Can You Hear Me Now?

When we were preparing for the first leg of HUMPACS, referred to as HUMPACS East, we found ourselves faced with a tough decision when it came to how the hydrophone should be mounted.

“Do we hang the hydrophone, or try to hard mount it as close to the sub as possible?”

When doing hydrophone operations just outside of Puako, Hawaii, we have found that you get the best audio if you hang the hydrophone at least 30 feet below the sub. This, obviously, is due to the fact that we’re basically decoupling the hydrophone from the sub. We also are able to pick up more sounds when we’re deeper.

Hearing that, you might wonder why we decided to hard mount the hydrophone during HUMPACS East.

Well, what we have also learned through years of experience monitoring the gliders off the coast of the Big Island is that when we have a hydrophone hanging, ocean currents become a much larger problem.

There are different currents at different depths, and so even though the glider (float, sub and hydrophone) are all relatively in vertical alignment, each part of them is getting pushed and pulled by a different current.

In Hawaii, it’s not that big of a deal for us because we keep the gliders in a relatively small area the majority of the time, and we can go rescue the glider if we really need to.

When sending it across the Pacific Ocean, it’s a different story. There are no rescue missions. It just has to work!

For that reason, we decided to keep the hydrophone hard mounted directly to the sub, with no separation or “acoustic isolation”. We knew that the background noise (flow noise, wing springs and rudder) would be very loud. However, we confirmed that even with all this loud background noise we would be able to detect humpback whales, as we did a proof of concept with humpbacks singing off Puako before sending it east. All this was worth it to know that the hydrophone would be very safe. After all, we’d never made this trek before, (no one had for that matter), so we didn’t know what kind of abuse it might encounter. Sharks, rubbish, wear and tear, getting tangled up by the umbilical. These were all big concerns, and, at the time, we needed to play it as safe as possible.

HUMPACS East  Copper Hydrophone Mount

HUMPACS East

Copper Hydrophone Mount

All these concerns continued to stand true with HUMPACS West. We still agreed that the unknowns about drifting were too much of a risk, so we mounted it close, but not hard mounted.

Since we did not encounter any drift that could have entangled the hydrophone, nor any shark bites, for HUMPACS West, we decided to see what the minimum distance was that we could drop the hydrophone and achieve higher quality audio. We still needed to keep the hydrophone safe, but we wanted more vibration isolation between the sub and the hydrophone itself.

After testing many different materials and changing up the distance of which we dropped the hydrophone below the sub we came to the conclusion that a three inch drop using EPDM Fiberglass Reinforced rubber sheets to mount was the way to go. It improved our audio and also kept the hydrophone safe at the same time. As an additional safety measure, we added a deflector bar to the bottom of the sub to help prevent shark bites and entanglement on the hydrophone.

HUMPACS West  EPDM Fiberglass Reinforced Hydrophone Mount

HUMPACS West

EPDM Fiberglass Reinforced Hydrophone Mount

Take a look at the two spectrograms below and see the difference in noise levels. HUMPACS West is exponentially more quiet than HUMPACS East. There is also almost a complete elimination of the 650Hz and 975Hz harmonics from the rudder module. This, alone, is a very improved piece of the puzzle, as the primary range that we listen and view the humpbacks’ song is in that <1KHz range.

HUMPACS West Spectrogram

HUMPACS West Spectrogram

HUMPACS East Spectrogram

HUMPACS East Spectrogram

As you can see, HUMPACS West is much more quiet as far as background noise goes. What’s that do for us? Well, if the background noise is less, then it becomes substantially easier to detect humpback whales (and other species). This improvement should greatly improve our post processing efforts, and is more efficient at detecting as many humpbacks as possible.

Currently, Europa is a little over 700nm (nautical miles) west of the Big Island of Hawaii. Follow its journey on the HUMPACS page!

Aloha!


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We're Back!

Europa is back in the water on her second mission to listen for humpback whales, just in time for the Holidays. Last year, Europa successfully completed the East Leg (from Hawaii to the Baja California Seamount Province and back), and now she will swim to the Mariana Trench and back (the West Leg). Biologists have wondered if there is an undiscovered distribution of humpback whales among the seamounts between these areas. Since the East Leg was successful, we hope Europa’s journey west will be triumphant. You can track Europa’s path on our website. Stay tuned for more updates!

