The sea otter’s diet includes about 40 marine species, including urchins, crabs, clams, abalones, mussels, and snails. Like land-based plants and trees, kelp and other algae form the base of the marine food web. Rather than using roots — as seagrasses do, which unlike algae are true plants — they cling to the rocky seafloor using growths called holdfasts. * Sea Otter Great White Shark Hagfish Crab. What kind of "eater" are manatees? Since then, this kind of comparative study has been carried out in other parts of Alaska, Canada, Washington state, Russia and California. Confirming the previously uncertain role of sunflower stars in kelp-bed ecology will help researchers as they monitor the resilience of kelp beds across the North Pacific Rim and manage their recovery. For Hakai Institute scientists, undersea surveys bring other challenges. Photo by Sebastian Kennerknecht/Minden Pictures . The organisms sea otters had evolved alongside suddenly lost the main predator that kept them in check. Sea urchins are herbivores and feed on seaweeds like kelp. Without Sea Otters Kelp Forests Are Consumed By Urchins (credit: Mike Kenner), The Sea Otter's Big Appetite Helps Control Sea Urchins (credit: Joe Tomoleoni), Without Sea Otters Eel Grass Is Covered In Thick Algae (credit: Brent Hughes), With Sea Otters Sea Slugs Are Able To Consume Algae (credit: Brent Hughes). Traditionally, California’s iconic sea otter has stepped in to keep urchin populations in check. A new trophic cascade involving sea otters was recently discovered in a Central California estuary. Enduring the challenges of underwater experimentation and monitoring, however, can lead to groundbreaking insights. Sea urchins are voracious grazers of kelp. However, these smaller urchins are a favourite food of sunflower stars. Interspecific Interactions (Predators and relationships): The purple sea urchin is the prey to many other species, such as: - Sea Otters (Left) - Sunflower Starfish (Below) - Horn Sharks (Below) Although they have spines for protection, animals such as the sea otter can break them open and feed on the insides of the urchin. The crucial connection, he discovered, was sea urchins. Without otters to keep them in check, sea urchins in particular, with a healthy appetite for flora, were free to mow down large swaths of kelp forests that once flourished. They use the rock as a table against which they smash their shelled prey to g… Sea otters play a small role in mitigating global climate change, but their impact points to a larger lesson: wildlife … The complexity of trophic … The crucial connection, he discovered, was sea urchins. Sea urchins are related to starfish and look like small, purple hedgehogs. Beginning in 2013, Burt and her colleagues studied rocky reef areas around Calvert Island on the Central Coast of B.C., initially trying to better understand the effect that sea otters were having on undersea ecological communities. 's coastal ecology, glaciology and archaeology done in partnership with the Hakai Institute. Morona contains trogs, squirts, and zinks. Without sea otters, sea urchins and other herbivorous invertebrates are left unchecked to graze through swathes of giant kelp forests, creating barren stretches of coastal habitat behind them that once served as nurseries for fish, seals and hordes of other sea life. Kelp forests in turn provide critical habitat and nutrients to a wide variety of creatures, from the very small to the very large. * Sea Otter Seaweed Kelp Octopus. Sea otters, by eating sea urchins, help kelp to flourish. Subsequent generations of Californians didn’t know anything else, but as sea otters reclaim their historic range, I expect we will continue to discover far-reaching ecological effects that we hadn’t anticipated. Sea otters live in a cold ocean environment and rely on two traits to keep warm: a dense fur coat for insulation and very high metabolism to generate body heat. Urchins eat kelp, and sea otters eat sea urchins. Case study: Sea Otters →Crabs → Sea Slugs → Micro Algae → Eelgrass. Despite the Cold War considerations that placed him there, his research ended up transforming our modern understanding of coastal ecology. “Planet Earth,” says marine ecologist Jenn Burt, “is actually Planet Ocean.”. The correct food chain should be squirts → trogs → zinks . To understand the relationship between the two, Estes needed to find an area that was devoid of otters and see what the kelp forests looked like. Many of the funding sources that have supported our work over the last five years are reducing or suspending funding opportunities as they ride out the pandemic. your subscription today. Sea urchins have recently decimated kelp forests in Northern California, leaving researchers to wonder why Southern California kelp forests have remained relatively intact without sea otters to control the urchin populations. By studying how sea otters were foraging in the Elkhorn Slough—what prey species they were eating and where they were feeding—Dr. Sea urchins are like vacuum cleaners of the ocean floor. This is a mutualism relationship