2021-2022年春、秋季嵊泗列岛浮游植物群落状况及长期变化特征

为更好地了解嵊泗列岛海域在人类活动和气候变暖影响下的生态现状以及变化特征,于2020年秋季和2021年春季在该海域进行了浮游植物的拖网与水样采集及环境要素分析。水采样品中共检出浮游植物6门54属105种。其中,硅藻33属68种,甲藻14属30种,蓝藻、金藻和隐藻各2属2种,绿藻1属1种。春、秋季浮游植物主要优势种为骨条藻(Skeletonema spp.),并在秋季占据绝对优势(Y=0.975)。春季平均细胞丰度(7.17±7.78)个/mL]明显低于秋季(77.23±73.44)个/mL]。春季Shannon-Wiener多样性指数和Pielou均匀度指数均高于秋季。Spearman相关分析表明,浮游植物丰度与水温和透明度呈显著正相关,与盐度呈显著负相关。冗余分析显示,浮游植物群落组成与水温、营养盐密切相关。网采样品中共检出浮游植物4门46属94种,硅藻占比最大;春、秋季平均细胞丰度分别为838.17×10³和19406.43×10³个/m³。与水样相比,骨条藻仍为主要优势种,且优势度更高;网采获得的秋季多样性指数和均匀度指数(分别为0.23和0.05)低于水采(分别为0.38和0.10)。将本次网采结果与1990年、2007年调查资料对比发现,嵊泗列岛春、秋季浮游植物群落组成发生了明显改变:丰度明显升高,硅甲藻占比无明显变化,暖水种种类数明显增加,骨条藻优势地位增强,多样性指数和均匀度指数下降。这可能与变暖与富营养化加剧相关。近30年来,溶解无机氮在春季无显著变化,但在秋季显著升高;活性磷酸盐浓度在春、秋季均显著降低;氮磷比在春、秋季均显著升高。浮游植物的变化特征较好地指示了嵊泗列岛海域在富营养化和气候变暖下的生态环境变化。

Current status and long-term change of phytoplankton community around the Shengsi Islands in spring and autumn from 2021 to 2022

In order to obtain a better understanding of the ecological status and changing characteristics of the marine ecosystem around the Shengsi Islands under human activities and global warming, we collected net and water samples of phytoplankton and analyzed environmental factors in autumn 2020 and spring 2021. A total of 6 phyla, 54 genera, and 105 species were identified, including 68 species and 33 genera of Bacillariophyta, 30 species and 14 genera of Pyrrophyta, 2 species and 2 genera of all Cyanophyta, Chrysophyta and Cryptophyta, and 1 species and 1 genus of Chlorophyta. Skeletonema spp. was dominant in spring and autumn, especially in autumn with dominance at 0.975. The average cell abundance in spring ((7.17±7.78) cells/mL) was significantly lower than that in autumn ((77.23±73.44) cells/mL). The Shannon-Wiener diversity index and the Pielou''s evenness index were higher in spring than in autumn. Spearman correlation analysis showed that phytoplankton abundance was significantly positively correlated with water temperature and transparency, but negatively correlated with salinity. Redundancy analysis revealed that phytoplankton community was highly associated with temperature and nutrients. In addition, a total of 4 phyla, 46 genera, and 94 species were identified using the net collection method, with diatoms accounting for the greatest proportion. The average cell abundances in spring and autumn were 838.17×10³ and 19406.43×10³ cells/m³, respectively. Skeletonema spp. remained the dominant species, with dominance higher than that in water-collected samples. However, the diversity and evenness indices in autumn obtained from net-collected samples (0.23 and 0.05, respectively) were lower than those from water samples (0.38 and 0.10, respectively). Compared with the survey data in 1990 and 2007 using net collection method, we found that phytoplankton community around the Shengsi Islands in spring and autumn has undergone significant changes in the past 30 years. The abundance increased significantly, although the proportion of diatom and dinoflagellate species varied nonsignificantly; the warm-water species number increased markedly; the dominance of Skeletonema spp. increased; and the diversity and evenness indices decreased. These long-term changes in phytoplankton may be largely related to the intensification of warming and eutrophication. The concentration of dissolved inorganic nitrogen showed no significant change in spring, but increased significantly in autumn. Dissolved reactive phosphorus concentration decreased significantly in both spring and autumn. Consequently, N/P increased significantly in both spring and autumn. The changing trend of phytoplankton indicated the ecological and environmental changes around the Shengsi Islands under eutrophication and warming.