Thinking and managing outside the box: coalescing connectivity networks to build region-wide resilience in coral reef ecosystems

As the science of connectivity evolves, so too must the management of coral reefs. It is now clear that the spatial scale of disturbances to coral reef ecosystems is larger and the scale of larval connectivity is smaller than previously thought. This poses a challenge to the current focus of coral reef management, which often centers on the establishment of no-take reserves (NTRs) that in practice are often too small, scattered, or have low stakeholder compliance. Fished species are generally larger and more abundant in protected reserves, where their reproductive potential is often greater, yet documented demographic benefits of these reproductive gains outside reserves are modest at best. Small reproductive populations and limited dispersal of larvae play a role, as does the diminished receptivity to settling larvae of degraded habitats that can limit recruitment by more than 50%. For “demographic connectivity” to contribute to the resilience of coral reefs, it must function beyond the box of no-take reserves. Specifically, it must improve nursery habitats on or near reefs and enhance the reproductive output of ecologically important species throughout coral reef ecosystems. Special protection of ecologically important species (e.g., some herbivores in the Caribbean) and size-regulated fisheries that capitalize on the benefits of NTRs and maintain critical ecological functions are examples of measures that coalesce marine reserve effects and improve the resilience of coral reef ecosystems. Important too is the necessity of local involvement in the management process so that social costs and benefits are properly assessed, compliance increased and success stories accrued.     

Community involvement in management for maintaining coral reef resilience and biodiversity in southern Caribbean marine protected areas

Climate change is posing new challenges to conservation because management policies on protected coral reefs are less effective than they were before the current ecosystem degradation. Coral reefs, the most diverse and complex marine ecosystem provide economic services for millions, but are seriously threatened worldwide because reef-building corals are experiencing bleaching phenomena and a steady decline in abundance. The resources of a Marine Protected Area (MPA) in Cartagena, Colombia, are in constant decline, despite a current management plan and on-site staff, urging new conservation actions. A multidisciplinary team gathered to evaluate management effectiveness including biophysical, socioeconomic and governance indicators. Coral cover and fish diversity and abundance were low both inside and outside the MPA, which suggests a limited efficiency of management. Currently, the MPA is a reef with low coral cover and high algae cover as well as large dead coral areas, which are generally signs of highly degraded reef habitats. Live coral cover in the MPA was represented by pioneer coral species such as Agaricia tenuifolia and Porites astreoides. Nonetheless, 35% of the scleractinian species sampled in the area harbored more than one zooxanthellae symbiont, which suggests potential resistance and resilience against coral bleaching. Maintenance of trophic structure and functional diversity is an important endeavor that should be a priority for management in order to allow ecosystem resilience. Social and governance indicators showed low-income levels and few opportunities for communities living in and around the park, low governability, weak communication among stakeholders and with authorities at different levels. As a result, problems related to over exploitation of resources were commonplace in the MPA. These results reflect low adaptive capacity of communities to comply with restrictive conservation rules, showing that establishment of a protected area is a necessary but insufficient condition to guarantee conservation goals. Ignoring the role of local communities only will exacerbate the problems associated with natural resources. Involvement of communities in strategic ecosystems management appears to be a requisite to improve effectiveness of protected areas, and participatory strategies, such as co-management, offer opportunities to improve governability while letting communities adapt to MPA needs.     

