Food Paradox Answer Shows How Ocean Life Survives

Food Paradox Answer Shows How Ocean Life Survives

Acoustic tools reveal hotspots of ocean life in scattered places

Media Contact:
Larry Frum
AIP Media

SEATTLE, December 1, 2021 – Ocean predators cannot survive on average concentrations of food found in the water. Instead, they survive by exploiting small patches of food-rich areas peppered throughout the world’s waterways.

During the 181st Meeting of the Acoustical Society of America, which will be held Nov. 29 to Dec. 3, Kelly Benoit-Bird, from the Monterey Bay Aquarium Research Institute, will discuss how sonar or active acoustics can be used to interpret and indicate biological hotspots of ocean life. The talk, “A Sound Resolution to the Food Paradox in the Sea,” will take place Wednesday, Dec. 1, at 4:05 p.m. Eastern U.S.

Using active acoustics, where a sound pulse is created and resulting echoes are interpreted, the researchers found the ocean is widely populated with narrow hotspots of activity. Traditionally, these hotspots are missed with conventional sampling tools, but locating them can provide dynamic layered maps of ocean life.

“We’re using systems much like those used to find the depth of the ocean, but instead of interpreting echoes from the seafloor, we’re using more sensitive systems that allow us to map layers of life in the water,” said Benoit-Bird. “What we’ve found is that animals of all different sizes, from millimeter long plankton to large predators, are unevenly distributed, and this variation is really important to how life in the ocean functions.”

The findings signify ocean food and biota as patchy, varying with depth and location, suggesting animals must find and exploit small scale aggregations of resources.

The Lasker food paradox proposed in the 1970s found laboratory animals fed the average concentration of ocean food did not survive, but ocean-dwelling animals in the wild did. The paradox is reconciled by Benoit-Bird’s findings, demonstrating animals do not survive on average food concentrations but are well-adapted to locating and capitalizing on patches of resources, and reducing their total energy expenditure to hunt.
“For example, if a bucket’s worth of popcorn was spread out evenly throughout the volume of a room, and you had to fly around to capture each kernel, you would spend a lot of energy searching and it would be hard to get enough to be full,” Benoit-Bird said. “If instead, the popcorn was all grouped together, the popcorn would be a much more satisfying snack. The amount of popcorn is the same but changing how it is grouped determines whether you end up with a full belly.

“Acoustic tools provide the high spatial resolution and long duration sampling to explore the processes that drive organismal interactions in the ocean. We must understand not only how many animals are in the ocean, but how they are distributed, if we are to effectively manage our living marine resources.”

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The Acoustical Society of America (ASA) is the premier international scientific society in acoustics devoted to the science and technology of sound. Its 7,000 members worldwide represent a broad spectrum of the study of acoustics. ASA publications include The Journal of the Acoustical Society of America (the world’s leading journal on acoustics), JASA Express Letters, Proceedings of Meetings on Acoustics, Acoustics Today magazine, books, and standards on acoustics. The society also holds two major scientific meetings each year. See

2pAO6 – Listening to Hydrothermal Vents

Brendan Smith –
Dr. David Barclay –
Dalhousie University
Department of Oceanography
Life Sciences Centre, 1355 Oxford St.
PO Box 15000
Halifax, NS
B3H 4R2, Canada

Popular version of 2pAO6 – Passive acoustic monitoring of hydrothermal vents at the endeavour hydrothermal vent field
Presented Tuesday morning, November 30, 2021
181st ASA Meeting
Click here to read the abstract

Long-term monitoring of hydrothermal vents is challenging due to their high temperature and caustic fluid properties. Passive acoustics provides a sustained vent monitoring method from a safe distance. Long-term acoustic records and hydrophone arrays may be used to investigate the sound producing mechanisms of hydrothermal vents. The initial results from an analysis of 6-months of single hydrophone acoustic data collected at the Main Endeavour Hydrothermal Vent field in the North-East Pacific, and a short-term array deployment at the same location demonstrate features of the vent’s signature.
The monitoring hydrophone, operated by Ocean Networks Canada (ONC) is within 10 meters of a black smoker hydrothermal vent. During a servicing cruise in the fall of 2021, ONC deployed the Deep Acoustic Lander (DAL), an autonomous acoustic recorder carrying a four-channel hydrophone array, shown in Fig. 1. The difference in received signals across the array can be exploited to identify hydrothermal vent generated noise and separate it from possible interferences, such as flow noise, wind generated wave noise, and ship noise.


