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Effects of herbivory by the urchin Diadema antillarum on early restoration success of the coral Acropora cervicornis in the central Caribbean
Abstract
In an era of coral reef decline, coral restoration is receiving increasing attention, with many recent developments in culture and transplant techniques. However, how the ecological processes operating on coral reefs influence the success of restoration efforts remains largely unexplored, particularly during the first months after outplanting which are considered crucial for colony survival. Herbivory is a key process well-known to maintain a coral-dominated state, and in the Caribbean Sea, the long-spine urchin Diadema antillarum is thought to aid coral success by removing algae from seafloor substrate that might otherwise outcompete coral outplants. In this study, we conducted a three-month manipulative experiment in southeastern Dominican Republic to test the effect of Diadema antillarum density on percent living tissue and growth rate of outplanted fragments of the critically endangered coral species Acropora cervicornis. Increasing herbivore density had no significant effect on coral survival or growth but did increase the percent of living tissue when urchin abundance was 3× ambient levels. The greatest growth and survival outcomes were instead related to the initial size of the outplanted coral and were reduced through predation by the fireworm Hermodice carunculata. Our results highlight the potential importance of considering ecological processes like herbivory and predation to maximize the success of ecological restoration.
... Según Geraldes (2003), la República Dominicana cuenta con una extensa distribución de los arrecifes de coral a los largo de su cos- Grupo Puntacana y Fundación Propagas) así como también el surgimiento de la Red Arrecifal Dominicana (RAD), el Consorcio Dominicano de Restauración Costera (CDRC) y su inserción en redes de restauración y monitoreo regional como AGRRA y la Red de Resiliencia Arrecifal (RNN), ha posicionado a la República Dominicana como uno de los países Caribeños líderes en conservación, monitoreo y restauración de arrecifes de coral (Calle-Treviño et al. 2018, Bayraktarov et al. 2020, Cano et al. 2021, Cortés-Useche et al. 2021, Sellares-Blaco et al. 2021. Los trabajos relacionados con arrecifes de coral han sido extremadamente prolíficos para el país, los cuales se encuentran compilados en una revisión bibliográfica reciente (Irazabal, 2018). ...
Los arrecifes coralinos se consideran ecosistemas análogos a los bosques lluviosos, en términos de biodiversidad y variedad de bienes y servicios ecosistémicos que proveen. La pérdida acelerada de áreas coralinas a escala global es conocida como la crisis de los arrecifes, la cual es particularmente tangible en el Caribe. Aunque se sabe que la combinación de factores globales y locales son las causas del declive del estado de salud de los arrecifes, la importancia relativa e identidad de cada uno de estos factores puede ser diferente entre geografías. En la República Dominicana, los arrecifes coralinos son de gran importancia debido a su valor ecológico y económico. Al igual que otras islas del Caribe, los arrecifes en República Dominicana se han visto afectados por la crisis global, y en muchos casos se ha reportado su deterioro. Este trabajo tiene por objetivo identificar los factores globales y locales que han impactado la salud de los arrecifes dominicanos en las últimas décadas, así como puntualizar las acciones que se han llevado a cabo en el país para avanzar en la conservación de estos ecosistemas. En las últimas décadas, docenas de estudios de salud arrecifal han identificado las principales amenazas para los arrecifes de la isla. Los resultados muestran que los eventos masivos de blanqueamiento a causa de estrés térmico por calentamiento de las masas de agua, la ocurrencia de huracanes y eventos epizoóticos de enfermedades coralinas, han disminuido la cobertura de coral vivo. La sobrepesca es un problema serio, especialmente la extracción de peces herbívoros. Asimismo, el desarrollo costero acelerado, la deforestación de bosques de manglar, la intervención de cuencas y la entrada crónica de nutrientes, son factores que combinados pueden explicar el reemplazo de arrecifes dominados por corales y la transición hacia arrecifes dominados por algas. Si bien la reducción de los impactos globales escapa de las estrategias de implementación local, el desarrollo de planes de manejo integrado de costas y estrategias mancomunadas para reducir la presión de la pesca, aunado con la educación ambiental, pueden ofrecer una solución a mediano plazo para conservar los arrecifes de coral en la República Dominicana.
... Additionally, co-restoration of particularly beneficial individual species can improve the survival and growth rate of coral. For example, programmes in the Caribbean are experimenting with co-restoration of Diadema sea urchins and coral, because sea urchins can elevate grazing function on restored ecosystems and enhance survival and growth rates of outplanted corals [16,84]. Conversely, other species can be detrimental to coral growth, and efforts should be made to reduce their impact [116]. ...
Local and global stressors have led to rapid declines in coral reef health around the world. A range of active restoration techniques have recently been introduced in attempts to stem and reverse this decline, but their efficacy is debated. In particular, restoration faces the challenge of scale; successful projects must be deployed quickly over large areas, without being prohibitively expensive.
Indonesia has more coral reefs – and more coral reef restoration programmes – than any other country on Earth. The past two decades have seen a rapid expansion in the scale of Indonesia’s restoration efforts. Having started in the 1980s, there are now hundreds of individual programmes across the country, several of which have outplanted tens of thousands of corals. Here, we identify ten different social, economic and environmental approaches that have contributed to this scaling up of reef restoration in Indonesia. We discuss the theoretical basis for each approach and provide case studies of their implementation from sixteen different Indonesian programmes.
In combination, these diverse approaches have created opportunities to increase the operational efficiency, spatial scale, speed of deployment and social inclusivity of reef restoration in many different contexts. Their examples represent valuable learning experiences, highlighting a range of mechanisms through which management and policy interventions might aim to increase the scale of coral reef restoration. By combining ecological, social and economic strategies in a multi-dimensional approach to scale-up, reef restoration can deliver more beneficial and equitable outcomes locally, regionally and globally.
... To conclude, because of the paucity of time series available assessing the spatial and temporal trends of D. antillarum in the Dominican Republic is challenging. Determining if this species is recovering in the Caribbean is particularly relevant for ongoing coral restoration efforts, particularly in Bayahibe, where herbivory by this sea urchin has been shown to benefit the survivorship of coral outplant (Cano et al. 2021). ...
The sea urchin Diadema antillarum is an herbivore that plays an important ecological role in controlling benthic community structure in Caribbean reefs. After the mass mortality documented between 1982-1983, their populations were reduced by 94-99% triggering a phase shift from coral to macroalgae-dominated benthic communities across the Caribbean. Almost 4 decades after its regional collapse, it is not clear weather D. antillarum populations are recovering, thus local surveys are valuable to track the fate of this herbivore. This study aims to determine the population structure of this sea urchin in a shallow reef located southeast of the Dominican Republic. We conducted a visual survey in three haphazardly selected sites of the reef studying a total surface of 90 m2 in which test size and D. antillarum densities were measured. Overall, the mean density of D. antillarum was 1.77 ± 1.07 ind/ m2 (Mean ± SD) with an average test size of 67.3 ± 22.7 mm (Mean ± SD) a median of 70 mm and a mode of 80 mm. Test diameter had a platykurtic distribution (kurtosis = 2.53) slightly skewed to the left (skewness = -0.1). This information is valuable to establish a local baseline to follow up the population dynamics of this key species.
... While site selection is key for success and is extremely valuable for scaling up these efforts (Foo and Asner, 2019), a more complete understanding of coral species biology, and ecology is fundamental for successful coral restoration. Coral outplant survivorship not only depends on habitat suitability and the features of the physical environment Silliman, 2017, Ladd et al., 2018), but is also determined by a series of biological process such as predation (Glynn, 1962;Baums et al., 2003;Miller et al., 2014), herbivory (Burkepile and Hay, 2010;Shaver and Silliman., 2017;Ladd et al., 2018;Lefcheck et al., 2019;Cano et al., 2021), disease (Hernández-Delgado et al., 2014), and genetic identity of coral outplants (Drury et al., 2017). These types of variables can vary greatly across space and time and are undetectable in remotely sensed images. ...
