Lilian Dove: Tagging seals with sensors helps scientists track changes in currents and climate
Weddell seal coming up for air in the Southern Ocean.
PROVIDENCE, R.I.
A surprising technique has helped scientists observe how Earth’s oceans are changing, and it’s not using specialized robots or artificial intelligence. It’s tagging seals.
Several species of seals, such Weddell seals, live around and on Antarctica and regularly dive more than 100 meters in search of their next meal. These seals are experts at swimming through the vigorous ocean currents that make up the Southern Ocean. Their tolerance for deep waters and ability to navigate rough currents make these adventurous creatures the perfect research assistants to help oceanographers like my colleagues and me study the Southern Ocean.
Seal sensors
Researchers have been attaching tags to the foreheads of seals for the past two decades to collect data in remote and inaccessible regions. A researcher tags the seal during mating season, when the marine mammal comes to shore to rest, and the tag remains attached to the seal for a year.
A researcher glues the tag to the seal’s head – tagging seals does not affect their behavior. The tag detaches after the seal molts and sheds its fur for a new coat each year.
The tag collects data while the seal dives and transmits its location and the scientific data back to researchers via satellite when the seal surfaces for air.
Scientists attach a tag to a seal after it is safely tranquilized. Etienne Pauthenet
First proposed in 2003, seal tagging has grown into an international collaboration with rigorous sensor accuracy standards and broad data sharing. Advances in satellite technology now allow scientists to have near-instant access to the data collected by a seal.
New scientific discoveries aided by seals
The tags attached to seals typically carry pressure, temperature and salinity sensors, all properties used to assess the ocean’s rising temperatures and changing currents. The sensors also often contain chlorophyll fluorometers, which can provide data about the water’s phytoplankton concentration.
Phytoplankton are tiny organisms that form the base of the oceanic food web. Their presence often means that animals such as fish and seals are around.
The seal sensors can also tell researchers about the effects of climate change around Antarctica. Approximately 150 billion tons of ice melts from Antarctica every year, contributing to global sea-level rise. This melting is driven by warm water carried to the ice shelves by oceanic currents.
With the data collected by seals, oceanographers have described some of the physical pathways this warm water travels to reach ice shelves and how currents transport the resulting melted ice away from glaciers.
Seals regularly dive under sea ice and near glacier ice shelves. These regions are challenging, and can even be dangerous, to sample with traditional oceanographic methods.
The amount of excess heat (shown as energy) that the upper ocean (above 700 meters), deep ocean (below 700 meters), atmosphere and Earth have been taking up has increased over the past few decades. All values are relative to 1971, and uncertainty in the ocean values dominates the total uncertainty (black dotted line). Intergovernmental Panel on Climate Change
Across the open Southern Ocean, away from the Antarctic coast, seal data has also shed light on another pathway causing ocean warming. Excess heat from the atmosphere moves from the ocean surface, which is in contact with the atmosphere, down to the interior ocean in highly localized regions. In these areas, heat moves into the deep ocean, where it can’t be dissipated out through the atmosphere.
The ocean stores most of the heat energy put into the atmosphere from human activity. So, understanding how this heat moves around helps researchers monitor oceans around the globe.
Seal behavior shaped by ocean physics
The seal data also provides marine biologists with information about the seals themselves. Scientists can determine where seals look for food. Some regions, called fronts, are hot spots for elephant seals to hunt for food.
In fronts, the ocean’s circulation creates turbulence and mixes water in a way that brings nutrients up to the ocean’s surface, where phytoplankton can use them. As a result, fronts can have phytoplankton blooms, which attract fish and seals.
While we traditionally consider the ocean to be blue, it can actually appear green from space because of phytoplankton blooms. Currents can stretch out these blooms, and seals prefer to feed in these locations.
Scientists use the tag data to see how seals are adapting to a changing climate and warming ocean. In the short term, seals may benefit from more ice melt around the Antarctic continent, as they tend to find more food in coastal areas with holes in the ice. Rising subsurface ocean temperatures, however, may change where their prey is and ultimately threaten seals’ ability to thrive.
