Sea urchin exclusion experiments on an offshore petroleum platform, northwestern Gulf of Mexico

Abstract

Caging experiments were utilized to investigate the effects of sea urchin grazing on the fouling
community. By excluding sea urchins, it was possible to monitor certain areas of the platform
fouling community in the absence of sea urchin grazing. Three caging treatments (cages, fences,
open) were employed in the experiment. Cages excluded all grazers, fences excluded sea urchins
but allowed access to fishes, and open areas served as controls. Experimental plots were monitored
biweekly, using digital photography.

Presently, results seem to indicate that control plots showed a community progression intermediate
between caged and fenced areas. Such evidence suggests that overall change in the platform
community during the study period may be a confounding factor in this research; however, it would
be unwise to draw any decisive conclusions until all experimental data can be analyzed. Data from
intermediate sampling periods (09 August, 19 August) has yet to be investigated and may contain
some important information. Furthermore, statistical analysis of photographic data will be necessary
to determine if observed changes in percent cover of organisms is statistically significant.