Interactions among freshwater macrophytes and physical-chemical-biological processes in Lake Chini, Malaysia

[Truncated abstract] Aquatic vascular plants that grow within the littoral and pelagic environment are an important element of shallow lake and wetland ecosystems. Alteration of the natural environment, mostly human-induced, is rapidly changing the natural ecological processes and altering biotic factors including aquatic plant community composition in wetlands all over the world. This thesis examined the macrophyte communities in Lake Chini, a shallow floodplain wetland in Malaysia: specifically how physical-chemical and biological processes were related to plant community dynamics and changes of macrophyte dominance, from the native floating-leaved species (Nelumbo nucifera) to non-native submerged macrophytes (Cabomba furcata). Whole-lake vegetation surveys and statistical models were used to analyse spatially and temporally the macrophyte community composition and the environmental variables that influence their structure. The lake can be divided into distinct quasi-independent sub-basins. Temperature and dissolved oxygen measurements were conducted in benthic chambers and free water at two separate sub-basins and mathematical calculations were employed to describe (1) the influence of convective circulation, driven by horizontal temperature gradient and thermal structure on the nutrient transport in the system, and (2) oxygen dynamics and differences in primary production among habitat and macrophyte communities. Overall, this study found that the macrophyte community in Lake Chini is highly dynamic with possible alternate states dominated by floating-leaved and submerged species. The flood regime has a strong effect in controlling the variation in plant community dominance. Spatial variation in plant community composition was influenced by total depth, nutrient concentration and substrate.