闽江口芦苇与短叶茳芏湿地土壤无机硫形态分布特征及其影响因素

选择闽江口鳝鱼滩的芦苇湿地、短叶茳芏湿地以及二者交错带湿地为对象,研究了不同类型湿地土壤无机硫赋存形态的分布特征及其主要影响因素。结果表明,芦苇与短叶茳芏在空间扩展过程中形成的交错带湿地土壤的水溶性硫(H_2O-S)、吸附性硫(Adsorbed-S)和盐酸可溶性硫(HCl-Soluble-S)含量在0—40 cm土层上整体要高于芦苇湿地和短叶茳芏湿地,而盐酸挥发性硫(HCl-Volatile-S)含量则与之相反。在垂直方向上,不同类型湿地土壤的H_2O-S、Adsorbed-S和HCl-Soluble-S含量整体均自表层向下呈先降低而后增加的变化,而盐酸挥发性硫(HCl-Volatile-S)含量则与之相反。3种类型湿地土壤中不同形态无机硫平均含量整体均表现为HCl-Soluble-S H_2O-S Adsorbed-S HCl-Volatile-S,且其总无机硫(TIS)平均含量分别占全硫(TS)含量的22.29%—39.99%(芦苇湿地)、32.39%—33.33%(交错带湿地)和30.20%—30.86%(短叶茳芏湿地)。与芦苇湿地和短叶茳芏湿地相比,交错带湿地土壤的H_2O-S、Adsorbed-S、HCl-Soluble-S和TIS平均含量整体均呈增加趋势,增幅分别为36.94%和54.31%、34.84%和13.03%、73.25%和67.59%以及45.72%和45.28%;与之不同,HCl-Volatile-S平均含量则呈降低趋势,降幅分别为2.78%和22.24%。不同类型湿地土壤中H_2O-S、Adsorbed-S和TIS含量的变化主要受有机质含量和细颗粒组成的控制,而HCl-Soluble-S和HCl-Volatile-S含量主要受土壤氧化还原环境和金属元素分布的影响。研究发现,芦苇与短叶茳芏的空间扩展明显增加了交错带湿地土壤的H_2O-S、Adsorbed-S、HCl-Soluble-S和TIS含量,但降低了HCl-Volatile-S含量,说明二者的空间扩展在整体提高交错带湿地土壤有效硫供给能力的同时,亦降低了挥发性硫化物可能对二者生长产生的不利影响,这对于保持二者在交错带湿地中的竞争力具有重要生态意义。     

长江河口潮间带盐沼植被分布区及邻近光滩鱼类组成特征

研究鱼类群落在不同生境中的差异或者变化,是评价与预测生境丧失、环境退化等对湿地生物多样性与生态系统功能影响的重要基础。2006年4—11月,在长江河口崇明东滩盐沼植被分布区(简称草滩)和邻近的光滩区域分别设置采样站位,每月大潮期采用定制插网对鱼类群落进行了取样调查。分析研究了长江河口潮间带盐沼植被分布区和邻近光滩区域的鱼类组成及其月际变化,并对影响鱼类分布的主要因子进行了探讨。调查期间共采集鱼类标本1638尾,分属9目14科22种;其中,淡水鱼类2种,定居性河口鱼类12种,海洋鱼类5种,洄游鱼类3种。植被分布区和光滩区域鱼类组成及优势种特征存在明显差异。调查期间,植被分布区记录鱼类13种,主要优势种为斑尾刺虾虎鱼(Acanthogobius ommaturus)、鲻(Mugil cephalus)和棱鮻(Liza carinatus)(IRI>20),其他种类基本不具有优势度特征(IRI<0.05);光滩区域记录鱼类20种,主要优势种鲻(IRI>20),其他包括斑尾刺虾虎鱼、狼牙鳗虾虎鱼(Taenioides rubicundus)、棱鮻和棘头梅童鱼(Collichthys lucidus)也具有一定的优势特征(20>IRI>10);两个区域共有种为11种,部分种类只出现在光滩或植被分布区,但主要优势种均为定居性河口鱼类。与世界其他河口盐沼湿地鱼类研究结果不同的是,光滩区域记录的鱼类物种数、个体数、生物量和整体物种多样性水平均高于植被分布区;光滩和植被分布区鱼类相应的量比关系存在明显的月际变化,但两种生境鱼类组成间的关联性和差异性均不显著。通过比较两种生境共有的优势种体长发现,长江河口盐沼植被分布区鱼类优势种的平均体长大于光滩区域,而且植被分布区部分优势种体长的上、下限范围也大于光滩区域。长江河口盐沼植被分布区,除了育幼场外,还是许多鱼类成鱼的重要栖息地。影响河口潮间带盐沼湿地鱼类组成与分布的主要因素包括鱼类自身的生物学与生活史特征、饵料生物的组成与分布、植被出现与表形特征等生物因素和水温、盐度、淡水径流、潮汐特性等非生物因素,其对长江河口潮间带盐沼湿地中鱼类群落的组成与分布的综合作用机理有待进一步研究。     