Over the past decade, coral restoration efforts have increased as reefs continue to decline at unprecedented rates. Identifying suitable coral outplanting locations to maximize coral survival continues to be one of the biggest challenges for restoration practitioners. Here, we demonstrate methods of using derivatives from imaging spectroscopy from the Global Airborne Observatory (GAO) to identify suitable coral outplant sites and report on the survival rates of restored coral at those sites. Outplant sites for a community-based, citizen science outplant event in Bávaro, Dominican Republic, were identified using expert-defined criteria applied to a suitability model from data layers derived from airborne imagery. Photo quadrat analysis of the benthic community confirmed the accuracy of airborne remote sensing maps with live coral cover averaging 3.5–4% and mean algal cover (macro algae and turf) ranging from 28 to 32%. Coral outplant sites were selected at 3–7 m depth with maximized levels of habitat complexity (i.e., rugosity) and live coral cover and minimized levels of macroalgal cover, as predicted by the imaging spectrometer data. In November 2019, 1,722 Acropora cervicornis fragments (80–180 mm in length) were outplanted to these sites. Surveys conducted in January 2020 in four of these sites confirmed that 92% of outplants survived after 3 months. By October 2020 (11 months after outplanting), survivorship remained above 76%. These results demonstrate higher than average success rates for coral outplant survival for this species. An online tool was developed to enable replication and facilitate future selection of coral restoration sites. Our objective is to present a case study that uses GAO-derived map products within a suitability model framework to provide a quantitative and replicable method for selecting coral restoration sites with the goal of increasing outplant survival over time.
Release from herbivory is a factor underpinning coral replacement by macroalgae. Once macroalgae have achieved dominance, shifts back to the coral-dominated state can be hindered by stabilizing feedbacks. Thus, restoring herbivore assemblages alone can be insufficient to trigger coral recovery. However, herbivores could control macroalgal recovery in the aftermath of physical disturbances removing macroalgae. Diadematid urchins at Moorea (French Polynesia) have collapsed in the last decade. By means of a manipulative field experiment, we tested the interactive effects of physical disturbance and increased diadematid densities on macroalgae inside the lagoon. Massive Porites colonies, referred to as ‘bommies’, were assigned to 3 different macroalgal removal treatments (removal of stipes and fronds of the canopy-forming macroalgae Turbinaria ornata and Sargassum pacificum , total removal of erect macroalgae or untouched) and exposed to 3 different urchin densities (absent, low [~0.5 ind. m ⁻² ], and intermediate [~1 ind. m ⁻² ]). After 1 yr, sea urchins had no effect on the covers of S. pacificum and T. ornata when macroalgal canopies were left untouched. Urchins could control the recovery of S. pacificum on total macroalgal removal bommies, but not that of T. ornata . However, urchins, even when at intermediate densities, did not generate major changes in the structure of benthic assemblages on experimental bommies. Our study indicates that a moderate increase in diadematid densities is unlikely to reduce the extent of macroalgal stands in Moorea back reefs unless associated with the recovery of other herbivore guilds able to remove adult macroalgae (i.e. browsers).
Coral reefs worldwide are degrading due to climate change, overfishing, pollution, coastal development, coral bleaching, and diseases. In areas where the natural recovery of an ecosystem is negligible or protection through management interventions insufficient, active restoration becomes critical. The Reef Futures symposium in 2018 brought together over 400 reef restoration experts, businesses, and civil organizations, and galvanized them to save coral reefs through restoration or identify alternative solutions. The symposium highlighted that solutions and discoveries from long-term and ongoing coral reef restoration projects in Spanish-speaking countries in the Caribbean and Eastern Tropical Pacific were not well known internationally. Therefore, a meeting of scientists and practitioners working in these locations was held to compile the data on the extent of coral reef restoration efforts, advances and challenges. Here, we present unpublished data from 12 coral reef restoration case studies from five Latin American countries, describe their motivations and techniques used, and provide estimates on total annual project cost per unit area of reef intervened, spatial extent as well as project duration. We found that most projects used direct transplantation, the coral gardening method, micro-fragmentation or larval propagation, and aimed to optimize or scale-up restoration approaches (51%) or provide alternative, sustainable livelihood opportunities (15%) followed by promoting coral reef conservation stewardship and re-establishing a self-sustaining, functioning reef ecosystems (both 13%). Reasons for restoring coral reefs were mainly biotic and experimental (both 42%), followed by idealistic and pragmatic motivations (both 8%). The median annual total cost from all projects was $93,000 USD (range: $10,000 USD—$331,802 USD) (2018 dollars) and intervened a median spatial area of 1 ha (range: 0.06 ha—8.39 ha). The median project duration was 3 years; however, projects have lasted up to 17 years. Project feasibility was high with a median of 0.7 (range: 0.5–0.8). This study closes the knowledge gap between academia and practitioners and overcomes the language barrier by providing the first comprehensive compilation of data from ongoing coral reef restoration efforts in Latin America.
The mass mortality of acroporid corals has transformed Caribbean reefs from coral- to macroalgal-dominated habitats since systematic monitoring began in the 1970s. Declines have been attributed to overfishing, pollution, sea urchin and coral disease, and climate change, but the mechanisms are unresolved due to the dearth of pre-1970s data. We used paleoecological, historical, and survey data to track Acropora presence and dominance throughout the Caribbean from the prehuman period to present. Declines in dominance from prehuman values first occurred in the 1950s for Acropora palmata and the 1960s for Acropora cervicornis , decades before outbreaks of acroporid disease or bleaching. We compared trends in Acropora dominance since 1950 to potential regional and local drivers. Human population negatively affected and consumption of fertilizer for agriculture positively affected A. palmata dominance, the latter likely due to lower human presence in agricultural areas. The earlier, local roots of Caribbean Acropora declines highlight the urgency of mitigating local human impacts.
Acropora cervicornis is a structurally and functionally important Caribbean coral species. Since the 1980s, it has suffered drastic population losses with no signs of recovery and has been classified as a critically endangered species. Its rapid growth rate makes it an excellent candidate for coral restoration programs. In 2011, the Fundación Dominicana de Estudios Marinos (Dominican Marine Studies Foundation, FUNDEMAR) began an A . cervicornis restoration program in Bayahibe, southeast Dominican Republic. In this study, we present the methodology and results of this program from its conception through 2017, a preliminary analysis of the strong 2016 and 2017 cyclonic seasons in the greater Caribbean, and a genetic characterization of the “main nursery”. The mean survival of the fragments over 12 months was 87.45 ± 4.85% and the mean productivity was 4.01 ± 1.88 cm year ⁻¹ for the eight nurseries. The mean survival of six outplanted sites over 12 months was 71.55 ± 10.4%, and the mean productivity was 3.03 ± 1.30 cm year ⁻¹ . The most common cause of mortality during the first 12 months, in both nurseries and outplanted sites, was predation by the fireworm, Hermodice carunculata . We identified 32 multilocus genotypes from 145 total analyzed individuals. The results and techniques described here will aid in the development of current and future nursery and outplanted site restoration programs.
Natural population recovery of Acropora palmata, A. cervicornis and their hybrid, Acropora prolifera , have fluctuated significantly after their Caribbean-wide, disease-induced mass mortality in the early 1980s. Even though significant recovery has been observed in a few localities, recurrent disease outbreaks, bleaching, storm damage, local environmental deterioration, algae smothering, predation, low sexual recruitment and low survivorship have affected the expected, quick recovery of these weedy species. In this study, the status of three recovering populations of A. cervicornis and two of A. prolifera were assessed over one year using coral growth and mortality metrics, and changes in their associated algae and fish/invertebrate communities in three localities in the La Parguera Natural Reserve (LPNR), southwest coast of Puerto Rico. Five branches were tagged in each of 29, medium size (1–2 m in diameter) A. cervicornis and 18 A. prolifera colonies in the Media Luna, Mario and San Cristobal reefs off LPNR. Branches were measured monthly, together with observations to evaluate associated disease(s), algae accumulation and predation. A. cervicornis grew faster [3.1 ± 0.44 cm/month (= 37.2 cm/y)] compared to A. prolifera [2.6 ± 0.41 cm/month (= 31.2 cm/y)], and growth was significantly higher during Winter-Spring compared to Summer-Fall for both taxa (3.5 ± 0.58 vs. 0.53 ± 0.15 cm/month in A. cervicornis, and 2.43 ± 0.71 vs. 0.27 ± 0.20 cm/month in A. prolifera , respectively). Algal accumulation was only observed in A. cervicornis, and was higher during Spring-Summer compared to Fall-Winter (6.1 ± 0.91 cm/month and 3.8 ± 0.29 cm/month, respectively, (PERMANOVA, df = 2, MS = 10.2, p = 0.37)). Mortality associated with white band disease, algae smothering and fish/invertebrate predation was also higher in A. cervicornis and varied among colonies within sites, across sites and across season. The balance between tissue grow and mortality determines if colonies survive. This balance seems to be pushed to the high mortality side often by increasing frequency of high thermal anomalies, inducing bleaching and disease outbreaks and other factors, which have historically impacted the natural recovery of these taxa in the La Parguera Natural Reserve in Puerto Rico and possibly other areas in the region. Overall, results indicate variability in both growth and mortality rates in both taxa across localities and seasons, with A. cervicornis showing overall higher mortalities compared to A. prolifera .
