Settlement, colonization, and succession patterns of gold coral Kulamanamana haumeaae in Hawaiian deep coral assemblages

Abstract

The Hawaiian gold coral is a parasitic zoantharian that colonizes other deep corals and secretes a protein skeleton that over millennia can grow and more than double the original mean size of the host colony. Surveys at 6 known coral beds in the Hawaiian Archipelago found mature gold coral to be a common taxon and dominant at the geologically older sites. Fewer than 5% of the gold coral colonies seen were in the process of subsuming their host, described here as the 'midas' phase. Bamboo coral (Acanella, Keratoisis) comprised 85% of the midas colonies, with two-thirds found at the youngest site, where the mean height of bamboo coral was significantly greater than at other sites. Marked midas colonies revisited after 5 yr showed the gold coral tissue spreading across the host at an estimated rate of 2.2 ± 0.69 cm yr-1 (mean ± SD). Cross sections of mature gold coral colonies show the host averages just 9.8 cm of the stem's core, indicating that much of the host skeleton is lost when subsumed by gold coral tissue. The absence of midas colonies in a bamboo coral assemblage found growing on a 76 yr old wreck close (~1 km) to a mature gold coral patch suggests that gold coral recruitment is infrequent. This time lag between the growth of the host and the arrival of the gold coral successor is essential because otherwise the speed of the midas phase would subsume the host population faster than it could replenish.