Meesters, E.H.W.G.

1. 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. 2. 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. 3. Species presence and richness of different taxa were visually quantified in one hundred 25-m2 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). 4. Boosted regression tree models performed very well when explaining variability in total (823%), coral (806%) and fish species richness (773%), 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. 5. 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.

Dissolved organic carbon (DOC) release of three algal and two coral species was determined at three light intensities (0, 30–80, and 200–400 μmol photons m−2 s−1) in ex situ incubations to quantify the effect of light availability on DOC release by reef primary producers. DOC release of three additional algal species was quantified at the highest light intensity only to infer inter-specific differences in DOC release. For species tested at different light intensities, highest net release of DOC occurred under full light (200–400 μmol photons m−2 s−1). DOC released by benthic algae under full light differed (up to 16-fold) among species, whereas DOC release by scleractinian corals was minimal (Orbicella annularis Ellis and Solander, 1786) or net uptake occurred (Madracis mirabilis Duchassaing and Michelotti, 1860) independent of light availability. DOC concentrations and light intensities were also measured in situ near seven benthic primary producers, sediment, and in the water column at nine sites evenly distributed along the leeward coast of Curaçao. In situ DOC concentrations increased with light availability, although the magnitude of this positive effect differed among species and bottom types tested. In situ DOC concentrations were on average lower in November–December [87 (SD 45) μmol L−1] compared to May–June [186 (SD 136) μmol L−1], which can, at least partly, be explained by the lower light availability in the latter period. Our results suggest that DOC release by Caribbean benthic primary producers varies considerably among species and depends on light availability in reef algae. 

Outbreaks of Acropora and Diadema diseases in the 1970s and early 1980s, overpopulation in the form of too many tourists, and overfishing are the three best predictors of the decline in Caribbean coral cover over the past 30 or more years based on the data available. Coastal pollution is undoubtedly increasingly significant but there are still too little data to tell. Increasingly warming seas pose an ominous threat but so far extreme heating events have had only localized effects and could not have been responsible for the greatest losses of Caribbean corals that had occurred throughout most of the wider Caribbean region by the early to mid 1990s.
In summary, the degradation of Caribbean reefs has unfolded in three distinct phases:
1. Massive losses of Acropora since the mid 1970s to early 1980s due to WBD. These losses are unrelated to any obvious global environmental change and may have been due to introduced pathogens associated with enormous increases in ballast water discharge from bulk carrier shipping since the 1960s.
2. Very large increase in macroalgal cover and decrease in coral cover at most overfished locations following the 1983 mass mortality of Diadema due to an unidentified and probably exotic pathogen. The phase shift in coral to macroalgal dominance reached a peak at most locations by the mid 1990s and has persisted throughout most of the Caribbean for 25 years. Numerous experiments provide a link between macroalgal increase and coral decline. Macroalgae reduce coral recruitment and growth, are commonly toxic, and can induce coral disease.

3. Continuation of the patterns established in Phase 2 exacerbated by even greater overfishing, coastal pollution, explosions in tourism, and extreme warming events that in combination have been particularly severe in the northeastern Caribbean and Florida Keys where extreme bleaching followed by outbreaks of coral disease have caused the greatest declines.
 
In: Status and Trends of Caribbean Coral Reefs: 1970 - 2012. Jackson, J.B.C., Donovan, M.K., Cramer, K.L. Lam, W.. - Washington : Global Reef Monitoring Network, 2014 - p. 211 - 215.
 
Retreived from http://www.wageningenur.nl on April13, 2015

Four submersible dives off the coast of Bonaire (Caribbean Netherlands) and Klein Curaçao (Curaçao) to depths of 99.5–242 m, covering lower mesophotic and upper dysphotic zones, yielded 52 sponge specimens belonging to 31 species. Among these we identified 13 species as new to science. These are Plakinastrella stinapa n. sp., Pachastrella pacoi n. sp., Characella pachastrelloides n. sp., Geodia curacaoensis n. sp., Caminus carmabi n. sp., Discodermia adhaerens n. sp., Clathria (Microciona) acarnoides n. sp., Antho (Acarnia) pellita n. sp., Parahigginsia strongylifera n. sp., Calyx magnoculata n. sp., Neopetrosia dutchi n. sp., Neopetrosia ovata n. sp. and Neopetrosia eurystomata n. sp. We also report an euretid hexactinellid, which belongs to the rare genus Verrucocoeloidea, recently described (2014) as V. liberatorii Reiswig & Dohrmann. The remaining 18 already known species are all illustrated by photos of the habit, either in situ or ‘on deck’, but only briefly characterized in an annotated table to confirm their occurrence in the Southern Caribbean. The habitat investigated - steep limestone rocks, likely representing Pleistocene fossil reefs - is similar to deep-water fossil reefs at Barbados of which the sponges were sampled and studied by Van Soest and Stentoft (1988). A comparison is made between the two localities, showing a high degree of similarity in sponge composition: 53% of the present Bonaire-Klein Curaçao species were also retrieved at Barbados. At the level of higher taxa (genera, families) Bonaire-Klein Curaçao shared approximately 80% of its lower mesophotic and upper dysphotic sponge fauna with Barbados, despite a distance between them of 1000 km, indicating high faunal homogeneity. We also preliminarily compared the shallow-water (euphotic) sponge fauna of Curaçao with the combined data available for the Barbados, Bonaire and Klein Curaçao mesophotic and upper dysphotic sponges, which resulted in the conclusion that the two faunas show only little overlap

