About Sea Otters and Kelp

The sea otter's dark brown fur is the finest and densest of any animal fur. On an adult animal, there are an estimated 650,000 hairs per square inch. A sea otter relies on its fur to keep warm-it doesn't have an insulating layer of blubber as other marine mammals do. Natural oils in a sea otter's fur repel water and trap tiny air bubbles, providing a layer of warm air between the otter's skin and the harsh elements of its environment. Sea otters may spend as much as 48% of the daylight hours grooming their fur. Sea otters sleep, rest, and usually swim by paddling with their hindflippers on their backs. California sea otters spend almost all of their time in the water, while Alaska sea otters often sleep, groom, and nurse their young on land. Tool use is an unusual behavioral trait seen only in sea otters and a few other types of animals. An otter may remove an abalone by repeatedly hitting it with a rock. It also may use a flat rock to break open the shells of crustaceans and mollusks. While holding the rock on its chest, the otter pounds the animal on the rock until it breaks or opens. Sea otters are hungry animals. In a normal day they'll eat one quarter of their body weight by feasting on sea urchins, crabs, clams, mussels and octopuses. To get food, a sea otter may hammer open shellfish with small rocks or dive over 100 metres into the murky ocean depths. Kelp grows in any sea where it is covered in cool, sunlit water and fed with nutrients brought in by the waves. It grows so large and so densely, that it can form underwater forests. These kelp forests make suitable habitats for a host of sea animals, including the sea slug and the sea otter.. Sea otters keep kelp forests healthy Believe it or not, there is a kind of seaweed in the seas off California that grows to 50 metres in length! It is the giant kelp. Other kinds of kelp do not grow quite so big but can still reach three or four metres in length. Sea otters keep kelp forests healthy by eating animals that graze on kelp. When it dives in the shallows of the sea looking for food, the sea otter likes to find just the right meal. This usually includes abalones and other shellfish that humans often enjoy as delicacies. These shellfish are found in great numbers among the kelp forests. Unfortunately, the sea otter's tastes have not made it popular with fishermen who are part of an industry worth millions of dollars a year. In order to make their money, the Californian fishermen wanted otter-free zones, so they alone could catch the shellfish in the kelp forests. They also wanted to stop the people known as conservationists from moving otters into new areas to save them from oil spills. Bad idea This was not just a bad idea for the otters, but for the fishermen, too. Kelp needs sea otters. If otters were allowed to spread, fishermen would gain because kelp forests provide a home for valuable fish and shellfish In the early 1990s, there were only about 1,500 California sea otters. Nearly all of them had been wiped out in the 1800s. They were the victims of fur hunters. Kelp forests began to disappear as well. Since the 1930s, sea otters have been protected and their numbers have begun to grow The loss of the kelp forests was probably caused by sea urchins. Sea otters like to eat sea urchins, while sea urchins like to eat kelp. If there are no otters, the sea urchins grow in numbers and eat all the kelp. This in turn destroys the habitat of th shellfish, so the fishermen suffer, too. Kelp forests are underwater areas with a high density of kelp. They are recognized as one of the most productive and dynamic ecosystems on Earth.Mann, K.H. 1973. Seaweeds: their productivity and strategy for growth. Science 182: 975-981. Smaller areas of anchored kelp are called kelp beds. Kelp forests occur worldwide throughout temperate and polar coastal oceans. In 2007, kelp forests were also discovered in tropical waters near Ecuador.Graham, M.H., B.Phi. Kinlan, L.D. Druehl, L.E. Garske, and S. Banks. 2007. Deep-water kelp refugia as potential hotspots of tropical marine diversity and productivity. Proceedings of the National Academy of Sciences 104: 16576-16580. Physically formed by brown macroalgae of the order Laminariales, kelp forests provide a unique three-dimensional habitat for marine organisms and are a source for understanding many ecological processes. Over the last century, they have been the focus of extensive research, particularly in trophic ecology, and continue to provoke important ideas that are relevant beyond this unique ecosystem. For example, kelp forests can influence coastal oceanographic patternsJackson, G.A. and C.D. Winant. 1983. Effect of a kelp forest on coastal currents. Continental Shelf Report 2: 75-80. and provide many ecosystem services.Steneck, R.S., M.H. Graham, B.J. Bourque, D. Corbett, J.M. Erlandson, J.A. Estes and M.J. Tegner. 2002. Kelp forest ecosystems: biodiversity, stability, resilience and future. Environmental Conservation 29: 436-459. However, the influence of humans has often contributed to kelp forest degradation. Of particular concern are the effects of overfishing nearshore ecosystems, which can release herbivores from their normal population regulation and result in the over-grazing of kelp and other algae.Sala, E., C.F. Bourdouresque and M. Harmelin-Vivien. 1998. Fishing, trophic cascades, and the structure of algal assemblages: evaluation of an old but untested paradigm. Oikos 82: 425-439. This can rapidly result in transitions to barren landscapes where relatively few species persist.Dayton, P.K. 1985a. Ecology of kelp communities. Annual Review of Ecology and Systematics 16: 215-245. The implementation of marine protected areas (MPAs) is one management strategy useful for addressing such issues since it may limit the impacts of fishing and buffer the ecosystem from additive effects of other environmental stressors.