Accurate evaluation of target organisms is fundamental to quantify responses to disturbances, elu... more Accurate evaluation of target organisms is fundamental to quantify responses to disturbances, elucidate thresholds and strengthen effective management. Threats to seagrasses in Singapore are excessive nutrients and sedimentation, leading to an evaluation of descriptor utility to detect plant response to nutrient and light availability usingThalassia hemprichiias the model species. A combination of popularly used seagrass physio-morphological descriptors and epibiont biomass were measured to assess plant response to environmental quality. Results showed convincing support for the use of leaf pigments as indicators of light availability and salinity changes. Water column nitrification and phosphorus availability had strong effects on leaf nutrient content, leaf morphology and epibiont biomass. Relationships between leaf length and light contradicted expected patterns, where shorter leaves were associated with lowered light. This may be attributable to hydrodynamic or sedimentation reg...
This study estimates the maximum and minimum degrees of autocompaction for radiocarbon-dated Holo... more This study estimates the maximum and minimum degrees of autocompaction for radiocarbon-dated Holocene mangrove sediments in Singapore, in order to correct apparent sediment accretion rates for the effects of sediment compression due to autocompaction. Relationships developed for a suite of modern (surface) sediment samples between bulk density, particle-size distribution, and organic matter content were used to estimate the initial (uncompacted) bulk density of buried and variably compressed Holocene sediments, based on the grain-size distribution and organic matter content of the sediment. The difference between measured (compacted) and initial (uncompacted) bulk density of each buried sediment interval can be interpreted as the amount of length shortening experienced by each interval since burial. This allows the elevation of samples selected for 14C dating to be corrected for the effects of autocompaction of the underlying sediment sequence, so that accurate estimates of vertical...
Ecotoxicology is concerned with the effects of environmental toxicants on the health of organisms... more Ecotoxicology is concerned with the effects of environmental toxicants on the health of organisms living in the natural environment. Environmental toxicants are agents released into the general environment that may cause adverse effects on health. The study of environmental toxicology stems from the recognition that: (a) Human survival depends on the availability of clean air, water, and food and on the welfare of plants and animals and; (b) Anthropogenic and naturally occurring chemicals can cause adverse effects on living organisms and ecological processes. Environmental toxicology is a multidisciplinary science that encompasses several diverse areas of study that focuses on how environmental toxicants, through their interaction with humans, animals, and plants, influence the health and welfare of organisms. Related areas include biology; chemistry (inorganic, organic and analytical chemistry); anatomy; genetics; physiology; ecology; soil and water. Over the decades, the concept o...
Vulnerability of coastal areas to sea level rise is driven not only by global environmental chang... more Vulnerability of coastal areas to sea level rise is driven not only by global environmental changes but likewise by socio-economic development and the ability of affected communities to cope with such changes. As such we endeavored to achieve an integrated analysis of the effect of the complex and dynamic social, economic and environmental factors found in the region to the vulnerability of human communities, and their implications for management and governance of coastal systems and adaptation capacities.
The sea urchin Diadema setosum is often encountered in the coral reefs in the Southern Islands ... more 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 distribution and abundance of sea urchins in Singapore reefs, to examine algal cover, algal biomass, algal species and live coral cover, and to determine any interactions between urchin density and algal communities that may impact coral cover. Several reefs in Singapore were surveyed using belt transects measuring 20 m by 2 m, laid down on the reef crest. Abundance of urchins, algal species, biomass, and live coral cover were determined by the use of quadrats within each belt transect. This study revealed an increasing abundance of the sea urchin Diadema setosum in reefs progressing southwards away from mainland Singapore with low density of urchins occurring in Sisters' Island, St John's Island, Pulau Tekukor, and Kusu Island, and the highest density observed at Raffles Lighthouse. A significant negative linear relationship between algal cover and live coral cover (P < 0.05) was established. The results of this study indicate that sea urchins may not be an important component of the herbivore guild in Singapore.