Capturing the cornerstones of coral reef resilience: linking theory to practice

Coral reefs can undergo unexpected and dramatic changes in community composition, so called phase shifts. This can have profound consequences for ecosystem services upon which human welfare depends. Understanding of this behavior is in many aspects still in its infancy. Resilience has been argued to provide insurance against unforeseen ecosystem responses in the face of environmental change, and has become a prime goal for the management of coral reefs. However, diverse definitions of resilience can be found in the literature, making its meaning ambiguous. Several studies have used the term as a theoretical framework and concern regarding its practical applicability has been raised. Consequently, operationalizing theory to make resilience observable is an important task, particularly for policy makers and managers dealing with pressing environmental problems. Ultimately this requires some type of empirical assessments, something that has proven difficult due to the multidimensional nature of the concept. Biodiversity, spatial heterogeneity, and connectivity have been proposed as cornerstones of resilience as they may provide insurance against ecological uncertainty. The aim of this article is to provide an overview of the divergent uses of the concept and to propose empirical indicators of the cornerstones of coral reef resilience. These indicators include functional group approaches, the ratios of “good” and “bad” colonizers of space, measurements of spatial heterogeneity, and estimates of potential space availability against grazing capacity. The essence of these operational indicators of resilience is to use them as predictive tools to recognize vulnerability before disturbance occurs that may lead to abrupt phase shifts. Moving toward operationalizing resilience theory is imperative to the successful management of coral reefs in an increasingly disturbed and human-dominated environment. Communicating by Ecology Editor Professor Peter Mumby Order of authors 2–3 is alphabetic     

Prioritizing key resilience indicators to support coral reef management in a changing climate

Managing coral reefs for resilience to climate change is a popular concept but has been difficult to implement because the empirical scientific evidence has either not been evaluated or is sometimes unsupportive of theory, which leads to uncertainty when considering methods and identifying priority reefs. We asked experts and reviewed the scientific literature for guidance on the multiple physical and biological factors that affect the ability of coral reefs to resist and recover from climate disturbance. Eleven key factors to inform decisions based on scaling scientific evidence and the achievability of quantifying the factors were identified. Factors important to resistance and recovery, which are important components of resilience, were not strongly related, and should be assessed independently. The abundance of resistant (heat-tolerant) coral species and past temperature variability were perceived to provide the greatest resistance to climate change, while coral recruitment rates, and macroalgae abundance were most influential in the recovery process. Based on the 11 key factors, we tested an evidence-based framework for climate change resilience in an Indonesian marine protected area. The results suggest our evidence-weighted framework improved upon existing un-weighted methods in terms of characterizing resilience and distinguishing priority sites. The evaluation supports the concept that, despite high ecological complexity, relatively few strong variables can be important in influencing ecosystem dynamics. This is the first rigorous assessment of factors promoting coral reef resilience based on their perceived importance, empirical evidence, and feasibility of measurement. There were few differences between scientists' perceptions of factor importance and the scientific evidence found in journal publications but more before and after impact studies will be required to fully test the validity of all the factors. The methods here will increase the feasibility and defensibility of including key resilience metrics in evaluations of coral reefs, as well as reduce costs. Adaptation, marine protected areas, priority setting, resistance, recovery.     

Complex interactions in the control of coral zonation on a Caribbean reef flat

Summary This study uses short-term assays and long-term transplant experiments to document the potential importance of fish predation and herbivory to the distribution and abundance of reef-building corals in a Caribbean back-reef system. Experimental manipulations of fish access reveal that the zonal patterns of the two reef-building corals Porites astreoides and P. porites f. furcata, dominant on shallow back-reef habitats, are strongly associated with the feeding intensity of parrotfishes. Differential palatability of the two corals to parrotfishes, the proximity of protective cover for large grazers and the availability of small refugia to harbor a cryptic grazer fauna are suggested as major features contributing to the observed patterns. A model predicting the interactions of various algivore/corallivore guilds on the relative dominance of Porites and algal populations is presented.     

