Transport of Crustacean Larvae Between a Low-Inflow Estuary and Coastal Waters

The effectiveness of larval behavior in regulating transport between well-mixed, low-inflow estuaries and coastal waters in seasonally arid climates is poorly known. We determined the flux of an assemblage of benthic crustacean larvae relative to physical conditions between a shallow estuary and coastal waters on the upwelling coast of northern California (38°18′N, 123°03′W) from 29 to 31 March 2006. We detected larval behaviors that regulate transport in adjacent coastal waters and other estuaries for only two taxa in the low-inflow estuary, but they were apparent for taxa outside the estuary. Vertical mixing in the shallow estuary may have overwhelmed larvae of some species, or salinity fluctuations may have been too slight to cue tidal vertical migrations. Nevertheless, all larval stages of species that complete development in nearshore coastal waters were present in the estuary, because they remained low in the water column reducing seaward advection or they were readily exchanged between the estuary and open coast by tidal flows. Weak tidal flows and gravitational circulation at the head of the estuary reduced seaward transport during development for species that completed development nearshore, whereas larval release during nocturnal ebb tides enhanced seaward transport for species that develop offshore. Thus, nonselective tidal processes dominated larval transport for most species back and forth between the low-inflow estuary and open coastal waters, whereas in adjacent open coastal waters, larval behavior in the presence of wind-induced shear was more important in regulating migrations between adult and larval habitats along this upwelling coast.     

Numerical Modeling of the Long-Term Transport, Dispersion, and Accumulation of Black Sea Pollutants into the North Aegean Coastal Waters

This study investigates the long-term capacity of the North Aegean coastal systems to transport and store conservative pollutants that originate from the Black Sea. Emphasis is placed on modeling the dispersion and accumulation of a passive tracer that represents a Black Sea pollutant (BSP) substance that continuously discharges from the Dardanelles exit into the North Aegean, for a long period of time (16?years). The effects of the Black Sea water (BSW) inflows, meteorological forcing, and seasonal stratification are assessed with a 3D hydrodynamic model (Estuary, Lake and Coastal Ocean Model), after validation with available field data. The salinity, water temperature, and discharge from the Dardanelles Strait are taken to be seasonally varied. According to the authors' best knowledge, the present paper constitutes the first numerical modeling attempt in the literature that apart from the long-term hydrodynamic characteristics that have also been studied in previous works, a suitable tracer is introduced in order to predict the long-term fate, distribution, and accumulation of pollutants that originate from the Black Sea into the North Aegean coastal regions. The overall results of the present investigation indicate that the BSP concentration is very high at the coastal waters of Thassos, Samothraki, and Limnos islands, as well as along the mainland coastal waters between Alexandroupolis and Strymonikos Gulf, during summer and autumn when strong water column stratification occurs. In general, the BSP concentration in the North Aegean surface waters reaches considerable high values (47?C58?% of the initial pollutant concentration at Dardanelles inflow) within 16?years. Even for depths more than 500?m the BSP concentration is still remarkable, slightly increasing with time. The increase of the BSP concentration with respect to time at various depths (from free surface up to 750?m) is also investigated.     

示踪弥散试验影响因子分析

污染物质在含水介质中的运移,不仅受到水文地质条件的制约,而且受水化学动力条件的制约。示踪弥散试验常用于模拟地下水污染物质的运移研究,为污染预测和污染防治提供依据。试验选用NaCl为示踪剂,砂土为介质。在室内进行一维弥散试验,针对示踪剂的浓度、水力梯度、砂土干密度等影响因素,进行系统分析。结果表明,弥散系数与NaCl浓度、水力梯度成正比,与砂土干密度成反比。     

Observations of Thin Layers in Coastal Hawaiian Waters

Thin layers of plankton have been documented in a wide variety of environments. The growing body of observations indicates that these features are a critical component of marine ecosystem dynamics and functioning. In the past two decades, much of the research on thin layers was undertaken in temperate coastal waters. Here, we report the first known observations of thin layers of phytoplankton in tropical Hawaiian waters. We conducted an overnight shipboard study during which time we made high-resolution observations of physical and optical structure in the water column. During the overnight cruise, we observed the greatest number of thin layers in the early evening hours when thermal stratification was strongest and most persistent due to a combination of warm air and surface water, as well as light winds. A comparison of these observations with those from temperate regions leads us to hypothesize that the nature and persistence of the physical structure is very important in determining the persistence of thin layered structures. Because plankton biomass is generally lower in tropical regions, the heterogeneous aggregation of food in thin subsurface layers may be more critical to the marine ecosystem than it is in temperate regions where plankton are generally more abundant.     

