Coral reefs

In the last three decades, Caribbean coral cover values have been declining from 50% to 10% cover Caribbean wide. Several studies have researched this decreasing trend and assessed coral reefs throughout the Caribbean. These assessments often identify the coral reef of Bonaire as one of the most pristine reefs and describe the leeward coast of Bonaire as one of the healthier reefs of the Caribbean. However, the outcomes of these studies are based on pooled data, collected from multiple depths and locations and are presented as being valid for an entire reef while they have often been collected on a very small number of locations on each island. In a study on the ecosystem services of the reefs of Bonaire, Meesters et al. (2014) suggested that coral reefs show large variation in ecological quality on a small scale. This report investigates this small-scale variation in coral reef quality on the leeward coast of Bonaire. On the leeward side, we sampled the coral reef every 500 meters resulting in a total of 115 sampling sites. On each location, the reef was sampled at two different depths (~5 and ~10 meters) following the zonation pattern from Bak (1977). The reef quality is assessed with the Reefbudget methodology described in Perry et al. (2012). Carbonate production, bioerosion, and net production is calculated in kg CaCO3 m-2 year-1 for each site and depth. The net carbonate production reveals the quality of a reef. A positive value indicates the reef is growing while a negative value means a reef or site is flattening. Cluster analysis and TukeyHSD tests are used to analyse the spatial distribution of coral communities and to test if areas show a significant difference in coral reef quality. The shallow reef (depth ~5 meters) in front of Kralendijk shows clear signs of degradation. The area has a significant lower coral cover (3%, p=0.05) and a mean net carbonate production of -0.40 kg CaCO3 m-2 year-1. We found the marine reserve to have the highest coral cover and net carbonate production. The shallow reef of the marine reserve net produces 3.64 kg CaCO3 m-2 year-1, and the fringing deeper reef (depth ~10m) 4.04 kg CaCO3 m-2 year-1. A previous study found a net production of 3.63 kg CaCO3 m-2 year-1 for 5m depth zone. For the 10m depth, net carbonate production was 9.53 kg CaCO3 m-2 year-1. Both values were measured at the “no dive reserve” of Bonaire in Perry et al. (2012). This study finds a lower production for the 10 meters zone, but comparable values for the shallow reef at 5 meters depth. However, the values of the Marine Reserve in this study are the highest of the leeward side of Bonaire. The reef shows a large variation in reef quality along the coastline Net carbonate production ranged from a minimum of -8.70 to a maximum of 50.85 kg CaCO3 m-2 year-1 for one transect. This range is much larger than the range found by Perry et al. (2013). Perry et al. (2013) found a minimum net carbonate production of -2.3 kg CaCO3 m-2 year-1 and a maximum of 16.68 kg CaCO3 m-2 year-1. Comparing the calculated net carbonate production values in this study with data from the Caribbean region, we found that the variation between sites on the leeward side of Bonaire shows similarity with the variation throughout the area. Net production of reefs on Belize, Jamaica, and St. Croix show values of 1.42, 1.2-1.8, and 0.9 kg CaCO3 m-2 year-1 respectively. These values are similar to the 5 meters reef at Klein Bonaire, the South, and the North of Bonaire with 1.09, 0.49, and 0.18 kg CaCO3 m-2 year-1 production respectively. This study reveals a difference in coral community composition between the North and the South of Bonaire. The 10 meter reef of North Bonaire is merely Merulinidae spp where the South of Bonaire is more diverse with a larger cover of Agariciidae spp. Overall turf cover is high across the entire coastline with for the 10 meter depth reef a mean of 36.4% (± 1.8) cover. The 10 meter reef in front of the city shows a higher mean turf algae cover of 50% cover. This study shows that the reef in front of the Kralendijk is in a poor state and is, with a net negative carbonate production, flattening in topographic complexity. The Marine Reserve shows the best net production values in both the 10 meters depth reef as the 5 meters depth reef. The variation between sites along the leeward side is large. This large variation proofs that it is not legitimate to assess an entire coastline based on a limited number of sites. While parts of Bonaire Marine Reserve can indeed be viewed as belonging to the most pristine in the Caribbean, other areas, e.g. in front of the city, show similarities with known

