Production of glycine betaine and dimethylsulfoniopropionate in marine phytoplankton. I. Batch cultures

The quantitative significance of the nitrogenous compound glycine betaine (GBT) and its sulfur analog dimethylsulfoniopropionate (DMSP) to intracellular pools in marine phytoplankton is not well known. In a series of experiments conducted in August 1993, we measured these compounds, as well as total organic sulfur, carbon, and nitrogen, over the growth cycle in six isolates of marine phytoplankton, Amphidinium carterae Hulburt, Chrysochromulina sp. Lackey, Emiliania huxleyi Hay et Mohler, Prorocentrum minimum (Pavillard) Schiller, Skeletonema costatum (Greville) Cleve, and Tetraselmis sp. At the same time, we measured cellular concentrations of protein, amino acids, chlorophyll, and inorganic nutrients. All six species produced DMSP, while three produced GBT at lesser levels. In the Chrysochromulina sp. isolate, levels of GBT were greater than DMSP during the exponential phase of growth, but declined sharply as the culture approached stationary phase. This change appeared to coincide with the onset of nitrogen limitation. Other nitrogenous osmolytes were produced in five of the six species but in much smaller quantities. DMSP contributed significantly to cellular sulfur throughout the growth cycle although, in some algae, the proportion of dissolved DMSP increased substantially during stationary growth. When present, GBT formed a sizeable fraction of the cellular nitrogen only during exponential growth. A significant percentage (ca. 50%) of the organic nitrogen could not be accounted for even when cellular pools of protein, amino acids, inorganic nitrogen, and nitrogenous osmolytes were combined. Based on these experiments, there does not appear to be a reciprocal relationship between DMSP and GBT production, although GBT production does appear to be correlated with nitrogen availability. Received: 5 January 1998 / Accepted: 29 June 1999     

Management von schadstoffbelasteten Feinsedimenten in Bundeswasserstraßen

The Federal Institute of Hydrology has developed operating strategies in order to deal with dredged material within the scope of the Waterways and Shipping Administration. Sediments will be assessed based on certain quality parameters. The potential environmental impact at the source and relocation areas has to be evaluated in respect to ecological and economical issues. A coordinated sediment management plan for the Rhine River was commissioned. The most important contaminated sedimentation areas were identified, and special sedimentation areas were classified based on ecological impact or even risk. Proposals for economical and ecological strategies are discussed. Further developments for operational instructions dealing with sediments and dredged material in federal waterways are still being processed. The objectives of the river basin commissions as well as those of the stakeholders have to be met in an appropriate manner. In the framework of the analysis and impact of climate change on both sediment quantity and quality for optimizing sediment management, one or more dimensional hydraulic models will be applied. This will help gain a better insight into the understanding of contaminant transport in freshwater bodies.     

The role of silicon in the supply of terrestrial ecosystem services

Environmental Chemistry Letters - Silicon (Si) is the most abundant element on the earth’s surface after oxygen. Si  can be found in minerals, electronic chips, cosmetic...     

Changes in the rhizosphere of metal-accumulating plants evidenced by chemical extractants

The plants Salix viminalis L. (common osier) and Thlaspi caerulescens J. Presl & C. Presl have been studied often because of their high potential to extract heavy metals from soils. The soil properties favoring this phytoextraction are not yet fully known. In this study we compared three frequently used single-extracting agents (NaNO3, diethylenetriaminepentaacetic acid [DTPA], and ethylenediaminetetra-acetic acid [EDTA]) with a sequential extraction procedure to describe changes in the different Cd, Cu, and Zn pools in the rhizosphere of S. viminalis and T. caerulescens grown on calcareous and acidic Swiss soils in a pot experiment. The sequential extraction was used to assess the chemical affinities of these heavy metals (HM) in the soil whereas the single extractants were used for estimating the bioavailable HM pools in the soils. Cadmium depletion in several pools was most apparent in the acidic soil, with a significant decrease observed in the NaNO3-, DTPA-, and EDTA-extractable fractions following T. caerulescens growth compared with control pots. The sequential extraction showed that most Cd extracted by the plant from the acidic soil originated from the organic pool, which implies that heavy metals bound to organic matter may constitute a significant part of the bioavailable Cd pool in soils. In the calcareous soil only a small amount of Cd was taken up by T. caerulescens, and this came mainly from the carbonate-bound fraction. This study shows that T. caerulescens, and to a lesser extent S. viminalis, can alter the heavy metal distribution in different soil pools within 90 d.     

Evidence of biological recovery in acid-stressed lakes near Sudbury, Canada

Reductions in the emissions of SO2 and trace metals from the Sudbury smelters have resulted in substantial improvements in water quality in many surrounding lakes. Significant biological changes have accompanied the chemical improvements. Evidence of relatively rapid recovery was found for benthic filamentous algae, phytoplankton, zooplankton, mobile species of benthic invertebrates, and some fish populations. Organisms with low dispersal ability (e.g. Hyalella azteca) have not yet recolonized these lakes. The partial recovery observed to date shows movement toward re-establishment of biological communities typical of natural Precambrian Shield lakes in this area. These findings offer strong support for further efforts to reduce industrial emissions of pollutants to the atmosphere.     

