Background information; by edgardowelelo@yahoo.com, Master of the Game
In total, water covers just over 70 per cent of the Planet Earth’s surface, most of it being distributed between just five (5) huge Ocean basins. The largest of these is the Pacific and its associated seas, followed by the Atlantic, and the Indian Ocean, the Southern Ocean and the Arctic Ocean. Around and within these wide expanses of water lies a rich variety of habitats that support a huge diversity of life.
OCEAN HABITATS
On land it is relatively easy to pinpoint clear vegetation belts which show similar characteristics, but it is much more difficult to follow this principle with the OCEANS. Currents, wind patterns and changes in salinity all mean that many characteristics can be localised and variable. Nevertheless, it is possible to distinguish a number of general marine biological zones which are related to temperature. Warm water populations exist where the surface temperatures are about 18 – 20°C (67 – 69°F). Here there is a great diversity of species, but often the waters are relatively poor in nutrients, hence the total numbers of creatures may be quite low. On coral reefs, for example, the ecosystem is tightly organized and nutrient recycling is of the utmost efficiency in order to make the most of the small amount of nutrients available. Cold water populations are found in the Arctic and Southern Oceans, where surface temperatures lie between 5°C (40°F) and just below 0°C (32°F). Here, there is a low species diversity – for example Antarctica has no land mammals, no freshwater fish and few plants – but there is still an extraordinary abundance of life. In spring, the ice melts and phytoplankton blooms with astonishing speed, attracting a host of other creatures that come to feed. Between the tropical and the cold – water areas lie the temperate regions where the surface temperatures are between 5 and 18°C (40 and 67°F) and the productivity of the Oceans is markedly influenced by the seasons because of the enormous variation in the amount of light energy. In midwinter the temperate regions can see as little as four (4) hours of sunlight, while in the summer they can experience as many as 20 hours. When the light is most abundant, plants grow in profusion and temperature layers form in the Ocean: both have a significant influence on marine life. The Ocean can also be divided into categories according to the distance from land and the depth beneath the surface. From the coasts, where the habitat is constantly changing due to the ebb and flow of the tide, to the enormity of the open Ocean and the mysterious darkness of the deep Sea each of these environments is blessed with a diverse range of life that is uniquely adapted for its particular habitat. The creatures of tidal areas have to cope with periodic exposure to air, those of the open Ocean need speed and endurance, whilst in the deep, marine life has evolved to endure extraordinary pressures and long months of starvation.
