河口海岸三维水流数值模型中几种垂向坐标模式研究述评

回顾了近年来国内外河口、近岸海域三维斜压水流数值模式研究的进展,着重讨论了不同垂向坐标下三维水流模式的发展状况以及存在的问题。地形拟合坐标(σ坐标)模式可以很好地拟合床面地形和自由面,已在物理海洋学中被广泛使用。但在地形变化剧烈,尤其在密度层结效应明显的海域,σ坐标模式中的水平压强梯度力误差会引起伪密度流。寻求高精度的数值模式以及更加有效的拟合坐标变换将是值得努力的方向。     

舟山海域陆源溶解有机质变化及其对近岸羽状流的响应

2007年夏季在东海舟山海域河口锋区开展了陆源溶解有机质的调查研究。测定了有色溶解有机质(CDOM)在激发波长370 nm/发射波长460 nm处的荧光强度和在λ=355 nm处的吸收系数,用于代表陆源CDOM浓度,并测定了荧光指数以指示CDOM来源。结果表明,CDOM的荧光值和紫外吸收系数之间呈显著正相关性,陆源CDOM浓度大体有向海方向降低的趋势,但是纵向上存在一些"突跃"现象。在舟山海域东北角不时观测到表层水体含有高浓度的CDOM,但变异性很大,推测可能该海区受到长江口羽状流的影响。在连续观测站发现陆源CDOM浓度在低平潮时往往比高平潮时要高。河海水在混合过程中CDOM浓度与盐度呈显著的线性负相关关系。在低盐度的悬沙锋区(S<24)CDOM浓度明显低于理论稀释值,而在较高盐度的羽状锋区,CDOM浓度接近于理论稀释值。在盐度为24~31范围内,大部分水样的荧光指数在1.50上下波动,表明其中CDOM来源以陆地来源为主;在较低盐度(S<24)的水样中荧光指数在1.70至1.90以上,表明CDOM以海洋来源为主,这与其陆源组分在高浊度的低盐度区存在显著的去除过程有关。研究表明,舟山海域水质存在着显著的变异性,与近岸羽状流密切相关,陆源溶解有机质的分布特征对此有较好的响应。     

Elucidating the dynamics and mixing agents of a shallow fjord through age tracer modelling

The mixing agents and their role in the dynamics of a shallow fjord are elucidated through an Eulerian implementation of artificial tracers in a three-dimensional hydrodynamic model. The time scales of vertical mixing in this shallow estuary are short, and the artificial tracers are utilized in order to reveal information not detectable in the temperature or salinity fields. The fjord's response to external forcing is investigated through a series of model experiments in which we quantify vertical mixing, transport time scales of fresh water runoff and estuarine circulation in relation to external forcing.Using age tracers released at surface and bottom, we quantify the time scales of downward mixing of surface water and upward mixing of bottom water. Wind is shown to be the major agent for vertical mixing at nearly all depth levels in the fjord, whereas the tide or external sea level forcing is a minor agent and only occasionally more important just close to the bottom. The time scale of vertical mixing of surface water to the bottom or ventilation time scale of bottom water is estimated to be in the range 0.7 h to 9.0 days, with an average age of 2.7 days for the year 2004.The fjord receives fresh water from two streams entering the innermost part of the fjord, and the distribution and age of this water are studied using both ageing and conservative tracers. The salinity variations outside this fjord are large, and in contrast to the salinity, the artificial tracers provide a straight forward analysis of river water content. The ageing tracer is used to estimate transport time scales of river water (i.e. the time elapsed since the water left the river mouth). In May 2004, the typical age of river water leaving the fjord mouth is 5 days. As the major vertical mixing agent is wind, it controls the estuarine circulation and export of river water. When the wind stress is set to zero, the vertical mixing is reduced and the vertical salinity stratification is increased, and the river water can be effectively exported out of the fjord.We also analyse the river tracer fields and salinity field in relation to along estuary winds in order to detect signs of wind-induced straining of the along estuary density gradient. We find that events of down estuary winds are primarily associated with a reduced along estuary salinity gradient due to increased surface salinity in the innermost part of the fjord, and with an overall decrease in vertical stratification and river water content at the surface. Thus, our results show no apparent signs of wind-induced straining in this shallow fjord but instead they indicate increased levels of vertical mixing or upwelling during down estuary wind events.     

福建漳江口红树林保护区浮游植物群落的季节变化研究

于2001年1月～2003年1月对福建省漳江口红树林区水体浮游植物群落的季节变化进行了研究。结果表明,漳江口红树林区浮游植物以硅藻门种类为主,优势种为长菱形藻(Nitzschia longissima)和菱形藻(Nitzschia sp.1)等,同时出现多种裸藻、绿藻和甲藻。本次调查共鉴定到浮游植物31属87种(包括变种),其中硅藻门23属75种(包括变种),蓝藻门3属3种,绿藻门1属4种,金藻门1属1种,甲藻门2属2种,裸藻门1属2种。浮游植物密度变化范围为2.78×104～1.14×106个/L,平均为3.51×105个/L,季节变化为双峰型。出现大量的底栖硅藻和淡水性藻类是该水域浮游植物的一个特点。浮游植物的组成和结构表明该水域水质较好。     

两株河口湿地耐盐石油降解菌的生物学特性及降解能力研究

从辽河口湿地污染土壤样品中分离筛选出2株高效石油降解茵lhk-2和lhk-10,经鉴定lhk-2为巴氏萄萄球菌(Staphylococcus pasteuri),lhk-10为嗜麦芽寡养单胞菌(Stenotrophomonasmaltophili).两株菌的石油降解能力研究结果表明,培养8d后,加菌组的石油烃降解率均在...     

