Wakatobi Marine National Park Research Articles

Survival rates of branching Acropora morphologies on coral rubble stabilization structures

Compact bushy and expansive branching Acropora survival rates were compared in an experimental restoration setting. Coral fragments were sourced as corals of opportunity (CoPs) or refragmented from CoPs reared on a floating mid‐water rope nursery. Fragments were attached in single‐species and mixed‐species aggregations to modular substrate stabilization structures (reef stars) on degraded, unconsolidated dead coral rubble slopes in Wakatobi Marine National Park, central Indonesia. In total, 1440 Acropora fragments were outplanted to 96 reef stars across five experimental restoration blocks at 14 m depth. Fragment survival was recorded 40–44 months post‐attachment. Survival had a significant relationship with fragment morphology (p < 0.001) and aggregation type (p < 0.01). Sourcing fragments as CoPs or from the nursery did not have a significant relationship with survival. No significant relationships were found with fragment survival for any interactions between morphology, outplanted aggregation, and source. Survival rates for bushy Acropora were 3.44 times and 5.25 times higher than for expansive species for direct CoP outplants and nursery‐reared corals, respectively. The results demonstrate the potential efficacy of returning complex bushy branching Acropora morphologies to mid‐depth reef slopes previously dominated by the genus, using single‐species aggregations interspersed with mixed‐species aggregations. The study also supports using mid‐water nurseries to create a closed or semi‐closed nursery cycle to scale up restoration, and proposes introducing the term “biomass production system” to distinguish this as a process distinct from other coral nursery approaches.

Coral health assessment of two marine national parks (takabonerate and wakatobi) in southern sulawesi

Coral reef ecosystems carry out a wide range of ecological functions and sustain the livelihoods of coastal communities through fisheries, coastal protection, and tourism. However, the coral condition has declined recently due to climate changes and anthropogenic activities. This study was undertaken in May 2019 to assess reef health status in Takabonerate and Wakatobi Marine National Park based on three components: live coral cover, resilience component (macroalgae and rubble cover), and fish biomass. The highest coral cover was 45.53% (Wanci), with an average cover of 24.6% and 29.48% in Takabonerate and Wakatobi. The average biomass of reef fish in Wakatobi was higher in Wakatobi (1.26 kg/ha) than in Takabonerate (0.70 kg/ha). For the resilience score, the average cover of macroalgae and rubble was 0.11% and 6.35% in Takabonerate and 1.64% and 0.51% in Wakatobi. Based on the coral, resilience, and biomass fish score, the Coral Health Index scored 5 (fair) and 9 (good) for Takabonerate and Wakatobi. The data suggested that reefs in both locations could recover from disturbance. However, the low biomass of targeted fish in the Takabonerate shows high fishing activities, which might lead to a direct/indirect impact on coral health.

A Century long of coral records of heavy metals in coastal water of Wakatobi Marine National Park, South East Sulawesi

Scleractinian corals absorb heavy metals in their skeletons; therefore, corals can be used as environmental recorders due to incorporating certain metals for centuries. The research was conducted in Wakatobi Marine National Park (WMNP) using a core of massive coral Porites Sp. to determine heavy metals’ concentrations and assess the possible impact on the coastal water. The sample was collected by drilling the coral vertically using a pneumatic tool. Annual banding was determined by using x-ray radiography, continued with sub-sampled from each band, and analyzed using an Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES) for heavy metals determination. Enrichment Factor (EF) and Principal Component Analysis (PCA) were applied for assessing possible impact and differentiating between the heavy metals, respectively. The concentrations of heavy metals fluctuated during the period of the year 1917 to 2016, with the average concentration were 0.55 %, 0.07 %, 2.46 ppm, 3.86 ppm, 5.70 ppm, 63.22 ppm, 0.66 ppm, 3.16 ppm, 0.66 ppm, and 42.59 ppm for Sr, Mg, Mn, Ba, Cu, K, Pb, Zn, Cr, and Al, respectively. EF for all heavy metals showed that the coastal area was at the level of very small pollution (EF<2); therefore, it can be used as baseline data.

