A Review of Marine Viruses in Coral Ecosystem

Abstract

Coral reefs are among the most biodiverse biological systems on earth. Corals are classified as marine invertebrates and filter the surrounding food and other particles in seawater, including pathogens such as viruses. Viruses act as both pathogen and symbiont for metazoans. Marine viruses that are abundant in the ocean are mostly single-, double stranded DNA and single-, double stranded RNA viruses. These discoveries were made via advanced identification methods which have detected their presence in coral reef ecosystems including PCR analyses, metagenomic analyses, transcriptomic analyses and electron microscopy. This review discusses the discovery of viruses in the marine environment and their hosts, viral diversity in corals, presence of virus in corallivorous fish communities in reef ecosystems, detection methods, and occurrence of marine viral communities in marine sponges.

Screening for climate adaptative loci using seascape genomics resolves phenotypic variation in heat tolerance of the coral Acropora millepora.

“…As it was neither observed for other colonies nor for colony 10 in the control treatment, it is unlikely to be the consequence of pathogen introduction through handling of the colony. However, high temperatures are known to promote microbial infections in many benthic organisms, including corals, through increases of virulence genes expression and number of pathogens life cycles per unit of time, host cells lysis, disruption of immune system functions or changes in bacterial communities [112][113][114] . Colony 10 might harbor a thermosensitive immune system, which could be a possible explanation for its health impairment in this experiment.…”

Metagenomic Assessment of DNA Viral Diversity in Freshwater Sponges, Baikalospongia bacillifera

“…We also identified the viral families that are known to infect microalgae (Phycodnaviridae), archaea (Bicaudaviridae), protozoa (Mimiviridae and Lavidaviridae), and invertebrates (Baculoviridae and Poxviridae). These families, except for the Lavidaviridae, were found earlier in the viromes of marine sponges [14,16]. A large abundance of virophage sequences was discovered previously in the viromes of Baikal water [45].…”

“…Viruses are the least studied component of the sponge community, which is explained by the methodological difficulties in the investigation of the existing variety of viruses. However, new technologies and approaches such as next-generation sequencing and metagenomic analysis have become good alternatives to classical virological methods and useful aids in the study of uncultivated viruses [13], including the viral communities of sponge holobionts [14][15][16].…”

“…Some studies were focused on the study of RNA viruses in sponges [26,27]. In general, various virome sequences related to viruses from more than 20 families, as well as many unclassified and unidentified viruses, were revealed in different marine and freshwater sponges [14][15][16]25]. The bulk of the sponge-associated viruses are DNA viruses-both single-stranded (ssDNA) and double-stranded (dsDNA) ones [21].…”

The coral microbiome: towards an understanding of the molecular mechanisms of coral–microbiota interactions

“…Metagenomic sequencing show a high diversity of coral-associated DNA and RNA viruses (Weynberg et al 2014 ). Large metagenomic and metatranscriptomic sequencing efforts towards establishing a ‘coral virome’ conducted across 101 cnidarian samples from the Red Sea documented DNA and RNA viral assemblages associated with corals (Cardenas et al 2020 ) [for a recent review on the roles of viruses in corals see Ambalavanan et al ( 2021 )]. While the functional roles of coral-associated viruses are still unclear, they likely play important roles in the coral holobiont.…”