bluuebunny/crossref_metadata_2025_split huggingface dataset:
Trace Metals in Mesozooplankton of the North Sea: Concentrations in Different Taxa and Preliminary Results on Bioaccumulation in Copepod Collectives (Calanus finmarchicus/C. helgolandicus)
Authors: Zauke Gerd‐Peter , Krause Michael , Weber Adolf 
Published: February 2007

AbstractTrace metals (Cd, Cu, Zp, Pb, Ni) were determined in different zooplankton taxa to assess their role in the biogeochemical cycle in the North Sea. Results of semi‐static bioaccumulation experiments on board ship using collectives of Calanus finmarchicus/C. helgolandicus were in agreement with a net accumulation strategy, thus meeting an inevitable precondition for their utilization as biomonitors. Cd, Cu and Zn concentrations in field samples of zooplankton displayed a pronounced variability between taxa, with Cd ranging from 0.13 mg kg‐1 (d.w.) in fish larvae to 5I mg kg‐1 in hyperiid amphipods. Almost no information is available about metal requirements of copepods. However, most of our and worldwide reported Cu concentrations in calanoid copepods (6‐22 mg kg−1) coincided with estimates of enzymatic requirements of decapod crustaceans. Cd levels in Calanus collectives increased significantly from 0.68 mg kg‐1 in the German Bight to 11 mg kg−1 at some stations around Scotland above 59° N, in line with literature data reported for benthic decapod crustaceans.
Differential Response of Benthos to Natural and Anthropogenic Disturbances in 3 Lowland Streams
Authors: Armitage P. D. , Gunn R. J. M. 
Published: February 2007

AbstractThe macroinvertebrate faunal assemblages of 8 sites on three small streams in SE England were examined annually in spring between 1987 and 1993. Considerable ‘natural’ variability was observed in the sites superimposed over a background of low‐intensity anthropogenic disturbance such as farming, quarrying, and urban influences. Landscape changes and activities in the catchment (saline drainage, removal of topsoil, pipeline crossings of streams) associated with the construction of the UK terminal for the Channel Tunnel, resulted in further temporary disturbance at some of the sites.Most changes in faunal composition were related to natural and anthropogenically induced modifications of the stream substrate. The response and recovery time of sites to disturbances was very variable and was related to the hydraulic and substrate characteristics of the stream bed, with least change and quickest recovery at sites with coarse substrates and high slope. Variations between years in the occurrence of taxa were generally more apparent with species data than with family data except where environmental change was great. Despite the observed differences in faunal composition the main elements of the fauna were fairly constant throughout the study period.Analyses of the data with biotic indices, the predictive RIVPACS system and ordination analyses have all shown clearly the annual variability of faunal parameters used to measure environmental quality. The study has shown that very basic rapid assessment techniques can provide insights into faunal responses to disturbance, especially if the work is long‐term and that before authoritative statements concerning environmental impact can be made it is essential to have knowledge of the natural variation to be expected in streams of differing characteristics.
The Structure of a Macroinvertebrate Community in a Northern German Lake Outlet (Lake Belau, Schleswig‐Holstein) with Special Emphasis on Abundance, Biomass and Secondary Production
Authors: Popperl Rainer 
Published: February 2007

AbstractThe structure of macroinvertebrate communities was studied at I I sampling sites of the outlet of Lake Belau in the lowlands of northern Germany. To describe the structures of macrobenthic animal communities three different units were examined: abundance, biomass, and secondary production.112 taxa were collected from the entire stream. The numbers of species ranged from 31 (fine sand) to 70 (submerged macrophytes). For the stream, average macroinvertebrate density was 18.400 ind. M−1. Density was highest at the macrophytes amounting to 35,630 individuals per m2, and lowest in the pure sand with only 3,900 ind. M−2. Average biomass (dry mass) was 194 g DM m−2 varying from 9.8 (peat) to 381 g DM m−2 (gravel with mollusk shells near the upstream lake). For the stream, average annual production was 129 g DM m−2 varying from 15 (peat) to 286 g DM m−2 (macrophytes).The highest values for each unit were found in stream sections with gravel and submerged macrophytes. Lower values occured in sections that contained peat and sand. Usually, a single structure of the macroinvertebrate community was dominated by less than ten taxa, which varied at each sampling site depending on the units observed.
Herbaceous Wetlands of the Yucatan Peninsula: Communities at Extreme Ends of Environmental Gradients
Authors: Rejmankova Eliška , Pope Kevin O. , Post Rebecca , Maltby Edward 
Published: February 2007

