秦山Ⅲ期核电站工程邻近水域叶绿素a的电布特征

根据 1 995年 1 0月至 1 996年 7月秦山 期核电站邻近水域生态调查资料 ,对叶绿素 a的分布特征进行研究。结果表明 ,该调查水域叶绿素 a含量低 ,表层叶绿素 a平均含量为 0 .2 93mg/m3,底层叶绿素 a平均含量为 0 .2 2 2 mg/m3。叶绿素 a含量的季节变化明显 ,秋季最高 ,其它依次为夏季、春季、冬季。与该水域过去的调查资料进行比较分析 ,发现叶绿素 a的含量有明显下降。     

山东半岛南部近岸海域富营养化状况的多元评价研究

于2006年至2007年分四个季度月对山东半岛南部近岸海域(35.5°~36.7°N,119.8°~121.3°E)的营养盐和叶绿素a进行了设站调查,分析了该海域上述因子时空分布特征,同时应用主成分分析(PCA)和潜在富营养化评价方法对该海域的富营养化状况进行了分析,初步确定了影响该海域富营养化状况的主要驱动因子。结果表明:(1)在时间分布上,总氮、总磷、活性磷酸盐、溶解态氮与总无机氮和活性硅酸盐的季节变化类似,均表现出秋冬季浓度较高而春夏季较低的趋势,而总磷、溶解态磷的浓度则在冬季最高,在夏秋季较低,叶绿素a浓度的季节变化趋势为春夏季较高,而冬季最低;该海域营养盐与叶绿素a浓度空间分布以胶州湾和丁字湾为中心,总体呈现出由近岸向离岸海域逐渐递减的趋势;(2)应用主成分分析对调查结果进行分析,结果显示10项调查指标(营养盐与叶绿素a)可以转换提取4个主成分,解释82.00%的结果。主成分综合得分可以作为富营养化程度的评价指标,据此得到调查海域富营养化状况的季节变化趋势由高到低依次为秋季、冬季、春季、夏季,总体呈现出以胶州湾和丁字湾为中心,沿岸及北部海域富营养化程度较高的格局;分析结果还表明总无机氮是该海区富营养化形成的主要驱动因子;(3)利用潜在富营养化评价方法对调查海域富营养化状况进行了初步分析,结果表明该海区仅于秋季表现为总体中度营养,在其他季节总体趋势均为贫营养,胶州湾与丁字湾附近海域在春秋季表现为磷限制潜在富营养化。主成分分析法较潜在富营养化评价方法更敏感,不仅能够定量表述海区富营养化状况,而且能够有效确定富营养化驱动因子。     

Nutrient concentrations and fluxes in the Changjiang Estuary during summer

In June 2003 and 2006 concentrations of nutrient were determined in the Changjiang Estuary. The data indicated that phosphate and nitrate did not behave conservatively in the estuary, but silicate behaved conservatively. An important mobilization of phosphate and nitrate was observed from the river up to halfway in the estuary. Both input flux (from river to estuary) and output flux (from estuary to coastal zone) of phosphate, silicate and nitrate were calculated from statistical interpretations of the salinity profiles. There was a large discrepancy between input and output fluxes of phosphate and nitrate. The river fluxes of silicate, phosphate and nitrate (f_r) are augmented 5.3%, 28.9% and 36.6% in June 2003 and 1.0%, 62.5%, 31.7% in June 2006 by internal inputs (f_i). The phosphate and nitrate fluxes are enhanced through the estuarine process, while silicate flux is unaltered. The authors present some long-term data for nutrient concentrations and the ratios of silicon to nitrogen to phosphorus in the Changjiang Estuary. Silicate level falled in the last two decades, while concentration of nitrate increased. Phosphate concentration had no significant change.     

长江口南汇边滩冲淤变化规律与机制

根据1842—2004年海图资料分析发现,南汇边滩存在近百年尺度的强烈冲刷—淤积旋回。长江主泓走南港或北港是造成冲刷期"北滩、东滩淤积,南滩、过渡带冲刷"或淤积期冲淤态势反相的主要原因;冲刷期内风暴强度和频数明显多于淤积期,造成冲刷期滩面叠置记忆的是暴风浪成因的"高滩冲刷、低滩淤积"的冲淤态势,而淤积期保存的是弱风浪成因的"高滩淤积、低滩冲刷"叠置增强的剖面特征。尽管三角洲整体冲淤态势的转变主要受流域来沙量的控制,但不同岸段受河口河势分水分沙作用、潮流和波浪等共同作用,明显存在此冲彼淤、冲淤动态调整等特征。已有的入海泥沙含量阈值研究以点代面或以局部代整体,这是造成阈值估算偏高的主要原因。2003年三峡水库开始蓄水后平均年输沙量154 Mt/a已低于低阈值184 Mt/a,但三角洲尚未如预测那样发生由净淤积向净侵蚀的转变。已有的河口水文观察资料显示,水体含沙量也未发生明显下降,这可能是潮控型三角洲潮流对泥沙在河口的再分配起主导作用,并可能由此延长三角洲冲淤转变对入海泥沙量减少的滞后。今后需进一步加强潮控型河口复杂过程的综合研究,提高对泥沙含量阈值估算和应对可能面临的海岸侵蚀及其相关的环境地质灾害的能力。     

