Colonization, succession, and nutrition of macrobenthic assemblages in a restored wetland at Tijuana Estuary, California

Modes of colonization, the successional trajectory, and trophic recovery of a macrofaunal community were analyzed over 19 months in the Friendship marsh, a 20-acre restored wetland in Tijuana Estuary, California. Traditional techniques for quantifying macrofaunal communities were combined with emerging stable isotopic approaches for evaluation of trophic recovery, making comparisons with a nearby natural Spartina foliosa habitat. Life history-based predictions successfully identified major colonization modes, although most taxa employed a variety of tactics for colonizing the restored marsh. The presence of S. foliosa did not seem to affect macrofaunal colonization or succession at the scale of this study. However, soil organic matter content in the restored marsh was positively correlated with insect densities, and high initial salinities may have limited the success of early colonists. Total macrofaunal densities recovered to natural marsh levels after 14 months and diversity, measured as species richness and the Shannon index (H′), was comparable to the natural marsh by 19 months. Some compositional disparities between the natural and created communities persisted after 19 months, including lower percentages of surface-feeding polychaetes (Polydora spp.) and higher percentages of dipteran insects and turbellarians in the Friendship marsh. As surficial structural similarity of infaunal communities between the Friendship and natural habitat was achieved, isotopic analyses revealed a simultaneous trajectory towards recovery of trophic structure. Enriched δ¹³C signatures of benthic microalgae and infauna, observed in the restored marsh shortly after establishment compared to natural Spartina habitat, recovered after 19 months. However, the depletion in δ¹⁵N signatures of macrofauna in the Friendship marsh indicated consumption of microalgae, particularly nitrogen-fixing cyanobacteria, while macroalgae and Spartina made a larger contribution to macrofaunal diets in the natural habitat. Future successional studies must continue to develop and employ novel combinations of techniques for evaluating structural and functional recovery of disturbed and created habitats.     

Carbon stable isotopes in estuarine sediments and their utility as migration markers for nursery studies in the Firth of Forth and Forth Estuary, Scotland

The stable carbon isotope ratios (δ¹³C) of the organic fraction of intertidal sediments in the Forth Estuary and the Firth of Forth, Scotland, were measured to determine if terrestrially derived carbon was present in the estuarine sediments. It was hypothesised that differences in the inputs from marine vs. terrestrial sources to the organic carbon of estuarine and marine sediments, as well as differences in ambient seawater stable oxygen isotope (δ¹⁸O) ratios between the estuary and the Outer Firth, would allow the use of these two stable isotopes as habitat markers for juvenile plaice (Pleuronectes platessa), to allow determination of nursery habitats. Muddy and sandy sediments from the estuary and sandy sediments from the Outer Firth were sampled and δ¹³C measured. Juvenile plaice were caught at two estuarine sites and at two Outer Firth sites and otoliths were removed for δ¹³C and δ¹⁸O analysis. The sandy sediments in the estuary showed a strong gradient of δ¹³C enrichment with distance down the estuary, while the muddy sediments showed a much shallower gradient. δ¹³C and δ¹⁸O measured in the carbonate of juvenile plaice otoliths showed no clear difference between otoliths of fish caught at one of the estuarine sites and at the two Outer Firth sites. However, the isotope ratios of both carbon and oxygen in plaice otoliths from the other estuarine site showed the expected trend of depletion in the heavier isotopes. While the measurements recorded here did not conclusively distinguish between otoliths from juveniles caught in the estuarine site and those caught in the other three sites, they show that stable isotopes have potential to distinguish between estuarine habitats with terrestrial carbon inputs, and coastal marine habitats with predominantly marine carbon inputs.     

稳定同位素在天然气水合物地球化学勘查中的应用简介--以"布莱克海隆"海区为例

介绍了国外在布莱克海隆（包括ODP164航次994、995、997站位）进行天然气水合物勘查过程中应用稳定同位素的研究实例；通过对这3个站位样品的甲烷、CO2、DIC（dissolved inorganic carbon)、有机碳以及自生碳酸盐的δ^13C分析，指出浅部（0－30m)甲烷和DIC的δ^13C值随深度迅速降低又迅速升高的变化可以作为天然气水合物存在的地球化学指标。994站位孔隙水δ^18O值深度从0.30‰下降到-0.37‰；氢同位素δD随深度略有下降（从11‰到-12‰），这与水合物形成时氢氧重同位素相对富集于固相有关，表明天然气水合物的存在。997站位δ^37Cl从海底沉积物表层以下30m处为接近海水的最大值0，至钻孔底746.85m处降为-3.68‰，可能也与天然气水合物的形成有关。     

