Adams D.K.,Woods Hole Oceanographic Institution |
Arellano S.M.,WHOI |
Govenar B.,Rhode Island College
Oceanography | Year: 2012
Visually striking faunal communities of high abundance and biomass cluster around hydrothermal vents, but these animals don't spend all of their lives on the seafloor. Instead, they spend a portion of their lives as tiny larvae in the overlying water column. Dispersal of larvae among vent sites is critical for population maintenance, colonization of new vents, and recolonization of disturbed vents. Historically, studying larvae has been challenging, especially in the deep sea. Advances in the last decade in larval culturing technologies and more integrated, interdisciplinary time-series observations are providing new insights into how hydrothermal vent animals use the water column to maintain their populations across ephemeral and disjunct habitats. Larval physiology and development are often constrained by evolutionary history, resulting in larvae using a diverse set of dispersal strategies to interact with the surrounding currents at different depths. These complex biological and oceanographic interactions translate the reproductive output of adults in vent communities into a dynamic supply of settling larvae from sources near and far. © 2012 by The Oceanography Society.
News Article | January 13, 2016
Predatory behaviors of great white sharks deep into the water are unknown to man. Whether they hunt for preys or swim peacefully underwater is a question that seems impossible to answer via direct observations by humans. Fortunately, an underwater robot installed with REMUS SharkCam, was able to record footages of sharks, paving the way for better understanding of the species' behavior below the water surface. In November 2013, the autonomous underwater vehicle (AUV) installed with six high-definition cameras sailed off Mexico's Guadalupe islands where sharks are known to gather massively. The main goal was to understand how white sharks behave. "Most of what we know about white shark predatory behavior comes from surface observations," said lead researcher Greg Skomal from Massachusetts Division of Marine Fisheries. To know what happens at depth, researchers need a specialized tool and for Skomal, that is the REMUS AUV. For Woods Hole Oceanographic Institution (WHOI) engineer Amy Kukulya, who is also one of the principal researchers, the team wanted to prove that the REMUS SharkCam technology is an essential modality for observing animals and obtaining information about the animals' habitat and behavior. The animal behavior captured by the videos range from simple nudging to strong bumping of the vehicle. The bumps were said to be a form of aggressive behavior, comprising of short physical interaction, most commonly characterized by the shark nudging the vehicle with its snout. In nine instances, the researchers noted aggressive bites, which are said to be a predatory behavior. The bites typically took place at the rear of the vehicle. "Predation events are rarely witnessed," the authors wrote. Almost all recorded predatory actions were observed on water surfaces. In the expedition, however, predatory behavior on the surface was rarely seen. The researchers hypothesized that maybe Guadalupe's clear waters pose varying hunting opportunities for the sharks. For example, sharks may stalk preys from deeper parts of the water where it is darker. Because of the island's visible waters, the sharks are able to see its prey's silhouette and attack it from below. The expedition consisted of six AUV missions that were performed for a period of seven days. During that time, the experts were able to tag and track a total of four sharks, collecting 13 hours' worth of video data. Among the shark species observed were one male and three female great white sharks, including a 21-foot Deep Blue from 100 meters or about 328 feet deep under. While the main animal being observed was the great white shark, the video was also able to capture footages of animals that were not being tracked. All in all, the investigators were able to record 30 interactions with 10 individual sharks. The expedition marks the first successful endeavor to autonomously track and capture any marine animal. The data gathered in the experiment may pave the way for better conservation measures that the marine animals need for survival. The REMUS AUV was initially created to aid coastal mapping and monitoring projects. As more versions were released, the developers were able to customize the vehicle for other purposes. The REMUS SharkCam is equipped with salinity and temperature probes, water current detectors, six HD cameras and other sensors to enable observations from various angles and perspectives. The findings of the expedition were published in the Journal of Fish Biology.
