Functional bioassays utilizing zooplankton: a comparison

Functional zooplankton bioassays based on ingestion, reproduction and respiration are described, with methods for a new ingestion bioassay included. All bioassays are compared using three indices, including the variability of controls, the range of experimental responses, and a listing of contaminants causing inhibition/stimulation of response. The ingestion bioassay showed the greatest range of response, and was sensitive to pesticides, PCBs and heavy metals. It was also commonly characterized by a hormesis response. The reproduction bioassay showed the lowest variability, illustrated a reduced range of response, and was sensitive to nutrients and heavy metals. In one study, the respiration bioassay was sensitive only to PCBs.     

沙漠腹地天然绿洲胡杨和柽柳叶片δ13C值对不同地下水埋深的响应

干旱区植物的水分利用效率对植物的分布及水分利用状况具有重要意义。基于不同地下水埋深条件下沙漠腹地绿洲优势种胡杨和柽柳叶片δ¹³C值,分析了胡杨和柽柳的水分利用效率对不同地下水埋深的响应。结果表明: 随着地下水埋深由2.1 m增加到4.3 m,柽柳叶片的δ¹³C值先略有增加后处于较为稳定状态,柽柳采取较为稳定的水分利用效率适应干旱环境;胡杨叶片的δ¹³C值呈现先略有减小后增加的趋势,胡杨通过提高水分利用效率的策略适应干旱胁迫。同一地下水埋深条件下柽柳叶片的δ¹³C值高于胡杨叶片,表明柽柳的水分利用效率高于胡杨。     

地下水位对黄河三角洲柽柳根系生长的影响

为揭示黄河三角洲柽柳根系生长特征对地下水位的响应规律,明确柽柳生长适宜的地下水位,在咸水矿化度（6 g/L）下,模拟设置0、0.3、0.6、0.9、1.2、1.5、1.8 m共7个地下水位。测定分析栽植柽柳土柱的水盐参数与根系生长指标。结果表明：在咸水矿化度下,地下水位可显著影响土壤水盐变化,从而影响柽柳根系的生长。随地下水位的降低,土壤含水量、含盐量和土壤溶液绝对浓度显著降低。在高水位（≤0.6 m）下,柽柳根系生长受水盐胁迫影响显著,柽柳根长、根径、侧根数、总生物量、侧根生物量、根系连接长度均较低,拓扑结构呈叉状分支;中水位（0.9 m）时,土壤水盐条件适宜,柽柳侧根数、根径、二级侧根和毛细根生物量达到最大值,拓扑结构由叉状分支向鱼尾形分支过渡;低水位（≥1.2 m）下,土壤水盐含量低,柽柳根系总生物量、主根生物量、一级侧根生物量和根系平均连接长度在1.2 m水位达到最大值后降低,拓扑结构呈鱼尾形分支。柽柳根系生长与地下水位密切相关,柽柳通过改变根系生长和调整构型来适应不同土壤水盐和地下水位条件。高水位（≤0.6 m）下柽柳以降低根系生长深度,增加分叉,调配各组织器官的生物量来适应水盐胁迫;中水位0.9 m下土壤水盐条件最适宜柽柳生长;低水位（≥1.2 m）下柽柳主要受土壤干旱胁迫而使根系向下生长,增加根系连接长度,以此扩大资源获取效率。柽柳根系生长及根系构型对咸水矿化度下不同地下水位表现出较强的适应性和可塑性。     