Wishing you a Happy Holiday and a Joyful New Year!


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Photo Time-lapses from Europa

Almost one month has passed since we recovered Europa, and we are still in the process of analyzing data, however; we have reviewed all of our photos. During the 3.5 month mission, we had a camera attached to both the top and bottom of Europa’s float that took above and underwater images periodically on a daily basis.

The top camera was mounted on the back of the float looking forward, which enabled us to inspect the float and antenna deck during the mission. The bottom camera looked down towards the sub underneath the water to help us check the sub and umbilical. In the previous blog, we mentioned we had a gooseneck barnacle that grew over the underwater camera lens. Even so, we were still able to get glimpses of the sub for diagnostic purposes.

Over the 3.5 month mission, the top and bottom mounted cameras took over 500 photos each. We have constructed two time-lapse videos of the above and underwater pictures, which are each a little over three minutes long. We were able to capture some fantastic photos! The sunset photos and waves washing over the float are captivating, and it’s fun to watch the barnacle grow over time in the underwater footage.

In our next blog, we will post some sample of audio files of some exciting sounds we’ve heard, including odontocetes whistles and clicks, echolocation, and other unusual noises. Stay tuned!


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Europa is Home!

After many late nights and early morning of monitoring Europa, she was finally close to home. Europa endured many challenges during the 3.5-month mission, from huge waves, high winds, strong currents, sharks, marine debris, to near collisions with large ships! We are very proud of her!

On April 24th, she rounded South Point and started veering north as she fought powerful south-bound currents. The currents had her barely creeping, so at daybreak on the 25th, our team loaded our vessel, the May Maru, with recovery gear, and trailered the boat to launch from Honokohau Harbor in Kona. We found Europa just south of Milolii, about five miles off the coast.The retrieval mission was about 90 miles round trip and took about four hours, an effort well spent.

In this video we were approaching Europa just south of Milolii,

Here we were pulling Europa up onto our boat with the davit.

Once we got her on the deck, we visually inspected her for any damages and documented all of the critters that had hitched a ride, such as barnacles, crabs, and fishes. We then secured her to the deck and brought her home. The following day, we disassembled and examined all the payloads, and continued to document, and then identify, the marine organisms and debris that lingered in the payload bays. Overall, everything was in good shape, and the biofoul was minimal.

We are currently in the process of analyzing the temperature and salinity data from the HOBO logger that was attached to the bottom of the float. We have over 800 above and underwater pictures to download. Also, we are preparing to investigate our 2,000+ hours of acoustic data. We will, therefore, be hard at work for the next few months. After our analysis, we’ll publish our results in a peer-reviewed Journal and on our website. Stay tuned for updates within the following months, and thank you for following our HUMPACS mission. We can’t wait to see what will be revealed!


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Land Ho!

Europa  approximately 40 nautical miles off South Point (the red star).

Europa approximately 40 nautical miles off South Point (the red star).

Europa is nearing the shores of Ka Lae (ka-lie), or South Point, which is the southernmost tip of the Big Island and the United States. Archaeological excavations and Hawaiian tradition indicate Ka Lae, meaning “the point,” was the first place the early Polynesians occupied in Hawaii, as early as A.D. 124. The area is an official National Historic Landmark (NHL) because of its cultural significance and importance. Claiming this region as an NHL enables protection and preservation under the National Historic Preservation Act (NHPA).

Two prevailing currents converge off the coast of South Point: Kāwili and Hala’ea.The Kāwili, or the Hawaiian Lee Counter Current, flows from west to east all the way from Asia. This current is thought to have helped early Polynesians find the Hawaiian Islands while traveling from their original homeland: Kahiki.

The Hala’ea, also known as the North Equatorial Current, travels east to west by trade winds and is named after the greedy chief, Hala’ea. Oral histories and texts say Hala’ea ordered his men to throw all of their aku (tuna) into his canoe so he could claim all of the fish for himself. His men threw so many fish into his boat that it capsized, and he was swept out to sea by a strong current. Hence, the current bears his name.

The currents bring many nutrients and make the waters off Ka Lae abundant in fish. However, they also carry a vast amount of trash that piles up along the coastline. The majority of the waste is plastic, likely from the Great Pacific Garbage Patch carried by Hala’ea.

