An emerging coral disease outbreak decimated Caribbean coral populations and reshaped reef functionality

Diseases are major drivers of the deterioration of coral reefs, linked to major declines in coral abundance, reef functionality, and reef-related ecosystems services1-3. An outbreak of a new disease is currently rampaging through the populations of the remaining reef-building corals across the Caribbean region. The outbreak was first reported in Florida in 2014 and reached the northern Mesoamerican reef by summer 2018, where it spread across the ~ 450-km reef system only in a few months4. Rapid infection was generalized across all sites and mortality rates ranged from 94% to < 10% among the 21 afflicted coral species. This single event further modified the coral communities across the region by increasing the relative dominance of weedy corals and reducing reef functionality, both in terms of functional diversity and calcium carbonate production. This emergent disease is likely to become the most lethal disturbance ever recorded in the Caribbean, and it will likely result in the onset of a new functional regime where key reef-building and complex branching acroporids (a genus apparently unaffected) will once again become conspicuous structural features in reef systems with yet even lower levels of physical functionality.

Recruitment hotspots and bottlenecks mediate the distribution of corals on a Caribbean reef

Recruitment hotspots are locations where organisms are added to populations at high rates. On tropical reefs where coral abundance has declined, recruitment hotspots are important because they have the potential to promote population recovery. Around St. John, US Virgin Islands, coral recruitment at five sites revealed a hotspot that has persistent for 14 years. Recruitment created a hotspot in density of juvenile corals that was 600 m southeast of the recruitment hotspot. Neither hotspot led to increased coral cover, thus revealing the stringency of the demographic bottleneck impeding progression of recruits to adult sizes and preventing population growth. Recruitment hotspots in low-density coral populations are valuable targets for conservation and sources of corals for restoration.

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 multifaceted approach to reduce the impacts of chronic reef stressors on wild and outplanted corals alike.

Sexual production of corals for reef restoration in the Anthropocene

Coral-reef ecosystems are experiencing frequent and severe disturbance events that are reducing global coral abundance and potentially overwhelming the natural capacity for reefs to recover. While mitigation strategies for climate warming and other anthropogenic disturbances are implemented, coral restoration programmes are being established worldwide as an additional conservation measure to minimise coral loss and enhance coral recovery. Current restoration efforts predominantly rely on asexually produced coral fragments—a process with inherent practical constraints on the genetic diversity conserved and the spatial scale achieved. Because the resilience of coral communities has hitherto relied on regular renewal with natural recruits, the scaling-up of restoration programmes would benefit from greater use of sexually produced corals, which is an approach that is gaining momentum. Here we review the present state of knowledge of scleractinian coral sexual reproduction in the context of reef restoration, with a focus on broadcast-spawning corals. We identify key knowledge gaps and bottlenecks that currently constrain the sexual production of corals and consider the feasibility of using sexually produced corals for scaling-up restoration to the reef- and reef-system scales.

Urgent need for coral demography in a world where corals are disappearing

Coral reefs have long attracted attention because of their biological and economic importance, but this interest now has turned to examining the possibility of functional extirpation. Widespread declines in coral abundances have fueled the shift in motivation for studying reefs and catalyzed the proliferation of monitoring to record the changes underway. Despite appreciation of monitoring as a scientific endeavor, its primary use has continued to be the quantification of cover of coral, macroalgae, and a few other space holders. The limitations of coral cover in evaluating the consequences of changing coral abundance were highlighted decades ago. Yet neglect of the tools most appropriate for this task (demographic approaches) and continuing emphasis on a tool (coral cover) that is not ideal, indicates that these limitations are not widely appreciated. Reef monitoring therefore continues to underperform with respect to its potential, thus depriving scientists of the approaches necessary to project the fate of coral reefs and test hypotheses focused on the proximal causes of declining coral cover. We make the case that the coral reef crisis creates a need for coral demography that is more acute now than 4 decades ago. Modern demographic approaches are well suited to meet this need, but to realize their potential, consideration will need to be given to the possibility of expanding ecological monitoring of coral reefs to provide the data necessary for demographic analyses of their foundation taxon, the Scleractinia.

Cross-Shelf Variation Among Juvenile and Adult Coral Assemblages on Australia’s Great Barrier Reef

Coral reefs are under increasing pressure from a variety of stressors, highlighting the need for information about the status of coral reef communities including the distribution, abundance and composition of juvenile and adult coral assemblages. This information is currently limited for the Great Barrier Reef (GBR) and is necessary for understanding the impacts of disturbances and the system’s potential for recovery. This study reports juvenile and adult hard coral abundance and composition from 122 reefs on the GBR during a period of limited acute disturbance. The data represent baseline observations for juvenile hard coral assemblages spanning the longitudinal cross-shelf gradient of the GBR and 12 degrees of latitude and augment reported distribution of adult coral assemblages over the same scale with inclusion of additional reefs. Juvenile and adult coral assemblages reflected broad differences imposed by the gradient of environmental conditions across the GBR. The mean density of juvenile hard corals was lower in the inshore reefs (5.51 m2) than at either the mid-shelf (11.8 m2) or outer shelf reefs (11.2 m2). The composition of juvenile and adult coral assemblages covaried overall, although there were different relationships between these two life stages across the continental shelf and among community types. Dissimilarity between juvenile and adult coral assemblages was greater on inshore and outer shelf reefs than on reefs in the mid-shelf, although, there were differences in community types both within these shelf positions and those that spanned mid- and outer shelf reefs. Dissimilarity was greatest for Inshore branching Acropora and high for Southern Acropora communities, although very high coral cover and very low juvenile densities at these reefs precluded interpretation beyond the clear competitive dominance of Acropora on those reefs. Dissimilarity was also high between juvenile and adult coral assemblages of Turbid inshore communities suggesting water quality pressures, along with synergistic effects of other stressors, pose ongoing selective pressures beyond the juvenile stage. Conversely, relatively low dissimilarity between juvenile and adult coral assemblages on mid-shelf and lower latitude outer shelf reefs suggests pressures beyond those influencing settlement and early post-settlement survival were having less influence on the composition of adult coral assemblages.

