Bryna Liang Jia Ying

Main supervisor: Dr. Maxine Allayne Darlene Mowe            

Co-supervisor: A/P Darren Yeo Chong Jinn

Project: The diversity and distribution of aquatic heteropterans in Singapore

Water bugs include the infraorders Leptopodomorpha, Gerromorpha and Nepomorpha, and make up a significant proportion of the world’s aquatic insect diversity. These insects are ecologically important owing to their ability to occupy diverse aquatic habitats and adapt to various associated niches. Although documentation of Singapore’s aquatic bugs has been done extensively during the 1960s till early 2010s, the aquatic heteropteran in Singapore has not been surveyed or well-studied in the recent decade. In addition, the water bug diversity in streams at rural and urban areas in Singapore has not been documented despite several species of water bugs becoming very rare or even extinct as a result of changes in Singapore’s water drainage system. Thus, to better understand how urbanisation may affect the freshwater stream aquatic insect community, the diversity and distribution of aquatic heteropterans in Singapore across forest, rural and urban streams will be studied.

Sim Li Xuan, Vera

Supervisor: A/P Darren Yeo Chong Jinn

Project: A global meta-analysis of functional diversity and redundancy in lentic freshwater fish assemblages

Freshwater fishes contribute significantly to ecosystem functioning (e.g., food web regulation, nutrient cycling) in lentic waterbodies, but are at risk of extinction as a result of anthropogenic impacts. The effect of decline in fish diversity on their contributions to ecosystem functioning can be assessed through measures of functional diversity and redundancy—which determine also the robustness of the aquatic food webs. While there has been an increasing number of localised studies on the functional diversity and redundancy of freshwater fish assemblages, few have examined large-scale patterns in functional ecology of freshwater fishes (e.g., in tropical versus temperate regions, natural versus man-made habitats), and how it relates to food web robustness. The present study aims therefore to 1) characterise functional diversity and redundancy of freshwater fish assemblages in lentic waterbodies using a global meta-analysis, and 2) assess the extent of influence of functional diversity and redundancy on food web robustness of such assemblages by simulating scenarios of species removal.

 Soh Bryan

Main supervisor: A/P Darren Yeo Chong Jinn

Project: Trophic ecology of decapod crustaceans in Nee Soon Swamp Forest

Nee Soon Swamp Forest (NSSF), Singapore’s only freshwater swamp, harbours a high proportion of stenotopic freshwater decapod crustaceans found only in its acidic waters, including the endemic and globally critically endangered freshwater swamp crab, Parathelphusa reticulata. Despite their prominence and relatively high diversity in NSSF, the role that decapods play in the trophic/food web of NSSF remains unstudied. This information will be crucial to the conservation of the species as the new knowledge may give insights into the prey-predator relationship of key organisms in NSSF. Therefore, this study aims to characterise and compare the trophic ecology of decapods in NSSF through Stable Isotope Analysis; to deduce the relative trophic positions of decapods in NSSF and how these trophic positions vary across sites within NSSF.

Teo Xue Shen 

Main supervisor: A/P Darren Yeo Chong Jinn

Co-supervisor: Dr. Maxine Allayne Darlene Mowe

Project: Comparison of microplastics in gut content of two freshwater fish species (Geophagus altifrons and Cichla orinocensis) from Singapore reservoirs

In recent years, concerns have been raised over the presence of a new source of aquatic pollutant: microplastics. Microplastics are plastic particles below five millimeters in size with no lower limit. Most microplastics originate from land-based sources, with freshwater systems forming pathways by which they enter the marine environment. Yet research on microplastics have largely been focused on the marine environment. In countries like Norway and China, microplastics have been observed to aggregate in reservoirs. A similar phenomenon could take place in Singapore’s urban reservoirs and these microplastics may pose a threat to the reservoir’s food web via consumption and bioaccumulation. Due to their size, microplastics are increasingly bioavailable to small organisms, paving their intrusion into food webs. Fish may ingest microplastics directly through mistaken identity as prey, or indirectly via consumption of contaminated prey. Ingestion of microplastics by fish may result in starvation, internal physical damage and physiological damage such as immune system interference.

