Cynthia Silveira: "From phage-to-shark: relationships between coral reef health and predation pressure at the micro and macro scales "

Fri February 24th 2023, 12:00pm
Event Sponsor
Hopkins Marine Station
Hopkins Marine Station

Predation pressure has well-documented cascading effects on coral reef health and stability. However, the extent of these cascading effects can vary considerably across time and space. This variability is likely a result of the complex interactions between the reefs’ biotic and abiotic dimensions. One significant biological component still poorly integrated into the reefs' energy landscape is the microbial community, despite its relevance in mediating coral death and susceptibility to bleaching. In this talk, I will introduce the idea that the predation pressure exerted by viruses that infect bacteria in the microbial food web may be analogous to the top-down pressure of macroorganisms. I will present data showing the relationships between live coral cover and viruses, bacteria, benthic algae, fish biomass, and water chemistry in 110 Pacific reefs spanning inhabited and uninhabited islands and atolls. Statistical learning analysis of the phage-to-shark dataset showed that the abundance of turf algae, viruses, and bacteria, in that order, were the variables best predicting the variance in coral cover on these reefs. While fish biomass was not a strong predictor of coral cover, the relationship between fish predation and coral cover became apparent when analyzed in the context of viral predation: high coral cover (>50%) occurred on reefs with a combination of high predator fish biomass (sum of sharks and piscivores >200 g.m-2) and high virus-to-bacteria ratios (>10), an indicator of viral predation pressure. These results support the hypothesis that viral predation of bacteria is associated with high coral cover and, thus, maintenance of coral health and stability. I propose that the combined predation pressures from fishes and viruses control energy fluxes that inhibit the detrimental accumulation of ecosystem energy in the microbial component of the coral reef food web. 

Dr. Cynthia Silveira is an Assistant Professor at University of Miami.