长江口锋面附近咸淡水混合对浮游植物生长影响的现场培养

通过2009年6月调查航次,获得了营养盐等参数断面分布,表明咸淡水混合是控制营养盐分布的主要因素。为了解不同盐度梯度下浮游植物生长与营养盐吸收的关系,采集两个站位水样分别代表长江冲淡水(C1站)和外海水(I10站),按C1站水样比例,分100%、75%、50%、25%、0%不同比例混合进行现场模拟咸淡水混合培养,有以下认识:(1)平行结果表明培养过程中活体荧光极大值在100%混合组,且淡水比例越低,指数生长期0—48 h内生长速率越低,100%、75%、50%、25%组分别为1.18/d、1.12/d、1.14/d、0.77/d;(2)低于26盐度的水体中PO34-在48 h内可被迅速消耗而产生限制作用,是控制浮游植物生长的潜在限制因子;(3)除0%组外,各混合组DIN/P(DIN:溶解无机氮,Dissolved Inorganic Nitrogen,DIN=NO3-+NO-2+NH4+)比值在浮游植物指数生长期有升高趋势,100%组DIN/P比值增加了一倍。各组培养48 h后DIN/Si比值逐渐降低至原来的0.7左右,初始DIN/Si小于一定时间内硅藻吸收的(ΔDIN/ΔSi)比,是造成各组DIN/Si比值减小的原因。以上结果表明咸淡水混合过程中形成的营养盐梯度可造成浮游植物生长程度和速率差异,且可因局部浮游植物旺发而改变海水营养结构。     

珠江口水域夏季小型底栖生物群落结构

于2010年8月在珠江口水域进行小型底栖生物取样分析,结果表明,该调查水域夏季小型底栖生物的平均丰度为(183±174)个/10 cm2,平均生物量为(345±334)μg干重/10 cm2,平均生产量为(3104±3008)μg干重/10 cm2。共鉴定出小型底栖生物16个类群,按丰度,自由生活海洋线虫和双壳类幼体为优势类群,其丰度分别占调查水域小型底栖生物总丰度的62.61%和22.62%。按生物量,优势类群由双壳类幼体(50.57%)、线虫(13.33%)和多毛类(12.47%)等组成。81.15%的小型底栖生物分布在0—5 cm的沉积物中。与环境因子相关分析表明:小型底栖生物丰度、线虫丰度与温度呈显著负相关,与盐度呈显著正相关。调查水域线虫与桡足类数量的比值(N/C)呈现出由河口上游向下游递增,且西岸明显高于东岸的趋势。     

2010年夏季珠江口海域颗粒有机碳的分布特征及其来源

于2010年8月对珠江口海域20个站位的颗粒有机碳(POC)进行采样,分析了POC的空间分布特征,讨论了POC与环境因子之间的关系,并利用碳稳定同位素(δ13C)分析了POC的来源及其贡献率。结果显示,研究区域POC的浓度范围98.5—1929.8μg/L,平均浓度541.9μg/L,空间分布总体呈现自北部海域向中部海域逐渐降低,中部海域至南部海域又逐渐升高,底层大于表层的特点。总悬浮颗粒物、叶绿素a、水动力是影响POC空间分布的重要原因。研究区域总悬浮颗粒物δ13C值的变化范围-27.05‰—-21.03‰,平均为-24.57‰,反映出珠江口海域颗粒有机碳为陆源和水生源混合来源,其分布呈现沿盐度梯度自口门内向口门外逐渐递增,底层高于表层的特点。陆源输入和海洋生物生产是影响δ13C值分布的主要原因。运用二元混合模型计算得知,珠江口北部和中部海域POC以陆源有机碳为主,贡献率平均为64%;南部海域POC以水生源有机碳为主,贡献率平均为68%。与20多年前相比,POC的分布特征与来源已经发生了改变,珠江口海域含沙量减少与营养盐含量增加可能是导致POC组成发生变化的主要原因。     

