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Graph showing fitted line plot of live coral cover versus algal cover across sample sites 

Graph showing fitted line plot of live coral cover versus algal cover across sample sites 

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The sea urchin Diadema setosum is often encountered in the coral reefs in the Southern Islands of Singapore. While sea urchins have been known to play a role in regulating algal communities and influencing coral recruitment in other parts of the world, their role in Singapore reefs has not been determined. This study was conducted to determine the...

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... scatter plot between coral cover and algal cover (Fig. 7) showed a significant negative liner relationship between algal cover and live coral ...
Context 2
... a significant negative linear relationship was observed between algal cover and live coral cover (Table 2, Fig. 7), indicating that algal cover plays a role in influencing live coral cover in Singapore ...

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Citations

... While diadematoids are largely recognized as omnivores, they mainly feed by grazing on algae scraped from hard substrates (Bronstein and Loya, 2014;Muthiga and McClanahan, 2020). Consequently, Diadema spp., like other members of this family, are potent 'environmental engineers', capable of altering the structure and composition of entire benthic communities (Hernańdez et al., 2008;Ling et al., 2009;Bronstein and Loya, 2014;Goh and Lim, 2015). As algal growth regulators, Diadema grazing restricts algae proliferation, thereby supporting the settlement and development of slower growing benthic organismssuch as corals (Lawrence, 1975;Sammarco, 1982;Bronstein and Loya, 2014;do Hung Dang et al., 2020). ...
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... Tatsuya, Miyuki & Akira (2016), also 73 reported that grazing and high densities of D. setosum control algal coverage and density on the 74 seaweed bed ecosystems along the central coast of Japan. However, in Singapore reefs, D. 75 setosum is not an important component of the herbivore guild (Goh & Lim, 2015). Seasonal 76 changes have also been reported in the size of the gut of some sea urchins related to changes in 77 food availability (Lawrence, Lawrence & Watts, 2013), there were no changes in D. setosum in ...
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Sea urchins are keystone herbivores that greatly influence primary productivity, algal abundance and scleractinian coral recruitment. The long-spined black sea urchin Diadema setosum is widespread and abundant in reef flats throughout the Philippines. Prior studies regarding the feeding preference of D. setosum have been conducted overseas, but little is known about the impact of the echinoid herbivory on reef flat communities in the Philippines . Feeding preferences of D. setosum on four common marine plant species, Halimeda macroloba , Ceratodictyon spongiosum, Padina sp., and Enhalus acoroides were investigated at the University of the Philippines Visayas Marine Biological Laboratory, located in Taklong Island National Marine Reserve (TINMR), Guimaras. Two food choice experiments were conducted; choice feeding and no-choice feeding. The outcome of choice feeding experiments, expressed as consumption (in g) and percent consumption (%), were used to determine its feeding preferences. The two most preferred feeds determined were then used in no-choice feeding experiment to measure its consumption rate (g⸱echinoid ⁻¹ ⸱hr ⁻¹ ). Results of the choice feeding experiment show that D. setosum significantly prefers C. spongiosum (4.83 ± 2.56 g consumption or 32.2%) and H. macroloba (3.73 ± 2.27 g or 24.8%), and avoids E. acoroides (only 0.17 ± 0.22 g or 1.13%) (F= 5.423, p < 0.05). The no-choice feeding experiment between preferred feeds show H. macroloba was consumed more (0.22 ± 0.16 g⸱echinoid ⁻¹ ⸱hr ⁻¹ ) than C. spongiosum (0.15 ± 0.05 g⸱echinoid ⁻¹ ⸱hr ⁻¹ ) although there was no significant difference (p > 0.05) in consumption rate. Results of the no-choice feeding experiment may have been affected by poor water quality and are considered inconclusive. Nevertheless, the study supports the ecological role of D. setosum as an important herbivore that regulates certain macroalgal species in TINMR through its grazing activities.
... Larvae were pooled together, cleaned with 0.2 µm filtered seawater (FSW), and kept in aerated tanks prior to experiments. Six locally abundant macroalgal species (Lee et al., 2009;Goh and Lim, 2015) were collected from Kusu and maintained in aquaria 2-3 days prior to experiments. The algal species collected were Bryopsis pennata var. ...
... Individuals of Sargassum sp. and Bryopsis sp. were used for this experiment as these algae are locally abundant and have been shown to reduce post-settlement survivorship in previous studies (Lee et al., 2012;Goh and Lim, 2015). The study was conducted on the fringing reef crest and flat of Sister's Island where Sargassum sp. and Bryopsis sp. were relatively abundant on the reef crest and flat, respectively (≥10 individuals per site). ...
... Larvae were pooled together, cleaned with 0.2 µm filtered seawater (FSW), and kept in aerated tanks prior to experiments. Six locally abundant macroalgal species (Lee et al., 2009;Goh and Lim, 2015) were collected from Kusu and maintained in aquaria 2-3 days prior to experiments. The algal species collected were Bryopsis pennata var. ...
