Severe 2010 Cold-Water Event Caused Unprecedented Mortality to Corals of the Florida Reef Tract and Reversed Previous Survivorship Patterns

Background Coral reefs are facing increasing pressure from natural and anthropogenic stressors that have already caused significant worldwide declines. In January 2010, coral reefs of Florida, United States, were impacted by an extreme cold-water anomaly that exposed corals to temperatures well below their reported thresholds (16°C), causing rapid coral mortality unprecedented in spatial extent and severity. Methodology/Principal Findings Reef surveys were conducted from Martin County to the Lower Florida Keys within weeks of the anomaly. The impacts recorded were catastrophic and exceeded those of any previous disturbances in the region. Coral mortality patterns were directly correlated to in-situ and satellite-derived cold-temperature metrics. These impacts rival, in spatial extent and intensity, the impacts of the well-publicized warm-water bleaching events around the globe. The mean percent coral mortality recorded for all species and subregions was 11.5% in the 2010 winter, compared to 0.5% recorded in the previous five summers, including years like 2005 where warm-water bleaching was prevalent. Highest mean mortality (15%–39%) was documented for inshore habitats where temperatures were \u3c11°C for prolonged periods. Increases in mortality from previous years were significant for 21 of 25 coral species, and were 1–2 orders of magnitude higher for most species. Conclusions/Significance The cold-water anomaly of January 2010 caused the worst coral mortality on record for the Florida Reef Tract, highlighting the potential catastrophic impacts that unusual but extreme climatic events can have on the persistence of coral reefs. Moreover, habitats and species most severely affected were those found in high-coral cover, inshore, shallow reef habitats previously considered the “oases” of the region, having escaped declining patterns observed for more offshore habitats. Thus, the 2010 cold-water anomaly not only caused widespread coral mortality but also reversed prior resistance and resilience patterns that will take decades to recover

Ecological solutions to reef degradation: optimizing coral reef restoration in the Caribbean and Western Atlantic

Reef restoration activities have proliferated in response to the need to mitigate coral declines and recover lost reef structure, function, and ecosystem services. Here, we describe the recent shift from costly and complex engineering solutions to recover degraded reef structure to more economical and efficient ecological approaches that focus on recovering the living components of reef communities. We review the adoption and expansion of the coral gardening framework in the Caribbean and Western Atlantic where practitioners now grow and outplant 10,000’s of corals onto degraded reefs each year. We detail the steps for establishing a gardening program as well as long-term goals and direct and indirect benefits of this approach in our region. With a strong scientific basis, coral gardening activities now contribute significantly to reef and species recovery, provide important scientific, education, and outreach opportunities, and offer alternate livelihoods to local stakeholders. While challenges still remain, the transition from engineering to ecological solutions for reef degradation has opened the field of coral reef restoration to a wider audience poised to contribute to reef conservation and recovery in regions where coral losses and recruitment bottlenecks hinder natural recovery

The Role of Mucus in the Ultraviolet Radiation Protection of \u3cem\u3ePorites astreoides\u3c/em\u3e

High intensities of ultraviolet radiation (UVR) have been shown to detrimentally effect the growth, reproduction, and photosynthetic physiology of corals inhabiting tropical marine waters. One protective mechanism utilized by marine organisms, including corals, is the production of mycosporine-like amino acids (MAAs) that absorb biologically harmful wavelengths of UVR in the range from 309 to 360 nm. Normally present within animal tissues, MAAs have also been extracted from mucus present on colony surfaces. Many functions, including protection from sedimentation, salinity fluctuations, and temperature changes, have been attributed to coral mucus. The presence of MAAs within mucus suggests an additional function: protection from the biologically damaging effects of UVR. Therefore, the goal of this study was to evaluate the UVR protective capabilities of coral mucus and its constituent MAAs in situ by addressing three main questions. First, what are the UVR absorption capabilities of coral mucus? Second, is mucus production affected by exposure to UVR? And finally, do MAA concentrations within mucus vary with changes in UVR exposure? Colonies of Porites astreoides located at Rainbow Gardens (23.47.783N, 76.08.787W) and North Norman\u27s (23.47.373N, 76.08.267W) patch reefs adjacent to Lee Stocking Island, Bahamas were either exposed to, or protected from, ambient UVR for 45 days. Mucus and tissue samples were collected at the beginning and end of the experiment and mucus production was measured by mucus weight while absorption of UVR by mucus and tissue samples was analyzed using spectrophotometry. Neither mucus production nor MAA concentrations were affected by UVR exposure at ambient levels. However, coral mucus and associated MAAs absorbed 1.11% of the total UVR impinging on coral surfaces with the highest absorbance in the UV-B (280-320 nm) portion of the spectrum. Surprisingly, the mean percent absorbance of MAAs extracted from mucus was not significantly different from that of mucus and MAAs combined. These results indicate that any UVR protection provided by coral mucus is furnished primarily by MAAs rather than inherent properties of the mucus. Finally, mucus MAA concentrations were not dependent on tissue concentrations. In sum, coral mucus and associated MAAs do provide small amounts of UVR protection, but it is unlikely that mucus and its constituent compounds have been selected as a primary mechanism to prevent UVR damage

