Title: SEASONAL VARIABILITY OF MESOPHOTIC BENTHIC COMMUNITIES AT TWO SITES AND DEPTHS OFF LA PARGUERA, PUERTO RICO

Abstract: Coral reefs are dynamic environments, and rapid changes in benthic cover can occur in response to environmental conditions or biological interactions. Mesophotic coral ecosystems are thought to be more stable than shallow coral reefs because it is assumed that variations in environmental parameters (e.g., temperature) are reduced at depth, and MCEs are buffered by depth or distance from shore from surface-based disturbances. We investigated changes in percent benthic cover at quarterly intervals over one year at two mesophotic sites along the insular slope: El Hoyo (low rugosity, low slope) and Hole-in-the-Wall (high rugosity, high slope). Data were obtained from two replicate high-resolution phototransects conducted at each of two depths (50, 70 m) at each site. Nonmetric multidimensional scaling showed that site and depth combinations tended to cluster separately, with individual transects within site/depth typically having less than 80% but greater than 60% similarity over space and time. Temporal trends were similar across sites and depths. Dominant changes occurred among the algae, particularly Dictyota and Schizothrix, with the former oscillating from near 0 to over 30% cover, peaking in March and September. The latter species showed a general increase over time. The magnitude of change was higher at 50 m. The degree and magnitude of variability at mesophotic depths was less than previously documented at 30m depth. While temporal variability declines with depth, relative impacts must account for potential reductions in productivity as well.

Authors: Appeldorn RS, Ballantine DL, Carlo M, Nemeth MI, Ruiz HJ, Sherman C, Weil E

Presentation: Oral

Session: 29

Date: 06/22/16

Time: 14:00

Location: 308 A/B

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