Abstract

Based on a case study (the Anegada de Adentro Reef, Veracruz Reef System National Park, southwestern Gulf of Mexico), a method that allows quantifying a negative impact on hermatypic corals is proposed. Two photo transects of 100m length at a constant depth (to avoid differences in a coral community caused by depth) were followed. Both transects had not been previously impacted by divers. One transects is impacted by divers, and the other is without diver impact (control). The impacts were classified according to their origin: (1) by swimming, (2) by Learning on corals or standing on sand, (3) by resuspending sediments, (4) by touching corals, (5) by destroying corals or (6) by collecting organisms. Trimestral observations were performed by taking photographs each meter using a Nikon D800 camera equipped with a Nikkor 16-35mm lens at 1.5m distance from the transect. Every 5m a coral colony was selected, and photographs of a 1x1m quadrant from different angles were taken. A CPCE (Coral Point Count with Excel extensions) program was used to estimate coral coverage. Damage of the photographed colonies was recorded individually as bleaching, partial mortality, presence of diseases or syndromes and growth of algae or other benthic organisms. To identify diver impact, temporal changes along each transect and between them were compared, and possible correlations with a diver impact factor were analyzed.

Keywords: Coral reefs; Gulf of Mexico; Hermatypic corals; Impact assessment; Scuba