Larval behavior and settlement dynamics of a ubiquitous Caribbean octocoral and its implications for dispersal

Biological traits of marine benthic species have important effects on the extent of larval dispersal. Yet, empirical characterizations of many of these traits, which are critical data for parameterizing models of larval dispersal, remain scant for most species, particularly corals. We characterized spawning, larval development, settlement dynamics, survival, and propagule buoyancy and vertical swimming behavior of the Caribbean octocoral Antillogorgia americana. Spawning of A. americana in the Florida Keys, USA, was associated with the lunar cycle and occurred over 2 separate events following the full moon of November 2014. Despite the rapid larval development (2-3 d) and onset of competency to settle at ∼4 d, most larvae delayed settlement for an extended period of time, with 50% of the cohort transitioning to the benthos by 36 d, and 95% by 58 d. Larval mortality in the laboratory was surprisingly low (10% over 58 d). Egg buoyancy and larval swimming behavior were highly variable both within cohorts and over time. In particular, there was a significant decrease in propagule buoyancy during embryogenesis, which was gradually offset by the increase in larval swimming activity (∼3-4 d). Most larvae had negative geotactic behavior for up to 20 d. The observed capacity to delay settlement suggests the dispersal potential of A. americana is high, which undoubtedly contributes to its broad distribution in the Caribbean. Importantly, our results underline the inherent variation observed in these larval traits, particularly swimming behavior, which has potentially important implications for dispersal and may improve our understanding of connectivity.