Decadal-scale changes in abundance of non-scleractinian invertebrates on a Caribbean coral reef

The benthic community structure of the shallow reefs of St. John, US Virgin Islands, was studied from 1992 to 2007 to test the hypotheses that the abundances of non-scleractinian invertebrates have changed, and further, that the changes are associated with variation in the percentage cover of scleractinian coral and macroalgae. The study utilized photoquadrats (0.25 m²) from fringing reefs (7-9 m depth) characterized by igneous boulders and low (< 5%) coral cover, and results from six sites were pooled to describe these reefs as a single habitat. Photoquadrats were analyzed biennially for the abundance of invertebrates, particularly those belonging to four well represented classes (Anthozoa, Demospongiae, Echinoidea, and Polychaeta), as well as the cover of scleractinians and macroalgae. Overall, the combined (multivariate) abundance of 30 invertebrate taxa changed over time, the combined (multivariate) abundance of the four invertebrate classes changed over time, and the individual (univariate) abundance of anthozoans, sponges, and echinoids changed over time. Throughout the study, coral cover remained < 5%, and while it varied significantly, it did not display a consistent trajectory of change; in contrast, the cover of macroalgae increased throughout the study. While it is unsurprising that the abundances of invertebrates changed over 15 y, notably they varied even though coral cover remained stable, in only a few cases were they related positively to macroalgal cover, and in most cases it was members of the suspension feeding guild that became more abundant. These outcomes suggest that: (1) benthic invertebrates on the shallow reefs of St. John may be more strongly influenced by regional (e.g., larva supply) than local (e.g., coral cover) conditions, (2) Caribbean reefs have changed more since the early 1990s than can be inferred from variation in cover of coral and macroalgae, and (3) suspension feeding invertebrates have become more common on shallow fringing reefs in at least one location.     

Hyperspectral discrimination of coral reef benthic communities in the western Caribbean

Determining a subset of wavelengths that best discriminates reef benthic habitats and their associated communities is essential for the development of remote sensing techniques to monitor them. This study measured spectral reflectance from 17 species of western Caribbean reef biota including coral, algae, seagrasses, and sediments, as well as healthy and diseased coral. It sought to extend the spectral library of reef-associated species found in the literature and to test the spectral discrimination of a hierarchy of habitats, community groups, and species. We compared results from hyperspectral reflectance and derivative datasets to those simulated for the three visible multispectral wavebands of the IKONOS sensor. The best discriminating subset of wavelengths was identified by multivariate stepwise selection procedure (discriminant function analysis). Best discrimination at all levels was obtained using the derivative dataset based on 6–15 non-contiguous wavebands depending on the level of the classification, followed by the hyperspectral reflectance dataset which was based on as few as 2–4 non-contiguous wavebands. IKONOS wavebands performed worst. The best discriminating subset of wavelengths in the three classification resolutions, and particularly those of the medium resolution, was in agreement with those identified by Hochberg and Atkinson (2003) and Hochberg et al. (2003) for reef communities worldwide. At all levels of classification, reflectance wavebands selected by the analysis were similar to those reported in recent studies carried out elsewhere, confirming their applicability in different biogeographical regions. However the greater accuracies achieved using the derivative datasets suggests that hyperspectral data is required for the most accurate classification of reef biotic systems.     

Herbivory, connectivity, and ecosystem resilience: response of a coral reef to a large-scale perturbation

Coral reefs world-wide are threatened by escalating local and global impacts, and some impacted reefs have shifted from coral dominance to a state dominated by macroalgae. Therefore, there is a growing need to understand the processes that affect the capacity of these ecosystems to return to coral dominance following disturbances, including those that prevent the establishment of persistent stands of macroalgae. Unlike many reefs in the Caribbean, over the last several decades, reefs around the Indo-Pacific island of Moorea, French Polynesia have consistently returned to coral dominance following major perturbations without shifting to a macroalgae-dominated state. Here, we present evidence of a rapid increase in populations of herbivorous fishes following the most recent perturbation, and show that grazing by these herbivores has prevented the establishment of macroalgae following near complete loss of coral on offshore reefs. Importantly, we found the positive response of herbivorous fishes to increased benthic primary productivity associated with coral loss was driven largely by parrotfishes that initially recruit to stable nursery habitat within the lagoons before moving to offshore reefs later in life. These results underscore the importance of connectivity between the lagoon and offshore reefs for preventing the establishment of macroalgae following disturbances, and indicate that protecting nearshore nursery habitat of herbivorous fishes is critical for maintaining reef resilience.     