AbstractDistribution of wetland communities and growth characteristics of dominant macrophyte species were studied in the SE and NW parts of the Yucatan Peninsula. Plant, water and soil samples were collected from 40 marshes ranging from permanently flooded to seasonally drying. Marsh soils were identified as either peats, mark or clays with many intergrades. Water quality ranged from mesosaline (chloride or sulfate dominated) to fresh (carbonate dominated). Nutrient concentrations, specifically phoshorus, were low. The dominant species wereTypha domingensis(TD),Cladium jamaicense(CJ),Eleocharis cellulosa(EC),E. interstincta(EI), and algal mats composed mostly of blue green algae (BG). EC and BG dominate marshes with marly soils and high salinities. C3 grows well on peaty soils and is well adapted to extremely low phosphorus concentrations and occasional drying. TD dominates nutrient rich marshes with deep water and clayey soils. The species differ significantly in their growth, death and decomposition rates. All these rates are highest for TD, followed closely by EC, and slowest for CJ.
Phytoplankton and Nutrients in the River Strymon, Greece
Authors: Tryfon Eleni , Moustaka‐Gouni Maria , Nikolaidis Georgios 
Published: February 2007

AbstractPhytoplankton species composition, biomass, diversity, nutrients and chlorophyll a were studied at monthly intervals from December 1991 to December 1992 in a selected area of the river Strymon. SRP ranged from 53 to 182 μg−1 l−1 and DIN from 265 to 850 μg−1 I−1. Nutrient values do not indicate strong anthropogenic effects. Chlorophyll α ranged from 1.0 to 35.3 μg−1 I−1 and followed the temporal distribution of total phytoplankton biomass. Phytoplankton biomass exhibited maxima in winter – spring and summer (6.8 g m−3 in December 1991, 4.8 g m−3 in April 1992 and 9.3 g m−3 in August 1992) composed mainly of diatoms, chlorphytes, cyanophytes and dinophytes. Nanoplankton was the most important component of phytoplankton biomass (69.5%) revealing increased values in winter and early spring. Phytoplankton diversity ranged from 0.8 to 3.2. The hydrological conditions in the river Strymon seem to be appropriate for the algae to reproduce themselves in the running water and so, to develop as a true potamoplankton. However, significant populations of phytoplankton must have been carried out from the Kerkini reservoir, situated at the north of the sampling station. The phytoplankton species composition and their periodicity in the river resemble those of typical, large, lowland and nutrient – rich rivers of Europe.
Development of Submerged Macrophytes in the Treated Sewage Channel Wuhle (Berlin, Germany)
Authors: Körner S. , Kühl H. 
Published: February 2007

AbstractThe environmental conditions for submerged macrophytes in sewage channels are different to those of natural waters. Mainly 6 eutraphent species occur in two communities on the flowing stretch of the Berlin treated sewage channel Wuhle. The survival time of the above ground biomass of the annual species is relatively long due to the higher water temperatures in winter. The average biomass of the different parts of the flowing stretch is between 50 and 830 g DM/m2 in summer. With decreasing concentrations of ammonia and BOD an increase of the biomass and the colonization density could be noticed over the last few years.
A Proposed Framework for the Management of Water Quality in Arid‐Region Lakes
Authors: Parparov Arkadi , Hambright K. David 
Published: February 2007

