Trophic dynamics and energy flow in freshwater wetland ecosystems

Abstract

On earth Freshwater wetlands are highly productive ecosystems and also provide complex trophic interactions as well as efficient energy transfer pathways. This study will aim at assessing the trophic processes and energy dynamics within freshwater wetlands ecosystems and more specifically the role of primary producers, consumers and decomposers in ensuring that the ecosystem is productive and stable. This analysis draws on a literature review and trophic modeling and trophic level analysis of the wetland biotic communities; macrophytes, phytoplankton, zooplankton, macroinvertebrates, fish, amphibians, and microbial decomposers. The conceptual trophic models and quantitative estimates of primary productivity, decomposition rates, and transfer efficiency of trophic models were used to study the energy transfer pathways. Other drivers of the environment like hydrology, nutrient supply, and light intensity were also analyzed to have insight into how it affect energy allocation in the ecosystem. It is established by the analysis that Primary producers contribute 60–65% of gross primary production (GPP), forming the base of the wetland food web. Grazing pathways produce about 60–90% of the energy flow whereas the detritus-based pathways produce about 10–40% of the energy flow underlining the preponderance of organic matter decomposition in the wetlands. The degradation rates of litter averaged at 3.0–3.5 g m⁻² day⁻¹, indicating high rate of recycling of nutrients and high activity of microorganisms. Nevertheless, there was an efficiency of 8–12% trophic transfer across trophic levels with some deviation of the classical ecological efficiency rule with the complexity of structure of wetlands and the composition of lignocellulosic wetlands. Nutrient pollution, hydrological changes and the presence of invasive species in the ecosystem were also cited as anthropogenic stressors that were able to decrease the efficiency of energy transfer and destabilize trophic cascades. The general implications of the study are that balanced relationships between grazing and detrital processes are required to sustain the productivity of wetlands and ecological resilience, so there is a need to have sustainable management and conservation strategies of the wetlands.