Acute and Chronic Effects of Large-Vessel Anchoring on Coral Reef Communities Inside a Designated Commercial Anchorage

摘要

Coral reefs provide economic and environmental services to millions of people as areas for recreation, sources of food, jobs, and shoreline protection; and are now under threat from multiple stresses (NOAA 2002). Anthropogenic impact from acute physical events such as commercial vessel grounding and anchor drags have been well documented throughout the world and southeast Florida. However little data exist on the chronic effects of large commercial vessels anchoring on reef resources. The Port Miami commercial anchorage was designated circa 1927 and was delineated over approximately 700 acres of reef resources. Anchorage use, benthic resources, and substrate composition were surveyed to understand the impact commercial vessel anchoring activities have had. Survey sites included both random sites within the anchorage to understand the cumulative chronic effect of anchoring activity, as well as targeted surveys at recently anchored sites to understand the immediate impacts of those anchoring events. Survey data were also compared to anchorage use data to understand how vessel traffic patterns influenced impact. Results indicated that there was both significant differences at acute recent impact sites and chronic impact sites. Generally, Outer Reef chronic impact sites had more evidence of chronic impacts both in the benthic community and substrate composition than Inner Reef sites. Significant differences on Outer Reef included an increase in the percent cover of small rubble, a decrease in octocoral percent cover, and a decrease in the density of larger octocoral size classes. Significant differences on Inner Reef included a decrease in the number of scleractinian species present compared to control sites.