bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tracing lake trophic history with a chironomid–total phosphorus inference model
Authors: Brooks Stephen J. , Bennion Helen , Birks H. John B. 
Published: March 2003

1. In the absence of historical water chemistry data, predictive biological indicator groups preserved in lake sediments can be employed to reconstruct the history of lake eutrophication. Diatoms are well established in this role, but to augment diatom‐based inferences of nutrient status we investigate the potential use of chironomid midges (Insecta: Chironomidae).2. Canonical correspondence analysis (CCA) of modern chironomid assemblages in surface sediments from 44 lakes in the English Midlands and Wales, U.K., shows that five environmental variables (total phosphorus (TP), bottom dissolved oxygen, maximum lake depth, Secchi depth and surface water temperature) make a statistically significant (P < 0.05) contribution to explaining the variance in the chironomid data, of which TP makes the largest contribution (29%).3. The relationship is used to develop a series of weighted averaging (WA) and partial least squares (PLS), (WA‐PLS) models to infer log10TP. The models are evaluated by leave‐one‐out (jack‐knifing) cross‐validation. The simplest minimal adequate model is provided by WA with unweighted inverse deshrinking of root mean square error of prediction (RMSEPjack=0.34 and r2jack=0.60).4. Using this model, the trophic history of Betton Pool, Shropshire, U.K., is reconstructed from the mid‐19th century to the present day and the results from the chironomid‐TP model are compared with inferences from a diatom‐TP model (Bennion, Juggins & Anderson, 1996). Both reconstructions suggest that there was a gradual rise in TP since 1850 AD until about 1974, followed by a more pronounced and rapid increase that has continued until the present. Inferred TP values from the WA chironomid inference model agree with diatom‐inferred values.5. The study demonstrates that fossil chironomid assemblages can be used to investigate quantitatively the trophic history of lakes.
Sulphate reduction and sulphur cycling in lake sediments: a review
Authors: Holmer Marianne , Storkholm Peter 
Published: March 2003

1. The concentration of sulphate is low in lakes and sulphur cycling has often been neglected in studies of organic matter diagenesis in lake sediments. The cycling of sulphur is, however, both spatially and temporally dynamic and strongly influences many biogeochemical reactions in sediments, such as the binding of phosphorus. This review examines the control of sulphate reduction and sulphur cycling in sediments of lakes with different trophic status.2. The factors that control the rate of sulphate reduction have not been identified with certainty in the various environments because many factors are involved, e.g. oxygen and sulphate concentrations, temperature and organic matter availability.3. Sulphate reduction is less significant under oligotrophic conditions, where mineralization is dominated by oxic decomposition. The supply of organic matter may not be sufficient to support sulphate reduction in the anoxic parts of sediments and, also, sulphate availability may control the rate as the concentration is generally low in oligotrophic lakes.4. There is a potential for significant sulphate reduction in eutrophic lakes, as both the availability of organic matter and sulphate concentration are often higher than in oligotrophic lakes. Sulphate is rapidly depleted with sediment depth, however, and methanogenesis is generally the most important process in overall carbon mineralization. Sulphate reduction is generally low in acidic lakes because of low sulphate availability and reduced microbial activity.5. It is still unclear which of the forms of sulphur deposits are the most important and under which conditions burial occurs. Sulphur deposition is controlled by the rate of sulphate reduction and reoxidation. Reoxidation of sulphides occurs rapidly through several pathways, both under oxic and anoxic conditions. Only a few studies have been able to examine the importance of reoxidation, but it is hypothesized that most of the reoxidation takes place under anoxic conditions and that disproportionation is often involved. The presence of sulphide oxidizing bacteria, benthic fauna and rooted macrophytes may substantially enhance oxic reoxidation. Deposition of sulphur is generally higher in eutrophic than in oligotrophic lakes because of a number of factors: a higher rate of sulphate reduction, enhanced sedimentation of organic sulphur and less reoxidation as a result of reduced penetration of oxygen into the sediments, a lack of faunal activity and rooted macrophytes.
Effects of nutrient enrichment and leaf quality on the breakdown of leaves in a hardwater stream
Authors: Royer Todd V. , Minshall G. Wayne 
Published: March 2003

