Soft coral reproductive phenology along a depth gradient: Can “going deeper” provide a viable refuge?

Ronen Liberman*, Tom Shlesinger, Yossi Loya, Yehuda Benayahu

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

Many species across a wide range of taxa and habitats display phenological shifts and differences in response to both environmental gradients and climate change. Moreover, the wide-scale decline of numerous ecosystems is leading to increasing efforts to identify zones that might serve as natural refuges from various disturbances, including ocean warming. One such refuge was suggested to be that of the deep coral reefs, but whether depth can provide coral populations with a viable and reproductive refuge remains unclear. Given the global coral-reef degradation and the key role that corals play as ecosystem engineers, their reproductive ecology has been widely studied. A particular knowledge gap nonetheless exists regarding coral reproductive phenology along a depth gradient. Filling in this gap may uncover the environmental cues that regulate coral reproduction, leading to better predictions of population connectivity, and their possible responses to climate change and other environmental changes. Here, using long-term in situ observations of the soft coral Rhytisma fulvum's reproductive activity along its entire depth range (0–45 m), we examined the relationship among several environmental factors and the coral's reproductive phenology and activity over five successive annual breeding seasons. Compared with the shallow depths, a lower number of reproducing colonies was found in habitats deeper than 30 m, highlighting possible constraints on coral reproduction at the deeper end of their range. Our results further revealed that an increase in seawater temperature over 1–2-day intervals during the breeding season correlated with the onset of reproductive activity along the depth gradient, leading to different reproductive periodicities in different depths. These differences suggest that differential temperature regimes and reproductive timing across depth may create intraspecific temporal reproductive segregation, possibly reducing connectivity among populations along a depth gradient. Moreover, we found high variability among years in both the timing of breeding activities and in the level of reproductive synchrony among corals from different depths. Overall, our study questions whether depth can provide a long-term and viable refuge for corals in the face of global environmental changes.

Original languageEnglish
Article numbere3760
JournalEcology
Volume103
Issue number9
DOIs
StatePublished - Sep 2022

Funding

FundersFunder number
Rieger Foundation
IUI
Israel Taxonomy Initiative
Interuniversity Institute for Marine Sciences in Eilat
Horizon 2020
Horizon 2020 Framework Programme634674

    Keywords

    • Octocorallia
    • Red Sea
    • Rhytisma
    • coral reproduction
    • mesophotic coral ecosystem
    • seawater temperature
    • surface brooding

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