2014年夏季长江口有色溶解有机物(CDOM)的分布、光学特性及其来源探究

通过测定有色溶解有机物(CDOM)的吸收光谱、荧光光谱、溶解有机碳(DOC)浓度,探究了2014年夏季长江口CDOM的来源及河口混合行为。结合吸收系数a(355)、光谱斜率S275-295、比紫外吸光度SUVA254与盐度的关系,结果表明南港水道受黄浦江输入影响显著,北港水道由长江径流控制呈保守性混合行为,二者CDOM的物质结构性质较为相似。DOC的浓度可通过a(275)与a(295)模拟估算:ln[DOC]=4.94–0.87ln[a(275)]+0.90ln[a(295)],a(275)8.0 m–1;ln[DOC]=4.77–6.79ln[a(275)]+8.05ln[a(295)],a(275)≥8.0 m–1。模拟结果表明,在长江口及邻近海域,CDOM对DOC具有示踪意义。利用三维荧光光谱-平行因子分析(EEMs-PARAFAC)技术,可得到夏季长江口FDOM含有3个类腐殖质组分(C2,C4和C5)和3个类蛋白质组分(C1,C3和C6)。类腐殖质组分具有相似的来源及地球化学行为,且与a(355)及盐度存在显著相关性;类蛋白质组分则与a(355)及盐度之间无显著相关性,揭示其与区域内微生物的活动有关。     

东海典型水体的黄色物质光谱吸收及分布特征

水体中的有色可溶性有机物(又称"黄色物质")是遥感监测水质分类的主要参数之一,研究其光谱吸收性质具有重要的实际意义。东海海区受长江冲淡水等陆源输入的影响,水体浑浊,光学性质复杂,以往对该区域CDOM吸收特征的研究相对较少。利用"九○八"我国近海海洋光学调查航次数据,获得了2006-2007年四个季节东海水体样品CDOM的光谱吸收数据,建立了包括杭州湾高浑浊水体、长江冲淡水、外海水体等东海不同水体类型的CDOM光谱模型及其典型波段的吸收系数分布情况。发现近岸受陆源输入影响大的海区其光谱性质与外海有明显区别,主要体现为近岸尤其在杭州湾附近站点短波段吸收系数值非常高,而且随波长增加吸收系数曲线衰减迅速,同时还有一定的季节变化,外海站点短波段吸收值则明显要低。这反映了CDOM的陆源输入特性,愈向外受到海水的混合稀释作用愈显著,验证了CDOM可以作为近岸海水水质监测的重要参数。对该海区内CDOM的实测荧光性质进行了相关分析,结果表明CDOM荧光与吸收系数之间有很好的线性相关关系,可以作为荧光方法遥感监测该海区CDOM的有价值的参考。     

Planktonic and benthic microalgal community composition as indicators of terrestrial influence on a fringing reef in Ishigaki Island, Southwest Japan

Microalgal-based indicators were used to assess terrestrial influence on Shiraho coral reef of Ishigaki Island (Okinawa, Japan). A typhoon occurred on 4-5 August 2005 and sampling were made on three occasions thereafter (6, 8, and 11 August). Pre-typhoon sampling was conducted on 26 July. The typhoon-enhanced terrestrial discharges increased reef nutrient levels (e.g. average NO(3)(-)-N: 0.088mg/L pre-typhoon to 0.817mg/L post-typhoon). This elevated chlorophyll-a concentrations by four times and shifted phytoplankton composition (spectral class-based) from an initial dominance of diatoms and green microalgae to the dominance of bluegreen microalgae (cyanobacteria) and cryptophytes. Cyanobacteria later increased by more than 200% and accounted for as much as 80% of total chl-a ( approximately 0.29microg/L), possibly assisted by favorable nutrient availability. In outer reef waters, diatoms and green microalgae predominated whereas cyanobacteria and cryptophytes were nearly undetectable. Due to detrital decomposition and river discharge, the CDOM was much higher in the inner reef than in the outer reef. Benthic bluegreen microalgae were relatively more abundant in areas close to the river mouth and coastal agricultural fields. At these locations, nutrient concentrations were much higher due to river discharge and potentially significant groundwater discharge. Thus, phytoplankton and benthic microalgae can serve as indicators of terrestrial influence on coral reefs.     

