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Complex Object
Interactions among freshwater macrophyte Interactions among freshwater macrophyte... - Complex Object ()
Interactions among freshwater macrophytes and physical-chemical-biological processes in Lake Chini, Malaysia / Zati Sharip
[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.
C. furcata appears adapted to annual floods, and its invasion affected the diversity and plant community composition in this wetland. Additionally, both floating-leav and submerged vegetation contributed to thermal structure and water exchange dynamics in the system. Weak density-driven flow was induced by the differential temperature gradient between the open water and the littoral areas dominated by floating-leaved plants. Additionally, depth variation between the near littoral zone and the open pelagic region induced physical circulation that could improve nutrient delivery to the submerged C. furcata bed. In addition to the effects of the macrophyte, lake physical characteristics such as shape and surrounding topography influenced the variation of thermal stratification and mixing dynamics between the lake segments at different water levels. Oxygen dynamics differed between the two plant communities. Gross primary production rates and biomass accumulation were higher in C. furcata sites and ecosystem production contributed to increased carbon fixation in the system. High consumption of DO by sediment communities and microflora associated with C. furcata beds increased respiratory activities. An increase in abundance of the invasive submergent C. furcata throughout the pelagic zone affected net ecosystem production and biomass accumulation...
Thesis (Ph.D.)--University of Western Australia, 2011
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