Carbon cycling on intertidal mudflats of the Kaomei Wetland

• Main Authors: Li- Hua Lee, 李麗華
• Other Authors: 林幸助
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/84068527695178653537

博士 === 國立中興大學 === 生命科學系所 === 101 === In situ benthic community production and respiration during emersion were measured monthly in the course of a 19 mo survey from June 2008 to December 2009 by monitoring CO2 fluxes in benthic chambers on intertidal sandflats of a subtropical coastal wetland. Both maximum gross community production (GCPm) and community respiration (CR) all show higher values in summer and fall and lower values in spring and winter. GCPm and CR were positively correlated with air temperature. GCPm was also positively correlated with sediment grain size and negatively correlated with the silt/clay content. CR exhibited a strong positive correlation with sediment chlorophyll a concentration and macrofaunal biomass. To provide an accurate annual budget of benthic production during emersion, corrections were considered for cloudiness and the time lag between emersion and maximum production due to vertical migration of benthic diatoms and variations in CR during nighttime emersion periods. Annual net community production (NCP) during emersion on sandflats was estimated to be 2.87 g C m−2 yr−1, indicating an autotrophic system. However, taking into account the variation in benthic metabolism during immersion, the subtropical intertidal sandflats shifted to a heterotrophic system, and annual NCP was calculated to be −91.47 g C m−2 yr−1. Effects of an oil spill on subtropical benthic community production and respiration were documented by monitoring CO2 fluxes in benthic chambers on intertidal sandflats of a coastal wetland before and after an accidental oil spill. The oil spill decreased sediment chlorophyll a concentrations and the community composition, and also affected ecological functioning by suppressing microalgal production, increasing bacterial respiration, and causing a shift from an autotrophic system to a heterotrophic system. Effects of the oil spill were more severe on the macrofauna than on benthic microalgae and more severe on small-sized, sedentary infauna than on large-sized, motile epifauna. Despite these effects on the benthic community and carbon metabolism, the affected area recovered in about 23 days. To qunatify the total carbon flux of Kaomei wetland, the carbon flux of water was monitored. There were obvious differences in the concentration of POC and DOC of water between seasons and sampling sites. The main factors affected the carbon content and the changes of carbon flux were chlorophyll a concentration, DO and turbidity of sea water. The carbon influx amount was larger than outflux, the carbon in the water of Kaomei Wetland came from sea water, and its net OC influx was 9.1 metric ton yr-1, indicating a carbon sink system.