Research

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scRNAseq approaches to define cell types in marine invertebrates

Single cell RNA sequencing (scRNAseq) has recently allowed us to characterize cell types based on transcriptional profiles in many non-model organisms. However, the lack of well annotated reference genomes and our poor understanding of cell types outside of model systems limits our interpretation of this new technology. We aim to use histology, in situ hybridization, flow cytometry, and novel bioinformatic approaches to help better characterize cell types in two marine invertebrates: scleractinian corals and ctenophores.

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Environmental memory within and across generations

Reef-building corals respond to the temporal integration of both pulse events (i.e., heat waves) and press thermal history (i.e., local environment) via physiological changes, with ecological consequences. When attempting to model the impacts of climate change on biological systems temporal variability creates complexity, as organisms are integrating previous environmental signals with consequences for their response to subsequent disturbances. The integration of multiple historical events rapidly complicates potential biological outcomes, as events can be of varying types (i.e. pulse, press, ramp, constant) and additive, reductive, synergistic, or antagonistic, and even across generations. A growing body of literature outlines the potential for cross-generational acclimatization occurring in marine invertebrates in response to adverse environmental conditions, leading to “pre-conditioned” offspring phenotypes. However, little research has focused on the timeframe and types of disturbances that elicit these responses. Here we demonstrate the importance of integrating across both chronic and acute, or press and pulse, thermal disturbances in order to understand how environmental history impacts adult and offspring phenotypes. This project has two parallel aims:

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Multi-omic analysis of coral bleaching phenotypes

Coral bleaching is an energetically costly consequence of stress that commonly leads to mortality. However, survival after bleaching is possible if stress returns below physiological thresholds or if alternative energy acquisition is used, including catabolism of stored reserves and heterotrophic feeding. These two outcomes, (1) bleaching then mortality or (2) maintaining an alternative symbiotic “bleached” state, involve different cellular mechanisms that have not been directly compared. In this project, we used a multi-omic approach to understand the mechanisms that underlie differential bleaching phenotypes (“mortality” vs “bleached”) to chronic thermal stress in the common reef-building coral, Porites astreoides. The aims of this project are: 

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Porites astreoides genome assembly and annotation 

With the increased accessibility of genomic sequencing, the molecular resources of non-model organisms, such as corals, are becoming readily available. Having reference transcriptomes and genomes for coral species has created a platform to understand the evolutionary history of corals and potential mechanisms for adaptation to future climate change. However, only about 20 coral species have references genomes or transcriptomes, limiting the interpretation of molecular mechanisms in other corals species. Here, we sequenced and annotated the Porites astreoides genome. P. astreoides is a notoriously resilient coral that is highly abundant across most shallow reef environments in the Caribbean. Creating a reference genome for this resilient coral will assist in outlining the molecular basis of future responses to climate change and allow other molecular approaches to take place (e.g. whole-genome bisulfite sequencing).

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Coral reproduction across depth gradients

Early life history traits of brooding corals are often affected by the environmental conditions experienced by parental colonies. Such parental effects can impact offspring survival, which influences the overall success of a population as well as resilience to environmental challenges. This study examines the reproductive ecology and early life history traits of the brooding coral Porites astreoides across a depth gradient in Bermuda. Fecundity, larval size, larval Symbiodinium density, and settlement success, as well as post-metamorphic juvenile survival, growth, and Symbiodinium density were compared across three reef sites representing an inshore patch reef (2–5 m), an offshore rim reef (8–10 m), and an upper-mesophotic reef (30–33 m). Although fecundity did not differ across sites, larvae produced by colonies on the patch reef site were smaller, had lower Symbiodinium densities, and had lower rates of settlement and juvenile survival compared to larvae from colonies on the rim and upper-mesophotic reef sites. Larvae produced by colonies from the rim and upper-mesophotic sites did not differ in size or Symbiodinium densities; however, rates of settlement, growth, and survival were higher for larvae from the upper-mesophotic site compared to those from the rim reef site. These results indicate that offspring quality and success vary among sites with differing environmental conditions and may imply higher recruitment potential and resilience for upper-mesophotic corals.