Distribution and fluxes of suspended sediments in the offshore waters of the Changjiang (Yangtze) Estuary

The offshore waters of the Changjiang Estuary are the transitional areas where river-supplied water and sediment are transported to the sea, and material exchanges occur with the neighbored Hangzhou Bay and the Jiangsu waters. Field observations of currents and sediment properties were conducted to study temporal and spatial distributions of suspended sediments under various dynamical conditions. The high sediment concentrations were found to occur in the western and southern waters of the offshore, and the low concentrations occurred in the eastern and northern waters. This pattern of the suspended sediment concentration (SSC) distribution is obviously influenced by the runoff and tidal current. The significant difference of along-estuary SSC distribution indicates that the SSC is reduced gradually from the west to the east, and that in the spring tide is obviously higher than in the neap tide. The methods of mechanism analysis and equal-area grids were used to calculate the suspended sediment fluxes at the typical cross sections. It was found that 44 percent of total suspended sediments from the Changjiang River were deposited in the submarine delta, and more than 27 percent of sediments were transported southernly into the Hangzhou Bay, and only 9 percent of sediments was supplied and exchanged with the northern Jiangsu waters, and about 20 percent of sediments was delivered offshore to the sea.     

The role of macrophytes as a refuge and food source for the estuarine isopod Exosphaeroma hylocoetes ( )

The role of submerged macrophytes as refugia from fish predation and as possible food sources for the estuarine isopod Exosphaeroma hylocoetes ( Barnard, K.H., 1940) was investigated. Laboratory experiments tested the effectiveness of artificial vegetation, replicating submerged vegetation, in enabling isopods to elude selected fish predators Rhabdosargus holubi, Glossogobius callidus, Monodactylus falciformis and Clinus cottoides. Isopods preferentially hid in the vegetation (>90%), even in absence of fish. The predatory fish had varying success in finding isopods within the vegetation. Isopod mortality ranged from 2% (R. holubi) to a maximum of 87% (C. cottoides) within vegetation, depending on the fish predator present. Stable isotope and fatty acid analyses ruled out the submerged macrophyte Ruppia maritima and inundated fringing grasses as direct food sources, but highlighted the epiphytic biota (mainly diatoms) found on the submerged vegetation and sediments as more likely food sources. These findings are consistent with gut content analyses. The results suggest that the close association of E. hylocoetes with R. maritima is the result of the vegetation providing the isopod with a refuge against fish predation as well as areas of increased food availability.     

Influence of allochthonous organic matter on bacterioplankton biomass and activity in a eutrophic,sub-tropical estuary

Heterotrophic bacterial and phytoplankton biomass, production, specific growth rates, and growth efficiencies were studied in the Northern region of the Cananéia–Iguape estuarine system, which has recently experienced an intense eutrophication due to anthropogenic causes. Two surveys were carried out during spring and neap tide periods of the dry season of 2005 and the rainy season of 2006. This region receives large freshwater inputs with organic seston and phosphate concentrations that reach as high as 1.0 mg l⁻¹ and 20.0 μM, respectively. Strong decreasing gradients of seston and dissolved inorganic nutrients were observed from the river/estuary boundary to the estuary/coastal interface. Gradients were also observed in phytoplankton and bacterial production rates. The production rates of phytoplankton were 5.6-fold higher (mean 8.5 μg C l⁻¹ h⁻¹) during the dry season. Primary production rates (PP) positively correlated with salinity and euphotic depth, indicating that phytoplankton productivity was light-limited. On the other hand, bacterial biomass (BB) and production rates (BP) were 1.9- and 3.7-fold higher, respectively, during the rainy season, with mean values of up to 40.4 μg C l⁻¹ and 7.9 μg C l⁻¹ h⁻¹, respectively. Despite such a high BP, bacterial abundance remained <2 × 10⁶ cells ml⁻¹, indicating that bacterial production and removal were coupled. Mean specific growth rates ranged between 0.9 and 5.5 d⁻¹. BP was inversely correlated with salinity and positively correlated with temperature, organic matter, exopolymer particles, and particulate-attached bacteria; this last accounted for as much as 89.6% of the total abundance. During the rainy season, BP was generally much higher than PP, and values of BP/PP > 20 were registered during high freshwater input, suggesting that under these conditions, bacterial activity was predominantly supported by allochthonous inputs of organic carbon. In addition, BB probably represented the main pathway for the synthesis of high-quality (low C:N) biomass that may have been available to the heterotrophic components of the plankton food web, particularly nanoheterotrophs.     

