Biology subjects

Strand, E. L.

Publications and source records attributed to Strand, E. L..

3 recordsLinked to original sources

bioRxiv2025

Seasonal plasticity of symbiotic strategies clarifies coral holobiont resistance and resilience

As coral reefs face unprecedented declines driven by thermal stress and the breakdown of coral symbiosis (i.e., coral bleaching), restoration efforts increasingly rely on coral health and resilience rankings. However, seasonal plasticity in symbiosis and holobiont metabolism, along with the presence of cryptic species, can complicate data interpretation. Therefore, quantifying seasonal plasticity in coral physiology and incorporating genetic identification are essential for accurately interpreting and drawing conclusions from trait-based and fitness-based analyses. To test the effect of seasonal and site variation on physiological plasticity we sampled three ecologically dominant genera, Acropora, Pocillopora, and Porites across three lagoon sites (n=15 tagged colonies genus-1 site-1) on the north shore of Moorea French Polynesia in January, March, September, and December of 2020. We identified coral host and intracellular symbiotic Symbiodiniaceae to the highest taxonomic resolution possible and quantified 13 physiological variables within the holobiont. Genetic analyses identified A. pulchra along with cryptic lineages in Pocillopora (P. meandrina, P. tuahiniensis) and Porites (P. evermanni, P. lobata/lutea). A. pulchra was dominated by Durusdinium trenchii and also contained Symbiodinium microadriaticum. Symbiont communities differed between cryptic congeners, with P. meandrina hosting Cladocopium latusorum and P. tuahiniensis hosting Cladocopium pacificum, whereas P. evermanni and P. lobata/lutea both hosted Cladocopium (C15), but each with unique C15 profiles. Weedy taxa such as Acropora and Pocillopora displayed a cycle of symbiont boom and bust in response to seasonally variable light and temperature, likely contributing to the high stress sensitivity of these taxa. In contrast, despite seasonal environmental variability, Porites displayed greater symbiont stability, with temperature--rather than light--serving as the stronger explanatory variable of seasonal variation in host physiology. Increased host biomass under cooler conditions, which provides energy reserves, may serve as an important stabilizing factor in massive Porites well-documented stress resilience. Collectively, our data provide essential evidence of the need for integrative analyses considering baseline physiological states across seasons along with host and symbiont genetics, particularly in light of the plethora of climate change related stress test assays taking place throughout the year across coral taxa with cryptic lineages.

physiology↗

bioRxiv2021

Ploidy variation and its implications for reproduction and population dynamics in two sympatric Hawaiian coral species

Standing genetic variation is a major driver of fitness and resilience, and therefore of fundamental importance for threatened species such as stony corals. We analyzed RNA- seq data generated from 132 Montipora capitata and 119 Pocillopora acuta coral colonies collected from K[a]neohe Bay, Oahu, Hawaii. Our goals were to determine the extent of colony genetic variation and to study reproductive strategies in these two sympatric species. Surprisingly, we found that 63% of the P. acuta colonies were triploid, with putative independent origins of the different triploid clades. These corals have spread primarily via asexual reproduction and are descended from a small number of genotypes, whose diploid ancestor invaded the bay. In contrast, all M. capitata colonies are diploid, outbreeding, with almost all colonies genetically distinct. Only two cases of asexual reproduction, likely via fragmentation, were identified in this species. We report two distinct strategies in sympatric coral species that inhabit the largest sheltered body of water in the main Hawaiian Islands. These data highlight divergence in reproductive behavior and genome biology, both of which contribute to coral resilience and persistence. Significance StatementGiven the threat posed to coral reef ecosystems by human caused climate change, there is a growing focus on developing strategies for the protection and restoration of these critical marine habitats. These efforts are however limited by our understanding of the diversity of coral survival and reproductive strategies. Our analysis of data from two coral species inhabiting the same Hawaiian bay found that one is a strict sexual outbreeder, whereas the other reproduces predominantly asexually (i.e., clonally) and includes both diploids and triploids. These results broaden our understanding of coral biology, adaptability, and evolution, and underpin future research into the mechanisms of coral resilience that can inform restoration activities.

genomics↗

bioRxiv2021

Energetics but not development is impacted in coral embryos exposed to ocean acidification

In light of the chronic stress and mass mortality reef-building corals face under climate change, it is critical to understand the processes essential to reef persistence and replenishment, including coral reproduction and development. Here we quantify gene expression and size sensitivity to ocean acidification across a set of developmental stages in the rice coral, Montipora capitata. Embryos and swimming larvae were exposed to pH treatments 7.8 (Ambient), 7.6 (Low) and 7.3 (Xlow) from fertilization to 9 days post-fertilization. Embryo and larval volume, and stage-specific gene expression were compared between treatments to determine the effects of acidified seawater on early development. While there was no measurable size differentiation between fertilized eggs and prawn chips exposed to pH 7.8, 7.6, and 7.3, early gastrula and planula raised in reduced pH treatments were significantly smaller than those raised in ambient seawater, suggesting an energetic cost to developing under low pH. However, no differentially expressed genes emerged until 9 days post-fertilization. Notably, gene expression patterns of larvae developing at pH 7.8 and pH 7.3 were more similar than those developing at pH 7.6. Larvae from pH 7.6 showed upregulation of genes involved in cell division, regulation of transcription, lipid metabolism, and oxidative stress in comparison to the other two treatments. While low pH appears to increase energetic demands and trigger oxidative stress, the developmental process is robust to this at a molecular level, with swimming larval stage reached in all pH treatments. Summary statementThis developmental time series tracks the physiological and transcriptomic outcomes of early coral development under ambient pH (pH 7.8), and two low pH conditions (pH 7.6 and 7.3).

physiology↗