Photographic monitoring of benthic biota at Stetson Bank, Gulf of Mexico

Abstract

The percent cover of benthic biota was measured at Stetson Bank, Gulf of Mexico yearly between 1993 and 1999. This study was the first temporal monitoring effort at Stetson Bank and will subsequently serve as a base line for all future work. In addition, this was the first application of coral reef monitoring techniques to a hard bottom reef dominated by sponges in the northwestern Gulf of Mexico. Individual photostations were found to be significantly different, indicating complex microstucture at the 2 m² level. Overall the photostations were dominated by Millepora alcicornis (30 %), various poriferans (30 %), and exposed substrate (30 %). No overall temporal changes occurred at Stetson Bank during the period of the study. Two color segmentation methods were compared to a manual segmentation method and the traditional point count method in terms of estimating percent cover of benthic organisms. All four methods provided similar estimates of percent cover when applied to three photostations for each of nine sampling periods. Interactive color segmentation provided a digital record of organism boundaries and color data. Point counts were more time efficient for collection of percent cover data, but provided no other data.