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.     

珠江河口西南风强迫下潮流场的数值模拟

采用Backhaus三维斜压模型模拟了均匀西南风场对珠江口近岸海域的影响，并与无风情况作了对比；通过对珠江河口盐度场及风生环流的分析比较，结果表明，模型较为真实地再现了夏季珠江河口的水动力学特性。     

Carbon balance in a salt marsh: Interactions of diffusive export, tidal deposition and rainfall-caused erosion

Studies of the concentrations of particulate and dissolved organic carbon in the Duplin River, of the tidal exchange of POC and DOC in the marsh, of the standing stock and movement of Spartina alterniflora wrack in the Duplin, and of the removal of carbon from the surface of the marsh by rain were conducted at Sapelo Island, Georgia in order to test three hypotheses about export of carbon from the Duplin River watershed. We found that the gradients in POC and DOC concentrations are such that carbon is being transported down the Duplin River throughout the year, although in smaller quantities than previously believed. In contrast, almost all tidal exchanges within the marsh result in deposition of carbon. Most of this deposited carbon is subsequently eroded as a result of rain falling on the exposed marsh surface, and is washed back into the tidal creeks. This cycle of deposition and erosion is a possible mechanism keeping POC in the thin aerobic surface layer of the marsh, thus increasing its availability to detritivores and aerobic microbes. The standing stock of wrack is only a fraction of the S. alterniflora produced each year, and its export is a negligible term in the carbon balance equation.     

Tidal fluxes of nutrients and suspended sediments at the North Inlet–Winyah Bay National Estuarine Research Reserve

Beginning June of 1993 suites of 13 water samples have been collected at Oyster Landing, North Inlet (SC), every 20 days covering two consecutive tidal cycles at 2.07 h intervals. In order to ascertain whether this large (and still growing) water chemistry data set can be used to determine tidal fluxes of nutrients and sediments, we coupled measured concentrations to estimates of instantaneous tidal discharge based on a basin water storage curve and hindcast tides. The mean advective fluxes of all constituents, including salt, showed statistically significant exports. This result, however, is largely due to an ebb bias in the sampling protocol, which resulted in 52% of the samples being collected on ebb tide versus a theoretical percentage of 48%. When this bias was corrected by reducing the mean discharge (−610 l s⁻¹) to a value (−125 l s⁻¹) that produced a balance between the mean advective and dispersive salt fluxes, the advective fluxes of the other constituents were reduced to values that are not significantly different from zero. In addition to a statistically significant dispersive influx of salt, significant dispersive exports were found for DON, NH₄, DOP, PO₄ and DOC. All particulate constituents (PN, PP, ISS and OSS) yielded dispersive fluxes that were not significantly different from zero. Annual material budgets for the Oyster Landing basin based on the dispersive fluxes of all constituents (except salt) are generally similar in magnitude and direction to those measured by [Dame, R.F., Spurrier, J.D., Williams, T.M., Kjerfve, B., Zingmark, R.G., Wolaver, T.G., Chrzanowski, T.H., McKeller, H.N., Vernberg, F.J., 1991. Annual material processing by a salt marsh-estuarine basin in South Carolina, USA. Marine Ecology Progress Series 72, 153–166.] in the nearby and ecologically similar Bly Creek basin, indicating that the dispersive fluxes determined in this study are realistic. We offer suggestions for improving the reliability and usefulness of future Oyster Landing water quality data.     

高效液相色谱法测量海洋浮游植物色素浓度

JGOFS计算和SeaWiFS计划推荐高效液相色谱（HPLC）作为海洋浮游植物色色浓度的测量方法。文章参考SeaWiFS计划制定的HPLC分析规范，叙述采用反相C18ODS色谱柱、996PDA、自动进样器（未配柱温箱）和三元梯度的色谱法测量海洋浮游植物色素浓度的具体实践。     

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.     

Seasonal methyltin and (3-dimethylsulphonio)propionate concentrations in leaf tissue of Spartina alterniflora of the Great Bay estuary (NH)

Concentrations of total recoverable inorganic tin (TRISn), monomethyltin (MeSn³⁺), dimethyltin (Me₂Sn²⁺), trimethyltin (Me₃Sn⁺) and (3-dimethylsulphonio)propionate (DMSP) were determined in leaves of Spartina alterniflora from three sites in the Great Bay estuary (NH) from 8 May to 15 September 1989. Total methyltin concentration increased from 8·9 ng g⁻¹ (fresh weight) on 8 May to 472 ng g⁻¹ on 23 May, decreased to 52 ng g⁻¹ on 7 June and 16ng g⁻¹ on 20 June, and remained low until the last sample on 18 September. Statistical calculations showed that methyltin concentrations varied significantly with sampling week, but not with site. DMSP concentrations showed very different behaviour. During the same sampling period DMSP concentrations varied only from 7·5 to 26 μmol g⁻¹ (fresh weight). DMSP concentrations varied significantly for site, but not sampling week.     

Nutrients and zooplankton composition and dynamics in relation to the hydrological pattern in a confined Mediterranean salt marsh (NE Iberian Peninsula)

The role of the hydrological regime in the nutrients and zooplankton composition and dynamics has been analysed in five lagoons of La Pletera salt marshes (NE Iberian Peninsula) during a complete hydrological cycle (2002–2003). Two of the lagoons have their origin in the old river mouths while the other three were recently created in the framework of a Life Restoration project. This fact has also allowed us to study the effect of the lagoon age on nutrient and zooplankton composition and dynamics. The salt marsh hydrology is determined by a prolonged period of confinement without water inputs, irregularly interrupted by sudden water inputs due to flooding events (sea storms or intense rainfalls). While the dynamics of oxidized nitrogen compounds in the lagoons depends on the water inputs variability within each hydrological cycle, the internal load of phosphorus, total nitrogen and organic matter is related more to the cumulative mechanisms during the confinement periods. Accumulation processes may be easily related to lagoon age, since old lagoons have higher content of nutrients and organic matter, suggesting that these lagoons progressively accumulate nutrients during the successive confinement events. This is the usual case for most Mediterranean salt marshes without an artificially manipulated water regime. The zooplankton community in La Pletera integrates the effects of both the hydrological regime and the lagoon age since the former determines the temporal pattern of the main zooplankton species and the latter explains differences in composition and structure between old and new lagoons.