Variations in the chemical lability of iron in estuarine, coastal and shelf waters and its implications for phytoplankton

The relationship between total and chemically labile Fe has been studied in estuarine, coastal and shelf waters of the Gulf of Maine, U.S.A. Measurements of the labile fraction of total Fe, defined by complexation with 8-hydroxyquinoline in 1 h, correlate with the availability of Fe to marine phytoplankton and therefore can be used to estimate Fe availability in seawater. The results show that the relative lability (=labile/total) of Fe in seawater varied both spatially and temporally from near-zero to 100%. Although particulate Fe (>0.45 μm) was generally less labile than dissolved Fe (<0.45 μm), the particulate fraction often contributed substantially to labile Fe concentrations overall. Conversely, as much as 75% of ‘dissolved’ Fe was non-labile, and therefore was probably not available to phytoplankton. In seawater/river-water mixing experiments, aggregation diminished the relative lability of Fe by 30%, even though much of it remained in the ‘dissolved’ fraction. Considering phytoplankton nutrition, these results demonstrate that equating dissolved Fe concentrations with ‘available’ metal can be misleading. Furthermore, the large variability observed in the labile proportion of total Fe in seawater indicates that Fe availability to phytoplankton cannot be estimated by applying fixed lability-ratios to total Fe concentrations.     

2009年4月浙江近岸海域浮游植物的分布特征及与环境因子的关系

利用2009年4月在浙江近岸海域采集的47个浮游植物水样,对该海域浮游植物的类群组成及其空间分布特征进行了研究,并分析了其空间分布特征与环境因子的关系,结果表明:(1)共鉴定出浮游植物81种,隶属于4门32属,其中硅藻26属69种,甲藻4属10种,硅藻在种类数上占优势,中肋骨条藻Skeletonema costatum和具槽直链藻Melosira sulcata为优势种。(2)各水层浮游植物总细胞密度为(2~236.8)×102个/dm3,平均值为41.9×102个/dm3。平面分布上,表层和5 m层的浮游植物总细胞密度分布趋势较一致,即调查区域最南端出现高值区(>200×102个/dm3),沿岸向北则细胞密度值呈递减趋势。硅藻细胞密度为(1.2~236.4)×102个/dm3,平均值为40.88×102个/dm3,与浮游植物总细胞密度分布趋势基本一致。甲藻细胞密度为(0~13.6)×102个/dm3,平均值为0.94×102个/dm3。垂直分布上,浮游植物总细胞密度大小依次为30 m层(82.5×102个/dm3)>表层(35.3×102个/dm3)>10 m层(31.9×102个/dm3)>5 m层(31.8×102个/dm3)。断面分布上,浮游植物总细胞密度由大到小依次为D断面(83.1×102个/dm3)>C断面(36.5×102个/dm3)>B断面(30.9×102个/dm3)>A断面(16.3×102个/dm3)。(3)总体上,浮游植物生态分布与水温、营养盐均呈正相关关系。     

Chromatographic studies of dissolved organic matter and copper-organic complexes isolated from estuarine waters

Dissolved organic matter (DOM) and dissolved copper-organic complexes were isolated from the estuarine waters of Narragansett Bay, RI, using reverse-phase liquid chromatography (RPLC). Different types of reverse-phase BOND ELUT columns (Analytichem International), including C₂, C₁₈ and phenyl-bonded phases, were studied to determine their adsorption efficiency for extracting DOM. Extraction efficiencies followed the order phenyl > C₁₈ > C₂, and phenyl − C₁₈ > C₂ for DOM and organic copper, respectively. However, comparisons of BOND ELUT and C₁₈ SEP-PAK (Waters Associates) columns indicated that SEP-PAK columns were the most efficient when both DOM and organic copper were considered. Chromatographic profiles of the isolated DOM obtained using high-performance liquid chromatography were similar in elution characteristics and resembled chromatograms typical of fulvic acid. The UV-absorption characteristics of the DOM showed small differences and suggested that the different reverse-phase columns isolated material that was qualitatively similar.Copper-organic complexes isolated using C₁₈ RPLC were studied to examine the dissociation of organically bound copper in seawater as the pH is lowered. Only a small amount of the complexed copper was displaced by the H⁺ with about 40% of the copper remaining bound at pH 3. However, the chromatographic elution behavior of the DOM and organic copper was significantly altered under acidic conditions as a result of protonation of acidic functional sites on the organic matter.     

