mass supplied to the continental shelves through the world's rivers. These plumes introduce a turbidity which decreases light levels at the bottom and can affect kelp reproduction. Bottom trawling can both resuspend and bury biologically recyclable organic material, changing the flow of nutrients and carbon through the food web and thereby alter geomorphological landscapes. Ocean sediments are the sink for many persistent organic pollutants, usually lipophilic pollutants like DDT, PCB and PAH. Bottom trawling mixes these pollutants into the plankton ecology where they can move back up the food chain and into our food supply. Phosphorus is often found in high concentration in soft shallow sediments. Resuspending nutrient solids like these can introduce oxygen demand into the water column, and result in oxygen deficient dead zones. Even in areas where the bottom sediments are ancient, bottom trawling, by reintroducing the sediment into the water column, can create harmful algae blooms. More suspended solids are introduced into the oceans from bottom trawling than any other man-made source. Multiple large-scale reviews on bottom trawling have noted that there is a great need for further studies that properly examine the effects of nutrient and toxin remobilization as well as carbon cycling, in order to better estimate greenhouse gas emissions and hence the impact on climate change. Deep sea damage The Secretary General of the United Nations reported in 2006 that 95 percent of damage to seamount ecosystems worldwide is caused by deep sea bottom trawling. A study published in Current Biology suggests a cutoff of is a point which ecological damage increases significantly. Vast amounts of carbon stored in seafloor sediments risk release by bottom-trawling fishing. Current restrictions Today, some countries regulate bottom trawling within their jurisdictions: The United States Regional Fishery Management Councils limit bottom trawling in specific closed areas to protect specific species or habitat. For instance, on the United States West Coast a large Rockfish Conservation Area was created in 2002 prohibiting trawling in most areas of the coast between 75 and 150 fathoms – – to protect overfished rockfish species. In 2018, these closures were revised to allow trawling in some previously closed areas while closing new areas of sensitive habitat to bottom trawling. The Council of the European Union in 2004 applied "a precautionary approach" and closed the sensitive Darwin Mounds off Scotland to bottom trawling. In 2005, the United Nations Food and Agriculture Organization's General Fisheries Commission