In these very deep, high pressure ecosystems, primary productivity is fuelled by chemical compounds as energy sources instead of light (chemoautotrophy). This group of productive deep sea ecosystems include: 1) hydrothermal vents on mid-ocean ridges and volcanically active seamounts, where temperatures may reach 400°C; 2) cold seeps typically on continental slopes; and 3) large organic falls of whales or wood. These specialised environments have high biomass but low diversity of organisms including microbes, tubeworms and shrimps, many of which are locally unique.