Estuary–ocean connectivity: fast physics,slow biology

Estuaries are connected to both land and ocean so their physical, chemical, and biological dynamics are influenced by climate patterns over watersheds and ocean basins. We explored climate‐driven oceanic variability as a source of estuarine variability by comparing monthly time series of temperature and chlorophyll‐a inside San Francisco Bay with those in adjacent shelf waters of the California Current System (CCS) that are strongly responsive to wind‐driven upwelling. Monthly temperature fluctuations inside and outside the Bay were synchronous, but their correlations weakened with distance from the ocean. These results illustrate how variability of coastal water temperature (and associated properties such as nitrate and oxygen) propagates into estuaries through fast water exchanges that dissipate along the estuary. Unexpectedly, there was no correlation between monthly chlorophyll‐a variability inside and outside the Bay. However, at the annual scale Bay chlorophyll‐a was significantly correlated with the Spring Transition Index (STI) that sets biological production supporting fish recruitment in the CCS. Wind forcing of the CCS shifted in the late 1990s when the STI advanced 40 days. This shift was followed, with lags of 1–3 years, by 3‐ to 19‐fold increased abundances of five ocean‐produced demersal fish and crustaceans and 2.5‐fold increase of summer chlorophyll‐a in the Bay. These changes reflect a slow biological process of estuary–ocean connectivity operating through the immigration of fish and crustaceans that prey on bivalves, reduce their grazing pressure, and allow phytoplankton biomass to build. We identified clear signals of climate‐mediated oceanic variability in this estuary and discovered that the response patterns vary with the process of connectivity and the timescale of ocean variability. This result has important implications for managing nutrient inputs to estuaries connected to upwelling systems, and for assessing their responses to changing patterns of upwelling timing and intensity as the planet continues to warm.     

芦苇型湿地生态系统的潜水水质状态研究

以白洋淀芦苇滩地为实验地,研究了湿地生态系统中潜水的水质状况.苇地潜水运动受到芦苇根孔的强烈影响.受芦苇根区生物呼吸作用的影响,潜水pH值(6.94士0.14)显著低于淀水(9.17).潜水中CO2分压约为淀水的85～1039倍.潜水水质类型在离淀2.7至6.7m发生变化,逐渐由ClN3转变为CCa.自苇地边缘至中央,HT(总硬度),Ar(总碱度)与∑C(主要离子总量)逐渐升高.潜水中Mg2+/Ca2+的平均摩尔比值为0.60,明显低于淀水(1.31).淀水和潜水Cl-,SO2-,Na++K+含量无显著差异,平均值分别是176,116和112mg/L.苇地濒水区为一过渡带,对磷氮污染物具备首先的过滤作用.在离淀0.7m处TN,TP和活性磷酸盐的减少量分别为63.3%,84.6%,80.8%.     

The hyporheic zone as a source of dissolved organic carbon and carbon gases to a temperate forested stream

The objective of this study was to examine chemical changes in porewaters that occur over small scales (cm) as groundwater flows through the hyporheic zone and discharges to a stream in a temperate forest of northern Wisconsin. Hyporheic-zone porewaters were sampled at discrete depths of 2, 10, 15, 61, and 183 cm at three study sites in the study basin. Chemical profiles of dissolved organic carbon (DOC), CO₂, CH₄, and pH show dramatic changes between 61 cm sediment depth and the water-sediment interface. Unless discrete samples at small depth intervals are taken, these chemical profiles are not accounted for. Similar trends were observed at the three study locations, despite each site having very different hydraulic-flow regimes. Increases in DOC concentration by an order of magnitude from 61 to 15 cm depth with a corresponding decrease in pH and rapid decreases in the molecular weight of the DOC suggest that aliphatic compounds (likely organic acids) are being generated in the hyporheic zone. Estimated efflux rates of DOC, CO₂, and CH₄ to the stream are 6.2, 0.79, 0.13 moles m² d^-1, respectively, with the vast majority of these materials produced in the hyporheic zone. Very little of these materials are accounted for by sampling stream water, suggesting rapid uptake and/or volatilization.     

Abundance and Diversity of Sulfate-Reducing Bacteria in High Arsenic Shallow Aquifers

The abundance, diversity, and relative distribution of sulfate-reducing bacteria (SRB) in high arsenic (As) groundwater aquifers of Hangjinhouqi County in the Hetao Basin, Inner Mongolia was investigated using denaturing gradient gel electrophoresis (DGGE) and quantitative polymerase chain reaction (qPCR) analysis of dsrB genes (encoding dissimilatory sulfite reductase beta-subunit). DGGE results revealed that SRB populations were diverse, but were mainly composed of Desulfotomaculum, Desulfobulbus, Desulfosarcina, and Desulfobacca. The abundance of Desulfobulbus was positively correlated with the ratio of Fe(II)/Fe(III). Although qPCR results showed that the dsrB gene abundance in groundwater samples ranged from below detection to 4.9 × 10⁶ copies/L, and the highest percentage of dsrB gene copies to bacterial 16S rRNA gene copies was 2.1%. Geochemical analyses showed that As(III) content and the ratio of Fe(II) to Fe(III) increased with total As, while sulfate concentrations decreased. Interestingly, the dsrB gene abundance was positively correlated with As concentrations. These results indicate that sulfate reduction occurs simultaneously with As and Fe reduction, and might result in increased As release and mobilization when As is not incorporated into iron sulfides. This study improves our understanding of SRB and As cycling in high As groundwater systems.     

