bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assessing the health of sediment ecosystems: use of chemical measurements
Authors: Maher W. , Batley G. E. , Lawrence I. 
Published: March 2003

Summary1. This paper outlines the use of chemical measurements as surrogate indicators of the health of sediment ecosystems.2. For chemical measurements to be used for this purpose, links must be able to be made between adverse biological effects and the chemical composition of sediments.3. Benchmark sediment quality guidelines allow decisions to be made about whether or not a sediment ecosystem is likely to be impacted. These guidelines are established using an effects database and a weight‐of‐evidence approach that gives ranges of chemical concentrations associated with known adverse biological effects.4. If guidelines are exceeded the measured values are compared to concentrations of that contaminant in a comparable background or reference sediment. Exceedance of these concentrations leads to site‐specific estimates of contaminant bioavailability. If a potential problem is indicated, laboratory sediment bioassays are used to assess the likelihood that the sediment will harm biota.5. Trace metals are used as an example of a sediment contaminant.
Development and testing of an Index of Stream Condition for waterway management in Australia
Authors: Ladson Anthony R. , White Lindsay J. , Doolan Jane A. , Finlayson Brian L. , Hart Barry T. , Lake P. Sam , Tilleard John W. 
Published: March 2003

Summary1. An Index of Stream Condition (ISC) has been developed to assist broad scale management of waterways by providing an integrated measure of their environmental condition.2. The ISC provides scores for five components of stream condition: (i) hydrology (based on change in volume and seasonality of flow from natural conditions); (ii) physical form (based on bank stability, bed erosion or aggradation, influence of artificial barriers, and abundance and origin of coarse woody debris); (iii) streamside zone (based on types of plants; spatial extent, width, and intactness of riparian vegetation; regeneration of overstorey species, and condition of wetlands and billabongs); (iv) water quality (based on an assessment of phosphorus, turbidity, electrical conductivity and pH); and (v) aquatic life (based on number of families of macroinvertebrates).3. The ISC is intended for use by managers at state and regional levels and can be used to report on stream condition, assist with priority setting, judge the long‐term effectiveness of rehabilitation programs and assist with adaptive management. The best available scientific information was used by a multidisciplinary group of scientists and managers to create a stream assessment procedure that can be used routinely by people with limited scientific training.4. ISC development included trials in four catchments in Victoria, Australia. Over 80 stream reaches were assessed and the results were used to refine the ISC to improve the ease of measurement and ensure that outcomes met the expectations of users. The ISC is now available to be used more widely for reporting on stream condition.
Climate sensitivity of Oak Mere: a low altitude acid lake
Authors: Carvalho Laurence , Moss Brian 
Published: March 2003

1. Hydrologically open lakes in temperate regions are not considered as sensitive to climate change as closed‐basin lakes in semiarid regions.2. Oak Mere is an acid lake in lowland UK. It has no surface inflow or outflow but is connected to the regional groundwater. It is a high landscape, hydrologically open lake.3. This paper describes how Oak Mere responded to drought with rapid and substantial changes in acidity and nutrients. Decreases in pH and catchment‐derived nutrients appear to be a response to the relative amount of catchment‐derived minerals compared with those received in direct precipitation.4. The extreme sensitivity of the site appears to be due to negligible groundwater inputs, low buffering capacity and a short retention time.5. The paper demonstrates that high landscape sites may represent the most sensitive hydrologically open lakes to climate change. This not only has consequences for acidification and eutrophication studies. These sites may also be considered valuable in that they potentially offer an important new archive for palaeoclimate studies, with a sensitivity previously considered unavailable in low altitude temperate regions.
Physiological responses to variable environments: storage and respiration in starving rotifers
Authors: Kirk Kevin L. , Ellis John , Taylor Jennifer 
Published: March 2003

1. Zooplankton exist in environments where food availability varies greatly over time, and success depends in part on the ability to store resources when food is abundant and to conserve them when food is scarce. This paper reports on interspecific differences in the size of stored reserves, and in respiration rate during food deprivation, of four species of planktonic rotifers.2. The size of reserves varied from 42 to 71% of initial (well‐fed) body mass. Interspecific differences in reserve size explained some of the previously observed differences in starvation time.3. The initial response of respiration rate to food deprivation was quite variable between species. Brachionus calyciflorus was the only species to conserve energy by decreasing respiration rate in response to food deprivation. In contrast, the respiration rate of starved Asplanchna priodonta increased, while that of A. silvestrii and Synchaeta pectinata did not change, during food deprivation.4. Theory predicts that temporal variation in resource level may facilitate the coexistence of competing species. This theory depends upon trade‐offs between traits that confer competitive success in different environments. Although rotifers show a trade‐off between competitive ability and maximum population growth rate, we found no evidence for trade‐offs between either of those two traits and the size of reserves.
Importance of landscape position and legacy: the evolution of the lakes in Taylor Valley, Antarctica
Authors: Lyons Wberry , Fountain& ReW. ,   dagger, & Peter Doran ,   Dagger, Priscu& JohN. C. ,   sect, Neumann Klaus , Welch Kathleen A. 
Published: March 2003

1. The major factor influencing the chemical composition and evolution of the major lakes in Taylor Valley, Antarctica, is their location within the landscape. Present‐day microclimatic variation and its manifestation over the past 6000 years have led to the differences observed in these lakes today.2. Geographical and topographical variables within the Taylor Valley magnify subtle changes in the hydrological balances of these lakes. Even short‐term variation of the surface temperatures and albedo greatly impact the run‐off into the lakes, leading to positive or negative water balances.3. The legacy of past climatic changes has had a profound effect on the ecology of the lakes today.
Factors influencing the temporal coherence of five lakes in the English Lake District
Authors: George D. G. , Talling J. F. , Rigg E. 
Published: March 2003

