Introduction to the session: Creating a Regional Vision for Urban Reef Restoration: A Case Study from Biscayne, FL

In our presentation, we will describe the development and achievements of the coral propagation and restoration program started by the University of Miami in Biscayne National Park in 2007. We will describe our research on the growth and survivorship of different genotypes of staghorn coral both in the nursery and once outplanted onto different reefs, the impacts of damselfish occupation, bleaching and disease outbreaks, the genotypic and genetic structure of staghorn populations, and the physical and genetic connectivity of staghorn populations across the Florida Reef Tract.

Assisted migration of corals over latitudinal gradients has been proposed as a strategy for increasing coral thermotolerance, but is currently considered high-risk, due to the potential for the unwanted introduction of pathogens or invasive species, and genetic risks such as outbreeding depression. A pragmatic way of minimizing these risks is to identify thermal heterogeneity in seascapes over much smaller scales and use corals from locally warmer conditions as source populations for restoration. We investigated this approach in Miami, Florida, by testing whether corals collected from different sites spanning a natural thermal break in Biscayne Bay varied significantly in their thermotolerance. Thirty genotypes of staghorn coral (Acropora cervicornis) were collected from sites spanning this break and maintained in common-garden conditions in three nurseries for 2-10 years. We then used a laboratory heat stress experiment to test the thermotolerance of these genotypes, based on reductions in symbiont density (measured as cell counts and as symbiont-to-host cell ratios), photochemical efficiency (Fv/Fm), and chlorophyll. We grouped genotypes by thermotolerance and found higher thermotolerance was associated with the southern collection locations, with an increase of just 0.25oC in maximum monthly mean (MMM) temperature selecting for genotypes that were twice as thermotolerant (measured as time spent at 32.5oC for a similar decline in response variable) compared to susceptible genotypes. However, thermotolerant genotypes also grew ~25% more slowly at nursery sites compared to susceptible genotypes. When interpreted using high-resolution climate models, these data indicate that assisted translocation of genotypes from southern sites to northern sites – a distance of < 15km – could extend bleaching horizons (measured as time to annual severe bleaching) by >20 years compared to outplanting nursery corals at their original collection sites. Assisted translocation within local restoration areas may help restore reefs which grow more slowly but are more climate resilient, and help buy time for the development of additional interventions.

Current research has shown strong differences within species between coral colonies in their resistance to bleaching temperatures. Sources of variation range from the symbiont, acclimation by the host, adaptation by the host and microbiome. New efforts in the Pacific show that choosing heat resistant colonies on reefs can lead to more heat resistance in coral nurseries made from fragments of these colonies. Genome and transcriptome and selective breeding experiments in Pacific species of the genus Acropora suggest that many coral genes affect heat resistance. In the Caribbean, Acropora colonies also show strong differences in heat resistance in the field and in lab common garden settings. High genetic diversity still exists even in threatened populations, but new experiments show that multiple stressors such as heat and disease can potentially erode this diversity. Standing genetic diversity can be a source for heat tolerant corals and thus conservation strategies that promote the conservation of coral genetic diversity are recommended.

The risk of flooding is increasing for coastal cities around the world and there is great interest in identifying effective solutions that reduce it. It is increasingly clear that natural defenses such as mangroves and reefs can play significant roles in coastal protection and these are particularly critical in south Florida and the Biscayne region. There are significant opportunities to support restoration of these critical habitats for flood defense. But to be able to access these funds, we must be able to rigorously value their flood protection benefits; the good news is that we can. In this presentation, we will show some of the critical values of reef and mangrove habitats in the Biscayne Bay region.

