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Staaterman E.,University of Miami | Rice A.N.,Cornell University | Mann D.A.,Loggerhead Instruments | Paris C.B.,University of Miami
Coral Reefs | Year: 2013

Underwater soundscapes vary due to the abiotic and biological components of the habitat. We quantitatively characterized the acoustic environments of two coral reef habitats, one in the Tropical Eastern Pacific (Panama) and one in the Caribbean (Florida Keys), over 2-day recording durations in July 2011. We examined the frequency distribution, temporal variability, and biological patterns of sound production and found clear differences. The Pacific reef exhibited clear biological patterns and high temporal variability, such as the onset of snapping shrimp noise at night, as well as a 400-Hz daytime band likely produced by damselfish. In contrast, the Caribbean reef had high sound levels in the lowest frequencies, but lacked clear temporal patterns. We suggest that acoustic measures are an important element to include in reef monitoring programs, as the acoustic environment plays an important role in the ecology of reef organisms at multiple life-history stages. © 2013 Springer-Verlag Berlin Heidelberg. Source

Randall Hughes A.,Northeastern University | Mann D.A.,Loggerhead Instruments | Kimbro D.L.,Northeastern University
Proceedings of the Royal Society B: Biological Sciences | Year: 2014

The risk of predation can have large effects on ecological communities via changes in prey behaviour, morphology and reproduction. Although prey can use a variety of sensory signals to detect predation risk, relatively little is known regarding the effects of predator acoustic cues on prey foraging behaviour. Here we show that an ecologically important marine crab species can detect sound across a range of frequencies, probably in response to particle acceleration. Further, crabs suppress their resource consumption in the presence of experimental acoustic stimuli from multiple predatory fish species, and the sign and strength of this response is similar to that elicited by water-borne chemical cues. When acoustic and chemical cues were combined, consumption differed from expectations based on independent cue effects, suggesting redundancies among cue types. These results highlight that predator acoustic cues may influence prey behaviour across a range of vertebrate and invertebrate taxa, with the potential for cascading effects on resource abundance. © 2014 The Authors Published by the Royal Society. All rights reserved. Source

Staaterman E.,University of Miami | Paris C.B.,University of Miami | DeFerrari H.A.,University of Miami | Mann D.A.,Loggerhead Instruments | And 2 more authors.
Marine Ecology Progress Series | Year: 2014

Soundscape ecology is the study of the acoustic characteristics of habitats, and aims to discern contributions from biological and non-biological sound sources. Acoustic communication and orientation are important for both marine and terrestrial organisms, which underscores the need to identify salient cues within soundscapes. Here, we investigated temporal patterns in coral reef soundscapes, which is necessary to further understand the role of acoustic signals during larval settlement. We used 14 mo simultaneous acoustic recordings from 2 reefs, located 5 km apart in the Florida Keys, USA to describe temporal variability in the acoustic environment on scales of hours to months. We also used weather data from a nearby NOAA buoy to examine the influence of environmental variables on soundscape characteristics. We found that high acoustic frequencies typically varied on daily cycles, while low frequencies were primarily driven by lunar cycles. Some of the daily and lunar cycles in the acoustic data were explained by environmental conditions, but much of the temporal variability was caused by biological sound sources. The complexity of the soundscape had strong lunar periodicity at one reef, while it had a strong diurnal period at the other reef. At both reefs, the highest sound levels (∼130 dB re: 1 μPa) occurred during new moons of the wet season, when many larval organisms settle on the reefs. This study represents an important example of recently-developed soundscape ecology tools that can be applied to any ecosystem, and the patterns uncovered here provide valuable insights into natural acoustic phenomena that occur in these highly diverse, yet highly threatened ecosystems. © Inter-Research 2014. Source

News Article | August 29, 2016
Site: http://www.rdmag.com/rss-feeds/all/rss.xml/all

