Porewater-derived dissolved inorganic carbon and nutrient fluxes in a saltmarsh of the Changjiang River Estuary

Saltmarshes are one of the most productive ecosystems, which contribute significantly to coastal nutrient and carbon budgets. However, limited information is available on soil nutrient and carbon losses via porewater exchange in saltmarshes. Here, porewater exchange and associated fluxes of nutrients and dissolved inorganic carbon(DIC) in the largest saltmarsh wetland(Chongming Dongtan) in the Changjiang River Estuary were quantified. Porewater exchange rate was estimated to be(37±35) cm/d during December 2017 using a radon(~(222)Rn) mass balance model. The porewater exchange delivered 67 mmol/(m~2·d), 38 mmol/(m~2·d) and 2 690 mmol/(m~2·d) of dissolved inorganic nitrogen(DIN), dissolved silicon(DSi) and DIC into the coastal waters,respectively. The dominant species of porewater DIN was NH_4~+ (99% of DIN). However, different with those in other ecosystems, the dissolved inorganic phosphorus(DIP) concentration in saltmarsh porewater was significantly lower than that in surface water, indicating that saltmarshes seem to be a DIP sink in Chongming Dongtan. The porewater-derived DIN, DSi and DIC accounted for 12%, 5% and 18% of the riverine inputs, which are important components of coastal nutrient and carbon budgets. Furthermore, porewater-drived nutrients had obviously high N/P ratios(160–3 995), indicating that the porewater exchange process may change the nutrient characteristics of the Changjiang River Estuary and further alter the coastal ecological environment.     

Benthic metabolism and the fate of dissolved inorganic nitrogen in intertidal sediments

We determined patterns of benthic metabolism and examined the relative importance of denitrification (DNF) and dissimilatory nitrate reduction to ammonium (DNRA) as sinks for nitrate (NO₃⁻) in intertidal sediments in the presence and absence of benthic microalgal (BMA) activity. By influencing the activity of BMA, light regulated the metabolic status of the sediments, and, in turn, exerted strong control on sediment nitrogen dynamics and the fate of inorganic nitrogen. A pulsed addition of ¹⁵N-labeled NO₃⁻ tracked the effect and fate of dissolved inorganic nitrogen (DIN) in the system. Under illuminated conditions, BMA communities influenced benthic fluxes directly, via DIN uptake, and indirectly, by altering the oxygen penetration depth. Under dark hypoxic and anoxic conditions, the fate of water column NO₃⁻ was determined largely by three competing dissimilatory reductive processes; DNF, DNRA, and, on one occasion, anaerobic ammonium oxidation (anammox). Mass balance of the added ¹⁵N tracer illustrated that DNF accounted for a maximum of 48.2% of the ¹⁵NO₃⁻ reduced while DNRA (a minimum of 11.4%) and anammox (a minimum of 2.2%) accounted for much less. A slurry experiment was employed to further examine the partitioning between DNF and DNRA. High sulfide concentrations negatively impacted rates of both processes, while high DOC:NO₃⁻ ratios favored DNRA over DNF.     

渤海海峡冬季无机碳的立体分布特征及其源汇变化

根据2010年2月至2010年3月对渤海海峡3个断面39个站位表层、10 m层和30 m层水体中盐度、水温、叶绿素a以及无机碳等参数的测定数据,分析了该季节溶解无机碳的分布特征以及源汇变化状况,探讨了影响其分布的主要因素。结果显示,调查期间渤海海峡水体中各水层溶解无机碳(DIC)及其组分浓度分布较一致,其中DIC及HCO₃-的浓度等值线分布均呈现出从西南向东北梯度降低的趋势,且受温度影响明显;二氧化碳分压[p(CO₂)]则表现出与叶绿素a含量成明显负相关的分布特征;位于渤海海峡东部的H断面垂直方向上,由于受黄海、渤海水团在海峡中部交汇混合形成的水体紊流影响,DIC及其组分在断面中部等值线分布较两边曲折。冬季渤海海峡表现出明显的源、汇分区分布特征,整个调查区海-气二氧化碳通量为3.52 mmol/(m2·d),表现为大气CO₂的弱源。冬季流经渤海海峡的DIC通量约为(130±2)×103 mol/s。     