... Individuals of Sargassum sp. and Bryopsis sp. were used for this experiment as these algae are locally abundant and have been shown to reduce post-settlement survivorship in previous studies (Lee et al., 2012;Goh and Lim, 2015). The study was conducted on the fringing reef crest and flat of Sister's Island where Sargassum sp. and Bryopsis sp. were relatively abundant on the reef crest and flat, respectively (≥10 individuals per site). ...
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Scleractinian corals are vulnerable to a range of environmental disturbances, but generally suffer the highest rates of mortality during early life-history stages, i.e., from larval settlement until a few months post-settlement. Variations in survival rates of corals during this period play a key role in structuring adult coral populations. Many coral reefs have experienced reductions in herbivory rates due to overfishing and consequent increases in macroalgae, however, the effect of increased coral-algal interactions may vary between coral life-history stages and among locations. Therefore understanding the relative importance of different drivers of mortality across early life-history stages, under a range of environmental conditions, is essential to effectively manage and restore coral reefs. To date, however, relatively few studies have (a) examined coral-algal interactions across several early life-history stages (i.e., from planulae to juvenile colonies) and (b) done so in highly disturbed reefs close to large urban centers. We investigated the effect of algal-coral-herbivore interactions on early life history stages in the coral Pocillopora acuta on coral reefs off mainland Singapore, a heavily disturbed “urbanized reef environment”. Larval settlement rates were estimated in the presence of six macroalgal species ex situ. The effect of direct interaction with two macroalgal species on newly settled spat was examined in situ and the effect of reduced herbivory was tested with exclusion cages on naturally settled 9-month-old juveniles in situ. We found significant reductions in P. acuta settlement in the presence of four macroalgal species. Newly settled spat of P. acuta had significantly lower survivorship when in contact with Sargassum sp. on the reef crest but not with Bryopsis sp. on the reef flat. Herbivore exclusion reduced survivorship of juvenile corals, which was associated with increased sediment accumulation, but not with algal biomass. Our results suggest coral recruitment on heavily disturbed reefs can be impacted by species-specific macroalgal effects via reduced settlement on ephemeral substrata and reduced survivorship when in direct contact with Sargassum sp. Furthermore, recruitment may be negatively impacted by reductions in herbivory, possibly via increased abundance of epilithic algal matrix leading to sediment trapping.
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Urchins are ubiquitous components of coral reefs ecosystems, with significant roles in bioerosion and herbivory. By controlling urchin densities, triggerfishes have been identified as keystone predators. However, the functional linkages between urchins and triggerfishes, in terms of distributional patterns and concomitant effects on ecosystem processes, are not well understood, especially in relatively unexploited systems. To address this we censused urchins and triggerfishes on two cross-shelf surveys on the Great Barrier Reef (GBR) at the same times and locations. We also evaluated the role of urchins in bioerosion. Although urchin abundance and triggerfish biomass varied by 80% and nearly 900% across sites, respectively, this variability was driven primarily by shelf position with no evidence of top-down control on urchins by triggerfishes. Low urchin abundances meant urchins only played a minor role in bioerosion. We highlight the potential variability in functional links, and contributions to ecosystem processes, among regions.
... For instance, Huang et al. (2009) observed 161 species in 2006-2007, a level of diversity on par with surveys at more remote locations within the surrounding region (Harborne et al., 2000;Affendi et al., 2005;Huang et al., 2015). Macroalgal competitors of coral include the genera Bryopsis and Sargassum (Lee et al., 2012) but cover on the reef crest is generally low at ≤20% (Guest et al., 2016), though this varies considerably between sites, as well as in relation to abundances of the urchin, Diadema setosum (Goh and Lim, 2015). Guest et al. (2016) found no evidence of phase shifts between coral and macroalgal dominated states over time. ...
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Given predicted increases in urbanization in tropical and subtropical regions, understanding the processes shaping urban coral reefs may be essential for anticipating future conservation challenges. We used a case study approach to identify unifying patterns of urban coral reefs and clarify the effects of urbanization on hard coral assemblages. Data were compiled from 11 cities throughout East and Southeast Asia, with particular focus on Singapore, Jakarta, Hong Kong, and Naha (Okinawa). Our review highlights several key characteristics of urban coral reefs, including “reef compression” (a decline in bathymetric range with increasing turbidity and decreasing water clarity over time and relative to shore), dominance by domed coral growth forms and low reef complexity, variable city-specific inshore-offshore gradients, early declines in coral cover with recent fluctuating periods of acute impacts and rapid recovery, and colonization of urban infrastructure by hard corals. We present hypotheses for urban reef community dynamics and discuss potential of ecological engineering for corals in urban areas.