Comparison Between Tidally Driven Groundwater Flow and Flushing of Animal Burrows in Tropical Mangrove Swamps

Tidal groundwater in a mangrove swamp can return to the mangrove creek by one of two mechanisms: (a) it can either flow through the swamp soil due to the water table difference between the creek and the groundwater in the swamp; or (b) it can flow via tidal flushing of animal burrows. This paper compares the magnitude of these two mechanisms for different regions of a mangrove swamp. Direct groundwater flow rates resulting from water stored in the sediment as a consequence of infiltration, especially during and after tidal inundation, were calculated for every square meter in the surface of a mangrove forest from piezometer data. Flow rates of water due to burrow flushing were determined based on published surveys, by estimating the burrow volume and the percentage of the burrow water that is flushed at each tidal inundation. Although direct groundwater flux was found to decrease further away from the creek compared to close to the creek, it was also found to have a similar range as burrow flushing flow. Specifically, direct groundwater flow ranged from 0.004 to 0.04 m³/m²/day, whilst burrow flushing flux ranged from 0.01 to 0.04 m³/m²/day.Considering the errors involved in the experiments and calculations, these ranges can be considered as being the same and neither of the two processes can be considered as negligible compared to the other. As a consequence, surveys of groundwater processes in mangrove areas, and more generally in swamp and tidal areas where animal burrows are present, will need to consider both mechanisms. Investigations of the influence over flushing mechanisms of different residence times of the water in burrows and in the sediment body would also be recommended in order to establish salt and nutrient budget in mangrove swamps.     

Trace metals in marine,brackish and freshwater prawns (Crustacea,Decapoda) from northeast Algeria

The concentrations of the trace metals Zn, Cu, Fe, Cd and Pb were measured in four caridean decapods; Atyaephyra desmaresti, Palaemonetes varians, Parapenaeus longirostris and Aristeus antennatus, from freshwater , estuarine and marine habitats in northeast Algeria variably affected by anthropogenic metal contamination. The two coastal species (P. longirostris and A. antennatus) are a food source for the local population. Accumulated metal concentrations varied interspecifically, and intraspecifically between sites and between seasons, except in the case of Aristeus antennatus. The fresh and brackish water species (Atyaephyra desmaresti and Palaemonetes varians) accumulated more Cd and Pb than their marine counterparts. Results are discussed with respect to anthropogenic inputs and the environmental conditions of the regions studied.     

A Delphi Approach to Understanding Varying Expert Viewpoints in Sustainability Communication: The Case of Water Footprints of Bio‐Based Fiber Resources

In recent years, the concepts of accounting for water use and assessing its impact, also known as the water footprint (WF), have evolved. The cultivation of wood and cotton are two important bio‐based fiber resources that can use, consume, and pollute huge amounts of water. The purpose of this study is to identify the methodological options on an inventory level asociated with a WF assessment for bio‐based fiber resources. Using a three‐step Argument Delphi approach with international experts, important, but controversial, aspects of water footprinting are elaborated. During the different rounds of the Delphi procedure, the interlacement of the crucial topics became apparent, including the net green water or the total volume of green water, trade‐offs between water use and land‐use impacts, allocation of the green WF on ecosystem services, and nomination of a reference situation (e.g., potential natural vegetation). Further, this study evaluates whether the experts allowed generalizations about these methodological options. Finally, the agreement of experts on some generalized statements showed that such statements can be used legitimately as long as knowledge of the inventory methods and knowledge of production characteristics are carefully combined.