Estimates of sponge consumption rates on an Indo-Pacific reef

Determining predator diets is essential for understanding the strength of top-down processes and how they cascade through food webs. This is especially important for sponges, key members of benthic communities, whose dominance has increased in recent years on some coral reefs. However, the diversity of spongivorous fishes and the sponges they consume are relatively unknown. Here, we estimated sponge consumption by spongivorous fishes in the Wakatobi Marine National Park, Indonesia. We deployed cameras to identify fish biting at the dominant reef sponge Xestospongia spp. and then used gut content analysis and fish abundance estimates to quantify sponge consumption. In total, 33 species from 10 families of reef fish were identified taking bites from Xestospongia spp.; however, the 2 most prolific sponge-grazers, Ctenochaetus binotatus and Chaetodon kleinii, had no sponge in their guts, showing that for some fish, bites on sponge surfaces are not reliable evidence of sponge consumption. Gut contents indicated that Pygoplites diacanthus was an obligate spongivore, while Pomacanthus imperator, P. xanthometopon, Zanclus cornutus and Siganus punctatus regularly consumed sponges. Sponge consumption by these 5 spongivores was estimated at 46.6 ± 18.3 g sponge 1000 m-2 d-1. Molecular approaches developed to sequence the 18S gene for sponges consumed by angelfishes led to the successful amplification of 14 consumed sponges representing 6 orders of Porifera. We provide the first estimate of sponge consumption in the Indo-Pacific and are the first to successfully sequence partially digested sponges from fish stomachs, identifying several sponges previously unknown to be consumed by spongivores.

Bridging and Bounding Social Capital: Social Interaction Analysis of Islets Islanders in Wakatobi Marine National Park

The purpose of this paper is to provide an overview of the differences in the strength of social capital that is bonding and bridging two community groups, namely land-dwellers and Sama Bajo boat-dwellers in three islands in Wakatobi Marine National Park. This study used a post-positivistic research paradigm, and the primary data were collected by using a questionnaire to 240 respondents who represented the group of land-dwellers and Sama Bajo boat-dwellers on the islands of Wangi-wangi, Kaledupa, and Tomia. This research was also supported by qualitative data through in-depth interviews from several informants and desk studies. The results showed that bridging social capital relations tend to be weak in the two forms of interactions between the Sama Bajo and the land-dwellers on Wangi-wangi Island and Kaledupa Island, while bridging social capital tend to be secured in Tomia Island. We found that the social context through the historical links in the past and identity played a role in the relationship of bridging social capital and bonding social capital in the three communities as an analytical unit of this research.

Social network analysis: Key actors of cooperation between Sama Bajo and land-dwellers in Wakatobi marine national park

The relationship between Sama Bajo’s small-scale fishers and land-dwellers are unique and paradox. These ties embedded in the everyday economic and social life of Sama Bajo as an Indonesian iconic maritime tribe. This article will identify key actors between Sama Bajo and varied land-dwellers. We presume that the actors support cooperation and enhance the social resilience of Sama Bajo communities in marine preserve social context. The research was conducted from May until June 2019 in three Sama Bajo villages and land-dwellers islands in Wakatobi Regency. A social mapping, using UCINET 6.0, is offered to seek key actors in the different local social context of land-dwellers. Research findings found that key actors related to trading networks, social identity, and gender dimension. Later, the actors’ social relation has contributed to the social resilience amongst three different Sama Bajo communities in Wakatobi Marine National Park.

Spatial variation in the benthic community composition of coral reefs in the Wakatobi Marine National Park, Indonesia: updated baselines and limited benthic community shifts

AbstractCoral reefs have experienced extensive degradation across the world over the last 50 years as a result of a variety of stressors operating at a range of spatial and temporal scales. In order to assess whether declines are continuing, or if reefs are recovering, detailed baseline information is required from across wide spatial scales. Unfortunately, for some regions this information is not readily available, making future reef trajectories difficult to determine. Here we characterized the current benthic community state for coral reefs in the Wakatobi region of Indonesia, one of the most biodiverse marine regions in the world. We surveyed 10 reef sites (5, 10 and 15 m depth) to explore spatial variation in coral reef benthic communities and provide a detailed baseline. Previous data (2002–2011) were available for coral, sponges, algae and soft coral at six of our study sites. Using this information, we determined if any changes had occurred in dominance of these benthic groups. We found that benthic assemblage composition differed significantly over relatively small spatial scales (2–10 km) and hard coral cover was highly variable, ranging from 7–48% (average 19.5% ± 1.5 SE). While coral cover appears to have declined at all sites where data were available since 2002, we found little evidence for widespread increases in other benthic groups or regime shifts. Our study provides a comprehensive baseline dataset for the region that can be used in the future to determine rates of change in benthic communities.