because both species benefit from the interaction. Archaeological evidence indicates that for thousands of years, indigenous peoples have hunted sea otters for food and fur. Researchers have also discovered that kelp forests in the northeast Pacific can be dramatically impacted by the presence of two predators. These urchins would usually eat the majority of the kelp; however the sea otters can prevent this. Burt and her fellow researchers began collecting data in 2013, not knowing that two years later, the epizootic of sea star wasting disease (SSWD) would strike the waters around Calvert Island. They have an interesting method of eating their prey. Manatees eat sea grass to survive, but they do not eat animals. The need to stick with your “dive buddy” and communicate with hand signals or by scrawling on a slate can slow things down, as can murky water. Sea urchins move slowly, crawling with their tube feet, and sometimes pushing themselves with their spines. Aleutian sea otters have been in flux before. He will tuck himself beneath the prickly protection of the purple sea urchin, finding a safe haven in a dangerous ocean. Because the otter food source is easier to excavate from rocky-bottom habitats, as opposed to soft-bottom habitats, more otters tend to live in waters with rocky bottoms with access to shallow-burrowing prey. Fur traders in the 18th and 19th centuries hunted the animals to the brink of extinction, allowing sea urchin numbers to skyrocket, Dr. Rasher said. Sea urchins are voracious grazers of kelp. The complexity of trophic cascades can vary extensively from place to place, but this basic pattern is the foundation for understanding how sea otters fit into a healthy coastal environment. Salomon notes that although many ecologists had suspected that sunflower stars played a role in the resilience of kelp forests, that role had not yet been measured or acknowledged. “Bob listened to my account of what I had seen while diving," Estes recalled in his 2016 memoir Serendipity, "and what I thought it might mean and then abruptly suggested a simple but radically different change in perspective. They feed primarily on algae but also eat slow-moving or sessile animals. Seaweeds and sea otters have a symbiotic relationship as evidenced by the rafts of sea otters (Enhydrus lutra), numbering in the hundreds, bobbing amongst the kelp beds just north of Tofino in Kyuquot Sound, Vancouver Island. One of them is cute and fuzzy — the other one, less so. What would happen to the ecosystem if the Octopus go extinct? 's waters is an incredible tale of recovery for a species once hunted into oblivion for its lush fur. After four years of research, Burt and her colleagues came to a groundbreaking new understanding of the relationships between kelp, urchins and sea otters — thanks to unexpected discoveries about a previously overlooked bottom-dwelling predator. In this relationship, the sea otter eats sea urchins, as discussed above. In coastal areas where sea otters regularly consume sea urchins, kelp forests have a greater chance to take hold and endure, and act as an undersea forest habitat for other marine animals. Sea otters are known to carry rocks when they dive, to increase their weight when diving, as well as to … Burt and her colleagues also carry a panoply of marine science tools: a foldable, two-dimensional box for sampling called a quadrat; sealable bags for collecting everything from kelp to invertebrates; a writing slate with data sheets, pencil and built-in ruler; and meter tapes for measuring survey areas, known as transects. Rough weather on the outer coast can keep research vessels tied up at the dock for days. One of the results of Dr. Estes’ research was to designate sea otters as a “keystone species”. Using a dataset collected over four years, Burt and her colleagues learned that sea otters are not the only predators that have a significant effect on urchins, and thus not the only creature that can help ensure the health and abundance of kelp forests: the less cute but nonetheless impressive sunflower star also plays a major role. Unlike the woods on land, a kelp forest moves with the push and pull of the ocean — and so do the researchers. Burt’s graduate studies undertaken with the Hakai Institute in British Columbia were focused on the ecological and social impacts of sea otter recovery — including the effects that growing sea otter populations have on coastal Indigenous communities. The lined chiton has no self-defense mechanisms, so he often cohabitates with purple sea urchins and green anemones. Hughes discovered that sea otters were feeding on crabs that in turn were feeding on sea slugs. Kelp produce their own food through photosynthesis, absorbing sunlight and organic carbon from the environment. Dr. Estes found that the presence of sea otters had a dramatic effect on coastal habitats (see case study below). Enhydra lutris has a very close relationship with kelp. Now, new research suggests this kelp may also be helping the otters in turn. Sea Otters Are Walled in by Hungry Sharks Outside the safety of the kelp