Dissolved inorganic carbon dynamics in the waters surrounding forested mangroves of the Ca Mau Province (Vietnam)

Dissolved inorganic carbon (DIC) and ancillary data were obtained during the dry and rainy seasons in the waters surrounding two 10-year-old forested mangrove sites (Tam Giang and Kiên Vàng) located in the Ca Mau Province (South-West Vietnam). During both seasons, the spatial variations of partial pressure of CO₂ (pCO₂) were marked, with values ranging from 704 ppm to 11481 ppm during the dry season, and from 1209 ppm to 8136 ppm during the rainy season. During both seasons, DIC, pCO₂, total alkalinity (TAlk) and oxygen saturation levels (%O₂) were correlated with salinity in the mangrove creeks suggesting that a combination of lower water volume and longer residence time (leading to an increase in salinity due to evaporation) enhanced the enrichment in DIC, pCO₂ and TAlk, and an impoverishment in O₂. The low O₂ and high DIC and pCO₂ values suggest that heterotrophic processes in the water column and sediments controlled these variables. The latter processes were meaningful since the high DIC and TAlk values in the creek waters were related to some extent to the influx of pore waters, consistent with previous observations. This was confirmed by the stochiometric relationship between TAlk and DIC that shows that anaerobic processes control these variables, although this approach did not allow identifying unambiguously the dominant diagenetic carbon degradation pathway. During the rainy season, dilution led to significant decreases of salinity, TAlk and DIC in both mangrove creeks and adjacent main channels. In the Kiên Vàng mangrove creeks a distinct increase of pCO₂ and decrease of %O₂ were observed. The increase of TSM suggested enhanced inputs of organic matter probably from land surrounding the mangrove creeks, that could have led to higher benthic and water column heterotrophy. However, the flushing of water enriched in dissolved CO₂ originating from soil respiration and impoverished in O₂ could also have explained to some extent the patterns observed during the rainy season. Seasonal variations of pCO₂ were more pronounced in the Kiên Vàng mangrove creeks than in the Tam Giang mangrove creeks. The air–water CO₂ fluxes were 5 times higher during the rainy season than during the dry season in the Kiên Vàng mangrove creeks. In the Tam Giang mangrove creeks, the air–water CO₂ fluxes were similar during both seasons. The air–water CO₂ fluxes ranged from 27.1 mmol C m⁻² d⁻¹ to 141.5 mmol C m⁻² d⁻¹ during the dry season, and from 81.3 mmol m⁻² d⁻¹ to 154.7 mmol m⁻² d⁻¹ during the rainy season. These values are within the range of values previously reported in other mangrove creeks and confirm that the emission of CO₂ from waters surrounding mangrove forests are meaningful for the carbon budgets of mangrove forests.     

渤海海峡冬季表层海水中溶解无机碳分布特征分析

根据2010 年2 月—2010 年3 月的调查数据, 探讨了冬季渤海海峡及其附近表层海水中溶解无机碳体系的分布特征。结果表明: 表层水体中TA、DIC 和HCO₃^- 的浓度分布总体上呈现出海峡西南部高东北部低的分布趋势。西南部出现的高值区, 与该区域靠近莱州湾, 受莱州湾水体污染影响有关。调查海域TA 与表层水的温度相关性明显, pH 与叶绿素的相关性较高。水温和Chl-a 浓度是影响水体中无机碳体系分布变化的重要因素。其中, 水温对HCO₃^- 的影响要明显强于DIC。海峡南北两侧水体交换的差异, 是导致海峡南部东西两端无机碳体系各参数监测数值的差异明显大于海峡北部的主要原因。     

