Microbial exchanges through cleaner fish in reef environments bring new levels of understanding to reef ecology
By MADELINE HASS — science@theaggie.org
Species-driven microbial transfers within ecosystems have become a growing area of interest within microbial ecology. One way to study these interactions is through research conducted on species aggregation hubs, which are areas where a concentration of species will gather for a particular purpose, such as feeding or spawning.
A team of researchers consisting of scientists from UC Davis and Woods Hole Oceanographic Institute (WHOI) in collaboration with the University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science set out to study these microbial interactions within coral reef communities.
The group’s study, published in the Marine Ecology Progress Series journal, is one of the first to take a closer look at the effects that cleaner fish stations have on microbial diversity. Cleaner fish stations are a classic example of aggregation hubs, as cleaner fish will be stationed in one consistent area and attract groups of client fish to swim up and be cleansed of any bacteria or parasites, and as a result they are microbial hotspots.
Anya Brown, an assistant professor in the Department of Evolution and Ecology at UC Davis and the Bodega Marine Laboratory, as well as a corresponding author of the study, spoke on the importance of studying these cleaner fish.
“We had expertise and interest in cleaner behavior, and we realized just how much physical contact is involved in the interaction between the cleaner and the client fish,” Brown said. “We also know from previous studies, and as showcased in this study, that if you manipulate the cleaner fish it will completely change the abundance and density and diversity of other fish. So, because you’ve got cleaner fish attracting a wide range of fish to that site, all of which are bringing their own microbes with them, you create this potential for these cleaning stations to be these hotspots for the exchange of microbes.”
The team focussed their study on specifically cleaner gobies within two separate reef systems, one in Puerto Rico and the other in St. Croix, as they set out to investigate the microbial diversity around the cleaning hubs.
“One of the reasons why we chose cleaning gobies is because they’re conspicuous, they’re easy to find and easy to see,” Brown said. “You can find lots of these cleaning gobies in all of the places we were going to in the Caribbean, and the interaction between cleaners and clients are quite obvious while also happening very frequently. The range of cleaning gobies is also pretty small — they don’t travel much further than a meter from their home base or their major habitat.”
The team tested the effects of cleaner fish by experimentally removing cleaner gobies to create numerous different treatment zones with and without the presence of cleaner gobies. They then monitored the microbial communities of the nearby reef areas, while also paying special attention to the amount of client fish present in each treatment zone and the effects on damselfish.
Overall, the researchers found the presence of cleaner gobies attracted significantly more visitors, while also quantifiably influencing the diversity of microbes living in the reef. Damselfish showcased effects on their microbiome by the presence of cleaner gobies as well. The study further went on to note that the microbial impact shifts depending on the type of seafloor or reef territory, as each reef territory has a distinctive microbial environment.
Paul Sikkel, a research professor in the Department of Marine Biology and Ecology at the University of Miami Rosenstiel School, remarked more on the group’s findings.
“Cleaner fish seem to be able to facilitate the recovery of the microbiome of the client fish, if it’s been stripped, like with antibiotics, they can help recover that,” Sikkel said. “Say we have a mass heating event that could affect the microbiome of the client fish. Well, the cleaners may help them to regain their natural microbiome, which is essential for protecting against diseases.”
This discovery is a large step forward in understanding microbial interactions and poses as a stepping stone in implementing new reef management strategies through a reef restoration lens. Sikkel described the potential implications of the study.
“If you have a heavily fished out reef, the cleaning stations can act like sort of the hubs of recovery,” Sikkel said. “They can attract what fish are left, and maybe even fish from other areas, which could then help restore that section of the reef. There are lots of implications and possibilities that we’re only beginning to sort of see and know what the potential is.”
Brown further commented on the importance of microbes.
“One thing here that we’re excited about is providing some foundational knowledge of how microbes are moving around the reef,” Brown said. “In a more foundational science sense, this is giving us an idea of where we might have hotspots of transmission of microbes, and we’re suggesting that cleaning stations may be one of them.”
This study makes the vital role of cleaner fish in facilitating microbial exchanges abundantly clear. Further research of the influence of species-driven microbial transfers within these coral reef systems could offer even more insight into coral reef resilience and new reef management strategies. This study can serve as a reminder that sometimes an ecosystem’s survival relies on the smallest interactions.
Written by: Madeline Hass – science@theaggie.org