A new study from the Woods Hole Oceanographic Institution (WHOI) will help researchers understand the ways that marine animal larvae use sound as a cue to settle on coral reefs. The study, published on August 23rd in the online journal Scientific Reports, has determined that sounds created by adult fish and invertebrates may not travel far enough for larvae —which hatch in open ocean—to hear them, meaning that the larvae might rely on other means to home in on a reef system. “To keep a reef healthy, you need a constant supply of new larvae to repopulate animals that die off,” said Max Kaplan, the lead author of the paper and a graduate student in the MIT/WHOI Joint Program in Oceanography. “How larvae find reefs has been a big question, though. We think sound may play a role in attracting them, but exactly how far away they can sense those sounds has not yet been accurately measured.” To address that problem, Kaplan and his PhD adviser, WHOI Associate Scientist Aran Mooney, a co-author on the paper, traveled to the Hawaiian island of Maui to make painstaking acoustic measurements of a healthy reef system. The pair focused their efforts on recording two different components of sound—pressure waves (the element of sound that pushes on a human eardrum), and particle motion (the physical vibration of the water column as a sound wave travels through it). The latter, Kaplan explained, is how the majority of fish and marine species detect sound, yet no previous studies have focused on recording it. “Think of it like being at a loud concert—if you’re standing next to a huge speaker, you effectively feel the sound as it vibrates your skin,” Kaplan said. “Fish and invertebrates sense sound in a similar way.” Species like squid, octopus, and shrimp, for example, can detect vibrations through nerves embedded in their flesh. Similarly, adult fish sense them through the motion of tiny bone-like structures called otoliths inside their skulls. Although researchers in the past have detected reef sounds from many kilometers away, Kaplan says that most of those studies rely on a hydrophone, an underwater microphone, which can only detect pressure waves. In their Maui study, however, the researchers recorded particle motion as well, using a sensitive accelerometer alongside a hydrophone. The data the accelerometer provides is directly relevant to how marine organisms sense sound, said Mooney. “Particle motion is really the relevant cue for marine animals,” Mooney said. “When we’re measuring pressure, we’re measuring the wrong thing—it only gives a ballpark sense of what marine species hear. We think studying particle motion is a big step to figuring out how larvae find their way to a reef.” Using an accelerometer to measure that motion, however, comes with a few challenges, said David Mann, President of Loggerhead Instruments, which designs small accelerometers for marine research. “To sense particle motion, an accelerometer has to be able to move along with the water as the sound passes by. It can’t be mounted rigidly on frame or on the bottom, but it also can’t be allowed to drift loosely with the currents. It’s a lot harder to use than a hydrophone.” Kaplan worked with Canadian company GeoSpectrum Technologies to fine-tune existing accelerometers for use in the study, then deployed them at multiple sites around the reef. Over three days, he and Mooney measured sound levels at dawn and mid-morning, placing the sensors at distances ranging from zero to 1500 meters away from the reef itself. In doing so, the pair found that particle motion was much lower than expected, dropping rapidly below levels that most marine species can sense—even just a few meters away from the reef. ”It’s possible that larvae are still able to use chemical signals from other animals to locate the reef, or maybe can read the currents to move towards shore,” Kaplan said, “but based on this data, it seems unlikely that they’d be able to use sound to find the reef. That was a surprise to us.” Once larvae do locate a reef, Kaplan thinks sound may play an important role in finding a suitable location to settle down. Many species living on reef systems are extremely localized, he notes. For example, some damselfish species live their entire adult lives within one square meter, so finding the best possible location is key to their survival. “In cases like that, sensing sound on order of meters would make a big difference,” Kaplan said. “If you hear sounds of your species instead of predators, you might be more inclined to settle in a specific spot.” The researchers’s findings might also be useful for reef conservation efforts. Past studies have shown that larvae are attracted to reef sounds when played through an underwater loudspeaker, so Kaplan thinks that playing back recorded biological sounds at high volumes could be used to steer larvae to damaged reef areas. “You’d have to boost sound levels by quite a bit to get the response you want, but it could be one solution,” said Kaplan. “If we can figure out the hearing threshold of each species’ ability to sense particle motion, we might be able to amplify that motion to make it audible to them at a distance.” Kaplan notes that the Maui study only covers one shallow reef, so further study is needed to gain a full understanding of how sound propagates from other types of reef systems. “Recording particle motion in the field hasn’t really been done before,” said Kaplan, “but now that we’ve worked out these methods, we can start to expand our work.” This research was supported by the Woods Hole Oceanographic Institution Ocean Ventures Fund, the PADI Foundation, and the Woods Hole Oceanographic Institution Access To The Sea program.

The current challenge in the study of larval fish navigation is to sample signals as they are perceived by fish larvae in the pelagic environment. To meet this challenge, the PI?s plan to build upon novel bio-acoustic technology and proof of concept methods for monitoring larval behavior in situ, to develop an integrated realTime Larval Environment and Ocean Signal Tracking (T-LEOST) system.

Almost nothing is known about the orientation of larvae earlier in the larval phase, far offshore, or at night. It is now clear that behavior can play a crucial role in pelagic larval dispersal, but the biological processes involved in larval dispersal remain largely unknown. The sequence of cues that dispersing larvae use to determine their swimming direction (orientation) and how they vary spatially is entirely subject to speculation. The orientation of marine larvae is a central issue in understanding and modeling the pelagic stage of coastal organisms. The proposed research will supply important pieces of the pelagic orientation puzzle, that will lead to a better understanding of larval dispersal and population connectivity, and an improved ability to model them. The project will also serve as an observing system platform that will be vital in understanding larval use of a full suite of sensory cues, such as polarized light, electroreception of water movement, and other (magnetic, thermal). One of the over-arching benefits of our proposed system is the capacity to provide existing ocean observing systems with recording of environmental signals meaningful to the successful recruitment of benthic species.

Broader Impacts:

The projects broader impact lies in its potential to contribute meaningfully to our understanding of the mechanisms underlying dispersal in marine organisms. Personnel will produce an educational video, mentor high-school and college students and provide videos of swimming larval fish in public forums.

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