Aquatic macroinvertebrates of Nee Soon 
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Discussion 
The Nee Soon freshwater swamp forest is a vital refuge for the biodiversity of 
Singapore, due to the large number of species which can be found nowhere else in 
Singapore (Clews et al., 2018; Davison et al., 2018). Furthermore, some species are 
endemic to the Nee Soon freshwater swamp forest and found nowhere else in the 
world (Ng & Lim, 1992; Cumberlidge et al., 2009; Lim et al., 2011). These species 
would likely be extirpated from Singapore or rendered globally extinct, should their 
habitat be damaged or severely altered. In order to conserve Singapore’s native 
biodiversity, there is a need to understand the diversity and distribution of the aquatic 
macroinvertebrates in the Nee Soon freshwater swamp forest and develop a baseline 
dataset. Additionally, further studies can be built on this baseline dataset to inform 
policy makers and aid in the conservation efforts of the Nee Soon freshwater swamp 
forest. 
The results of this study suggest that the conservation of the Nee Soon 
freshwater swamp forest is pivotal in protecting the rich aquatic macroinvertebrate 
biodiversity found there. Surveys during this study yielded a higher number of aquatic 
macroinvertebrate taxonomic groups (76 families and six higher taxa) as compared 
to the number of macroinvertebrate taxonomic groups (68 families and 6 higher taxa) 
collected across 47 urban concrete canals and natural forest streams within the Central 
Catchment Nature Reserve (Blakely et al., 2014). Moreover, only 66% of the taxa (54 
out of 82 taxonomic groups) in this study are reported in the study by Blakely et al 
(2014). This means that the aquatic biodiversity in Nee Soon freshwater swamp forest 
consists of a large number of rare taxa (e.g. Psephenidae or water-penny beetle and the 
Xiphocentronidae caddisfhes) that are not found in other habitats within Singapore. 
This further highlights the need to prioritise the conservation and the protection of the 
natural resources within the Nee Soon drainage. 
The results of this study demonstrate variations in the distribution of 
macroinvertebrate groups within the forest streams with different communities 
represented in different parts of the forest. These communities reflect heterogeneous 
environmental conditions across the catchment. Some taxa, including both mollusc 
classes and the crustacean class Ostracoda, are confined to only the northeast area of 
the Nee Soon drainage. Common taxa, such as the Diptera and the Ephemeroptera, 
are also found in extremely large numbers in this area and in reduced numbers deeper 
inside (further upstream) the Nee Soon drainage. The northeast area of the catchment 
receives additional input of less acidic water from an adjacent reservoir. The decreased 
acidity here is more suitable for some of the mollusc taxa, since molluscs are sensitive 
to low pH levels due to the corrosive effects on their shells (Clements et al., 2006; 
Gazeau et al., 2013; Parker et al., 2013). 
In addition to the less acidic conditions in the northeast area of the Nee Soon 
drainage, the streams are more open and lacking canopy cover, unlike the densely 
forested streams deeper within the freshwater swamp forest. Macroinvertebrate 
groups such as Plecoptera, Megaloptera and some of the Ephemeroptera (Family 
Heptageniidae and Leptophlebiidae) were absent in these less-forested areas. 