Environmental education in Tobago's primary schools: a case study of coral reef education

Environmental education is a relatively new area on the primary school curriculum of Trinidad and Tobago. Because of the close relationship between human activities and the degradation of the natural environment in Tobago, environmental education will become increasingly important to the preservation and conservation of the island's fragile natural resources. Current teaching methods rely heavily on text books and utilise a lecture style that does not promote student interaction. Unfortunately, these methods are not very conducive to environmental education. As such, this paper examines a pilot program in which staff from the Buccoo Reef Trust taught students from 15 primary schools about coral reefs using interactive tools and hands-on methods as described in People & Corals: an Education Package for Primary Schools (People & Corals). The pilot program ran over an eight week period with prepared lessons being taught every two weeks and student evaluations taking place once before the first lesson and once after the last lesson. The lessons were supplemented with a field trip to a coral reef ecosystem. Despite several challenges that were faced in the implementation process, the overall outcome of the pilot program was successful. Teachers and students reacted positively to the information that was being shared, thereby reinforcing the effectiveness of using a dynamic, active method of teaching to advance environmental education.     

Facilitation in Caribbean coral reefs: high densities of staghorn coral foster greater coral condition and reef fish composition

Recovery of the threatened staghorn coral (Acropora cervicornis) is posited to play a key role in Caribbean reef resilience. At four Caribbean locations (including one restored and three extant populations), we quantified characteristics of contemporary staghorn coral across increasing conspecific densities, and investigated a hypothesis of facilitation between staghorn coral and reef fishes. High staghorn densities in the Dry Tortugas exhibited significantly less partial mortality, higher branch growth, and supported greater fish abundances compared to lower densities within the same population. In contrast, partial mortality, branch growth, and fish community composition did not vary with staghorn density at the three other study locations where staghorn densities were lower overall. This suggests that density-dependent effects between the coral and fish community may only manifest at high staghorn densities. We then evaluated one facilitative mechanism for such density-dependence, whereby abundant fishes sheltering in dense staghorn aggregations deliver nutrients back to the coral, fueling faster coral growth, thereby creating more fish habitat. Indeed, dense staghorn aggregations within the Dry Tortugas exhibited significantly higher growth rates, tissue nitrogen, and zooxanthellae densities than sparse aggregations. Similarly, higher tissue nitrogen was induced in a macroalgae bioassay outplanted into the same dense and sparse aggregations, confirming greater bioavailability of nutrients at high staghorn densities. Our findings inform staghorn restoration efforts, suggesting that the most effective targets may be higher coral densities than previously thought. These coral-dense aggregations may reap the benefits of positive facilitation between the staghorn and fish community, favoring the growth and survivorship of this threatened species.     

Comparative phylogeography in a genus of coral reef fishes: biogeographic and genetic concordance in the Caribbean

Geographic barriers that limit the movement of individuals between populations may create or maintain phylogenetically discrete lineages. Such barriers are often inferred from geographic surveys of a single mitochondrial marker to identify phylogenetic splits. Mitochondrial DNA, however, has an effective population size one-fourth that of nuclear DNA, which can facilitate the rapid evolution of monophyletic mtDNA lineages in the absence of geographic barriers. The identification of geographic barriers will thus be more robust if barriers are proposed a priori, and tested with multiple independent genetic markers in multiple species. Here, we tested two proposed marine biogeographic breaks located at the Mona Passage in the Caribbean Sea and at the southern end of Exuma Sound in the Bahamas. We sequenced mitochondrial cytochrome b (400 bp) and nuclear rag1 (573 bp) for nine species and colour forms (183 individuals total) within the teleost genus Elacatinus (Gobiidae) that span the proposed breaks. Our results showed that Mona Passage separated mtcyb and rag1 lineages, with no genetic exchange between populations separated by just 23 km. However, the Central Bahamas barrier was only weakly supported by our data. Importantly, neither barrier coincided with deep genetic splits. This suggests that these two barriers did not initially isolate regional populations, but instead disrupt ongoing gene flow between regions. Our inferred relationships further suggested a division of the Caribbean region into northwestern and southeastern regions, a pattern reflected by some freshwater and terrestrial vertebrates. Our results, coupled with genetic and demographic data from other reef fishes and corals, provide robust support for the Mona Passage as a long-term biogeographic barrier for Caribbean animals.     