Ecological solutions to reef degradation: optimizing coral reef restoration in the Caribbean and Western Atlantic

ABSTRACT Reef restoration activities have proliferated in response to the need to mitigate coral declines and recover lost reef structure, function, and ecosystem services. Here, we describe the recent shift from costly and complex engineering solutions to recover degraded reef structure to more economical and efficient ecological approaches that focus on recovering the living components of reef communities. We review the adoption and expansion of the coral gardening framework in the Caribbean and Western Atlantic where practitioners now grow and outplant 10,000's of corals onto degraded reefs each year. We detail the steps for establishing a gardening program as well as long-term goals and direct and indirect benefits of this approach in our region. With a strong scientific basis, coral gardening activities now contribute significantly to reef and species recovery, provide important scientific, education, and outreach opportunities, and offer alternate livelihoods to local stakeholders. While challenges still remain, the transition from engineering to ecological solutions for reef degradation has opened the field of coral reef restoration to a wider audience poised to contribute to reef conservation and recovery in regions where coral losses and recruitment bottlenecks hinder natural recovery

Occupation Dynamics and Impacts of Damselfish Territoriality on Recovering Populations of the Threatened Staghorn Coral, <i>Acropora cervicornis</i>

<div><p>Large-scale coral reef restoration is needed to help recover structure and function of degraded coral reef ecosystems and mitigate continued coral declines. <i>In situ</i> coral propagation and reef restoration efforts have scaled up significantly in past decades, particularly for the threatened Caribbean staghorn coral, <i>Acropora cervicornis</i>, but little is known about the role that native competitors and predators, such as farming damselfishes, have on the success of restoration. Steep declines in <i>A</i>. <i>cervicornis</i> abundance may have concentrated the negative impacts of damselfish algal farming on a much lower number of coral prey/colonies, thus creating a significant threat to the persistence and recovery of depleted coral populations. This is the first study to document the prevalence of resident damselfishes and negative effects of algal lawns on <i>A</i>. <i>cervicornis</i> along the Florida Reef Tract (FRT). Impacts of damselfish lawns on <i>A</i>. <i>cervicornis</i> colonies were more prevalent (21.6% of colonies) than those of other sources of mortality (i.e., disease (1.6%), algal/sponge overgrowth (5.6%), and corallivore predation (7.9%)), and damselfish activities caused the highest levels of tissue mortality (34.6%) among all coral stressors evaluated. The probability of damselfish occupation increased as coral colony size and complexity increased and coral growth rates were significantly lower in colonies with damselfish lawns (15.4 vs. 29.6 cm per year). Reduced growth and mortality of existing <i>A</i>. <i>cervicornis</i> populations may have a significant effect on population dynamics by potentially reducing important genetic diversity and the reproductive potential of depleted populations. On a positive note, however, the presence of resident damselfishes decreased predation by other corallivores, such as <i>Coralliophila</i> and <i>Hermodice</i>, and may offset some negative impacts caused by algal farming. While most negative impacts of damselfishes identified in this study affected large individual colonies and <50% of the <i>A</i>. <i>cervicornis</i> population along the FRT, the remaining wild staghorn population, along with the rapidly increasing restored populations, continue to fulfill important functional roles on coral reefs by providing essential habitat and refuge to other reef organisms. Although the effects of damselfish predation are, and will continue to be, pervasive, successful restoration efforts and strategic coral transplantation designs may help overcome damselfish damage by rapidly increasing <i>A</i>. <i>cervicornis</i> cover and abundance while also providing important information to educate future conservation and management decisions.</p></div

