基于MODIS数据的太湖浮游植物物候变化及其对水表温度的响应

浮游植物物候能够反映浮游植物的生长变化与湖泊生态系统的变化,水温、营养盐浓度等因素对物候有重要影响。太湖富营养化程度较高,水温的影响作用日趋显著,物候与水温关系的研究对理解、控制和改善太湖生态系统具有重要意义。本研究利用2003—2018年MODIS遥感数据计算浮游植物物候指标和湖泊水表温度（Temperature of Water Surface,LSWT）,通过分析太湖浮游植物物候时空变化特点探究了不同区域的物候特征,并结合LSWT揭示了浮游植物物候对LSWT变化的响应关系。结果表明：① 不同浮游植物物候指标具有不同空间分布特点,水华发生次数、峰值叶绿素a（Chla）浓度和水华总持续时间呈现由西部沿岸向湖心区递减的趋势;浮游植物生长开始时间和峰值Chla发生时间分布复杂但在沿岸区域相对较早;② 太湖可被划分为4种具有不同物候特征的区域,Ⅰ类区域主要位于贡湖湾、东部沿岸以及太湖中部开阔水域,该区Chla浓度范围为50~60 μg/L,且波动平缓,水华发生次数最少、开始最晚、持续时间最短;Ⅱ类区域主要分布于太湖西部沿岸,Chla浓度范围为50~90 μg/L且变化剧烈,该区水华发生次数最多、开始最早、持续时间最长;Ⅲ和Ⅳ类属于过渡区域,前者主要分布于梅梁湾、竺山湾及入湾口,后者主要位于南部沿岸以及太湖中部;③ 浮游植物物候对LSWT变化的响应受营养水平影响,当营养水平较高时,浮游植物的生长受LSWT的促进作用显著,LSWT年际变化的升高趋势对浮游植生长物候提前、生物量增加的影响明显,反之,则LSWT变化对浮游植物生长的影响减弱。     

海洋浮游植物的生物富集热力学模型——对疏水性污染有机物生物富集双箱热力学模型

依据疏水性有机物（ＨＯＣ）在有机相／水相之间简单物理化学分配的基本原理,提出了浮游植物对ＨＯＣ生物富集双箱热力学模型。得出浮游植物对ＨＯＣ的生物富集因子ＢＣＦ与浮游植物比表面积Ｓ,有机物正辛醇／水分配系数ｋｏｗ,有机物在水中浓度Ｃｗ之间皆存在ｌｏｇ－ｌｏｇ相关性的结论,并且由海洋浮游植物对氯代苯的生物富集实验结果验证了该模型。     

Distribution characteristics of size-fractionated chlorophyll a and primary productivity in Beibu Gulf

The distribution of the abundance of phytoplankton, chlorophyll a (Chl.a) concentration and primary productivity in the Beibu Gulf were observed from May 23 to June 4, 1994.The results show that there were marked featares of spatial zonation in the survey area due to the differences between the geographic environment and the hydrological conditions.Chlorophyll a and primary productivity were higher in the inshore than in the middle area and higher in the north than in the south of the Beibu Gulf.The average concentration of Chl.a, primary productivity and the abundance of phytoplankton were 0.94±0.45 μg/dm³, 351±172 mg/(m²·d) (C) and 0.97×10⁴-10.050×10⁴ ind./m³ in the area, respectively.There were 176 species belonging to 4 phyla and 56 genera based on microscope identification.The results of the size-fractionation show that the contribution of nanoplankton and picoplankton was 77% to total Chl.a and 91% to total primary productivity, which proved their importance to phytoplankton communities in the Beibu Gulf.     