Exchange of Nitrogen and Phosphorus Between a Shallow Lagoon and Coastal Waters

West Falmouth Harbor, a shallow lagoon on Cape Cod, has experienced a threefold increase in nitrogen load since the mid- to late 1990s due to input from a groundwater plume contaminated by a municipal wastewater treatment plant. We measured the exchange of nitrogen and phosphorus between the harbor and the coastal waters of Buzzards Bay over several years when the harbor was experiencing this elevated nitrogen load. During summer months, the harbor not only retained the entire watershed nitrogen load but also had a net import of nitrogen from Buzzards Bay. During the spring and fall, the harbor had a net export of nitrogen to Buzzards Bay. We did not measure the export in winter, but assuming the winter net export was less than 112 % of the load, the harbor exported less than half of the watershed nitrogen load on an annual basis. For phosphorus, the harbor had a net import from coastal waters in the spring and summer months and a net export in the fall. Despite the large increase in nitrogen load to the harbor, the summertime import of phosphorus from Buzzards Bay was sufficient to maintain nitrogen limitation of primary productivity during the summer. Our findings illustrate that shallow systems dominated by benthic producers have the potential to retain large terrestrial nitrogen loads when there is sufficient supply of phosphorus from exchange with coastal waters.     

Contrasting Bacterial Dynamics in Subtropical Estuarine and Coastal Waters

Seasonal succession and composition of both attached and free-living bacterial communities were studied in subtropical estuarine and coastal waters with contrasting hydrographic conditions. A higher abundance of attached bacteria was recovered in the estuarine waters containing high concentrations of dissolved organic carbon (DOC) resulting from the freshwater discharge in the adjacent Pearl River, and Proteobacteria, including ??-, ??-, and ??-groups, predominated the attached community at both stations. Free-living bacterial communities at both stations showed higher diversity and lower seasonality than their attached counterparts, and ??-Proteobacteria accounted for the highest proportion at both stations. Redundancy analysis (RDA) demonstrated that, in addition to the obvious temperature effects, DOC and microphytoplankton (>20???m Chl a) drive the temporal variation of attached bacteria at the estuarine and coastal stations, respectively. On the other hand, picophytoplankton (<2???m Chl a) and dissolved oxygen concentration explained most of the free-living bacterial community succession at the estuarine station, while those at the coastal station were associated with micro- and picoplankton (Chl a fractions of <2 and >20???m). These findings suggest that temperature and bottom?Cup effects play a more important role for the spatial?Ctemporal variations of both attached and free-living bacterial communities in the subtropical estuarine and coastal waters.     

中国近海海面地形的计算与研究

介绍了海面地形的研究现状,并根据几何水准求得了中国近海的海平面倾斜及其精度.给出应用水文资料计算中国近海海面地形的公式及其计算结果.探讨了由球函数模型计算中国近海海面地形的理论和方法,并对不同方法进行了比较,得出了一些有益的结论.     

汕头近岸海域表层沉积物粒度特征及其输运趋势

对汕头近岸海域70个站位表层沉积物作了粒度分析和粒度参数计算,以探讨沉积物粒度分布特征。分析结果显示,研究区表层沉积物可划分为9种底质类型,以黏土质粉砂（YT）、砂质粉砂（ST）和砂-粉砂-黏土（S-T-Y）为主;砾、砂、粉砂和黏土的平均含量分别为1.4％,29.2％,51.0％,18.4％。平均粒径在0.12~7.30 之间变化,平均值为5.53 ;分选系数、偏态和峰态值的变化范围分别为0.50~2.94,-0.65~0.30和0.63~2.67,对应的平均值为1.82,-0.02和1.11。根据粒度分析结果,结合系统聚类方法和因子分析方法将研究区分为四类沉积区,分别代表不同的沉积环境,并应用GSTA模型分析了沉积物净输运趋势。结果显示,在汕头港水深＜10 m的海区,径流来沙和海域来沙有在榕江入海口和近岸汇聚的趋势;水深＞10 m的海区,沉积物呈现出明显的沿海岸线东北向输运的特征;在柘林湾,沉积物主要表现为弱的由海岸/海岛向海湾输运的特征。粒径趋势模型所揭示的这种沉积物输运格局与研究区的物源和水动力状况较好吻合,可为研究区港口建设和航道管理的决策提供参考资料。     