The conservative and non-conservative behavior of chromophoric dissolved organic matter in Chinese estuarine waters

The spectral absorption properties of chromophoric dissolved organic matter (CDOM) and their distributions in two Chinese estuaries, the Yangtze River Estuary and the Jiulong River Estuary, were studied during August 2003 (wet season) and during different seasons between 2003−2005, respectively. The CDOM concentrations (a₃₅₅) of fresh end members in the Jiulong River Estuary varied seasonally, while its quality remained relatively stable. However, the a₃₅₅ of the marine end members exhibited less variability. Application of a conservative mixing model indicated that CDOM behaved conservatively in the Yangtze River Estuary. No photobleaching removal was observed at high salinity region of this estuary. Although CDOM showed conservative behavior for many cruises in the Jiulong River Estuary, there was evidence for removal in the low salinity regions during some cruises. Laboratory mixing experiments and a salt addition experiment suggested that particle sorption of CDOM maybe the possible reason for the removal. These results showed that absorption properties of CDOM can be used as a tool to observe the quantitative and qualitative dynamics of DOM during estuarine mixing.     

Particulate matter and components of the organic substance in the surface waters of the Southern and Atlantic Oceans

The integrated studies of the particulate matter and organic compounds in the surface waters and the snow-ice cover by means of geochemical (the concentrations of the particulate matter, the Corg, the hydrocarbons, the lipids, and the chlorophyll a) and optical techniques were performed in the Southern Ocean and in the east of the Atlantic Ocean along the vessel’s route: Africa-Antarctica-Africa-St. Petersburg. The correlations between the treated compounds were found. It was shown that the supply of pollutants affects not only the concentrations but also the proportions of the considered compounds. New data were obtained on the processes of the accumulation of particulate matter and organic compounds under the ice formation.     

Isolation of dissolved organic matter and copper-organic complexes from estuarine waters using reverse-phase liquid chromatography

Reverse-phase liquid chromatography was used for the isolation of dissolved organic matter and dissolved copper-organic complexes from the estuarine waters of Narragansett Bay, Rhode Island. The procedure isolates 10–30% of the organic matter and up to 50% of the total dissolved copper from various bay samples. Chromatograms obtained by high-performance liquid chromatography of the isolated organic matter showed qualitative differences between sampling stations progressing from the Providence River in the upper bay to the lower bay.     

2003-2004年浙江沿岸海域浮游植物的分布特征及其与环境因子的关系

2003年夏季和2004年夏、秋季,分别在浙江沿岸海域10m等深线(以下称内侧海域)和50 m等深线(禁渔线附近,以下称外侧海域)处共设置37个站位,对采集于大、小潮汛期间的浮游植物样品进行了种类组成、优势种、细胞丰度分布和群落结构特征的调查研究,并分析了其分布特征与环境因子的关系.结果表明,调查海域共鉴定出浮游植物3...     

Scavenging of particulate matter in coastal waters

The uptake of a suite of 19 metals from coastal seawaters upon both glass and Teflon surfaces reflected primarily the sorption of particulate matter derived from crustal rock weathering. Uptake for all elements was greater in the light than in the dark. Based upon these and earlier results, a new definition of scavenging for environmental systems is proposed.     