Coral reef ecosystems have suffered an unprecedented loss of habitat-forming hard corals in recent decades. While marine conservation has historically focused on passive habitat protection, demand for and interest in active restoration has been growing in recent decades. However, a disconnect between coral restoration practitioners, coral reef managers and scientists has resulted in a disjointed field where it is difficult to gain an overview of existing knowledge. To address this, we aimed to synthesise the available knowledge in a comprehensive global review of coral restoration methods, incorporating data from the peer-reviewed scientific literature, complemented with grey literature and through a survey of coral restoration practitioners. We found that coral restoration case studies are dominated by short-term projects, with 60% of all projects reporting less than 18 months of monitoring of the restored sites. Similarly, most projects are relatively small in spatial scale, with a median size of restored area of 100 m². A diverse range of species are represented in the dataset, with 229 different species from 72 coral genera. Overall, coral restoration projects focused primarily on fast-growing branching corals (59% of studies), and report survival between 60 and 70%. To date, the relatively young field of coral restoration has been plagued by similar ‘growing pains’ as ecological restoration in other ecosystems. These include 1) a lack of clear and achievable objectives, 2) a lack of appropriate and standardised monitoring and reporting and, 3) poorly designed projects in relation to stated objectives. Mitigating these will be crucial to successfully scale up projects, and to retain public trust in restoration as a tool for resilience based management. Finally, while it is clear that practitioners have developed effective methods to successfully grow corals at small scales, it is critical not to view restoration as a replacement for meaningful action on climate change.
Coral reefs in the Florida Keys have degraded in recent decades, prompting efforts to re-establish populations of staghorn coral, Acropora cervicornis, to restore structure and ecological function. However, predation on these corals by the corallivorous gastropod, Coralliophila galea, has been a substantial and chronic impediment to restoration efforts. Therefore, we conducted a series of manipulative laboratory experiments and a 2-week, in situ proof-of-concept trial to determine whether Thais deltoidea, a carnivorous gastropod that co-occurs with C. galea, can control C. galea corallivory and thus improve A. cervicornis survival. Our laboratory results showed that T. deltoidea preys upon C. galea, although it is not a preferred prey choice. Nevertheless, treatments with T. deltoidea had significantly higher percentages of live coral tissue than when T. deltoidea was absent. This occurred not only because T. deltoidea consumed C. galea, but also because the presence of T. deltoidea elicited an escape response in C. galea, significantly reducing the amount of time C. galea spent feeding on A. cervicornis colonies. This trophic relationship was also seen in our in situ proof-of-concept trial. We observed significantly fewer C. galea on A. cervicornis when T. deltoidea was present which led to a higher, if not statistically significant, percentage of live tissue on our A. cervicornis outplants. Ecological processes need to be incorporated into coral reef ecosystem restoration to achieve positive outcomes. Integrating T. deltoidea into coral restoration efforts may improve success by mitigating C. galea corallivory through the non-consumptive, risk-adverse, escape response that T. deltoidea provokes, initiating a trophic cascade that improves the long-term survival of outplanted corals. Further research is needed to determine the long-term efficacy of this approach, but the addition of gastropod trophodynamics to coral reef ecosystem restoration may prove useful.
An approach that tackles the underlying causes of coral-reef decline could be applied to other habitats, argue Tiffany H. Morrison, Terry P. Hughes and colleagues. An approach that tackles the underlying causes of coral-reef decline could be applied to other habitats, argue Tiffany H. Morrison, Terry P. Hughes and colleagues. Turtle swimming over bleached coral, Heron Island, Australia.
Increasing heat stress due to global climate change is causing coral reef decline, and the Caribbean has been one of the most vulnerable regions. Here, we assessed three decades (1985–2017) of heat stress exposure in the wider Caribbean at ecoregional and local scales using remote sensing. We found a high spatial and temporal variability of heat stress, emphasizing an observed increase in heat exposure over time in most ecoregions, especially from 2003 identified as a temporal change point in heat stress. A spatiotemporal analysis classified the Caribbean into eight heat-stress regions offering a new regionalization scheme based on historical heat exposure patterns. The temporal analysis confirmed the years 1998, 2005, 2010–2011, 2015 and 2017 as severe and widespread Caribbean heat-stress events and recognized a change point in 2002–2004, after which heat exposure has been frequent in most subsequent years. Major heat-stress events may be associated with El Niño Southern Oscillation (ENSO), but we highlight the relevance of the long-term increase in heat exposure in most ecoregions and in all ENSO phases. This work produced a new baseline and regionalization of heat stress in the basin that will enhance conservation and planning efforts underway.
Increased loadings of nitrogen (N) from fertilizers, top soil, sewage, and atmospheric deposition are important drivers of eutrophication in coastal waters globally. Monitoring seawater and macroalgae can reveal long-term changes in N and phosphorus (P) availability and N:P stoichiometry that are critical to understanding the global crisis of coral reef decline. Analysis of a unique 3-decade data set for Looe Key reef, located offshore the lower Florida Keys, showed increased dissolved inorganic nitrogen (DIN), chlorophyll a, DIN:soluble reactive phosphorus (SRP) ratios, as well as higher tissue C:P and N:P ratios in macroalgae during the early 1990s. These data, combined with remote sensing and nutrient monitoring between the Everglades and Looe Key, indicated that the significant DIN enrichment between 1991 and 1995 at Looe Key coincided with increased Everglades runoff, which drains agricultural and urban areas extending north to Orlando, Florida. This resulted in increased P limitation of reef primary producers that can cause metabolic stress in stony corals. Outbreaks of stony coral disease, bleaching, and mortality between 1995 and 2000 followed DIN enrichment, algal blooms, and increased DIN:SRP ratios, suggesting that eutrophication interacted with other factors causing coral reef decline at Looe Key. Although water temperatures at Looe Key exceeded the 30.5 °C bleaching threshold repeatedly over the 3-decade study, the three mass bleaching events occurred only when DIN:SRP ratios increased following heavy rainfall and increased Everglades runoff. These results suggest that Everglades discharges, in conjunction with local nutrient sources, contributed to DIN enrichment, eutrophication, and increased N:P ratios at Looe Key, exacerbating P limitation, coral stress and decline. Improved management of water quality at the local and regional levels could moderate N inputs and maintain more balanced N:P stoichiometry, thereby reducing the risk of coral bleaching, disease, and mortality under the current level of temperature stress.
Coastal development and climate change are dramatically increasing the risks of flooding, erosion, and extreme weather events. Coral reefs and other coastal ecosystems act as natural defenses against coastal hazards, but their degradation increases risk to people and property. Environmental degradation, however, has rarely been quantified as a driver of coastal risk. In Quintana Roo, Mexico, a region on the Mexican Caribbean coast with an annual tourism economy of 10 billion USD, coral reefs constitute a natural barrier against flooding from hurricanes. This study spatially quantifies the risk reduction benefits of the Mesoamerican Reef in Quintana Roo for people, buildings, and hotel infrastructure. The risk reduction benefits are substantial. For example, the reefs prevented 43% additional damage during Hurricane Dean in (2007) and provide nowadays hazard risk reduction for 4.3% of the people, 1.9% of the built capital, and 2.4% of the hotel infrastructure, per year. The annual benefits are estimated in 4,600 people, 42 million USD damage prevention for buildings, and 20.8 million USD for hotel infrastructure. The study also compares the risk reduction of coral reefs with (i) the protection offered by dunes and (ii) the increase in coastal risk from sea-level rise (SLR). The risk reduction of dunes is more critical where there are no coral reefs offshore and for small return-periods storms. Sea-level rise, however, will make the more frequent storms more impactful and will drive significant increases in annual expected damages across the region. However, we demonstrate that, in coral reef environments, the contribution of reef degradation to coastal risk is larger than the expected increase in risk from SLR. However, the spatial distribution of the risk reduction benefits from reefs differs for people and infrastructure, and in particular for hotels, which receive the most protection from reefs. Furthermore, many sections present larger benefits than the typical costs of restoration. This valuation makes a compelling case for protecting and maintaining this natural infrastructure for its risk reduction service, but also allows the development of piloting innovative strategies, such as risk finance and insurance strategies, that can align environmental and risk management goals.
