Detachment of Porites cylindrica nubbins by herbivorous fishes

Escaping the benthos with Coral Reef Arks: effects on coral translocation and fish biomass

Anthropogenic stressors like overfishing, land based runoff, and increasing temperatures cause the degradation of coral reefs, leading to the loss of corals and other calcifiers, increases in competitive fleshy algae, and increases in microbial pathogen abundance and hypoxia. To test the hypothesis that corals would be healthier by moving them off the benthos, a common garden experiment was conducted in which corals were translocated to midwater geodesic spheres (hereafter called Coral Reef Arks or Arks). Coral fragments translocated to the Arks survived significantly longer than equivalent coral fragments translocated to Control sites (i.e., benthos at the same depth). Over time, average living coral surface area and volume were higher on the Arks than the Control sites. The abundance and biomass of fish were also generally higher on the Arks compared to the Control sites, with more piscivorous fish on the Arks. The addition of Autonomous Reef Monitoring Structures (ARMS), which served as habitat for sessile and motile reef-associated organisms, also generally significantly increased fish associated with the Arks. Overall, the Arks increased translocated coral survivorship and growth, and exhibited knock-on effects such as higher fish abundance.

Low coral bleaching prevalence at the Bolinao-Anda Reef Complex, northwestern Philippines during the 2016 thermal stress event

Here, we examined the coral bleaching responses during the 2016 thermal stress event and post-bleaching changes in coral communities in the heavily disturbed reefs of the Bolinao-Anda Reef Complex (BARC), northwestern Philippines. Less than 25% of colonies bleached, with 77% attributed to five genera (Dipsastrea, Porites, Fungia, Seriatopora, and Montipora). Coral bleaching prevalence was associated with site location, coral composition, and coral abundance, suggesting that small-scale variation (<20 km) in coral communities (taxa and density) influences spatial variation in coral bleaching prevalence. There was no noticeable change in coral composition and cover two years after the bleaching event as exposure to chronic disturbance likely selected for the dominance of stress tolerant coral taxa and communities. Results show that the 2016 thermal stress event caused coral bleaching but with low prevalence at the BARC, which suggests that disturbed reefs may provide spatial refuge to coral communities from thermal stress.

Fish predation hinders the success of coral restoration efforts using fragmented massive corals

As coral reefs continue to decline globally, coral restoration practitioners have explored various approaches to return coral cover and diversity to decimated reefs. While branching coral species have long been the focus of restoration efforts, the recent development of the microfragmentation coral propagation technique has made it possible to incorporate massive coral species into restoration efforts. Microfragmentation (i.e., the process of cutting large donor colonies into small fragments that grow fast) has yielded promising early results. Still, best practices for outplanting fragmented corals of massive morphologies are continuing to be developed and modified to maximize survivorship. Here, we compared outplant success among four species of massive corals (Orbicella faveolata, Montastraea cavernosa, Pseudodiploria clivosa, and P. strigosa) in Southeast Florida, US. Within the first week following coral deployment, predation impacts by fish on the small (<5 cm²) outplanted colonies resulted in both the complete removal of colonies and significant tissue damage, as evidenced by bite marks. In our study, 8–27% of fragments from four species were removed by fish within one week, with removal rates slowing down over time. Of the corals that remained after one week, over 9% showed signs of fish predation. Our findings showed that predation by corallivorous fish taxa like butterflyfishes (Chaetodontidae), parrotfishes (Scaridae), and damselfishes (Pomacentridae) is a major threat to coral outplants, and that susceptibility varied significantly among coral species and outplanting method. Moreover, we identify factors that reduce predation impacts such as: (1) using cement instead of glue to attach corals, (2) elevating fragments off the substrate, and (3) limiting the amount of skeleton exposed at the time of outplanting. These strategies are essential to maximizing the efficiency of outplanting techniques and enhancing the impact of reef restoration.