Seals have helped scientists understand and observe some of the most remote regions on Earth. On a changing planet, seal tag data will continue to provide observations of their ocean environment, which has vital implications for the rest of Earth’s climate system.
Lilian Dove is a post-doctoral fellow of oceanography at Brown University.
Lilian Dove does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
Todd McLeish: It's a busy time at the Mystic Aquarium's Seal Rescue Clinic
via ecoRI News (ecori.org)
MYSTIC, Conn.
The Seal Rescue Clinic at Mystic Aquarium is a modest, outdoor, fenced area where seals, sea turtles and other marine animals rescued from nearby beaches are cared for until they are ready to be released back into the wild. And in winter, it’s a busy place.
Last week, swimming in a 12-foot-diameter tank containing 3,200 gallons of water, was a young harbor seal found malnourished on a Long Island beach in December. A few steps away in one of five 700-gallon intensive care tanks was a newly arrived gray seal pup recovered from a beach in Maine, and another gray seal pup — this one stranded on Fisher’s Island, N.Y. — rested in a smaller tank.
Inside an adjacent tent, food and medications were being prepared by staff and interns to ensure that the animals recover as quickly as possible.
“January to April is our busy season for responding to live animals,” said Janelle Schuh, who directs the clinic and the aquarium’s Animal Rescue Program. “That’s when we see gray seals pupping off our shoreline and when harp seals and hooded seals are migrating into our area.”
Aquarium staff and about 250 trained volunteers respond to some 150 reports of sick, stranded and dead marine mammals in southern New England and Fisher’s Island, N.Y., annually — about 70 percent of which come from Rhode Island.
When it’s deemed necessary to rescue an animal, it’s herded into a mobile kennel and delivered to the Seal Rescue Clinic for round-the-clock care. When necessary, veterinarians may conduct surgeries and other procedures in the aquarium’s new veterinary hospital, which opened in December.
The clinic also rehabilitates animals recovered by organizations elsewhere in the Northeast that don’t have their own clinics, including a manatee found on Cape Cod last fall that was eventually flown to Florida by the Coast Guard.
Last year was the aquarium’s busiest year for rehabilitating seals. About 30 animals were rescued and brought to Mystic — half of them harbor seal pups recovered in the summer in Maine — and 25 of them were nursed back to health and released at Blue Shutters Beach in Charlestown. Most were young seals struggling with malnourishment, dehydration and traumatic wounds such as shark bites. Other animals were suffering from human interactions, such as fishing-gear entanglements or boat-propeller wounds.
How long the animals remain at the aquarium depends on their age and the severity of their malady.
“This time of year, we often turn around a dehydrated harp seal in a month, gray seal pups in two or three months, and days-old harbor seal pups are usually here four or five months,” Schuh said. “They’re sometimes here for over a year if they have bad injuries.”
She said the number of stranded animals isn’t increasing, but it’s unlikely that it will decrease enough to put her out of a job.
“There’s always going to be a need,” she said. “Marine mammal populations are increasing significantly, especially seal populations, and there will always be human interactions as the number of animals increases.”
While few seals have been rescued from disease in recent years, an outbreak of the avian flu virus in harbor seals in 2011 resulted in ongoing research projects that require aquarium staff to collect biological samples from every animal that comes into the clinic.
According to Schuh, one of the benefits of the Animal Rescue Program is the public education that results from the rescue, rehabilitation and release of the animals. The public learns first-hand how their actions, such as the irresponsible disposal of plastics, can affect marine creatures.
Those who observe a seal or other marine mammal or sea turtle on a beach are encouraged to report it to the Mystic Aquarium Animal Rescue Program at 1-800-572-5955, ext. 107. The aquarium advises the public to give the animal plenty of space, don’t touch it, keep pets away, and be observant for obvious signs of injury, general body condition and any identification tags.
“It’s human nature to do what we can to help an animal in need,” Schuh said. “That’s the philosophy we take here. If we see an animal in need, we’re going to help it and take care of it regardless of what’s happening to the population in the wild. In some cases, they’re too far gone to help, but we can still ease their suffering. It’s the least we can do.”
Todd McLeish runs a wildlife blog and is a contributor to ecoRI News..