Coral reefs face an uncertain future and may not recover naturally from anthropogenic climate change. Coral restoration is needed to rehabilitate degraded reefs and to sustain biodiversity. There is a need for baseline data on global reef distribution, composition, and condition to provide targets for conservation and restoration. Remote sensing can address this issue and is currently underutilized in reef research and restoration. This synthesis integrates current capabilities of remote sensing with key reef restoration criteria, to facilitate coral restoration success. Research into the development of a spectral database for corals, linking habitat type and extent with predator abundance, and identification of species-specific acoustic signatures are needed to advance the use of remote sensing in reef restoration design and monitoring. Reciprocally, reef restoration efforts should innovate at ecosystem, regional, and global levels using remote sensing, to preserve as much of the coral reef biome as possible with continued ocean-climate change.
There is now a general consensus that biodiversity positively affects ecosystem functioning. This consensus, however, stems largely from small-scale experiments, raising the question of whether diversity effects operate at multiple spatial scales and flow on to affect ecosystem structure in nature. Here, we quantified rates of fish herbivory on algal turf communities across multiple coral reefs spanning >1000 km of coastline in the Dominican Republic. We show that mass-standardized herbivory rates are best predicted by herbivore biomass and herbivore species richness both within (α-diversity) and across sites in the region (β-diversity). Using species-diversity models, we demonstrate that many common grazer species are necessary to maximize the process of herbivory. Last, we link higher herbivory rates to reduced algal turf height and enhanced juvenile coral recruitment throughout the ecosystem. Our results suggest that, in addition to high herbivore biomass, conserving biodiversity at multiple scales is important for sustaining coral reef function.
This work presents an updated taxonomic list of the fish fauna of the coral reefs in the Southeastern Reefs Marine Sanctuary (SMASE) in the Dominican Republic. The inventory is the result of 360 visual surveys of coral reefs during the period 2013-2016. We recorded 150 species from 86 genera and 47 families, including 14 new records for the southeast coastline of the Dominican Republic. The families of fishes with the highest species number comprised Serranidae (16 species), Haemulidae (12 species) and Pomacentridae (10 species).
Acropora cervicornis
is the most widely used coral species for reef restoration in the greater Caribbean. However, outplanting methodologies (e.g., colony density, size, host genotype, and attachment technique) vary greatly, and to date have not been evaluated for optimality across multiple sites. Two experiments were completed during this study, the first evaluated the effects of attachment technique, colony size, and genotype by outplanting 405A. cervicorniscolonies, from ten genotypes, four size classes, and three attachment techniques (epoxy, nail and cable tie, or puck) across three sites. Colony survival, health condition, tissue productivity, and growth were assessed across one year for this experiment. The second experiment assessed the effect of colony density by outplanting colonies in plots of one, four, or 25 corals per 4 m2across four separate sites. Plot survival and condition were evaluated across two years for this experiment in order to better capture the effect of increasing cover. Colonies attached with a nail and cable tie resulted in the highest survival regardless of colony size. Small corals had the lowest survival, but the greatest productivity. The majority of colony loss was attributed to missing colonies and was highest for pucks and small epoxied colonies. Disease and predation were observed at all sites, but did not affect all genotypes, however due to the overall low prevalence of either condition there were no significant differences found in any comparison. Low density plots had significantly higher survival and significantly lower prevalence of disease, predation, and missing colonies than high density plots. These results indicate that to increase initial outplant success, colonies of many genotypes should be outplanted to multiple sites using a nail and cable tie, in low densities, and with colonies over 15 cm total linear extension.
Coral reefs support immense biodiversity and provide important ecosystem services to many millions of people. Yet reefs are degrading rapidly in response to numerous anthropogenic drivers. In the coming centuries, reefs will run the gauntlet of climate change, and rising temperatures will transform them into new configurations, unlike anything observed previously by humans. Returning reefs to past configurations is no longer an option. Instead, the global challenge is to steer reefs through the Anthropocene era in a way that maintains their biological functions. Successful navigation of this transition will require radical changes in the science, management and governance of coral reefs.
Caribbean populations of the long-spined sea urchin, Diadema antillarum (Philippi, 1845), have undergone two mass mortality events since the 1980s that have caused 93%–100% of individuals on any given reef to perish. Subsequently, coral recruitment and survival declined, in part due to algal overgrowth and an increase in secondary metabolites associated with macoalgae. For long-term macroalgal biomass removal, supplementation of D. antillarum via translocation, captive-rearing and release, or both, must be considered. This project aimed to (1) compare genetic diversity of D. antillarum (Philippi, 1845) from six reef locations in south Florida ranging from Biscayne National Park to the Dry Tortugas, and (2) determine whether two broodstock populations of mixed ancestry contain variation indicative of natural Florida populations. We found little genetic differentiation among natural locations and between natural and broodstock populations (highest pairwise FST was 0.0066). Moreover, genetic diversity was similar among all natural and broodstock populations (allelic richness and heterozygosity ranged from 22.6–24.4 and 0.937–0.956, respectively). Additionally, a Structure analysis suggested that all samples compose a single genetic cluster. These data suggest that natural populations of D. antillarum are genetically similar throughout the Florida Keys, from Dry Tortugas National Park through Biscayne National Park, and that captive-bred individuals could be used for reintroduction as part of a plan to re-establish healthy urchin populations throughout the Florida Keys.
Background
ImageJ is an image analysis program extensively used in the biological sciences and beyond. Due to its ease of use, recordable macro language, and extensible plug-in architecture, ImageJ enjoys contributions from non-programmers, amateur programmers, and professional developers alike. Enabling such a diversity of contributors has resulted in a large community that spans the biological and physical sciences. However, a rapidly growing user base, diverging plugin suites, and technical limitations have revealed a clear need for a concerted software engineering effort to support emerging imaging paradigms, to ensure the software’s ability to handle the requirements of modern science.
Results
We rewrote the entire ImageJ codebase, engineering a redesigned plugin mechanism intended to facilitate extensibility at every level, with the goal of creating a more powerful tool that continues to serve the existing community while addressing a wider range of scientific requirements. This next-generation ImageJ, called “ImageJ2” in places where the distinction matters, provides a host of new functionality. It separates concerns, fully decoupling the data model from the user interface. It emphasizes integration with external applications to maximize interoperability. Its robust new plugin framework allows everything from image formats, to scripting languages, to visualization to be extended by the community. The redesigned data model supports arbitrarily large, N-dimensional datasets, which are increasingly common in modern image acquisition. Despite the scope of these changes, backwards compatibility is maintained such that this new functionality can be seamlessly integrated with the classic ImageJ interface, allowing users and developers to migrate to these new methods at their own pace.
Conclusions
Scientific imaging benefits from open-source programs that advance new method development and deployment to a diverse audience. ImageJ has continuously evolved with this idea in mind; however, new and emerging scientific requirements have posed corresponding challenges for ImageJ’s development. The described improvements provide a framework engineered for flexibility, intended to support these requirements as well as accommodate future needs. Future efforts will focus on implementing new algorithms in this framework and expanding collaborations with other popular scientific software suites.
Electronic supplementary material
The online version of this article (doi:10.1186/s12859-017-1934-z) contains supplementary material, which is available to authorized users.