The Deep Acoustic Lander being deployed by Ocean Networks Canada using an ROV near a black smoker hydrothermal vent [Credit: Ocean Networks Canada]”
Despite the vigorous, high-temperature flow seen from black smoker chimneys, they do not produce loud acoustic signals relative to the ocean’s background noise. However, several acoustic source mechanisms have been proposed to generate both tonal and broadband sounds (Lighthill, 1952; Little, 1988; Crone et al., 2006).

Fig. 2 compares audio spectra and vertical coherence from the DAL hydrophone array deployed at an initial standoff distance of 200 m, then subsequently repositioned to within 3 m from the vent outlet. Increased broadband infrasonic (1 – 10 Hz) and low frequency (100 – 200 Hz) energy is observed when the sensor is positioned near the vent, and tonal components at 4, 5, 7, 8, and 9 Hz are observed in the spectra. A reduction in coherence in the infrasonic band indicates flow noise while the coherent tonals may be generated by the vibrating vent structure.

Caption: “Figure 2: (a) Acoustic power spectra, (b) real and (c) imaginary vertical coherence <3m (solid) and >200m (dashed) from vent”
The outflow rate and temperature of hydrothermal vent fluid can modulate due to tidal variations in overburden pressure, causing a correlated variation in sound level (Barreyre & Sohn, 2016; Xu & Di Iorio, 2012; Larson et al., 2007; Crone & Wilcock, 2005; Crone et al., 2006). Tidal-period variations in sound level over 6 months of audio data were observed by carrying out a spectral analysis of power spectral density levels, shown in Fig. 3. Variations in sound level with the diurnal and semidiurnal tidal components are seen at infrasonic (1 – 10 Hz) and low (100 – 400 Hz) frequencies. The semidiurnal variability below 10 Hz is attributed to flow noise (Fig. 2) due to either tidal currents or vent plume entrainment. Variability between 100-400 Hz, above the flow noise regime, is generated by vent plume outflow and mixing.


Caption: “Figure 3: Periodic variability of power spectral density”
Combining the long-term records with data recorded on the Deep Acoustic Lander’s hydrophone array will allow the relationships between physical forcing and hydrothermal vent sound generation mechanisms and acoustic signatures to be further determined.

Barreyre, T., and Sohn, R. A. (2016). Poroelastic response of mid-ocean ridge hydrothermal systems to ocean tidal loading: Implications for shallow permeability structure. Geophys. Res. Lett., 43, 1660-1668, doi:10.1002/2015GL066479
Crone, T. J., and Wilcock, W. S. D. (2005). Modeling the effects of tidal loading on mid-ocean ridge hydrothermal systems. Geochem. Geophys. Geosyst., 6, Q07001, doi:10.1029/2004GC00905
Crone, T. J., Wilcock, W. S. D., Barclay, A. H., Parsons, J. D. (2006). The sound generated by mid-ocean ridge black smoker hydrothermal vents. PLoS ONE, 1(1): e133, doi:10.1371/journal.pone.0000133
Larson, B. I., Olson, E. J., Lilley, M.D. (2007). In situ measurement of dissolved chloride in high temperature hydrothermal fluids. Geochimica et Cosmochimica Acta, 71, 2510-2523, doi:10.1016/j.gca.2007.02.013
Lighthill, M. J. (1952). On sound generated aerodynamically I. General theory. Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences, 211(1107), 564-587, doi:10.1098/rspa.1952.0060
Little, S. A. (1988). Fluid flow and sound generation at hydrothermal vents. PhD thesis, Massachusetts Institute of Technology and Woods Hole Oceanographic Institution.
Xu, G., and Di Iorio, D. (2012). Deep sea hydrothermal plumes and their interaction with oscillatory flows. Geochem. Geophys. Geosyst., 13, Q0AJ01, doi:10.1029/2012GC004188

2aAO5 – Tracking natural hydrocarbons gas flow over the course of a year

Alexandra M Padilla –
Thomas C Weber –
University of New Hampshire
24 Colovos Road
Durham, NH, 03824