藻源性湖泛发生过程CDOM变化对水色的影响

利用Y-型沉积物再悬浮发生装置模拟湖泛发生过程,分析其中有色可溶性有机物(CDOM)的变化特征及其对水色的影响.结果表明,藻类死亡过程消耗大量的氧气,水中溶解氧在短时间内消失殆尽,形成厌氧环境;并同时分解产生大量CDOM,使得水中CDOM显著增多.前期阶段,CDOM浓度随时间一直升高,第6 d时CDOM浓度达到峰值,CDOM在443 nm处的吸收系数ag(443)为4.48 m-1.水体黑度值(Fe S浓度)呈先增大后减小的趋势,最大值0.35 mmol/L同样出现在第6 d,整个过程中,CDOM浓度和黑度值变化趋势一致,ag(443)与水体黑度呈显著正相关.利用Hydrolight和CIE颜色匹配函数模拟不同梯度的CDOM对水色的影响,发现随ag(443)增大,水体颜色也逐渐由绿色转为棕色,整体向长波方向移动,水色逐渐变暗.因此,可以认为CDOM浓度变化是引起湖泛水体发黑的重要原因之一,可作为定量监测湖泛强度的指示性参数.     

Effects of precipitation on summer epilimnion thickness in tropical lakes

This study aimed to evaluate the importance of physical, chemical and biological factors (e.g., chlorophyll-a, and carbon) in the regulation of the summer epilimnion thickness (Zmix) of the tropical lakes focusing on trends of the current environmental variability. We sampled a set of tropical lakes from the middle Rio Doce lacustrine system (Minas Gerais, Brazil) for two consecutive summers. Besides Zmix, we analyzed the visible light attenuation (Kd_PAR), dissolved organic carbon (DOC), chlorophyll-a (Chl-a), total suspended solids (TSS), and fetch. We also analyze the quality of the dissolved organic matter (DOM) through colored dissolved organic matter (CDOM), spectral slope (S), DOC-specific absorbance (SUVA) and the ratio between the absorbance at 250 nm and 365 nm (E_250:365). Our results showed quite different results during the two years studied. In the summer of 2012, when there was higher rainfall, variations in Zmix were correlated to the optical factors associated with DOM quality, while in the drier summer of 2013 Chl-a, TSS and fetch were the variables that more explained Zmix. It suggests that DOM regulates the Zmix in the rainy periods in the studied tropical lakes and that control is determined by the balance between the DOM input (runoff) and output (such as photodegradation) of the aquatic systems. In reduced rain conditions (summer 2013), the factors responsible by chemistry photodegradation of DOM were predominant, and the organic matter was no longer controlling Zmix, which was driven by internal mixing, productivity, and the wind (Chl-a, TSS and fetch). In this study we showed how changes in precipitation might cause shifts in the factors that regulate the epilimnion thickness in tropical lakes.     

西太平洋冬季上层水体有色溶解有机物的分布和转化特征

为深入解析西太平洋溶解有机碳的生物地球化学过程,本研究于2015年12月至2016年1月,开展了西太平洋上层水体有色溶解有机物（CDOM）吸收光谱和荧光光谱特征研究。研究结果表明,西太平洋上层水体CDOM吸收系数a（320）变化范围为0.01~1.07 m-1,平均值为0.18 m-1;其较高值位于100~200 m水层,表层的海水相对含量较低,主要以有机物的光化学分解为主。采用PARAFAC分析CDOM三维荧光光谱特征,得到1种类腐殖质组分C2（252（310 nm）/405 nm）及2种类蛋白组分C1（224（276 nm）/335 nm）和C3（224（260 nm）/300 nm）,其中类腐殖质荧光组分占总荧光强度的11%~22%,蛋白质荧光组分占总荧光强度的78%~89%,蛋白质荧光中类色氨酸和类络氨酸组分对荧光强度的贡献相当。洋流在大尺度上控制西太平洋CDOM的分布特征,两流交界处和环流形成区域的CDOM相对含量较高,荧光信号较强。西太上层水体CDOM相对含量和荧光信息,与温度、盐度、DO和营养盐等理化因素之间的相关分析结果表明,CDOM主要成分类蛋白质的产生主要受上层水体初级生产过程控制。     