In this review the following three reef restoration techniques are discussed: 1. Coral gardening, 2. Larval seeding, and 3. Reef balls. These techniques are commonly used in the Caribbean and have widely different approaches. Coral gardening utilize the natural process of asexual reproduction through fragmentation to provide new coral clones for population growth. Healthy wild colonies are once clipped/fragmented and further grown (and cloned multiple times) in an underwater nursery and ultimately transplanted to the reef.
In contrast, larval seeding is based on the sexual reproduction of corals, where large amounts of coral eggs and sperm are collected in the field with subsequent fertilization in the lab. The coral recruits are then made to settle and grown in aquaria until a certain size, after which they are transplanted to the reef. Reef balls are artificial concrete structures designed to provide shoreline protection and sometimes shelter for fish, while at the same time providing substrate for natural recruitment and attachment of benthic organisms such as corals.
A general introduction to coral reproduction is provided to show how life history characteristics are used in restoration efforts and how these can affect the genetic variation within coral populations. The three approaches are compared based on:
1. Survival of fragments and larvae before transplantation to the reef.
2. Survival of transplants at the restoration site.
3. Introduction of exogenous material.
4. Indirect effects of coral restoration on the reef.
5. Genetic diversity.
6. Feasibility and effectiveness.
The main advantages of the production of colonies from fragments are that it bypasses the early larval stages where mortality is high and that new colonies can be grown completely in the field. Generally, the asexual reproduction technique demands less advanced expertise and the public outreach of this method is high because volunteers can easily be incorporated into the program. Furthermore, results become apparent relatively soon since the used species are relatively fast growing. However, there is the risk of creating populations with little genetic variability and the method is only applicable to branching coral species. Presently the method is mainly used for one single species, namely staghorn coral (Acropora cervicornis).
Larval seeding (sexual reproduction) is arguably the best method since it ensures natural genetic diversity and can be used with many species. The disadvantage with this method is that it demands a reasonably high level of expertise and takes more time than the asexual production of new colonies by fragmentation. Also a high percentage of new colonies is lost during the early stages. It is still mostly in the development phase.
Reef balls may increase fish biomass and protect shorelines, but their potential for coral reef restoration is judged to be limited due to the generally low levels of natural recruitment to these structures.
The restoration techniques suffer presently from a lack of independent scientific publications with good data to validate survival, regeneration, and growth rates of colonies in the different phases of the restoration program.
Different populations of the branching Acropora species can differ fundamentally in reproductive characteristics and may respond differently to environmental change. Their difference in strategy may also be a result of adaptation to local environmental factors. All studies and protocols thus stress the necessity to adapt methods to specific locations and environments.
Consideration of genetic factors is essential because the long-term success of restoration efforts (depending on resilience of the populations) may be influenced by genetic diversity of restored coral populations. The use of molecular tools may aid managers in the selection of appropriate propagule sources, guide spatial arrangement of transplants, and help in assessing the success of coral restoration projects by tracking the performance of transplants, thereby generating important data for future coral reef conservation and restoration projects.
It is proposed to study genetic variation in the natural populations around the islands of the Dutch Caribbean and within the various restoration projects in progress. Additionally, it is recommended to assess survival, growth and regeneration of fragments ánd mother colonies in the field. We recommend to combine characteristics of the two main coral restoration techniques (fragmentation and larval rearing) to create a new hybrid approach to increase survival of sexually derived colonies and genetic diversity. In addition, the cost-effectiveness of the larval seeding method should be ascertained and compared with the fragmentation method.
We conclude by pointing out that reef restoration can only be successful if environmental conditions are adequate for survival and growth of coral colonies. This will mean that presently the selection of restoration sites with good environmental conditions is crucial. Thus, active management of anthropogenic stressors is a prerequisite for reef restoration — if a reef is not effectively managed and chronic stressors persist or develop, restoration will ultimately fail. Reef restoration must only be considered as complementary to management tools that address the wider causes of reef degradation.

The land cover map of Saba gives a coarse representation of the distribution of forest, shrub, pasture and artificial surface. Invasive species (like Corallita) are included where technically possible. See this report for more information

Bonaire, St Eustatius and Saba, islands in the Caribbean, became Dutch municipalities in October 2010. These islands are considered hotspots of biodiversity. This brings along specific responsibilities, including a thorough conservation plan. Each plan and monitoring of it demands good basic knowledge and data. It is of great importance for many studies to have proper altitude maps, in addition to good topographical maps. Detailed elevation maps (Digital Terrain Models) are important not only for preprocessing of high resolution satellite imagery , but also for e.g. geomorphological studies, soil surveys, hydrological modelling, species niche modelling, that all need altitude as an important input data layer. At present there are no detailed digital terrain models for these islands, while these are especially important for Saba and St Eustatius that have a very varied and complex topography.