Phytoplankton carbon dynamics during a winter-spring diatom bloom in an enclosed marine ecosystem: primary production,biomass and loss rates

Phytoplankton production, standing crop, and loss processes (respiration, sedimentation, grazing by zooplankton, and excretion) were measured on a daily basis during the growth, dormancy and decline of a winter-spring diatom bloom in a large-scale (13 m³) marine mesocosm in 1987. Carbonspecific rates of production and biomass change were highly correlated whereas production and loss rates were unrelated over the experimental period when the significant changes in algal biomass characteristic of phytoplankton blooms were occurring. The observed decline in diatom growth rates was caused by nutrient limitation. Daily phytoplankton production rates calculated from the phytoplankton continuity equation were in excellent agreement with rates independently determined using standard ¹⁴C techniques. A carbon budget for the winter bloom indicated that 82.4% of the net daytime primary production was accounted for by measured loss processes, 1.3% was present as standing crop at the end of the experiment, and 16.3% was unexplained. Losses via sedimentation (44.8%) and nighttime phytoplankton respiration (24.1%) predominated, while losses due to zooplankton grazing (10.7%) and nighttime phytoplankton excretion (2.8%) were of lesser importance. A model simulating daily phytoplankton biomass was developed to demonstrate the relative importance of the individual loss processes.     

A Multidisciplinary Study of Spatial and Temporal Scales Containing Information in Turbulent Chemical Plume Tracking

This report describes the results of a multidisciplinary study of turbulent chemical plume tracking of blue crabs and autonomous agents. The study consists of a coordinated investigation of animal behavior, fluid mechanics, strategy simulations, and chemical sensing. The objective is to provide a comprehensive understanding of chemical plume tracking in a single biological system and to prescribe strategies that are effective for autonomous agents. The consensus of the study is that spatial variation in the plume, measured by sampling at multiple locations simultaneously, yields information that is useful for plume tracking. Behavioral investigations reveal that blue crabs demonstrate the ability to detect the chemical plume and use lateral movements to avoid losing contact with the odor. Blue crabs move rapidly towards the source, strongly suggesting that temporal comparisons of odor properties are not employed during navigation. Analysis of the concentration fields reveals that a spatial correlation between spanwise-separated sensors indicates the relative direction of the plume centerline over short time periods provided the sensor spacing is scaled appropriately relative to the plume. Similarly, simulations of tracking strategies reveal an optimal separation for the sensors at a distance roughly equal to the plume width; both smaller and larger sensor spans degrade tracking performance. The simulations further reveal an optimal sensor size above which the fine details of the concentration distribution are obscured and below which there is insufficient contact with the odor to enable effective navigation. Finally, analysis of the chemical signal shows that the frequency dependent correlation function between two (or more) sensors indicates the relative position of the source.     

Mixed-function oxidase-specific activity in wild and caged speckled sanddabs Citharichthys stigmaeus in Elkhorn Slough, Moss Landing Harbor and nearshore Monterey Bay, California

The goal of this study was to characterize the spatial, seasonal and annual hepatic activities of mixed-function oxidase (MFO) in the speckled sanddab Citharichthys stigmaeus, the most common fish in the Moss Landing area. In addition, techniques to monitor MFO activities in caged speckled sanddabs were developed and tested. Once the relationship between MFO activities in caged and wild fish populations is determined, caged fish could be used to monitor potential hydrocarbon impacts at Moss Landing, or other marine sites. During each of the spatial, seasonal and annual sediment samplings conducted in 1985-1987 as part of a separate hydrocarbon variability study at Moss Landing, 12 wild speckled sanddabs were collected from Moss Landing Harbor, Elkhorn Slough and nearshore Monterey Bay sites. In addition, four locations were chosen for a 14-day field caged fish experiment. The caged fish experiments successfully demonstrated the feasibility of using caged sanddabs as indicators of hydrocarbon exposure. The major source of variability in hepatic aryl hydrocarbon hydroxylase activity in wild speckled sanddabs from the Moss Landing area is due to seasonal rather than site differences. Significant relationships between caged fish MFO response and sediment hydrocarbon concentrations were found. It is possible that caged fish could be used in place of costly sediment sampling and analysis, and provide a more direct method to assess biological impacts. Many of the caging techniques demonstrated in this study can easily be transferred to other benthic flatfish, and other marine and freshwater environments.     

Metal availability and soil toxicity after repeated croppings of Thlaspi caerulescens in metal contaminated soils

Metal phytoextraction with hyperaccumulating plants could be a useful method to decontaminate soils, but it is not fully validated yet. In order to quantify the efficiency of Cd and Zn extraction from a calcareous soil with and without Fe amendment and an acidic soil, we performed a pot experiment with three successive croppings of Thlaspi caerulescens followed by 3 months without plant and 7 weeks with lettuce. We used a combined approach to assess total extraction efficiency (2 M HNO3-extractable metals), changes in metal bio/availability (0.1 M NaNO3-extractable metals and lettuce uptake) and toxicity (lettuce biomass and the BIOMET biosensor). The soil solution was monitored over the whole experiment. In the calcareous soil large Cu concentrations were probably responsible for chlorosis symptoms observed on T. caerulescens. When this soil was treated with Fe, the amount of extracted metal by T. caerulescens increased and metal availability and soil toxicity decreased when compared to the untreated soil. In the acidic soil, T. caerulescens was most efficient: Cd and Zn concentrations in plants were in the range of hyperaccumulation and HNO3-extractable Cd and Zn, metal bio/availability, soil toxicity, and Cd and Zn concentrations in the soil solution decreased significantly. However, a reduced Cd concentration measured in the third T. caerulescens cropping indicated a decrease in metal availability below a critical threshold, whereas the increase of dissolved Cd and Zn concentrations after the third cropping may be the early sign of soil re-equilibration. This indicates that phytoextraction efficiency must be assessed by different approaches in order not to overlook any potential hazard and that an efficient phytoextraction scheme will have to take into account the different dynamics of the soil-plant system.