AbstractFor arid‐region lakes, management conflicts are likely to occur between quantity and quality of water supplied: increasing quantity of water supply can lead to water quality deterioration. Such conflicts can best be resolved within an effective management program based on awareness and cooperation at all levels of water management from policy makers to experts. We propose a general framework for designing effective water resource management programs for lakes based on concrete definitions of management criteria such as water quality. The proposed system requires close interaction between policy makers, water resource managers, water suppliers and users, hydrological engineers and limnologists. The significance of mathematical modeling as a self‐organizing tool of the management program is emphasized, especially with regards to designing limnological investigations directed toward lake management. We illustrate the application of this approach to water resource management in arid‐region lakes (Lake Kinneret, Israel and Lake Sevan, Armenia), where artificial variability of lake morphometry due to water use is a forcing function affecting water quality.
Bionomy of Macrobenthic Molluscs in Evros Delta (North Aegean Sea)
Authors: Kevrekidis T. , Gouvis N. , Koukouras A. 
Published: February 2007

AbstractThe composition and distribution of the macrobenthic molluscs in Evros Delta (North Aegean Sea) were investigated by quantitative sampling. The molluscan distribution shows a zonation mainly related to the degree of “confinement”. Based on similarity in distribution among stations, 2 groups of species were distinguished. One group includes marine species (Tellina tenuis, Bittium reticulatum) found only in coastal stations and the second group is typical of estuarine species (Hydrobia acuta, Abra ovata and Cerastoderma glaucum) distributed in almost all stations. Spatial fluctuations of the 3 estuarine species reflect their preferences in the various parameters (“confinement”, salinity, grain size and organic matter of sediment). The most isolated stations support the highest values of total mollusc abundance and biomass.
Prey Selection by the Water Bug Aphelocheirus aestivalis Fabr. (Heteroptera: Aphelocheiridae)
Authors: Lemb Markus , Maier Gerhard 
Published: February 2007

AbstractFeeding experiments were conducted in situ in flow through boxes to determine the vulnerability of different prey types (the mayfly larvae Baetis, Ephemerella and Ecdyonurus spp., the caddisfly larva Hydropsyche spp. and the crustacean Gammarus spp.) to the predaceous water bug Aphelocheirus aestivalis and to estimate the predation impact of Aphelocheirus on prey populations. Experiments with equal densities of mixed prey and experiments where each prey was tested individually revealed that Baetis and Ephemerella were most vulnerable to Aphelocheirus predation: Hydropsyche, Ecdyonurus and Gammarus were little/not preyed upon. The present results suggest that vulnerability of prey depends mainly upon prey mobility and microhabitat overlap between predator and prey and that feeding behaviour of Aphelocheirus resembles more that of megalopterans than of stoneflies. Experiments with different prey densities (120–720 prey m−2) showed that the predation rate of Aphelocheirus increased with increasing prey density. Experiments with different substrates documented that mortality rates of prey decreased with increasing substrate complexity. When substrate conditions were complex mortality rates in the control and in the experimental boxes were the same which suggest little importance of Aphelocheirus predation on mayflies in the study site.
Diurnal vertical migration study during a winter bloom of Cryptophyceae in a floodplain pool
Authors: Pithart David 
Published: February 2007

AbstractThe diurnal vertical migration (DVM) of the phytoplankton community was studied in a small (270m2), shallow (1.8m), and frozen floodplain pool. Steep vertical gradients were detected in O2, NH4+‐N, NO3−‐N and PO43‐‐P profiles. The phytoplankton of the pool is characterized by year round dominance of Cryptophyceae: Cryptomonas curvata and Cryptomonas marssonii created more than 90% of total phytoplankton biomass during the time of study. DVM was studied by analysing vertical profiles six times during a 24 hour cycle; samples were taken at 20 cm intervals along the profiles. Koliella planktonica, the only non‐motile alga, showed a stable uniform distribution. Dinobryon divergens and Chrysococcus rufescens created a stable distinct concentration maximum at 40cm. Unlike these three species, both Cryptomonas spp. actively changed their position during the 24 hour cycle with distinctive evening downward and morning upward migration. The absence of filtering zooplankton excluded its influence on the patterns of phytoplankton DVM. The results showed the key role of PhAR (Photosynthetic active irradiance) in day ‐ positioning of Cryptomonas. Night‐time uptake of phosphate and/or ammonium at the bottom is probable, although direct evidence is lacking.
Thiamine dynamics in aquatic ecosystems and its biological implications
Authors: Niimi Arthur J. , Jackson Chung‐Ja C. , Fitzsimons John D. 
Published: February 2007

