Characteristics of phytoplankton communities and their biomass variation in a gas hydrate drilling area in the northern South China Sea
Characteristics of phytoplankton communities and their biomass variation in a gas hydrate drilling area in the northern South China Sea
复制标题
南海北部天然气水合物钻探区浮游植物群落特征及其生物量变化
DOI：
10.1016/j.marpolbul.2018.06.018
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发表时间：
2018
影响因子：
5.8
通讯作者：
Lin Mao
中科院分区：
文献类型：
--
作者：
Wang Yu;Kang Jian-hua;Liang Qian-yong;He Xue-bao;Wang Jian-jun;Lin Mao
我们对2013年5月中旬（钻前）和10月上旬（钻后）南海北部东沙天然气水合物钻探区的现场观测数据进行了分析，研究了浮游植物群落和生物量的变化以及溶解甲烷等环境因素的影响。结果表明，南海东沙天然气水合物钻探区呈现出典型的低营养盐、低叶绿素（LNLC）环境，浮游植物丰度较低。共鉴定出5纲52属103个类群，以硅藻和甲藻为主。浮游植物丰度和叶绿素(Chla)在地下最大层最高。钻前和钻后地下叶绿素最大值（SCM）稳定在75m（分别为0.30±0.06mg/m3和0.51±0.29mg/m3），钻后地下最大丰度从钻前地表（707.14±243.98cells/L）更深至75m（604.17±313.22cells/L）。钻探后，磷酸盐和氯含量显着增加，但丰度没有显着差异。硅藻优势种基本不变，甲藻的出现和丰度明显增加，而蓝藻在钻探后呈现多样性。冗余分析(RDA)和Spearman相关分析均表明温度、pH和磷酸盐是引起浮游植物群落结构波动的主要因素，而溶解甲烷的直接影响不显着。我们清楚地发现特定水层（50 至 75m 之间）和溶解甲烷浓度也异常高的站（DS06、DS08 和 DS15）的丰度和甲烷含量均增加。这项研究似乎在一定程度上与墨西哥湾天然石油渗漏的发现相一致，墨西哥湾天然石油和天然气渗漏区的湍流可以通过上升的气泡抬高底层水，并将富含营养物质的冷海水从深层渗漏带到温跃层。这种羽流产生的上升流可能会对富光带内上层中上层水域的光合物种产生自下而上的影响。
We analyzed the data obtained from field observations on a gas hydrate drilling area in Dongsha of northern South China Sea (SCS) in middle May (before drilling) and early October (after drilling) in 2013. The variation in the phytoplankton communities and biomass as well as the impacts of environmental factors including dissolved methane was studied. Results indicated that the gas hydrate drilling area in Dongsha, SCS exhibited a typical low-nutrients low-chlorophylla(LNLC) environment accompanied with low phytoplankton abundance. A total of 103 taxa belonging to 52 genera of 5 classes were identified, with diatoms and dinoflagellates dominating the community. Both phytoplankton abundance and chlorophylla(Chla) were highest at the subsurface maximum layer. The subsurface chlorophyll maximum (SCM) before and after drilling were stabilized at 75 m (0.30 ± 0.06 mg/m3and 0.51 ± 0.29 mg/m3, respectively), while the subsurface maximum of abundance after drilling went deeper to 75 m (604.17 ± 313.22 cells/L) from the surface (707.14 ± 243.98 cells/L) before drilling. After drilling, phosphate and Chlaincreased significantly, but no significant differences were observed on abundance. Dominant species of diatoms were basically constant with dinoflagellates becoming more apparent in higher occurrence and abundance, while Cyanophyta was diverse after drilling. Redundancy analysis (RDA) and Spearman's correlation analysis both indicated that temperature, pH and phosphates were major factors causing fluctuation in phytoplankton community structure, while dissolved methane had non-significant impact directly. We clearly found both abundance and Chlaincreased in particular water layers (between 50 and 75 m) and at stations (DS06, DS08 and DS15) where dissolved methane concentrations were also abnormally high. This study appeared to partly coincide with the findings of natural oil seeps in the Gulf of Mexico, which assumed that the turbulence from the natural oil and gas leaking zone could raise the bottom water through the rising bubbles and bring cold nutrient rich waters to the thermocline from the deep seeps. This plume-generated upwelling could then fuel a bottom-up effect on the photosynthetic species in the upper pelagic waters within the euphotic zone.