Spatio-temporal Patterns of Protozoan Communities in a Meso-eutrophic Reservoir (Esch-sur-Sûre,Luxembourg)

The spatio-temporal distribution of the heterotrophic nanoflagellates (HNF) and ciliates was monitored in the reservoir of Esch-sur-Sûre during the year 1999. Three main periods of protozoan development were observed, in early April, early May, and in July. On the basis of the seasonal dynamics, it appeared that the early spring development of protozoa was probably not controlled by resources or predators. The second protozoan development was progressively controlled by the increase of metazooplankton density that led to the clear water phase characterised by very low protozoan densities and biomasses. A summer development of protozoa was possible thanks to the development of bacteria and moderate metazooplankton densities due to the appearance of non-edible algae. Prorodontida, Halteriida and Strombidiida were the dominant ciliates in the upper part of the water column. A development of Tintinnida was moreover observed in spring whereas Philasterida and Sessilida developed in winter and summer. Ciliates occupied the entire water column in spring and were concentrated in the epilimnion and the metalimnion during the summer period where they fed on bacteria and algae.     

Control of eutrophication by silver carp (Hypophthalmichthys molitrix) in the tropical Paranoá Reservoir (Brasília,Brazil): a mesocosm experiment

A mesocosm experiment was conducted to assess the impact of moderate silver carp (Hypophthalmichthys molitrix) biomass (41 g m^–3 or 850 kg ha^–1) on the plankton community and water quality of eutrophic Paranoá Reservoir (Brasília, Brazil). Microzooplankton (copepod nauplii and rotifers <200 m), netphytoplankton (> 20 m), total phytoplankton biomass (expressed as chlorophyll-a) and net primary productivity were significantly reduced by silver carp. Apart from increased nitrogen in the sediment, nutrients and chemical properties of the water were not affected by fish presence. The observed improvements in water quality suggest that stocking silver carp in Paranoá Reservoir to control blue-green algae is a promising biomanipulation practice.     

Inhibitory factors affecting the process of enhanced biological phosphorus removal (EBPR) – A mini-review

Enhanced biological phosphorus removal (EBPR) technology has been widely considered as a key strategy in preventing eutrophication and recognized as the advancing front of research in wastewater treatment. The key to keep its high efficiency in biological phosphorus removal is to optimize the operation and management of the system. Previous research in this field has undoubtedly improved understanding of the factors hindered overall efficiency of EBPR. However, it is obvious that much remains to be learnt. This paper attempts to review the fundamental understanding in factors inhibiting the stability and reliability of the EBPR systems in the state-of-the-art research. In view of modeling the EBPR systems, an appropriate extension of the current mechanistic models with these inhibitory factors is recommended in order to better simulate and predict the behavior of full-scale and lab-scale EBPR plants. From the perspectives of the further mechanistic and multi-factors study, the direction of denitrifying dephosphatation and granules/biofilms are also discussed. This comprehensive overview will not only help us to understand the overall mechanism of the EBPR process, but also benefit the researchers and engineers to consider all the possible factors affecting the process in the urban sewage treatment plants.     

Does the seston of Lake Biwa release dissolved inorganic nitrogen and phosphorus during aerobic decomposition?: Its implication for eutrophication

Seston was collected from depths of 5 and 60 m in the north basin and a depth of 0 m in the south basin of Lake Biwa in the summer of 1985 and decomposed in the laboratory under aerobic conditions for three months. There was no net release of dissolved inorganic phosphorus from any seston, in contrast with the liberation of dissolved inorganic nitrogen. From this result and other available data, it is suggested that almost all phosphorus entering Lake Biwa and remaining within it is finally transformed into particulate phosphorous, transported to the bottom sediments, and fixed there without being recycled. Thus, this mechanism seems to play an important role in the prevention of rapid eutrophication of Lake Biwa, in spite of high external phosphorus loading.     

Control of microbial communities by the macrofauna: a sensitive interaction in the context of extreme summer temperatures?