Saba Bank is a large and completely submerged carbonate platform in the northeastern Caribbean Sea located approximately 4 km southwest of Saba Island, Netherlands Antilles. Zonation patterns of reef-like bathymetric features, together with observations of significant shelf edge coral reef development, suggest that Saba Bank is an actively growing coral reef atoll. Little quantitative data exists to evaluate the composition and distribution of marine benthic communities or fish assemblages of Saba Bank. In the present study, habitat surveys were conducted to investigate the abiotic characteristics, benthic community composition, and fish assemblage structure of habitats from an eastern portion of Saba Bank known as Overall Bank. A random stratified sampling design was developed that utilized remote sensing data for bathymetry and ocean color superimposed on reef zones. Five sampling strata, which putatively delineated five distinct marine habitat types, were identified along a shelf edge-to-lagoon gradient. Survey results indicate that the proposed strata correspond to distinct marine habitat types in terms of substrate composition, benthic cover, and dominant macro algae. Significant coral cover was restricted to the outer reef edge in the fore reef habitat (11.5 %) and outer reef flat (2.4 %), declining to near absence in the lagoon habitats towards the bank center. Macro algae dominated benthic cover in all habitats (32.5 – 48.1 % cover) with the composition of dominant algal genera differing among habitats. Gorgonians reached their highest density and greatest average colony height in the fore reef zone. Gorgonian colony height was also pronounced in softbottom habitats of the lagoon. Fish assemblage structure showed patterns that were concurrent with observed habitat zonation. Highest fish densities were observed in the outer reef flat, fore reef, and inner reef flat zones. Fish abundance and diversity was low in the lagoon zone and lowest over softbottom habitats within the lagoon. The greatest diversity of fishes (average number of species per survey, cumulative number of species) occurred in the fore reef zone and outer reef flat zone. Fish biomass followed the same pattern of distribution, with the greatest weight occurring in the outermost zones and least in the lagoon. Queen conch were most frequently encountered in the softbottom lagoon zone and estimates of average conch density were between 42 and 60 individuals per hectare. Abundance of spiny lobster was not adequately surveyed by the methods employed in this study and recommendations are made for improved field assessment of lobster stocks. Collectively, the results of this study indicate that the benthic communities of Saba Bank follow predictable patterns of distribution, diversity, and abundance across a gradient from shelf edge to lagoon. Recommendations for future research are given. 

Raw photo material of the 2015 reef survey using the GCRMN method.

The 20 survey sites lie within the St. Eustatius National Marine Park, which surrounds the island from the high water mark to a depth of 30 meters.  To maximize comparability across the region, GCRMN data was collected solely from forereef habitats at depths ranging from 8 – 15 meters. Sites included the industrialized harbor area along with sites with perceived lower anthropogenic influence on the north and south ends of the island. For each site 5 transects were surveyed. Photographs were taken along the 5 transect lines set for counting fish, capturing 15 images per transect line. See this report for details.

Please contact the DCBD administratorfor access to the raw digital photographs.

Coral reefs provide some of the most valuable ecosystem services for the islands. They are a driver of tourism, they protect against storms, and support local fisheries. To monitor this resource the regionally agreed Global Coral Reef Monitoring Network (GCRMN) scientific methods and guidelines for the Caribbean, provide a basic framework to contribute inter-comparable data that support a regional understanding of status and trends of Caribbean coral reefs, providing a systematic snapshot of ecosystem health and insight into temporal trends in reef condition. The data contribute to our understanding of processes shaping coral reefs, and to actionable advice to policy makers, stakeholders, and communities.
The Ministry of Economic Affairs, as part of its efforts for the International Coral Reef Initiative (ICRI), together with GCRMN and the SPAW protocol convened a regional workshop in Curacao August 6th – 8th, 2014 during which coral reef experts from the region came together and discussed how to better coordinate ongoing Caribbean coral reef monitoring and stimulate and support monitoring in areas that lack capacity for sustained monitoring efforts. There was a clear consensus on the importance of revitalizing and formalizing the regional network, with the adoption of a simple and accessible regional data set and associated methods. The group agreed on a minimum core set of data to be collected, with associated recommended protocols and methods, developing a model for simple, accessible, but also scientifically pertinent and sustainable monitoring, both from a regional and local perspective.
The local situation on St Eustatius is in desperate need of scientifically pertinent and sustainable coral reef monitoring. Historically there have been only widely scattered and non-sustainable coral reef monitoring efforts in Statia’s waters. Following the protocols established at this and subsequent GCRMN workshops will allow the Island Government of St Eustatius to establish a 2015 baseline of coral reef health indicators, record future changes in coral reef health and manage natural and anthropogenic disasters which may affect the coral reefs.
The survey location is the St. Eustatius National Marine Park (SNMP), which surrounds the island from the high water mark to a depth of 30 meters. To maximize comparability across the region, GCRMN data will be collected solely from forereef habitats at depths ranging from 8 – 15 meters. This report descibes the main findings