Morphology and molecular characterization of newly isolated microalgae strain Chlorella volutis LIPI13-WKT066 from Wakatobi Islands and its potential use

Morphology and molecular characterization of microalgae isolated from Wakatobi Marine National Park was conducted. An understanding of the characteristics of morphology, molecular, as well as metabolites profile of the microalgae species is potentially useful for its future application. The primary aim of this study was to isolate, identify and characterize the microalgae strain isolated from Wakatobi Marine National Park labeled as LIPI13-WKT066 with the emphasis on the evaluation of amino acid content as a basis for its health application. Morphological observation under the microscope and molecular identification suggested that the microalgae strain of LIPI13-WKT066 belong to the strain under species of Chlorella volutis. Metabolite characterization of the microalgae strain showed that the content of protein (11.9%), lipid (12.4%) and carbohydrate (4.7%) was in the regular range. Further analysis of its amino acid content revealed the potency of the microalgae strain to be used as antihypertensive agent.

Domination of mesophotic ecosystems in the Wakatobi Marine National Park (Indonesia) by sponges, soft corals and other non-hard coral species

AbstractMesophotic ecosystems have been relatively poorly studied in the Indo-Pacific and in particular within the Coral Triangle region. Here we used a mini-ROV to explore the changes in major benthic groups at two sites (~200 m apart) in the Wakatobi Marine National Park, SE Sulawesi, Indonesia spanning shallow water coral reefs (5 m) to deeper water mesophotic ecosystems (80 m). We found very similar patterns at both sites where coral cover peaked at 15 m, declined rapidly by 30 m, and was virtually absent at 50 m. As coral declined there was a marked increase in sponges, soft corals and other encrusting organisms (including ascidians, bryozoans, tubeworms, gorgonians and molluscs). Importantly, our results differ from most previous studies in other geographic locations where hard corals extend much deeper. It is unclear what drives this difference but it may be related to higher levels of turbidity and therefore reduced light penetration in the Wakatobi compared with other areas, which limits the vertical extent of coral development.

The highly competitive ascidian Didemnum sp. threatens coral reef communities in the Wakatobi Marine National Park, Southeast Sulawesi, Indonesia

Coral reefs in the Wakatobi Marine National Park (WMNP), Indonesia, are protected but have been degrading in several areas due to local anthropogenic stressors. In affected areas, benthic surveys revealed the occurrence of a dominant ascidian species of the genus Didemnum, which may negatively impact the benthic community composition and structure. We quantified the abundance, substrate preference, and growth rate of Didemnum sp. in non-degraded and degraded reefs to assess its impact on the benthic community. While Didemnum sp. occurred in similar high abundances in both, non-degraded (0.66%) and degraded (0.75%) reef sites, this species showed a substantially (>10-fold) increased growth rate in degrading reefs (2.7 ± 0.98% day−1 increase in colony size, compared to 0.17 ± 0.39% day −1 in non-degraded reefs). Furthermore, Didemnum sp. colonized many different substrates and showed the ability to overgrow live corals quickly. These observations indicate that Didemnum sp. can be a severe threat to a reef community by outcompeting live corals and call for further studies on the interaction between environmental pollution and Didemnum growth patterns in coral reefs.

Environmental gradients structure gorgonian assemblages on coral reefs in SE Sulawesi, Indonesia

Indonesian coral reefs are the epicenter of marine biodiversity, yet are under rapid anthropogenically induced decline. Therefore, ecological monitoring of high diversity taxa is paramount to facilitate effective management and conservation. This study presents an initial report from a comprehensive survey of shallow-water (0–15 m) gorgonian assemblage composition and structure across sites with varying habitat quality within the Wakatobi Marine National Park (WMNP), SE Sulawesi, Indonesia. Current estimates of over 90 morphospecies from 38 genera and 12 families within the calcaxonian, holaxonian and scleraxonian groups are reported. This extensive survey confirms high local gorgonian abundance, diversity and species richness in the absence of anthropogenic influence and increasing with depth. Notably, morphological variants of the zooxanthellate species Isis hippuris Linnaeus, 1758, and Briareum Blainville, 1830, drive site and habitat assemblage differences across environmental gradients. Azooxanthellate taxa, particularly within the Plexauridae, drive species richness and diversity with depth. Of the 14 predictor variables measured, benthic characteristics, water flow and natural light explained just 30% of gorgonian assemblage structure. Furthermore, zooxanthellate and azooxanthellate taxa partitioned distinct gorgonian communities into two trophic groups—autotrophs and heterotrophs, respectively—with contrasting diversity and abundance patterns within and between study sites. This study strongly supports the WMNP as an area of high regional gorgonian abundance and diversity. Varying ecological patterns across environmental clines can provide the foundation for future research and conservation management strategies in some of the most biodiverse marine ecosystems in the world.