Climate models predict an increasing frequency of extremely hot summer events in the northern hemisphere for the near future. We hypothesised that microbial grazing by the metazoan macrofauna is an interaction that becomes unbalanced at high temperatures due to the different development of the grazing rates of the metazoans and the growth rates of the microbial community with increasing temperature. In order to test this hypothesis, we performed grazing experiments in which we measured the impact of increasing temperatures on the development of the grazing rates of riverine mussels in relation to the growth rates of a unicellular prey community (a natural heterotrophic flagellate community from a large river). In a first experimental series using Corbicula fluminea as a grazer and under the addition of a carbon source (yeast extract), the increase of the prey’s growth rates was considerably stronger than that of the predator’s grazing rates when temperatures were increased from 19 to over 25°C. This was also the outcome when the mussels had been acclimatized to warm temperatures. Hereafter, specific experiments with natural river water at temperatures of 25 and 30°C were performed. Again, a strong decrease of the mussels’ grazing rates in relation to the flagellate growth rates with increasing temperature occurred for two mussel species (C. fluminea and Dreissena polymorpha). When performing the same experiment using a benthic microbial predator community (biofilms dominated by ciliates) instead of the benthic mussels, an increase of the grazing rates relative to the growth rates with temperature could be observed. Our data suggest that predator–prey interactions (between metazoans and microbes) that are balanced at moderate temperatures could become unbalanced at high temperatures. This could have significant effects on the structure and function of microbial communities in light of the predicted increasing frequency of summer heat waves. Priority programme of the German Research Foundation—contribution 7.     

An autoantibody against N(ε)-(carboxyethyl)lysine (CEL): possible involvement in the removal of CEL-modified proteins by macrophages

Advanced glycation end products (AGEs) are believed to play a significant role in the development of diabetic complications. In this study, we measured the levels of autoantibodies against several AGE structures in healthy human plasma and investigated the physiological role of the autoantibodies. A high titer of the autoantibody against N(ε)-(carboxyethyl)lysine (CEL) was detected in human plasma compared with other AGE structures such as CML and pentosidine. The purified human anti-CEL autoantibody reacted with CEL-modified human serum albumin (CEL-HSA), but not CML-HSA. A rabbit polyclonal anti-CEL antibody, used as a model autoantibody against CEL, accelerated the uptake of CEL-HSA by macrophages, but did not enhance the uptake of native HSA. Furthermore, when (125)I-labeled CEL-HSA was injected into the tail vein of mice, accumulation of (125)I-CEL-HSA in the liver was accelerated by co-injection of the rabbit anti-CEL antibody. These results demonstrate that the autoantibody against CEL in plasma may play a role in the macrophage uptake of CEL-modified proteins.     

Comments: Limits of phosphorus removal in wetlands (Kadlec,previous issue,pp. 165–175)

Wetlands Ecology and Management -     

Can lake restoration by fish removal improve the status of profundal macroinvertebrate assemblages?

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Control of the citric acid cycle by glyoxylate: Mechanism of the inhibition by oxalomalate and γ-hydroxy-α-oxoglutarate

1. Hydroxyoxoglutarate was obtained by three methods: decarboxylation of oxalomalic acid, and synthesis from glyoxylate and pyruvate by using either Mg²⁺ or an enzyme from rat liver as catalysts. 2. The inhibitory effects of oxalomalate and hydroxyoxoglutarate upon aconitate hydratase, isocitrate dehydrogenase (NADP) and oxoglutarate dehydrogenase were investigated. 3. Oxalomalate at low concentrations (1mm) inhibited almost completely both aconitate hydratase and isocitrate dehydrogenase. Hydroxyoxoglutarate also inhibited these enzymes, but at concentrations approximately tenfold that of oxalomalate. 4. Oxalomalate and hydroxyoxoglutarate, at the higher concentrations, inhibited oxoglutarate dehydrogenase to approximately the same extent. 5. It is suggested that the ability of glyoxylate to control reaction rates in the tricarboxylic acid cycle must in some degree be due to its condensation with oxaloacetate and pyruvate to form enzyme inhibitors.     

Adapting the dynamic LakeMab model to simulate seasonal variations of phosphorus concentration in reservoirs: a case study of Lake Bultière (France)

Limnology - Controlling phosphorus is fundamental to limit the risk of eutrophication of continental aquatic ecosystems. Integrated modelling of its concentration in the aquatic continuum requires...     

Does leaf quality mediate the stimulation of leaf breakdown by phosphorus in Neotropical streams?