Since the first settlement of Polynesians, communities within Ka Lae have relied on fish as their prominent resource. In the 1950s, the University of Hawaii and the Bishop Museum excavated a site called Pu’u Ali’i. This location is thought to be one of the first dwellings in Ka Lae established by fishermen. Archaeologists found many different types of large fish hooks and tools to make them, including coral and stone abraders. Further excavations in Ka Lae revealed a fishing shrine (Ko’a) within the Kalalea Heiau. This shrine was created for the fishing god, Ku’ula, to maintain the abundance of fish. Other remaining cultural sites within the area are Lua o Palahemo, the Canoe Mooring Holes, and Lua Makalei.

The federal government manages NHL’s, and although it protects Ka Lae, it does not provide enough support on a local and state level. As environmental and cultural regimes continue to shift in Hawaii, significant stakeholders of Ka Lae (community members, the State of Hawaii, and the Department of Hawaiian Homelands) have recognized the need for additional preservation, conservation, and management efforts. Thus, since 2016, a new management plan has been underway that implements community-based management strategies of long-term land stewardship, and natural resource and cultural management.

Europa was able to swim past South Point without any issues from the currents as she traveled towards Mexico. We hope she doesn’t have any trouble as she passes it once more on her way home. Once she wraps around the point and gets north of Milolii (see map above), we plan to retrieve her with our vessel, the May Maru. She has approximately 80 nautical miles to go until retrieval. Track the rest of Europa's journey on our website and stay tuned for exciting new updates after HUMPACS concludes!


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How the Sea Shapes our Lives

Ocean Currents. Photo by  Atlas for the End of the World

Ocean Currents. Photo by Atlas for the End of the World

The vast, mysterious ocean, covering 71 percent of the Earth, plays an essential role in our everyday lives. Not just for the coastal and island dwellers, but for everyone. The ocean provides many ecosystem services, including food production, fisheries, pharmaceuticals, oxygen regulation, carbon storage and sequestering, water quality enhancement, coastal protection, biodiversity, economy, cultural values, and climate and weather regulation. Without the ocean, we would not be able to survive.

One of the most critical ecosystem services of the ocean is weather and climate regulation because it affects economies and livelihoods on a global scale. The sea has a low albedo, meaning it absorbs most of the sun’s heat radiation. Thus, water molecules heat up and evaporate into the atmosphere and create storms that are carried over long distances by trade winds and currents. These storms can become destructive as they accumulate warm water while traveling over the ocean.

Ocean currents are crucial for regulating the climate and transferring heat around the globe. Water density, winds, tides, and the earth’s rotation direct and power the currents, which are found on the ocean’s surface and at a depth below 900 feet. They move water horizontally and vertically and occur on a local and global scale. The currents create a global conveyor belt that acts as a global circulation system. It transfers warm water and precipitation from the equator towards the cold-watered poles and vice versa. It also plays a vital role in distributing nutrients across the ocean.

As seasons change, so do wind and weather trends, sea surface temperatures, and currents. Currents are stronger in the winter than they are in the summer because there are stronger winds and colder sea temperatures. Furthermore, spring is a considerable transition period. During this time, temperatures begin to warm, the density and salinity of the ocean changes, and wind patterns shift. These factors significantly influence currents, causing them to become unstable.

Without currents, the land wouldn’t be habitable because temperatures would be too extreme; the equator too hot and the poles too cold. Additionally, the precipitation distributed by currents and wind is necessary to all living things and is needed to sustain life. Foreseeable current, weather, and climate trends are key components in maintaining a healthy economy by supporting crops, livestock, tourism, etc., and can also save lives from dangerous storms and create more resilient communities.

Currents are measured and monitored by moored and drifting buoys that relay data via satellite. These buoys are efficient in collecting data, but they are quite costly and require much effort to deploy, retrieve, and maintain. Moored buoys often break from their mooring and can't be implemented in deep waters. Wave Gliders, however, can measure and monitor surface currents on a local and global scale in any seas without the considerable exertion and cost. Therefore, they could be utilized as an alternative to some of the moored buoys or drifters while collecting other vital data such as salinity, sea surface temp, CO2 levels, and much more. 

