摘要 : The dynamics of seston fluxes has been associated with phy-toplankton blooms in marine and freshwater systems (Viner-Mozzini et al. 2003). The fate of these blooms is crucial to the understanding of carbon flow, nutrient cycling a... 展开 The dynamics of seston fluxes has been associated with phy-toplankton blooms in marine and freshwater systems (Viner-Mozzini et al. 2003). The fate of these blooms is crucial to the understanding of carbon flow, nutrient cycling and ecosystem functions. As a consequence, it is important to unravel the mechanisms of particle sedimentation as well as the quantity and quality of settling particles. Ecosystem processes are important determinants of the biogeochemistry of the ocean that can be profoundly affected by changes in climate (Le Quere et al. 2005). The different routes that the particles take in the aquatic ecosystem (transfer in food-web, respiration, sedimentation, and burial) will define the availability of carbon to organisms and the time of return of carbon molecules in the carbon cycle. The transfer in the food web and its processes are important controls of aquatic bio-genic carbon flux and water-atmosphere carbon dioxide exchange (Legendre 1999). Rapid increases in phytoplank-ton biomass have a high potential for exporting particulate organic matter from the euphotic layer, providing important information for the study of global fluxes of carbon in the inland water systems; however, if a larger fraction of assimilated carbon is respired at low than at high latitudes, a smaller proportion of production can be exported in tropical regions. The explicit inclusion of ecosystem processes in models will permit ecological changes to be taken into account, allow us to understand how the uptake of CO_2 in inland water systems is likely to change in the future, and improve our understanding of the local and regional climate systems.The main losses for bloom biomasses are grazing, decomposition in the mixing layer, and sedimentation to the bottom of lakes (Zohary et al. 1998). The dominant size fraction of phy-toplankton defines the principal transfer path of biogenic carbon in the ecosystem. When the small fraction (<2 μm) dominates, the main route will be nutrient recycling through the microbial loop in the euphotic zone. In contrast, when the large fraction (>2 μm) dominates, new production will either be exported to the bottom of the lake or consumed by herbivores and eventually exported as fecal pellets (Legendre 1999).The aim of this study was to evaluate the vertical and temporal variation of seston fluxes in Lake Alchichica to better understand the carbon dynamics of a tropical, oligotrophic lake where the large size fraction of phytoplankton dominates. 收起