Acclimatory capacity of the Gorgonian Isis hippuris Linnaeus, 1758 to environmental change in SE Sulawesi, Indonesia

Coral reefs within the Indonesian archipelago are some of the most biodiverse yet anthropogenically compromised marine ecosystems. Within the Wakatobi Marine National Park (WMNP), SE Sulawesi, Indonesia, pronounced environmental clines are either caused or exacerbated by marine resource subsistence and destruction. The protected zooxanthellate gorgonian (sea fan coral) Isis hippuris Linnaeus, 1758 however, thrives on degraded reefs, with distinct morphotypes across contrasting reef environments within the region. To investigate if I. hippuris morphotypes are environmentally induced (plastic) or genetically derived (fixed), reciprocal transplant experiments (RTEs) were conducted across environmental gradients of light attenuation and anthropogenic disturbance. Phenotypic traits were measured and grouped into modules (colony, polyps, sclerites, optical parameters) to assess the physiological responses and endosymbiont specificity of each I. hippuris morphotype to environmental change. Trait modules were then modelled for tests of integration to determine phenotypic traits that interact to delimit I. hippuris morphotypes in response to environmental perturbation. After one-year, survivorship was lowest in clones transplanted from healthy to the degraded reef, suggesting the onset of immigrant inviability. Multivariate analyses revealed that phenotypic traits in healthy source colonies consistently showed significant trait plasticity, whereas residents from the impacted site were relatively insensitive to environmental change. Of the 38 phenotypic traits assessed, 17 were identified as driving test dissimilarities, most notably in branching dynamics, polyp density, capstan and spindle sclerite dimensions, and Symbiodinium chlorophyll a light energy absorbance efficiency (for photosynthesis). Specifically, photoacclimatory responses were integrated at the morphological and bio-optical levels, with chlorophyll a light harvesting efficiency maintained during reduced pigment density resulting from an increase in host sclerite articulation that maximized the internal light field in healthy clones on degraded reefs. Variable optical responses were not attributed to endosymbiont type, as all test colonies possessed a novel Symbiodinium Clade D1a. In summary, patterns of phenotypic variability within the I. hippuris holobiont likely represent incipient ecological divergence, with a high capacity for plasticity that has become fixed through ongoing anthropogenic disturbance on degraded reefs.

Adaptive mechanisms and physiological effects of suspended and settled sediment on barrel sponges

Coral reefs across the Indo-Pacific are among the most diverse in the world but like reefs globally, they remain vulnerable to a multitude of stressors, including coastal development and the resultant sedimentation. In the Wakatobi Marine National Park, Indonesia, some degraded reefs are characterised by high levels of sedimentation and low coral cover, but support large populations of the ecologically important giant barrel sponge Xestospongia testudinaria (Lamarck 1815). Barrel sponges can have a strong influence on water characteristics, yet tolerance and responses to sedimentation are unknown. This study examined the physiological effects of short-term exposure of X. testudinaria to suspended sediment. Respiration rates increased compared to controls when sponges were exposed to environmentally relevant suspended sedimentation concentrations of 75 and 150mgl−l. Sponge mucus production was observed as a mechanism to remove settled sediment for the first time and sediment clearance was filmed in situ over the course of 24h. Sponges produced mucus in response to sediment addition, with a mean clearance rate of 10.82±2.04%h−1 (sediment size fractions 63–250μm). Mucus production is an effective, but slow mechanism supporting barrel sponge survival in habitats experiencing high levels of sedimentation. Our results show that there are likely to be energetic consequences for sponges living in sedimented environments, which may influence the energy available for other demographic processes, and therefore have implications for barrel sponge population sustainability.

SUITABILITY ANALYSIS OF MULTISPECTRAL SATELLITE SENSORS FOR MAPPING CORAL REEFS IN INDONESIA CASE STUDY: WAKATOBI MARINE NATIONAL PARK

Providing accurate information on suitable multispectral satellite sensors for mapping coral reefs in Indonesia is a challenge for coastal remote-sensing experts. As coral reefs vary in spatial extent, shape, length, perimeter and/or distance to shore, the mapping of coral reefs will need different satellite sensors depending on the objectives and the kind of information required. This work compares the suitability of two kinds of multispectral satellite sensors for mapping coral reefs in Indonesia, high and moderate spatial resolution. This was done through a case study of Wakatobi Marine National Park since that represents many types of coral reef in Indonesia (fringing, barrier, atoll, and patch). Indonesian coral reef shapefile data 2010 was downloaded from UNEP (United Nations Environment Programme) website, and Landsat 7 ETM + images, path/row 112/064 was used to determine the terrestrial area of Wakatobi Islands. Both high and moderate spatial resolution sensors are suitable for mapping the benthic communities and geomorphic zones on coral reefs. The former are more accurate but they are also much less cost-effective, especially over large areas.