1. The breakdown of leaf litter in streams is influenced strongly by leaf quality and the concentration of dissolved nutrients, primarily inorganic nitrogen (N) and phosphorus (P) in the water. We examined the effect of nutrient enrichment on the breakdown of three species of leaves in a hardwater, nutrient‐rich stream. The rate of microbial respiration was also measured on the decomposing leaves.2. The breakdown rates of dogwood (Cornus stolonifera), aspen (Populus tremuloides) and birch (Betula occidentalis), k‐values of 0.0461, 0.0307 and 0.0186 day–1, respectively, were unaffected by nutrient enrichment and generally faster than reported previously. Microbial respiration on the leaves was greater than reported previously for leaves of congeneric species. It appears that leaf breakdown in the study stream was not nutrient limited.3. Nitrogen‐based measures of leaf quality, such as percentage N and carbon (C)/nitrogen ratio, did not correspond to measured breakdown rates among the three leaf types. The best predictors of relative breakdown rates were percentage lignin and the percentage of the total carbon that occurred as lignin. We suggest that, when leaf breakdown is not nutrient limited, measures of carbon quality (i.e. lignin‐based measures) are a better assessment of overall leaf quality than are N‐based measures.4. Previous studies have indicated that the enzymes produced by aquatic hyphomycetes (microfungi) operate most efficiently at a basic pH and in the presence of calcium ions. The hardwater conditions (pH=8.6, total hardness > 300 mg CaCO3 L–1) and abundance of dissolved NO3 and soluble reactive phosphorous (SRP) (approximately 50 μg L–1, each) in the study stream appear to have provided conditions that resulted in a high respiration rate and rapid breakdown of leaf litter.
A proximate cue for oviposition site choice in the bitterling (Rhodeus sericeus)
Authors: Smith Carl , Rippon Karina , Douglas Alex , Jurajda Pavel 
Published: March 2003

1. We investigated two possible proximate cues used for oviposition site choice by females of the bitterling (Rhodeus sericeus), a freshwater fish that spawns on the gills of live unionid mussels. The two cues were the flow velocity and/or oxygen content of water emerging from the exhalant siphon of a mussel.2. Field observations showed that female bitterling always inspected the exhalant siphons of mussels before they spawned in them. Siphon inspection was not always a prelude to spawning and it may serve as a means of assessing mussel quality. Female skimming behaviour, swimming over a mussel without spawning, may also be used to assess mussel quality, although the mechanism for this is unclear.3. Measurements of the flow velocity of water emerging from the exhalant siphons of four mussel species (Anodonta anatina, A. cygnea, Unio pictorumandU. tumidus) showed a significant difference among species, withU. tumidushaving the highest mean flow velocity andU. pictorumthe lowest.4. Measurements of the change in oxygen concentration of water entering a mussel inhalant siphon and leaving its exhalant siphon in field and laboratory studies showed a significant difference among the four mussel species, withA. cygneaexhibiting a significantly higher change in oxygen concentration than the other species.5. The presence of bitterling embryos in the gills of a mussel significantly increased its oxygen consumption whereas larval glochidia had no significant effect. We discuss oxygen availability as a possible proximate cue for oviposition site choice in bitterling.
Comparison of bacterial production in sediments, epiphyton and the pelagic zone of a lowland river
Authors: Fischer Helmut , Pusch Martin 
Published: March 2003

