In May 2006, divers searching for invasive species discovered a mat of marine bacteria covering a stretch where all normal sea life was dead. The mat dissipated five months later. Jan Newton, oceanographer at the University of Washington, said it was important to note that Hood Canal has had very low oxygen for a long time. Similar mats have been found near Tacoma, Washington; San Diego, California; New York City; and New Orleans, Louisiana. Hypoxia and its detrimental effects on fish have been documented in Hood Canal since the 1970s. But hypoxia's impacts on the area's wildlife have been more significantly linked to growing urbanization along the coast. A recent study determined DO content, oxygen saturation, of the Sound's Main Basin to consistently stay around 5 mg/l from the 1950s up through 2005. DO concentration in Hood Canal, however, was identified to have dramatically decreased from 5–6 mg/l in the 1950s to less than 0.2 mg/l in the twenty-first century. As of 2000, the National Research Council defined hypoxia to occur at a DO level of <2 mg/l—making Hood Canal's current 0.2 mg/l composition far below life-sustaining conditions.