Transcriptomic Responses of Deep-Sea Corals Experimentally Exposed to Crude Oil and Dispersant

Abstract

Resource extraction from the ocean comes with ecosystem-wide risks, including threats to its biota such as the habitat forming corals that support elevated biomass and biodiversity. Despite catastrophic incidents like the Deepwater Horizon oil spill (DWHOS) disaster that occurred in 2010, offshore oil and gas drilling continues to occur around the world. Previous work investigating the toxicity of oil and the chemical dispersant used in an attempt to mitigate the effects of the DWHOS revealed that the dispersant elicits a stronger, negative physiological response than oil alone. However, little is known regarding the specific ways in which these anthropogenic pollutants impact organisms at the cellular level. To investigate the impacts of each pollutant and their synergistic effects on corals, we analyzed the transcriptional responses of the deep-sea octocorals Callogorgia delta and Paramuricea type B3 following 12 h of exposure to oil, dispersant, and mixtures of oil and dispersant. Analyses revealed that the highest levels of significant differential gene expression were found among the treatments containing dispersant, which corresponds to the significant effects observed in physiological experiments. Functional analyses of annotated transcripts further suggest both species- and colony-specific responses to the exposures, likely due to underlying cellular and physiological differences. However, some commonalities were observed among the responses to chemical stress across treatments and species, including immune and cellular stress responses, altered energy metabolism, and oxidative stress, elucidating how corals respond to chemical pollutants. As resource extraction is an ongoing threat, this study demonstrates the importance of considering the varied and diverse responses of biota to anthropogenic disturbances and the implications of introducing chemicals into vulnerable ecosystems like those associated with deep-sea corals.

Capacity of deep‐sea corals to obtain nutrition from cold seeps aligned with microbiome reorganization

“…To assess expression levels, the filtered and trimmed sequences were mapped and quantified against a de novo transcriptome for C. delta from the Gulf of Mexico (DeLeo et al, 2021 ) using Salmon (Patro et al, 2017 ) in quasi‐mapping mode. Significantly differentially expressed genes (DEGs; adjusted p ‐value <.5, absolute log2‐fold change [FC] >1) in relation to site (MC751 vs. MC885) and proximity to cold seeps (seep vs. non‐seep) were carried out using the “ DESEq2 ” package in R (Love et al, 2014 ).…”

“…For example, hydrocarbon pollution has long‐term impacts on coral health and the associated fauna (Girard et al, 2018 ; Guzman et al, 2020 ; McClain et al, 2019 ). Exposure to hydrocarbons and related toxic chemicals may cause colony mortality or have sublethal consequences such as; (i) a decline in health and growth of coral colonies (Girard & Fisher, 2018 ; Girard et al, 2019 ), (ii) a change of the associated epifauna (Demopoulos et al, 2016 ; Lewis et al, 2020 ), (iii) a shift in the associated microbial community (Luter et al, 2019 ; Turner & Renegar, 2017 ), and (iv) an influence on gene expression of the coral host (DeLeo et al, 2018 , 2021 ). Yet, some cold‐water corals grow near active cold seeps (Quattrini et al, 2013 ) that are a source of various chemicals including hydrogen sulfide, methane, and other hydrocarbon‐rich fluids in the environment.…”

A broad‐taxa approach as an important concept in ecotoxicological studies and pollution monitoring

“…Transcriptomic analyses performed on aquatic invertebrates exposed to various pollutants (Srivastava et al ., 2010; Elran et al ., 2014; Riesgo et al ., 2014; Ereskovsky et al ., 2017; Kenny et al ., 2018, 2020; Zhang et al ., 2019 b ; Luter et al ., 2020; DeLeo et al ., 2021; Rubin et al ., 2021) have shed light on species‐specific differences in response to environmental pollution. Tests based on the mode of regulation and expression of genes of the aryl hydrocarbon receptor signalling pathway (Hahn, Karchner & Merson, 2017) and xenobiotic‐metabolising enzymes have become prominent examples of these approaches, serving as reliable pollution biomarkers in various organisms, including non‐model organisms (Zhou et al ., 2020).…”

Oil Spill Incidents on Coral Reefs: Impacts and Remediation Technologies

“…Tissue death [19][20][21][22][23] Impaired feeding [20,22,24] Impaired polyp retraction [21,22,25,26] Impaired debug or recovery ability [27,28] Increased mucus production [22,[29][30][31][32] Change in calcification rate [21,[33][34][35] Damage to the gonads [29,36] Premature expulsion of larva [37,38] Larval death [36,39,40] Impaired larval settlement [36,[41][42][43][44][45] Expulsion of zooxanthellae [21,29] Change in primary production of zooxanthellae [21,23,26,46] Increased expression of genes associated with oxidative, immune, and metabolic stress responses [28,47] Muscle atrophy [29] Tissue and fragment loss [48] Bioaccumulation [10,…”