Terrestrial dissolved organic carbon consumption by heterotrophic bacterioplankton in the Huanghe River estuary during water and sediment regulation

Nearly 20%–50% of the annual terrestrial dissolved organic carbon(DOC)from the Huanghe(Yellow)River was transported to the estuary during the 5-14d of water and sediment regulation.The concentration of DOC increased sharply during the period of water and sediment regulation,which may promote the terrestrial DOC consumption by heterotrophic bacterioplankton.Water and sediment regulation provides an ideal condition for the study of terrestrial DOC consumption by heterotrophic bacterioplankton when terrestrial DOC increases sharply in rainy season,which may help to seek the fates of terrestrial DOC in the estuaries and coasts.In this study,the concentration and stable isotope of DOC,the biomass,growth,and respiration of heterotrophic bacterioplankton were determined.By the study,we found both average percent contribution of terrestrial DOC to the DOC pool and Contribution of terrestrial DOC to the carbon composition of heterotrophic bacterioplankton decreased as distance from the river mouth increased off shore,which was deceased from(39.2±4.0)%,(37.5±4.3)%to(30.3±3.9)%,(28.2±3.9)%respectively.255-484μg C/(L·d)terrestrial DOC was consumed by heterotrophic bacterioplankton.And 29%-45%terrestrial DOC consumed by heterotrophic bacterioplankton releasing as CO2 by respiration.Comparing with tropical estuary,terrestrial DOC consumed by heterotrophic bacterioplankton was lower in temperate estuary(this study).Temperature may limit the consumption of terrestrial DOC by heterotrophic bacterioplankton.     

模拟添加氮对海水溶解无机碳体系的影响

碳和氮作为主要的生源要素对维持海洋生态系的正常运转起着至关重要的作用,碳与氮的变化是相互耦合的且呈双向作用,为探讨海水无机碳与氮的相互作用规律,研究了室内模拟添加硝酸盐对海水无机碳体系pH、溶解无机碳(DIC)、HCO3-、二氧化碳分压(Pco2)的影响。结果表明,在室内培养的条件下,单纯添加硝酸盐(增加至原海水硝酸盐浓度的5-20倍)可引起培养体系浮游生物量的变化,但不能引起海水pH及DIC、HCO-3含量的明显变化,对DIC而言,其变化率仅仅在1%以内,但可导致海水Pco2的相对明显升高,其最终结果导致海水碳汇强度的减弱,碳源强度的增加。     

黄海春季表面海水溶解无机碳的分层研究

根据中国SOLAS计划2006年4月航次出海调查所得数据,系统地研究了春季黄海表面海水溶解无机碳（DIC）的分布规律,同时,与2005年3月、5月两个航次的DIC调查结果进行了对比。结果表明：（1）DIC浓度由近岸向外海逐渐降低;（2）DIC浓度在海水微表层中明显大于次表层和表层,呈现富集现象;（3）由于海水微表层的多层模型特征和海水微表层中Gibbs吸附异常的共同作用,使DIC含量在海水微表层、次表层和表层中变化趋势呈现非线性;（4）在连续站的周日变化研究中发现,DIC浓度在02：00～03：00时间范围内出现最大值,在13：00～15：00时间范围内出现最小值,呈“单峰”分布规律;（5）对比2005年研究结果,发现黄海春季表面海水中的DIC浓度在3,4,5月份依次降低;（6）DIC与温度和盐度均呈较明显的负相关性。     

桑沟湾沉积碳库年汇入速率的长期变化及其区域性差异

对取自桑沟湾北西南三根柱样近200 a碳来源及埋藏通量的解析,分析了湾内不同站位各形态碳的差异性,进而对全湾碳埋藏进行了估算。湾内环流、贝藻养殖等造成湾内不同区域碳埋藏的差异;桑沟湾总碳（TC）平均量1.79%,有机碳（TOC）平均量0.54%,无机碳（TIC）平均量1.25%,TOC含量相对较小,为海陆混合来源,以陆源有机碳（C_t）为主,大规模人工养殖后,海源有机碳（C_a）有明显增加的趋势。桑沟湾碳埋藏通量平均为228.9 g/（m2·a）,以无机碳为主要埋藏形式（约占70%）,高的沉积速率及生物残骸沉降使桑沟湾养殖区碳的来源及埋藏区别于其他陆架海域。     

