Marine Biology

Nekton

      Nekton is active swimmers that use diverse means to propel themselves through the water. Some species swim using fins, tails, or flippers. Other species, such as cephalopods, move by shooting out jets of water, known as jet propulsion. Nektonic species include fish, octopus, sea turtles, whales, seals, penguins, and many others. Many nektonic species eat high in the food chain, although there are plankton-eating species (e.g., some fish) and herbivorous species (e.g., sea turtles) in addition to carnivorous ones (e.g., seals and killer whales). In the aphonic zone, there are only heterotrophic organisms that are supported mostly by organic material that rains down from the euphonic environments above. These animals live in darkness, with the exception of light produceing animals  (bioluminescentones).. It is common for sea creatures (especially animals living  is the intermediate depths) to house luminescent bacteria within their tissues, which are able to produce light for communication, as a lure to attract prey, or to light their bottom surface to conceal their silhouette against the dimly lighted  background from above. Anglerfish are deep-sea predators that attract prey near their mouths by dangling a bioluminescent lure in front of their head. The density of organisms in the deep sea is low. Because of this low density, a long period of time can pass between meals, or between encounters with the opposite sex. To deal with the problem of infrequent meals, deep-sea creatures are often gigantic compared to shallow-water relatives. Large size allows for storage of food reserves that sustain the animals between meals. Predatory fish also have large mouths and stomachs that allow them to take full advantage of any meal, regardless of size.