Can native sessile species resist the settlement of the orange cup coral, Tubastraea coccinea, on hard substrate communities of Bonaire, Netherlands Antilles?
Tubastrea coccinea is an invasive coral species found on the reefs of Bonaire. These corals are typically seen at various densities (up to 80% m-2) on hard, vertical substrata suggesting that biotic resistance could be one possible biological factor preventing settlement of T. coccinea elsewhere (e.g.,,, horizontal substrata). The impact potential competitors have on the successful invasion, recruitment and growth of T. coccinea was experimentally assessed by establishing replicated 15 x 15 cm plots of substrata already inhabited by single species or combinations of native species (0-3 and 3 seeded with adult T. coccinea) at the Harbor Village jetty, Kralendijk, Bonaire, which had the necessary vertical substrata. Monitoring occurred over a period of three weeks to assess percent cover change of the studied organisms. Additionally 15 vertical, 5 m transects were run to evaluate mean percent cover of all sessile species that inhabited the surveyed locations for a general representation of species diversity at the jetty. T. coccinea was not observed to settle in any of the experimental plots nor did the seeded adult conspecifics show any evidence of growth or recruitment. Observational data indicated that an algal turf had the highest mean percent cover, but in areas around T. coccinea, algal turf percent cover decreased by almost 20%, suggesting competition between the two organisms. No firm conclusions could be drawn about T. coccinea recruitment or growth, but results suggested that the presence of an invasive species may negatively affect the growth of native species when they are found in close proximity to it.