Investigation of the environmental control on the phytoplankton and bacterioplankton in two contrasting temperate estuaries
Investigation of the environmental control on the phytoplankton and bacterioplankton in two contrasting temperate estuaries
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发表时间：
2017-10
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通讯作者：
Amani Alshatti
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作者：
Amani Alshatti
河口的物理化学参数和生物组成的频繁测量是评估这些过渡性沃茨生态状况的关键。关于英国南部海岸两个温带河口的微生物群落组成，南安普顿水和基督城港（Mudeford码头）知之甚少。本研究项目的目的是调查这两个河口春季和夏季浮游植物水华期间优势系统发育异养细菌种群的丰度和动态变化与主要理化参数的关系。2013年期间，南安普顿水域春季浮游植物水华发生在水温低于10°C时，而基督城港则发生在14°C时，在接下来的几年里，分别在2014年和2015年，在14 °C和15 °C的南安普顿水中。南安普敦水域的春季水华叶绿素a浓度在所有三年中从未超过10 μg L-1，而在克赖斯特彻奇港，2013年春季的主要峰值达到44 μg L-1。南安普敦水域的表面盐度范围很窄，为27 - 33，而在基督城港入口处的Mudeford码头，检测到的范围更大，为1.3 - 22。与南安普顿水域相比，在两个河口之间检测到的硝酸盐、磷酸盐和硅酸盐无机营养盐浓度在基督城港的范围要大得多，反映了不同河流的贡献。确定生物成分的影响的物理-化学控制影响他们的动态和继承。通过HPLC色素分析结合显微计数对南安普敦水域的浮游植物群落进行了评估，海链藻属，和角毛藻（Chaetoceros sp.）春季水华以甲藻为主，夏季水华以甲藻为主，主要种类为Scripsiella sp.和原甲藻Prorocentrum sp..对1%（PFA）的水样进行核酸染色（DAPI和SYBR绿色I），进行浮游细菌总数计数。与荧光显微镜测定的DAPI细胞计数相比，流式细胞术在春季和夏季浮游植物水华期间略微高估了细菌浓度，但总体而言，南安普顿水域和基督城港口的两种方法之间存在显著相关性（r =0.87，r = 0.85，p <0.0001，n = 32）。利用寡核苷酸探针荧光原位杂交技术（FISH）对河口及与环境条件相关的水体样品中异养细菌的丰度和优势度进行了研究。β-变形菌与盐度呈显著负相关（r =-0.95，p <0.0001，n = 29），表明它们有利于淡水系统。α-、γ-变形菌的检出率与温度、盐度呈显著相关。然而，只有适度的相关性之间的系统发育组和Chl‐a浓度强调的事实，theterotrophic细菌可能利用有机碳从其他来源的河口系统。主成分分析（PCA）结果表明，温度对真细菌和广古菌的影响最大，而在系统发育级水平上，盐度和叶绿素a对变形菌门的丰度和演替影响最大。
Frequent measurements of the physical‐chemical parameters and biologicalcomponents of estuaries are key for assessing the ecological status of thesetransitional waters. Little is known about the microbial community composition oftwo temperate South Coast UK estuaries, Southampton Water and ChristchurchHarbour (Mudeford Quay). The aim of this research project was to investigate howchanges in the abundance and dynamics of the dominant phylogenetic heterotrophicbacteria populations relate to major physical‐chemical parameters duringphytoplankton bloom periods in the spring and summer months in these twoestuaries.During 2013 in Southampton Water, the spring phytoplankton bloom occurred whenthe water temperature was below 10°C whereas in Christchurch Harbour it occurredat 14°C, and in the following years in Southampton Water at 14 °C and 15 °C, in 2014and 2015, respectively. The spring bloom chlorophyll a concentrations inSouthampton Water never exceeded 10 μg L‐1 in all three years while in ChristchurchHarbour a major peak in spring 2013 reached 44 μg L‐1. Surface salinity inSouthampton Water showed a narrow range of 27‐33 whereas, at Mudeford Quay atthe entrance to Christchurch Harbour a much larger range was detected of 1.3‐22.The concentration of inorganic nutrients detected between the two estuaries fornitrate, phosphate and silicate had a much higher range in Christchurch Harbourcompared to Southampton Water reflecting the contribution from different riversources. Identifying the biological components the influence of the physical‐chemicalcontrols affecting their dynamics and succession. The phytoplankton community inSouthampton Water was assessed from HPLC pigment analysis coupled withmicroscopic counts, and indicated diatoms (Skeletonema sp., Thalassiosira sp., andChaetoceros sp.) dominated the spring bloom and dinoflagellates dominated summerbloom with major species Scripsiella sp. and Prorocentrum sp.Nucleic acid staining (DAPI and SYBR Green I) was applied to 1% (PFA) preservedwater samples for total enumeration of bacterioplankton. A cytosense flowcytometry slightly overestimated the concentration of bacteria compared to DAPIcell counts determined using a fluorescent microscope mainly during thephytoplankton spring and summer blooms but overall with significant correlationbetween the two methods for Southampton Water and Christchurch Harbour (r =0.87, r = 0.85, p <0.0001, n = 32 respectively). Fluorescence in situ hybridization(FISH) with oligonucleotide probes was used to determine the abundance anddominance of various heterotrophic bacteria groups in samples from both estuariesand theses related to environmental conditions. Betaproteobacteria showed a strongnegative significant correlation with salinity (r = ‐0.95, p <0.0001, n = 29) in the twoestuaries indicating they favour fresh water systems. Alpha‐, andGammaproteobacteria were detected with variable significant correlation withtemperature and salinity. However, only a moderate correlation was observedbetween the phylogenetic groups and Chl‐a concentrations highlighting the fact thatheterotrophic bacteria may utilize organic carbon from other sources in theestuarine system. A principal component analysis (PCA), indicated temperature tobe the most influence on bacteria domain levels (Eubacteria and Euryarchaea).Whereas, at phylogenetic class level proteobacterial phyla, salinity and Chl‐a werethe most influence on their abundance and succession.