Caribbean coral reefs have been declining for decades due to a combination of anthropogenic drivers such as unsustainable fishing practises, pollution, erosion and coastal development and natural phenomena like hurricanes. The degradation of coral reefs is characterised by, among others, a decline in coral cover, three dimensional structure, sharks, large groupers and snapper, herbivorous fish and invertebrates and an increase in macroalgal cover. In the past 40 years throughout the Caribbean large-scale shifts have occurred from coral dominated to macroalgal dominated reef communities.
Healthy coral reef ecosystems and sustainable fisheries are of utmost importance for the small island economies of Bonaire, Saba and St Eustatius. St. Eustatius (21 km2) is located in the north-eastern Caribbean and is surrounded by the 2700 ha St Eustatius National Marine Park (SNMP) which was established in 1996. From 1996 the SNMP included two marine reserves, the Northern Reserve (163 ha; rezoned in 2015 as harbour area) and the Southern Reserve (364 ha), in which no fishing or anchoring is allowed. In this report we document the 2015 status of a range of indicators for the health of St Eustatius coral reef ecosystem and its fisheries. Where possible the current status and trends of the indicators are discussed in a historical and wider geographical (Caribbean) perspective.

Status coral reef: Coral cover declined to a historic low. Dominance of macroalgae is established.The grouper species composition is characteristic for highly fished areas with little management.The status of key herbivorous fish (parrotfish and surgeonfish) biomass is reasonable at best.Using the most conservative survey results (precautionary approach), the overall Reef Health Index scored the reefs St Eustatius as “poor” in 2015

Status fishery: The capacity of the coastal fishery has remained roughly the same over the past 15 years, and possibly even since 1908

Unusually warm ocean temperatures surrounding Bonaire during the late summer and fall of 2010 caused 10 to 20 % of corals to bleach (Fig. 1). Bleaching persisted long enough to kill about 10 % of the corals within six months of the event (Steneck, Phillips and Jekielek Chapters 2A – C). That mortality event resulted in the first significant decline in live coral at sites monitored since 1999 (Fig. 2). Live coral declined from a consistent average of 48 % (from 1999 to 2009) to 38 % in 2011 (Steneck Chapter 1). This increase in non-coral substrate increased the area algae can colonize and the area parrotfish must keep cropped short (Mumby and Steneck 2008). For there to be no change in seaweed abundance would require herbivorous fish biomass and population densities to increase, but they have been steadily declining in recent years. This decline in parrotfish continues despite the establishment of no-take areas (called Fish Protection Areas – FPAs) and the recent law that completely bans the harvesting of parrotfish. The other major herbivore throughout the Caribbean is the black spined sea urchin, Diadema antillarum. However, since 2005 Diadema abundance has steadily declined. Damselfishes continue to increase in abundance (except in FPAs) and their aggressive territoriality reduces herbivory where they are present. These declines in herbivory resulted in a marked increase in macroalgae (Steneck Chapter 1). Although patchily distributed, algae on some of Bonaire’s reefs are approaching the Caribbean average (Kramer 2003). All research to date indicates that coral health and recruitment declines directly with increases in algal abundance (e.g., Arnold et al 2010).
On the bright side, predatory fishes are increasing in abundance in general but increasing most strongly in FPAs. Typically, responses to closed areas take 3 - 5 years to begin to manifest themselves. Predators of damselfishes have increased significantly in FPA sites and there, damselfish abundances are trending downward. These trends are the first signs of changes in the FPAs, and they are encouraging.
Overall, Bonaire’s coral reefs today are more seriously threatened with collapse than at any time since monitoring began in 1999.
 
