海南新村湾海草床沉积物影响有机碳转化的主要酶活性特征及其对营养负荷的响应

本文以海南新村湾海草床生态系统为研究对象，根据环境中营养负荷梯度设置3条断面，探讨表层沉积物中影响有机碳（SOC）转化的主要酶活性的空间分布特征及其对营养负荷的响应。结果表明:SOC含量随营养盐含量上升而增加，二者呈现显著正相关（p<0.05），沉积物多酚氧化酶、过氧化物酶、蔗糖酶和纤维素酶活性范围分别为0.10~0.24 mg/g/2 h、0.14~0.73 mg/g/2 h、0.24~0.69 mg/g/24 h和0.03~0.36 mg/g/72 h，平均值分别为0.17 mg/g/2 h、0.36 mg/g/2 h、0.43 mg/g/24 h和0.19 mg/g/72 h。在同一断面，泰来藻（Thalassia hemprichii）沉积物酶活性大多高于海菖蒲（Enhalus acoroides）；与其它类型滨海湿地比较，热带海草床中这4种酶的活性较低。根据与环境中营养盐浓度的相关性分析，这4种酶活性大多呈现随着营养负荷的增加而逐渐上升。因此，营养负荷增加可能会提高海草床表层沉积物的酶活性，加快其SOC的转化速率，改变海草床生态系统中碳的生物地球化学循环，可能会弱化海草床沉积物的碳存储，影响其重要的蓝碳功能。

Characteristics of key enzyme activities influencing sediment organic carbon transformation and their response to the nutrient loading in seagrass bed of Xincun bay,Hainan Island

To examine the spatial distribution of key enzyme activities influencing sediment organic carbon (SOC) transformation in surface sediment and their response to nutrient enrichment in seagrass bed in Xincun bay,Hainan Island,three transects were carried out according to different nutrient loading.The content ranges of polyphenol oxidase,peroxidase,invertase and cellulas were 0.10~0.24 mg/g/2 h,0.14~0.73 mg/g/2 h,0.24~0.69 mg/g/24 h and 0.03~0.36 mg/g/72 h,respectively,with the average content as 0.17 mg/g/2 h、0.36 mg/g/2 h、0.43 mg/g/24 h and 0.19 mg/g/72 h,respectively.Enzyme activities in surface sediment beneath Thalassia hemprichii were generally higher than that of Enhalus acoroides in the same transect.In general,enzyme activities in our investigating locations were lower than other coastal wetlands.Moreover,these enzyme activities showed an increasing trend with increasing nutrient loading.Therefore,increasing nutrient load was probably favorable for stimulating seagrass surface sediment enzyme activities and accelerating SOC transformation rate,which might change carbon biogeochemical cycle in particular seagrass bed ecosystem.Further eutrophication might weaken seagrass beds sediment carbon storage,and thus influence the "blue carbon" function.