Ecology of beach wrack in northern New England with special reference to Orchestia platensis

The northern New England beach wrack community with special reference to the cosmopolitan amphipod crustacean, Orchestia platensis, was examined at estuarine and open coastal habitats. Beach wrack was dominated by the plant genera Ascophyllum, Zostera, Spartina and Chondrus, and was most abundant during spring and late summer. Animal community numbers, biomass and frequency in fresh to moderately decomposed wrack were dominated by O. platensis throughout the year at all habitats; oligochaetes and Collembola were also important. The abundance of O. platensis showed high spatial and temporal variability, with low abundance generally associated with decreased amounts of wrack during colder months. An exception was the winter presence of the species at one estuarine habitat, in patchy aggregations within gravel-cobble refuges. The abundance of O. platensis averaged 1280 (0.04 m²)⁻¹, with a maximum of 7040 (0.04 m²)⁻¹. The life cycle of O. platensis is bivoltine, with summer-hatched young reaching maturity within 1 month. Laboratory studies indicate females with up to 4 broods (30 days)⁻¹, averaging 18 eggs brood⁻¹.Orchestia platensis is omnivorous, eating fresh plant tissue, live oligochaetes, Limulus eggs and diatom ‘fuzz’. The rate of laboratory consumption of algae and Zostera was 0.05 mg plant mg⁻¹ wet body weight day⁻¹. Presumptive predators of O. platensis are juvenile green crab, Carcinus maenus, and the earwig. Anisolabis maritima. The mobility, aggregation and aggressiveness of O. platensis assist the species in establishing and maintaining populations in the rigorous wrack habitat. The general competitive superiority of O. platensis over its congener, O. gammarella, and the co-occurrence of these species on both eastern and western Atlantic shores is discussed.     

闽江口段溶解态镉,铅和铜的收支平衡

利用潮输沙量的计算方法,估算了闽江口入海口内3个断面所包围区域溶解态镉、铅和铜的收支平衡,从而研究了这些重金属的河口行为。     

九龙江口红树林湿地与米草湿地的底栖生物

2004年冬季,在厦门海沧青礁和海沧大道东侧潮间带进行红树林湿地、互花米草湿地和普通滩涂湿地的底栖生物生态调查.调查结果:定量样品普通滩涂出现的种类、生物量比互花米草区和红树林区多,互花米草区底栖动物的栖息密度、种类多样性、丰度比红树林区高.     

长江口扁担沙动力地貌变化过程研究

河口浅滩不仅为人类提供宝贵湿地资源,而且是调控河势演变的重要因素。研究河口浅滩动力地貌演变规律对航道整治、湿地生态开发及岸堤防护等具有重要价值。本文利用最近150多年的长江口历史海图资料、实测水深与水文泥沙数据,分析长江口南支最大的浅滩—扁担沙动力地貌演变格局及其变化机制。结果表明：(1) 1860−2016年期间,扁担沙反复历经淤积−冲刷−淤积,浅滩由最初水下阴滩发育出露而形成纺锤状沙体,随后演变为细长扁担状,沙尾切滩成爪状沙体,下扁担沙则伴随爪状缝隙被不断填充而淤长;(2)自1954年洪水到目前,扁担沙−2 m、−5 m等深线包络的面积与体积整体上均呈现增长态势,其中面积年均增长率分别为0.88 km²/a和0.81 km²/a,体积年均增长率分别为1.3×10⁶ m³/a和5×10⁶ m³/a;扁担沙浅滩在不同时期冲淤变化不同,其中1998年出现大幅度冲刷,平均冲刷厚度达到1.4 m;(3)扁担沙体积变化和长江入海泥沙的增减无直接联系,但与入海径流量的变化密切相关;(4)白茆沙“南强北弱”的河势、南北港分流工程以及东风西沙水库的建立导致扁担沙向北推移。     

近30年长江口海域生态系统健康状况及变化趋势研究

为评估长江口海域生态系统健康状况,本文以鱼类浮游生物为指示生物,选择1986年、1999年、2007年和2016年4个年份的数据,选取鱼类浮游生物总种类数、底栖鱼种类数、水层鱼种类数、低耐污鱼种类数、高耐污鱼种类数百分比、杂食性鱼种类数百分比、虫食性鱼种类数百分比、肉食性鱼种类数百分比、鱼类取样个体数、天然杂交种种类数百分比等10个评价指标,采用1、3、5赋值法计算4个不同年份的河口生物完整性指数(Estuarine Biotic Integrity Index,EBI),并以此评价近30年长江口海域生态系统健康状况变化趋势。结果显示,1986年、1999年、2007年和2016年4个不同年份的EBI值分别是52、40、36、34,对应的EBI等级分别为“好”、“一般”、“一般−差”、“差”。通过分析EBI年际变化的结果,发现近30年来长江口海域生态系统健康状况呈现先下降,而后稳定在较低水平的趋势,说明长江口海域生态系统亟需及时进行保护和修复工作。