Project: The impact of Hurricane Maria on the mesophotic reefs of southwest Puerto Rico

NSF Award Abstract:

Major Hurricane Maria, on 20 September 2017, delivered a devastating blow to the island of Puerto Rico. Both terrestrial and marine ecosystems were heavily impacted.  This powerful and rare weather event provides an opportunity to examine the effects of extreme physical forces on coral reefs. The research team will concentrate on the mesophotic reefs or "twilight zone reefs", which rival shallow water coral reefs in diversity and beauty.  Mesophotic coral ecosystems are reefs found between 30 and 100 m depth, and are thought to serve as refugia for the declining shallow water coral reefs because they are further removed from anthropogenic and natural disturbances. Hurricane Maria is one of those rare, high-magnitude disturbance events that could affect even those deeper, mesophotic reefs. The investigators are positioned with pre-deployed oceanographic instruments and previously-collected ecological data to measure the effects of Hurricane Maria on the presumably sheltered, mesophotic reefs. The investigators will document the hurricane effects on the reef communities by comparing photographic data from pre-established transects at shallow and mesophotic reefs. Misplaced corals will be used to test the capacity of extreme weather events to shape the population connectivity of key species. Radioisotope analysis will be used to identify the origin of sediments collected from the mesophotic reefs. The investigators will interpret all data described above in light of the physical conditions that were recorded before, during, and after the passage of Hurricane Maria. The project will involve the collaboration of an interdisciplinary team of five researchers and a graduate student from a Hispanic-serving Institution. The investigators will disseminate the results to Natural Resources Management Agencies and will use local media outlets and organize outreach events to inform local communities about the effects of hurricanes on coral reefs.

The landfall of major Hurricane Maria on the south coast of Puerto Rico provides a unique opportunity to examine its impacts on an insular shelf margin reef ecosystem (~25 to 70-80 m depth).  The powerful weather system likely triggered major off-shelf transport of sediments, turbidity, terrigenous material and benthic organisms, affecting entire shelf margin benthic ecosystems. It also constitutes a unprecedented natural experiment where coral colonies were likely dislodged and transplanted to deeper areas, allowing to test various hypotheses related the deep refugia model and connectivity between shallow and mesophotic coral reefs. The investigators will assess the ecosystem stability that underlies the deep-reef refuge hypothesis of the insular-slope mesophotic reefs by: a) repeating high resolution photo-transects at pre-established sites at shallow and mesophotic stations, b) documenting the type and extent of displaced/damaged benthic taxa, c) examining the possibility of hurricane-assisted vertical connectivity through the displacement of shallow corals to deeper depths, d) measuring the potential recent input of terrigenous material to mesophotic depths by radioisotope analysis of sediment samples and, e) relating all the above observations to actual physical conditions, which were measured in situ before, during, and after Hurricane Maria.