Detection of gaps in the spatial coverage of coral reef monitoring projects in the US Caribbean and Gulf of Mexico

As part of the US Coral Reef Task Force's National Program to Map, Assess, Inventory, and Monitor US Coral Reef Ecosystems, a comprehensive survey of projects/programs monitoring coral reef ecosystems and related habitats (i.e., seagrass beds and mangroves) in the US Caribbean and Pacific was undertaken. Information was gathered on a total of 296 monitoring and assessment projects conducted since 1990 in the US Caribbean and the Gulf of Mexico. Substantial gaps in monitoring coverage of US coral reef ecosystems were revealed through geographic information system (GIS) analysis of survey metadata. Although southern Florida contains approximately two-thirds of all marine monitoring projects found in the US Caribbean and Gulf of Mexico, we were unable to identify any ongoing projects that monitor coral reefs along Florida's western coast and off of the Florida Middle Grounds. Additionally, Florida is covered by approximately 1 900 km2 of mangroves, yet there were only four ongoing projects that monitor this ecosystem, leaving gaps in coverage in the Lower and Middle Keys and along the eastern and western coasts. The Flower Garden Banks National Marine Sanctuary, located offshore of the Texas/Louisiana border, has an integral long-term monitoring program, but lacks a monitoring project that gathers long-term, quantitative data on reef lish abundance and certain water quality parameters. Numerous coral reef monitoring projects in Puerto Rico are concentrated on the island's southwestern coast surrounding La Parguera, while far fewer monitoring projects are conducted along the northern and southeastern coasts and around Vieques Island. In the US Virgin Islands, the paucity of monitoring projects in large areas of St. Croix and St. Thomas contrasts with monitoring activity in three marine protected areas (MPAs), where 66% of the US Virgin Islands' coral reef monitoring sites were found. Only a series of assessments have been conducted at Navassa, a small, uninhabited island located 55 km west of Haiti and 137 km northeast of Jamaica. In order to better understand changes in coral reef communities and to produce a series of biennial reports on the status of US coral reef ecosystems, the National Oceanic and Atmospheric Administration (NOAA) is developing a national coral reef monitoring network. This network has already begun to fill some of these gaps in monitoring coverage through issuing cooperative grants to states and territories to build long-term monitoring capacity.     

A standard unit for monitoring recruitment of fishes to coral reef rubble

We developed a benthic standard monitoring unit for recruitment of fishes (SMURF) to sample fishes that settle in coral rubble and tested it on three fringing reefs on the west coast of Barbados, West Indies. These rubble SMURFs are inexpensive to construct and permit newly settled fishes, including cryptic, secretive and small species, to be quickly and fairly completely (> 83%) removed by divers without returning the unit to the surface. Over a 3-month period involving 9 collections, 32 units on 3 reefs yielded 948 newly settled fishes belonging to 28 taxa (3.3 ± 0.2 S.E. recruits per sample, n = 287) in addition to numerous crustaceans. Most specimens were Sparisoma spp. (Scaridae) (41.8%) and Stegastes partitus (Pomacentridae) (13.6%), with moderate numbers of Scarus spp. (Scaridae) (8.6%), Lythrypnus spp. (Gobiidae) (7.4%), and Pseudogramma gregoryi (Serranidae) (7.2%). Sampling SMURFs at 1-day rather than 11-day intervals yielded approximately twice as many fish, although some taxa were not affected by sampling frequency, indicating taxon-specific differences in post-settlement loss rates. Netting, intended to reduce predation on settlers, did not affect settlement estimates unless algae grew on it, suggesting that the SMURF design minimizes fish predation even in the absence of the netting. Over time, however, the netting resulted in substantial algal growth that was associated with an increase in abundance of Sparisoma spp. and a decrease in the abundance of S. partitus. This suggests that settler estimates are more affected by microhabitat changes from algal growth than by predation. During low settlement periods, SMURFs performed better than light-traps in assessing the daily input of new settlers of two abundant taxa. Eight SMURFs per reef were sufficient to demonstrate differences in settlement rates and temporal correlations in settlement within and among reefs. This study underscores the potential of benthic SMURFs to measure settlement of coral reef fishes at a range of spatio-temporal scales with moderate research cost and effort, and to facilitate the study of the settlement stage of several taxa.     