Chlorophyll-specific absorption coefficients and pigments of phytoplankton off Sanriku, northwestern North Pacific

The variety in shape and magnitude of thein vivo chlorophyll-specific absorption spectra of phytoplankton was investigated in relation to differences in pigment composition off Sanriku, northwestern North Pacific. Site-to-site variations of the absorption coefficients,a _ph ^* (λ), and pigment composition were clearly observed. At warm-streamer stations, higher values ofa _ph ^* (440) anda _ph ^* (650) were found with relatively high concentrations of chlorophyllb (a green algae marker). At stations located in the Oyashio water (cold streamer),a _ph ^* (440) values were lower and fucoxanthin (a diatom marker) concentrations were higher, compared to the other stations. The peak in the absorption spectra at the Oyashio stations was shifted toward shorter wavelengths, which was probably due to the presence of phaeopigments. In a Kuroshio warm-core ring, the magnitude ofa _ph ^* (440) was in between those at the warm-streamer and Oyashio stations, and the diagnostic pigment was peridinin (a dinoflagellate marker). These findings indicated that major differences in phytoplankton absorption spectra of each water mass were a result of differences in the phytoplankton pigment composition of each water mass, which was probably related to the phytoplankton community.     

Correction of atmospheric effect on ADEOS/OCTS ocean color data: Algorithm description and evaluation of its performance

This paper first describes the atmospheric correction algorithm for OCTS visible band data used at NASDA/EOC. Sharing a basic structure with Gordon and Wang’s Sea WiFS algorithm, it uses 10 candidate aerosol models including the “Asian dust model” introduced in consideration of the unique feature of aerosols over the east Asian waters. Based on the observations at 670 and 865 nm bands, the algorithm selects a pair of aerosol models that account best for the observed spectral reflectances, and synthesizes the aerosol reflectance used for the atmospheric correction. Two different schemes for determining the value of the parameter for the aerosol model selection are presented and their anticipated estimation error is analyzed in terms of retrieved water reflectance at 443 nm. The results of our numerical simulation show that the standard deviation of the estimation error of the “weighted average” scheme is mostly within the permissible level of ±0.002, reducing the error by 18% on average compared to the “simple average” scheme. The paper further discusses the expected error under the old CZCS-type atmospheric correction, which assumes constant aerosol optical properties throughout the given image. Although our algorithm has a better performance than the CZCS algorithm, further analysis shows that the error induced by the assumption taken in the algorithm that the water-leaving radiance at 670 nm band is negligibly small may be large in high pigment concentration waters, indicating the necessity for future improvements.     

Bioassessment Techniques for Monitoring of Eutrophication and Nutrient Limitation in Coastal Ecosystems

Bioassesment by the use of the macroalga, Ulva lactuca L., was carried out in the Limfjord, Denmark, to assess the significance of nitrogen and phosphorus as limiting factors for primary production during 1985, 1993, 1994 and 1995 and for the detection of changes in eutrophication levels.

Minimum and critical tissue concentrations for nitrogen and phosphorus in macroalgae were identified. The concentrations of nitrogen were generally below the critical concentration level in June–October in 1985, 1993, and 1995 but in 1994 nitrogen was only limiting for primary production in short periods. Only in early spring in 1985 and 1993 were the tissue concentrations of phosphorus below the critical concentration level, whereas in 1994 up to 3–4 months showed phosphorus limited growth, indicating that significant changes in limitation patterns can occur between different years.

It was concluded that the use of biomonitoring techniques is well suited as a bioassessment method for direct detection and for providing a time-integrated measure of nutrient availability in coastal waters, and thus for assessing ecosystem health with regard to eutrophication. It is recommended that biomonitors and the concept of critical tissue concentrations should be used in environmental management and incorporated in future monitoring programmes.     

Eutrophication Dynamics of Tolo Harbour, Hong Kong

The time and spatial variation of water quality in Tolo Harbour, a eutrophic landlocked semi-enclosed bay frequented by algal blooms, is studied using a dynamic eutrophication model. Hourly changes of tide levels and currents are computed by a link-node model assuming M₂ tidal forcing. Phytoplankton growth is assumed to be limited by solar radiation, nitrogen and temperature. The model incorporates light acclimation by algae, self-shading, photosynthetic production, nutrient uptake, and a dynamic determination of the carbon to chlorophyll ratio. In particular, sediment-water-pollutant interactions are modelled via an anaerobic benthic layer segment. Using recorded pollution loads and environmental forcing as input, the model predictions of daily-averaged water quality are compared with the extensive water quality monitoring data of the Environmental Protection Department (EPD). The predicted spatial distribution and trends of algal biomass, inorganic nitrogen, dissolved oxygen (DO), as well as sediment oxygen demand (SOD), are in general agreement with field observations.     