forest, California sea otters are being picked off by sharks. The sea otter’s diet relies heavily on sea urchins that can consume 30 feet of kelp forest in less than a month. In the 1970s, a scientist named Dr. James Estes recognized that he could study the influence of sea otters on other species in their environment by comparing the coastal habitats in Alaska’s Aleutian Islands where sea otters had recovered to similar places where sea otters were absent. The Sea Otters have a Symbiotic Relationship with Kelp. The sea otter eats sea urchins which if there is a large population makes the kelp endangered. The relationships between predators and prey vary among communities. When SSWD struck the region during the winter of 2015, it suddenly brought a new dimension to the research: a rare opportunity to also look at how predatory sea stars influence coastal rocky reef ecosystems. Image courtesy Grant Callegari/Hakai Institute. By controlling the number of crabs, sea otters helped sea slugs and other tiny marine grazers flourish. Islands with sea otters had healthy kelp forests while otter-less islands had barren sea floors littered with sea urchins but no kelp. These furry creatures are closely intertwined with the life cycle and recovery of kelp forests from urchin predation. Large-scale hunting, part of the Maritime Fur Trade, which would eventually kill approximately one million sea otters, began in the 18th century when hunters and traders began to arrive from all over the world to meet foreign demand for otter pelts, which were one of the world's most valua… * Hagfish Large Fish Sea Urchin Kelp. The growing sea otter population in B.C. Sea otters are another predator of urchins in the kelp forests. Otters feed on sea urchins, which in turn keeps them from overgrazing on kelp. Sloan Wangel APES Woods Case Study TB p.101-102 Sea Otters Sea otters are well known as a keystone species because of their ability to transform sea urchin-dominated communities into kelp-dominated communities by preying on sea urchins and thus reducing the intensity of herbivory. Symbiotic Relationships Natural Selection Works Cited QuIz. Sea otters are considered a keystone species because of the crucial ecological role they play in maintaining the health and stability of the nearshore marine ecosystem. Sea otters have the thickest fur of any mammal. Their beautiful fur is a main target for many hunters. In 1970, an ecologist named James A. Estes traveled to Amchitka Island in Alaska’s Aleutian archipelago to study sea otters. Kelp is a type of marine algae. The stipes and fronds of a kelp forest create a three-dimensional lattice that benefits everything from invertebrates like snails and anemones to marine mammals like seals and whales — providing food, hiding places and shelter. Which animal is the Decomposer? They are sensitive to temperature, ripped up by storms and affected by currents and waves. The disease outbreak created what is known to researchers as a natural experiment — a unique condition that appears without artificial or planned intervention. The kelp can flourish, providing habitat for many ocean organisms. By wiping out huge numbers of sea stars, including those in nearshore kelp-producing zones, SSWD had created a new set of research conditions. As sea otters reclaimed their role as predators in this estuary, they helped restore balance to this important habitat connecting land to sea. Now numbering in the thousands, the appetite of the otters is dramatically altering large parts of the West Coast ecosystem. In the wake of a devastating disease outbreak that ravaged starfish populations from Alaska to Mexico, researchers like Jenn Burt are just starting to understand the role that sunflower stars play in helping kelp beds to thrive. As he tells in Serendipity, what he saw when he put on his scuba gear and entered the waters off Shemya shocked him: "When I looked down at the seafloor, I was stunned by the vast numbers of urchins and the absence of kelp… Every place I looked was the same—large and abundant sea urchins over a seafloor of crustose coralline algae with little or no kelp… In the absence of sea otter predation, sea urchins had increased in size and number, and the larger and more abundant urchins had eaten the kelp. “When you descend below the surface, it’s like going into space. When boats are able to go out to gather data — in Burt’s case, counting sunflower stars, or performing an undersea experiment to track urchin feeding rates — divers have only 45 to 60 minutes to complete their task before their oxygen runs out. The Atomic Energy Commission had sponsored his research there ahead of a contentious nuclear test on the island. A population that once extended continuously along the North Pacific Rim was reduced to a few small remnant colonies. The sea otters help the kelp by eating the sea urchins because if there is too big of a population of sea urchins the kelp is endangered. “Sea star wasting disease came and did the experiment for us, and research on the Central Coast with Jenn Burt provided evidence of the important