In this paper, Rasher and his PhD advisor Mark Hay addressed a long-standing debate over whether increases in seaweeds on coral reefs are a cause or consequence of coral decline. Using a combination of field competition experiments and chemical bioassays, Rasher demonstrated that numerous common seaweeds in the Caribbean Sea and tropical Pacific Ocean directly damage corals when in direct contact, and do so by chemical warfare. These poisonous seaweeds produce surface-associated chemicals that are transferred to corals by direct contact - causing localized coral bleaching, reduced photosynthesis, and even coral tissue death after only 20 days of contact. However, using field feeding assays Rasher also found that many of these harmful seaweeds are rapidly consumed when transplanted onto reefs protected from fishing, but are rarely grazed on overfished reefs. Together, Rasher and Hay's paper suggests that seaweeds do play a critical role in the decline of coral reefs, and may help to explain why so few overfished reefs show signs of significant recovery.