The effect of submarine groundwater discharge on nutrient and salinity regimes in a coastal lagoon off Perth, Western Australia

Submarine groundwater discharge (SGD) into a coastal lagoon off Perth, Western Australia, contains nitrate and silicate in concentrations two orders of magnitude higher than those of the receiving waters. This discharge delivers enough nitrate to replace that dissolved in the lagoon water mass about every eight days and enough silicate to replace the lagoon silicate in about 48 days. The delivery rate of nitrate nitrogen by SGD is equal to about 48% of that required for observed growth rates of lagoon macrophytes. Surface salinity is lower close to the shore as a result of SGD. During calm conditions a salinity front was observed in the lagoon, with a nearshore pool of nutrient-enriched water floating above the more saline ocean water.     

Spatio-temporal distribution of dissolved inorganic carbon and net community production in the Chukchi and Beaufort Seas

As part of the 2002 Western Arctic Shelf–Basin Interactions (SBI) project, spatio-temporal variability of dissolved inorganic carbon (DIC) was employed to determine rates of net community production (NCP) for the Chukchi and western Beaufort Sea shelf and slope, and Canada Basin of the Arctic Ocean. Seasonal and spatial distributions of DIC were characterized for all water masses (e.g., mixed layer, halocline waters, Atlantic layer, and deep Arctic Ocean) of the Chukchi Sea region during field investigations in spring (5 May–15 June 2002) and summer (15 July–25 August 2002). Between these periods, high rates of phytoplankton production resulted in large drawdown of inorganic nutrients and DIC in the Polar Mixed Layer (PML) and in the shallow depths of the Upper Halocline Layer (UHL). The highest rates of NCP (1000–2850 mg C m⁻² d⁻¹) occurred on the shelf in the Barrow Canyon region of the Chukchi Sea and east of Barrow in the western Beaufort Sea. A total NCP rate of 8.9–17.8×10¹² g for the growing season was estimated for the eastern Chukchi Sea shelf and slope region. Very low inorganic nutrient concentrations and low rates of NCP (<15–25 mg C m⁻² d⁻¹) estimated for the mixed layer of the adjacent Arctic Ocean basin indicate that this area is perennially oligotrophic.     

Effects of upwelling,tides and biological processes on the inorganic carbon system of a coastal lagoon in Baja California

The role of coastal lagoons and estuaries as sources or sinks of inorganic carbon in upwelling areas has not been fully understood. During the months of May–July, 2005, we studied the dissolved inorganic carbon system in a coastal lagoon of northwestern Mexico during the strongest period of upwelling events. Along the bay, different scenarios were observed for the distributions of pH, dissolved inorganic carbon (DIC) and apparent oxygen utilization (AOU) as a result of different combinations of upwelling intensity and tidal amplitude. DIC concentrations in the outer part of the bay were controlled by mixing processes. At the inner part of the bay DIC was as low as 1800 μmol kg⁻¹, most likely due to high water residence times and seagrass CO₂ uptake. It is estimated that 85% of San Quintín Bay, at the oceanic end, acted as a source of CO₂ to the atmosphere due to the inflow of CO₂-rich upwelled waters from the neighboring ocean with high positive fluxes higher than 30 mmol C m⁻² d⁻¹. In contrast, there was a net uptake of CO₂ and HCO₃⁻ by the seagrass bed Zostera marina in the inner part of the bay, so the pCO₂ in this zone was below the equilibrium value and slightly negative CO₂ fluxes of −6 mmol C m⁻² d⁻¹. Our positive NEP and ΔDIC values indicate that Bahía San Quintín was a net autotrophic system during the upwelling season during 2005.     

