Szmant, A. M., Miller, M. W.

Settlement preferences and post-settlement mortality of laboratory cultured and settled larvae of the Caribbean hermatypic coral Montastraea faveolata and Acropora palmata in the Florida Keys, USA

2006

Proceedings of 10th International Coral Reef Symposium, Okinawa, Japan, June 28-July 2, 2004

43-49

"The broadcast spawning massive corals, Motastraea faveolata and Acropora palmata, are two of the most important hermatypes in the Caribbean. They are common as large colonies up to several meters high (former) or in large patches (latter), but infrequently found as young recruits. These species have suffered major tissue loss and mortality in recent decades due to bleaching and disease. Thus, it is important to understand processes that will affect their regenerative abilities, especially sexual recruitment. Gametes bundles were collected ruing annual mass spwanings, and larvae raised in the laboratory to early competency (ca. 4 to 8 days). Batches of larvae were given naturally aged limestone plates on which to settle, and settlement patterns mapped onto data grids within one to two weeks after settlement. The plates were attached to natural reef substrate on two reefs offshore of Key Largo FL, and resurveys monthly for up to 3 months. Newly settled spat (ca. 0.4 to 0.5 mm in diameter for M. faveolata and 0.8 mm for A palmata) are difficult to observe without a microscope. Larvae of M. faveolata preferred to settle on the underside-conditioned surfaces of plated regardless of plate orientation in the laboratory during settlement (i.e. they settled on "under-surfaces" even when these were oriented upwards towards ligh), demonstrating a strong settlement attraction to fouling organisms typical of cryptic reef surfaces. Some (ca. 25%) settled directly on crustose coralline red adgae (CCA) but most settled 1 cm or more away from CCA. Settlement was statistically aggregated, indicating either that newly settled larvae attract others to settle near them, or that there are substrate micro-patches with strong settlement induction ability. Field survivorship was low: 25% after 1 month; 0 to 2% after 2.5 months, and 0 after 10 months. If such survivor hip rates are typical, it will take very high densities of settlement for there to be any hope of long-term recruitment success. In contrast, larvae of A. palmata preferentially settled on the upward-facing side of the settlement plates, regardless of substrate composition but had similar proportional settlement (25%) directly on CCA. Field survivorship (3% after 9 months) was much more higher than of M. faveolata, and as high as that of spat of two brooding species, suggesting that sexual reproduction may play a greater role in the population recovery of this fast growing species."

coral; larval culture; planula; settlement preferences; Montastraea faveolata; Acropora palmata; post-settlement survivorship; crustose cralline algae

FY2005 CRCP Project ID 1066; Project Title: Ecological Approach to Coral Reef Restoration; Principal Investigator: Margaret Miller