Effects of Light Dynamics on Coral Spawning Synchrony

Abstract

Synchrony of spawning in many hermatypic corals, typically a few nights after the full moon, is putatively dependent on solar and lunar light cycles in conjunction with other possible cues such as tides and temperature. We analyze here the contributions of separate components of light dynamics, because the effects of twilight and lunar skylight on coral spawning synchrony have previously been conflated and the alternative hypothesis that these components have differential contributions as proximate cues has not been tested. Moonlight-dependent changes in spectra during twilight, rates of decreasing twilight intensities, and changes in lunar photoperiod were experimentally decoupled using programmed light-emitting diodes and compared for their separate effects on spawning synchrony in Acropora humilis. Effects on synchrony under the control of synthetic lunar cues were greatest in response to changes in lunar photoperiod; changes in light intensities and spectra had lesser influence. No significant differences among treatment responses were found at the circa-diel time scale. We conclude that spawning synchrony on a particular lunar night and specific time of night is a threshold response to differential periods of darkness after twilight that is primarily influenced by lunar photoperiod and secondarily by discrete optical components of early nocturnal illumination.

Reproductive biology and larval development of the scleractinian coralsFavites colemaniandF. abdita(Faviidae) in northwestern Philippines

“…Majority of colonies spawned 1-3 days before the last quarter phase (4-6 days after full moon). Most of the documented in situ spawnings of corals occurred in the period 4-7 nights after the full moon (Boch et al 2011). The observed lunar pattern in this study is similar to the gamete release of other faviid species (Kojis & Quinn 1982;Van Veghel 1994;Mendes & Woodley 2002;Guest et al 2005a;Mangubhai 2009).…”

“…Split-spawning pattern across lunar phases was observed in faviid species in Thailand (Kongjandtre et al 2010), but this pattern was not recorded in the present study. It seems that the synchrony of spawning in this study, which occurred on the same lunar phase, may depend on some mechanisms that has lunar dependence such as lunar light or tidal cycle (Boch et al 2011).…”

Inducing broadcast coral spawning ex situ: Closed system mesocosm design and husbandry protocol

“…reading from the seasonal table and through initial calibration, lunar phases were replicated. External light has been shown to influence spawning timing (Boch et al., ; Kaniewska et al., ; Vize, Hilton, & Brady, ); therefore, to prevent this disruption to spawning timing and synchrony with predicted wild dates, the Radion LED lighting rig was boxed‐in on the sides, back and top with 5 mm black mdf fitted into an aluminum frame (Figure u). Integrated blackout blinds housed within the front of the aquarium framework (Figure v) were then drawn 30 min before sunset, facilitating the artificial control of the nocturnal light environmental.…”

“…Several factors have been proposed to drive the seasonal timing of gametogenesis including insolation (Penland, Kloulechad, Idip, & Van Woesik, ), sea surface temperatures (SST) (Harrison et al., ; Keith et al., ), regional wind fields (Van Woesik, ), tidal rhythms, and seasonal patterns in rainfall (Mendes & Woodley, ). Environmental rhythms related to the lunar cycles are undoubtedly involved in determining the date of the spawning (Babcock et al., ), and diel light cycles have been shown experimentally to drive the actual timing of such spawning events (Boch, Ananthasubramaniam, Sweeney, Doyle, & Morse, ). Studies suggest that spawning timing may be driven by a light‐mediated biological process which reacts to the differential shift of darkness post‐twilight and premoonrise (Boch et al., ; Brady, Willis, Harder, & Vize, ; Kaniewska, Alon, Karako‐Lampert, Hoegh‐Guldberg, & Levy, ), and at a secondary level to changes in spectral dynamics of twilight and lunar phases (Boch et al., ; Sweeney, Boch, Johnsen, & Morse, ).…”

Transcriptome dynamics over a lunar month in a broadcast spawning acroporid coral

“…A previous study by Boch et al . () demonstrated that constant spectra lunar lighting timed and intensity matched to local conditions can direct normal broadcast spawn timing in Acropora humilis . A separate study (Mayfield et al .…”