HUBUNGAN KONDISI TERUMBU KARANG DENGAN KELIMPAHAN IKAN KARANG TARGET DI PERAIRAN PULAU TINABO BESAR, TAMAN NASIONAL TAKA BONERATE, SULAWESI SELATAN

This research aims to understand the condition of coral reef (life coral), the abundance of reef target fishes, and the corellation between those two variables. This research has been conducted in Tinabo Besar Island with 6 sampling stations in 5-6 meter depth. Data collected are substrate cover precentage (life form), and the number of reef target fish appeared from 7 specified families (Serranidae, Lutjanidae, Haemulidae, Lethrinidae, Scaridae, Siganidae, and Acanthuridae) using Underwater Photo Transect (UPT) and Underwater Visual Census (UVC). Substrate cover analyzed using CPCe software with life coral, dead coral, algae, abiotic, and other biota cover output. Mortality Index (MI) obtained from the ratio of life coral and dead coral. The result shows that percentage of life coral coverlie between 11.87% to 38.80%, with dominance of Coral Masive (CM). It’s mean that the coral reef condition is in poor to moderate category. Coral death ratio is low with MI between 0.15 to 0.30. Reef target fish total abundance is 493 individual/2100m2 from 31 species, with dominance from Lutjanidae family (173 individual). The result shows positive and strong enough correlation between coral reef coverage and reef target fish abundance (r=0.65) with Determinantion Coefficient at 42.55%. Linear regression is y=-12.929+3.7562x, where in every addition of coral reef cover percentage, resulted in addition of 4 fishes.Keyword: life coral, abundance, reef target fish, correlation, Tinabo Besar Island

KELIMPAHAN DAN KERAGAMAN JENIS IKAN FAMILI CHAETODONTIDAE BERDASARKAN KONDISI TUTUPAN KARANG HIDUP DI KEPULAUAN SPERMONDE SULAWESI SELATAN

The family Chaetodontidae known as butterfly fishes (kepe-kepe) is a species that associated with coral by consumes coral polyp as its feed. This study aimed to determine the abundance and fish diversity of Chaetodontidae and to look the relationship of fish Chaetodontidae abundance with live coral coverage at Spermonde Island. To determines the abundance and fish diversity of Chaetodontidae by using direct census, while to determine the condition of coral reel used line intercept transect (LIT) method. This study was conducted for 6 (six) station at Spermonde Island by collecting data on depth 4 – 6 m with 3 replicate in each station. Result of study found 5 genera and consist of 16 species fishes from family Chaetodontidae. The overall of Chaetodontidae found is 70 Ind/250 m2 with the largest abundance in Kapoposang island (46 Ind/250 m2) and the smallest is Karanrang island (1 Ind/250 m2). Percentage of live coral coverage on research station at Spermonde Island at “good” to “bad” categories highest coral coverage at Badi island (72.6%) and the lowest is Balanglompo island (5%). Fish diversity of Chaetodontidae is high at station that dominated by Acropora coral. Abundance and fish diversity of Chaetodontidae are no relationship significantly on the percentage of live coral coverage of research station at Spermonde Island.Keyword : Chaetodontidae, coral reef, Spermonde.

Are coral reefs victims of their own past success?

As one of the most prolific and widespread reef builders, the staghorn coral Acropora holds a disproportionately large role in how coral reefs will respond to accelerating anthropogenic change. We show that although Acropora has a diverse history extended over the past 50 million years, it was not a dominant reef builder until the onset of high-amplitude glacioeustatic sea-level fluctuations 1.8 million years ago. High growth rates and propagation by fragmentation have favored staghorn corals since this time. In contrast, staghorn corals are among the most vulnerable corals to anthropogenic stressors, with marked global loss of abundance worldwide. The continued decline in staghorn coral abundance and the mounting challenges from both local stress and climate change will limit the coral reefs’ ability to provide ecosystem services.

Decadal comparison of a diminishing coral community: a study using demographics to advance inferences of community status

The most common coral monitoring methods estimate coral abundance as percent cover, either viain situobservations or derived from images. In recent years, growing interest and effort has focused on colony-based (demographic) data to assess the status of coral populations and communities. In this study, we relied on two separate data sets (photo-derived percent cover estimates, 2002–12, and opportunisticin situdemographic sampling, 2004 and 2012) to more fully infer decadal changes in coral communities at a small, uninhabited Caribbean island. Photo-derived percent cover documented drastic declines in coral abundance including disproportionate declines inOrbicellaspp. While overallin situestimates of total coral density were not different between years, densities of several rarer taxa were.Meandrina meandritesandStephanocoenia interseptaincreased whileLeptoseris cucullatadecreased significantly, changes that were not discernable from the photo-derived cover estimates. Demographic data also showed significant shifts to larger colony sizes (both increased mean colony sizes and increased negative skewness of size frequency distributions, but similar maximum colony sizes) for most taxa likely indicating reduced recruitment.Orbicellaspp. differed from this general pattern, significantly shifting to smaller colony sizes due to partial mortality. Both approaches detected significant decadal changes in coral community structure at Navassa, though the demographic sampling provided better resolution of more subtle, taxon-specific changes.