Spatial patterns of coral survivorship: impacts of adult proximity versus other drivers of localized mortality

Abstract

Species-specific enemies may promote prey coexistence through negative distance- and density-dependent survival of juveniles near conspecific adults. We tested this mechanism by transplanting juvenile-sized fragments of the brooding corals Pocillopora damicornis and Seriatopora hystrix 3, 12, 24 and 182 cm up- and down-current of conspecific adults and monitoring their survival and condition over time. We also characterized the spatial distribution of P. damicornis and S. hystrix within replicate plots on three Fijian reef flats and measured the distribution of small colonies within 2 m of larger colonies of each species. Juvenile-sized transplants exhibited no differences in survivorship as a function of distance from adult P. damicornis or S. hystrix. Additionally, both P. damicornis and S. hystrix were aggregated rather than overdispersed on natural reefs. However, a pattern of juveniles being aggregated near adults while larger (and probably older) colonies were not suggests that greater mortality near large adults could occur over longer periods of time or that size-dependent mortality was occurring. While we found minimal evidence of greater mortality of small colonies near adult conspecifics in our transplant experiments, we did document hot-spots of species-specific corallivory. We detected spatially localized and temporally persistent predation on P. damicornis by the territorial triggerfish Balistapus undulatus. This patchy predation did not occur for S. hystrix. This variable selective regime in an otherwise more uniform environment could be one mechanism maintaining diversity of corals on Indo-Pacific reefs.

Detachment of Porites cylindrica nubbins by herbivorous fishes

“…tiles) exposed to local reef fish assemblages varied from 0.99–1.05%/day in the northwestern Philippines (Baria et al ), 1.39%/day on the Great Barrier Reef (Trapon et al ), to 2.5–10%/day in French Polynesia (Penin et al , ). Similarly, estimates of the mortality of juvenile corals (<5 cm diameter) and small nubbins vary from 0.35 to 5.9%/day (Fiji: 0.35–0.71%/day—Gibbs & Hay ; Palau: 2.17–3.44%/day—Gallagher & Doropoulos ; French Polynesia: 2.8–5.9%/day—Penin et al ). In contrast, previous estimates of mortality rates of transplanted coral nubbins have been typically higher than those reported in the present study (e.g.…”

Density-dependent coral recruitment displays divergent responses during distinct early life-history stages

“…Subsequently, the action of herbivorous fish grazing may have indirectly targeted individual coral settlers because indirect predation by herbivorous fish occurs on the smallest coral recruits, which are quickly avoided as their size increases [12,35,60,61]. The alternative hypothesis that aggregative settlement increases post-settlement mortality by attracting predators, as seen at high-densities of barnacle [25] and coral [62–64] recruits, is not supported by the results found in this study.…”

Mortality, Population and Community Dynamics of the Glass Sponge Dominated Community “The Forest of the Weird” From the Ridge Seamount, Johnston Atoll, Pacific Ocean

“…The species-specific mortality then enables different species to occupy these areas. Most studies testing this hypothesis are focused on shallow-water reefs, and have found no densitydependent mortality for giant barrel sponges (Deignan and Pawlik, 2015), Caribbean sponge Aplysina cauliformis (Easson et al, 2013) nor Caribbean corals (Muller and van Woesik, 2012), but density-dependent death due to corallivory has been detected in Indo-Pacific corals (Gibbs and Hay, 2015). In our study, we find that species-sensitive density-dependent mortality is likely once a density threshold was reached for Aspidoscopulia.…”

“…Within SPPA each organism is treated as a point and spatial distributions are calculated using distance measures such as pair correlation functions (PCFs) which then describe how the density of points change over different spatial scales (Illian et al, 2008). SPPA has not been widely applied to sessile animal communities, but has been used to investigate coral colony aggregations (Muko et al, 2014), to consider mortality due to adult proximity (Gibbs and Hay, 2015), and has been suggested for quantifying changes over time (Piazza et al, 2020). Most SPPA studies of benthic communities have focused on disease spread through sponge and coral populations (e.g., Jolles et al, 2002;Zvuloni et al, 2009;Muller and van Woesik, 2012;Easson et al, 2013;Deignan and Pawlik, 2015) with limited numbers of analyses using SPPA to investigate population spatial aggregations (Prado et al, 2019).…”