Joel Ng Xuan Hao

Supervisors: Dr. Darren Yeo Chong Jinn & Dr. Chris Baker (University of Queensland)

Project: Removal of a non-native freshwater shrimp (Macrobrachium nipponense) from a tropical freshwater stream: effectiveness and impacts on ecosystem functioning

The non-native shrimp, Macrobrachium nipponense, is widely established in Singapore reservoirs, which are largely dominated by non-native fauna. The species has spread to rural streams along the edges of nature reserves, posing a possible competitive threat to native shrimp species that dwell in forest streams within the reserves and these transitory forest edge habitats. Removal of the non-native species to control or slow its establishment is a possible management response, but the effectiveness as well as impacts of removal of the established non-native species in the transitory habitat are unclear. Thus, the project aims to investigate the effectiveness of removal at slowing the spread of Macrobrachium nipponense through regular removal and population assessment. Additionally, the impact of such removal on stream ecosystem functioning will be determined through the monitoring of leaf litter breakdown and macroinvertebrate assemblages in in-situ microcosms. Results will demonstrate the viability of removal.

Joshua Tan Lin Jie

Supervisors: Dr. Darren Yeo Chong Jinn

Project: Responses of fish functional traits along an anthropogenic disturbance gradient in Singapore freshwater streams

Tropical fresh waters in Southeast Asia have exceptionally high biodiversity but are at the same time, are undergoing rapid and extensive habitat modification. This situation has motivated investigations into the effects of anthropogenic disturbances on freshwater diversity—many of which use fishes as research models due to their size, abundance and ease of sampling. While the observation of freshwater community responses is a common approach to study changes in freshwater diversity, the findings are often specific to the context and species identities investigated. Functional traits —attributes of an organism contributing to its ecological role— on the other hand are generalisable beyond locally-specific species identities, allowing for more widely applicable findings. Therefore, this study aims to investigate how functional traits in fishes of Singapore’s freshwater streams respond to an anthropogenic disturbance gradient. To do this, I will first obtain environmental data, fish community data and functional trait data in selected sites spanning an anthropogenic disturbance gradient. Ordination techniques will be used to summarise multivariate environmental data representing the disturbance gradient. Generalised regression will then be applied to relate functional trait responses to this gradient. Through this, I aim to achieve a generalised understanding that can be applied to other threatened freshwater ecosystems.

Mia Sara Choo

Supervisors: Dr. Darren Yeo Chong Jinn

Project: Investigation of the influence of riparian vegetation species on leaf litter macroinvertebrate community

Riparian vegetation regulates natural stream processes by providing nutrient/energy inputs into freshwater streams. Leaf litter from riparian vegetation serves as a food source and/or substrate for macroinvertebrates, thereby influencing the overall faunal assemblage of streams. While past studies in temperate regions have observed that leaf litter breakdown rates and macroinvertebrate community differ for single- and mixed-species leaf litter, little research has been done on this particularly in the tropics. Fundamental differences between tropical streams and temperate streams also mean that the effects of leaf litter diversity on breakdown and macroinvertebrate community may differ. Thus, this project aims to quantify the effects of riparian species composition and diversity (through leaf litter diversity and composition) on the leaf litter macroinvertebrate community within the forest streams of Singapore, and study how this pattern varies over time. The results from this study will help better predict and understand the effects of changes in riparian vegetation on the functioning of the stream ecosystem, as well as provide insight on riparian management in stream habitats.

M Pooventhran

Supervisor: Dr. Darren Yeo Chong Jinn

Project: Investigating the autecology of the marbled gudgeon, Oxyeleotris marmorata, in Singapore fresh waters

The marbled gudgeon, Oxyeleotris marmorata, is a benthopelagic ambush predator that feeds primarily of freshwater prawns, small fish, and other benthic organisms. A native of brackish waters in Singapore and the surrounding Southeast Asian region, the species has been introduced to inland waters in Singapore and is now established in many reservoirs. This large ambush predator has been observed to have spread from reservoirs into forest streams, and has the potential to impact the native communities within these streams. To determine and better understand the potential impact that O. marmorata may have on forest stream communities, an understanding on its autecology (i.e., trophic role, diet, life history) is required. Therefore, this study aims to compare the autecology of O. marmorata found in streams and reservoirs by examining the diet, trophic ecology, population structure as well as abiotic differences between lentic and lotic sites in relation to differences in O. marmorata autecology. Findings from such efforts will shed light on the possible impact that O. marmorata may have on stream communities if they were to establish themselves and increase in numbers. This will enable the development conservation strategies especially those related to native stream species in the future.