Europa has not experienced much trouble from the changing spring currents thus far. Although, on April 5th, she hit a robust northern current with no sea state to give her power, which made her veer off course a little. Fortunately, we were able to turn on the thruster (a small solar powered, electric propeller on the sub) that quickly put her back on track. We hope the currents remain steady and in our favor, so she’ll return home as soon as possible.


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Oh Barnacles, those Crusty Foulers!

Barnacles are pesky little creatures. Have you ever heard of Barnacle Bill, the foulest sailor? Well, he’s named that for a reason. Sailors, shipowners, and mariners hate barnacles because they attach to the bottoms of boats and ships (biofouling). Large barnacle colonies weigh marine vessels down, which causes them to drag and burn more fuel. In our case, they stick to the bottom of our Wave Gliders and block the camera’s field of view.

Biofouling is a process where invertebrates, including barnacles, mussels, sponges, and corals stick to marine surfaces. For this to occur, a biofilm consisting of bacteria, algae, seaweed, or diatoms must first form on the substrate. The formation of biofilm is dependent on many environmental factors, however, once it develops, the biofoul rapidly increases.

To prevent biofouling, we experimented with an antifouling Coppercoat™ paint and a 90-10 copper-nickel alloy before deploying Europa. First, we painted the entire vehicle with the Coppercoat™. If we didn’t do this step, a thick layer of barnacles and algae would encrust Europa and significantly weigh her down. We then sheathed the camera within a copper-nickel casing with an acrylic lens in hopes that biofouling would not occur.

This image displays the bottom of Europa's float, painted with a Coopercoat paint. The Camera (facing down) is encased in a copper-nickel alloy housing with an additional copper ring around the acrylic lens to prevent biofouling.

This image displays the bottom of Europa's float, painted with a Coopercoat paint. The Camera (facing down) is encased in a copper-nickel alloy housing with an additional copper ring around the acrylic lens to prevent biofouling.

As a secondary safeguard, we incorporated an additional biofoul resistant copper ring around the lens. Unfortunately, that didn’t work as we’d hoped. Europa has had a barnacle progressively developing over the camera’s field of view for over a month, and there’s nothing we can do about it. Their lifespan is 8-20 years so that barnacle will keep growing until Europa’s mission is complete, at which time we will identify this barnacle. Below is an image sequence of the barnacle forming in the camera lens.

So, besides being annoying, what is a barnacle’s purpose and ecological role? Barnacles are in the Crustacea taxon, meaning they are related to shrimps, lobsters, and crabs. They are most abundant in areas where upwelling occurs, worldwide. As larvae, barnacles function as zooplankton; microscopic organisms that float around as food for other critters. As they morph into adulthood, they affix themselves to surfaces, such as rocks, ships or whales, and eat microscopic plankton through feather-like appendages called cirri. Primarily, they play a trophic role in balancing plankton populations.

Barnacles secrete a robust adhesive substance like super glue that has enormous medical and engineering potential.  Scientists have discovered barnacle’s glue binds the same way humans’ blood does when it clots. By researching it further, scholars can gain more information about how to prevent barnacles from fouling.


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The White Shark Café

A great white shark. Image by  Jim Abernethy, National Geographic.

A great white shark. Image by Jim Abernethy, National Geographic.

Great white sharks, a species over 16 million years old, are one of the most feared animals on Earth.They’re quite frightening; lurking in the ocean with their massive torpedo-like bodies, dagger-like teeth, and soulless, beady eyes. It’s safe to say the movie “Jaws,” is in part responsible for this fear. Let’s face it, they tend to get a bad rap, but sharks aren’t the mindless killing machines we perceive them to be.

Sharks play an essential role in the ocean’s ecosystem by keeping the food web in balance. They are top predators in the sea - a keystone species. Sharks maintain fish populations by eating them. Those fish then eat smaller fish, which eat even smaller fish, etc., all the way down the food chain. If sharks went extinct, the entire composition of the food web would shift and cause a top-down trophic cascade. The need for shark conservation has grown as the demand and exploitation rate of sharks have increased. Fishers kill millions of sharks every year for the Chinese delicacy: shark fin soup.

Every winter, in the North Pacific Basin, hundreds of great whites migrate from the California and Baja California coasts to a subtropical gyre, nicknamed the White Shark Café. This congregation area is located halfway between Hawaii and Baja California. Scientists are unsure why these sharks gather here. Maybe they’re socializing over a hot latte. More than likely, the sharks are meeting in this location to eat or mate.

