Comparison of C and N stable isotope ratios between surface particulate organic matter and microphytoplankton in the Gulf of Lions (NW Mediterranean)

Carbon and nitrogen stable isotope ratios of particulate organic matter (POM) in surface water and 63–200 μm-sized microphytoplankton collected at the fluorescence maximum were studied in four sites in the Gulf of Lions (NW Mediterranean), a marine area influenced by the Rhone River inputs, in May and November 2004. Some environmental (temperature, salinity) and biological (POM, Chlorophyll a and phaeopigments contents, phytoplankton biomass and composition) parameters were also analysed. Significantly different C and N isotopic signatures between surface water POM and microphytoplankton were recorded in all sites and seasons. Surface water POM presented systematically lower δ¹³C (∼4.2‰) and higher δ¹⁵N (∼2.8‰) values than those of microphytoplankton, due to a higher content of continental and detrital material. Seasonal variations were observed for all environmental and biological parameters, except salinity. Water temperature was lower in May than in November, the fluorescence maximum was located deeper and the Chlorophyll a content and the phytoplankton biomass were higher, along with low PON/Chl a ratio, corresponding to spring bloom conditions. At all sites and seasons, diatoms dominated the phytoplankton community in abundance, whereas dinoflagellate importance increased in autumn particularly in coastal sites. C and N isotopic signatures of phytoplankton did not vary with season. However, the δ¹⁵N of surface water POM was significantly higher in November than in May in all sites likely in relation to an increase in ¹⁵N/¹⁴N ratio of the Rhone River POM which influenced surface water in the Gulf of Lions. As it is important to determine true baseline values of primary producers for analysing marine food webs, this study demonstrated that C and N isotopic values of surface water POM cannot be used as phytoplankton proxy in coastal areas submitted to high river inputs.     

Dynamics and fluxes of organic carbon and nitrogen in two Guiana Shield river basins impacted by deforestation and mining activities

Deforestation and mining activities have proven to be very damaging to rivers because these activities disturb the environmental characteristics of rivers. Thus, the concentrations of dissolved organic carbon (DOC), particulate organic carbon (POC), particulate nitrogen (PN), and Chlorophyll‐a (Chl‐a) were measured monthly during 2 hydrological years in the Maroni and Oyapock Rivers to assess the dynamics and fluxes of organic carbon and nitrogen in these 2 Guiana Shield basins, which have been strongly (Maroni) and weakly (Oyapock) impacted by deforestation and mining activities. The 2‐year time series show that DOC, POC, PN, and Chl‐a concentrations vary seasonally with discharge in both rivers, indicating a hydrologically dominated control. Temporal patterns of DOC, POC, and PN indicate that these variables show maximum concentrations in rising waters due to the yield of organic matter and nitrogen accumulated in soils, which are incorporated into the rivers during rainfall. However, the Chl‐a concentrations were at a maximum during low‐water stages. The C/N and C/Chl‐a ratios also showed a seasonal trend, with lower values during the low water periods due to an increase in algal biomass. During high water, the POC in both rivers is the result of terrestrial organic matter, whereas during low‐water autochthonous organic matter can reach up to 34% of the POC. The mean annual fluxes of TOC and PN were higher (4.56 × 10⁵ tonC year^?1 and 1.77 × 10⁴ tonN year^?1, respectively) in the Maroni River than those (1.84 × 10⁵ tonC year^?1 and 0.54 × 10⁴ tonN year^?1, respectively) in the Oyapock River. However, the specific fluxes of DOC, POC, and PN from both basins were nearly the same. Although gold mining activities are performed in both basins, there is no conclusive evidence regarding the impact of these activities on the dynamics of organic matter and particulate nitrogen in the Maroni and Oyapock Rivers.     

2007/2008年和2008/2009年夏季南大洋以及普里兹湾POC的分布与变化

在中国第24次和第25次南极科学考察期间,利用航渡表层水观测和普里兹湾定点观测,对颗粒有机碳(POC)的分布及其影响因素进行了研究.结果表明,南大洋表层水体的颗粒有机碳分布具有明显的区域性特征,表层水体POC的含量与营养盐和叶绿素a有着明显的相关分布趋势.南极水、亚南极水的表层POC浓度明显高于亚热带水和热带水,第24...     

刺参养殖池塘一种塑料人工参礁表面生态学特征初步研究

人工参礁在中国刺参(Apostichopus japonicus (Selenka))养殖业中被广泛应用,本文调查了2008年春、秋季刺参池塘中一种塑料人工礁表面的生物群落结构.采用沉积物捕捉器的方法调查了刺参池塘人工礁表面碳、氮、磷的循环及参礁的生态特征.结果表明,春季礁体底栖动物生物量及生物多样性高于秋季,底栖动物均集中在礁体外表面的缝隙内,4月礁体表面颗粒物,底泥沉积物总有机碳(TOC)平均含量分别为41.9 mg/g 和2.45 mg/g;总氮(TN)平均含量分别为4.1 mg/g 和0.2 mg/g.10月礁体表面颗粒物,底泥沉积物 TOC 含量分别为27.5 mg/g 和3.1 mg/g; TN 平均含量分别3.1 mg/g 和0.3 mg/g.4月 TOC, TN 沉积量分别达到711.2 mg/(m2·d)和70.7 mg/(m2·d);10月 TOC, TN 沉积量分别为804.9 mg/(m2·d)和87.3 mg/(m2·d).4月人工礁表面叶绿素/脱镁叶绿素(Chl a/Pheophytin)>1,表明礁体活体藻类较多.10月人工礁表面 Chl a/Pheophytin<1表明礁体表面降解颗粒物质较多.人工礁为刺参提供遮蔽场所,其表面生物膜为刺参提供优质食物,同时可增加池塘底面积,增强养殖系统稳定性.     