Spongivory in the Wakatobi Marine National Park, Southeast Sulawesi, Indonesia

Abstract: Sponges are functionally important coral reef fauna and there is strong evidence from the Caribbean that predation has important impacts on sponge-assemblage dynamics; whether the same is true for Indo-Pacific sponges remains unknown. As a first step toward understanding the potential effects of spongivores on sponge diversity and abundance, we identified sponge predators at nine sites in Wakatobi Marine National Park, Indonesia, and conducted a short-term caging experiment to examine the effects of excluding predators on noncryptic reef sponges at this location. Nudibranchs were the most abundant invertebrate spongivores, although their low densities are likely to limit their influence on sponges. Fish were the most abundant vertebrate spongivores with 16 species from six families observed feeding on sponges. Based on their abundance and our feeding observations, the fish with the greatest potential to influence sponge assemblages in Wakatobi Marine National Park were Zanclus cornutus, Chaetodo...

Photoacclimation supports environmental tolerance of a sponge to turbid low-light conditions

Changes to coral reefs are occurring worldwide, often resulting in declining environmental quality which can be in the form of higher sedimentation rates and increased turbidity. While environmental acclimation to turbid and low-light conditions has been extensively studied in corals, far less is known about other phototrophic reef invertebrates. The photosynthetic cyanobacteria containing sponge Lamellodysidea herbacea is one of the most abundant sponges in the Wakatobi Marine National Park (WMNP, Indonesia), and its abundance is greatest at highly disturbed, turbid sites. This study investigated photoacclimation of L. herbacea symbionts to turbid reef sites using in situ PAM fluorometry combined with shading and transplant experiments at environmental extremes of light availability for this species. We found in situ photoacclimation of L. herbacea to both shallow, clear, high-light environments and deep, turbid, low-light environments. Shading experiments provide some evidence that L. herbacea are dependent on nutrition from their photosymbionts as significant tissue loss was seen in shaded sponges. Symbionts within surviving shaded tissue showed evidence of photoacclimation. Lamellodysidea herbacea transplanted from high- to low-light conditions appeared to have photoacclimated within 5 d with no significant effect of the lowered light level on survival. This ability of L. herbacea to photoacclimate to rapid and extreme changes in light availability may be one of the factors contributing to their survival on more turbid reef sites in the WMNP. Our study highlights the ability of some sponge species to acclimate to changes in light levels as a result of increased turbidity.

Environmental influences on the Indo-Pacific octocoral Isis hippuris Linnaeus 1758 (Alcyonacea: Isididae): genetic fixation or phenotypic plasticity?

As conspicuous modular components of benthic marine habitats, gorgonian (sea fan) octocorals have perplexed taxonomists for centuries through their shear diversity, particularly throughout the Indo–Pacific. Phenotypic incongruence within and between seemingly unitary lineages across contrasting environments can provide the raw material to investigate processes of disruptive selection. Two distinct phenotypes of the Isidid Isis hippuris Linnaeus, 1758 partition between differing reef environments: long-branched bushy colonies on degraded reefs, and short-branched multi/planar colonies on healthy reefs within the Wakatobi Marine National Park (WMNP), Indonesia. Multivariate analyses reveal phenotypic traits between morphotypes were likely integrated primarily at the colony level with increased polyp density and consistently smaller sclerite dimensions at the degraded site. Sediment load and turbidity, hence light availability, primarily influenced phenotypic differences between the two sites. This distinct morphological dissimilarity between the two sites is a reliable indicator of reef health; selection primarily acting on colony morphology, porosity through branching structure, as well as sclerite diversity and size. ITS2 sequence and predicted RNA secondary structure further revealed intraspecific variation between I. hippuris morphotypes relative to such environments (ΦST = 0.7683, P < 0.001). This evidence suggests—but does not confirm—that I. hippuris morphotypes within the WMNP are two separate species; however, to what extent and taxonomic assignment requires further investigation across its full geographic distribution. Incongruence between colonies present in the WMNP with tenuously described Isis alternatives (Isis reticulata Nutting, 1910, Isis minorbrachyblasta Zou, Huang & Wang, 1991), questions the validity of such assignments. Furthermore, phylogenetic analyses confirm early taxonomic suggestion that the characteristic jointed axis of the Isididae is in fact a convergent trait. Thus the polyphyletic nature of the Isididae lies in its type species I. hippuris, being unrelated to the rest of its family members.

