The effect of simulated manatee disturbance intensity and stingray foraging on Thalassia testudinum recovery and benthic invertebrate communities

Decreased resistance and/or resilience following a disturbance event may alter ecological succession and prevent recovery to a previous state. We hypothesized that removal of biomass from seagrass beds through simulated manatee grazing may render remaining live plant biomass more vulnerable to uprooting by bioturbating organisms, which may delay or prevent ecological recovery. Moreover, we broadened our perspective on community recovery by testing whether bioturbation alters invertebrate communities associated with previously grazed plots. To test this hypothesis, we created experimental plots in Thalassia testudinum seagrass beds in Bocas del Toro, Panama that were subjected to varying levels of simulated sirenian grazing and then made accessible or inaccessible to bioturbating stingrays. We then assessed the impact of these treatments on seagrass cover and communities of macroinfauna and meioinfauna for approximately one year. Accessibility of plots to stingrays had no effect on seagrass recovery, despite abundant and actively foraging stingrays. T. testudinum was the only macroorganism to colonize gaps created by stimulated grazing, indicating that T. testudinum recovery did not require facilitation by other seagrasses or algae that are often considered pioneer species, which contrasts with previous studies in more oligotrophic waters. Intensity of simulated sirenian grazing had no effect on macroinfaunal or meiofaunal communities, and stingray access affected only meioinfaunal communities, which stingrays do not feed on directly. Simulated sirenian grazing may be less attractive to bioturbating stingrays than other previously studied forms of disturbance to seagrass beds. This suggests that the importance of positive interactions in communities with similar species compositions is highly context dependent. This Bioproject contains demultiplexed sequencing data from 18S rRNA gene metabarcoding of sieved marine sediment core samples collected as part of the study.