1. Lowland tropical streams have a chemically diverse detrital resource base, where leaf quality could potentially alter the effect of high nutrient concentrations on leaf breakdown. This has important implications given the extent and magnitude of anthropogenic nutrient loading to the environment. 2. Here, we examine if leaf quality (as determined by concentrations of cellulose, lignin and tannins) mediates the effects of high ambient phosphorus (P) concentration on leaf breakdown in streams of lowland Costa Rica. We hypothesised that P would have a stronger effect on microbial and insect processing of high‐ than of low‐quality leaves. 3. We selected three species that represented extremes of quality as measured in leaves of eight common riparian species. Species selected were, from high‐ to low‐quality: Trema integerrima > Castilla elastica > Zygia longifolia. We incubated single‐species leaf packs in five streams that had natural differences in ambient P concentration (10–140 μg soluble reactive phosphorus (SRP) L^?1), because of variable inputs of solute‐rich groundwater and also in a stream that was experimentally enriched with P (approximately 200 μg SRP L^?1). 4. The breakdown rate of all three species varied among the six streams: T. integerrima (k‐values range: 0.0451–0.129 day^?1); C. elastica (k‐values range: 0.0064–0.021 day^?1); and Z. longifolia (k‐values range: 0.002–0.008 day^?1). Both ambient P concentration and flow velocity had significant effects on the breakdown rate of the three species. 5. Results supported our initial hypothesis that litter quality mediates the effect of high ambient P concentration on leaf processing by microbes and insects. The response of microbial respiration, fungal biomass and invertebrate density to high ambient P concentration was greater in Trema (high quality) than in Castilla or Zygia (low quality). Variation in flow velocity, however, confounded our ability to determine the magnitude of stimulation of breakdown rate by P. 6. Cellulose and lignin appeared to be the most important factors in determining the magnitude of P‐stimulation. Surprisingly, leaf secondary compounds did not have an effect. This contradicts predictions made by other researchers, regarding the key role of plant secondary compounds in affecting leaf breakdown in tropical streams.     

Reassessment of Paleotachina Townsend and Electrotachina Townsend and their removal from?the?Tachinidae (Diptera)

The monotypic genera Paleotachina Townsend, 1921 and Electrotachina Townsend, 1938 were originally described as fossils in amber but were later discovered to be inclusions in copal. Both taxa were originally assigned to the Tachinidae (Diptera) and this placement has continued to the present day. The holotypes of the two type species, P. smithii Townsend and E. smithii Townsend, were examined and the following taxonomic and nomenclatural changes are proposed: Paleotachina is transferred to the Muscidae and placed in synonymy with Aethiopomyia Malloch, 1921, syn. n.; P. smithii Townsend, type species of Paleotachina, is synonymized with Aethiopomyia gigas (Stein, 1906), syn. n.; Electrotachina is transferred to the Sarcophagidae and placed in synonymy with Dolichotachina Villeneuve, 1913, syn. n.; E. smithii Townsend, type species of Electrotachina, is recognized as a valid species of Dolichotachina comb. n. Images of the holotypes of P. smithii and E. smithii are provided and features that have helped place these copal inclusions in their new combinations are discussed.     

A bizarre sternorrhynchan wing from the Lower Jurassic of Luxembourg (Hemiptera: Sternorrhyncha: Pincombeomorpha?)

Fossil wing of Hemiptera Sternorrhyncha with peculiar venation is described from the lower Toarcian (Lower Jurassic) of Bascharage (Grand-duchy of Luxembourg). It represents new family Xulsigiidae fam. nov., comprising a new genus and species Xulsigia karetsa gen. et sp. nov. It is placed preliminarily in extinct infraorder Pincombeomorpha for the presence of three branches of median vein. Key to families of Pincombeomorpha is given and the taxonomic position and venation features of the new fossil are discussed.

Family Xulsigiidae is registered in Zoobank under the http://www.zoobank.org/urn:lsid:zoobank.org:act:3A57B428-638A-439A-AEC4-D18B5959B5CA

Genus Xulsigia is registered in Zoobank under the http://www.zoobank.org/urn:lsid:zoobank.org:act:2B255A30-5A7C-4CF8-AE77-18ED6E8E03C2     

Is halogen content the most important factor in the removal of halogenated trace organics by MBR treatment?

This study investigated the relationship between physicochemical properties (namely halogen content and hydrophobicity) of halogenated trace organics and their removal efficiencies by a laboratory scale membrane bioreactor (MBR) under stable operating conditions. The reported results demonstrated a combined effect of halogen content and hydrophobicity on the removal. Compounds with high halogen content (>0.3) were well removed (>85%) when they possessed high hydrophobicity (Log D>3.2), while those with lower Log D values were also well removed if they had low halogen content (<0.1). General indices such as the BIOWIN index (which is based on only biodegradation) or a more specific index such as the halogen content (which captures a chemical aspect) appeared insufficient to predict the removal efficiency of halogenated compounds in MBR. Experimental data confirmed that the ratio of halogen content and Log D, which incorporates two important physico-chemical properties, is comparatively more suitable.