Scleractinian Coral Recruitment to Reefs Physically Damaged by Ship Groundings

Southeast Florida reefs are impacted by a number of stress factors, among which ship groundings are one of the most physically damaging. In particular, portion of Florida reef tract located near Port Everglades in Broward County has been severely damaged by ship groundings. In 2004, extensive physical damage of more than 30,000 m2 was caused by the groundings of two large cargo ships, the MV Eastwind and MV Federal Pescadores. The present study was designed to examine differences in the recruitment patterns of scleractinian corals and pioneering benthic communities settling to these physically impacted sites compared to undamaged reef sites. Coral recruitment and non-coral benthic settlers were measured on unglazed terracotta tiles deployed for a period of one year from February 2007 to February 2008 at five different locations: three control sites (including a high coral cover site) and the two ship grounding sites. Colony morphology and two genetic markers: mitochondrial cytochrome oxidase subunit I and cytochrome b were used to identify the coral recruits. A whole genome amplification kit (REPLI-g, Qiagen) was used to obtain sufficient amounts of DNA from small coral spat. The image analysis software Coral Point Count with the Excel extension was used to quantify the percent cover of major benthic invertebrate and algal functional groups. Results revealed very low diversity of coral recruits and low recruitment rates (0.5-2.7 recruits m-2 yr-1), suggesting a low potential for recovery of the damaged areas. Other non-coral benthic groups, including turf algae, barnacles, sponges, tunicates and bryzoans, were found to proliferate and occupy almost the entire tile substrate, suggesting possible coral recruitment inhibition by space preemption or coral recruit mortality by overgrowth. Turf algae which comprised up to 50% of the total cover were the most dominant group settling to the tiles. This dominance of algae on the tiles reflects a similar pattern of algal dominance present on the reef system along the Florida coast