Large birth size does not reduce negative latent effects of harsh environments across life stages in two coral species

Abstract

Abstract. When juveniles must tolerate harsh environments early in life, the disproportionate success of certain phenotypes across multiple early life stages will dramatically influence adult community composition and dynamics. In many species, large offspring have a higher tolerance for stressful environments than do smaller conspecifics (parental effects). However, we have a poor understanding of whether the benefits of increased parental investment carry over after juveniles escape harsh environments or progress to later life stages (latent effects). To investigate whether parental effects and latent effects interactively influence offspring success, we determined the degree to which latent effects of harsh abiotic conditions are mediated by offspring size in two stony coral species. Larvae of both species were sorted by size class and exposed to relatively high-temperature or low-salinity conditions. Survivorship was quantified for six days in these stressful environments, after which surviving larvae were placed in ambient conditions and evaluated for their ability to settle and metamorphose. We subsequently assessed long-term post-settlement survival of one species in its natural environment. Following existing theory, we expected that, within and between species, larger offspring would have a higher tolerance for harsh environmental conditions than smaller offspring. We found that large size did enhance offspring performance in each species. However, large offspring size within a species did not reduce the proportional, negative latent effects of harsh larval environments. Furthermore, the coral species that produces larger offspring was more, not less, prone to negative latent effects. We conclude that, within species, large offspring size does not increase resistance to latent effects. Comparing between species, we conclude that larger offspring size does not inherently confer greater robustness, and we instead propose that other life history characteristics such as larval duration better predict the tolerance of offspring to harsh and variable abiotic conditions. Additionally, when considering how stressful environments influence offspring performance, studies that only evaluate direct effects may miss crucial downstream (latent) effects on juveniles that have significant consequences for long-term population dynamics.

Crude oil contamination interrupts settlement of coral larvae after direct exposure ends

“…These 'crashes' have previously been observed in this species using a similar experimental method (Hartmann et al 2013). The likelihood that a replicate crashed in our experiment was independent of site or the presence of oil contamination (p > 0.05 for both, Fisher's exact test), suggesting total mortality of larvae was not a response to our treatments.…”

“…during dispersal; Vermeij et al 2006, Hartmann et al 2013, Ross et al 2013. While the effect of oil contamination on survival reduced coral populations by 25% in Orbicella faveolata and undetectably in Agaricia humilis, inclusion of the effect of oil on total settlement reduced coral densities by 85% and 40%, respectively.…”

“…For all indicators, these delayed effects outweighed direct effects, showing that even after larvae escape contaminated seawater the impact of chemical stressors remains. While the larval period constitutes a short period in the life of organisms such as corals, the environment experienced during these early stages has a disproportionately large effect on the long-term success of these individuals (Vermeij et al 2006, Hartmann et al 2013, Ross et al 2013.…”

“…To induce larval settlement, an extract of crustose coralline algae (to O. faveolata replicates) or a cured limestone tile with growing crustose coralline algae (to A. humilis replicates) was added to each replicate. We have previously demonstrated the suitability of these techniques for testing settlement competence in these species (Hartmann et al 2013). Moving larvae from oil-contaminated to non-oil-contaminated seawater and exposing them to positive settlement cues was done to mimic the migration of larvae from the sea surface to the benthos in search of settlement substrate.…”

Preconditioning in the reef-building coralPocillopora damicornisand the potential for trans-generational acclimatization in coral larvae under future climate change conditions

“…This is true in the case of the Olympia oyster, where exposure to ocean acidification during development resulted in smaller shell sizes, and the latent effect of small size persisted for more than a month in ambient common garden conditions (Hettinger et al, 2012). It appears for corals, however, that small size is not always a certain predictor of negative performance, as large and small larvae exposed to temperature and salinity stress had the same propensity for latent effects in the coral Orbicella faveolata (Hartmann et al, 2013). These variable post-metamorphosis responses in marine taxa highlight the need to track the duration and magnitude of trans-generational acclimatization beyond the larval stage, through recruitment and into the next generation.…”