Quantitative habitat mapping and description form the basis for understanding the provisioning of ecosystem services and habitat connectivity, and hence provide an essential underpinning for marine spatial planning, management and conservation. Based on 869 video stations in a 150 x 200 m grid, we mapped 25.3 km2 of the near-shore island shelf of St. Eustatius at depths ranging 5-30 m. This yielded a coarse-grained map of the principal habitat classes of St. Eustatius’ seascapes. A total of nine principal seafloor habitats were distinguished. Gorgonian reefs amounted to 22% of the Statia Marine Park habitats sampled and were concentrated in the shallow wave-exposed eastern parts of the island (7.7 m average depths). The densest coral “scapes” and seagrass beds of St. Eustatius were concentrated at depths of about 24 m and only amounted to 4 and 5 percent resp. of the island shelf habitats studied. Whereas coral areas were essentially limited to the southern and south-western island shelf areas, seagrass beds were confined to the northern island shelf area. Including patch reef habitats, total hard coral-scape habitat for the St. Eustatius Marine Park amounted to about 19% of the area surveyed and about 475 ha of habitat. Sargassum reef habitat typically occurred at the seaward edge of communities dominated by hard coral growth.

The deep reef of Bonaire, Caribbean Netherlands, was explored with the aid of the “Curasub” submarine of Substation Curaçao. The shallow reefs of the Caribbean are considered a biodiversity hotspot, an area with exceptional diversity of plants, animals and ecosystems, yet surprisingly little is known about the flora and fauna of the deeper reefs.

Dives were made to depths of 140-250m.at three locations on the Southern coast of Bonaire: Kralendijk,Cargill, and Statoil. Distinct depth zonations in substrate features were visible. Coral reef was observed until approximately 45m, then followed a zone of sand mixed with varying amounts of stones. At each site a wide layer of cyanobacteria mats covering sand were found spanning the depths of 45m.to 90m.

The depth from 90-100m was typically dominated by sand with occasional small rocks on which fan corals and sponges resided. From 100-

150m depth fossil barrier reef and rodolith beds were observed, either in long stretches or in patches within a barren sandscape. By providing hard substrate, these fossil reefs displayed heightened biodiversity in a desert landscape of sand. Below 150m the substrate was generally dominated by fine sand. The cause of the cyanobacterial mats remains unclear. These mats are generally believed to indicate nutrient enriched (disturbed) environmental conditions, and should therefore be further studied to elucidate the cause. Trash was observed at all depths. High biodiversity was observed on the sporadic hard substrate below 100m, presumably fossil reef. In total 72 species were recorded, of which at least 15 species are new to science (shrimp, sponges, fish). The major focus was on sponges due to their importance in the deep reef in terms of diversity, filtering activities, biomass, and source of pharmaceutical compounds. A species list and picture gallery are provided in this report. This is just of subset of the true biodiversity of Bonaire’s deep reef. With the description of new species also comes a better understanding of ecosystems.

Benthic habitats (habitats occurring at the bottom of a water body) and coral reef ecosystems provide many functions. Currently, however, worldwide coral reefs are threatened by a number of factors and are degrading rapidly. Benthic maps are important for management, research and planning, but the benthic communities around St. Eustatius have not yet been accurately mapped or described.
Remote sensing imagery has been found to be a useful tool in providing timely and up-to-date information for benthic mapping and offers an approach that may complement the limitations of field sampling. Remote sensing in water, however, presents challenges mainly due to the complex physical interactions of absorption and scattering between water and light. Shorter wavelengths (-450 nm) penetrate deepest into the water column and longer wavelengths (-500-750 nm) are more rapidly absorbed and scattered. Therefore, the potential extent of use of remote sense imagery in the oceans relies more on shorter wavelengths (blue band), which have inherently noisier signals due to atmospheric effects.
This research explores the utility of multispectral imagery to identify and classify marine benthic habitats in the Dutch Caribbean island of St Eustatius. These include the comparison of two sensors with different spatial and spectral resolution, QuickBird (2.4m, 4 bands) and WorldView-2 (2.0m, 8 bands) for mapping benthic habitats. The study first investigates the existing methodologies for benthic habitat classification. The benefits of atmospheric correction, corrections for sun-glint effect and water column attenuation on the accuracy of classification maps are also assessed. Then, an object and pixel-based supervised classifications for the characterization of sea grass, sand and coral are performed. This research also evaluates the possibility to extract water depth from multispectral satellite imagery by the use of a ratio transform method. Bathymetric data is important for water column correction, to improve the classification accuracy and for the study of the ecology of the habitats.