Spatial, Temporal, and Human-Induced Variations in Suspended Sediment Concentration in the Surface Waters of the Yangtze Estuary and Adjacent Coastal Areas

To delineate temporal and spatial variations in suspended sediment concentration (SSC) in the Yangtze (Changjiang) Estuary and adjacent coastal waters, surface-water samples were taken twice daily from 10 stations over periods ranging from 2 to 12?years (total number of samples >28,000). Synoptic measurements in 2009 showed an increase in surface SSC from 0.058?g/l in the upper sections of the estuary to ??0.6?g/l at the Yangtze River turbidity maximum at the river mouth, decreasing seaward to 0.057?g/l. Annual periodicities reflect variations in the Yangtze discharge, which affect the horizontal distribution and transport of SSC, and seasonal winds, which result in vertical resuspension and mixing. Over the past 10?C20?years, annual surface SSC in the lower Yangtze River and the upper estuary has decreased by 55%, due mainly to dam construction in the upper and middle reaches of the river. The 20?C30% decrease in mean surface SSC in the lower estuary and adjacent coastal waters over the same period presumably reflects sediment resuspension, in part due to erosion of the subaqueous Yangtze Delta. SSCs in the estuary and adjacent coastal waters are expected to continue to decline as new dams are constructed in the Yangtze basin and as erosion of the subaqueous delta slows in coming decades.     

Nutrient-Replete Benthic Microalgae as a Source of Dissolved Organic Carbon to Coastal Waters

Dissolved organic carbon (DOC) flux dynamics were examined in the context of other biogeochemical cycles in intertidal sediments inhabited by benthic microalgae. In August 2003, gross oxygenic photosynthetic (GOP) rates, oxygen penetration depths, and benthic flux rates were quantified at seven sites along the Duplin River, GA, USA. Sediments contained abundant benthic microalgal (BMA) biomass with a maximum chlorophyll a concentration of 201 mg chl a m^?2. Oxygen microelectrodes were used to determine GOP rates and O₂ penetration depth, which were tightly correlated with light intensity. Baseline and ¹⁵N-nitrate amended benthic flux core incubations were employed to quantify benthic fluxes and to investigate the impact of BMA on sediment water exchange under nitrogen (N)-limited and N-replete conditions. Unamended sediments exhibited tight coupling between GOP and respiration and served as a sink for water column dissolved inorganic nitrogen (DIN) and a source of silicate and dissolved inorganic carbon (DIC). The BMA response to the N addition indicated sequential nutrient limitation, with N limitation followed by silicate limitation. In diel (light–dark) incubations, biological assimilation accounted for 83% to 150% of the nitrate uptake, while denitrification (DNF) and dissimilatory nitrate reduction to ammonium (DNRA) accounted for <7%; in contrast, under dark conditions, DNF and DNRA accounted for >40% of the NO₃ ^? uptake. The N addition shifted the metabolic status of the sediments from a balance of autotrophy and heterotrophy to net autotrophy under diel conditions, and the sediments served as a sink for water column DIN, silicate, and DIC but became a source of DOC, suggesting that the increased BMA production was decoupled from sediment bacterial consumption of DOC.     

