The Anniversary Changes Of Primary Productivity, Fish Diversity And The Assessment Of Carbon Sequestration Capacity Of Phytoplankton In Jiuduansha Wetland

Jiuduansha wetland is located in the south of Yangtze River estuary’s deep channel,its contained South Jiangyasha, Upper Jiuduansha and Middle-Lower Jiuduansha.1. The annual variation of fish diversity in Jiuduansha wetlandJiuduansha wetland is the most representative area of fish in the Yangtze Riverestuary. From2010to2011, Jiuduansha wetland was surveyed seasonally to researchthe species composition and diversity. A total of4,120individuals of42species werecounted in8sites by8times’ surveys,2,280individuals were caught in SouthJiangyasha,998individuals in Middle Jiuduansha and842individuals in LowerJiuduansha. These fishes belonged to10orders in23families, which Pleuronectiformes,Tetraodontiformes and Beloniformes only have one species. The dominant species wereAcanthogobius hasta, Liza carinatus and Liza haematocheila. The advantages ofdominant species were very high, only7species of fish accounted for80%of the totalnumber of samples. In this paper, three indexes of diversity components （D, H’, J’） werecalculated to explain the spatial and temporal differences of fish diversity. The diversityindex of spring was the highest （2.067）, and winter （1.372） was the lowest; LowerJiuduansha （2.18）> South Jiangyasha （2.159）> Middle Jiuduansha （1.322）.2. The anniversary change of primary productivity and estimate of the annualcarbon sequestration in Jiuduansha wetlandPrimary productivity means the rate of autotrophs manufacturing organics throughphotosynthesis or chemical synthesis. It includes gross primary productivity and netprimary productivity. The former refers to total organic carbon produced by autotrophsand the latter is the amount that the gross primary productivity deducted the respirationby autotrophs in the determination stage.This paper was the research for differences and trends of gross primary productivity in different seasons and regions of Jiuduansha wetland. And estimate thetotal organic carbon fixed by autotrophs （phytoplankton） through the analysis the resultsof primary productivity. Aimed at evaluate of the contribution to the wetland ecosystemcarbon cycle by phytoplankton in Jiuduansha wetland. Provide theoretical guidance anddecision-making basis for optimize the management measures and further enhance thecarbon sink function of Jiuduansha Wetland Nature Reserve.（1）Annual variation of the primary productivity of Jiuduansha wetlandAccording to the survey analysis of seawater transparency, salinity, dissolvedoxygen and chlorophyll concentrations in Jiuduansha wetland from December2010toOctober2011, we explore the relationship between the change of environmental factorsand primary productivity under different climate conditions. The average annualprimary productivity of South Jiangyasha, Upper Jiuduansha, Middle Jiuduansha andLower Jiuduansha were in the range of87.75⁷44.79mgC·m^-3·d. The primaryproductivity of Lower Jiuduansha was strongest and the South Jiangyasha was theweakest. This may be because South Jiangyasha belongs to the riverside freshwaterwetlands, more organic matters were input with the tides, leading to strong respiration.There are large differences between each season. In four seasons, spring have thehighest average primary productivity (528.13mgC·m^-3·d) because the environmentalfactors such as water temperature, transparency and solar irradiance were more suitablefor phytoplankton’s photosynthesis. At the same time, due to the high sedimentconcentration made autumn have the lowest average primary productivity (137.11mgC·m^-3·d). The average annual primary productivity was276.55mgC·m^-3·d inJiuduansha wetland.（2）Assessment of carbon sequestration capacity by phytoplankton in JiuduanshawetlandAccording to the result of the primary productivity, we estimated annual carbonsequestration of phytoplankton in Jiuduansha wetland was about61,852tons. Thecarbon sequestration in South Jiangyasha, Upper Jiuduansha, Middle Jiuduansha andLower Jiuduansha were from81.173gC·m^-3to126.562gC·m^-3. The carbonsequestration ability of Lower Jiuduansha was stronger than others, and the carbonsequestration ability of South Jiangyasha was the weakest. But the overall difference isless pronounced. The phytoplankton solid carbon amount in four seasons were spring (48.591gC·m^-3)> winter (31.681gC·m^-3)> summer (17.130gC·m^-3)> autumn(6.993gC·m^-3) respectively. The seasonal variation was consistent with primaryproductivity. Combined with water volume, we calculated carbon sequestration eachseason: spring （28,790tons）> winter （18,770tons）> summer （10,150tons）> autumn（4,142tons）. The result show that the higher primary productivity, the stronger carbonsequestration ability. According to the annual plankton, fish resources data and theirindividual carbon content, we estimate that only103.9tons of carbon stored in vivo,equivalent to1,172.6tons of CO2. Visible, the amount of organic carbon fixed byphytoplankton photosynthesis were greatly reduced after food chain.