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81.
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. 相似文献
82.
Variability of the apparent quantum efficiency of CO photoproduction in the Gulf of Maine and Northwest Atlantic 总被引：1，自引：0，他引：1
The photochemical oxidation of colored, dissolved organic matter (CDOM) is important for carbon cycling in the ocean. This oxidation process produces a number of products, including carbon monoxide (CO). While the photochemical production efficiency of CO (apparent quantum yield, AQY, defined in terms of CDOM absorbance) has been reported to be similar for many water types, a full evaluation of the observed natural variability in CO AQY requires additional study. Here we use a polychromatic irradiation system to determine twenty AQY spectra at sea on fresh samples ranging from the near coastal waters of the Gulf of Maine to the offshore waters of the Northwest Atlantic. Despite the geographic variability of these marine samples the AQY of CO production in the Gulf of Maine and Northwest Atlantic exhibited only a small degree of variability, none of which was not correlated with measured environmental parameters. Consequently, a single aggregate AQY spectrum λ = e(−(9.134+0.0425(λ−290)))+e(−(11.316+0.0142(λ−290))) was found to adequately represent the entire data set. Significantly, the accuracy of an AQY spectrum determined using this multispectral/statistical technique was confirmed with data obtained from a monochromatic irradiation technique on a single open ocean sample. Taken together, the AQY spectra determined in this study were similar in magnitude and shape to those previously published for marine samples and, overall, were somewhat lower than those previously reported for freshwater studies. 相似文献
83.
84.
Catherine D. Clark Warren J. De Bruyn Charlotte M. Hirsch Paige Aiona 《Marine pollution bulletin》2010,60(12):2284-2288
Hydrogen peroxide is photochemically produced in natural waters. It has been implicated in the oxidative-induced mortality of fecal indicator bacteria (FIB), a microbial water quality measure. To assess levels and cycling of peroxide in beach waters monitored for FIB, diel studies were carried out in surf zone waters in July 2009 at Crystal Cove State Beach, Southern California, USA. Maximum concentrations of 160–200 nM were obtained within 1 h of solar noon. Levels dropped at night to 20–40 nM, consistent with photochemical production from sunlight. Day-time production and night-time dark loss rates averaged 16 ± 3 nM h−1 and 12 ± 4 nM h−1 respectively. Apparent quantum yields averaged 0.07 ± 0.02. Production was largely dominated by sunlight, with some dependence on chromophoric dissolved organic matter (CDOM) levels in waters with high absorption coefficients. Peroxide levels measured here are sufficient to cause oxidative-stress-induced mortality of bacteria, affect FIB diel cycling and impact microbial water quality in marine bathing waters. 相似文献
85.
Zhi-Ping Mei François J. Saucier Vincent Le Fouest Bruno Zakardjian Simon Sennville Huixiang Xie Michel Starr 《Continental Shelf Research》2010
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) 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 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. 相似文献
86.
Xiaomin ZHU Jianhua LI Qinghui HUANG Fan YANG 《中国地球化学学报》2006,25(B08):265-265
Chromophoric dissolved organic matter （CDOM）, one of the important components in freshwater and seawater ecosystems, plays a role in underwater light absorption and primary productivity. The Lake Beihu was a part of the North Branch of the Yangtze （Changjiang） River estuary in the past, but now the Lake Beihu has become the biggest manmade brackish lake in East China. The lake is a unique brackish ecosystem, however, little study deals with the fate of CDOM in it and whether this type of lake ecosystem will face eutrophication problem. This paper focuses on the transformation of CDOM, and the impact of microbe and light in the Lake Beihu. Microbial production and natural photobleaching simulative experiment was done on water samples from the Lake Beihu, yielding the following results. Water samples were collected from the Lake Beihu in May 2006. The filtrates through Whatman GF/F filters and polycarbonate membranes （μm） were exposed to microbe and microbe plus light condition, respectively. Three-dimensional excitation emission matrix （3-DEEM） fluorescence spectra were analyzed. It was shown that the amount of CDOM increased with time in the microbe exposure experiment, which means that microbes may play an important role in the production of CDOM instead of degrading CDOM. The .productivity was enhanced with increasing temperature, e.g. the value of UV260 increased by 62.4% in 4.5 days at 30℃, 26.9% at 20℃, 5.0% at 10℃. In addition, photobleaching was observed in the study as other papers reported. With the impact of microbes, the fluorescence signal of fulvic acid became stronger as the time went by. At 30℃, the fulvic acid fluorescence, which was expressed by QSU, increased by 35%-39%. 相似文献
87.
利用光学遥感反演盐度,可以充分利用遥感数据的空间代表性,以及目前高分率遥感数据的高时空精度。本文利用MERIS(Medium Resolution Imaging Spectrometer)300 m数据,以干旱区的博斯腾湖(博湖)为例,探讨了光学遥感数据反演低盐湖泊水体盐度的可行性。结果显示:在开都河入流影响的博湖西南角,存在光学遥感反演盐度利用的黄色物质(CDOM)与盐度的反比关系,但相关性不高,而且在博湖区域不同时间、不同区域CDOM与盐度的关系都不同。博湖盐度低于3 g·L-1,而遥感数据计算盐度的精度约为1.1 psu,因而用光学遥感数据计算博湖盐度的误差太大。博湖本身CDOM与盐度关系的时空异质性以及相关性不高,目前光学遥感反演精度有限,因此,在博湖用光学遥感数据反演整个湖区的盐度有困难。用光学数据反演水体盐度要求盐度足够高,盐度和CDOM存在梯度,并满足CDOM扩散守恒,因此用光学遥感反演低盐湖泊水体盐度较为困难。 相似文献
88.
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 总被引：3，自引：0，他引：3
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。 相似文献
89.
Colored Dissolved Organic Matter (CDOM) is one of important ocean color factors. In the background of “Jiangsu Coastal Development”, it is important to monitor the water quality and pollution status of coastal waters by analyzing its spatial and temporal distribution characteristics with remote sensing data. This paper was based on the high temporal resolution of Geostationary Ocean Color Imager (GOCI) image downloaded from Korea Ocean Satellite Center. The temporal-spatial distribution of CDOM in Jiangsu coastal waters was analyzed on daily, weekly and monthly time scales from April, 2011 to May, 2016. CDOM in Jiangsu coastal waters are mainly terrigenous, and higher inshore than that of offshore. The monthly average concentration of CDOM in the western coast of the South Yellow Sea was 0.167~0.201 m-1, and those of central and southern regions were 0.086~0.187m-1. The maximum values were outside the maximum turbidity zone of the Yangtze River Estuary, which was 0.180~0.206 m-1 (absorption coefficient at 440 nm). The diurnal variation of CDOM in near shore waters was found to coincide with the change of tide, which decreased at first and then increased in the sea area. By fitting the monthly mean using cosine function, significantly cyclical variation of mean CDOM was found in the South Yellow Sea. The central region of the South Yellow Sea waters fitting coefficient was 0.823. Affected by the Yellow Sea cold water mass, the sub-regions of the South Yellow Sea changed seasonally, whose CDOM concentration in winter and spring was higher than that in summer and autumn. Because of Changjiang Diluted Water and other water masses, seasonal variation of the Yangtze River Estuary was contrary to that of the South Yellow Sea. On monthly scale, CDOM concentration was positively correlated with total suspended matter, with correlation coefficient r being 0.72. The trend of the central and southern region was more significant. 相似文献
90.
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。 相似文献