Over the past decades numerous studies havereported declines in stony corals and, in many cases, phase shifts to fleshy macroalgae. However, long-term studies documenting changes in other benthic reef organisms are scarce. Here, we studied changes in cover of corals, algal turfs, benthic cyanobacterial mats, macroalgae, sponges and crustose coralline algae at four reef sites of the Caribbean islands of Curac¸ao and Bonaire over a time span of 40 yr. Permanent 9 m2 quadrats at 10, 20, 30 and 40 m depth were photographed at 3- to 6-yr intervals from 1973 to 2013. The temporal and spatial dynamics in the six
dominant benthic groups were assessed based on image point-analysis. Our results show consistent patterns of benthic community change with a decrease in the cover of calcifying organisms across all sites and depths from 32.6
(1973) to 9.2% (2013) for corals and from 6.4 to 1% for crustose coralline algae. Initially, coral cover was replaced by algal turfs increasing from 24.5 (1973) to 38% around the early 1990s. Fleshy macroalgae, still absent in 1973, also proliferated covering 12% of the substratum approximately 20 yr later. However, these new dominants largely declined in abundance from 2002 to 2013 (11 and 2%, respectively), marking the rise of benthic cyanobacterial mats. Cyanobacterial mats became the most dominant benthic component increasing from a mere 7.1 (2002) to 22.2% (2013). The observed increase was paralleled by a small but significant increase in sponge cover (0.5 to 2.3%). Strikingly, this pattern of degradation and phase change occurred over the reef slope down to mesophotic depths of 40 m. These findings suggest that reefs dominated
by algae may be less stable than previously thought and that the next phase may be the dominance of slimy cyanobacterial mats with some sponges
Tropical coral reefs are among the most biologically diverse and economically important ecosystems on earth. Nevertheless, we found dramatic changes in coral communities on the reef slopes of Curaçao and Bonaire since 1973. Cover species. The data show a shift from communities dominated by framework building species (e.g., Orbicella spp.) to communities consisting of small opportunistic, phenotypically plastic, species, including few remaining structural colonies. Madracis mirabilis, Porites astreoides, Diploria strigosa, and Agaricia lamarcki are at present modest winners in the coral assemblage, although overall cover declined also for these species. Increased frequency and intensity of events inducing coral mortality and ongoing reduction in suitable hard substratum, provided by the remnants of large colony building species, could reduce the chance of these species to remain winners in the longer run. The observed loss in coral cover and the shift from larger structural to smaller
opportunistic species reduced reef carbonate production by 67% and therewith, in combination with a trend toward smaller coral colonies, reef complexity. Alarmingly, reefs at upper-mesophotic depths (30–40 m) did not escape the general degradation of the coral community. The negative effects are larger around densely populated areas where local stressors are adding to degradation caused, for instance, by region wide mass bleaching. Without proper conservation and management this already dramaticdegradation will continue and turn more and more coral species into losers<br/
Land-use change in the coastal zone has led to worldwide degradation of marine coastal ecosystems and a loss of the goods and services they provide. Restoration is the process of assisting the recovery of an ecosystem that has been degraded, damaged, or destroyed and is critical for habitats where natural recovery is hindered. Uncertainties about restoration cost and feasibility can impede decisions on whether, what, how, where, and how much to restore. Here, we perform a synthesis of 235 studies with 954 observations from restoration or rehabilitation projects of coral reefs, seagrass, mangroves, saltmarshes, and oyster reefs worldwide, and evaluate cost, survival of restored organisms, project duration, area, and techniques applied. Findings showed that while the median and average reported costs for restoration of one hectare of marine coastal habitat were around US$80 000 (2010) and US$1 600 000 (2010), respectively, the real total costs (median) are likely to be two to four times higher. Coral reefs and seagrass were among the most expensive ecosystems to restore. Mangrove restoration projects were typically the largest and the least expensive per hectare. Most marine coastal restoration projects were conducted in Australia, Europe, and USA, while total restoration costs were significantly (up to 30 times) cheaper in countries with developing economies. Community- or volunteer-based marine restoration projects usually have lower costs. Median survival of restored marine and coastal organisms, often assessed only within the first one to two years after restoration, was highest for saltmarshes (64.8%) and coral reefs (64.5%) and lowest for seagrass (38.0%). However, success rates reported in the scientific literature could be biased towards publishing successes rather than failures. The majority of restoration projects were short-lived and seldom reported monitoring costs. Restoration success depended primarily on the ecosystem, site selection, and techniques applied rather than on money spent. We need enhanced investment in both improving restoration practices and large-scale restoration.
In the past decade, significant efforts have been made to describe fish-habitat associations. However, most studies have oversimplified actual connections between fish assemblages and their habitats by using univariate correlations. The purpose of this study was to identify the features of habitat forming corals that facilitate and influences assemblages of associated species such as fishes. For this we developed three-dimensional models of colonies of
Acropora cervicornis
to estimate geometry (length and height), structural complexity (i.e., volume, density of branches, etc.) and biological features of the colonies (i.e., live coral tissue, algae). We then correlated these colony characteristics with the associated fish assemblage using multivariate analyses. We found that geometry and complexity were better predictors of the structure of fish community, compared to other variables such as percentage of live coral tissue or algae. Combined, the geometry of each colony explained 40% of the variability of the fish assemblage structure associated with this coral species; 61% of the abundance and 69% of fish richness, respectively. Our study shows that three-dimensional reconstructions of discrete colonies of
Acropora cervicornis
provides a useful description of the colonial structural complexity and may explain a great deal of the variance in the structure of the associated coral reef fish community. This demonstration of the strongly trait-dependent ecosystem role of this threatened species has important implications for restoration and conservation efforts.
Eight years ago (2007), the distribution and status of
Acropora palmata
was quantified throughout Los Roques archipelago in Venezuela. The aim was to produce a baseline study for this species which combined population genetics with demographic data. The results highlighted that
A. palmata
had the potential to recover in at least 6 out of 10 sites surveyed. Recovery potential was assumed to be high at sites with a relatively high abundance of the coral, low disease prevalence, high genetic diversity, and high rates of sexual reproduction. However, as noted, Zubillaga et al. (2008) realized recovery was still strongly dependent on local and regional stressors. In 2014 (this study), the status of
A. palmata
was re-evaluated at Los Roques. We increased the number of sites from 10 in the original baseline study to 106. This allowed us to assess the population status throughout the entirety of the MPA. Furthermore, we also identified local threats that may have hindered population recovery. Here, we show that
A. palmata
now has a relatively restricted distribution throughout the park, only occurring in 15% of the sites surveyed. Large stands of old dead colonies were common throughout the archipelago; a result which demonstrates that this species has lost almost 50% of its original distribution over the past decades. The majority of corals recorded were large adults (∼2 m height), suggesting that these older colonies might be less susceptible or more resilient to local and global threats. However, 45% of these surviving colonies showed evidence of partial mortality and degradation of living tissues. Interestingly, the greatest increase in partial mortality occurred at sites with the lowest levels of protection (${X}_{o}^{2}=5.4> {X}_{c}^{2}=4.5$;
df
= 4,
p
< 0.05). This may suggest there is a positive role of small scale marine management in assisting reef recovery. We also recorded a significant reduction (${X}_{\mathrm{exp}}^{2}=1 2 6.8> {X}_{\mathrm{cri}}^{2}=1 5.5$;
df
= 8;
p
< 0.05) in the density of
A. palmata
in sites that had previously been categorized as having a high potential for recovery. One explanation for this continued decline may be due to the fact that over the past 10 years, two massive bleaching events have occurred throughout the Caribbean with records showing that Los Roques has experienced unprecedented declines in overall coral cover. We therefore conclude that although local protection could promote recovery, the impacts from global threats such as ocean warming may hamper the recovery of this threatened species.
In recent decades, the cover of fleshy macroalgae has increased and coral cover has decreased on most Caribbean reefs. Coral mortality precipitated this transition, and the accumulation of macroalgal biomass has been enhanced by decreased herbivory and increased nutrient input. Populations of Acropora palmata (elkhorn coral) and A. cervicornis (staghorn coral), two of the most important framework-building species, have died throughout the Caribbean, substantially reducing coral cover and providing substratum for algal growth. Hurricanes have devastated local populations of Acropora spp. over the past 20–25 years, but white-band disease, a putative bacterial syndrome specific to the genus Acropora, has been a more significant source of mortality over large areas of the Caribbean region.
Paleontological data suggest that the regional Acropora kill is without precedent in the late Holocene. In Belize, A. cervicornis was the primary ecological and geological constituent of reefs in the central shelf lagoon until the mid-1980s. After constructing reef framework for thousands of years, A. cervicornis was virtually eliminated from the area over a ten-year period. Evidence from other parts of the Caribbean supports the hypothesis of continuous Holocene accumulation and recent mass mortality of Acropora spp. Prospects are poor for the rapid recovery of A. cervicornis, because its reproductive strategy emphasizes asexual fragmentation at the expense of dispersive sexual reproduction. A. palmata also relies on fragmentation, but this species has a higher rate of sexual recruitment than A. cervicornis If the Acropora spp. do not recover, macroalgae will continue to dominate Caribbean reefs, accompanied by increased abundances of brooding corals, particularly Agaricia spp. and Porites spp. The outbreak of white-band disease has been coincident with increased human activity, and the possibility of a causal connection should be further investigated.
