A Kalman Filter Approach to Realize the Lowest Astronomical Tide Surface

In this paper , we present a novel Kalman filter approach to combine a hydrodynamic model-derived lowest astronomical tide (LAT) surface with tide gauge record-derived LAT values. In the approach, tidal water levels are assimilated into the model. As such, the combination is guided by the model physics. When validating the obtained “Kalman-filtered LAT realization” at all tide gauges, we obtained an overall root-mean-square (RMS) difference of 15.1 cm. At the tide gauges not used in the data assimilation, the RMS is 17.9 cm. We found that the assimilation reduces the overall RMS difference by ～ 31% and ～ 22%, respectively. In the Dutch North Sea and Wadden Sea, the RMS differences are 6.6 and 14.8 cm (all tide gauges), respectively. Furthermore, we address the problem of LAT realization in intertidal waters where LAT is not defined. We propose to replace LAT by pseudo-LAT, which we suggest to realize similarly as LAT except that all water level boundary conditions and assimilated tidal water levels have to be enlarged by a constant value that is removed afterward. Using this approach, we obtained a smooth reference surface for the Dutch Wadden Sea that fits LAT at the North Sea boundary within a few centimeters.     

基于卫星高度计资料提取浙江近海的潮汐信息

利用Topex/Poseidon(T/P)、Jason-1和Jason-2卫星24a的原始轨道及6a的变轨轨道高度计资料,对浙江近海区域内进行潮汐调和分析,得到8个主要分潮(Q_1、O_1、P_1、K_1、N_2、M_2、S_2和K_2)的调和常数.比较卫星轨道交叉点处潮汐调和常数结果显示,8个分潮总体综合误差在原始轨道,变轨轨道及原始轨道与变轨轨道交叉点处的和方根RSS值分别为3.16、7.02、5.54cm;用卫星高度计资料及31个近岸验潮站得到的潮汐分布与21个验潮站资料结果进行比较,M_2、S_2、N_2、K_1和O_1主要分潮的多点向量均方根偏差分别为4.32、3.64、1.97、2.61、1.83 cm;本研究结果与前人数值模拟结果比较显示M2、S2分潮在对比点处的多点向量均方根偏差在11、8 cm左右,最后给出了浙江近岸及近海区域更为精确的5个主要分潮(M_2、S_2、N_2、K_1和O_1)的同潮图.     

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.     

Behaviour of colloidal trace metals (Cu, Pb and Cd) in estuarine waters: An approach using frontal ultrafiltration (UF) and stripping chronopotentiometric methods (SCP)

The frontal cascade ultrafiltration (UF) technique in conjunction with stripping chronopotentiometry (SCP) has been evaluated for determining the colloidal distribution of Cu, Pb and Cd in estuarine waters. Metallic concentrations in seven size fractions (0.45 μm–0.22 μm; 0.22 μm–300 kDa; 300–50 kDa; 50–30 kDa; 30–10 kDa; 10–5 kDa; <5 kDa) were determined with the aim to investigate their changes along the salinity gradient of the Penzé system (NW France). These data, completed by analysis of the total dissolved metals at 10 stations over the whole freshwater–seawater mixing zone, provided some insights in the removal and addition processes that affect Cu, Pb and Cd in estuaries.     

Characterizing sources of groundwater to a tropical coastal lagoon in a karstic area using radium isotopes and water chemistry

Radium isotopes (²²³Ra, ²²⁴Ra, ²²⁶Ra, and ²²⁸Ra) and water chemistry were used to identify two chemically distinct sources of submarine groundwater discharge (SGD) in Celestún Lagoon, Yucatán, Mexico. Low salinity groundwater discharging from springs within the lagoon has previously been identified and extensively sampled for nutrient concentrations. However, a second type of groundwater discharging into the lagoon was detected during this study using radium isotope activity measurements. This second type of groundwater is characterized by moderate salinities (within the range of lagoon salinities) and very elevated radium activities in comparison to the low salinity groundwater, mixed lagoon water, and seawater. Further analysis showed that the two types of groundwater also have distinct chloride, strontium, and sulfate ratios, along with slightly different nutrient concentrations. Groundwater discharge occurs through large and small springs scattered throughout the lagoon, and both types of groundwater were detected discharging from one of the larger springs. The relative proportions of low salinity groundwater and brackish high radium groundwater varied over the tidal cycle. In order to better understand the relative contributions of each type of groundwater to the lagoon, a three end-member mixing model based on the distinct chemical and isotopic compositions of both types of groundwater and of seawater was used to estimate the distribution of each water type throughout the lagoon in different seasons. This study suggests that substantial groundwater discharge to the lagoon can occur during both dry and rainy seasons. The presence of two groundwater sources has implications for monitoring and protection of the Celestún Lagoon Biosphere Reserve, since the two sources may have different susceptibilities to anthropogenic contamination depending on their respective recharge area and recharge rates.     