In Singapore, due to extensive development and land use change, many reservoirs’ surroundings and the areas they drain are highly urbanized. Previous research has revealed the presence of microplastics in the sediment and waters of various waterways; to date, the extent to which microplastics have infiltrated the gastrointestinal tracts of freshwater fish in Singapore’s reservoirs has not been quantified. This study aims to quantify microplastics occurrence in the gastrointestinal tract of the eartheater cichlid(Geophagus altifrons) and the Orinoco peacock bass (Cichla orinocensis) at Serangoon and Lower Seletar reservoirs. Geophagus altifrons and Cichla orinocensis are important links in the reservoirs’ food webs. Geophagus altifrons is a primarily insectivorous benthic feeder while Cichla orinocensis is a pelagic piscivorous predator. Both of these are also prey for other wildlife such as otters, monitor lizards and various birds of prey. The outcomes of this study would contribute to the monitoring of microplastic risk in Singapore’s reservoirs and will be the first to quantify microplastic consumption in freshwater fish in Singapore. This could provide a baseline for further research into microplastics as a potential threat to other wildlife and inform wildlife conservation decisions.

Chan Yee Qi

Main supervisor: A/P Darren Yeo Chong Jinn

Project Title: A baseline study of population structure and sexual dimorphism in Irmengardia johnsoni (Crustacea: Brachyura: Gercarcinucidae)

Johnson’s freshwater crab (Irmengardia johnsoni) is one of Singapore’s three endemic freshwater crab species and has been observed to display heterochely among adult males. Little else, however, is known about the biology of the species. Given its important ecological role, significance as an endemic species, and vulnerable IUCN status, there is therefore a need for basic biological information to inform the conservation of I. johnsoni. As such, this study aims to collect baseline data on I. johnsoni population structure in two stream sites within Nee Soon Swamp Forest and Bukit Timah Nature Reserve known to have high I. johnsoni population densities. This will establish a baseline reference for long-term monitoring of the species which would help to inform future conservation measures. In addition, patterns in heterochely and handedness among I. johnsoni males will also be examined, providing a case study among freshwater crabs which would inform future studies that elucidate the ecological significance of this phenomenon.

Ivan Neo

Main supervisor: A/P Darren Yeo Chong Jinn

Co-supervisor: Dr. Tan Ming Kai

Project Title: Behavioural study on the aquatic adaptations of the pygmy grasshopper (Orthoptera: Tetrigidae) from freshwater swamp forest

Orthopterans (grasshoppers, crickets, and katydids) are generally fully terrestrial species, though some have been known to be adapted and associated with aquatic environments. One such orthopteran are the pygmy grasshoppers (Tetrigidae), known to be able to stay submerged for extended periods of time by utilizing an extended thorax structure (pronotum) to trap an air bubble. Literature on such adaptations of pygmy grasshoppers is scarce regionally, hence little is known about the behaviour and morphological adaptations of local species in Singapore. This knowledge gap hinders the understanding of climate change resistance and conservation of pygmy grasshoppers, as they prefer wet microhabitats and are sensitive to environmental changes. This makes them potential bio-indicators of changes in freshwater swamp forest. This study therefore seeks to fill this knowledge gap.

In the context of climate change, excess rainfall may cause pygmy grasshoppers to be inundated by floods. On the other hand, droughts may cause them to seek microhabitats nearer to the main streams where it is moist. In both scenarios, aquatic adaptation is an advantageous trait, where irregular weather patterns caused by climate change may pressure an ecologically sensitive and valuable area like Nee Soon Swamp Forest (NSSF). NSSF is thus selected as a study site due to the prevalence of Tetrigidae, abundance of wet micro-habitats and ecological value/sensitivity of the area. This study will help understand how morphological features (like the pronotum) aid the pygmy grasshoppers to live a semi–aquatic lifestyle through controlled behavioural study, looking at possible implications of floods/droughts (driven by climate change) on the individuals.

Lim Yang Jin, Stanley

Main supervisor: Dr. Maxine Allayne Darlene Mowe

Co-supervisor: A/P Darren Yeo Chong Jinn

Project Title: Examining phytoplankton community responses to nutrient limitation with a focus on the effects of trace metals on Microcystis ichthyoblabe and Microcystis viridis growth and toxin production

Phytoplankton are microscopic organisms that can photosynthesise and constitute the base of food webs in Singapore’s reservoirs. However, some groups can produce toxins that negatively affect water quality. Many are also capable of blooming which could damage ecosystems. Macro-nutrients such as phosphorous and nitrogen are some nutrients that allow for such blooms to occur. Trace metals such as Iron, Manganese, Cobalt and Zinc are also important for many cellular functions. However, the effects of macronutrients on phytoplankton communities are understudied in the tropics. In addition, the effects of trace metals on growth and toxin production are less understood. This project aims to investigate differences in the phytoplankton community responses between protected and unprotected reservoirs through ex-situ nutrient-addition bioassay experiments and the observation of cell counts and biovolume data. More specifically, this study will also experimentally investigate the effects of trace metals on the growth and toxin production of cyanobacteria strains isolated from local reservoirs.