Streaks of milky blue and turquoise tinted the waters off of the southern tip of South Africa in late December, 2013 - visible evidence of teeming life within the Indian Ocean. The sinuous lines mark blooms of phytoplankton, where millions of microscopic plant-like organisms have burst into life and float freely in the waters, providing the basis of the marine food change.
The waters off of South Africa contain a rich diversity of marine life, with about 20% of the world marine fish fauna found in the West Indian Ocean. A rich array of dolphin, whales, birds, seals and other marine animals also thrive in and around these waters. Phytoplankton blooms provide food for most of these, either directly (zooplankton and some whales, for example) or indirectly, as the food of many prey species. Because phytoplankton contains chlorophyll, such blooms remove carbon from the ocean by the process of photosynthesis – they use the energy of the sun to turn carbon dioxide into sugars.
While many blooms are beneficial, they can also cause problems. When blooms become too large, they can cause low-oxygen dead zones as massive amounts of dying organisms sink and decompose. Also, some species contain neurotoxins, which affect marine mammals, as well as humans through direct contact, breathing or through the food chain. Such toxic blooms are called "red tides".