The researchers studied preserved plankton taken from the North Sea and North Atlantic Ocean from 1958 to 2011, and found that as sea temperatures rose, so did germ levels. It's not proof of direct cause, but it's strong evidence of a link. "From long-term data, it is apparent that the level of these pathogens is rising in the ocean as a result of global warming," study author Luigi Vezzulli told Phys.org.