives to the deep-sea for nearly 30 years, and Dr. Craig Young, Director of the Oregon Institute of Marine Biology and an expert in deep-sea larval biology.
Thanks to all of you that have pledged to our project!
There is still a long way to go and not many days left to get this science funded. Please help with our final push by promoting the project to your friends and colleagues so that this study can happen and you can receive your exciting reward!