Amanda Hsiung Rouwen

Supervisors: Dr. Darren Yeo Chong Jinn

Project: Comparative functional responses of native and alien Macrobrachium prawns under different environmental conditions

Functional response, a measurement of food consumption against food density, has recently been investigated for its utility as a predictive tool in forecasting relative ecological impacts between native and alien species, in terms of resource utilization. In Singapore, the introduced Oriental river prawn, Macrobrachium nipponense, now thrives in the outskirts of Nee Soon Swamp Forest (NSSF), potentially competing with the Malayan freshwater prawn, Macrobrachium malayanum, a native congener found in the natural forest stream and freshwater swamp habitats of NSSF and other parts of the Central Catchment Nature Reserve. With both prawns being epibenthic scavengers and opportunistic predators, the species that better exploits food resources would be a better competitor. Additionally, functional responses have been documented to change significantly in varying environmental conditions. My objective will be to assess their comparative functional responses under varying temperatures and pH conditions, to attempt to predict the impacts of the M. nipponense.

James Chang Wen Jie

Supervisor: Dr. Darren Yeo Chong Jinn

Project: Distribution and autecology of the non-native ocellate river stingray, Potamotrygon motoro

The South American ocellate river stingray, Potamotrygon motoro, is frequently encountered worldwide in the aquarium trade (a major invasion pathway for ornamental freshwater fishes), yet somewhat surprisingly has not been documented to be established outside of its Neotropical home range—with the exception of a single published record from a reservoir in Singapore in 2007. Despite environmental concerns, public health concerns, and the threat of invasive scenarios, no research has been carried out on these stingrays. Understanding the distribution and autecology of the species is an important first step towards better understanding that can inform potential management efforts. This study aims to investigate the local distribution and autecology of P. motoro in Singapore. Through dietary analyses (gut content analysis and stable isotope analysis), the trophic/community level interactions of this species will be investigated. Additionally, environmental parameters recorded in this study will supplement existing distribution data of this species, which will be used in species distribution modelling, allowing for predictions on potential range expansions of P. motoro in regions outside of its native distribution.

See Shi Min Yvonne

Supervisors: Dr. Darren Yeo Chong Jinn

Project: Investigating the role of refugia in regulation of phytoplankton population by macrophytes using a mesocosm study in Pandan Reservoir Singapore

Macrophytes have been known to impact the freshwater plankton community through both direct and indirect mechanisms. While past studies in temperate regions have observed direct effects of allelopathy and competition by macrophytes on phytoplankton, little research has been done on the effect of macrophytes on the zooplankton community and the resulting indirect cascading effects on the phytoplankton community, particularly in the tropics. Thus, this project aims to investigate these effects through an in-situ experiment at Pandan Reservoir, with a focus on the mechanism of refuge provided by macrophytes for zooplankton, and how it can possibly have an indirect impact on the phytoplankton community. The results of this study will fill the gaps in current knowledge about the topic and potentially provide insight on management of tropical freshwater habitats.

Sia Chang Han

Supervisors: Dr. Darren Yeo Chong Jinn & Dr. Simon Mitrovic (University of Technology, Sydney)

Project: Laboratory and field investigations of the effects of light and nutrients on the growth and toxin production of Microcystis viridis

Eutrophication can induce cyanobacterial blooms in lakes and coastal waters, which may be harmful to aquatic organisms as they can sometimes create hostile hypoxic environments, and may even produce toxins that harm or kill animals. As water security is an important component of Singapore’s continued stability, the factors which influence the growth and toxicity of freshwater cyanobacterial blooms have to be well-understood in order to be managed. One particular cyanobacteria that can be found within Singapore’s reservoirs is Microcystis viridis. Many studies that investigated the effect of nutrient enrichment or light intensity on Microcystis growth and toxicity have been done either ex situ within laboratories, or in situ in lakes and reservoirs. Few studies, however, involve both ex situ and in situ experiments run simultaneously. My study aims to apply different nutrient and light treatments to M. viridis both in the laboratory and on site in Serangoon reservoir concurrently to observe and compare their effects on the growth and toxin production of M. viridis. Through this study, we would be able to evaluate the validity of results obtained in the laboratory as compared to under natural lake/reservoir conditions. By doing so, we may be better equipped in dealing with toxic cyanobacterial blooms that occur within Singapore’s reservoirs in the future.

Yeo Soon Boon Shayne

Supervisor: Dr. Darren Yeo Chong Jinn

Project: Effects of invertivore fish diversity on ecosystem functioning and its stability against environmental stressors

In the highly urbanised Singapore, many natural forest streams are being cleared as forests make way for urban developments. These forest streams are often the last few remaining natural habitats for native forest stream fishes and hence threatened by habitat loss. My study aims to understand how the diversity of local forest stream fishes affects ecosystem functioning (BEF) by looking at functional processes such as feeding and excretion rate. The fishes will be subjected to different diversity treatments based on their feeding guild. Anthropogenic stressors such eutrophication will also be simulated to understand whether diversity affects their tolerance to withstand these stressors. Findings from this study could potentially aid biodiversity conservation efforts and management of the environment. Since a variety of species used in this study are also found in aquarium fish trade, results from this research could also improve aquacultural practices involving these fishes.