Contemporary Trends and Issues in Science Education, 2001
The cover photograph shows participants of the workshop in an activity-based learning session on ... more The cover photograph shows participants of the workshop in an activity-based learning session on the use of conceptual diagrams in communicating science.
Studies concerning subtidal octocoral species from Singapore reefs are few. This study document... more Studies concerning subtidal octocoral species from Singapore reefs are few. This study documents the diversity and abundance of octocoral communities from fringing reefs at Singapore's Southern Islands, namely, Pulau Semakau, P. Hantu and Kusu Island. Belt transects of 20 m ( 5) were employed to survey the octocoral communities at these reef sites. Morphology and sclerites of a number of collected octocoral samples were compared with paratypes obtained from the Raffles Museum of Biodiversity Research, National University of Singapore, for species identification. A total of 16 morphotypes, belonging to five octocoral genera, including Cladiella, Lobophytum, Nephthea, Sarcophyton and Sinularia, were identified in this study. Statistical analysis revealed octocoral abundance and diversity at Kusu Island reefs were higher than those around P. Hantu and P. Semakau. Conversely, octocoral community structures encountered along P. Semakau and Kusu Island were more similar than those of P. Hantu. The preliminary data presented in this study could serve as the baseline data for long term biomonitoring programs in assessing the state of coral reefs in Singapore.
Studies concerning subtidal octocoral species from Singapore reefs are few. This study document... more Studies concerning subtidal octocoral species from Singapore reefs are few. This study documents the diversity and abundance of octocoral communities from fringing reefs at Singapore's Southern Islands, namely, Pulau Semakau, P. Hantu and Kusu Island. Belt transects of 20 m ( 5) were employed to survey the octocoral communities at these reef sites. Morphology and sclerites of a number of collected octocoral samples were compared with paratypes obtained from the Raffles Museum of Biodiversity Research, National University of Singapore, for species identification. A total of 16 morphotypes, belonging to five octocoral genera, including Cladiella, Lobophytum, Nephthea, Sarcophyton and Sinularia, were identified in this study. Statistical analysis revealed octocoral abundance and diversity at Kusu Island reefs were higher than those around P. Hantu and P. Semakau. Conversely, octocoral community structures encountered along P. Semakau and Kusu Island were more similar than those of P. Hantu. The preliminary data presented in this study could serve as the baseline data for long term biomonitoring programs in assessing the state of coral reefs in Singapore.
Aedes (Stegomyia) aegypti (Linnaeus) and Ae. (Stegomyia) albopictus (Skuse) were sampled from fiv... more Aedes (Stegomyia) aegypti (Linnaeus) and Ae. (Stegomyia) albopictus (Skuse) were sampled from five regions of Singapore (Central, North East, North West, South East and South West) and tested with diagnostic concentrations of the technical grade insecticides, pirimiphos-methyl and cypermethrin. Biochemical assays were performed on the same populations of Ae. aegypti and Ae. albopictus to determine activities of detoxifying enzymes, including non-specific esterase (EST), monooxygenase (MFO) and acetylcholinesterase (AChE). The diagnostic test showed that all Ae. aegypti populations were susceptible to pirimiphos-methyl (mortality = 99 to 100%), but resistant to cypermethrin (mortality = 11 to 76%). Resistance to pirimiphos-methyl was observed in all Ae. albopictus populations (mortality = 49 to 74%) while cypermethrin resistance was detected in most Ae. albopictus populations (mortality = 40 to 75%), except those from Central (mortality = 86%) and South East (mortality = 94%) showing...