Monitoring Results
The abundance of live coral at the monitoring sites has been remarkably constant since 1999. However, the bleaching related mortality event (Fig. 1) resulted in the first marked decline in live coral.
Seaweed abundance (“macroalgae”) increased sharply in 2011. While the greatest increase in algae occurred at the 18th Palm site where effluent could have increased nutrient levels, most of the other sites showed marked increases in algal abundance (see Steneck Chapter 1). Coralline algae, which has been shown to facilitate coral recruitment, remains at or near unprecedentedly low levels (Fig 2). Herbivory from parrotfishes and the grazing sea urchin Diadema antillarum remains at or near the lowest levels recorded since monitoring began in 1999 (Fig. 3 and see Cleaver Chapter 5). Herbivory from parrotfish is widely thought to be most important (e.g., Steneck and Mumby 2008) but territorial damselfishes can negate parrotfishes’ positive effects by attacking grazing herbivores and preventing them from effectively grazing (Arnold et al 2010). Damselfish abundances have trended upward in recent years (Fig. 3). However, there is a hint of a reversal to this trend in the FPAs (see Arnold Chapter 3). This reversal is consistent with the possibility that areas without fishing have elevated abundances of damselfish predators such as species of groupers and snappers (Randall 1965)  
Predatory fishes including snappers, groupers, barracuda, grunts and others increased in abundance at our monitored sites (Fig. 4 and see DeBey Chapter 6a). Specific predators known to eat damselfishes (see Preziosi Chapter 6b) show variable population densities with only a hint of an increase in 2011.   
Predatory fishes increased in abundance in both biomass (most striking) and population densities (Fig. 5). While biomass of predators in FPA and control sites is identical, the population density of predators is slightly greater at FPA sites
Coral recruitment remained lower than recorded in 2003 and 2005 (Fig. 6). However, the abundance of juvenile corals was higher in 2011 than was quantified in 2009

This report characterizes the state of Bonaire’s reefs as of March 2005. We pay particular attention to structural and functional attributes of reefs that have changed in so many other Caribbean reefs. We characterize coral reefs by their resident organisms and the forces regulating their distribution and abundance. Thus, corals, algae and fish define the “structure” of coral reefs but climate changes, diseases, hurricanes, overfishing, sedimentation and excess nutrients may affect how they “function”. Recent unfavorable changes in the structural and functional attributes of reefs have caused “the coral reef crisis” (Bellwood et al. 2004). In Caribbean coral reefs the most alarming changes have been the declines in the abundance of corals, sea urchins and reef fishes and the accompanying increases in large harmful seaweeds (called “macroalgae”). The decline in coral and increase in macroalgae, called a “phase shift”, represents a significant change in the structure of coral reef ecosystems that could lower its resilience.

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In March of 2005, a team of graduate students from the University of Maine revisited six study reefs on Bonaire to determine the status of those reefs and to detect if any change has occurred since March of 2003 when the last such survey was conducted. The study sites established in 2003 from north to south are: Karpata, Barcadera, Reef Scientifico, Forest on Klein Bonaire, Plaza and Windsock. Bonaire’s shallow (10 m) reefs remain in good condition. Coral cover averaged 47% in 2005 compared to 46% in 2003 (no change). Turf algae have increased and coralline algae have declined slightly over the past two years. Harmful seaweed “macroalgae” abundance remains low (2% in 2005 and 5% in 2003; see Steneck in this report) at the 10 m depth we studied. At depths below 20 m, macroalgae are now and have been (for at least the past 30 years) much more abundant (e.g. Van den Hoek et al. 1975) The absence of macroalgae in Bonaire most likely relates to the abundance of seaweedeating species or “herbivores”. Caribbean-wide, harmful macroalgal seaweed abundance corresponds inversely with the abundance of grazing fish such as parrotfish and tangs (Fig. 1). No comparable plot exists for seaweed abundance and any other measured factor on reefs.

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Changes over the past two decades
Comparisons between the status of reefs over a few years tell us little about long-term changes. For example, today there is a distinct demarcation between where Bonaire’s fringing reefs begin at 5 to 10 m depth and the shore. This region today is largely coralfree and dominated by rubble and sediment laden turf algae. However, this may not have always been the case. Prior to whiteband disease that killed nearly 90% of the elkhorn and staghorn corals in the Caribbean (i.e. Acropora palmata and A. cervicornis) (Aronson et al. 1998, Aronson and Precht 2001), most of the near shore zone was coral-dominated.
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Coral cover in the near shore zone surrounding Bonaire has declined dramatically and is now dominated by dead coral rubble where once elkhorn and staghorn corals had formed near monocultures prior to white band disease. Five of our six study sites have changed dramatically over the past 20 years except for Karpata. The decline of the Acropora species may have allowed competitively inferior species such as lettuce, pencil, finger and fire corals (Agaricia spp, Madracis spp, Porites porities and Millepora complanata) to expand since all have increased in abundance since the Van Duyl study (1985). Corals are not the only group to have changed dramatically since the 1980s. Diadema antillarum, the dominant grazing sea urchins was abundant in the near shore zone until it succumbed to the mass mortality of the mid 1980s. Today, more than 20 years later it remains below detectable levels at most of the sites we studied (Smith and Malek this report, Steneck this report). These changes, along with the significant declines in large predator finfish (see Bonaire Report 2003) indicate that several key players for the resilience of coral reefs (e.g. Fig. 3) have declined in abundance.

