Gene expression profiling reveals deep‐sea coral response to the Deepwater Horizon oil spill

Abstract

Deep-sea coral communities are key components of the Gulf of Mexico ecosystem and were adversely affected by the Deepwater Horizon (DWH) oil spill. Coral colonies exposed to oil and dispersant exhibited mortality, damage and physiological signatures of stress. Understanding how corals respond to oil and dispersant exposure at the molecular level is important to elucidate the sublethal effects of the DWH disaster and reveal broader patterns of coral stress responses. Gene expression profiles from RNAseq data were compared between corals at an impacted site and from a reference site. A total of 1,439 differentially expressed genes (≥twofold) were shared among impacted Paramuricea biscaya colonies. Genes involved in oxidative stress, immunity, wound repair, tissue regeneration and metabolism of xenobiotics were significantly differentially expressed in impacted corals. Enrichment among the overexpressed genes indicates the corals were enduring high metabolic demands associated with cellular stress responses and repair mechanisms. Underexpression of genes vital to toxin processing also suggests a diminished capacity to cope with environmental stressors. Our results provide evidence that deep-sea corals exhibited genome-wide cellular stress responses to oil and dispersant exposure and demonstrate the utility of next-generation sequencing for monitoring anthropogenic impacts in deep waters. These analyses will facilitate the development of diagnostic markers for oil and dispersant exposure in deep-sea invertebrates and inform future oil spill response efforts.

A Synthesis of Deep Benthic Faunal Impacts and Resilience Following the Deepwater Horizon Oil Spill

“…This survey was focused on healthy coral colonies throughout the northern Gulf, but also found a previously unknown coral community near Mississippi Canyon (MC294), which was visibly impacted by flocculent material containing both oil and dispersant (White et al, 2012(White et al, , 2014DeLeo et al, 2015). Visible impacts (e.g., mucous strands, loose tissue, and bare skeleton) from oiled flocculent material were assessed by examination of digital imagery for Paramuricea biscaya, Paragorgia regalis, and Swiftia pallida (White et al, 2012;DeLeo et al, 2018;Montagna and Girard, 2020). ROV surveys performed in 2011 as part of the NRDA (Fisher et al, 2014a,b) identified two additional coral sites (MC297, MC344) near (6-20 km) the DWH wellhead from 1,560 to 1,850 m water depth as also being visibly impacted by oiled flocculent material.…”

“…During the DWH (Figures 2B,F) MOSSFA and hydrocarbon intrusions ultimately caused an increase in particulate organic carbon flux ("marine snow"), advected detritus and dead falls as inputs to the benthic system (Paris et al, 2012;Valentine and Benfield, 2013;Romero et al, 2015;Lindo-Atichati et al, 2016). Certain microbial and chemotrophic communities' mineralization rates increased, lethal effects to meiofauna (specifically foraminifera) and sub-lethal effects to macrofauna, corals and megafauna were observed (White et al, 2012(White et al, , 2014Montagna et al, 2013;Valentine and Benfield, 2013;Mason et al, 2014;Schwing et al, 2015;DeLeo et al, 2018). Following DWH (1-2 years: Figures 2C,G), hydrocarbon toxicity remained elevated, surface sedimentary oxygen concentrations decreased, burial of petroleum carbon was initiated and unconsolidated flocculent material containing oil residue was re-suspended, causing changes in microbial, meiofaunal and macrofaunal community structure, and sub-lethal effects in corals and megafauna (Hsing et al, 2013;Montagna et al, 2013;Valentine and Benfield, 2013;Mason et al, 2014;Romero et al, 2015;Silva et al, 2015;Hastings et al, 2016;Yang et al, 2016;Schwing et al, 2017bSchwing et al, , 2018a.…”

Gene correlation networks reveal the transcriptomic response to elevated nitrogen in a photosynthetic sponge

“…Similar to the Turquoise and Black modules, genes within the Brown module were also downregulated in the highest nitrogen treatment and were enriched in functions relating to "DNA metabolic processes" and "DNA recombination" (Figure 5d). These been identified in deep-sea corals exposed to oil and dispersants (DeLeo et al, 2018).…”

“…The dendrogram shows the sharing of genes between categories and the fractions correspond to the number of genes significant within that category of genes. Individual genes from each GO term/module are detailed in Appendix S1 [Colour figure can be viewed at wileyonlinelibrary.com] in innate immunity have also been identified in corals(DeSalvo, Sunagawa, Voolstra, & Medina, 2010) and sponges(Guzman & Conaco, 2016) in response to increased temperature, as well as in oil-contaminated corals(DeLeo et al, 2018). Most notable, however, is a similar change in gene expression of immunity-related factors in Galaxea fascicularis from eutrophic environments(Lin et al, 2016).…”

The expanded footprint of the Deepwater Horizon oil spill in the Gulf of Mexico deep-sea benthos

“…Each one of these habitats suffered from a loss of biodiversity caused by the smothering effects of oil as well as lethal and sublethal effects from a multitude of chemical compounds contained in crude oil [13]. In addition, the use of industrial oil dispersants, such as Corexit A9500 1 , increased the bioavailability of the oil [14] and introduced synergistic toxic effects to some of the organisms [15,16,17].…”