ABSTRACT Abstracts of 2nd UNU-ORI joint international workshop for marine environment 第2回海洋環境国際ワー... more ABSTRACT Abstracts of 2nd UNU-ORI joint international workshop for marine environment 第2回海洋環境国際ワークショップ講演要旨
ABSTRACT Abstracts of 3rd UNU-ORI joint international workshop for marine environment 海洋環境国際ワークショ... more ABSTRACT Abstracts of 3rd UNU-ORI joint international workshop for marine environment 海洋環境国際ワークショップ講演要旨
Nutrient enrichment of nearshore waters has been extensively implicated in the global decline of ... more Nutrient enrichment of nearshore waters has been extensively implicated in the global decline of seagrass populations. Ex-situ manipulative experiments are invaluable in studying mechanisms and direct effects of elevated nutrients on seagrasses, but may underestimate the importance of indirect consequences of enrichment and need to be corroborated in the fi eld. However, conducting in-situ experiments are notoriously diffi cult with real-world variability in conditions easily confounding attempted treatments. This paper presents the results of an in-situ pilot study conducted at St John's Island (also known as Pulau Sakijang Bendera), Singapore, to investigate experimental conditions that can properly examine the impacts of elevated water column nutrients on intertidal populations of a seagrass Thalassia hemprichii (Ehrenb. ex Solms) Asch. (Hydrocharitaceae). Plants were experimentally exposed to two sources of nitrogen (NH 4 and NO 3 ) and phosphate (PO 4 ) added into the water column over a three-month period. In addition, an assessment to evaluate suitable physiological and morphological response variables of T. hemprichii were made, and the effects of potential competitors such as epibionts (biomass) and phytoplankton (measured by chlorophyll a) on their well-being. Nutrient levels over the study period were highly variable within treatments, with measured concentrations in control plots exceeding intended dosing regimes. Increases in nitrate and nitrite concentrations were evident at enriched plots, but these were inconsistent within and among treatments, suggesting large variability in hydraulics. Some evidence of enrichment effects on plants exposed to nutrient treatments were observed, from reduced leaf C:P, enhanced leaf total chlorophyll concentrations, lowered leaf chlorophyll a/b ratios, and increased leaf length and area. However, these responses were mostly not statistically signifi cant as the high variation observed potentially reduced the power of statistical tests. The results are discussed in the context of improvements to the experimental setup. This study highlighted the importance of pilot studies in planning manipulative in-situ studies to minimise high natural variation. A more robust design would provide clearer quantitative information on the impact of anthropogenic nutrient enrichment on local seagrasses.
Benthic macroalgae generally dominate on degraded and disturbed coral reefs. However, little is k... more Benthic macroalgae generally dominate on degraded and disturbed coral reefs. However, little is known about the interactions between benthic macroalgae and coral larvae on tropical reefs. The present study examined the effects of macroalgal species on the settlement success of Pocillopora damicornis larvae under aquarium conditions. Coral larvae were exposed to locally common macroalgal species Bryopsis corymbosa, Halimeda opuntia, Sargassum sp. and Padina minor. The presence of B. corymbosa, Sargassum sp. and H. opuntia had signifi cant negative effects on larval settlement, while that of P. minor had no signifi cant effect. Coral polyp "bail-out" from skeletons was also observed in the experimental tanks containing macroalgae. These results suggest that the presence of some benthic macroalgal species could inhibit coral settlement.
Previous studies have shown marine bivalves to be suitable bioindicators for heavy metal pollutio... more Previous studies have shown marine bivalves to be suitable bioindicators for heavy metal pollution in the marine environment. In this study, the potential of the Green Mussel, Perna viridis to be a bioindicator of copper and cadmium contamination in the marine environment was explored. The study aimed to develop a toxicity bioassay using P. viridis, and explored if a dose-response relationship between fertilisation in P. viridis and increasing concentrations of copper and cadmium could be established. The effect of copper and cadmium on embryo formation was also examined. Few fertilisation assays involve the use of the P. viridis, a tropical marine bivalve. Rather, a temperate mussel Mytilus sp., is more commonly used. As such, this study is relevant to the Southeast Asian region. Mussel gametes were subjected to increasing concentrations of cadmium and copper over a 24h test period. Following this, the number of unfertilised eggs was counted under a microscope. Data obtained was then arcsine transformed and subjected to one way Analysis of Variance (ANOVA) and Dunnett's test to determine if a significant dose-response curve could be established. Results indicated significant treatment effects and a degeneration of unfertilised eggs when gametes were subjected to cadmium and copper solutions.
