Meeting Abstract

49.6  Jan. 6  Attachment strengths of settling coral planulae. HADFIELD, M. G.*; DUBUC, T.; TRAN, C; University of Hawaii at Manoa; University of Hawaii at Manoa; University of Hawaii at Manoa hadfield@hawaii.edu

The larvae of reef-forming corals must recruit to a world characterized by great surface complexity and turbulent water flow generated by ocean waves. Utilizing a precision turbulent flow apparatus, we have examined the attachment strength of planulae of the Hawaiian coral Pocillopora damicornis under conditions of set flow velocities. We have found that during early stages of attachment, when larvae have formed only initial mucus attachments to surfaces but have not initiated metamorphosis, resistance to removal is significant; they are not washed off by shear forces below about 15 Pascals. However, within 10 � 12 hours, metamorphosis has commenced and attachment strengths are considerably greater; maximum shear forces generated in the flow cell (50 � 100 Pa) either do not remove the newly settled individuals or do so only by physically damaging them. Additionally, preliminary measurements suggest that gregarious settlement, where two or three individuals attach to a surface in contact with each other, endows the settlers with significantly increased resistance to removal by fluid-shear forces. Together, these data indicate that planulae of P. damicornis are capable of making rapid and very strong attachments to reef surfaces and remain there under flow rates that occur under typical conditions on Hawaiian coral reefs.