Methane emission from tidal freshwater marshes

In two tidal freshwater marshes, methane emission,production and accumulation in the pore-water have beenstudied. The two sites differ in their dominantvegetation, i.e., reed and bulrush, and in theirheights above sea level. The reed site was elevated inrelation to the bulrush site and had higher rates ofmethane emission and production. It is argued thatthis difference in methane emission between sites wasprimarily due to a different effect of reed andbulrush plants on methane dynamics rather than methaneoxidation related to tidal elevation. Methane emissionshowed strong seasonality related primarily to plantphysiology and only secondarily to temperature. Twocontrol sites at which vegetation was removedsystematically had lower emission rates indicating anoverall stimulating effect of plants on methaneemission from tidal marshes. Flooding reduced methaneemission, probably by blocking the primary sites ofmethane release in the lower part of the plantstems.     

模拟SO42-沉降对闽江口淡水感潮野慈姑湿地甲烷排放通量的影响

2015年12月—2016年10月,每月小潮日原位定期向闽江口塔礁洲淡水感潮野慈姑(Sagittaria trifolia L.)湿地施加剂量为60、120 kg S hm~(-2)a~(-1)的K_2SO_4溶液(分别记做S-60和S-120),探讨模拟硫酸根(SO_4~(2-))沉降对河口淡水感潮湿地甲烷(CH4)排放通量及间隙水SO_4~(2-)浓度的影响。对照、S-60和S-120处理组CH_4排放通量年均值分别为(7.88±1.00)mg h~(-1)m~(-2)、(6.55±0.97)mg h~(-1)m~(-2)和(6.66±1.49)mg h~(-1)m~(-2)。在年尺度上,两个高强度模拟SO_4~(2-)沉降处理组均未显著降低闽江口淡水感潮野慈姑湿地CH_4排放通量(P0.05),即高强度SO_4~(2-)沉降不会对河口淡水感潮湿地CH_4排放通量产生类似于其对泥炭湿地和水稻田的显著抑制效应。在年尺度以及秋、冬季,两个施加K_2SO_4溶液处理显著增加了野慈姑湿地10 cm深度土壤间隙水SO_4~(2-)浓度。对于各个处理组,温度较高的夏、秋季CH_4排放通量均显著高于温度相对较低的冬、春季(P0.05)。不同处理组CH_4排放通量均与土壤温度呈显著正相关关系,温度仍然是影响亚热带河口淡水感潮湿地CH_4排放通量的重要环境因子。     

Particulate inputs to Dublin Bay and to the South Lagoon,Bull Island

There are substantial riverine and sewage particulate inputs into Dublin Bay. The main river, the R. Liffey, accounts for almost 85% of the riverine input, which amounts to 37.1 t d^–1 of SPM. The sewage input, which is discharged into the estuary, is slightly less at 35.3 t d^–1. The combined inputs deliver 17.4 t d^–1, 2.9 t d^–1and 1.2 t d^–1of particulate C, N and P, respectively, to the Bay as a whole. Although the particulate N load accounts for just 20% of the total N input, the retention of particulates within the system, and the subsequent remobilisation of N from the sediments is heavily implicated in the macroalgal blooms. A particulate mass balance of SPM, and of C, N and P for the South Lagoon showed no consistent pattern of import/export except that the fluxes of the individual elements reflected SPM load and varied with quantity rather than quality. The molar C:N ratio was around 6:1 although on occasion values approaching 3:1 were obtained, indicating very high quality and potentially labile SPM. The controlling factors in the budget appeared to be the water velocities and to a lesser extent, the SPM load, which surprisingly was no greater on a spring tide than on a neap. In this shallow, and primarily intertidal, system, wind- or wave-driven resuspension may exert more influence than predictable factors such as tidal range.     