Accurate evaluation of target organisms is fundamental to quantify responses to disturbances, elu... more Accurate evaluation of target organisms is fundamental to quantify responses to disturbances, elucidate thresholds and strengthen effective management. Threats to seagrasses in Singapore are excessive nutrients and sedimentation, leading to an evaluation of descriptor utility to detect plant response to nutrient and light availability usingThalassia hemprichiias the model species. A combination of popularly used seagrass physio-morphological descriptors and epibiont biomass were measured to assess plant response to environmental quality. Results showed convincing support for the use of leaf pigments as indicators of light availability and salinity changes. Water column nitrification and phosphorus availability had strong effects on leaf nutrient content, leaf morphology and epibiont biomass. Relationships between leaf length and light contradicted expected patterns, where shorter leaves were associated with lowered light. This may be attributable to hydrodynamic or sedimentation reg...
This study estimates the maximum and minimum degrees of autocompaction for radiocarbon-dated Holo... more This study estimates the maximum and minimum degrees of autocompaction for radiocarbon-dated Holocene mangrove sediments in Singapore, in order to correct apparent sediment accretion rates for the effects of sediment compression due to autocompaction. Relationships developed for a suite of modern (surface) sediment samples between bulk density, particle-size distribution, and organic matter content were used to estimate the initial (uncompacted) bulk density of buried and variably compressed Holocene sediments, based on the grain-size distribution and organic matter content of the sediment. The difference between measured (compacted) and initial (uncompacted) bulk density of each buried sediment interval can be interpreted as the amount of length shortening experienced by each interval since burial. This allows the elevation of samples selected for 14C dating to be corrected for the effects of autocompaction of the underlying sediment sequence, so that accurate estimates of vertical...
Ecotoxicology is concerned with the effects of environmental toxicants on the health of organisms... more Ecotoxicology is concerned with the effects of environmental toxicants on the health of organisms living in the natural environment. Environmental toxicants are agents released into the general environment that may cause adverse effects on health. The study of environmental toxicology stems from the recognition that: (a) Human survival depends on the availability of clean air, water, and food and on the welfare of plants and animals and; (b) Anthropogenic and naturally occurring chemicals can cause adverse effects on living organisms and ecological processes. Environmental toxicology is a multidisciplinary science that encompasses several diverse areas of study that focuses on how environmental toxicants, through their interaction with humans, animals, and plants, influence the health and welfare of organisms. Related areas include biology; chemistry (inorganic, organic and analytical chemistry); anatomy; genetics; physiology; ecology; soil and water. Over the decades, the concept o...
Vulnerability of coastal areas to sea level rise is driven not only by global environmental chang... more Vulnerability of coastal areas to sea level rise is driven not only by global environmental changes but likewise by socio-economic development and the ability of affected communities to cope with such changes. As such we endeavored to achieve an integrated analysis of the effect of the complex and dynamic social, economic and environmental factors found in the region to the vulnerability of human communities, and their implications for management and governance of coastal systems and adaptation capacities.
The sea urchin Diadema setosum is often encountered in the coral reefs in the Southern Islands ... more 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 distribution and abundance of sea urchins in Singapore reefs, to examine algal cover, algal biomass, algal species and live coral cover, and to determine any interactions between urchin density and algal communities that may impact coral cover. Several reefs in Singapore were surveyed using belt transects measuring 20 m by 2 m, laid down on the reef crest. Abundance of urchins, algal species, biomass, and live coral cover were determined by the use of quadrats within each belt transect. This study revealed an increasing abundance of the sea urchin Diadema setosum in reefs progressing southwards away from mainland Singapore with low density of urchins occurring in Sisters' Island, St John's Island, Pulau Tekukor, and Kusu Island, and the highest density observed at Raffles Lighthouse. A significant negative linear relationship between algal cover and live coral cover (P < 0.05) was established. The results of this study indicate that sea urchins may not be an important component of the herbivore guild in Singapore.