秋季湛江港和入海口温盐结构及生态特征

采用2015年10月采集的湛江港海域水体叶绿素a浓度、温度、盐度等参数,分析了秋季湛江港和入海口温盐结构及生态特征。研究结果表明,湛江港海域盐度的水平分布上由湾内往湾外逐渐递增,叶绿素a浓度由湾内往湾外逐渐递减,水深比较浅的区域水温较高,同时在航道入海口底层存在着“高盐低温低叶绿素”的相对稳定的冷水团结构。该水团的形成是由于湛江港出海口独特的地形构造促进区域性水体层化,同时底部水体透明度低,限制航道入海口区域底层的浮游植物的生长等因素所致。     

黄海海区的叶绿素α和初级生产力

本文是对70年代末以来我国在黄海西部海区进行的叶绿素a及初级生产力调查和研究的综述。内容包括叶绿素a水平分布,垂直分布。粒径大小分级,初级生产力的季节变化,山东近岸初级生产力,浮游植物量子产值及光利用效率,初级生产力模式及利用遥感法估算叶绿素a等。结果显示,黄海初级生产力有明显季节变化,春季最高,冬季最低;高生产力区位于长江口外海及黄海北部;大部份海区年平均值在200～500mg·m~(-2)。d~(-1)(以碳计)之间,平均值在425mg·m~(-2)·d~(-1)左右。     

Dynamics of carbohydrates in the Norwegian Sea inferred from monthly profiles collected during 3 years at 66°N, 2°E

Water samples were collected monthly for 3 years at 66°N, 2°E in the Norwegian Sea, 250 nautical miles off the Norwegian coast. Concentrations of mono- and polysaccharides were measured with the 2,4,6-tripyridyl-s-triazine (TPTZ) spectroscopic method. Total dissolved carbohydrates varied from 3.4 to 28.2 μM C of all samples and the ratio of carbohydrate to dissolved organic C (DOC) varied from an average of 14% at 0–25 m depth to 11% at 800–2000 m depth. This indicates that dissolved carbohydrates were a significant constituent of DOC in the Norwegian Sea. Polysaccharides varied from 0.4 to 21.5 μM C and monosaccharides from 0.7 to 11.7 μM C at all depths. The level of monosaccharides was relatively constant at 2.8–3.2 μM C below the euphotic zone, whereas polysaccharides showed more varying concentrations. Dissolved carbohydrates accumulated during the productive season, reaching maximum concentrations during summer although interannual differences were observed. A significant positive correlation between Chl a and soluble carbohydrate was found in one growing season with nutrient analyses. Average values for total carbohydrates were highest in the surface – 0 to 25 m – with 13.3 μM C and decreased to 8.4 μM C at 800–2000 m depth. The ratio of monosaccharides to polysaccharides exhibited a marked seasonal variation, increased from January to a maximum in June of 1.1, and declined to 0.5 in July.     

Laws of Chl. a maximum distribution and variation in the northern East China Sea

INTRODUCTIONTheChl.adistributionintheseawaterreflectstheabundanceanddistributionofphytoplankton,andthehighChl.aareasareusuallythedistributionareasofcentralfishingground.Intheearly1960s,Steelein1960andAndersonin1969concludedthatthereweresubsurfaceChl.amaximainthehomogeneouslystratifiedocean.Inthepast10a,ChinesescholarsmademanyinvestigationsonChl.aintheEastChinaSeacontinentalshelfareaanditsadjacentseaarealstudiedthegeneraldistributionofChl.aandtheformationmechanismofitsverticalmaxima,an…     

基于Aquatox模型的洱海营养物投入响应关系模拟

针对洱海富营养化加剧以及蓝藻水华问题,应用Aquatox模型对洱海水环境进行模拟,确立了一套适用于洱海生态系统的特征参数,并将模拟结果与实测数据进行验证.验证结果表明模型较好地模拟了常规水质和藻类演替变化,与实际水环境状况大体吻合.以此为基础选取TN、TP和Chl.a指标对洱海营养物与富营养化状态的投入响应关系进行模拟研究.结果表明,洱海对于外界营养物输入比较敏感,对氮磷输入增减反应明显;外界氮磷的削减都对Chl.a含量有降低作用,TN的作用更加明显;氮磷的增加对于Chl.a含量都略有提升;同时调控氮磷具有协同作用,对Chl.a含量影响效果最明显;当水体TN浓度在0.34 mg/L的阈值以下水平,即洱海外源TN输入量削减比例达到43.3%以上时,藻类优势种由蓝藻变为硅藻,水体Chl.a含量大幅降低,有效抑制富营养化进程.