福建东部近海生物中稀土元素的生态化学特征

在福建东部海域16个海湾采集了近海生物鱼、虾、贝壳、藻4大类26小类128个样品,用ICP-MS法测定15种稀土元素的含量,结果表明,轻、重稀土元素存在较大的分镏作用,明显富集轻稀土元素,即轻稀土元素的生物学效应更为明显,鱼类等近海生物稀土元素配分模式总体上与海水和世界页岩稀土元素配分模式接近。稀土元素沿福建东部海域食物链的迁移传递没有表现出明显的生物放大作用。     

海州湾近岸海域水质状况调查与风险评价

随着我国沿海经济的快速发展,人类活动强度不断加剧,对海洋生态系统的干扰和破坏不断加剧。为了解海州湾近岸海域水质状况,本文于2016年4月、9月对海州湾近岸海域表层海水的温度、盐度、pH值、悬浮物(SS)、溶解氧(DO)、化学需氧量(CODMn)、亚硝酸盐(NO2--N)、硝酸盐(NO3--N)、铵氮(NH4+-N)、活性磷酸盐(PO34--P)、铜、铅、锌、镉、石油类等指标进行了两次采样调查,应用分光光度法和ICP-MS等技术分析各指标;应用单因子法、富营养化指数法和有机污染指数法对该海域海水的质量状况进行了评价分析,以期为研究区环境预警、环境管理和保护提供依据。结果表明:研究海域表层海水中CODMn在4月均值为1. 34mg/L,9月为1. 22mg/L;石油类4月均值为0. 031mg/L,9月为0. 034mg/L;活性磷酸盐4月均值为0. 013mg/L,9月为0. 012mg/L;溶解无机氮4月均值为0. 34mg/L,9月为0. 16mg/L; CODMn、石油类、活性磷酸盐、溶解无机氮的质量浓度大致呈现出由西南部向东北部海域降低的趋势,且无机氮总体浓度水平较高,为该海域主要的污染物。根据营养化评价模式和有机污染指数计算结果,本研究认为海州湾近岸海域表层水质总体营养水平较高,处于氮限制的潜在性富营养水平,有机污染程度属于Ⅱ级,水质已受到污染。     

The Response of Macrobenthic Communities to Environmental Variability in Tropical Coastal Waters

The relative contributions of spatial and temporal fluctuations are different in shaping natural communities in a tropical coastal/estuarine system. Understanding how coastal communities respond to these fluctuations is still equivocal, and thus, available data are rare. Here, multiple analytical approaches were used to identify key spatial and temporal factors, and to quantify their relative roles in shaping a macrobenthic community through space (contamination degree, physical parameters, and sediment characteristics) and time (climatic factors, season, and year). A dataset of eight sampling times was analyzed over a period of 2 years, in which macrobenthic species abundances were sampled. A total of 33 species were identified, including 18 bivalves, 5 gastropods, and 4 crustaceans. The other taxa were less diverse. The results show that there were no significant temporal changes of macrobenthic community structure, but spatial changes were significant and synchronized with environmental factors (i.e., sediment characteristics, water depth, and the distance from anthropogenic sources). This study demonstrates that spatial factors played a primary role in structuring of macrobenthic assemblages, whereas the influence of temporal factors appeared less across geographically distinct sites. Thus, temporal variation of a coastal macrobenthic community appears to be controlled by partly different processes at different scales.     

基于染色示踪的膜下滴灌棉田水盐运移规律

采用亮蓝FCF染色示踪剂, 研究膜下滴灌条件的水盐运移规律; 分别在灌溉前、灌溉中和灌溉后等不同时间段共开挖13个时刻的剖面, 观察膜下滴灌湿润面的运移情况; 以10 cm间隔的网格, 用MP406土壤水分探测器原位测定3 120个点的土壤体积含水率, 同时取1 430份土样, 利用1∶5土水比浸提法测定土壤盐分; 并利用WATCHDOG气象站监测研究区气象要素.结果表明: 染色示踪能直观表征土壤水盐运动轨迹; 膜下滴灌条件下, 垂直滴灌带方向土壤水流呈点源入渗特征、沿滴灌带方向近似呈线源入渗特征; 现行灌溉模式下, 壤质砂土湿润锋横向运移速率约为8 cm/h; 滴灌对滴头附近土体有一定洗盐效果, 未覆膜区域地表土体出现盐分积累; 灌水时间越长, 湿润锋越深, 横向扩展速率接近无作物小区(8 cm/h); 从土壤水合理利用角度考虑, 满足研究区一膜一带四行的种植模式和土质的单次合理灌水量应为29.4~69.8 mm.      