Interventions to save coral reefs are deemed critical and urgent to protect these exceptional ecosystems and those who depend on them. Increasing losses in ecosystem services including coastal protection, fisheries resources, and support for tourism and cultural practices have demonstrated the need for well designed and implemented restoration programs. New molecular tools in the disciplines of genomics, proteomics, metabolomics and transcriptomics can help guide restoration activities and provide a basis for evaluating program efficacy. Criteria for the selection of wild and brood stock and the cultivation of resistant variants that can survive anthropogenic stressors is essential for the success of restoration efforts and associated interventions. Protein expression is a valuable tool for diagnosing specific local stressors of highest concern, and the genotypes of corals most likely to survive. The Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) databases are now usable to help guide interventions for corals. Genetic analyses can determine those genotypes with inherent resistance to individual and multiple stressors, and transcriptomic data can provide critical information on gene expression in response to changing environmental conditions. The Florida Keys and Biscayne Bay provide an appropriate set of sites for the testing and application of techniques. To make the most of limited financial, institutional and human resources that can be devoted to coral reef restoration, the application of emerging molecular tools can be foundational in the design, implementation and evaluation of such activities.

Panel discussion.

The Miami-Dade portion of the Florida Reef Tract consists mostly of non-accretionary hard bottom coral communities organized into patchy platform and shelf edge reefs. Live hard coral cover is very low in the wake of coral disease, thermal shocks and hurricanes. However, the reefs are high value due to dense nearby user populations, ready accessibility, and presence of a national park. The situation is suitable for coral reef restoration, with good potential for enhancing biodiversity maintenance and the provisioning of food, recreation and tourism opportunities. This portion of the reef estate is proximal to major impactors including human population expansion, rapid urbanization, and sacrifice of habitat destruction that have together severely compromised ecological landscape function. We have begun to examine the key factors bearing on the risk-benefit for reef restoration in the Biscayne marine ecosystem, using a combination of remote sensing, GIS, long-term habitat monitoring, and dynamic modeling of ecosystem service flows and tradeoffs. Early results suggest that if coral reefs and adjacent seagrass and estuarine environments are to be restored, there is need to adopt a landscape view with plans for aggressive and comprehensive stewardship, extensive restoration interventions, and close attention to the amelioration of enabling conditions for coral survival. This is particularly true within Biscayne National Park.

The coastal bays and coral reefs of Biscayne support diverse natural resources, and lucrative tourism and fishing industries that generate billions of dollars in regional economic activity. Biscayne, the nation’s largest marine National Park, is visited by more than 250,000 persons annually due to its proximity to south Florida’s burgeoning 6 million-person population. A host of consumptive and sport fisheries target fish and shellfish across the seascape, most intensively the snapper-grouper complex. Other directed commercial fisheries capture primary prey species (pink shrimp, baitfish) that deleteriously affects food availability for reef fishes and elite sportsfishes like tarpon, bonefish, and permit. Overfishing, prey reduction, and habitat degradation are principal threats. Ecological persistence and economic sustainability is a key conservation concern as resource demand continues to escalate. “Sustainability” in this context is the ability of an exploited fish population to produce goods and services (including yields) at suitable levels in the short-term, while maintaining sufficient stock reproductive capacity to continue providing these goods and services at similar levels into the indefinite future. This talk explores fishery sustainability risks and provides strategic advice to enhance reef restoration activities that will improve management decision-making capacity for the National Parks and State of Florida.

Biscayne National Park, located in Miami’s back yard, protects extensive mangrove forests, seagrass meadows, the northernmost Florida Keys, and a portion of the Florida Keys Reef Tract. Status as a national park offers a level of protection from some local stressors, yet the park’s proximity to the Miami metropolitan area provides its own set of challenges. Over the past fifteen years, the National Park Service has engaged in sustained intensive reef restoration efforts, with support from damage assessment case settlements and grants and through key partnerships. Most visitors enjoy the park by boat, and park waters support active trap fisheries. The park’s Habitat Restoration Program addresses direct impacts to reef resources from vessel strikes, vessel debris, derelict fishing gear, and storms, as well as indirect effects that have drastically reduced coral populations. The scale, complexity, and ecological benefit of reef restoration efforts in the park continue to grow in parallel with advances in the field. Examples of substrate stabilization, reef habitat reconstruction, debris removal, and coral population enhancement through nursery collaborations and larval propagation will be presented. This body of work has helped to advance restoration concepts from the research realm to practical and ecological meaningful scales. Active restoration measures that conserve the park’s existing reef resources and build diverse coral populations are critical to their continued existence in a changing future.

Panel discussion.