Comparing the Efficiency of Nursery and Direct Transplanting Methods for Restoring Endangered Corals

Restoration of plants, corals, and other sessile species often involves transplanting individuals to sites chosen for rehabilitation. Transplanted individuals are sometimes harvested directly from wild populations (direct transplanting), and sometimes propagated or cultured in a “nursery” before being transplanted (nursery outplanting). The ecological effectiveness and cost-efficiency of these methods have rarely been compared, so we performed an experiment to address this. Coral fragments, Acropora cervicornis (n = 780), were collected and assigned to one of three treatments: 1) directly transplanted to a restoration site and placed loose on the reef; 2) directly transplanted and manually attached to the reef; 3) moved to a nursery site near the restoration site for three months before being transplanted and manually attached to the reef. Treatment 1 was inefficient simply because these corals survived poorly. After 15 months, the survival and growth of corals assigned to treatments 2 and 3 was similar. The nursery method (3) was more expensive and time-consuming than direct transplanting (2), so treatment 2 yielded twice as many surviving corals per hour of work invested and three times as many survivors per dollar of set-up costs as treatment 3. The net production of live coral tissue per hour or per dollar invested was also greatest for direct-attached transplants. Cost- and time-efficiency are important considerations for practitioners seeking to maximize the area of reef rehabilitated and, in this case study, were maximized by bypassing a nursery stage

Comparing monitoring data collected by volunteers and professionals shows that citizen scientists can detect long-term change on coral reefs

Citizen science is increasing and can complement the work of professional scientists, but the value of citizen data is often untested. We therefore compared the long-term changes to coral reefs that were detected by a professional and volunteer monitoring program, operated by University of Rhode Island (URI) staff and Reef Check volunteers, respectively. Both groups monitored reefs in the British Virgin Islands from 1997 to 2012 but mostly monitored different sites (URI 8 sites and Reef Check 4 sites). When URI staff visited the Reef Check sites to perform a side-by-side to comparison, Reef Check fish density estimates were consistently higher than those made by URI observers but benthic indicators showed better agreement. When long-term trends were compared, the two programs detected qualitatively similar trends in the % cover of live coral and coral rubble, but temporal changes in the cover of other benthic indicators were less consistent. The URI program detected a widespread increase in parrotfish densities and a decline in snappers, whereas the Reef Check surveys detected no consistent changes in any fish density indicators. Overall, site-specific temporal trends revealed by the URI program were more often statistically significant than those from Reef Check (twice as often for benthic taxa, and five times as often for fish taxa), which implies greater precision of the scientists’ counts. Nonetheless, volunteers were able to detect important changes in benthic communities and so have a valuable role to play in assessing change on coral reefs

Metabolomic Shifts Associated with Heat Stress in Coral Holobionts

Understanding the response of the coral holobiont to environmental change is crucial to inform conservation efforts. The most pressing problem is “coral bleaching,” usually precipitated by prolonged thermal stress. We used untargeted, polar metabolite profiling to investigate the physiological response of the coral species Montipora capitata and Pocillopora acuta to heat stress. Our goal was to identify diagnostic markers present early in the bleaching response. From the untargeted UHPLC-MS data, a variety of co-regulated dipeptides were found that have the highest differential accumulation in both species. The structures of four dipeptides were determined and showed differential accumulation in symbiotic and aposymbiotic (alga-free) populations of the sea anemone Aiptasia (Exaiptasia pallida), suggesting the deep evolutionary origins of these dipeptides and their involvement in symbiosis. These and other metabolites may be used as diagnostic markers for thermal stress in wild coral

Multi-omic characterization of the thermal stress phenome in the stony coral Montipora capitata

Background Corals, which form the foundation of biodiverse reef ecosystems, are under threat from warming oceans. Reefs provide essential ecological services, including food, income from tourism, nutrient cycling, waste removal, and the absorption of wave energy to mitigate erosion. Here, we studied the coral thermal stress response using network methods to analyze transcriptomic and polar metabolomic data generated from the Hawaiian rice coral Montipora capitata. Coral nubbins were exposed to ambient or thermal stress conditions over a 5-week period, coinciding with a mass spawning event of this species. The major goal of our study was to expand the inventory of thermal stress-related genes and metabolites present in M. capitata and to study gene-metabolite interactions. These interactions provide the foundation for functional or genetic analysis of key coral genes as well as provide potentially diagnostic markers of pre-bleaching stress. A secondary goal of our study was to analyze the accumulation of sex hormones prior to and during mass spawning to understand how thermal stress may impact reproductive success in M. capitata. Methods M. capitata was exposed to thermal stress during its spawning cycle over the course of 5 weeks, during which time transcriptomic and polar metabolomic data were collected. We analyzed these data streams individually, and then integrated both data sets using MAGI (Metabolite Annotation and Gene Integration) to investigate molecular transitions and biochemical reactions. Results Our results reveal the complexity of the thermal stress phenome in M. capitata, which includes many genes involved in redox regulation, biomineralization, and reproduction. The size and number of modules in the gene co-expression networks expanded from the initial stress response to the onset of bleaching. The later stages involved the suppression of metabolite transport by the coral host, including a variety of sodium-coupled transporters and a putative ammonium transporter, possibly as a response to reduction in algal productivity. The gene-metabolite integration data suggest that thermal treatment results in the activation of animal redox stress pathways involved in quenching molecular oxygen to prevent an overabundance of reactive oxygen species. Lastly, evidence that thermal stress affects reproductive activity was provided by the downregulation of CYP-like genes and the irregular production of sex hormones during the mass spawning cycle. Overall, redox regulation and metabolite transport are key components of the coral animal thermal stress phenome. Mass spawning was highly attenuated under thermal stress, suggesting that global climate change may negatively impact reproductive behavior in this species