Effect of ocean acidification on coastal phytoplankton composition and accompanying organic nitrogen production

The effect of ocean acidification, caused by the increase in pCO₂ in seawater, on phytoplankton population and on related organic nitrogen production was experimentally examined by use of a natural coastal microbial population. pCO₂ and pH were controlled by aeration with air in which pCO₂ was at the current level (control), for which ambient air was used, and with air in which pCO₂ was ??800?? and ??1200?? ppm, in 500-L culture vessels. The experiment was continued for 15?days after addition of the inorganic nutrients such as nitrate, phosphate, and silicate. During most of the experimental period, a minor increase in phytoplankton biomass was noted, probably because of low irradiance, an increase in phytoplankton biomass was observed at the end of the experiment. Flow cytometric and microscopic observations revealed that this increase was because of Chrysochromulina sp. (Haptophyceae). The growth of Chrysochromulina sp. was most obvious in the control vessel, and tended to be obscured by increasing pCO₂ (decrease in pH), indicating the possibility that ocean acidification inhibits the growth of specific phytoplankton groups, for example Chrysochromulina sp. Production of particulate organic nitrogen (PON), determined by the ¹⁵N tracer method, also diminished under acidified conditions compared with that at the current level.     

溶解有机物的光降解及其对浮游细菌和浮游植物的影响

作为海洋中最大的动态有机碳储库,溶解有机物的光降解(主要是紫外波段)对生源要素的生物地球化学循环以及海洋生态系统的结构和功能具有重要的影响。本文探讨了影响溶解有机物光降解的环境因素、其光化学过程和产物,并重点阐述了溶解有机物的光降解对浮游细菌和浮游植物的影响。溶解有机物的来源和成分复杂,其光降解在不同海区有不同的生态效应,为了能更准确地把握其生态效应,需要更全面和深入的研究。     

Production of chromophoric dissolved organic matter fluorescence in marine and estuarine environments: an investigation into the role of phytoplankton

We tested whether phytoplankton are a direct source of chromophoric dissolved organic matter (CDOM) fluorescence in a series of experiments. In the first experiment, sonication of 11 dense algal cultures from several algal classes revealed no immediate release of CDOM fluorescence. In a second experiment, using nutrient addition bioassays from a range of sites in the mid-Atlantic region, we found no increase in CDOM fluorescence when nutrient limitation was alleviated despite large increases in chlorophyll a over 3–5 days. In a third experiment, the change in CDOM fluorescence over a 28-day period in five non-axenic algal batch cultures was measured. There was little or no increase in CDOM fluorescence until the cultures entered the stationary phase, whereupon an exponential increase in CDOM fluorescence was observed. In a fourth set of experiments, the production of CDOM fluorescence was examined in a series of cultures of Skeletonema costatum and Prorocentrum minimum. In the dark, in the absence of autotrophic growth, we observed slow rates of CDOM fluorescence production (0.02–0.05 NFlU day⁻¹). Rates were much higher in parallel lighted cultures (0.1–0.2 NFlU day⁻¹) but were more related to bacterial counts than to algal biomass. In a third phase of this experiment, when illuminated, stationary phase cultures were filtered through 1-μm pore size filters and incubated in the dark, CDOM fluorescence production continued unchanged. These results are consistent with the hypothesis that phytoplankton are not a direct source of CDOM fluorescence in marine and estuarine environments and that CDOM fluorescence is produced by bacteria using non-fluorescent organic matter derived from phytoplankton.     

Distribution and composition of phytoplankton in northeastern coastal waters of the United States

Results are given from collections made during eight cruises over the northeastern continental shelf. Seasonal phytoplankton assemblages are noted, which include a variety of ultraplankton components. Areas of greatest cell concentrations were at near shore stations, Georges Bank, and at scattered sites over the shelf. Dominant species included Skeletonema costatum, Asterionella glacialis and Leptocylindrus danicus.     