Spatial Pattern in Beta Diversity of Echinoidea and Asteroidea Communities from the Coastal Area of Tomia Island, Wakatobi Marine National Park, Southeast Sulawesi, Indonesia

The present study was aimed to elucidate the spatial pattern in the beta diversity of marine bentic for Echinoidea and Asteroidea that assemblages the coastal area of Tomia Island, Wakatobi Marine National Park, Indonesia. The two transect lines of 460 and 260 m in length with small quadrats of 1m2 wide were placed at the open and unopen beaches perpendicularly to the coastlines. The important value index and similarity index SI of organisms on these taxa were estimated in each the transect. Echinometra mathaei was the most dominant Echinoidea at open and unpen beaches, while Protoreaster nodusus was the most dominant Asteroidea at both areas. Most of SI values of Echinoidea at open beach were estimated less than 50%, which was lower than SI values that of organisms at unopen beach. On the other hand, most of SI values of Asteroidea at both areas were estimated more than 70% representing high similarity degree of its species composition among sites. The disimilarity index of organisms in the taxa of Echinoidea and Asteroidae was increased significantly as increasing the distance of among stands, which suggested that pettern in beta diversity of these taxa was associated with the spatial heterogenity.

The association between coral communities and disease assemblages in the Wakatobi Marine National Park, south-eastern Sulawesi, Indonesia

The relationship between coral community structure and disease prevalence is poorly understood, particularly in the Coral Triangle. Improved understanding of this relationship will assist in identifying assemblages that might be particularly vulnerable to disease, and in predicting possible future impacts. Here, we report results from the last 2 years (2010 and 2011) of a 4-year coral disease-monitoring program (2005, 2007, 2010, 2011) in the Wakatobi Marine National Park (Indonesia), and evaluate changes in total disease prevalence and coral cover since 2005. A comparison with previously published results from 2005 and 2007 indicates that the number of coral diseases increased from two to eight and total disease prevalence tripled between 2005 and 2011. We observed a dramatic decline in coral cover and an increase in disease prevalence at a site with a unique community of foliose corals. However, because of the 3-year period between surveys (2007, 2010), it is likely that the peak of the disease event was not observed. While multi-year studies provide useful insights into the relationships between community structure and disease, our results emphasise how determining the drivers of change in remote reef locations is especially challenging if events such as disease outbreaks are missed.

Resilience to Disturbance Despite Limited Dispersal and Self-Recruitment in Tropical Barrel Sponges: Implications for Conservation and Management

While estimates of connectivity are important for effective management, few such estimates are available for reef invertebrates other than for corals. Barrel sponges are one of the largest and most conspicuous members of the coral reef fauna across the Indo-Pacific and given their large size, longevity and ability to process large volumes of water, they have a major role in reef functioning. Here we used a panel of microsatellite markers to characterise the genetic structure of two barrel sponge species, Xestospongia testudinaria and a currently undescribed Xestospongia species. We sampled across seven populations in the Wakatobi Marine National Park, SE Sulawesi (Indonesia) spanning a spatial scale of approximately 2 to 70 km, and present the first estimates of demographic connectivity for coral reef sponges. Genetic analyses showed high levels of genetic differentiation between all populations for both species, but contrasting patterns of genetic structuring for the two species. Autocorrelation analyses showed the likely dispersal distances of both species to be in the order of 60 and 140 m for Xestopongia sp. and Xestospongia testudinaria, respectively, which was supported by assignment tests that showed high levels of self-recruitment (>80%). We also found consistently high inbreeding coefficients across all populations for both species. Our study highlights the potential susceptibility of barrel sponges to environmental perturbations because they are generally long-lived, slow growing, have small population sizes and are likely to be reliant on self-recruitment. Surprisingly, despite these features we actually found the highest abundance of both barrel sponge species (although they were generally smaller) at a site that has been severely impacted by humans over the last fifty years. This suggests that barrel sponges exhibit environmental adaptation to declining environmental quality and has important implications for the management and conservation of these important reef species.