Coral Reefs

, Volume 29, Issue 2, pp 347–360

Geomorphology and benthic cover of mesophotic coral ecosystems of the upper insular slope of southwest Puerto Rico

  • C. Sherman
  • M. Nemeth
  • H. Ruíz
  • I. Bejarano
  • R. Appeldoorn
  • F. Pagán
  • M. Schärer
  • E. Weil
Report

DOI: 10.1007/s00338-010-0607-4

Cite this article as:
Sherman, C., Nemeth, M., Ruíz, H. et al. Coral Reefs (2010) 29: 347. doi:10.1007/s00338-010-0607-4

Abstract

The upper insular slope of southwest Puerto Rico is defined as extending from the shelf break at ~20 m water depth down to a depth of ~160 m where there is a pronounced change in geomorphic character and the basal slope begins. The upper slope is divided into two geomorphic zones separated by a pronounced break in slope gradient at ~90 m water depth. Descending from the shelf break, these are Zone I (20–90 m) and Zone II (90–160 m). As orientation of the shelf margin changes, geomorphology of Zone I shows systematic variations consistent with changes in exposure to prevailing waves. Within Zone I, exposed southeast-facing slopes have a gentler gradient and lower relief than more sheltered southwest-facing slopes, which are steep and irregular. Mesophotic coral ecosystems (MCEs) are largely restricted to Zone I and concentrated on topographic highs removed from the influence of active downslope sediment transport. Accordingly, MCEs are more abundant, extensive and diverse on southwest-facing slopes where irregular topography funnels downslope sediment transport into steep narrow grooves. MCEs are more sporadic and widely spaced on southeast-facing slopes where topographic highs are more widely spaced and downslope sediment transport is spread over open, low-relief slopes inhibiting coral recruitment and growth. Relict features formed during preexisting sea levels lower than present include deep buttresses at ~45–65 m water depth and a prominent terrace at ~80 m. Based on correlations with existing reef accretion and sea-level records, it is proposed that the 80-m terrace formed during the last deglaciation ~14–15 ka and subsequently drowned during a period of rapid sea-level rise associated with meltwater pulse 1A at ~14 ka and deep buttresses at ~45–65 m formed between ~11.5 and 13.5 ka and then drowned during a period of rapid sea-level rise associated with meltwater pulse 1B at ~11.3 ka.

Keywords

Insular slopeGeomorphologyMesophotic coral ecosystemRelict reefPuerto Rico

Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  • C. Sherman
    • 1
  • M. Nemeth
    • 1
  • H. Ruíz
    • 1
  • I. Bejarano
    • 1
  • R. Appeldoorn
    • 1
  • F. Pagán
    • 1
  • M. Schärer
    • 1
  • E. Weil
    • 1
  1. 1.Department of Marine SciencesUniversity of Puerto Rico-MayagüezMayagüezUSA