秦皇岛海域赤潮期间浮游植物的生态特征

Ecological characteristics of phytoplankton in Qinhuangdao coastal areas during the red-tide period

2010年5月下旬,秦皇岛海域暴发了多次赤潮,其影响一直持续至当年的8月份。通过2010年5–9月对秦皇岛近岸海域进行的5个月份调查,对赤潮期间该海域浮游植物的种类组成、时空分布、群落结构特征及浮游植物与夜光藻的依存关系、浮游植物与环境因子的关系进行了分析。结果表明,调查海域共检出浮游植物46属96种,主要隶属硅藻门（Bacillario phyta）和甲藻门（Pyrroptata）,生态类型多数为广温广盐的广布种或近岸性种类,少数为暖海性物种或远洋性种类。主要优势种有夜光藻（Noctiluca scintillans）、斯托根管藻（Rhizosolenia stolterfothii）、角毛藻（Chaetoceros sp.）、圆筛藻（Coscinodiscus sp.）和辐杆藻（Bacteriastrum sp.）等。共鉴定赤潮生物48种,占浮游植物种类数的50%。浮游植物丰度均值的变化范围为6.20×10^4-4 129.53×10^4 cells/m3,其丰度均值的高峰出现在9月份,低谷出现在7月份。调查海域浮游植物5个月份的多样性指数均值都大于1,生物多样性状况良好,群落结构比较稳定;聚类分析表明,5个调查月份群落相似性程度较高,相似性范围为40%-71%。相关性分析表明,浮游植物平均丰度与盐度存在显著的负相关关系（r=–0.734,P〈0.01,N=37）;与无机氮营养盐（DIN）存在显著地正相关关系（r=0.753,P〈0.01,N=37）,推测调查期间该海域浮游植物生长繁殖的主导环境因子为无机氮营养盐。浮游植物物种与环境因子的典范对应分析表明,N/P、盐度、硝酸盐、硅酸盐、亚硝酸盐和水温是影响秦皇岛海域浮游植物群落结构特征的主要环境因子。

The spatio-temporal distribution of phytoplankton is influenced by physical and chemical factors such as water temperature, salinity, dissolved oxygen, p H, and nutrients. Nitrogen（N） and phosphoros（P） are essential for the growth of phytoplankton which play a key role in determining the abundance of phytoplankton. The species composition, community similarity, and diversity of phytoplankton affect the structure and function of ocean ecosystems. Marine phytoplankton can be used as a rapid and sensitive indicator of environmental changes. The coastal region of Qinhuangdao is used by fish, shrimp, and crabs for spawning and feeding. However, this region has experienced an increase in the frequency of red tides as a result of pollution and marine development. In 2010, red tides began in late May and lasted until August. We evaluated the species composition, spatio-temporal distribution, community structure of phytoplankton and the relationship between phytoplankton abundance and environmental factors based on data collected during five surveys conducted from May to September, 2010. We identified 96 species belonging to 46 genera of phytoplankton. The phytoplankton community was primarily composed of Bacillariophyta and Pyrrophyta. The majority were neritic species or cosmopolitan species which were eurythermal and euryhaline, while the remainder was oceanic warm water or oceanic species. The dominant species include Noctiluca scintillans, Rhizosolenia stolterfothii, Chaetoceros sp., Coscinodiscus sp., and Bacteriastrum sp.. A total of 48 red tide causative species were observed（-50% of total species）. The mean phytoplankton abundance ranged from 6.20×10^4 cells/m3 to 4 129.53×10^4 cells/m3. Abundance peaked in September 2010 and was lowest in July 2010. The diversity index values were all 1.0 which suggested biodiversity and community structure was healthy. The highest indices of community structure and biodiversity were observed in September, and biodiversity was lowest in June. The community similarity of phytoplankton was relatively high and the range in similarity was from 40% to 70% from May to September. The community similarity was ranked in order： September〉July〉August〉May〉June. The average abundance of phytoplankton was significantly negatively correlated with salinity（r=–0.734, P〈0.01, N=37） and significantly positively correlated with inorganic nitrogen nutrients（r=0.753, P〈0.01, N=37）. We conclude that inorganic nitrogen is the primary factor explaining the increase in phytoplankton abundance during the study period. A canonical correspondence analysis of the relationship between phytoplankton species and environmental factors indicated that N/P, salinity, nitrate, silicate, nitrite, and water temperature were the main environmental factors which influenced the community structure of phytoplankton in the coastal areas of Qinhuangdao.