Title: PHYSICAL DRIVERS OF COMMUNITY STRUCTURE AND GROWTH AMONG MESOPHOTIC CORAL ECOSYSTEMS IN ST. THOMAS, US VIRGIN ISLANDS

Abstract: Mesophotic coral ecosystems (MCEs) are deep (>30m), light-dependent communities that are abundant in the northern US Virgin Islands. Compared to their shallow water counterparts, MCEs remain understudied. South of St. Thomas, mesophotic coral cover on Orbicella-dominated reefs can reach 50%, but observations of the northern shelf at similar depths (30-45 m) suggest limited coral cover. The cause and extent of these differences is unknown. Using spatially explicit observations of coral health, species abundances, and coral population densities, we compared northern shelf bank MCEs to previously studied MCEs south of St. Thomas. Overall coral cover is lower on northern MCEs and reefs dominated by Orbicella species have not been found. Factors limiting coral growth on northern MCEs may include more frequent wave disturbance as well as nutrient loading, turbidity, and thermal stress associated with upwelling. To assess if disturbance and growth are driving community structure, we collected 30 colonies each of Orbicella franksi and Porites astreoides from 27 to 47 m depths on the north and south shelves of St. Thomas. Using CT to quantify calcification, we will identify environmental factors correlated with coral growth across sites. We predict slower growth rates of mesophotic corals north of St. Thomas, corresponding to lower light conditions and more frequent disturbance. These results will identify processes that influence the structure of MCEs and, thus, help to predict their global distribution and utility as refugia.

Authors: Groves SH, Brandt ME, Enochs IC, Holstein DM, Manzello DP, Canals MF, Smith TB

Presentation: Oral

Session: 29

Date: 06/22/16

Time: 14:15

Location: 308 A/B

Back