Frank Kinnaman –
David L Valentine –
University of California – Santa Barbara
Webb Hall
Santa Barbara, CA, 93106

Popular version of paper 2aAO5
Presented Wednesday morning, June 9, 2021
180th ASA Meeting, Acoustics in Focus

Researchers have been studying the release of methane, a greenhouse gas, in the form of bubbles from different regions of the ocean’s seafloor for decades to understand its impact on global climate change and ocean acidification (Kessler, 2014). One region, the Coal Oil Point (COP) seep field, is a well-studied natural hydrocarbon (e.g., oil droplets and methane gas bubbles) seep site, known for its prolific hydrocarbon activity (Figure 1; Hornafius et al., 1999). Researchers that have studied the COP seep field have observed both spatial and temporal changes in the gas flow in the area, that has been thought to be linked to external processes such as tides (Boles et al., 2001) and offshore oil production from oil rigs within the seep field (Quigley et al., 1999).

Figure 1. Video of methane gas bubbles rising through the ocean’s water column within the COP seep field.

In recent years, an oil platform within the COP seep field, known as Platform Holly, has become inactive and decommissioned, and there has been a resurgence in natural hydrocarbon seepage activity in the vicinity of the platform based on anecdotal observations. This led a group  from UNH and UCSB to map the hydrocarbon activity in the COP seep field (Padilla et al., 2019), where we were able to identify a large patch of high seepage activity near Platform Holly (Figure 2). The shut-in at Platform Holly provided us with the opportunity to deploy a long-term acoustic monitoring system to study both the spatial and temporal changes in hydrocarbon gas flow in the region and to assess how it is affected by external processes.

Figure 2. a) Acoustic map of natural hydrocarbon activity within the COP seep field (Padilla et al., 2019). b) Zoomed in acoustic map near Platform Holly. c) Image of Platform Holly.

We mounted a split-beam echosounder, at a depth of approximately 8 m  below the sea surface, on one of Platform Holly’s cross beams. The echosounder was programmed to emit an acoustic signal every 10 seconds and has been collecting acoustic data since early September 2019, providing us with more than a year’s worth of acoustic data to process and analyze (Figure 3). The acoustic signal emitted by the echosounder interacts with scatterers in the water column, mostly methane gas bubbles in our case, and measures the target strength of these scatterers. The target strength represents how strong a scatterer scatters sound back towards the echosounder (for more information of acoustics and gas bubbles, see article by Weber, 2016).

Figure 3. Acoustic observations of hydrocarbon activity (ranges between 10-140 m) west of Platform Holly as a function of range from the echosounder and time. Warm and cool colors represent high and low target strength, which correspond, roughly, to high and low seepage activity, respectively.

The acoustic measurements, shown in Figure 3, indicate that there are temporal changes in the location and the target strength of the hydrocarbons in the region; however, it does not tell us how the amount of gas flow of these hydrocarbons is changing with time. Exploiting the split-beam capability of the echosounder, allowed us to track the position of scatterers in the acoustic data, so we can identify and classify different hydrocarbon structure types (Figure 4) and use the appropriate mathematical equations to convert acoustic measurements into gas flow. This will allow us to track changes in gas flow of hydrocarbons near Platform Holly and learn more about how gas flow is affected by external processing, like tides, storms, and earthquakes.

Figure 4. a) Acoustic observations of hydrocarbon activity. b) Acoustic classification map of different hydrocarbon structure types.

4pAO1 – Oceanic Quieting During a Global Pandemic

John P. Ryan –
Monterey Bay Aquarium Research Institute
7700 Sandholdt Road
Moss Landing, CA 95039

John E. Joseph –
Tetyana Margolina –
Department of Oceanography
Naval Postgraduate School
Monterey, CA 93943

Leila T. Hatch –
Stellwagen Bank National Marine Sanctuary, NOS-NOAA
175 Edward Foster Road
Scituate, MA 02066

Andrew DeVogelaere –
Monterey Bay National Marine Sanctuary, NOS-NOAA
99 Pacific Street, Bldg. 455A
Monterey, CA  93940