At the Café, male sharks perform a strange, mysterious behavior of diving up and down continuously to approximately 150 ft. What is the purpose of this behavior? With the goal of gaining more knowledge, the Monterey Bay Aquarium Research Institute (MBARI) and other researchers are attaching camera tags to the sharks’ dorsals to record their diving conduct while they’re at the Café. MBARI has produced a neat video clip about the camera tags, available to view on YouTube.

On Feb 22nd, Europa started swimming through the southern outskirts of the Café, and she is still within the sharks’ migratory route. So far we’ve been fortunate a shark hasn’t chomped on her and obliterated all our data (keeping our fingers crossed)! Also, ship traffic has started increasing as Europa swims further into the Baja California Seamount Province (BCSP). All of this makes her more vulnerable and increases her risk.

Europa is currently surveying a few more seamounts in the BCSP. Then, she’ll start her trek home and continue to collect data. As she heads to Hawaii, we’ll want to keep her at low-risk by steering her south of the Café. Once we approach the Big Island where there’s more ship traffic, we’ll decide the best path into port to prevent a collision. So far, we’ve been able to steer away from any critical danger. We hope to keep it that way!


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Mountains in the Deep Sea

A seamount is an underwater sea mountain formed by plate tectonics and volcanic activity. Seamounts form near the boundaries of tectonic plates and hotspots (Image 1). Plates force ocean and crust to descend towards Earth’s hot interior as they converge and collide near subduction zones. Here, the crust melts and forms into magma. The magma then returns to the surface as it buoyantly rises and fills in the gaps where plates diverge along mid-ocean ridges.

Image 1.  This image from the  Scientific Library Online  displays a range of mapped seamounts. Scientists have only explored a small percent of these seamounts.

Image 1. This image from the Scientific Library Online displays a range of mapped seamounts. Scientists have only explored a small percent of these seamounts.

Earth’s crust is rich in silica. When it subsides, it makes the magma near subduction zones more viscous. Think of honey. Honey is extremely thick and sticky because it has a high silica content. The magma is also high in gases, including water vapor, and carbon and sulfur dioxide, that come from the ocean, soil, and rocks. Viscous substances don’t release gases quickly, so they accumulate in the magma chamber. As the gases increase, the pressure increases and magma explodes through the seafloor. The thick magma builds on the surface of the sea floor and cools rapidly, forming steep mounts. Isolated regions of magma called hotspots also create seamounts.

Seamounts are known to be diverse ecosystems. Vital nutrients are brought in by strong ocean currents and the process of upwelling (Image 2). Upwelling occurs when the wind blows across the ocean’s surface and pushes water away, allowing water to emerge from beneath the surface to replace it, along with nutrients from the deep, cold depths. The pressure of the ocean creates friction along the seamount walls, forcing the nutrients to rise through an eddy (Image 3).

Image 2 . This image from  NOAA  demonstrates the process of upwelling.

Image 2. This image from NOAA demonstrates the process of upwelling.

Image 3. This image is a schematic drawing from  Aliza Vinzant , illustrating a seamount ecosystem. The upward arrow on the left side represents the upwelling current, the whirlpool on the right side illustrates the eddy.

Image 3. This image is a schematic drawing from Aliza Vinzant, illustrating a seamount ecosystem. The upward arrow on the left side represents the upwelling current, the whirlpool on the right side illustrates the eddy.

Nutrients, such as nitrates and phosphates enable the growth of phytoplankton, which are microscopic algae that compose the basis of the marine food web and provide sustenance for a wide range of creatures. Seamounts home a variety of corals, sponges, anemones, mollusks, crustaceans, bivalves, echinoderms fishes, and many more organism. Furthermore, they provide resting and feeding areas for migratory species, such as sperm whales, sea turtles, seabirds, and sharks. Hence, we are exploring the hypothesis that humpback whales may be congregating around seamounts too.

The biodiverse seamount ecosystems are unique because they contain endemic, fragile, long-lived, and rare species. However, this makes the ecosystems vulnerable. Commercial fishers are attracted to these locations because of the seafood abundance. As anthropogenic activity increases, scientists are recognizing the need to understand better the ecology of seamounts and factors that are impacting these sensitive benthic communities.

