Brandon Lam

Goh Xin Ni, Candice

Supervisor: Assoc. Professor Darren Yeo Chong Jinn & Dr. Maxine Allayne Darlene Mowe

Project: Examining the limiting nutrients of phytoplankton between protected and unprotected reservoirs in Singapore via ex-situ incubation experiments

Reservoirs are an important source of potable water supply in Singapore. However, harmful freshwater phytoplankton blooms have been known to occur in Singapore’s reservoirs, such as Kranji reservoir, and may threaten the safety and quality of Singapore’s water sources. Cyanobacteria, a major constituent of phytoplankton, can produce harmful toxins in freshwater. In addition to toxins, the secondary non-toxic products produced by cyanobacteria, such as geosmin, may affect the taste and smell of drinking water. Algal blooms can be the result of an increase in the limiting nutrients, such as nitrogen (N), phosphorus (P), or both, available to phytoplankton communities, causing their rapid proliferation. In general, nutrient limitation in tropical freshwater bodies is less understood compared to those in temperate regions as there are comparatively fewer studies. This project involves conducting ex-situ N and P nutrient addition bioassays to observe responses in the growth dynamics of phytoplankton from different protected and unprotected reservoirs. The phytoplankton compositional biovolume and chlorophyll a concentration of each assay containing reservoir water will be recorded before and after nutrient addition for comparison as an indicator of phytoplankton biomass and community response. Corresponding water chemistry will also be analysed to measure the total N, total P, nitrate (NO₃^–), ammonium (NH₄⁺) and phosphate (PO₄^3-) levels present in each reservoir. These will be compared with the N and P levels in the bioassays to determine nutrient availability in the reservoir. Having a better understanding of the N or P limiting status of Singapore reservoirs and the potential differences between protected and unprotected reservoirs will be invaluable in the management and prevention of harmful phytoplankton blooms in the tropics.

Lim Wan Teng

Supervisor: Assoc. Professor Darren Yeo Chong Jinn & Dr. Ng Ting Hui

Project: The ecology of freshwater molluscs and the effects of non-native Pomacea apple snails on local freshwater gastropod communities in Singapore.

Freshwater molluscs in Singapore are poorly studied despite their ecological importance and diversity. The only comprehensive study that investigated the diversity patterns and habitat attributes of local primary freshwater molluscs was conducted 20 years ago. However, changes during the intervening years in the taxonomic status would mean that information of the diversity patterns of freshwater molluscs is no longer accurate, and this could alter our understanding of the molluscan communities. Therefore, an updated study is timely and would provide the baseline information that could aid future research and inform freshwater biodiversity conservation efforts. This study thus aims to provide updated baseline information on the distribution of freshwater molluscs found locally and their general habitat affinities. In addition, the opportunity will be taken to also investigate the effects of the presence of the widespread introduced freshwater apple snails of the genus Pomacea on local gastropod communities. Given their well-documented invasive potential and negative ecological impacts on malacofauna elsewhere, knowledge on the effects of Pomacea species on local malacofauna can provide more information on the impacts of its introduction and aid in management efforts of this invasive species

Tan Zhi Wan

Supervisor: Assoc. Professor Darren Yeo Chong Jinn & Dr. Jose Christopher Escano Mendoza

Project: Indochinese Freshwater Crab Taxonomy

Freshwater crabs (Crustacea: Decapoda: Brachyura) are one of the most conspicuous and dominant benthic invertebrates that are present in almost all freshwater environments ranging from fast-flowing hill streams and waterfalls to sluggish swamps and rice fields. True freshwater crabs refer to those that are adapted to living in freshwater, semi-terrestrial or terrestrial environments, and are importantly characterized by their fully freshwater life cycle with no larvae stages that require saline conditions. Of the estimated 1430 species of freshwater crabs in the world, the vast majority are located within the Oriental region which comprises India, South China and Southeast Asia with more than 900 species in 154 genera and two families formally described. In particular, the region known as Indochina which comprises Myanmar, Thailand, Laos, Cambodia and Vietnam, represents a hotspot for freshwater crab diversity, where the family Potamidae is particularly well represented. More recently, the number of Indochinese freshwater crab species has grown considerably as a result of increased attention to the revisionary taxonomic studies in this region. However, it is also known that Indochinese potamids are more diverse than previously understood and still requires more work to resolve and revise the crabs of this family. Thus, this project aims to revise the Potamidae crabs of Thailand and provide formal descriptions of several undescribed species using morphological traits.

