Author Interview: Investigating microbial size classes associated with the transmission of stony coral tissue loss disease (SCTLD)

PeerJ spoke to James Evans, Ph.D. Research Marine Biologist at St. Petersburg Coastal and Marine Science Center about the recently published PeerJ Life & Environment article Investigating microbial size classes associated with the transmission of stony coral tissue loss disease (SCTLD). The article was published as part of the IABO Hub. The IABO Hub is the publishing home of the International Association for Biological Oceanography, and features the latest biological oceanography research published by the members of IABO.

Can you tell us a bit about yourself?

I’m a research marine biologist at the St. Petersburg Coastal and Marine Science Center, where I’m part of the Coral Microbial Ecology Lab. We study corals from a variety of different environments with the goal of understanding how microbes influence, and are influenced by, their coral hosts and the surrounding environment. We’re particularly interested in the role microorganisms play in coral reef diseases.

Can you briefly explain the research you published in PeerJ?

Stony coral tissue loss disease (SCTLD) is an extremely destructive disease currently impacting reefs throughout Florida and the Caribbean, and we don’t know what causes it. Pathogen identification is one of the most important components of responding to a disease, because different types of pathogens may require different types of treatments (e.g., bacteria compared to viruses). Traditionally microbial investigations of coral disease have examined coral tissue / mucus, but this approach can be complicated because even healthy corals host a large diversity of microorganisms, which makes it difficult to distinguish pathogens from other microbes present in or on the coral.

Because scientists have established that SCTLD can be transmitted through the water, we know that infected corals must shed the causative agent(s) into the water around them. Our approach was to place infected and healthy corals into mesocosms containing filtered and UV-treated seawater (i.e., seawater with a reduced microbial load), incubate them for a few days to allow corals to shed microbes into the water, then characterize the microbial communities associated with this water as a means to cut back on some of the microbial “background noise.” We then filtered this water through a sequential series of different pore-size filters, to sort the water microbes into different size classes. Finally, we applied these different filters to healthy corals to determine what size class of microorganism would transmit the disease.

What did you discover and where?

Although the transmission component of our experiment was inconclusive, we did determine that the causative agent of SCTLD is likely between 200 µm and 0.22 µm in size. We also characterized the prokaryotic communities associated with all of the 0.22 µm filters generated in this study and found overlaps with numerous other studies investigating SCTLD.

What was significant about your findings?

Our findings suggest that that microbes between 0.22 µm and 200 µm in size (e.g., bacteria, large viruses, microeukaryotes, or infected zooxanthellae) are more likely to be involved in transmission of SCTLD than larger (>200 µm) eukaryotes, small (<0.22 µm) viruses, or chemicals / toxins. Further, in characterizing the prokaryotic community associated with our mesocosms, the overlaps that we identified with other studies spanned different geographic regions, collection years, source material, and coral species, which suggests that bacteria may have some role to play in the disease.

How did you first hear about PeerJ, and what persuaded you to submit to us?

We have seen several excellent studies related to SCTLD published in PeerJ and thought it would be a great fit for this study!

How was your experience publishing an article in the IABO hub?

The IABO Hub was easy to use, and everything from initial submission to final acceptance went smoothly!

Anything else you would like to add?

Thanks for the opportunity to publish with PeerJ!