The influence of macronitrogen (NO3- and NH4+) addition with Ulva pertusa on dissolved inorganic carbon system

The influence of macronitrogen (NO - 3 and NH + 4 ) addition with Ulva pertusa on dissolved inorganic carbon system in seawater was studied. The results indicate that p(CO 2 ) and HCO 3 concentration decrease significantly, while pH and CO 2- 3 concentration increase significantly. When the concentration of NO 3 was less than 71 μmol/dm 3 or NH + 4 was less than 49.7 μmol/dm 3 , dissolved inorganic carbon (DIC) absorption rates by Ulva pertusa generally increased with the increasing of nitrogen concentration. The DIC decreased 151 μmol/dm 3 with the addition of 71 μmol/dm 3 NO 3 and decreased 232 μmol/dm 3 with the addition of 49.7 μmol/dm 3 NH + 4 after the experiment compared with DIC measured without nitrogen addition. A significant negative-correlation was found between c(DIC) and growth rate (μ) of Ulva pertusa (r = -0.91, P <0.000 1, n=11). NH + 4 had more influence on the species of inorganic carbon system than NO 3 .     

Temporal variations of surface oceanic and atmospheric CO2 fugacity and total dissolved inorganic carbon in the northwestern North Pacific

In order to examine temporal variations of the surface oceanic and atmospheric fCO₂ and the DIC concentration, we analyzed air and seawater samples collected during the period May 1992–June 1996 in the northwestern North Pacific, about 30 km off the coast of the main island of Japan. The atmospheric CO₂ concentration has increased secularly at a rate of 1.9 ppmv yr⁻¹, and it showed a clear seasonal cycle with a maximum in spring and a minimum late in summer, produced mainly by seasonally-dependent terrestrial biospheric activities. DIC also showed a prominent seasonal cycle in the surface ocean; the minimum and maximum values of the cycle appeared in early fall and in early spring, respectively, due primarily to the seasonally-dependent activities of marine biota and partly to the vertical mixing of seawater and the coastal upwelling. The oceanic fCO₂ values were almost always lower than those of the atmospheric fCO₂, suggesting that this area of the ocean acts as a sink for atmospheric CO₂. Values varied seasonally, mainly reflecting seasonal changes of SST and DIC, with a secular increase at a rate of 3.7 μatm yr⁻¹. The average values of the annual net CO₂ flux between the ocean and the atmosphere calculated by using the different bulk equations ranged between −0.8 and −1.7 mol m⁻²yr⁻¹, and its magnitude was enhanced and reduced late in spring and mid-summer, respectively, due mainly to the seasonally varying oceanic fCO₂.     

Observed fluxes of water,salt and suspended sediment in a partly mixed estuary

Observations of the residual fluxes of water, salt and suspended sediment are presented for seven stations along the Tamar Estuary. The data include measurements over single spring and neap tidal cycles, and are generally applicable to medium or high run-off conditions.Surface to bed differences in salinity are typically of the order of several parts per thousand. Gravitational circulation is an important component of residual flow in the deep, lower reaches of the estuary. Here, Stokes drift is insignificant. In the shallow upper reaches, the major residual currents are generated by Stokes drift and freshwater inputs. Data are compared with predictions from Hansen and Rattray's (1966) model of estuarine circulation.Salt fluxes due to tidal pumping and vertical shear are directed up-estuary at spring tides, tidal pumping being dominant. Tidal pumping of salt is also directed up-estuary at neap tides, although it is insignificant in the lower reaches, where vertical shear dominates.Tidal pumping of suspended sediment is directed up-estuary near the head at spring tides, and probably contributes to the formation of the turbidity maximum. The existence of the turbidity maximum is predicted using a simplified model of the transport of water and sediment. The model shows that an additional mechanism for the existence of the turbidity maximum is an up-estuary maximum in the tidal current speeds (and thus resuspension). In the lower reaches, transport of suspended sediment is directed down-estuary at both spring and neap tides, and sediment is essentially flushed to sea with the fresh water.     