In the current era of reduced coral populations, the effects of predation are likely to compromise the growing investment in restocking of imperiled coral populations and may be a strong, chronic deterrent of natural population recovery. A 2 yr surveillance study documented highly variable prevalence of predation by the fireworm Hermodice carunculata on both wild (0 to 51%) and restocked (0 to 53%) populations of the Caribbean staghorn coral Acropora cervicornis, but significantly higher prevalence overall in 2012 than 2011. In addition, individual predation scars (branch tips) were tagged to determine the costs of predation both in terms of healing time (i.e. to recover positive rates of branch growth) and in terms of likelihood of progressive diseaselike tissue loss on preyed branch tips. The risk of preyed branches showing progressive tissue loss at the subsequent survey was 10 times higher than for non-preyed branches. A survival analysis indicated an estimated mean time to healing for preyed branch tips of 110 ± 6 d (95% confidence). Finally, an experiment conducted in 2013 tested whether removing the dead skeleton from preyed branch tips could accelerate recovery. Indeed, this intervention shortened the mean time to formation of a new apical tip to 46 d (range: 22 to 92 d). Thus, fireworm predation imposes significant costs on both remnant wild and restocked staghorn colonies, but removing dead tips, rather than leaving them to bioerode, is a useful strategy to accelerate recovery from predation.
Since the 1980s, population densities of Acroporidae have dramatically declined in the Caribbean Sea. Quantitative censuses of Acroporidae provide information on the number of colonies (i.e. ramets), but not on the number of genetically distinct individuals (i.e. genets). In this context, the aim of our study was to provide an overview of the genetic status of Acropora populations in Guadeloupe by examining the genotypic richness of Acropora palmata and Acropora cervicornis. Using 14 microsatellite loci, we found extremely low genotypic richness for both species from Caye-À-Dupont reef (i.e. 0.125 for A. palmata and nearly zero for A. cervicornis). Because genetic diversity contributes to the ability of organisms to evolve and adapt to new environmental conditions, our results are alarming in the context of ongoing global warming as long periods of clonal growth without sexual recruitment may lead to the extinction of these populations.
Coral reefs have largely declined across multiple spatial scales due to a combination of local-scale anthropogenic impacts, and due to regional-global climate change. This has resulted in a significant loss of entire coral functional groups, including western Atlantic Staghorn coral (Acropora cervicornis) biotopes, and in a net decline of coral reef ecosystem resilience, ecological functions, services and benefits. Low-tech coral farming has become one of the most important tools to help restore depleted coral reefs across the Wider Caribbean Region. We tested a community-based, low-tech coral farming approach in Culebra Island, Puerto Rico, aimed at adapting to climate change-related impacts through a two-year project to propagate A. cervicornis under two contrasting fishing management conditions, in coastal areas experimenting significant land use changes. Extreme rainfall events and recurrent tropical storms and hurricanes had major site-and method-specific impacts on project outcome, particularly in areas adjacent to deforested lands and subjected to recurrent impacts from land-based source pollution (LBSP) and runoff. Overall, coral survival rate in “A frame” units improved from 73% during 2011-2012 to 81% during 2012-2013. Coral survival rate improved to 97% in horizontal line nurseries (HLN) incorporated during 2012-2013. Percent tissue cover ranged from 86% to 91% in “A frames”, but reached 98% in HLN. Mean coral skeletal extension was 27 cm/y in “A frames” and 40 cm/y in HLN. These growth rates were up to 545% to 857% faster than previous reports from coral farms from other parts of the Caribbean, and up to 438% faster than wild colonies. Branch production and branchiness index (no. harvestable branches > 6 cm) increased by several orders of magnitude in comparison to the original colonies at the beginning of the project. Coral mortality was associated to hurricane physical impacts and sediment-laden runoff impacts associated to extreme rainfall and deforestation of adjacent lands. This raises a challenging question regarding the impact of chronic high sea surface temperature (SST), in combination with recurrent high nutrient pulses, in fostering increased coral growth at the expense of coral physiological conditions which may compromise corals resistance to disturbance. Achieving successful local management of reefs and adjacent lands is vital to maintain the sustained net production in coral farms and of reef structure, and the provision of the important ecosystem services that they provide. These measures are vital for buying time for reefs while global action on climate change is implemented. Adaptive community-based strategies are critical to strengthen institutional management efforts. But government agencies need to transparently build local trust, empower local stakeholders, and foster co-management to be fully successful. Failing to achieve that could make community-based coral reef rehabilitation more challenging, and could potentially drive rapidly declining, transient coral reefs into the slippery slope to slime.
The 1983–1984 caribbean-wide mass mortality of the once ubiquitous long-spined sea urchin Diadema antillarum Philippi, 1845, is one of several factors considered responsible for coral reef change throughout the region. Unfortunately, there is a paucity of pre-mortality event density data for D. antillarum in the Florida Keys, making it difficult to determine pre-1983 population density levels. results from surveys conducted during 1970–1973 in the lower Florida Keys, in shallow (D. antillarum densities in qualitative transects at five reefs prior to the 1983–1984 die-off. In quantitative surveys at one reef, Middle sambo reef in 1972, up to 7.9 individuals m–2 were recorded using quadrats in high-relief spur and groove habitat. A second mortality event in the Florida Keys, beginning in April 1991, again depressed urchin densities that had begun to recover from the 1983–1984 mass mortality. by 1992, D. antillarum densities (–2) were two orders of magnitude lower than pre-die-off estimates (range of 0.07–0.57 m–2 from several spur and groove reefs in the lower Florida Keys) and remained so through 2009. The pre-mortality echinoid density estimates detailed in the Florida Keys provide a baseline to compare with their current population status and should help inform managers about realistic recovery or restoration targets for D. antillarum.
Coral reef restoration has gained recent popularity in response to the steady decline of corals and the recognition that coral reefs may not be able to recover naturally without human intervention. To synthesize collective knowledge about reef restoration focused particularly on the threatened genus Acropora in the Caribbean and western Atlantic, we conducted a literature review combined with personal communications with restoration practitioners and an online questionnaire to identify the most effective reef restoration methods and the major obstacles hindering restoration success. Most participants (90%) strongly believe that Acropora populations are severely degraded, continue to decline, and may not recover without human intervention. Low-cost methods such as coral gardening and fragment stabilization were ranked as the most effective restoration activities for this genus. High financial costs, the small footprint of restoration activities, and the potential damage to wild populations were identified as major concerns, while increased public awareness and education were ranked as the highest benefits of coral reef restoration. This study highlights the advantages and outlines the concerns associated with coral reef restoration and creates a unique synthesis of coral restoration activities as a complementary management tool to help guide “best-practices” for future restoration efforts throughout the region.
The decline and potential recovery of Caribbean reefs has been the subject of intense discussion and is of great interest to reef ecologists and managers. The recent return of Diadema antillarum sea urchins at some Caribbean locations and the concomitant changes in coral cover and recruitment. provide a new perspective on the reversibility of Caribbean coral reef decline. This study examined the influence of recovering populations of Diadema and the subsequent formation of dense urchin zones on the growth and density of newly settled juvenile scleractinian corals. In these urchin zones, where Diadema graze algae, we documented higher growth rates of juvenile corals, and higher densities of small juvenile recruits (likely to be important precursors to reef recovery). Coral survivorship was higher for juvenile corals living in urchin versus algal zones. Roughly 83% of the juvenile corals in urchin zones survived over the 2 yr period of the study, while similar to 69% survived in the algal zones. Corals in the urchin zones increased in major diameter by an average of 75 +/- 7% from 2001 to 2003 versus 24 +/- 4% for corals in the algal zones during the same time period. The relatively abrupt decrease in macroalgal cover and the signs of increasing coral cover along the north coast of Jamaica following the return of Diadema, reported here and by other authors, suggest that these reefs have undergone rapid phase shifts, rather than being constrained to alternate stable states. In the Caribbean, it appears that Diadema are effective at enhancing scleractinian coral recruitment and growth and thus could be used as an important manipulative tool for returning reefs to a coral dominated state, especially on reefs that are severely overfished.