AbstractThiamine concentrations were monitored in various organisms ranging from plankton to fish in the Lake Ontario ecosystem. The low concentrations found in most samples indicated thiamine levels were not strongly influenced by the trophic status of an organism. A similar conclusion was indicated from data reported by other studies in freshwater and marine ecosystems. Thiamine is produced by microbes and microalgae, and is acquired by higher trophic level organisms through the diet. The issue of thiamine deficiency in wild fish was also examined. It was concluded that increased dietary consumption of prey containing thiaminase was an important factor that can reduce thiamine levels in higher trophic level species.
Effects of a seasonal salinity change on periphyton biomass in a shallow tropical lagoon
Authors: Arfi Robert , Bouvy Marc , Luquet Pierre 
Published: February 2007

AbstractIn the Ebrié Lagoon (Cǒte d'Ivoire), growth of periphyton on bamboo stuck in the sediment is at the basis of the acadja, a low‐cost system developed in order to enhance aquaculture of omnivorous fish like the tilapia Sarotherodon melanotheron. A survey based on hydrological, bacterial and algal data (including phytoplankton and periphyton) was conducted from November 1992 to June 1993 in an experimental structure. Climatic and hydrological seasonality was marked during the study. Succeeding to a rainy season, the oligohaline situation starting in November was characterized by low bacterial and chlorophyll biomass attached to the bamboo (respectively 1 and 18 mg m−2). The mesohaline situation observed from January featured a sharp increase in periphyton biomass, with a maximum in April (16 and 177 mg m−2 for bacterial and algal biomass, respectively). The flood of the Agnéby river, induced in June by the local rains, originated again oligohaline conditions. The biomass decrease observed in May and June resulted from a shift towards low salinity (from 9.8 to 1.8 psu), a decrease in light availability (combined effects of a decreasing solar radiation during the rainy season and an increase of water turbidity due to the flood) and a lower phytoplankton biomass (therefore limiting the secondary epiphytism potentialities). In this shallow tropical environment characterized by high nutrient concentrations (due to local hydrology and organic nature of the substrate), the combination of seasonal variations of climatic (light availability), hydrological (salinity) and biological (abundance or lack of epiphytic algae) seems to control the periphyton biomass growing on bamboo. Therefore, marked seasonality in the production of resource available for the target fish would limit the interest of the acadja as an aquaculture system in brackish ecosystems.
Behavioural responses of different blackfly species to short‐term oxygen depletion
Authors: Kiel E. , Frutiger A. 
Published: February 2007

AbstractBehavioural changes of four larval blackflies (Simulium noelleri, S. ornatum (complex), S. trifasciatum [syn. S. spinosum] and S. variegatum) to experimental reduction of dissolved oxygen were investigated with videotechniques. Since these species are characterised by different habitat preferences, they were expected to respond differently to oxygen depletion. During experiments lasting 120–140 min., dissolved oxygen (DO) was reduced to 0.3–0.6 mg/1 within the first hour and kept constant for another hour. Water velocity in the laboratory channel was 135 cm/s. Transparent plastic walls allowed video‐recording of larval behavioural responses to oxygen depletion. Blackflies did not engage in undulative or other ventilation movements, and they did not increase locomotory activity, nor did they actively drift. Oxygen depletion mainly altered filter‐feeding activity and non‐locomotory movements (bending and sweeping). With decreasing DO concentrations larvae of all four species reduced and finally ceased filter‐feeding. Non‐locomotory movements first temporarily increased and then also ceased, except in S. variegatum, where these movements were immediately suspended. DO‐threshold values for cessation of filter‐feeding and movements, as well as mortality indicated S. variegatum to be the most sensitive species in respect to oxygen depletion, while S. noelleri seems to be the most tolerant among the four blackfly species tested here.
Some physical and biological factors affecting a spring‐summer phytoplankton dynamics in a shallow, temperate lake of South Andes (Argentina)
Authors: Queimaliños Claudia P. 
Published: February 2007