Short-term (≤2 yrs) estuarine mudflat and saltmarsh sedimentation: High-resolution data from ultrasonic altimetery, rod surface-elevation table, and filter traps

Rates of short-term (up to 2 years) bed elevation change and sedimentation from mudflats to salt marshes were measured in a rapidly infilling macrotidal estuary using an original combination of three high-resolution techniques: an ultrasonic altimeter, the Rod Surface-Elevation Table (RSET) method, and filter traps. The Authie estuary is located on a straight, sand-rich coast and is undergoing rapid infill under the influence of flood-dominant tides reinforced by wave action. The estuarine sediment suite consists of both mud and sand derived from the sea, of sand derived from storm wave erosion of dunes lining the north bank of the estuary, and, to a much smaller extent, of mud from the river catchment. Bed elevation change and sedimentation rates show an expected increase with the duration of tidal flooding (hydroperiod) in both space and time. The estuarine bed sediment suite changes from sandy at the mouth to muddy within the low-energy inner estuary, where mudflats are rapidly accreting, paving the way for the formation of increasingly denser and mature salt marshes from the high-sedimentation pioneer zone to the upper marsh where annual sedimentation is very low. Recorded variability in rates of bed elevation change and sedimentation reflect the influence of estuarine macro-scale and local sediment transport and depositional processes in a macrotidal context dominated by high inputs of allochthonous sediments.     

Copper complexing ligands and organic matter characterization in the northern Adriatic Sea

The study on dissolved organic ligands capable to complex copper ions (L_T), surface-active substances (SAS) and dissolved organic carbon (DOC) in the Northern Adriatic Sea station (ST 101) under the influence of Po River was conducted in period from 2006–2008. The acidity of surface-active organic material (Ac_r) was followed as well. The results are compared to temperature and salinity distributions. On that way, the contribution of the different pools of ligands capable to complex Cu ions could be determined as well as the influence of aging and transformation of the organic matter. The L_T values in the investigated period were in the range of 40–300 nmol l⁻¹. The range of DOC values for surface and bottom samples were 0.84–1.87 mg l⁻¹ and 0.80–1.30 mg l⁻¹, respectively. Total SAS concentrations in the bottom layer were 0.045–0.098 mg l⁻¹ in equiv. of Triton-X-100 while those in the surface layer were 0.050–0.143 mg l⁻¹ in equiv. of Triton-X-100. The majority of organic ligands responsible for Cu binding in surface water originate from new phytoplankton production promoted by river borne nutrients. Older, transformed organic matter, possessing higher relative acidity, is the main contributor to the pool of organic ligands that bind copper in the bottom samples. It was estimated that 9% of DOC in surface samples and 12% of DOC in the bottom samples are present as ligands capable to complex copper ions.     

Surface evolution and carbon sequestration in disturbed and undisturbed wetland soils of the Hunter estuary,southeast Australia

The aim of this work was to quantify the soil carbon storage and sequestration rates of undisturbed natural wetlands and disturbed wetlands subject to restriction of tidal flow and subsequent rehabilitation in an Australian estuary. Disturbed and undisturbed estuarine wetlands of the Hunter estuary, New South Wales, Australia were selected as the study sites for this research. Vertical accretion rates of estuarine substrates were combined with soil carbon concentrations and bulk densities to determine the carbon store and carbon sequestration rates of the substrates tested. Relationships between estuary water level, soil evolution and vertical accretion were also examined. The carbon sequestration rate of undisturbed wetlands was lower (15% for mangrove and 55% for saltmarsh) than disturbed wetlands, but the carbon store was higher (65% for mangrove and 60% for saltmarsh). The increased carbon sequestration rate of the disturbed wetlands was driven by substantially higher rates of vertical accretion (95% for mangrove and 345% for saltmarsh). Estuarine wetland carbon stores were estimated at 700–1000 Gg C for the Hunter estuary and 3900–5600 Gg C for New South Wales. Vertical accretion and carbon sequestration rates of estuarine wetlands in the Hunter are at the lower end of the range reported in the literature. The comparatively high carbon sequestration rates reported for the disturbed wetlands in this study indicate that wetland rehabilitation has positive benefits for regulation of atmospheric carbon concentrations, in addition to more broadly accepted ecosystem services.