Prevalence of sources of coral mortality (gray bars) and severity of impacts expressed as the mean percentage of tissue mortality on <i>A</i>. <i>cervicornis</i> colonies (black bars ± SE).

<p>Letters reference statistical difference in the mean percentage of tissue mortality of each coral colony affected by mortality between sources (one-way ANOVA; <i>p</i><0.001).</p

Location of sites along the Florida Reef Tract surveyed to investigate damselfish occupational dynamics and impacts.

<p>Open circles indicate sites where only wild staghorn colonies were observed. Black circles indicate sites where nursery-grown colonies were outplanted as part of restoration activities.</p

Colony of <i>Acropora cervicornis</i> with examples of (a) a damselfish algal lawn (solid circle) and chimneys formed by damselfish bites (dashed circle), and (b) a resident farming damselfish, <i>Stegastes planifrons</i>.

<p>Chimneys are formed as the coral attempts to recover tissue damaged due to repeated biting by damselfishes.</p

Optimizing the productivity of a coral nursery focused on staghorn coral Acropora cervicornis

The rapid decline of the staghorn coral Acropora cervicornis throughout the Caribbean prompted the development of coral gardening as a management strategy to restore wild stocks. Given that coral gardening relies on propagating corals collected from wild donor colonies, it is imperative to optimize growth within a nursery to reduce dependence on wild collections. This study determined the maximum amount of coral that may be clipped from a colony during propagation without causing mortality or decreased growth. We applied 3 experimental treatments to 12 nursery-reared staghorn corals, in which 25, 50, or 75% of the colony\u27s total biomass was removed and fragmented to create additional, smaller fragments. Four additional colonies served as unfragmented controls. Treatment had no effect on colony productivity, defined as the ratio of new tissue growth to initial colony size, over 87 d. Similarly, treatment had no effect on the rate at which colonies developed new branches. Results indicate that 75% of the biomass of staghorn colonies may be removed without affecting their growth. We anticipate that our observations will have practical applications for maximizing propagation of staghorn coral within nurseries throughout the wider Caribbean while minimizing the impact of this management measure on remnant wild populations

The impacts of competitive interactions on coral colonies after transplantation: A multispecies experiment from the Florida Keys, US

Reef restoration programs in Florida, US, focused initially on Acropora, but there is now a need to include other species that have also experienced declines. An outplanting experiment using Acropora cervicornis, Montastraea cavernosa, and Orbicella faveolata was conducted to compare performance among species and evaluate the impacts of contact interactions with macroalgae and the zoanthid Palythoa caribaeorum. Montastraea cavernosa and O. faveolata showed high survivorship (78% and 92%, respectively) over 18 mo. However, surviving colonies had limited growth and lost tissue due to factors like predation and disease. In contrast, A. cervicornis showed exponential growth. Colonies in contact with macroalgae showed the lowest survivorship. Removing macroalgae provided no long-term benefits in growth and a slight improvement in colony survivorship. Acropora cervicornis in contact with Palythoa grew 45% less than controls. Our study showed that: (1) coral taxa with massive morphologies (40–130 cm2) can be transplanted with low colony mortality but that their slow growth is not enough to balance partial tissue mortality caused by multiple chronic stressors; (2) removal of macroalgae at the time of outplanting improves colony survivorship; (3) periodic removal of macroalgae does not enhance growth; and (4) contact with Palythoa should be avoided. The impacts of contact competition were variable among species with different colony morphologies, with A. cervicornis showing the highest susceptibility to competition from algae and Palythoa. While restoration can rapidly increase coral abundance, long-term success will require a multi-faceted approach to reduce the impacts of chronic reef stressors on wild and outplanted corals alike