Modelling nitrogen and phosphorus cycles and dissolved oxygen in the Zhujiang Estuary Ⅰ.Model results

rmIoxThe averag annual dischaIge of the Zhujiang Xiver is 3. 32 x l0ll m3, which ranks theZhujiang River just end to the Changjiang River in China. The dischnye occutring duringthe fltal m between APril and ffepteTnber accounts for 80% of the yearly total. The Zhu-jiang hiver has a yeaIy sediment load of about 1 x l08 tons, which also concentrates in theM arn (Zhao, l990; Chen et al., 1998). The Zhujiang Xiver delta,which has l2 cities ofdifferent sizes and more than 40 towns with a po…     

ENSO对天目山柳杉树轮同位素的影响

在Nin↑～o3,4区SST序列和Jones等的SOI序列基础上，通过主分量分析方法建立了一个ENSO指数序列。并与根据天目山柳杉树轮碳，氢同位素组成比所建立的树轮指数序列进行相关分析。结果表明，天目山树轮指数与ENSO指数有很好的相关性，尤其与前2年的ENSO指数相关显著。说明ENSO对该地区树木的生长和同位素的分馏有影响，也说明天目山地区的树木年轮对于ENSO事件具有一定的记录能力。     

珠江口河流输沙、河口沉积与粒度信息之间的联系

河口三角洲地区泥沙供应充分，是现代沉积速率较高的区域。快速沉积的泥沙包含高分辨率的环境信息。采用放射性同位素测年方法研究了珠江口伶仃洋大铲湾海域6个柱样的现代沉积速率，以2mm的间隔分析了其中2个柱样上部的粒度，并对其平均粒径和珠江流域的年输沙量进行了快速傅里叶变换，以期获取河流泥沙供应、河口沉积速率和沉积物垂向粒度变化的对应关系。结果表明，大铲湾海域的沉积速率为1～3cm／a，受动力条件和泥沙供应条件的影响显著。2个柱样的平均粒径的最显著重现周期与珠江年输沙量的周期性有较好的对应关系，并可能反映了季节的、年的和多年的沉积速率信息。对于每年沉积厚度在厘米级的环境，以毫米级的高分辨率进行粒度分析，有可能揭示出沉积物供应的季节变化和年际变化。本研究亦可为其他河口的相关工作提供借鉴。     

虾池的溶解氧含量及其补充量和消耗量

对对虾养殖池塘溶解氧含量及其收支情况的研究结果表明，虾池DO值具有明显的季节和昼夜变化。浮游植物光合作用是虾池溶解氧补充的主要来源，夏季最高可超过5mg／（dm3·d）。养殖后期对虾的耗氧量占总耗氧量的34％，底质和池水耗氧量分别占30％和35％。根据虾池氧的收支情况讨论了池养对虾的生产容量。     

A Stable Carbon Isotope Study of the Food-web in a Freshwater-deprived South African Estuary, with Particular Emphasis on the Ichthyofauna

The importance of macrophytes as food sources for estuarine nekton is unclear. Previous carbon isotope investigations in the macrophyte-dominated, freshwater-deprived Kariega Estuary showed that the bivalveSolen cylindraceusdid not utilize the dominant estuarine macrophytes found within the estuary as a primary food source. This finding prompted questions as to what the nekton of this estuary utilize as primary energy sources. δ¹³C analyses of the principal autochthonous and allochthonous primary carbon sources, as well as the dominant invertebrate and fish species, indicate that there are two main carbon pathways within the Kariega Estuary. The littoral community, which incorporates the majority of crustaceans, gobies, mullet and a sparid, utilizes δ¹³C enriched primary food sources namelySpartina maritima,Zosteracapensis and epiphytes. The channel fauna, which includes the zooplankton, zooplanktivorous and piscivorous fish, utilizes a primary food source depleted in δ¹³C, which is most likely a mixture of phytoplankton, terrestrial plant debris and C₄macrophyte detritus. The C₃saltmarsh macrophytesSarcocornia perennisandChenolea diffusa, as well as benthic microalgae, appear to be less important as primary food sources to the nekton of the Kariega Estuary.     

黄海溶解氧垂直分布最大值的成因

本文对黄海溶解氧垂直分布中最大值的成因进行了探讨．认为：浮游植物春花期光合作用产生的大量氧，是溶解氧垂直分布最大值得以在春季（5月）形成的基础；而良好的温、密跃层的存在是氧最大值得以形成的必要条件，夏季叶绿素最大值层中较强的光合作用，是氧最大值在夏季得以维持甚至增强的主要原因．提出：黄海春、夏季溶解氧垂直分布中的最大值并非主要由冬季保持而来．