Marine Ecosystems continued

Animal Adaptations:

There are 120 species of mammals including whales, dolphins, porpoises, seals and sea lions which have evolved to adapt to their aquatic environment by developing small appendages (ears and flippers), a generally large size, hydrodynamic (mechanical properties of liquid) body shapes and different methods to cope with extreme changes in temperature.

The ocean provides habitat for a wide variety of animals, some of which are flying-fish, sharks, narwhals, sting-rays, whales, tarpon, tuna, sardines and jellyfish. One tiny shrimp-like animal known as the phaeton is a key species floating freely in the ocean. Many fish and marine mammals feed on it, and in turn carnivorous predators such as sharks, orcas and electric eels tear apart their prey, allowing pieces to fall to the sea floor and decompose, providing a rich fertilizer.

Fish are able to obtain oxygen through their gills, a specialized structure in which blood comes into contact with the water over a very large surface.

Animals such as flatworms, sea stars, giant isopod (wood louse) sole and flounder have adapted to living in the deepest ocean trenches where the pressure can be over one thousand atmospheres.

Mammals such as whales, dolphins, porpoises, manatees, dugong, seals, walrus, otters and even polar bears swim effortlessly through their watery environment, diving and swimming with ease. For example, the sperm whale cleans out its lungs to get rid of old carbon dioxide and load up with fresh oxygen in its swimming muscles before diving as low as 8,200 feet as it hunts for food. At this depth, the pressure is tremendous and a human would suffer from the "bends" if not properly pressurized. Sperm whales routinely hold their breath for as long as one hour before returning to the surface to repeat the process.

The watery environment is not conducive to strong vision because of light absorption, and as a result some marine mammals have evolved to rely upon echolocation. Toothed whales (dolphins, porpoises, river dolphins, orcas and sperm whales) send out a series of high-frequency clicks in the direction their head is pointing and listen to the echoes of those calls as they return from various objects in their environment. The different rates of click production are heard as barks, squeals and growls in the bottlenose dolphin. Some of the smaller toothed whales have a tooth arrangement that aids in echolocation.

Plankton converts inorganic carbon into sugars that are stored in its cells. They are in turn eaten by zooplankton, filter feeders and baleen whales. Zooplankton are eaten by small fish which in turn are eaten by salmon, tuna, seabirds, marine mammals, and so on.

Page 3> Marine Ecosystems