山东半岛东部海域悬浮体分布季节变化及其冬季输送通量研究

山东半岛东部近岸海域流系和水团要素季节变化显著,沉积动力环境特殊,发育有剖面形状独特的泥质沉积体。基于两个年度的夏、冬季山东半岛东部近岸海域水体温度、浊度、悬浮体浓度和海流等调查资料,分析了水团要素分布季节变化特征,并结合研究区域冬季海流和余流分布特征,计算了冬季经山东半岛东部近岸海域向南输送的悬浮体净通量。结果表明:山东半岛东部近岸海域悬浮体分布受沿岸流、黄海冷水团和黄海暖流等流系季节变化的影响存在显著季节变化。夏季,水体垂向层结和黄海冷水团均可抑制悬浮体垂向和东西向扩散。与以往的研究有所不同的是,冬季大量悬浮体可穿越沿岸流与黄海暖流形成的海流切变锋面,进入黄海暖流向北输送,海流切变锋的屏障作用会随着黄海暖流的减弱或东移而削弱。每年冬季经山东半岛东部近岸海域输送的悬浮体占渤海海峡向外海输送的悬浮体年净通量的3.22%~9.10%,冬季的悬浮体输送量较大,占冬季渤海海峡向外海输送的悬浮体年净通量的6.84%~19.38%。     

Surface Water Metabolism Potential in Groundwater-Fed Coastal Waters of Hawaii Island,USA

Submarine groundwater discharge (SGD) has become increasingly recognized as an important source of freshwater and nutrients to coastal waters worldwide. Although groundwater nutrients have been found to cause algal blooms in many temperate coastal waters, little is known about the biological response to these nutrients in the tropics. On the leeward coast of Hawaii Island, SGD is the dominant freshwater and nutrient source to coastal waters. Kiholo Bay, HI and Kaloko-Honokohau National Historical Park, HI are two nearshore regions with well-documented SGD with high nutrient concentrations; however, little is known about how biological processes within the surface waters respond to these inputs. This study examined how potential gross primary production (pGPP), respiration (RESP), and potential metabolism (pMET) within surface waters differed inside and outside of groundwater plumes at these two sites and between wet and dry seasons. pGPP and RESP were both significantly higher within groundwater plumes, suggesting that SGD stimulated these biological processes; however, RESP responded to a much greater extent than pGPP, resulting in heterotrophic surface waters. RESP also varied seasonally, with greater rates during the dry season compared to the wet one; pGPP did not vary seasonally. Autotrophic conditions were found within groundwater plumes at Kiholo Bay, while heterotrophic conditions were found within them at Kaloko-Honokohau and were greater during the dry season. Overall, our results show that coastal biological processes respond to SGD and that their responses vary over short spatial and temporal scales.     

Environmental Influences on Faecal Indicator Organisms in Coastal Waters and Their Accumulation in Bivalve Shellfish

Shellfish production areas are often located in shallow estuarine and coastal systems impacted by fluxes of faecal indicator organisms (FIOs) that exhibit extreme spatial and temporal variability. FIO abundance and distribution in the marine environment are determined by the combined effects of light intensity, water mixing, sewage content and suspended particulate matter. Favourable conditions for FIO survival are low solar radiation, low temperature, low salinity, low densities of micro-predators and high levels of organic matter. Rainfall is the parameter most commonly associated with peak levels of FIOs. Resuspension of contaminated sediments in the water column dominates FIO distribution in shallow and depositional estuaries during storm conditions. Water/flesh FIO ratios may differ between shellfish growing waters because salinities and water temperatures also influence filter-feeding activity. Data are lacking on the role of biological processes on FIOs uptake and clearance in shellfish, particularly during periods of good water quality. FIO accumulation is usually of higher magnitude in mussels and cockles than in oysters and surf clams. It is proposed that differences in FIO accumulation rates are associated with the biological activity and the position of shellfish in the water column in relation to the location of impacting pollution sources. Accurate information on catchment hydrology, land uses, FIO loads from sewerage-related sources and livestock production areas are required to adequately characterise the microbiological status of shellfisheries.     

Technogenic Radioactivity of Waters in the Central Arctic Basin and Adjacent Water Areas

Doklady Earth Sciences - The contemporary radiation situation in the Arctic Basin and Russian Arctic seas is assessed on the basis of data from 2013 to 2017. Statistically significant differences...