1. The microbial metabolism of organic matter in rivers has received little study compared with that of small streams. Therefore, we investigated the rate and location of bacterial production in a sixth‐order lowland river (Spree, Germany). To estimate the contribution of various habitats (sediments, epiphyton, and the pelagic zone) to total bacterial production, we quantified the contribution of these habitats to areal production by bacteria.2. Large areas of the river bottom were characterized by loose and shifting sands of relatively homogenous particle size distribution. Aquatic macrophytes grew on 40% of the river bottom. Leaf areas of 2.8 m2 m−2 river bottom were found in a 6.6 km river stretch.3. The epiphyton supported a bacterial production of 5–58 ng C cm−2 h−1. Bacterial production in the pelagic zone was 0.9–3.9 μg C L−1 h−1, and abundance was 4.0–7.8 × 109 cells L−1. Bacterial production in the uppermost 2 cm of sediments ranged from 1 to 8 μg C cm−3 h−1, and abundance from 0.84 to 6.7 × 109 cells cm−3. Bacteria were larger and more active in sediments than in the pelagic zone.4. In spite of relatively low macrophyte abundance, areal production by bacteria in the pelagic zone was only slightly higher than in the epiphyton. Bacterial biomass in the uppermost 2 cm of sediments exceeded pelagic biomass by factors of 6–22, and sedimentary bacterial production was 17–35 times higher than in the overlying water column.5. On a square meter basis, total bacterial production in the Spree was clearly higher than primary productivity. Thus, the lowland river Spree is a heterotrophic system with benthic processes dominating. Therefore, sedimentary and epiphytic bacterial productivity form important components of ecosystem carbon metabolism in rivers and shallow lakes.6. The sediments are focal sites of microbial degradation of organic carbon in a sand‐bottomed lowland river. The presence of a lowland river section within a river continuum probably greatly changes the geochemical fluxes within the river network. This implies that current concepts of longitudinal biogeochemical relationships within river systems have to be revised.
Lime treatment and its effects on the chemistry and biota of hardwater eutrophic lakes
Authors: Prepas Ellie E. , Pinel‐Alloul Bernadette , Chambers Patricia A. , Murphy Tom P. , Reedyk Sharon , Sandland Greg , Serediak Mark 
Published: March 2003

1. The main focus of this study was to investigate the effects of single and multiple moderate doses of lime (slaked lime, Ca(OH)2, and/or calcite, CaCO3) on eutrophic hardwater lakes. This information would contribute to strategies to manage phytoplankton and macrophyte biomass in eutrophic lakes.2. Water chemistry and biota were monitored for up to 7 years after initial lime treatment and results were compared with reference systems.3. Complementary studies investigated the effect of lime on macrophytes in ponds, irrigation canals and microcosm experiments.4. When water pH was kept within its natural range (≤ 10), single and multiple lime applications to lakes and ponds controlled macrophyte biomass, without negatively affecting invertebrate communities.5. Single lime treatments at moderate dosages of lakes and ponds resulted in variable and mostly temporary changes in chlorophyll a (chl a) and phosphorus (P) concentration. Although sediment P release was reduced in single‐dose lakes during the first winter following treatment, reductions appeared temporary.6. Multiple treatments of lakes and ponds were effective at reducing both chl a and P concentrations over longer periods. Mean winter P release rate was also reduced after initial treatment.7. In laboratory studies, sediment cores were incubated with eight different treatments to assess P release. Redox‐sensitive treatments were no more effective at lowering total P concentration in overlying water than some redox‐insensitive treatments. Lime reduced total P concentrations, but was not as effective as treatments with alum.8. The use of lime in managing macrophyte and phytoplankton biomass in shallow, hardwater lakes and ponds may be preferable over other treatments, because lime is economical and non‐toxic as long as pH is kept within a natural range.
Ecology of glacier‐fed rivers: current status and concepts
Authors: Brittain John E. , Milner Alexander M. 
Published: March 2003

1. This paper is an introduction to a special issue of Freshwater Biology containing papers dealing with various aspects of the ecology of glacier‐fed rivers.2. Using similar field protocols, a wide range of glacier‐fed systems were studied across Europe from the French Pyrenees to Svalbard within the framework of the European Commission project, Arctic and Alpine Stream Ecosystem Research (AASER). Recent investigations from other parts of Europe together with New Zealand and Greenland are also reported. This work has advanced our knowledge of the functioning of these types of rivers and has led to the modification and quantification of the conceptual model of Milner & Petts (1994).3. Glacier‐fed rivers, by virtue of the dominance of physical variables in shaping macroinvertebrate communities, are not only good indicators of climate change, but also may be suitable testing grounds for examining ecological concepts.
Longitudinal distribution of macroinvertebrate assemblages in a glacially influenced stream system in the Italian Alps
Authors: Maiolini Bruno , Lencioni Valeria 
Published: March 2003