The physiological reactions to sediment of four scleractinia and five alcyonacea from South Africa were observed in the laboratory. Species tested were Favia favus Forskal, Favites pentagona Esper, Platygyra daedalea Ellis & Solander, Gyrosmilia interrupta Ehrenberg, Lobophytum depressum Tixier-Durivault, Lobophytum venustum Tixier-Durivault, Sinularia dura (Pratt), Sinularia leptoclados (Ehrenberg) and Sarcophyton glaucum (Quoy & Gaimard). Natural sedimentation levels and light conditions were simulated. Photosynthetic carbon production and respiration were measured by respirometry. Loss of fixed carbon through mucus production was measured directly by filtration. The results were used to model daily energy budgets for these species. One set of models allowed for 50% PARs (photosynthetically active radiation at the surface), another set of models allowed for 25% PARs. The models showed severely diminished productivity and decreased respiration under sedimented conditions. Production/respiration (PR) ratios of all species were above 1 in the absence of sediment and dropped below unity when the corals were subjected to sedimentation. Although overall respiration dropped, its demand upon the also diminished amount of photosynthetically produced carbon rose dramatically. Without sediment, mucus output averaged 35% of daily respiration; this rose to 65% when sediment was applied. Sediment affects coral metabolism by decreasing photosynthetic production, increasing relative respiration and increasing carbon-loss through greater mucus output.
The 1983 mass mortality of the sea urchin Diadema antillarum greatly decreased graz- ing intensity on Caribbean reefs, contributing to widespread increases in algal abundance and exac- erbating decreases in coral cover. Urchin populations have been recovering in some areas, most notably the reefs of Jamaica's north coast. We manipulated the density of D. antillarum in the buttress zone of a previously unstudied Jamaican reef where the recovering urchins have a clumped distrib- ution. Some buttresses have a large number of urchins while others nearby have none. We trans- planted half of the urchins from high urchin density donor buttresses to low urchin density recipient buttresses. Transplantation significantly decreased the percent cover of macroalgae and increased the amount of bare space. These changes occurred despite a generally low retention of transferred urchins on recipient buttresses. Those urchins remaining on the recipient buttresses aggregated at rugose locations around which algae-free barrens appeared. Transplantation of urchins decreased their local density while maintaining overall density on the reef. The increase in algal consumption after transplantation implies that aggregated urchins compete for algae. Whereas aggregated D. antillarum tend to graze within the same area and have only a localized effect on algae, dispersed urchins compete less and eat more. Increased bare space could enhance recruitment of corals, further improving reef health. Our methods could potentially be used as an inexpensive reef restoration tool. Such restoration projects would be most effective if recipient sites with natural or artificially increased rugosity are used.
The 1983-84 Caribbean-wide mortality of the long-spined sea urchin Diadema antillarum
Philippi was followed by a 2nd mortality event during 1991 in the Florida Keys. Pre-mortality
sea urchin densities were up to 5 ind. m–2 and the large scale decline of D. antillarum is considered
to be 1 factor affecting community dynamics of Florida Keys reefs. During 1999-2000, we surveyed
125 sites using a stratified random sampling design in shallow-water coral reef and hard-bottom
habitats. Strip transects were sampled to assess density, habitat utilization and size structure patterns
among habitat types, regional sectors and between fished and protected areas. Nearly 17 yr after the
mass mortality, D. antillarum has not recovered to pre-1983 levels, with current densities no greater
than 0.05 ind. m–2, and small test sizes (1 to 2 cm) dominate. Other sea urchins such as Eucidaris
tribuloides (Lamarck) and Echinometra viridis Agassiz show density and habitat distribution patterns
similar to historical observations.
Sustainable Development Goal 14 of the United Nations aims to “conserve and sustainably use the oceans, seas and marine resources for sustainable development”. Achieving this goal will require rebuilding the marine life-support systems that deliver the many benefits that society receives from a healthy ocean. Here we document the recovery of marine populations, habitats and ecosystems following past conservation interventions. Recovery rates across studies suggest that substantial recovery of the abundance, structure and function of marine life could be achieved by 2050, if major pressures—including climate change—are mitigated. Rebuilding marine life represents a doable Grand Challenge for humanity, an ethical obligation and a smart economic objective to achieve a sustainable future.
Coral reef restoration is an increasingly important part of tropical marine conservation. Information about what motivates coral reef restoration as well as its success and cost is not well understood but needed to inform restoration decisions. We systematically review and synthesise data from mostly scientific studies published in peer‐reviewed and grey literature on the motivations for coral reef restoration, the variables measured, outcomes reported, the cost per hectare of the restoration project, the survival of restored corals, the duration of the project and its overall spatial extent depending on the restoration technique employed. The main motivation to restore coral reefs for the projects assessed was to further our ecological knowledge and improve restoration techniques, with coral growth, productivity and survival being the main variables measured. The median project cost was 400,000 US$ ha‐1 (2010 US$), ranging from 6,000 US$ ha‐1 for the nursery phase of coral gardening to 4,000,000 US$ ha‐1 for substrate addition to build an artificial reef. Restoration projects were mostly of short duration (1‐2 years) and over small spatial extents (0.01 ha or 108 m²). Median reported survival of restored corals was 60.9%. Future research to survey practitioners who do not publish their discoveries would complement this work. Our findings and database provide critical data to inform future research in coral reef restoration.
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Incorporating ecological processes into restoration planning is increasingly recognized as a fundamental component of successful restoration strategies. We outline a scientific framework to advance the emerging field of coral restoration. We advocate for harnessing ecological processes that drive community dynamics on coral reefs in a way that facilitates the establishment and growth of restored corals. Drawing on decades of coral reef ecology research and lessons learned from the restoration of other ecosystems, we posit that restoration practitioners can control factors such as the density, diversity, and identity of transplanted corals; site selection; and transplant design to restore positive feedback processes-or to disrupt negative feedback processes-in order to improve restoration success. Ultimately, we argue that coral restoration should explicitly incorporate key natural processes to exploit dynamic ecological forces and drive recovery of coral reef ecosystems.
Coastal communities in tropical environments are at increasing risk from both environmental degradation and climate change and require urgent local adaptation action. Evidences show coral reefs play a critical role in wave attenuation but relatively little direct connection has been drawn between these effects and impacts on shorelines. Reefs are rarely assessed for their coastal protection service and thus not managed for their infrastructure benefits, while widespread damage and degradation continues. This paper presents a systematic approach to assess the protective role of coral reefs and to examine solutions based on the reef's influence on wave propagation patterns. Portions of the shoreline of Grenville Bay, Grenada, have seen acute shoreline erosion and coastal flooding. This paper (i) analyzes the historical changes in the shoreline and the local marine, (ii) assess the role of coral reefs in shoreline positioning through a shoreline equilibrium model first applied to coral reef environments, and (iii) design and begin implementation of a reef-based solution to reduce erosion and flooding. Coastline changes in the bay over the past 6 decades are analyzed from bathymetry and benthic surveys, historical imagery, historical wave and sea level data and modeling of wave dynamics. The analysis shows that, at present, the healthy and well-developed coral reefs system in the southern bay keeps the shoreline in equilibrium and stable, whereas reef degradation in the northern bay is linked with severe coastal erosion. A comparison of wave energy modeling for past bathymetry indicates that degradation of the coral reefs better explains erosion than changes in climate and historical sea level rise. Using this knowledge on how reefs affect the hydrodynamics, a reef restoration solution is designed and studied to ameliorate the coastal erosion and flooding. A characteristic design provides a modular design that can meet specific engineering, ecological and implementation criteria. Four pilot units were implemented in 2015 and are currently being field-tested. This paper presents one of the few existing examples available to date of a reef restoration project designed and engineered to deliver risk reduction benefits. The case study shows how engineering and ecology can work together in community-based adaptation. Our findings are particularly important for Small Island States on the front lines of climate change, who have the most to gain from protecting and managing coral reefs as coastal infrastructure.