Abstract

Benzophenone-3 (BP-3; oxybenzone) is an ingredient in sunscreen lotions and personal-care products that protects against the damaging effects of ultraviolet light. Oxybenzone is an emerging contaminant of concern in marine environments—produced by swimmers and municipal, residential, and boat/ship wastewater discharges. We examined the effects of oxybenzone on the larval form (planula) of the coral Stylophora pistillata, as well as its toxicity in vitro to coral cells from this and six other coral species. Oxybenzone is a photo-toxicant; adverse effects are exacerbated in the light. Whether in darkness or light, oxybenzone transformed planulae from a motile state to a deformed, sessile condition. Planulae exhibited an increasing rate of coral bleaching in response to increasing concentrations of oxybenzone. Oxybenzone is a genotoxicant to corals, exhibiting a positive relationship between DNA-AP lesions and increasing oxybenzone concentrations. Oxybenzone is a skeletal endocrine disruptor; it induced ossification of the planula, encasing the entire planula in its own skeleton. The LC50 of planulae exposed to oxybenzone in the light for an 8- and 24-h exposure was 3.1 mg/L and 139 µg/L, respectively. The LC50s for oxybenzone in darkness for the same time points were 16.8 mg/L and 779 µg/L. Deformity EC20 levels (24 h) of planulae exposed to oxybenzone were 6.5 µg/L in the light and 10 µg/L in darkness. Coral cell LC50s (4 h, in the light) for 7 different coral species ranges from 8 to 340 µg/L, whereas LC20s (4 h, in the light) for the same species ranges from 0.062 to 8 µg/L. Coral reef contamination of oxybenzone in the U.S. Virgin Islands ranged from 75 µg/L to 1.4 mg/L, whereas Hawaiian sites were contaminated between 0.8 and 19.2 µg/L. Oxybenzone poses a hazard to coral reef conservation and threatens the resiliency of coral reefs to climate change.

Bonaire’s reefs remain among the best in the Caribbean. However, our monitoring has revealed some potentially troubling trends that may require management action. In 2005, we reported to the Bonaire Marine National Park on the status of Bonaire’s coral reefs, and we suggested a strategy for monitoring trends among four key reef attributes we believe track the health and resilience of Bonaire’s reefs (Steneck and McClanahan 2005). Here we report the results of monitoring studies conducted 2003, 2005 and now 2007 at each site. Where appropriate, we drew from Bonaire’s first AGRRA assessment conducted in February 1999 (Kramer and Bischof 2003) to extend temporal trends over a period of eight years. 
Troubling trends
We see three troubling trends of increased macroalgae, declining herbivory from parrotfish, and increases in damselfish populations. Of these, the first two are most serious (see Chapters 1, 2 and 3). Secondary trends of concern, increases in damselfish populations (Chapter 4) and declines in coralline algae (Chapter 1), could lead to reduced recruitment of reef corals (Chapter 7), but to date this is not evident (Chapter 7). Importantly, coral cover remains relatively high (Chapter 1). The monitored group of carnivorous fishes, the lutjanid snappers, are holding constant but we remain concerned about the past (Steneck and McClanahan 2003) and continued loss of other larger bodied reef carnivores such as groupers and barracuda. The positive ecological role of parrotfish is well documented (e.g. Mumby et al. 2006) so their decline is troubling. It is unclear exactly why their population densities are declining. While parrotfish are not currently a widely sought group of reef fish (Chapter 8), fishing pressure on them is growing. It is possible they are vulnerable to even modest fishing pressure, particularly from fish traps. Accordingly, we recommend that the capture and killing of parrotfish be stopped because of their key ecological role on Bonaire’s coral reefs. Further, other groups of grazing herbivores such as the longspined sea urchin (Diadema antillarum) are increasing but too slowly to effectively replace the functional role of parrotfish (Chapter 1). We suggest continued monitoring of key drivers of reef health (coral cover, algal abundance, herbivory and coral recruitment). Some standard protocols such as the Atlantic and Gulf Rapid Reef Assessment (AGRRA) are entirely commensurable with the data presented in our reports in 2003, 2005 and 2007 (this report). A streamlined monitoring protocol is likely to be most useful to managers to alert them as a potential problem is growing and, perhaps more importantly, to show improvement when it occurs.