The average depth of the ocean is over two miles, with the greatest known depth being just over seven miles in the Marianas Deep of the western Pacific. It is this very abundance of water that makes life possible, and therefore makes Earth different from all other planets. By the process of photosynthesis. Phytoplankton, tiny one-celled plants, floating on the ocean s surface provide the basis for the web of life for water and land animals by making food from the sun s energy and generating oxygen. These interconnections can be shown in the form of a food chain where lines and arrows are drawn between predators and prey.
Food webs are often complex, with animals eating more than one prey item.
When a particular prey becomes scarce, the predator may still survive by eating the alternate food item. Many food webs, however, are fragile, and the removal of even one link in the web may ultimately result in the collapse of the entire food web. Without upwelling, the phytoplankton which is the base of the food chain cannot bloom, zooplankton cannot flourish, clams then cannot find enough to eat, and ultimately the shorebirds will have to concentrate on some other food item, move to another beach, forego reproduction that year, or starve. Human hazards to marine life are also potentially disruptive to the food web. Pollution from oil spills may coat shorebirds, so that they are no longer able to keep warm.