Life history of the Indo‐Pacific humpback dolphin in the Pearl River Estuary,southern China

We studied life history characteristics of the Hong Kong/Pearl River Estuary population of Indo‐Pacific humpback dolphins (Sousa chinensis), based on data from 120 specimens stranded between 1995 and 2009, 40 individuals biopsied at sea, and a long‐term (14+ yr) photo‐identification study. Ages were determined for 112 specimens by thin‐sectioning teeth and counting growth layer groups. Estimated length at birth was 101 cm. Longevity was at least 38 yr, and there was little difference in growth patterns of males and females. Growth was described by a Bayesian two‐phase Gompertz model; asymptotic length was reached at 249 cm. The tooth pulp cavity filled at an average of 18.5 yr of age. Physical maturity was reached at between 14 and 17 yr of age, apparently a few years after attainment of sexual maturity. Maximum lengths and weights of about 268 cm and 240 kg were attained. Females appear to lose all their spots by 30 yr, although males may retain some spotting throughout life. Calving occurred throughout the year, with a broad peak from March to June. Of 60 females monitored at sea for >14 yr of the study, none were documented to have more than three calves, suggestive of low reproductive output or low calf survival.     

The effects of human activities and extreme meteorological events on sediment nitrogen dynamics in an urban estuary,Escambia Bay,Florida, USA

This study examined how sediment-sorbed PCBs and several large storms affected sediment nutrient dynamics based on potential nitrification rates and benthic flux measurements. PCBs were hypothesized to negatively affect potential nitrification rates due to the sensitivity of nitrifying bacteria. Sediment disturbance caused by the succession of storms, which can enhance nutrient inputs and phytoplankton production, was hypothesized to enhance both potential nitrification rates and benthic flux measurements as a result of higher nutrient and organic matter concentrations. Potential nitrification rates, benthic fluxes (NO₃ ⁻ + NO₂ ⁻, NH₄ ⁺, and DIP), sediment PCB content, water content, organic content, salinity, bottom water dissolved oxygen, and sediment chlorophyll were measured at 13 different sites in Escambia Bay during the summer of 2005. Potential nitrification rates were highest at deep, organic-rich sites. Total PCB content did not have a direct effect on potential nitrification rates. An analysis of recent changes in benthic processes in relation to extreme meteorological events was performed by comparing the 2005 results with data from 2000, 2003, and 2004. Storm effects on sediment biogeochemistry were mixed with sediment nitrogen dynamics enhanced at some sites but not others. In addition, SOC and NH₄ ⁺ fluxes increased in deeper channel sites after Hurricanes Ivan and Dennis, which could be attributed to the deposition of phytoplankton blooms. Sediment nutrient dynamics in Escambia Bay appear to be resilient to these extreme meteorological events since there were no significant effects on sediment processes in the Bay as a whole. Handling editor: P. Viaroli     

Movement patterns of catfishes (Ariidae) in a tropical semi‐arid estuary

From December 2005 to November 2006, 216 samples were taken from the main channel of the Goiana Estuary, representing a total sampled area of 23 ha. Ariidae species were the most abundant in density (1600 individuals ha^?1, 53%) and biomass (18 813 g ha^?1, 63%). Cathorops spixii was the most abundant in density (1340 individuals ha^?1) and biomass (14 203 g ha^?1). The variables: number of species, total density and biomass, showed significant interactions between the factors of areas and seasons (P < 0·01). The highest total density (7394 individuals ha^?1) and biomass (70 292 g ha^?1) occurred in the middle and upper estuaries, respectively, during the early‐rainy season. The density of C. spixii differed significantly between areas and seasons (P < 0·01), while Cathorops agassizii differed significantly only between seasons (P < 0·01). The biomass differed significantly for the species C. spixii, C. agassizii and Sciades herzbergii between seasons, and C. spixii and C. agassizii between areas. Also, the density and biomass of C. spixii and C. agassizii showed interaction between areas and seasons. Only the biomass of S. herzbergii showed interaction between areas and seasons (P < 0·01). This indicates that seasonal variations influenced the distribution of Ariidae species in the different areas of the Goiana Estuary. Moreover, canonical correspondence analysis highlighted a strongly significant correlation (P < 0·01) between the seasonal variations of the environmental gradients (salinity and water temperature) and distribution of catfishes. The management and conservation of estuaries should take into account the life cycle of these species in different estuarine areas and hydrological seasons.     