The relationship between chromophoric dissolved organic matter and dissolved organic carbon in the European Atlantic coastal area and in the West Mediterranean Sea (Gulf of Lions)

The absorption coefficient of chromophoric dissolved organic matter (aCDOM) has been found to be correlated with fluorescence emission (excitation at 355 nm). In the coastal European Atlantic area and in the Western Mediterranean Sea (Gulf of Lions), a significant statistical dependence has been found between aCDOM and fluorescence with dissolved organic carbon (DOC) concentration. The relationship shows that, in the river plume areas (Rhine in the North Sea and Rhône in the Gulf of Lions), a consistent fraction of DOC (from 40% to 60% of the average of the DOC measured) is non-absorbing in visible light range, where the dissolved organic matter (DOM) is typically absorbent. In comparison, in the open sea, apparently not affected by the continental inputs, the entire DOC belongs to the chromophoric DOM whose specific absorption is lower (5 to 10 times) than that found in the river plume areas.     

Distribution of dissolved organic carbon in and near the Prydz Bay, Antarctica

INTRODUCTIONDissolvedorganiccarbon (DOC)makesupthesecondlargestofthebioactivepoolsofcar bonintheocean ,secondtothelargestpoolofdissolvedinorganiccarbon .Theglobaldissolvedorganiccarbonpoolisestimatedtobe 6 85Gt,avaluecomparabletothemassofCO2 intheat mosphere (Hedges,1 992 ) .Thesizeofthereservoir,aswellasitsdynamics ,indicatesthatDOCplaysacentralroleintheoceancarboncycle .AsitrelatestogreenhousegasessuchasCO2 andassociatesclimatecycle ,oceanicDOCbiogeochemicalcycleshavebeenoneoftheh…     

南极普里兹湾及其邻近海域溶解有机碳的分布

中国南极科学考察第16航次期间(1999年11月～2000年4月),在南极普里兹湾及邻近海域的不同站位与水深采集海水样品用于溶解有机碳测定,通过高温催化氧化法完成样品的分析.结果表明,在调查期间,南极普里兹湾及其邻近海域各测站上层水体(0～100m)溶解有机碳浓度的变化范围为14.3～181.1μmol/dm3,平均为52.5μmol/dm3,该变化幅度比Ross海、太平洋等海域的相应值略大.溶解有机碳垂直分布的特征是0大于25大于50大于100m,即随深度的增加溶解有机碳浓度逐渐减小,与生物活动在垂直方向上的强弱变化相关.根据200m以深水柱溶解有机碳的垂直分布,可确定研究海域难降解溶解有机碳的浓度为40.4μmol/dm3,与其他研究所报道的数值(～42μmol/dm3)相近.上层水体(0～100m)过剩溶解有机碳的空间分布显示,64°S以北海域溶解有机碳过剩较多,而64°S以南海域则过剩溶解有机碳较少.溶解有机碳浓度与分布特征显示,普里兹湾及其邻近海域溶解有机碳浓度与南大洋其他海域相当,具有低溶解有机碳的一般特征.溶解有机碳浓度的空间分布呈现由西南向东北方向逐渐增加的趋势,这可能与南极陆架夏季上层水的北向扩展有关.生物活动及水体运动是研究海域溶解有机碳分布的主要影响因素.     

长江口及邻近海域夏季溶解无机碳体系及其响应机制初探

根据2009年8月“908”项目长江口补充调查总碱度(TAlk)、溶解无机碳(DIC)、pH值、溶解氧(DO)和叶绿素a(Chla)等数据的分析结果显示,长江口及邻近东海海域夏季溶解无机碳(DIC)含量分布范围在1 647.1～2 236.9 μmol/dm3之间,平均值为2 031.2 μmol/dm3;空间分布为由...