外源氮输入对黄河口新生湿地植物-土壤系统硫分布特征的影响

选择黄河口北部滨岸高潮滩的碱蓬湿地为研究对象,基于野外原位氮(N)输入模拟试验,研究了不同氮输入梯度下(N0,无氮输入;N1,低氮输入,9.0 gN m~(-2)a~(-1);N2,中氮输入,12.0 gN m~(-2)a~(-1);N3,高氮输入,18.0 gN m~(-2)a~(-1))碱蓬湿地植物-土壤系统全硫(TS)分布特征的差异。结果表明,外源N输入明显改变了湿地土壤TS含量的分布状况。随着N输入量的增加,除表层TS含量变化不明显外,其他土层均呈增加趋势。不同氮输入处理下植物各器官的TS含量整体均表现为叶茎根,叶是硫的主要累积器官。尽管氮输入处理并未改变植被的硫分配格局以及其地上与地下之间的硫养分供给关系,但其为适应不同养分环境可进行自身生长特性及养分分配的调整,且这种调整在N2处理下表现的尤为明显。随氮输入量的增加,不同氮处理下植物-土壤系统的S储量整体呈增加趋势,但土壤S储量的增幅远低于植物亚系统S储量的增幅以及N供给的增幅,说明N、S之间的养分供给存在不同步性。研究发现,未来黄河口N养分负荷增加情况下,碱蓬湿地植物-土壤系统的S生物循环速率不但可能会加速,而且N、S养分之间也可能形成一个正反馈机制,并将有利于维持新生湿地的稳定与健康。     

Nitrogen Behaviour and Nitrous Oxide Emission in the Tidal Seine River Estuary (France) as Influenced by Human Activities in the Upstream Watershed

The Seine River estuary (France) is the receptacle of a drainage basin characterised by high population density, heavy industrial activity and intensive agriculture. Whereas nitrate concentrations are high due to diffuse sources in the upstream drainage basin, ammonium mainly originates from the effluents of the Achères wastewater treatment plant (WWTP) downstream from Paris and its suburbs (6.5 million equivalent-inhabitants). Ammonium is mostly nitrified in the tidal freshwater estuary and nitrification causes a strong summer oxygen deficit. Average longitudinal summer profiles of oxygen and nitrogen concentrations for two periods, between 1993–1997 and 1998–2003 in dry hydrological conditions (excluding the wet years 2000 and 2001) clearly reflect the changes due to the improved treatment of wastewater from Paris and its suburbs. On the basis of daily water flux data and twice monthly nitrogen measurements at the boundaries of the upstream freshwater estuarine section (108 km), we calculated nitrification and denitrification fluxes, whose annual averages were 43 and 71 × 10³ kg N d⁻¹ respectively from 1993 to 2003, with summer values (July–September) representing 73 and 57% of the annual fluxes, respectively. The degree of denitrification in the upper estuary appears to be closely related to the nitrification, itself more loosely related to the amount of reduced nitrogen (Kjeldahl) brought by the treated effluents from the Achères WWTP. We estimated the total N₂O emissions to about 40 kg N d⁻¹ (25–60 kg N d⁻¹) in the same sector.     

江苏盐城上冈全瘭世颗石藻及其环境控制

盐城上冈地区全新世期间处于泥砂质潮滩环境。根据有孔虫组合分析,这套近岸潮滩沉积代表潮下带－湖间带－潮上带的一次大海退过程。本文分析了上冈村砖瓦厂采泥坑东侧SGE柱状剖面全新统的颗石藻化石,结果发现这套沉积物仅仅含Gephyrocapsa oceanica单一属种,而且丰度较低。但这个种在剖面上的丰度分布显示三分性：即自下至上为贫乏或缺失间隔、较常见间隔笔常见间隔,基本上对应于潮下带、潮间带和潮上带。一般情况下,潮坪区由海向陆水动力由强至弱,各相带的水动力条件不同,其沉积特征各异。颗石灌胳架十分细微,在海水中往往以悬乳形式搬运,并在水动力较弱时停积。所以,水动力是G.oceanica分布的直接控制因素。     

