Carl Safina, the founder of the nonprofit Blue Ocean Institute, is proud of the work he’s done to battle overfishing in the U.S., where some species are actually on the mend. Nevertheless, he says, humans are “poised to remake the ocean into a new kind of environment”—one that might require a toxic- containment suit. Recently, Ron Johnstone, an Australian marine biologist, broke out in boils while studying sediment. He was poisoned by fireweed, a toxic cyanobacteria exploding across the globe in response to pollution.

What is the meaning of the underlined sentence. Please help.

He got a skin disease after being in the ocean.
The act of contracting some ailments is sometimes described as "breaking out." I can only think of examples that use skin ailments. You can break out in a rash, for instance. Or you can break out in hives, which is another skin ailment. Teenagers break out in zits (or 'pimples').

'Sediment' is a fancy word for 'dirt.' Emotion: smile