Towards an indicator for functional diversity of microbial populations

The provisional results have been described of the development of an indicator for the functional diversity of microbial populations by use of Biolog microtiterplates. Aquatic as well as terrestrial environmental samples were tested. The report describes the experimental procedure and the manipulation of the measured data. Two diversity indicators are distinguished, both calculated from the log logistic relation of the measured activity and the number of colony forming units (CFU). One indicator is the slope in the point of inflection and the other is the logarithm of the CFU necessary for 50% of the maximal activity. The functionality of the proposed indicators is discussed.De voorlopige resultaten zijn beschreven van de ontwikkeling van een indicator voor de functionele diversiteit van microbiele populaties met behulp van microtiterplaten van Biolog. Voor dit doel werden zowel aquatische als terrestrische milieu monsters getoetst. Het rapport beschrijft de experimentele procedure en de uitwerking van de meetgegevens. In het rapport worden twee biodiversiteitsindicatoren onderscheiden, berekend uit de log-logistische relatie tussen de gemeten activiteit en het aantal kolonie vormende eenheden (CFU). Een indicator is de helling in het buigpunt, de andere indicator is de logaritme van de CFU die nodig is om 50% van de maximale activiteit te bereiken. De functionaliteit van de indicatoren wordt bediscussieerd

Towards an indicator for functional diversity of microbial populations

De voorlopige resultaten zijn beschreven van de ontwikkeling van een indicator voor de functionele diversiteit van microbiele populaties met behulp van microtiterplaten van Biolog. Voor dit doel werden zowel aquatische als terrestrische milieu monsters getoetst. Het rapport beschrijft de experimentele procedure en de uitwerking van de meetgegevens. In het rapport worden twee biodiversiteitsindicatoren onderscheiden, berekend uit de log-logistische relatie tussen de gemeten activiteit en het aantal kolonie vormende eenheden (CFU). Een indicator is de helling in het buigpunt, de andere indicator is de logaritme van de CFU die nodig is om 50% van de maximale activiteit te bereiken. De functionaliteit van de indicatoren wordt bediscussieerd.The provisional results have been described of the development of an indicator for the functional diversity of microbial populations by use of Biolog microtiterplates. Aquatic as well as terrestrial environmental samples were tested. The report describes the experimental procedure and the manipulation of the measured data. Two diversity indicators are distinguished, both calculated from the log logistic relation of the measured activity and the number of colony forming units (CFU). One indicator is the slope in the point of inflection and the other is the logarithm of the CFU necessary for 50% of the maximal activity. The functionality of the proposed indicators is discussed.DGM/SV

Naar een indicator voor functionele diversiteit van microbiele gemeenschappen

De voorlopige resultaten zijn beschreven van de ontwikkeling van een indicator voor de functionele diversiteit van microbiele populaties met behulp van microtiterplaten van Biolog. Voor dit doel werden zowel aquatische als terrestrische milieu monsters getoetst. Het rapport beschrijft de experimentele procedure en de uitwerking van de meetgegevens. In het rapport worden twee biodiversiteitsindicatoren onderscheiden, berekend uit de log-logistische relatie tussen de gemeten activiteit en het aantal kolonie vormende eenheden (CFU). Een indicator is de helling in het buigpunt, de andere indicator is de logaritme van de CFU die nodig is om 50% van de maximale activiteit te bereiken. De functionaliteit van de indicatoren wordt bediscussieerd.<br

The effects of a pesticide mixture on aquatic ecosystems differing in trophic status: responses of the macrophyte Myriophyllum spicatum and the periphytic algal community

The effects of a pesticide mixture (asulam, fluazinam, lambda-cyhalothrin, and metamitron) on aquatic ecosystems were investigated in 20 outdoor aquatic microcosms. Ten of the microcosms simulated mesotrophic aquatic ecosystems dominated by submerged macrophytes (Elodea). The others simulated eutrophic ecosystems with a high Lemna surface coverage (Lemna). This paper describes the fate of the chemicals as well as their effects on the growth of Myriophyllum spicatum and the periphytic algal community. In the Elodea-dominated microcosms significant increase in the biomass and alterations of species composition of the periphytic algae were observed, but no effect on M. spicatum growth could be recorded in response to the treatment. The opposite was found in the Lemna-dominated microcosms, in which decreased growth of M. spicatum was observed but no alterations could be found in the periphytic community. In the Elodea-dominated microcosms the species composition of the periphytic algae diverged from that of the control following treatment with 0.5% spray drift emission of the label-recommended rate (5% for lambda-cyhalothrin), while reduced growth of M. spicatum in the Lemna-dominated microcosms was recorded at 2% drift (20% for lambda-cyhalothrin). This study shows that the structure of the ecosystem influences the final effect of pesticide exposure. (C) 2003 Elsevier Inc. All rights reserved

Managing ditches for agroecological engineering of landscape. A review

International audienceAbstractAgriculture must now feed the planet with the lowest environmental impact. Landscape management is a means to protect natural resources from the adverse impacts. In particular, the adequate management of ditches could improve crop quality. Here, we review ditch design and maintenance. We found the following major points: (1) ditch networks have been primarily designed for waterlogging control and erosion prevention. Nonetheless, when properly managed, farm ditches provide other important ecosystem services, namely groundwater recharge, flood attenuation, water purification, or biodiversity conservation. (2) All ditch ecosystem services depend on many geochemical, geophysical, and biological processes, whose occurrence and intensity vary largely with ditch characteristics. (3) The major ruling characteristics are vegetative cover; ditch morphology; slope orientation; reach connections such as piped sections and weirs, soil, sediment and litter properties, biota, and biofilms; and network topology. (4) Ditch maintenance is an efficient engineering tool to optimize ecosystem services because several ditch characteristics change widely with ditch maintenance. For instance, maintenance operations, dredging, chemical weeding, and burning improve waterlogging and soil erosion control, but they are negative for biodiversity conservation. Mowing has low adverse effects on biodiversity conservation and water purification when mowing is performed at an adequate season. The effects of burning have been poorly investigated

Herbicide Exposure and Toxicity to Aquatic Primary Producers

The aim of the present review was to give an overview of the current state of science concerning herbicide exposure and toxicity to aquatic primary producers. To this end we assessed the open literature, revealing the widespread presence of (mixtures of) herbicides, inevitably leading to the exposure of non-target primary producers. Yet, herbicide concentrations show strong temporal and spatial variations. Concerning herbicide toxicity, it was concluded that the most sensitive as well as the least sensitive species differed per herbicide and that the observed effect concentrations for some herbicides were rather independent from the exposure time. More extensive ecotoxicity testing is required, especially considering macrophytes and marine herbicide toxicity. Hence, it was concluded that the largest knowledge gap concerns the effects of sediment-associated herbicides on primary producers in the marine/estuarine environment. Generally, there is no actual risk of waterborne herbicides to aquatic primary producers. Still, median concentrations of atrazine and especially of diuron measured in China, the USA and Europe represented moderate risks for primary producers. Maximum concentrations due to misuse and accidents may even cause the exceedance of almost 60% of the effect concentrations plotted in SSDs. Using bioassays to determine the effect of contaminated water and sediment and to identify the herbicides of concern is a promising addition to chemical analysis, especially for the photosynthesis-inhibiting herbicides using photosynthesis as endpoint in the bioassays. This review concluded that to come to a reliable herbicide hazard and risk assessment, an extensive catch-up must be made concerning macrophytes, the marine environment and especially sediment as overlooked and understudied environmental compartments