1. The longitudinal distribution of macroinvertebrates was investigated in June, August and September 1996 and 1997 in the Conca glacial stream and its tributary (Italian Alps; 46°N, 10°E). The principal aim was to test the Milner & Petts (1994) model that predicts the succession of faunal groups downstream of the glacial snout in relation to water temperature and channel stability. The effect of a non‐glacial tributary on the taxonomic richness and density patterns occurring in the glacial stream was also considered.2. Channel stability showed an atypical longitudinal trend in the Conca glacial stream, being high in the upper part with Pfankuch Index values between 30 and 33. Water temperature exceeded 6 °C at all stations, with average values below 2 °C occurring only within 700 m from the glacial snout.3. Taxonomic richness and diversity increased downstream. Taxonomic richness in the glacial stream (at about 1.5 km from the glacier) was comparable with the tributary and the reach after the confluence. Abundance also increased downstream in the glacial stream, but not as greatly as the number of taxa.4. At higher taxonomic levels, the community structure in the tributary stations appeared to be similar to the two stations in the glacial stream just upstream of the confluence. The effect of the tributary was evident mainly at the genus or species level of the Chironomidae community. Some taxa found in the non‐glacial stream (e.g. Cricotopus fuscus, Eukiefferiella coerulescens, Metriocnemus sp., Paratrichocladius rufiventris, P. skirwitensis, Rheocricotopus effusus and Smittia sp.) were found also in the Conca stream but only after the confluence.5. The upper glacial reach (within 700 m from the glacier snout) was dominated by the chironomid Diamesa spp. Less than 400 m from the glacier other Diamesinae (Pseudokiefferiella parva) and a few Orthocladiinae, especially Orthocladius (Euorthocladius) rivicola gr., colonized the stream. Some Diamesinae maintained relatively dense populations at mean water temperature around 5 °C, while some Orthocladiinae colonized reaches with mean water temperature <3 °C.6. Contrary to the Milner & Petts (1994) model, Dipteran families such as Empididae and Limoniidae were more abundant in the upper stations than Simuliidae; non‐insects such as Nematoda and Oligochaeta were also numerous at some sites. Leuctridae, Taeniopterygidae and Nemouridae were the first Plecoptera to appear upstream, while Chloroperlidae were restricted to the lower reaches. Among Ephemeroptera, Heptageniidae were more abundant than Baetidae in the glacial sites.7. In this glacial system channel stability and maximum temperature did not show the expected longitudinal trend and thus a typical kryal community was confined within 700 m from the glacier snout where summer mean water temperature was below 4 °C.
Longitudinal and seasonal distribution patterns of the benthic fauna of an alpine glacial stream (Val Roseg, Swiss Alps)
Authors: Burgherr Peter , Ward J. V. 
Published: March 2003

1. Seasonal changes in longitudinal patterns of environmental conditions and macroinvertebrate community distributions were examined in an alpine glacial stream (Roseg River, Switzerland).2. Physico‐chemical parameters reflected seasonal changes in glacial influence via shifts in water sources and flowpaths (glacial meltwater versus ground water), and were best described by turbidity, particulate phosphorus and specific conductance. High nitrogen concentrations indicated snowmelt was the main water source in June.3. Macroinvertebrate densities and taxon richness were highest during spring (4526 m–2 and 16 taxa, all sites combined) and late autumn/early winter (8676–13 398 m–2 with 16–18 taxa), indicating these periods may be more favourable for these animals than summer when glacial melting is maximal. Diamesa spp. (Chironomidae) dominated the fauna at the upper three sites (>95% of zoobenthos) and were abundant at all locations. Other common taxa at lower sites (1.2–10.6 km downstream of the glacier terminus) included other chironomids (Orthocladiinae, Tanytarsini), the mayflies Baetis alpinus and Rhithrogena spp., the stoneflies Leuctra spp. and Protonemura spp., blackflies (Simulium spp., Prosimulium spp.), and Oligochaeta.4. Co‐inertia analysis revealed a strong relationship between environmental conditions and benthic macroinvertebrate assemblages. Furthermore, it elucidated temporal variability in longitudinal response patterns, as well as a similarity in temporal patterns among individual sites.5. Our results suggest that zoobenthic gradients are not solely related to temperature and channel stability. Seasonal shifts in sources and pathways of water (i.e. extent of glacial influence), and periods of favourable environmental conditions (in spring and late autumn/early winter) also strongly influenced zoobenthic distributions.
Macrobenthic invertebrate richness and composition along a latitudinal gradient of European glacier‐fed streams
Authors: Castella Emmanuel , Adalsteinsson Hákon , Brittain John E. , Gislason Gisli M. , Lehmann Anthony , Lencioni Valeria , Lods‐Crozet Brigitte , Maiolini Bruno , Milner Alexander M. , Olafsson Jon S. , Saltveit Svein J. , Snook Deborah L. 
Published: March 2003