AbstractThe phytoplankton dynamics of Laguna Ezquerra (Río Negro, Argentina) was analysed on the basis of high frequency sampling, each 3–4 days during a spring‐summer period, in relation to physical factors and to the zooplankton community structure. The phytoplankton biomass presented a marked seasonality, accompanied by similar seasonal patterns in temperature and zooplankton dynamics. Community variations were reflected in the diversity, dominance and equitability values. The greatest change was associated during a short flooding period produced in late spring. The wind exposure was irregular during the whole study period, and was assumed to be a factor of stress for the phytoplankton growth. During spring and early summer, the phytoplankton community was dominated by nanoplanktonic forms likeRhodomonas lacustris, and the large sizedAsterionella formosapresented an exponential increment at late summer. ThisAsterionellagrowth permitted to affirm that the community evolved towards plagioclimatic stages, attending the highly disturbed conditions of the shallow and wind exposed environment.
Nitrogen and carbohydrate pools of two rhizome types of Phragmites australis (Cav.) Trin. ex Steudel
Authors: Woitke Peter , Kiehl Annette , Kühl Harald , Kohl Johannes‐Günter 
Published: February 2007

AbstractCarbohydrate and total nitrogen contents as well as free amino acid (FAA) concentrations were determined in distinct types of rhizomes of two genetically homogeneous stands of reed (Phragmites australis (Cav.) Trin. ex Steudel) differing in morphology, productivity and nutrient supply in order to evaluate the storage capacity of vertical rhizomes and expansion rhizomes. The expansion rhizomes possess significantly higher amounts of FAA and of total nitrogen but similar carbohydrate concentrations in comparison to the vertical rhizomes. However, no significant differences were found for total nitrogen, FAA and total carbohydrates between both investigated stands indicating a comparable storage capacity of rhizomes independent of nutrient availability. Only the composition of the FAA pool varied in the alanine/asparagine ratio probably influenced by the oxygen supply of the rhizome/root system.
Determinations of clusters, functional groups and variants among lake and catchment area variables
Authors: Håkanson Lars 
Published: February 2007

AbstractA cluster is a family of variables showing high internal correlation. For example, conductivity, hardness and Ca‐concentration which generally appear with correlation coefficients (r) > 0.8 for mean annual values among lakes. They indicate the amount of salts and ions in the water. A functional group is a family of variables which describe a particular process or mechanism in an ecosystem, like mean depth relative depth and volume development. All of these could be related to resuspension. Such variables would also constitute a cluster if they are well correlated across many lakes belonging to a given lake type. These three parameters express different form elements of lakes, they belong to the same functional group in contexts of lake resuspension, but they do not constitute a cluster since they are only rather poorly correlated (the r‐values between these parameters is generally <0.5). A variant is a value for a given variable from a defined period of time, like a mean annual or monthly value. One can then ask: Which variant from which time period should be used in relation to a given y‐variable one wants to predict to obtain a model with a high predictive power? Variables belonging to the same cluster can often replace one another in models without significantly altering predictive accuracy. The aim of this work is to determine clusters among standard groups of water variables, lake morphometric parameters and catchment parameters. The analysis uses a comprehensive data‐set from 95 Swedish lakes. There are about 83,000 lakes in Sweden, about 81,000 belong to this lake type of glacial lakes, which is the most common lake type on Earth. Selected results: Among the catchment parameters, one may note that the proportion of lakes does not co‐vary closely with any other parameter, but that the percentage of morainic soils is negatively associated with the area covered by bedrock and flat rocks. Two clusters of morphometric parameters can be identified: Size parameters (e.g., volume and area) and form parameters (e.g., relative depth and dynamic ratio). Among the water variables, colour, iron concentration and Secchi depth are strongly correlated. The concentration of total phosphorus, which is functionally associated with the production of algae, is also related to Secchi depth.