Lindsey E. Peavey Reeves –
NOAA Office of National Marine Sanctuaries
National Marine Sanctuary Foundation
Silver Spring, MD 20910
Channel Islands National Marine Sanctuary
University of California, Santa Barbara
Santa Barbara, CA  93106

Brandon L. Southall –
Southall Environmental Associates, Inc.
9099 Soquel Drive, Suite 8
Aptos, CA 95003

Simone Baumann-Pickering –
Scripps Institution of Oceanography, UC San Diego
Ritter Hall 200F
La Jolla, CA 92093

Alison K. Stimpert –
Moss Landing Marine Laboratories
Moss Landing, CA, 95039

Popular version of paper 4pAO1
Presented Thursday afternoon, December 10, 2020
179th ASA Meeting, Acoustics Virtually Everywhere

Imagine speaking with only your voice – no technology – and being heard by someone over a hundred kilometers away.  Because sound travels much more powerfully in water than it does in air, great whales can communicate over such vast distances in the ocean.

Whales and other oceanic animals produce and perceive sound for essential life activities – communicating, finding food, navigating, reproducing, and surviving.  This means that we can learn a lot about their underwater lives by recording and analyzing the sounds they produce and hear.  It also means that the noise we introduce into the ocean can cause harm.  Protecting oceanic species and their habitats requires an understanding of the detrimental impacts of our noise and strategies to mitigate these impacts.

There are many sources of anthropogenic noise in the ocean, but the most pervasive and persistent source is that of vessels, notably large commercial ships engaged in global trade.  This worldwide bustling is among the many human activities influenced by the COVID-19 pandemic.  Using sound recordings from the deep sea and information about vessel traffic, we examined oceanic quieting caused by reduced shipping traffic within Monterey Bay National Marine Sanctuary (Figure 1) during this ongoing pandemic.

Oceanic Quieting

Figure 1.  Study context.  Shaded regions represent Monterey Bay National Marine Sanctuary.  The black circle shows the location of a deep-sea (890 m) observatory connected to shore by a cable, through which we recorded sound.  Red and blue lines define nearby shipping lanes.

Our first question was whether the quieting we measured during 2020 could be explained by reduced traffic of large vessels.  We quantified vessel traffic using two independent data sources: (1) economic data representing vessel activity across all California ports, and (2) location data sent from vessels to shore continuously as they transit between ports.  Both of these data sources yielded the same answer: quieting within the sanctuary during January–June 2020 was caused by reduced shipping traffic.  Further, a rebound in noise levels during July 2020 was associated with an increase in vessel traffic.

Our second question was how much quieter 2020 was compared to previous years.  Using the previous two years as a baseline, we found that 2020 was quieter than both previous years during the months of February through June.  Low-frequency noise levels during June 2020, the quietest month having the least shipping activity, were reduced by nearly half compared to June of the previous two years.  For baleen whales that use low-frequency sound to communicate, potential consequences of this quieting include less time exposed to noise-induced interference and stress, and greater distance over which communication can occur.

The effects of this pandemic on oceanic noise will differ from place to place, depending on proximity to hubs of maritime activity, the nature of noise produced by each activity, and the degree and timing of pandemic influence.  These changes are being examined across U.S. National Marine Sanctuaries and all around the world.  The COVID-19 pandemic resulted in an unexpected global experiment in oceanic noise, one that could reveal better ways to care for ocean health and its powerful support of humanity.

Study overview

3pAO1 – Can We Map the Entire Global Ocean Seafloor by 2030?

Larry Mayer –
Center for Coastal and Ocean Mapping
University of New Hampshire
Durham, N.H. 03824

Popular version of paper 3pAO1
Presented Wednesday afternoon, December 09, 2020
179th ASA Meeting, Acoustics Virtually Everywhere

Today it is trivial, with a few clicks of a mouse, to enter an application like Google Earth and explore the complexity of a range of earth processes with extraordinary detail.  While this is true for the brown and green parts of the Earth, it is not the case for the three-quarters of the earth that is blue – for the light waves that are used to image the land cannot penetrate far into ocean waters.  Thus while 100% of the land surface on the earth is mapped in remarkable detail, most of the ocean is unmapped and unexplored.  Knowing seabed depths, (bathymetry) is of vital importance for safety of navigation, predicting storm surge and tsunami inundation, mapping deep-sea habitats and ecosystems, laying cables and pipelines, exploring for resources, understanding ocean currents and their impact on climate change, national security issues and exploring human history as preserved in shipwrecks.

