Giant Kelp Forest
Sea Otters keep a decent diet of marine plants and small marine animals. One of the important factors to the Sea Otters diet is Giant Sea Kelp Forests. 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. 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 (7). Sea otters have been found to wrap themselves in kelp when they sleep and they also provide shelter for sea otter mothers and pups. This species interaction is considered mutualism, as the sea otter species preys on the Giant Kelp Forest population for food and shelter, sea otters prevent larger animals from degrading the kelp forests.
Based on recent calculations, the presence of otters increased the carbon storage of kelp forests by 4.4 to 8.7 megatons—equivalent to the amount of carbon found in the annual carbon dioxide emissions from 3 to 6 million passenger cars (7). This information gave the value of sea otters, in maintaining carbon-storing kelp forests, anywhere from about $200 million to more than $400 million (7). The degree of influence that otters have on an ecosystem depends on where the carbon ultimately ends up. In general, there are two possibilities. The carbon is initially trapped in a one-off mechanism by the kelp in its tissues. This sequesters carbon for a time, but as pieces of kelp wash ashore and decompose, the carbon is released back into the atmosphere (7). The other possibility is that sloughed-off pieces of kelp may sink to the deep ocean where the trapped carbon can be stored for longer periods of time (7). The second prospect has the greatest potential to decrease atmospheric carbon levels, as carbon could remain trapped in plant tissues at the bottom of the sea for decades or centuries (7). Scientists know that some kelp does end up in the deep ocean; how much, though, is difficult to estimate. This concludes that there is another reason sea otters need to be protected… no sea otters, no kelp forests. |
http://seaotters.com/2012/09/07/thanks-to-sea-otters-kelp-forests-absorb-vast-amounts-of-co2/
http://seaotters.com/tag/keystone-species/
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Butter ClamsIf you’ve ever walked the beach at low tide, you’ve probably seen discarded clam shells all along the shoreline in British Columbia. Well there’s a good reason for that. Researchers have found that over 80% of a sea otter’s diet consists of clams. The approximate edible biomass of their favourite clam species, Butter clams, is 52g and 98g respectively. That means a 75 lb otter eats between 100 and 150 clams per day to meet its nutritional and energetic demands. Clams don't just sit there waiting to be picked up by some sea otter or recreational digger, they want to live, so consequently, the sea otter has to dig to get the clam. The clam can bury itself 10-50 cms under the sand (8). Remember, an otter must consume approximately 25% of its bodyweight in prey each day just to stay alive! This species interaction is considered predation, as the sea otter species preys on the Butter Clam population. Predation is defined as being a biological interaction in which the predator, the animal that is hunting, feeds on its prey, the animal being hunted.
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Killer Whale (Orca)The new phenomenon of killer whales preying on sea otters appears to be one link in a chain of interactions extending from the open sea to the coastal zone and involving a wide range of species at different levels of the food chain. The researchers have been studying the role of sea otters in the coastal ecosystem of Alaska's Aleutian archipelago since the early 1970s. During their field studies they often saw killer whales swimming near sea otters, but never saw one attack a sea otter until 1991 (9). Since then, about a dozen such attacks have been reported. Sea otter populations, meanwhile, have declined by about 25 percent each year during the 1990s throughout large areas of western Alaska and British Columbia (9). In waters inaccessible to killer whales, however, sea otter numbers have remained stable.
The decline in sea otters has allowed their primary prey, sea urchins, to increase in number and strip coastal kelp forests over large areas. A wide array of species was affected by these changes in otter population: coastal fish, filter-feeders like mussels and barnacles, marine birds, and other predators in the system (9). Researchers analyzed the caloric value of sea otters, which are a less nutritious food source than killer whales' usual prey because they have very little blubber. It was estimated that a single killer whale would need to eat 1,825 otters per year to meet its energy requirements and these figures suggest that as few as four killer whales feeding exclusively on sea otters could have driven the population decline observed over a large area of the Aleutian archipelago (9). This is a species interaction considered as predation, as the Killer Whale species preys on the Sea Otter population. Predation is defined as being a biological interaction in which the predator, the animal that is hunting, feeds on its prey, the animal being hunted. |
http://1.bp.blogspot.com/-3ohjisQo7GI/UFXAXnxJoWI/AAAAAAAABRU/tb7W2MR83P0/s1600/killer-whale.jpg
http://cdn1.arkive.org/media/29/29EC8EBE-700F-45AF-B923-67A8A82EA69E/Presentation.Large/Californian-sea-otter-swimming.jpg |