Award: OCE-1029515

Sponges are now the dominant organisms on most Caribbean coral reefs. This project was a renewal of a very successful investigation of the chemical ecology of Caribbean reef sponges, a group whose taxonomy and chemical defenses (unusual chemical compounds that taste bad to predators) are well described. Building on past work, the community of sponges and sponge predators (angelfishes and parrotfishes) was surveyed on coral reefs across the Caribbean, at sites ranging from heavily overfished to protected marine reserves. High predator abundance correlated with high abundance of chemically defended sponge species, but overfished reefs with few predators were dominated by undefended sponge species, which grow or reproduce faster than defended sponge species. Further, these overfished reefs had 3 times more overgrowth and smothering of reef-building corals by sponges. Sponge growth experiments revealed that sponges were not limited by the amount of particulate food in the seawater around them, but they were strongly limited by the presence of sponge-eating fishes. The greatest INTELLECTUAL MERIT of this project was the clear establishment of top-down (predatory) control of sponge communities across Caribbean reefs. This result has transformed our understanding of coral reef ecology, and provided clear scientific evidence for the indirect harm to endangered reef-building corals caused by overfishing. The results of this project further justify marine protected areas on Caribbean coral reefs. The BROADER IMPACTS of this project were (1) the advancement of STEM education through the training of 3 PhD students, 4 MS students, and 5 undergraduate students at UNCW, (2) international collaboration fostered among students and faculty during 3 UNOLS research cruises in the Bahamas and Mexico, and (3) high-impact, quantifiable public outreach programs developed through an online photographic key to the sponges of the Caribbean (spongeguide.org), 2 submissions to the Ocean 180 video challenge, submission of a lesson plan on giant barrel sponges to Skype in the Classroom, and development of an outreach YouTube channel (Pawlik Lab) that gives the public the visual experience of undersea research. Last Modified: 08/04/2015 Submitted by: Joseph R Pawlik