Application of palynology to describe vegetation succession in estuarine wetlands on Great Barrier Island,northern New Zealand

Question: This paper compares published palynological studies from coastal swamps containing the same suite of species. We ask the following questions: (1) does succession follow the same pathways in different swamp systems, or (2) at different times? If not, (3) how variable are the patterns and (4) what are the likely driving factors? Location: Great Barrier Island, Northern New Zealand. Methods: Eighteen pollen profile diagrams were studied from four estuarine wetlands, ranging from mangroves to swamp forest. Recognition of a transition between vegetation stages was by subjective consideration of the relative abundances of pollen of key indicator species at different depths in the sedimentary sequence. Results: A linear sequence of vegetation communities beginning with mangroves and followed by estuarine marsh communities composed of Juncus kraussii, Leptocarpus similis and Baumea juncea was recognised in almost all pollen diagrams. Further transitions, from Baumea to a terrestrial system of Leptospermum shrubland or Cordyline/Dacry‐carpus swamp forest, followed two main pathways associated with autogenic accumulation of peat and terrigenous sediment input respectively. At Kaitoke and Awana the marine/freshwater transition occurred before the arrival of humans on Great Barrier Island. At Whangapoua, increased sedimentation followed anthropogenic burning of adjacent forest, and this transition was faster and is still in progress. Conclusion: Palynology and current vegetation zonation patterns concur to demonstrate that the marine sedimentation phase of estuarine succession is predictable and linear. Baumea marks the transition to the freshwater phase, in which varied successional patterns are determined by interactions between hydrology, sediment input, and peat accumulation. Natural and human disturbances drive sedimentation rates, and interact with autogenic factors, to dictate vegetation transitions in these later stages. The intensive impact (mainly burning) during Polynesian times had a much greater effect on estuaries and swamps than the pre‐Polynesian natural processes, greatly accelerating plant succession.     

The prediction of nutrients into estuaries and their subsequent behaviour: application to the Tamar and comparison with the Tweed,U.K.

Some of the techniques used to model nitrogen (N) and phosphorus (P) discharges from a terrestrial catchment to an estuary are discussed and applied to the River Tamar and Tamar Estuary system in Southwest England, U.K. Data are presented for dissolved inorganic nutrient concentrations in the Tamar Estuary and compared with those from the contrasting, low turbidity and rapidly flushed Tweed Estuary in Northeast England. In the Tamar catchment, simulations showed that effluent nitrate loads for typical freshwater flows contributed less than 1% of the total N load. The effect of effluent inputs on ammonium loads was more significant (10%). Cattle, sheep and permanent grassland dominated the N catchment export, with diffuse-source N export greatly dominating that due to point sources. Cattle, sheep, permanent grassland and cereal crops generated the greatest rates of diffuse-source P export. This reflected the higher rates of P fertiliser applications to arable land and the susceptibility of bare, arable land to P export in wetter winter months. N and P export to the Tamar Estuary from human sewage was insignificant. Non-conservative behaviour of phosphate was particularly marked in the Tamar Estuary. Silicate concentrations were slightly less than conservative levels, whereas nitrate was essentially conservative. The coastal sea acted as a sink for these terrestrially derived nutrients. A pronounced sag in dissolved oxygen that was associated with strong nitrite and ammonium peaks occurred in the turbidity maximum region of the Tamar Estuary. Nutrient behaviour within the Tweed was very different. The low turbidity and rapid flushing ensured that nutrients there were essentially conservative, so that flushing of nutrients to the coastal zone from the river occurred with little estuarine modification.