胶州湾海水中一氧化碳光致生成影响因素的研究

海水中的一氧化碳(CO)主要由溶解有色有机物(CDOM)光降解产生,且CO的光致生成量受到环境因素的影响。采集了胶州湾及其河口表层水样,通过实验室模拟实验开展了不同的环境条件(辐射强度、光照时间、温度、pH和盐度)以及水体中CDOM的来源对CO光致生成的影响研究。结果表明胶州湾海水中CO的光致生成速率随辐射强度的增强、水温的升高和水体pH的增大而增大;随着光照时间的延长、水体盐度的增大而逐渐减小;不同来源的CDOM对水体中CO的光致生成速率产生了不同的影响。     

太湖梅梁湾有色可溶性有机物的空间分布及光学行为

2004年3月对太湖梅梁湾有色可溶性有机物(CDOM)的吸收和荧光等光学行为进行研究,并由此探讨了CDOM的空间分布．结果表明,溶解性有机碳(DOC)的浓度在10．48-19．72 mg／L间变化,其均值为13．20±2．79 mg／L;CDOM在280 nm,355 nm和440 nm的吸收系数分别为18．73-31．91 m-1(平均值23．19±4．36 m-1)、4．63-7．14 m-1(平均值5．76±0．91 m-1)、1．45-2．99 m-1(平均值1．92±0．40 m-1);355 nm波长处CDOM的比吸收系数为0．34-0．57 L／(mg·m),平均值0．44±0．06 L/(mg·m);表征CDOM分子大小的比值a(250)／a(365)变化范围为5．05-7．55;355 nm的激发波长、450 nm的发射波长处的荧光值的变化范围0．79-3 04 nm-1(平均值1．69±0．77 nm-1)．CDOM吸收系数、DOC浓度、荧光强度的分析显示CDOM浓度呈现从河口往湾内、湾口递减的趋势．CDOM吸收与DOC浓度的相关性随波长的降低而增加,在短波部分存在明显的正相关．355 nm处的荧光值、DOC浓度与CDOM吸收系分别存在如下显著性正相关关系:Fn(355)=0．692(±0．135)a(355)-2．297(±0．786),a(355)=0．233(±0．061)DOC 2．690(±0．816)．280 -500 nm、280-360 nm、360-440 nm指数函数斜率S值分别为13．86±0．91、18．54±1．11、12．93±0．92μm-1,S值与比吸收系数之间存在显著的负线性相关关系,而与a(25)／a(365)值则存在显著的正线性关系．比吸收系数越大,a(250)／a(365)值和S值就越小,对应的CDOM分子量就越大,腐质酸的比例就越高．     

Modeling the timing of spring phytoplankton bloom and biological production of the Gulf of St. Lawrence (Canada): Effects of colored dissolved organic matter and temperature

The effects of colored dissolved organic matter (CDOM) from freshwater runoff and seasonal cycle of temperature on the dynamic of phytoplankton and zooplankton biomass and production in the Gulf of St. Lawrence (GSL) are studied using a 3-D coupled physical-plankton ecosystem model. Three simulations are conducted: (1) the reference simulation based on Le Fouest et al. (2005), in which light attenuation by CDOM is not considered and maximum growth rate (_μmax${\mu }_{\max }$) of phytoplankton and zooplankton are not temperature-dependent (REF simulation); (2) light attenuation by CDOM is added to REF simulation (CDOM simulation); and (3) in addition to CDOM, the _μmax${\mu }_{\max }$ of phytoplankton and zooplankton are regulated by temperature (CDOM+TEMP simulation). CDOM simulation shows that CDOM substantially reduces phytoplankton biomass and production in the Lower St. Lawrence Estuary (LSLE), but slightly reduces overall primary production in the GSL. In the LSLE, the spring phytoplankton bloom is delayed from mid-March to mid-April, resulted from light attenuation by CDOM. The CDOM+TEMP simulation shows that the spring phytoplankton bloom in the LSLE is further delayed to July, which is more consistent with observations. Annual primary production is reduced by 33% in CDOM+TEMP simulation from REF and CDOM simulations. Zooplankton production is the same in all three simulations, and export of organic matter to depth is reduced in CDOM+TEMP simulation, suggesting that temperature controlled growth of phytoplankton and zooplankton enhances the coupling between primary production and zooplankton production under the seasonal temperature cycle of the GSL.