Abstract:Despite global deterioration of coral reef health, not all reef-associated organisms are in decline. Bioeroding sponges are thought to be largely resistant to the factors that stress and kill corals, and are increasing in abundance on many reefs. However, there is a paucity of information on how environmental factors influence spatial variation in the distribution of these sponges, and how they might be affected by different stressors. We aimed to identify the factors that explained differences in bioeroding s… Show more
“…Further research is needed to determine how these reefs function, how they differ from shallow water reefs, and if they are able to support shallower water communities, for example through larval subsides. There is also a need to quantify the importance of environmental parameters that might explain the depth-related patterns we have observed, as currently data are only available for shallow water (10–15 m) environments (see Powell et al ., 2014; Marlow et al ., 2018). Importantly, there has been discussion in the literature about the potential for shallow water coral reefs to transition to reefs dominated by other groups of organisms including sponges and soft coral (Bell et al ., 2013), and understanding the ecology of these deeper water reefs could provide insights into how altered shallow water reefs might function since they are already dominated by these groups.…”
Section: Discussionmentioning
confidence: 99%
“…Fig. 1.Map of the Wakatobi Marine National Park, Indonesia, and location of two sites where the mesophotic reefs were sampled (adapted from Marlow et al ., 2018). …”
Mesophotic 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.
“…Further research is needed to determine how these reefs function, how they differ from shallow water reefs, and if they are able to support shallower water communities, for example through larval subsides. There is also a need to quantify the importance of environmental parameters that might explain the depth-related patterns we have observed, as currently data are only available for shallow water (10–15 m) environments (see Powell et al ., 2014; Marlow et al ., 2018). Importantly, there has been discussion in the literature about the potential for shallow water coral reefs to transition to reefs dominated by other groups of organisms including sponges and soft coral (Bell et al ., 2013), and understanding the ecology of these deeper water reefs could provide insights into how altered shallow water reefs might function since they are already dominated by these groups.…”
Section: Discussionmentioning
confidence: 99%
“…Fig. 1.Map of the Wakatobi Marine National Park, Indonesia, and location of two sites where the mesophotic reefs were sampled (adapted from Marlow et al ., 2018). …”
Mesophotic 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 proliferation of macroalgae on many degraded reefs has not just been attributed to increased substrate availability, but also reduced herbivory (overfishing/disease) and eutrophication (Hughes, 1994; Pandolfi et al ., 2005). In the Wakatobi, in the absence of large rivers and agriculture, chlorophyll a concentration is low (Marlow et al ., 2019) and eutrophication is not considered to be a problem. Conversely, local fishing pressure appears to exceed the maximum sustainable yield and the widespread use of unselective fish fences (Exton, 2010) is likely to be negatively affecting the local herbivorous fish population.…”
Section: Discussionmentioning
confidence: 99%
“…Surveys across the Wakatobi took place in July 2014 at 10 sites chosen to represent a variety of reef types and varying degrees of exposure to human activity (Figure 1; Appendix 1): Wangi, a turbid and sedimented reef within the harbour at Wangi-Wangi Island; Karang Gurita, a coral atoll located between Wangi and Kaledupa Islands; Buoy 3 and Ridge 1, steep-walled sites on the Hoga fringing reef; Pak Kasims, a sloping site on the Hoga fringing reef; Kaledupa 1 and Kaledupa Double Spur, two gentle sloping sites on the Kaledupa fringing reef; Sampela 1, on the Kalepupa fringing reef and adjacent to a Bajo village, considered to be highly degraded, sedimented and turbid (Bell & Smith, 2004; McMellor & Smith, 2010; Powell et al ., 2014); Tomia 1 and Tomia 2, gentle sloping sites on the Tomia fringing reef. While short-term environmental data are available for some of these sites (see Powell et al ., 2014; Biggerstaff et al ., 2015; Marlow et al ., 2019) including Sampela, B3 and Pak Kasims, we do not have environmental data from all sites. Fig.…”
Coral 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.
“…Importantly, numerous studies have described the influence of local‐scale environmental factors on sponge abundance and assemblage composition (e.g. Bell & Barnes, 2000 a ; Powell et al ., 2014; Marlow et al ., 2019). Variability in sponge assemblages at small spatial scales resulting from local‐scale environmental conditions was not captured by our analysis.…”
Section: Global Variation In Sponge Traitsmentioning
Sponges are a major component of benthic ecosystems across the world and fulfil a number of important functional roles. However, despite their importance, there have been few attempts to compare sponge assemblage structure and ecological functions across large spatial scales. In this review, we examine commonalities and differences between shallow water (<100 m) sponges at bioregional (15 bioregions) and macroregional (tropical, Mediterranean, temperate, and polar) scales, to provide a more comprehensive understanding of sponge ecology. Patterns of sponge abundance (based on density and area occupied) were highly variable, with an average benthic cover between ~1 and 30%. Sponges were generally found to occupy more space (percentage cover) in the Mediterranean and polar macroregions, compared to temperate and tropical macroregions, although sponge densities (sponges m–2) were highest in temperate bioregions. Mean species richness standardised by sampling area was similar across all bioregions, except for a few locations that supported very high small‐scale biodiversity concentrations. Encrusting growth forms were generally the dominant sponge morphology, with the exception of the Tropical West Atlantic, where upright forms dominated. Annelids and Arthropods were the most commonly reported macrofauna associated with sponges across bioregions. With respect to reproduction, there were no patterns in gametic development (hermaphroditism versus gonochorism), although temperate, tropical, and polar macroregions had an increasingly higher percentage of viviparous species, respectively, with viviparity being the sole gamete development mechanism reported for polar sponges to date. Seasonal reproductive timing was the most common in all bioregions, but continuous timing was more common in the Mediterranean and tropical bioregions compared to polar and temperate bioregions. We found little variation across bioregions in larval size, and the dominant larval type across the globe was parenchymella. No pattens among bioregions were found in the limited information available for standardised respiration and pumping rates. Many organisms were found to predate sponges, with the abundance of sponge predators being higher in tropical systems. While there is some evidence to support a higher overall proportion of phototrophic species in the Tropical Austalian bioregion compared to the Western Atlantic, both also have large numbers of heterotrophic species. Sponges are important spatial competitors across all bioregions, most commonly being reported to interact with anthozoans and algae. Even though the available information was limited for many bioregions, our analyses demonstrate some differences in sponge traits and functions among bioregions, and among macroregions. However, we also identified similarities in sponge assemblage structure and function at global scales, likely reflecting a combination of regional‐ and local‐scale biological and physical processes affecting sponge assemblages, along with common ancestry. Fi...
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