1. The influence of 11 environmental variables on benthic macroinvertebrate communities was examined in seven glacier‐fed European streams ranging from Svalbard in the north to the Pyrenees in the south. Between 4 and 11 near‐pristine reaches were studied on each stream in 1996–97.2. Taxonomic richness, measured at the family or subfamily (for Chironomidae) levels for insects and higher levels for non‐insects, increased with latitude from Svalbard (3 taxa) to the Pyrenees (29 taxa).3. A Generalized Additive Model (GAM) incorporating channel stability [Pfankuch Index (PFAN)], tractive force, Froude number (FROU), water conductivity (COND), suspended solids (SUSP) concentration, and maximum temperature explained 79% of the total deviance of the taxonomic richness per reach. Water temperature and the PFAN of stability made the highest contribution to this deviance. In the model, richness response to temperature was positive linear, whereas the response to the PFAN was bell‐shaped with an optimum at an intermediate level of stability.4. Generalized Additive Models calculated for the 16 most frequent taxa explained between 25 (Tipulidae) and 79% (Heptageniidae) of the deviance. In 10 models, more than 50% of the deviance was explained and 11 models had cross‐validation correlation ratios above 0.5. Maximum temperature, the PFAN, SUSP and tractive force (TRAC) were the most frequently incorporated explanatory variables. Season and substrate characteristics were very rarely incorporated.5. Our results highlight the strong deterministic nature of zoobenthic communities in glacier‐fed streams and the prominent role of water temperature and substrate stability in determining longitudinal patterns of macroinvertebrate community structure. The GAMs are proposed as a tool for predicting changes of zoobenthic communities in glacier‐fed streams under climate or hydrological change scenarios.
Characterizing nitrogen dynamics, retention and transport in a tropical rainforest stream using an in situ15N addition
Authors: Merriam Jeffrey L. , McDowell William H. , Tank Jennifer L. , Wollheim Wil M. , Crenshaw Chelsea L. , Johnson Sherri L. 
Published: March 2003

1. This study was part of the Lotic Intersite Nitrogen eXperiment (LINX); a series of identical 15NH4 tracer additions to streams throughout North America. 15NH4Cl was added at tracer levels to a Puerto Rican stream for 42 days. Throughout the addition, and for several weeks afterwards, samples were collected to determine the uptake, retention and transformation pathways of nitrogen in the stream.2. Ammonium uptake was very rapid. Nitrification was immediate, and was a very significant transformation pathway, accounting for over 50% of total NH4 uptake. The large fraction of NH4 uptake accounted for by nitrification (a process that provides energy to the microbes involved) suggests that energy limitation of net primary production, rather than N limitation, drives N dynamics in this stream.3. There was a slightly increased 15N label in dissolved organic nitrogen (DON) the day after the 15NH4 addition was stopped. This DO15N was < 0.02% of DON concentration in the stream water at the time, suggesting that nearly all of the DON found in‐stream is allochthonous, or that in‐stream DON production is very slow.4. Leptophlebiidae and Atya appear to be selectively feeding or selectively assimilating a very highly labelled fraction of the epilithon, as the label found in the consumers became much higher than the label found in the food source.5. A large spate (>20‐fold increase in discharge) surprisingly removed only 37% of in‐stream fine benthic organic matter (FBOM), leaves and epilithon. The fraction that was washed out travelled downstream a long distance (>220 m) or was washed onto the stream banks.6. While uptake of 15NH4 was very rapid, retention was low. Quebrada Bisley retained only 17.9% of the added 15N after 42 days of 15N addition. Most of this was in FBOM and epilithon. Turnover rates for these pools were about 3 weeks. The short turnover times of the primary retention pools suggest that long‐term retention (>1 month) is minimal, and is probably the result of N incorporation into shrimp biomass, which accounted for < 1% of the added 15N.