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CONTRIBUTION OF NITROGEN SPECIES AND PHOSPHORUS FRACTIONS TO STREAM WATER QUALITY IN AGRICULTURAL CATCHMENTS

The contribution from agricultural catchments to stream nitrogen and phosphorus concentrations was assessed by evaluation of the chemical composition of these nutrients in agricultural runoff for both surface and subsurface flow pathways. A range of land uses (grazed and ungrazed grassland, cereals, roots) in intensive agricultural systems was studied at scales from hillslope plots (0.5 m²) to large catchment (>300 km²). By fractionating the total nutrient load it was possible to establish that most of the phosphorus was transported in the unreactive (particulate and organic) fraction via surface runoff. This was true regardless of the scale of measurement. The form of the nitrogen load varied with land use and grazing intensity. High loads of dissolved inorganic nitrogen (with >90% transported as NH₄-N) were recorded in surface runoff from heavily grazed land. In subsurface flow from small (2 km²) subcatchments and in larger (>300 km²) catchments, organic nitrogen was found to be an important secondary constituent of the total nitrogen load, comprising 40% of the total annual load.     

深圳海域弧菌种类组成、数量分布及其与环境因子的关系研究

研究了深圳海域2008年4月、9月的水体弧菌数量、种类组成及其分布,探讨了弧菌总数及各优势类群的数量分布与环境因子间的相关关系。结果表明:弧菌总数分布具有季节性,东部海域春季(4月)的弧菌数量高于秋季(9月)的,其均值分别为1.50×10⁴ ,8.89×10² CFU/cm³;在西部海域秋季的略高于春季的,其均值分别为5.09×10²,2.66×10² CFU/cm³;弧菌数量最高值出现在大亚湾(4.40×10⁴ CFU/cm³)。弧菌的优势类群具有季节性分布特征:春季特有的优势类群有Vibrio gigantis类似种和V. splendidus类似种,秋季特有的优势类群有V. natriegens类似种;V. alginolyticus类似种是两个季节共有的优势类群,其数量春季高于秋季的。弧菌种类、数量与海水温度、盐度及细菌总数、Chl-a等环境因子有一定的相关性,其中盐度为弧菌种类及数量分布的主要影响因子。     

胶州湾东北部养殖海区环境质量状况及分析

基于2006年2月、5月、8月、11月胶州湾东北部养殖海区现场调查结果,采用单因子指数、富营养化指数、有机污染指数对环境状况进行了分析评价。结果表明:该海域主要受到无机N、P污染;COD在夏、秋季符合一类,但在冬、春季只达到国家二类海水水质标准;DO全部符合国家一类海水水质标准。通过站位间的比较发现,东北部沧口水域环境质量最差,全年处于富营养化状态,有机污染介于轻度到严重污染之间。红岛附近水质较好,不存在有机污染,只有春、秋季达到富营养化水平。研究结果显示该海域主要受陆源污染,且与现有污水处理不能有效去除无机N、P营养盐有关。     

福建沿海文昌鱼的分布及其资源保护对策

采用现场采样方法对福建沿海文昌鱼(Branchiostoma balcheri)的分布和资源状况进行了调查,为文昌鱼的保护提供依据。全省19个海区潮间带均未捕获文昌鱼;12个海区的潮下带浅海定量调查中,仅5个海区采集到文昌鱼。东山湾海区文昌鱼密度最高,为41.67尾/m2,其次是厦门十八线海区,为14.5尾/m2,厦门南线海区和黄厝海区分别为5.39尾/m2和4.71尾/m2,泉州大港海区仅捕到1尾,闽江口3个海区均未捕获。所获文昌鱼年龄大多为1龄,占39.2%,2龄占23.5%,3龄占25.5%,其他(1龄以下、4龄、5龄及以上)占11.8%。与20多年前的历史资料相比,文昌鱼的分布区大为缩小,资源量大为降低,资源已濒临枯竭。必须加大对文昌鱼资源的保护力度,有必要增设文昌鱼自然保护区,并加强对文昌鱼保护区的管理。