News Article | April 12, 2016
Thousands of crabs are gathering off the coast of Panama, an event which is resembling an alien invasion, according to researchers. This occurrence is a surprise to researchers who have studied the animals. Red crabs are massing on the Hannibal Bank Seamount, located in the waters near Panama. The animals are gathering in oxygen-poor water just above the seafloor, around 1,200 feet beneath the surface of the water. Researchers aboard the Deep Rover 2 submersible, taking part in the last dive of a month-long investigation, recorded the unexpected encounter in April 2015. The team noticed the water was becoming murkier as they dove to greater depths. "There was this turbid layer, and you couldn't see a thing beyond it. We just saw this cloud but had no idea what was causing it. As we slowly moved down to the bottom of the seafloor, all of the sudden we saw these things. At first, we thought they were biogenic rocks or structures. Once we saw them moving--swarming like insects--we couldn't believe it," Jesus Pineda, a biologist at WHOI, said. Pleuroncodes planipes, also known as tuna crabs, are often found in waters off Baja California and the Gulf of California. They are not normally found as far south as Panama, and finding a large gathering of the creatures was especially surprising to investigators. This event marks the furthest south the animals have ever been seen. The tuna crab, which are a favorite food of the large fish for which they are named, may have moved to the low-oxygen water as a means to avoid predators, which also includes marine mammals. Seamounts like the site of the gathering are under water mountainous regions, rich with a wide variety of life forms. The study which found the underwater meeting of crabs was aimed at discovering why the Hannibal Seamount is able to sustain such a wide range of plants and animals. A large group of red crabs washed onto the beaches of southern California just months after the unusual gathering near Panama was recorded. Biologists believe this event was driven by warming water, heated by El Nino. Analysis of the unisual gathering of tuna crabs was presented in the journal PeerJ. © 2016 Tech Times, All rights reserved. Do not reproduce without permission.
News Article | November 23, 2015
A new study has concluded that long-term warming of the Indian and Pacific oceans worsened the deadly floods that hit Australia in 2010/11. During the summer of 2010/11, a series of floods hit the northern Australian state of Queensland, affecting at least 90 towns, over 200,000 people, killing at least 38 people (with another 9 listed as missing at the time), and causing AUD$2.38 billion worth of damage and an estimated reduction in Australia’s GDP of about $40 billion. Enough rain fell, in fact, to cause a filling of the rarely-filled Kati Thanda–Lake Eyre in the middle of the desert country, and even had enough of an impact to cause a drop in global sea levels. At the time it was assumed that a hyperactive La Niña was at least partly at play behind the sheer intensity of the weather patterns behind the flooding, and now a new study by a team of US and Australian researchers working out of the Woods Hole Oceanographic Institute in Massachusetts, United States, has concluded that both a strong La Niña and a long-term ocean warning were behind the floods. The results of the research were published in an article (How did ocean warming affect Australian rainfall extremes during the 2010/2011 La Niña event?) in the journal Geophysical Research Letters, attempting to discern the causes behind the phenomenal conditions that led to the flooding. “The sea surface temperatures around Australia during 2010/2011 were on average 0.5°C warmer than they were 60 years ago,” said lead author Caroline Ummenhofer, a physical oceanographer with Woods Hole Oceanographic Institution (WHOI). “While many past studies have found a global warming link to heat extremes, this study is one of the first to show how ocean warming can impact a heavy rainfall event.” The researchers determined that Australia was surrounded by extremely warm sea surface temperatures in the eastern Indian Ocean (to the west of Australia), western Pacific warm pool region (to the north and east of Papua New Guinea), and the Coral Sea (to the north-east of Australia). These warmer sea surface temperatures led to rainfall in Australia’s north-east 84% above average. In fact, the researchers determined that all the conditions put together increased Australia’s chances of encountering rainfall this severe by a factor of three during a strong La Niña event. “The additional warming of the oceans has profound impacts on the atmosphere,” said co-author Prof Matthew England from the ARC Centre of Excellence for Climate System Science. “It increases the amount of moisture in the atmosphere and can intensify rain-producing circulation conditions.” “This is why in 2010/11 more moisture was brought onshore along Australia’s east coast. Stronger rising motion over the northeast resulted in higher rainfall, making it more likely for Australia to suffer extreme rainfall conditions during this strong La Niña.” Of tangential interest to these findings is previous research which has concluded that increased warming of ocean temperatures in conjunction with global warming as a whole will lead to more frequent La Niña and El Niño events. “Australia has long been acknowledged as a country of extremes but this research suggests extreme rainfall events may become far more frequent in a warming world,” said Ummenhofer. “As we come into climate change talks in Paris, this research offers yet another incentive for countries around the world to take action to forestall global warming.” Image Credit: Markus Gebauer / Shutterstock.com Get CleanTechnica’s 1st (completely free) electric car report → “Electric Cars: What Early Adopters & First Followers Want.” Come attend CleanTechnica’s 1st “Cleantech Revolution Tour” event → in Berlin, Germany, April 9–10. Keep up to date with all the hottest cleantech news by subscribing to our (free) cleantech newsletter, or keep an eye on sector-specific news by getting our (also free) solar energy newsletter, electric vehicle newsletter, or wind energy newsletter.
News Article | August 29, 2016
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.