A health survey of the reef forming scleractinian cold-water corals Lophelia pertusa and Madrepora oculata in a remote submarine canyon on the European continental margin, NE Atlantic

• Published in: Journal of invertebrate pathology 2022-07, Vol.192, p.107782-107782, Article 107782
• Main Authors: Appah, J.K.M., Lynch, S.A., Lim, A., O' Riordan, R., O'Reilly, L., de Oliveira, L., Wheeler, A.J.
• Format: Article
• Language: English
• Subjects: Cold-water corals; Haplosporidia; Histology; Pathogen; Rickettsiales-like organisms; Vibrio
• ISSN: 0022-2011; 1096-0805
• DOI: 10.1016/j.jip.2022.107782

[Display omitted] •The corals experience low pathogen diversity under prevailing environmental conditions.•Sample size increases the probability of detecting a pathogen group in coral health screening.•A likely mode of pathogen entry can be associated with particulate availability and the varying feeding strategies of the scleractinian corals.•The lack of pathogens in Madrepora oculata can be attributed to the narrower diet exhibited in M. oculata compared to Lophelia pertusa, which may be limiting pathogen entry via ingestion. Monitoring of cold-water corals (CWCs) for pathogens and diseases is limited due to the environment, protected nature of the corals and their habitat and as well as the challenging and sampling effort required. It is recognised that environmental factors such as temperature and pH can expedite the ability of pathogens to cause diseases in cold-water corals therefore the characterisation of pathogen diversity, prevalence and associated pathologies is essential. The present study combined histology and polymerase chain reaction (PCR) diagnostic techniques to screen for two significant pathogen groups (bacteria of the genus Vibrio and the protozoan Haplosporidia) in the dominant NE Atlantic deep-water framework corals Lophelia pertusa (13 colonies) and Madrepora oculata (2 colonies) at three sampling locations (canyon head, south branch and the flank) in the Porcupine Bank Canyon (PBC), NE Atlantic. One M. oculata colony and four L. pertusa colonies were collected from both the canyon flank and the south branch whilst five L. pertusa colonies were collected from the canyon head. No pathogens were detected in the M. oculata samples. Neither histology nor PCR detected Vibrio spp. in L. pertusa, although Illumina technology used in this study to profile the CWCs microbiome, detected V. shilonii (0.03%) in a single L. pertusa individual, from the canyon head, that had also been screened in this study. A macroborer was observed at a prevalence of 0.07% at the canyon head only. Rickettsiales-like organisms (RLOs) were visualised with an overall prevalence of 40% and with a low intensity of 1 to 4 (RLO) colonies per individual polyp by histology. L. pertusa from the PBC canyon head had an RLO prevalence of 13.3% with the highest detection of 26.7% recorded in the south branch corals. Similarly, unidentified cells observed in L. pertusa from the south branch (20%) were more common than those observed in L. pertusa from the canyon head (6.7%).