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It is important to consider flow rate explicitly in coral growth and bleaching studies across multiple species with differing life histories to guide coral conservation, management and captive culture. We quantified growth rates and coral bleaching responses to thermal stress (approx. 18 DHW) in flow-through aquaria with various current velocities to test whether flow conditions alter experimental outcomes. Across natural flow rates (< 1 to over 50 cm/sec), Montipora capitata, Pocillopora acuta, and Pocillopora meandrina showed increased growth and bleaching recovery at intermediate flow rates. Growth rates for all species increased from no flow to intermediate (50–100 turnovers-per-hour, ~ 10–30 cm/s), but then decreased at highest flow (> 190 tph, > 50 cm/s) although this trend was not significant for P. meandrina. The flow treatment with highest recovery from temperature stress differed across species, ranging from 4 tph in the flow-loving P. meandrina to 210 tph in the lagoonal M. capitata, indicating that natural flow regime alone is not predictive. Fragments from the same individual (e.g., P. acuta colony 8) held under identical thermal conditions continue bleaching and die under one flow regime (4 tph), whereas they recover from bleaching (30 tph) or grow fastest (105 tph) under different flow treatments. Flow is rarely reported in the literature, but uncontrolled flow effects may help to explain some of the variation in coral bleaching results reported across the literature. Significant differences among individual colonies, and colony-by-flow interactions, preclude generalizations beyond that flow rates can alter the outcome of both coral growth and bleaching experiments.
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Gene expression response under thermal stress in two Hawaiian corals is dominated by ploidy and genotype
Abstract Transcriptome data are frequently used to investigate coral bleaching; however, the factors controlling gene expression in natural populations of these species are poorly understood. We studied two corals,Montipora capitataandPocillopora acuta, that inhabit the sheltered Kāne'ohe Bay, Hawai'i.M. capitatacolonies in the bay are outbreeding diploids, whereasP. acutais a mixture of clonal diploids and triploids. Populations were sampled from six reefs and subjected to either control (no stress), thermal stress, pH stress, or combined pH and thermal stress treatments. RNA‐seq data were generated to test two competing hypotheses: (1) gene expression is largely independent of genotype, reflecting a shared treatment‐driven response (TDE) or, (2) genotype dominates gene expression, regardless of treatment (GDE). Our results strongly support the GDE model, even under severe stress. We suggest that post‐transcriptional processes (e.g., control of translation, protein turnover) modify the signal from the transcriptome, and may underlie the observed differences in coral bleaching sensitivity via the downstream proteome and metabolome.
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- Award ID(s):
- 2128073
- PAR ID:
- 10545928
- Publisher / Repository:
- Ecology and Evolution
- Date Published:
- Journal Name:
- Ecology and Evolution
- Volume:
- 14
- Issue:
- 7
- ISSN:
- 2045-7758
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1002/ece3.70037