In a study called, “The Structure and Distribution of Benthic Communities on a Shallow Seamount (Cobb Seamount, Northeast Pacific Ocean),” by Preez et al., they conclude that the majority of seamount communities are at risk from anthropogenic disturbances. They are also at risk from ocean acidification and are refugia for biota from marine climate change. As risk increases, conservation and management efforts also increase. However, efforts will be at a disadvantage if researchers do not collect enough baseline data. NOAA and other organizations are using unmanned underwater vehicles to conduct imagery surveys with the purpose of better understanding the ecology of benthic communities (Image 4).

Image 4.  This picture by  NOAA  depicts image mapping of a seamount.

Image 4. This picture by NOAA depicts image mapping of a seamount.

Europa is past the second seamount and is on her way to a chain of seamounts. At the second seamount, we received an audio snippet that sounded like an odontocete, or toothed whale.  We’ve sent the audio to Dr. Jim Darling and Dr. John Ford (a killer whale specialists) for further analysis.

Stay tuned for more updates and a post about the Shark Café in our next blog!

 


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Commotion in the Ocean

Visibility in the ocean is relatively weak, especially at a depth of 400+ meters, making vision rather useless in the deep sea where whales reside. Sunlight doesn’t travel very far into the ocean. However, acoustic vibrations travel faster and farther in water than they do on land (Image 1). Therefore, sounds are valuable tools in deep, dark environments where whales use their ears as their eyes.

Image 1: An  image by NOAA.  A visual representation how far low-frequency sounds travel through the ocean.

Image 1: An image by NOAA. A visual representation how far low-frequency sounds travel through the ocean.

Animals in marine environments rely on sound for basic survival needs. For example, baleen whales, which are the largest of marine mammals (including humpback, blue, fin, right, and gray whales, etc.) emit long, low-frequency sounds ranging from 7Hz to 22kHz that travel long distances across the ocean. Baleen whales also travel long distances making periodic migratory trips from their feeding grounds to their breeding grounds. Thus, scientists hypothesize that baleen whales use low-frequency sound in part to aid in navigation and long-distance communication.

The ocean is already a naturally loud environment, and humans have significantly increased that noise level. Anthropogenic noise pollution (such as ship traffic) obscures animals' communication, and could potentially have adverse effects on marine life; especially baleen whales (Image2). Although, considerable scientific uncertainty remains. Many factors influence the degree of impact, including multiple characteristics of the sound, and the animal. Potential impacts include behavior alternation, temporary hearing loss, and various communication interferences (Image 3).

Image 2: An  image by the University of Rhode Island . A visual representation (in frequency (Hz)) of how anthropogenic noises interfere with marine mammals. Baleen whales' sounds are masked by seismic, ship traffic and bubbles &amp; spray noises.

Image 2: An image by the University of Rhode Island. A visual representation (in frequency (Hz)) of how anthropogenic noises interfere with marine mammals. Baleen whales' sounds are masked by seismic, ship traffic and bubbles & spray noises.

Image 3: An  image by SSPA . A visual representation of anthropogenic noise interference with marine animals.

Image 3: An image by SSPA. A visual representation of anthropogenic noise interference with marine animals.

Scientists study sounds and their relationship with the environment over a wide range of scales (both spatial and temporal) via a new science called ecoacoustics. They investigate sounds to understand their evolution, functions, and properties under environmental stressors and changes. Sounds are used as tools to monitor ecological factors, such as biotic and abiotic relationships, and animal behavior, diversity, abundance, distribution, etc.

Using hydrophones to record marine acoustics have helped scientists gain knowledge, and a better understanding of the ocean and how we’re affecting it. We are proud to say our Wave Gliders (WGs) don’t produce noise that’s harmful to whales or other marine life. So far, we think WGs do not deter animals: fish aggregate around them, birds rest on them, whales swim near them, and dolphins bow ride them. The WG has revolutionized the way we collect data and monitor the ocean. The hydrophone we attached to Europa is gathering acoustic data 24/7 through which we hope to gain more knowledge and understanding of the sea. Additionally, we expect our data will create a baseline, and contribute to marine ecoacoustics, as well as, support conservation efforts and the management of marine resources.

Europa Update:

Europa is approaching our second seamount; we’re within 25 miles! Stay tuned for a seamount update, the ecology of seamounts, and the habitats they provide in our next blog.


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