Nutrients,light and phytoplankton production in the shallow,tropical coastal waters of Bandon Bay,Southern Thailand

Phytoplankton primary production and its regulation by light and nutrient availability were investigated in the shallow, tropical coastal waters of Bandon Bay, Southern Thailand. The bay was meso‐eutrophicated and highly turbid, receiving river water discharge. Water column stratification was consistently weak during both rainy and dry seasons. Dissolved inorganic nitrogen (DIN) was higher off the river mouth than in the other regions, suggesting that river water discharge was a main source of DIN. By contrast, dissolved inorganic phosphorus (DIP) showed a significant negative correlation with total water depth, implying that regeneration around the sea floor was an important source of DIP. Surface DIN and DIP showed positive correlations with surface primary production (PP) and water column primary productivity (ΣPP*), respectively. The combined correlation and model analyses indicate that total water depth had an ambivalent influence on water column primary production (ΣPP); shallower water depth induced more active regeneration of nutrients, but it also caused higher turbidity and lower light availability as a result of enhanced resuspension of sediments. Furthermore, there was a vertical constraint for phytoplankton during the rainy season: total water depth tended to be shallower than euphotic zone depth. In conclusion, light limitation and vertical constraint owing to shallow water depth appear to be more important than nutrient limitation for water column primary production in Bandon Bay.     

海岸河口泥沙数学模型研究进展

对海岸河口泥沙运动的基本方程、数值方法、边界条件、参数选取等进行了归纳总结和评述,以期对本学科的发展起到一定的引导和促进作用。     

Methodology of X-ray fluorescence analysis of suspended matter in estuarine waters

Twenty-seven samples of suspended sediments collected on Millipore filters from the St. Lawrence estuary were directly analysed for Si, Al, Ca, Mg, Na, K, Fe, Ti, Mn, Ni, Co, Cu, Cr and Zn by X-ray fluorescence using standards prepared from suspended matter collected by continuous flow centrifugation. Calibration curves prepared from the analysis of these standards could be directly used in calculating the weight percent of elements for the unknown samples, if the weight of the total suspended matter on the filters did not exceed 25 mg.     

海岸河口潮流数值模拟的研究与进展

对海岸河口地区潮流场的数值模拟方法进行了较为系统的归纳总结和评述,对潮流数值模拟的发展趋势进行了分析.     

我国近岸海域富营养化评价新方法及应用

参考目前国际上被广泛应用的第2代富营养化评价方法体系,结合我国近岸海域生态环境特点和监测资料现状,建立了一种以压力-状态-响应模式为基本框架、以富营养化症状为主的第2代近岸海域富营养化评价体系。实际应用结果表明,应用本方法得出的长江口海域富营养化状况评价结论,与目前国外主流评价方法的评价结论一致,而且本方法具有评价指标代表性强、数据资料易得、评价标准有据、方法简便易行等优点。     

我国近岸海域富营养化评价新方法及应用

参考目前国际上被广泛应用的第2代富营养化评价方法体系,结合我国近岸海域生态环境特点和监测资料现状,建立了一种以压力-状态-响应模式为基本框架、以富营养化症状为主的第2代近岸海域富营养化评价体系。实际应用结果表明,应用本方法得出的长江口海域富营养化状况评价结论,与目前国外主流评价方法的评价结论一致,而且本方法具有评价指标代表性强、数据资料易得、评价标准有据、方法简便易行等优点。     

Speciation of dissolved metals associated with organic matter in coastal seawaters

By combined use of chloroform extraction and Amberlite XAD-2 resin chromatography, metal-organic compounds dissolved in coastal seawaters of Harima Sound, the Seto Inland Sea, were separated into three groups: hydrophobic, hydrophilic neutral and basic, and hydrophilic acidic. The hydrophobic metal-organic compounds, which are associated with organic matter with molecular weight less than 300, accounted for only a small fraction of the metal-organic compounds; 6 % for Cu and an insignificant fraction for Fe, Mn and Zn. The hydrophilic metal-organic compounds with molecular weights between 100 and 1,500 were major components of the metal-organic compounds. The metals associated with the organic matter on average accounted for 12 % of the Fe, 11 % of the Mn, 7 % of the Zn and 23 % of the Cu of the reactive dissolved metals.