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Carbon cycling on intertidal mudflats of the Kaomei Wetland
Lee, Li- Hua
Carbon sink;Gross community production;Community respiration;Net community production;Kaomei Wetland
|Issue Date: ||2013-11-07 13:23:10 (UTC+8)|
|摘要: ||台灣沿岸潮間帶泥沙灘地的底棲碳代謝量從未經測量。本研究從2008年6月至2009年12月，利用罩蓋法實地在退潮後之高美濕地潮間帶進行底棲群聚生產量與呼吸量之量測，藉由監測二氧化碳流量變化來推估全年的底棲微藻碳代謝量。研究結果顯示，底棲最高總群集生產量(GCPm)、淨群集生產量(NCP)及群集呼吸量(CR)均有明顯的季節變化，夏季高，冬與春季低，與氣溫呈現正相關。底棲代謝亦呈現地點間差異。GCPm與NCP與底質粒徑呈現正相關，但與粉泥黏土含量及底質篩選係數呈現負相關。CR則與底棲微藻葉綠素a含量及底棲動物生物量呈現正相關。在退潮時一整年的NCP為2.87 g C m-2，屬於自營生態系統，但在漲潮時則轉為異營的生態系統，一整年NCP為-91.47g C m-2。|
最後為估算整個高美濕地的碳通量，針對水體進行碳流量的監測。水體中的顆粒有機碳(POC)及溶解有機碳(DOC)濃度在季節與採樣地點之間都有顯著差異變化，POC在秋季清水大排所採樣的值最高，最低值是在秋季漲潮時；DOC最高值是在夏季的灌溉溝渠，最低值是在冬季漲潮時。葉綠素a濃度與POC、顆粒無機碳(PIC)為顯著正相關，與溶解無機碳(DIC)為顯著負相關；溶氧濃度與POC、DOC為顯著正相關，與DIC顯著負相關；海水濁度與DOC、PIC為顯著正相關，與POC顯著負相關。總碳（TC）的入流量大於出流量，因此高美濕地水體的碳是由海水及清水大排輸入的系統，有機碳(OC)淨入流量為9.1 metric ton yr-1，藉由沉積作用將碳留在濕地底土間隙中，形成碳匯。
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.
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