Recent changes in coral assemblages of a South African coral reef, with recommendations for long-term monitoring

Two-mile reef, Sodwana, South Africa is an unusual coral reef, being situated on a submerged fossilized sand dune and being very southerly (27°54). It is a popular Scuba diving venue receiving about 100000 dives year^–1. The line-intercept transect method, as recommended by the global coral reef monitoring network (GCRMN), was used to determine soft coral, hard coral and other benthos percentage cover. Physical coral damage, disease and bleaching were also recorded. Results were compared with those of B. Riegl (1993 – unpublished PhD thesis) 5 to 7 years earlier. The reef appears to be ecologically and highly dynamic. In the interim, there has been an increase in living benthos cover of 22.3% but also an increase in coral bleaching from 0% in 1993 to 1% in 1998. Physical damage, despite the large number of dives on the reef was minimal (1.52%), although it appears as if coral diseases may be increasing. The 20-m transects recommended by GCRMN are too long for this highly rugose reef with its distinct ridges and gullies. It is recommended that benthos cover, coral damage, bleaching and disease should be monitored annually using 40 5-m transects on the reef ridges and 40 5-m transects on the reef slopes.     

Caribbean reef coral diversity during the early to middle Miocene: an example from the Anguilla Formation

Reefal units in the early to middle Miocene of Anguilla consist of small, irregular lenses of variable coral composition which developed on a shallow, isolated offshore carbonate platform. They are composed of three distinct coral biofacies (branched, mound-shaped, and platy), which are haphazardly distributed in association with inter-reef sands. These units most probably formed as patch reefs across a broad, shallow area that was exposed to moderate energy conditions and periodically affected by storms. No evidence supports the existence of a more extensive barrier reef system. Comparisons with Oligocene and Mio-Pliocene reefs suggest that during the early to middle Miocene, Caribbean reefs were generally smaller in size (<100 m³) and lower in diversity (21 species in Anguilla, 42 species in total across the Caribbean) than Caribbean reefs during the late Oligocene or during the ate Miocene to early Pliocene (71 species in the Dominican Republic, 80 species total across the Caribbean). The early to middle Miocene Caribbean reef coral fauna was dominated by nine widespread species that occur in deposits of similar age in both Anguilla and Panama. More than half of the fauna consisted of Oligocene relicts. Of the 21 genera that first appeared in the Caribbean during Miocene time, 14 had first occurrences after the middle Miocene, as barrier reef systems became more prevalent across the central Caribbean.     

Modeled differences of coral life-history traits influence the refugium potential of a remote Caribbean reef

Coral Reefs - Remote populations can influence connectivity and may serve as refugia from climate change. We investigated two reef-building corals (Pseudodiploria strigosa and Orbicella franksi)...     

