The Marine life

Life began in the ocean, to this day it remains home to the majority of Earth's animals and plant life. Raging from single-celled organisms to the giants of the sea such as the blue whale. Most of the ocean's plant life consists of microscopic algae called phytoplankton that float at the surface and through photosynthesis produce about half of the oxygen that humans and all other terrestrial creatures breathe. The deepest reaches of the ocean were thought to be devoid of life, but biological hotspots appear around places like hydrothermal vents and elsewhere in the deep sea. These chimney-like structures spew gases and mineral-rich water from beneath the Earth's crust. Tube worms, clams, and mussels gather around the vents to feed on heat-loving bacteria. Other fish, octopuses, squid, eels, dolphins, and whales ply the open waters while crabs, lobsters, starfish, oysters, and snails crawl and scoot along the ocean bottom. Creatures like jellyfish lack their own way to get around and are mostly left to the whim of the wind and currents. Mammals like otters, walruses, and even polar bears also depend on the ocean for their survival and dip in and out as their biology requires.

Colonies of polyps form coral reefs as they die. The reefs are mostly found in shallow tropical waters and are home to a brilliant mosaic of polyps, plants, and fish. Coral reefs are also visible victims of human activity. Global warming, siltation, pollution, and other phenomena are stressing the corals to death, and over-zealous fishers net more food than the reefs can restore.

Human Impact on the Oceans

Human activities impact nearly all parts of the ocean. Lost and discarded nets continue to lethally snare fish, seabirds, and marine mammals as they drift. Ships spill oil and garbage and transport critters to alien habitats unprepared for their arrival. Mangrove forests are cleared for homes and industry. More than half of the U.S. population lives in coastal areas, spilling garbage and sewage into the ocean. Fertilizer runoff from farms turns vast swaths of the ocean into dead zones, including a New Jersey-size area in the Gulf of Mexico. The greenhouse gas carbon dioxide is turning ocean waters acidic, and an influx of freshwater from melting glaciers threatens to alter the weather-driving currents.