Given the inability of light to penetrate the oceans, for thousands of years, the only technique available to map the deep ocean was a hunk of lead at the end of a rope (lead line).  Unlike light, sound travels far distances in seawater and in the early 1900’s, the development of echo-sounders allowed for a much more rapid and accurate means of measuring ocean depths.  Initially echo-sounders used a single beam of sound that generated a broadly averaged measurement of depth, but in the late 1980s a new type of echo-sounder (multibeam echo-sounder) was developed that simultaneously provided hundreds of high-resolution measurements over a wide swath, revolutionizing our ability to map the seafloor.   By 2018 however, only 9% of the deep ocean seafloor had been mapped with multibeam echo-sounders.

Evolution of mapping systems from lead-line, to singlebeam sonar to multibeam sonar. Credit NOAA

Best depiction of bathymetry offshore southern California from single beam echosounder data

Bathymetry of offshore southern California from multibeam echosounder.  Credit USGS.

Recognizing the poor state of knowledge of ocean depths and the critical role such knowledge plays in understanding and maintaining our planet, the Nippon Foundation challenged the mapping community to produce a complete map of the world ocean seafloor by 2030. The result, “The Nippon Foundation-GEBCO Seabed 2030 Project,” has already increased publicly-available holdings of modern deep-sea mapping data from 9% to 19% in the 2020.  Some of this initial increase came through discovery of existing data; the challenge now is to complete new mapping, an effort estimated to require approximately 200 ship-years (at a cost of $3-5B) using current technologies. While this seems like a large amount to spend on mapping our planet, the reality is that we have spent much more than this mapping other planets (i.e., Mars and the Moon) at much higher resolution. Why not our own planet?

Nippon Foundation – GEBCO Seabed 2030 Project

Meeting the challenge of complete mapping of the global ocean will require innovative new technologies that can increase efficiency, cost-effectiveness and, capabilities.  Autonomous vessels are being developed that can deliver high-resolution mapping systems without the significant cost of crews, and wind-powered autonomous systems, without the cost of crews or fuel.  Along with these new platform technologies innovative new acoustic approaches capable of providing wider swaths and higher resolution are also being developed.  As these new technologies evolve, the aspirational goal of Seabed 2030 may very well become a reality.

22 meter (72 foot) uncrewed Saildrone Surveyor – soon to be launched to autonomously sail the globe collecting deep-sea bathymetric (and other) data.

3pID3 – Hot topics in a warming ocean: How acoustical oceanography can help monitor climate change

Gabriel R. Venegas –

Applied Research Laboratories, The University of Texas at Austin
10000 Burnet Rd
Austin, TX 78758

Popular version of paper 3pID3
Presented Wednesday afternoon, December 4, 2019. 1:45pm-2:05pm
178th ASA Meeting, San Diego, CA

Sound is an effective way to study the ocean by non-invasively and quickly surveying large areas, and acoustical oceanography has lent an extra pair of ears to help scientists monitor climate change. This talk will showcase the work of some of the many acoustical oceanographers in the Acoustical Society of America (ASA) that have made valuable contributions to aid in climate change related monitoring, in the hope of inspiring other members to think of new potential acoustic monitoring applications.

The planet is warming and so are its oceans. This warming causes the seawater to expand and large volumes of ice to break off from glaciers and melt in the ocean, ultimately resulting in sea level rise. An acoustic technique called passive acoustic thermometry1,2 takes the noise created by these calving events at the north and south poles to calculate the speed of sound averaged over path lengths as long as 132 km. Temperature can then be inferred from sound speed using a well-established formula relating the two quantities.