底栖生物影响下的潮滩微地貌演化数值模拟

潮滩是海岸带湿地的主要类型之一,其中分布的底栖生物对生态环境具有重要的调节作用。潮滩底栖微藻、泥沙与水动力之间存在相互作用,影响潮滩微地貌形态,明晰底栖生物对潮滩微地貌的演化机制至关重要。以黄河三角洲潮滩湿地为研究区,通过构建潮滩微地貌动力模型,探究底栖生物对微地貌格局演化的作用机制,分析底栖生物对微地貌系统稳定性的影响。结果表明(1)底栖微藻生长与泥沙扩散、水流再分配过程交互作用驱动下,潮滩上可形成底栖微藻覆盖的高丘与积水洼地交替分布的规则性微地貌斑图;(2)微地貌斑图的形成提高了潮滩生态系统初级生产力和泥沙淤积高度;(3)底栖微藻与泥沙、水流的交互作用使得潮滩微地貌系统对侵蚀扰动呈现非线性响应行为,系统存在临界点,且在一定侵蚀率范围内存在双稳态;(4)黄河口泥螺入侵使得微地貌系统抵抗侵蚀扰动能力减小,且系统稳定性随泥螺生物量的增加而降低。     

丰水期长江感潮河口段网采浮游植物的分布与长期变化

于2009年6、8月对长江口门至江阴的河口段浮游植物进行了拖网采集,共检出浮游植物6门99属239种。其中:硅藻123种,甲藻19种,绿藻和蓝藻各42种,裸藻9种,黄藻4种。河口段网采浮游植物丰度以蓝藻占绝对优势,硅藻次之,两者合计在群落中的比例超过了95%。优势种也主要以蓝藻(水华鱼腥藻Anabaena flos-aquae、柔软腔球藻Coelosphaerium kuetzingiarum、微囊藻Microcystis spp.、颤藻Oscillatoria spp.和席藻Phorimidium spp.)构成,硅藻仅有2种(骨条藻Skeletonema spp.和颗粒直链藻Aulacoseira granulata)。口门内盐度均<0.5,群落基本以淡水类群为主,口门附近则以半咸水类群为主,海水类群主要位于口门外(盐度>13)。随着水温和营养盐水平的升高,8月浮游植物平均丰度(347.75×10⁴ 个/m³)明显高于6月(204.19×10⁴ 个/m³)。根据多维尺度和相似性分析,丰水期长江河口段浮游植物群落组成与分布存在显著(P<0.01)的时空差异。对比20世纪80年代以来的历史资料发现,长江口门内网采浮游植物丰度显著升高,且优势种也从硅藻(骨条藻、直链藻和圆筛藻)转变为蓝藻(颤藻、鱼腥藻和微囊藻)。     

闽江河口潮汐湿地二氧化碳和甲烷排放化学计量比

为了阐明河口潮汐湿地碳源温室气体排放的化学计量比特征,对闽江河口潮汐湿地二氧化碳和甲烷排放进行了测定与分析。结果表明:芦苇湿地和短叶茳芏湿地二氧化碳与甲烷排放均呈现正相关;涨潮前、涨落潮过程和落潮后芦苇湿地和短叶茳芏湿地CO2∶CH4月平均值分别为55.4和185.0,96.3和305.5,68.7和648.6,3个过程芦苇湿地和短叶茳芏湿地CO2∶CH4差异均不显著(P>0.05),2种植物湿地CO2∶CH4对潮汐的响应并不一致,但均在涨潮前表现为最低;涨潮前、涨落潮过程和落潮后均表现为芦苇湿地CO2∶CH4低于短叶茳芏湿地(P<0.05);河口潮汐湿地CO2∶CH4为空间变异性>时间变异性,潮汐、植物和温度均对CO2∶CH4的变化具有一定的调节作用。