Coral reefs in the Caribbean Sea have progressively degraded in recent decades due to multiple stressors that include the mass mortality of a keystone invertebrate herbivore, Diadema antillarum (Philippi, 1845), in the 1980s. The population of D. antillarum in the Florida Keys has yet to recover, but recent advances in rearing captive-spawned D. antillarum have raised the possibility that D. antillarum can be produced in captivity and released into the wild as part of coral reef restoration efforts. However, organisms raised under artificial conditions could differ from their wild counterparts in ways that might reduce their fitness. Therefore, we conducted a series of experiments that compared the behavioral and morphological characteristics of hatchery-propagated and wild-collected D. antillarum. We demonstrate that hatchery-propagated D. antillarum raised in a non-rugose environment do not display the crevice shelter-seeking behavior of wild individuals. However, they did respond to the chemosensory stimulus of a potential predator, although they did not exhibit the escape behavior exhibited by wild individuals. Hatchery-propagated D. antillarum also exhibited lower spine density than wild individuals, likely the result of being maintained in conditions that did not induce spine breakage. However, this apparent habitat-induced morphological deficit was mitigated by maintaining them in rugose conditions. Our results suggest that competent hatchery-propagated D. antillarum can eventually be produced for coral reef restoration efforts, but they also underscore the need to further evaluate whether the behavioral deficiencies we identified can be effectively mitigated to ensure that ecologically competent individuals can be produced for such efforts. © 2018 Rosenstiel School of Marine & Atmospheric Science of the University of Miami.
Staghorn coral Acropora cervicornis is an important framework-building species that has declined severely throughout the Caribbean since the early 1980s. This species is now widely cultured in ocean-based nurseries to restore degraded populations. A variety of techniques have been adopted to grow A. cervicornis for restoration purposes, however the effect of each of these methods on nursery-reared corals is not well-understood. In particular, systematic evaluation of nursery-reared A. cervicornis between water column-suspended and benthic-attached culture methods is lacking. To better understand the effect of these techniques, a one-year A. cervicornis propagation experiment in the Florida Keys was conducted to compare growth, condition, and survivorship between common suspended (i.e. tree) and benthic-attached (i.e. block) grow-out methods. The effect of coral genotype on growth was also considered. Colonies were measured and monitored monthly from December 2014 until November 2015, when only three colonies had survived an extreme bleaching event. Colonies on trees grew up to three times faster than those on blocks and the location of colonies on trees did not affect growth. Genotype had a significant effect on colony growth, which was consistent across grow-out methods. Interestingly, colonies grown on blocks bleached sooner but survived longer than those on trees. These findings contribute to a growing understanding of A. cervicornis nursery culture, and could aid in the selection of culture methods and genotypes for coral nurseries throughout the wider Caribbean.
A guide to using S environments to perform statistical analyses providing both an introduction to the use of S and a course in modern statistical methods. The emphasis is on presenting practical problems and full analyses of real data sets.
Mass mortality of the sea urchin Diadema antillarum due to disease outbreaks in 1983 and 1991 decimated populations in the Florida Keys, and they have yet to recover. Here, we use a coupled advection-diffusion and fertilization-kinetics model to test the hypothesis that these populations are fertilization limited. We found that fertilization success was ≥ 96% prior to the first disease outbreak, decreased substantially following recurrent disease to 3%, and has since remained low. By investigating the combined effects of physical factors (population spatial extent and current velocity) and sea urchin behavior (aggregation) on density-dependent fertilization success, we show that fertilization success at a given density increases with increasing population spatial extent and decreasing current velocity, and is greater under simulated aggregation behavior of D. antillarum. However, at present population densities, the increase in fertilization success due to aggregation is < 1%, even under the most favorable physical conditions. These results indicate that populations are severely fertilization limited, and that Allee effects at low population density will continue to limit recovery. Our results can serve as a practical guide to managers in the development of coral reef restoration strategies, including the design of a D. antillarum restocking program to obtain reproductively viable populations.
Ecologists and evolutionary biologists are relying on an increasingly
sophisticated set of statistical tools to describe complex natural systems. One
such tool that has gained increasing traction in the life sciences is
structural equation modeling (SEM), a variant of path analysis that resolves
complex multivariate relationships among a suite of interrelated variables. SEM
has historically relied on covariances among variables, rather than the values
of the data points themselves. While this approach permits a wide variety of
model forms, it limits the incorporation of detailed specifications. Here, I
present a fully-documented, open-source R package piecewiseSEM that builds on
the base R syntax for all current generalized linear, least-square, and mixed
effects models. I also provide two worked examples: one involving a
hierarchical dataset with non-normally distributed variables, and a second
involving phylogenetically-independent contrasts. My goal is to provide a
user-friendly and tractable implementation of SEM that also reflects the
ecological and methodological processes generating data.
There has been ongoing flattening of Caribbean coral reefs with the loss of habitat having severe implications for these systems. Complexity and its structural components are important to fish species richness and community composition, but little is known about its role for other taxa or species-specific responses. This study reveals the importance of reef habitat complexity and structural components to different taxa of macrofauna, total species richness, and individual coral and fish species in the Caribbean. Species presence and richness of different taxa were visually quantified in one hundred 25-m(2) plots in three marine reserves in the Caribbean. Sampling was evenly distributed across five levels of visually estimated reef complexity, with five structural components also recorded: the number of corals, number of large corals, slope angle, maximum sponge and maximum octocoral height. Taking advantage of natural heterogeneity in structural complexity within a particular coral reef habitat (Orbicella reefs) and discrete environmental envelope, thus minimizing other sources of variability, the relative importance of reef complexity and structural components was quantified for different taxa and individual fish and coral species on Caribbean coral reefs using boosted regression trees (BRTs). Boosted regression tree models performed very well when explaining variability in total (82·3%), coral (80·6%) and fish species richness (77·3%), for which the greatest declines in richness occurred below intermediate reef complexity levels. Complexity accounted for very little of the variability in octocorals, sponges, arthropods, annelids or anemones. BRTs revealed species-specific variability and importance for reef complexity and structural components. Coral and fish species occupancy generally declined at low complexity levels, with the exception of two coral species (Pseudodiploria strigosa and Porites divaricata) and four fish species (Halichoeres bivittatus, H. maculipinna, Malacoctenus triangulatus and Stegastes partitus) more common at lower reef complexity levels. A significant interaction between country and reef complexity revealed a non-additive decline in species richness in areas of low complexity and the reserve in Puerto Rico. Flattening of Caribbean coral reefs will result in substantial species losses, with few winners. Individual structural components have considerable value to different species, and their loss may have profound impacts on population responses of coral and fish due to identity effects of key species, which underpin population richness and resilience and may affect essential ecosystem processes and services.
This tutorial demostrates the use of basic ordination methods in R package vegan. The tutorial assumes basic familiarity both with R and with ordination methods. Package vegan supports all basic ordination method, including non-metric multidimensional scaling. The constrained ordination methods include constrained analysis of proximities, redundancy analysis and constrained correspondence analysis. Package vegan also has support functions for environ-mental fitting and ordination graphics. In addition to ordination methods, vegan contains several methods for analysis species di-versity, but these methods are not discussed in this tutorial.
We surveyed the benthic community structure and population density of the long-spined sea urchin Diadema antillarum on the shallow fore-reefs of the Gandoca-Manzanillo Wildlife Refuge, Caribbean Costa Rica, in September and October 2004. In zones with high densities of D. antillarum (> 0.6 ind. m(-2)), the cover of non-calcareous macroalgae, known coral competitors, was low and that of live coral was high, whereas the opposite occurred in zones with low densities of D. antillarum (< 0.1 ind. m(-2)). D. antillarum density was not related to the coverage of calcareous macroalgae, which are not viewed as coral competitors. Mean density of D. antillarum was 0.2 ind. m(-2) and the total area covered by live coral was 14 %. D, antillarum density and area covered by live coral were 2 and 7 times larger, respectively, than those reported 4 yr earlier for the study site. Within the same period, the proportion contributed by non-calcareous macroalgae to total algal cover declined from similar to 79 to 48%. Results indicate that various families of scleractinian corals in the Caribbean coast of Costa Rica have increased in abundance, that non-calcareous macroalgae have declined, and that recovering D. antillarum densities are correlated with these observations.
Acropora hyacinthus, Pocillopora damicornis and Pavona frondifera displayed distinct differences which could be related to their respective life-history strategies. A. hyacinthus showed tendencies towards an r-mode, with rapid lienar growth but also high mortality rates. Response to transplantation was poor. Pocillopora damicornis had intermediate linear growth rates and relatively high mortality. Transplants fared poorly in the initial part of the experiment, though they showed successful adaptation after a year. Mortality rates of both A. hyacinthus and P. damicornis were increased by high temperatures during certain times of the year. Pavona frondifera had the highest linear growth rates and no mortality, tending towards a K-mode of life history strategy. It showed the best response to transplantation. This species is thus a suitable candidate for large-scale reef restoration in the Philippines. -from Authors