GEF

Unit 5  |  The Importance of Biodiversity 116 Bleached coral (top) indicates the death of coral ecosystems; healthy coral reefs are a vibrant aquatic life form (bottom). Intensive fishing is also threatening marine biodiversity. Modern fishing technologies, such as driftnets, seabed trawl- ing, and sonar, allow fishing fleets to capture virtually all harvestable sea creatures between the ocean surface and the sea floor. About 50 percent of all marine fish stocks are being fished beyond or near sustainable limits, while another twenty percent are depleted, putting them at risk of collapse. Heavily fished species, such as Atlantic cod, have not recov- ered successfully despite severe restrictions on their harvest. Indiscriminate fishing techniques also threaten other species, including marine mammals and sea turtles, many of which are threatened or endangered. ?  DID YOU KNOW Phytoplankton are free-float- ing microscopic plants that make up the bottom of a vast marine food web. These tiny but numerous creatures sup- port almost all ocean species and commercial fisheries, but they are threatened. According to the National Aeronautics and Space Administration (NASA), the most common phyto- plankton, called diatoms, decreased approximately 1 percent per year between 1998 and 2012, possibly due to warming temperatures. A widespread disruption in the health and size of phyto- plankton populations could trigger significant declines in marine species. Phytoplankton is critical to ecosystem health and is found in most food webs.