Contemporary Trends and Issues in Science Education, 2001
The cover photograph shows participants of the workshop in an activity-based learning session on ... more The cover photograph shows participants of the workshop in an activity-based learning session on the use of conceptual diagrams in communicating science.
Studies concerning subtidal octocoral species from Singapore reefs are few. This study document... more Studies concerning subtidal octocoral species from Singapore reefs are few. This study documents the diversity and abundance of octocoral communities from fringing reefs at Singapore's Southern Islands, namely, Pulau Semakau, P. Hantu and Kusu Island. Belt transects of 20 m ( 5) were employed to survey the octocoral communities at these reef sites. Morphology and sclerites of a number of collected octocoral samples were compared with paratypes obtained from the Raffles Museum of Biodiversity Research, National University of Singapore, for species identification. A total of 16 morphotypes, belonging to five octocoral genera, including Cladiella, Lobophytum, Nephthea, Sarcophyton and Sinularia, were identified in this study. Statistical analysis revealed octocoral abundance and diversity at Kusu Island reefs were higher than those around P. Hantu and P. Semakau. Conversely, octocoral community structures encountered along P. Semakau and Kusu Island were more similar than those of P. Hantu. The preliminary data presented in this study could serve as the baseline data for long term biomonitoring programs in assessing the state of coral reefs in Singapore.
Studies concerning subtidal octocoral species from Singapore reefs are few. This study document... more Studies concerning subtidal octocoral species from Singapore reefs are few. This study documents the diversity and abundance of octocoral communities from fringing reefs at Singapore's Southern Islands, namely, Pulau Semakau, P. Hantu and Kusu Island. Belt transects of 20 m ( 5) were employed to survey the octocoral communities at these reef sites. Morphology and sclerites of a number of collected octocoral samples were compared with paratypes obtained from the Raffles Museum of Biodiversity Research, National University of Singapore, for species identification. A total of 16 morphotypes, belonging to five octocoral genera, including Cladiella, Lobophytum, Nephthea, Sarcophyton and Sinularia, were identified in this study. Statistical analysis revealed octocoral abundance and diversity at Kusu Island reefs were higher than those around P. Hantu and P. Semakau. Conversely, octocoral community structures encountered along P. Semakau and Kusu Island were more similar than those of P. Hantu. The preliminary data presented in this study could serve as the baseline data for long term biomonitoring programs in assessing the state of coral reefs in Singapore.
Aedes (Stegomyia) aegypti (Linnaeus) and Ae. (Stegomyia) albopictus (Skuse) were sampled from fiv... more Aedes (Stegomyia) aegypti (Linnaeus) and Ae. (Stegomyia) albopictus (Skuse) were sampled from five regions of Singapore (Central, North East, North West, South East and South West) and tested with diagnostic concentrations of the technical grade insecticides, pirimiphos-methyl and cypermethrin. Biochemical assays were performed on the same populations of Ae. aegypti and Ae. albopictus to determine activities of detoxifying enzymes, including non-specific esterase (EST), monooxygenase (MFO) and acetylcholinesterase (AChE). The diagnostic test showed that all Ae. aegypti populations were susceptible to pirimiphos-methyl (mortality = 99 to 100%), but resistant to cypermethrin (mortality = 11 to 76%). Resistance to pirimiphos-methyl was observed in all Ae. albopictus populations (mortality = 49 to 74%) while cypermethrin resistance was detected in most Ae. albopictus populations (mortality = 40 to 75%), except those from Central (mortality = 86%) and South East (mortality = 94%) showing...