Zhong Kaiyun

Supervisor: Assoc. Professor Darren Yeo Chong Jinn

Project: Investigating the invasive potential of aquarium Procambarus clarkii in tropical freshwater systems through comparison against Cherax quadricarinatus using pH.

With global warming and climate change exacerbating alterations of abiotic and biotic parameters of ecosystems, the potential of non-native introduction through various pathways has been heightened. In Singapore, the ornamental trade is one such pathway to local freshwater systems which are particularly susceptible to negative impacts incited by invasive species, housing vulnerable native species that may be functionally equivalent. Cherax quadricarinatus and Procambarus clarkii are two freshwater crayfish species particularly popular in the aquarium trade, with the former already established in our streams. However, while studies have been done concerning parameters such as temperature, no direct comparison between the two species of interest in terms of pH yet exists. Therefore, this study aims to address this paucity by finding out the impact of varying pH levels on these invasive crayfish species, and use functional response experiments to determine their invasive potential and consequent impacts in Singapore’s freshwater ecosystems.

Shermaine Teo Huimin

Supervisors: Assoc. Professor Darren Yeo Chong Jinn

Project: Investigating the population structure and condition factor of the Singapore Freshwater Crab, Johora singaporensis.

Johora singaporensis is an endemic potamid of freshwater crab in Singapore which has been classified as “critically endangered” by the International Union for Conservation of Nature (IUCN). The species is restricted to only a few streams in Singapore due to relatively specialized habitat preferences coupled with rarity and disruptions of its preferred unique habitat. Hence, understanding the demographics of Johora singaporensis across space and time, as well as the potential effects of endogenous and exogenous variables on their condition factor can aid in informing conservation management of the species. This project aims to: 1) monitor spatial and temporal trends in the population size and structure of the crabs, 2) explore and compare the condition factors of the crab across streams and seasons and 3) investigating how the aforementioned differences in condition factor might be affected by abiotic habitat factors.

Sim Li Xuan, Vera

Supervisors: Assoc. Professor Darren Yeo Chong Jinn & Dr. Kwik Teik Beng Jeffrey

Project Title: Investigating macrophyte-associated fish and macroinvertebrate communities in Lower Seletar Reservoir. Aquatic plants, known as macrophytes, occur naturally in several reservoirs in Singapore. These mostly sun-loving, non-native species thrive in open, urban/artificial habitats (as opposed to the shade-loving, native species found in Singapore’s natural forest stream and freshwater swamp habitats). Non-native macrophytes have nevertheless been applied in various urban freshwater sites given their many functions in freshwater ecosystems, including nutrient sequestration and habitat/microhabitat provision for aquatic fauna. Existing literature indicate that macrophytes support diverse and abundant associated faunal communities, and are therefore important for enhancing aquatic biodiversity. Macrophyte-associated faunal communities, however, are not well-studied in Singapore. The present study aims to address this gap by describing and comparing, both quantitatively and qualitatively, macrophyte communities along with the associated fish and macroinvertebrate diversity within Lower Seletar Reservoir, which were investigated previously in 2015. As there are plans to conduct biomanipulation trials in this reservoir, an updated baseline is required. Apart from providing an updated overall baseline inventory of the macrophyte-associated faunal communities in this reservoir, this study will also include intra-reservoir comparisons of abiotic and biotic parameters at cross-sectional (i.e. spatial) levels between different parts of the reservoir as well as longitudinal (i.e. temporal) levels against previous studies. Through an in-depth characterisation of Lower Seletar Reservoir, this study may provide insights on patterns of spatio-temporal variations in macrophyte-associated faunal communities. Key abiotic parameters (e.g. Secchi depth, temperature, pH, and dissolved oxygen) will be measured, while macrophytes and their associated faunal communities will be surveyed with various methods, such as netting and trapping.