As the glaciers melt, they release tiny compressed air bubbles that make loud popping sounds underwater.3 If these popping sounds can be reasonably characterized at one or many glacial bays, at a safe distance, these sounds can be used to estimate the glacial melt rate.4,5

An increase in ocean temperature also causes methane hydrate, a material in ocean sediments that can store large amounts of methane, to turn from solid to greenhouse gas, which bubbles up from the seafloor and is ultimately released into the atmosphere. The sound of these bubbles has also been exploited to estimate the volume of methane released from hydrates and seeps.6–8

Global CO2 concentrations are higher than they have been over the last 800,000.9 A quarter of this gas is absorbed into the ocean and has caused the what is thought to be the fastest increase in ocean acidity in the last 60 million years.10 An increase in ocean temperature, actually decreases the ocean’s capacity to store CO2, causing it to be released back into the atmosphere. The relationship between ocean acidity and the absorption of sound is well understood. A passive acoustic technique using the sound of wind over the water is being investigated to estimate the absorption and thus ocean acidity.11

Ocean acidity also causes damage to many coastal ecosystems including valuable “blue carbon” stores such as mangroves, salt marshes, and seagrasses, which store 50% of the ocean’s organic carbon.12 The destruction of these carbon stores can also release CO2 back into the atmosphere. An ultrasonic sensor that will improve organic carbon estimates in these ecosystems is currently under development.13 These climate-altering feedback loops can cause rapid and catastrophic consequences for future generations, and should be the responsibility of all scientists, elected officials, and the general public, alike


1K. F. Woolfe, S. Lani, K. G. Sabra, and W. A. Kuperman, “Monitoring deep-ocean temperatures using acoustic ambient noise,” Geophys. Res. Lett. 42, 2878-2884 (2015);
2K. G. Sabra, B. Cornuelle, W. A. Kuperman, “Sensing deep-ocean temperatures,” Physics Today 69, 32-38 (2016).
3R. J. Urick, “The noise of melting icebergs,” J. Acoust. Soc. Am. 50, 337-341, (1971);
4E. C. Pettit, K. M. Lee, J. P. Brann, J. A. Nystuen, P. S. Wilson, S. O’Neel, “Unusually loud ambient noise in tidewater glacier fjords: A signal of ice melt,” Geophys. Res. Ltt. 42, 2309-2316 (2015);
5O. Glowacki, G. B. Deane, and M. Moskalik, “The intensity, directionality, and statistics of underwater noise from melting icebergs,” Geophys. Res. Ltt., 45, 4105–4113 (2018);
6C. A. Green, P. S. Wilson, “Laboratory investigation of a passive acoustic method for measurement of underwater gas seep ebullition,” J. Acoust. Soc. Am. 131, EL61 (2012);
7T. G. Leighton and P. R. White, “Quantification of undersea gas leaks from carbon capture and storage facilities, from pipelines and from methane seeps, by their acoustic emissions,” Proc. R. Soc. A 468, 485-510 (2012);
8T. C. Weber, L. Mayer, K. Jerram, J. Beaudoin, Y. Rzhanov, D. Lovalvo, “Acoustic estimates of methane gas flux from the seabed in a 6000 km2 region in the Northern Gulf of Mexico,” Geochem. Geophys. Geosys. 15, 1911-1925 (2014);
9D. Lüthi, M. Le Floch, B. Bereiter, T. Blunier, J.-M. Barnola, U. Siegenthaler, D. Raynaud, J. Jouzel, H. Fischer, K. Kawamura, and T. F. Stocker, “High-resolution carbon dioxide concentration record 650,000–800,000 years before present,” Nature 453, 379-382 (2008);
10C. Turley and J.-P. Gattuso, “Future biological and ecosystem impacts of ocean acidification and their socioeconomic-policy implications,” Curr. Opin. Environ. Sustain. 4, 278-286 (2012);
11D. R. Barclay and M. J. Buckingham, “A passive acoustic measurement of ocean acidity (A),” Conference & Exhibition Series on Underwater Acoustics, 5, 941 (2019).
12J. Howard, S. Hoyt, K. Isensee, E. Pidgeon, M. Telszewski (eds.). Coastal Blue Carbon: Methods for assessing carbon stocks and emissions factors in mangroves, tidal salt marshes, and seagrass meadows. Conservation International, Intergovernmental Oceanographic Commission of UNESCO, International Union for Conservation of Nature. Arlington, Virginia, USA. (2014).
13G. R. Venegas, A. F. Rahman, K. M. Lee, M. S. Ballard, P. S. Wilson, “Toward the Ultrasonic Sensing of Organic Carbon in Seagrass‐Bearing Sediments,” Geophys. Res. Ltt. 46, 5968-5977 (2019);