role that sunflower stars have,” says Salomon. But a new twist on this relationship, usually understood as a three-way interaction between urchins, kelp and sea otters, has recently come out of the work done on the Central Coast by Jenn Burt and her Hakai Institute colleagues. Just as terrestrial forests support a vast range of life, the stipes and fronds of a kelp forest benefit everything from sea anemones to rockfish to whales. By controlling the size and number of sea urchins (sea urchins are one of their favorite foods, and they eat the larger ones first), sea otters created the opportunity for kelp to grow and flourish, which in turn created habitat for numerous other kelp forest dwellers. This type of relationship between a predator (sea otter), herbivore (urchin), and plant (kelp) is known as a trophic cascade. When they did, says Burt, the insights came not only from her, but from “looking at the system with some clever modellers, from having coffees with Jim Estes and from talking with people who had seen similar things in other areas with green urchins.”. Sea otters eat about 25% of their weight every day, and is arguably the number one cause in sea otter deaths, when they cannot forage enough food to feed themselves. Fortunately, sea otters have an appetite for sea urchins and they help to keep sea urchins in check, allowing the kelp to flourish and capture CO 2. A keystone species is one that is comparatively rare but has a strong influence on its environment. Now, a ne… * Sea Urchin Kelp Crab Large Fish. When otters are present, urchins hide in crevices and snack on kelp scraps. Her mentors and colleagues include renowned coastal ecology experts Jane Watson and Anne Salomon. But Estes didn’t understand the real meaning of what he’d seen until a meeting with veteran … The grazers in turn kept the eelgrass blades clean and healthy. Sea otters do an excellent job of eating large sea urchins over eight centimetres in diameter, but they tend to leave behind smaller urchins. In places where sea otters have disappeared, sea urchins will eat the kelp forest until it’s gone. But Estes didn’t understand the real meaning of what he’d seen until a meeting with veteran ecologist Bob Paine. Perhaps the biggest challenge is that the waters of the Central Coast are rarely still. “There are so many interactions in the ocean that we don’t totally understand and probably never will, because we can’t systematically remove and then replace all the animals in the ocean,” says Burt. [16] “It was very interesting to learn how they give a helping hand to the apex predator in these areas, sea otters.”. That’s the bigger narrative around this research that I think is really neat.”. Observing sea otters and kelp beds on Amchitka — both onshore and during scuba dives — led Estes to question the links between them. Otter populations are affected by the density of prey they hunt. Sea otters, in turn, are equally voracious predators of sea urchins. On the Central Coast reefs she studied, Burt links the loss of sunflower stars to a startling 300 per cent spike in the population of small and medium-size urchins, and to a resulting 30 per cent decline in kelp density. Juvenile salmon, herring and rockfish all use kelp beds for habitat, as do crabs, sea stars, abalone and other snails. These small urchins also readily devour kelp, and if their numbers swell, they begin to thin out kelp forests. He found that about 350 kilometres to the west of Amchitka, off a remote island called Shemya. To oblivion and back. Places that are overrun with urchins are known as “urchin barrens”. The waters around the Hakai Institute on Calvert Island are at the leading edge of this expansion, and like the Aleutian Islands, are well suited to this sort of study. Some sea otters eat so many purple sea urchins over their lifetime that their teeth and bones actually become stained purple (known as echinochrome staining). This metabolism needs to be continually stoked with energy in the form of food, and sea otters must consume as much as 25% of their body weight each day in order to stay warm and survive. Sea stars and sea otters will happily dine on both creatures, and harlequin ducks will pluck the chiton from his rocky abode. Watch this great short film to understand more about keystone species: While scuba diving in the Aleutian Islands, Dr. Estes noticed places where the seafloor was covered with sea urchins and no kelp remained. Sea otters eat shellfish and other invertebrates (especially clams, abalone, and sea urchins). The Sea Otters eat Sea Urchins, which harm the kelp. Thanks to Estes, and the work of subsequent researchers like David Duggins and Jane Watson, the beneficial effects of sea otters in propagating kelp habitats have been well established among ecologists, and increasingly well known to the general public. Sea otters aren’t just cute – these marine mammals play a vital role protecting the kelp forests which maintain our climate and prevent storm damage. You need an active subscription to post a comment. 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