Connectivity and resilience of coral reef metapopulations in marine protected areas: matching empirical efforts to predictive needs

Design and decision-making for marine protected areas (MPAs) on coral reefs require prediction of MPA effects with population models. Modeling of MPAs has shown how the persistence of metapopulations in systems of MPAs depends on the size and spacing of MPAs, and levels of fishing outside the MPAs. However, the pattern of demographic connectivity produced by larval dispersal is a key uncertainty in those modeling studies. The information required to assess population persistence is a dispersal matrix containing the fraction of larvae traveling to each location from each location, not just the current number of larvae exchanged among locations. Recent metapopulation modeling research with hypothetical dispersal matrices has shown how the spatial scale of dispersal, degree of advection versus diffusion, total larval output, and temporal and spatial variability in dispersal influence population persistence. Recent empirical studies using population genetics, parentage analysis, and geochemical and artificial marks in calcified structures have improved the understanding of dispersal. However, many such studies report current self-recruitment (locally produced settlement/settlement from elsewhere), which is not as directly useful as local retention (locally produced settlement/total locally released), which is a component of the dispersal matrix. Modeling of biophysical circulation with larval particle tracking can provide the required elements of dispersal matrices and assess their sensitivity to flows and larval behavior, but it requires more assumptions than direct empirical methods. To make rapid progress in understanding the scales and patterns of connectivity, greater communication between empiricists and population modelers will be needed. Empiricists need to focus more on identifying the characteristics of the dispersal matrix, while population modelers need to track and assimilate evolving empirical results.     

Mangrove and coral reef sponge faunas: untold stories about shallow water Porifera in the Caribbean

Sponge faunas from coral reefs and mangrove ecosystems in the Caribbean have mostly been studied from an ecological perspective, with researchers considering the effects of physical and biological factors on their species distribution. To discern evolutionary patterns, this study analyzed the systematic composition, taxonomic diversity, and ecological properties (reproductive strategies, size, shape, endosymbiosis) of mangrove and reef sponge assemblages from seven distant Caribbean localities. Species composition was compared by use of cluster analysis (Sørensen’s), and taxonomic diversity by use of the biodiversity index average taxonomic distinctness (AvTD). Mangrove and reef-associated sponge faunas were found to be statistically dissimilar, with the AvTD values suggesting stronger taxonomic bias toward specific groups in mangroves, irrespective of geographic distance. Most Demospongiae orders have 30–50% more species in coral reefs than in mangroves. The richest reef genera (Agelas, Aplysina, Callyspongia, Petrosia, and Xestospongia) rarely colonize contiguous mangrove formations. The distribution and diversity of suprageneric taxa suggest that coral reef sponge assemblages might represent an older fauna. This historical interpretation would place mangrove subtidal habitats as the youngest marine ecosystem, rather than a below-optimum ecosystem. Life history traits support a biological split discussed here from the perspective of distinct evolutionary histories and different environmental conditions.     

Depth-related variation in epiphytic communities growing on the brown alga Lobophora variegata in a Caribbean coral reef

Lobophora variegata is a dominant macroalga on coral reefs across the Caribbean. Over the last two decades, it has expanded its vertical distribution to both shallow and deep reefs along the leeward coast of the island of Cura?ao, Southern Caribbean. However, the ecological implications of this expansion and the role of L. variegata as a living substratum are poorly known. This study compared epiphytic algal communities on L. variegata blades along two depth transects (6?C40?m). The epiphytic community was diverse with a total of 70 species of which 49 were found directly attached to L. variegata. The epiphytic community varied significantly between blade surface, depth and site. The greatest number of genera per blade was found growing on the underside of the blades regardless of site and depth. Filamentous red algae (e.g. Neosiphonia howei) were commonly found on the upperside of the blades over the whole depth gradient, whereas the underside was mainly colonized by calcifying (e.g. Hydrolithon spp., Jania spp., Amphiroa fragillissima), fleshy red algae (e.g. Champia spp., Gelidiopsis spp., Hypnea spinella) and foliose brown alga (e.g. Dictyota spp.). Anotrichum tenue, a red alga capable of overgrowing corals, was a common epiphyte of both blade surfaces. L. variegata plays an important role as a newly available substratum. Thus, its spread may influence other algal species and studies of benthic macroalgae such as L. variegata should also take into consideration their associated epiphytic algal communities.