ABSTRACT Abstracts of 2nd UNU-ORI joint international workshop for marine environment 第2回海洋環境国際ワー... more ABSTRACT Abstracts of 2nd UNU-ORI joint international workshop for marine environment 第2回海洋環境国際ワークショップ講演要旨
ABSTRACT Abstracts of 3rd UNU-ORI joint international workshop for marine environment 海洋環境国際ワークショ... more ABSTRACT Abstracts of 3rd UNU-ORI joint international workshop for marine environment 海洋環境国際ワークショップ講演要旨
Nutrient enrichment of nearshore waters has been extensively implicated in the global decline of ... more Nutrient enrichment of nearshore waters has been extensively implicated in the global decline of seagrass populations. Ex-situ manipulative experiments are invaluable in studying mechanisms and direct effects of elevated nutrients on seagrasses, but may underestimate the importance of indirect consequences of enrichment and need to be corroborated in the fi eld. However, conducting in-situ experiments are notoriously diffi cult with real-world variability in conditions easily confounding attempted treatments. This paper presents the results of an in-situ pilot study conducted at St John's Island (also known as Pulau Sakijang Bendera), Singapore, to investigate experimental conditions that can properly examine the impacts of elevated water column nutrients on intertidal populations of a seagrass Thalassia hemprichii (Ehrenb. ex Solms) Asch. (Hydrocharitaceae). Plants were experimentally exposed to two sources of nitrogen (NH 4 and NO 3 ) and phosphate (PO 4 ) added into the water column over a three-month period. In addition, an assessment to evaluate suitable physiological and morphological response variables of T. hemprichii were made, and the effects of potential competitors such as epibionts (biomass) and phytoplankton (measured by chlorophyll a) on their well-being. Nutrient levels over the study period were highly variable within treatments, with measured concentrations in control plots exceeding intended dosing regimes. Increases in nitrate and nitrite concentrations were evident at enriched plots, but these were inconsistent within and among treatments, suggesting large variability in hydraulics. Some evidence of enrichment effects on plants exposed to nutrient treatments were observed, from reduced leaf C:P, enhanced leaf total chlorophyll concentrations, lowered leaf chlorophyll a/b ratios, and increased leaf length and area. However, these responses were mostly not statistically signifi cant as the high variation observed potentially reduced the power of statistical tests. The results are discussed in the context of improvements to the experimental setup. This study highlighted the importance of pilot studies in planning manipulative in-situ studies to minimise high natural variation. A more robust design would provide clearer quantitative information on the impact of anthropogenic nutrient enrichment on local seagrasses.
Benthic macroalgae generally dominate on degraded and disturbed coral reefs. However, little is k... more Benthic macroalgae generally dominate on degraded and disturbed coral reefs. However, little is known about the interactions between benthic macroalgae and coral larvae on tropical reefs. The present study examined the effects of macroalgal species on the settlement success of Pocillopora damicornis larvae under aquarium conditions. Coral larvae were exposed to locally common macroalgal species Bryopsis corymbosa, Halimeda opuntia, Sargassum sp. and Padina minor. The presence of B. corymbosa, Sargassum sp. and H. opuntia had signifi cant negative effects on larval settlement, while that of P. minor had no signifi cant effect. Coral polyp "bail-out" from skeletons was also observed in the experimental tanks containing macroalgae. These results suggest that the presence of some benthic macroalgal species could inhibit coral settlement.
Previous studies have shown marine bivalves to be suitable bioindicators for heavy metal pollutio... more Previous studies have shown marine bivalves to be suitable bioindicators for heavy metal pollution in the marine environment. In this study, the potential of the Green Mussel, Perna viridis to be a bioindicator of copper and cadmium contamination in the marine environment was explored. The study aimed to develop a toxicity bioassay using P. viridis, and explored if a dose-response relationship between fertilisation in P. viridis and increasing concentrations of copper and cadmium could be established. The effect of copper and cadmium on embryo formation was also examined. Few fertilisation assays involve the use of the P. viridis, a tropical marine bivalve. Rather, a temperate mussel Mytilus sp., is more commonly used. As such, this study is relevant to the Southeast Asian region. Mussel gametes were subjected to increasing concentrations of cadmium and copper over a 24h test period. Following this, the number of unfertilised eggs was counted under a microscope. Data obtained was then arcsine transformed and subjected to one way Analysis of Variance (ANOVA) and Dunnett's test to determine if a significant dose-response curve could be established. Results indicated significant treatment effects and a degeneration of unfertilised eggs when gametes were subjected to cadmium and copper solutions.
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