北极王湾海域浮游植物对光照和盐度变化的适应性研究

2006年夏末,对北极黄河站附近的王湾(Kongsfjorden)海域基础环境特征进行调查,并采用模拟实验研究了该海域浮游植物对光照和盐度变化的适应性。结果显示:浮游植物群落在无光照条件下培养1天或者1周后,叶绿素a浓度基本保持稳定或略有下降;随后将其置于自然光下培养,叶绿素a浓度呈现先明显下降、后稳步上升的趋势。在盐度实验中,稀释倍率为10%时,浮游植物群落生长速率达到最大值,但将稀释倍率增大到一定程度(≥40%)时,低盐会限制浮游植物生长。研究显示,夏末王湾海域浮游植物群落对低光照环境具有一定的适应性;另外,由于低稀释率能促进浮游植物的生长,湾外由于受到融水影响的程度较小,因而有益于浮游植物的生长。     

伊乐藻-草鱼圈养复合生态系统中水生生物的变化和影响

从细菌、浮游植物、浮游动物、底栖动物和有机碎屑等几个方面分析了养鱼对伊乐藻种植区(以下简称为有草区)和无草区水域环境的影响。结果表明:两个区域存在着显著的差异性。有草区由于生长着茂密的水生植被,对环境压迫的缓冲能力增强,水生生物的群落结构较为稳定,物种多样性指数高于无草区,有机物的沉降速率也大大低于无草区。与此相比,无草区对环境压迫的缓冲能力较差,水体浮游植物数量增加,富营养化加剧。通过本项实验可以看出,人工种植伊乐藻对养鱼区水质有着明显地控制作用,是发展生态渔业的一条有效途径。     

唐山祥云湾海洋牧场海域网采浮游植物群集特征研究

为研究唐山祥云湾海洋牧场海域网采浮游植物群集特征, 于2020年11月至2021年11月在祥云湾海洋牧场海域进行了浮游植物及环境因子的周年逐月调查。共鉴定浮游植物41属78种, 其中硅藻33属62种, 甲藻7属15种, 硅鞭藻1属1种, 年均丰度为205.58×10⁴ cells/m³, 多样性指数H''为2.88。与近岸非增殖海域不同, 该海域浮游植物的丰度及群落结构指数在春夏季水生生物繁生期达到全年最低。优势类群的季节演替明显, 其中, 3~5月以诺氏海链藻最占优势, 9~10月以角毛藻和中肋骨条藻最占优势, 周年优势类群以圆筛藻和角毛藻最占优势, 其优势度变动在6月前以圆筛藻显著为高, 之后则以角毛藻显著为高; 此外,甲藻的优势度在泛冬季(11~2月)达到最高。鱼礁区与对照区的对比结果显示, 两区域浮游植物的群落变化均可划分为泛冬季低温期(11~2月)、春夏季繁生期(3~6月)、泛秋季降温期(7~11月)三个时期。链状浮游植物的丰度在礁区明显高于对照区, 而非链状浮游植物则相反; 与生物作用关系密切的溶解有机碳、pH值在礁区低于对照区, 而总磷和溶解态硅则相反。Pearson相关及冗余分析(RDA)显示, 两区域浮游植物与环境因子的显著相关关系在不同时期差异明显。春夏季繁生期牡蛎礁上的贝类滤食活跃, 浮游植物与环境因子的关系最为密切, 浮游植物与环境因子的相关关系达到显著水平的数量最多。礁区与对照区浮游植物的群集特征差异可能受到礁体附着生物活动及潮汐往复流混合作用的影响。