1. The lakes in the Windermere catchment are all deep, glacial lakes but they differ in size, shape and general productivity. Here, we examine the extent to which year‐to‐year variations in the physical, chemical and biological characteristics of these lakes varied synchronously over a 30–40‐year period.2. Coherence was estimated by correlating time‐series of the spring, summer, autumn and winter characteristics of five lakes: Esthwaite Water, Blelham Tarn, Grasmere and the North and South Basins of Windermere. Three physical, four chemical and two biological time‐series were analysed and related to year‐to‐year variations in a number of key driving variables.3. The highest levels of coherence were recorded for the physical and chemical variables where the average coherence was 0.81. The average coherence for the biological variables was 0.11 and there were a number of significant negative relationships. The average coherence between all possible lake pairs was 0.59 and average values ranged from 0.50 to 0.74. A graphical analysis of these results demonstrated that the coherence between individual lake pairs was influenced by the relative size of the basins as well as their trophic status.4. A series of examples is presented to demonstrate how a small number of driving variables influenced the observed levels of coherence. These range from a simple example where the winter temperature of the lakes was correlated with the climatic index known as the North Atlantic Oscillation, to a more complex example where the summer abundance of zooplankton was correlated with wind‐mixing.5. The implications of these findings are discussed and a conceptual model developed to illustrate the principal factors influencing temporal coherence in lake systems. The model suggests that our ability to detect temporal coherence depends on the relative magnitude of three factors: (a) the amplitude of the year‐to‐year variations; (b) the spatial heterogeneity of the driving variables and (c) the error terms associated with any particular measurement.
The responses of a lotic mayfly Nousia sp. (Ephemeroptera: Leptophlebiidae) to moving water and light of different wavelengths
Authors: Barmuta Leon A. , Mckenny Claire E. A. , Swain Roy 
Published: March 2003

1. Although laboratory studies of the behaviour of aquatic macroinvertebrates are common, there has been little critical evaluation of the importance of test conditions to them. We used a common Australian leptophlebiid mayfly, Nousia sp., to investigate responses to light, wavelength of light, presence or absence of cover and still or flowing water.2. Nousia sp. showed substantial qualitative differences in behaviour, as measured by movement, when there was no refuge (in the form of a crevice beneath a tile) present in the experimental arena.3. We found no evidence of diel periodicity in activity in Nousia sp.4. Nousia sp. did not respond to infra‐red, red or green light at a flux density of 18–19 μmol m–2 s–1.5. Nymphs were three times more likely to remain stationary in flowing water (mean velocity 0.10 m s–1) than in still water.6. We conclude that generalized assumptions about test conditions for experiments designed to quantify laboratory behaviour in benthic macroinvertebrates are unjustified and that evaluation of the individual requirements of test species should be conducted routinely.
Problems with the application of diatom‐total phosphorus transfer functions: examples from a shallow English lake
Authors: Sayer Carl D. 
Published: March 2003

1. A diatom‐total phosphorus transfer function has been applied to a sedimentary diatom sequence from Groby Pool, a small shallow lake in Leicestershire, U.K.2. Extensive aquatic plant records exist for Groby Pool dating back over two centuries. These records, in conjunction with selected aquatic pollen and herbarium diatom data, provide independent, qualitative evidence for the progression of eutrophication and its effects on aquatic plant communities and habitat structure.3. Before 1800, Groby Pool was probably mesotrophic with clear water and a diverse submerged macrophyte community, but subsequently it experienced considerable nutrient enrichment. Key evidence for this includes: (i) historical plant records indicating the loss of species associated with mesotrophic waters and their replacement by others typical of eutrophic conditions, (ii) a significant increase in the percentage of planktonic diatoms in the lake sediment record (particularly Cyclostephanos dubius) after 1890, and (iii) increases in percentages of Stephanodiscus parvus and Cocconeis placentula in the second half of the twentieth century.4. Diatom‐inferred total phosphorus (DI‐TP) estimates were inconsistent with the qualitative evidence for eutrophication at Groby Pool. In particular the DI‐TP profile was thought to overestimate phosphorus during the period of dominance by small Fragilaria spp. before 1890, and to misjudge the timing and direction of subsequent changes in nutrient loading.5. This study highlights some of the problems associated with the application of diatom‐TP transfer functions to sedimentary diatom sequences from shallow lakes. The major problem relates to the frequent dominance of non‐planktonic diatoms in the sediments of these systems, many species of which (particularly small Fragilaria spp.) appear to be more sensitive to changes in habitat availability than to phosphorus. Potential ways of improving diatom‐TP models via altered approaches to sampling are suggested.
Can life‐history traits predict the fate of introduced species? A case study on two cyprinid fish in southern France
Authors: Rosecchi Elisabeth , Thomas Frédéric , Crivelli Alain J. 
Published: March 2003

1. The ecological and economic costs of introduced species can be high. Ecologists try to predict the probability of success and potential risk of the establishment of recently introduced species, given their biological characteristics.2. In 1990 gudgeon, Gobio gobio, were released in a drainage canal of the Rhône delta of southern France. The Asian topmouth gudgeon, Pseudorasbora parva, was found for the first time in the same canal in 1993. Those introductions offered a unique opportunity to compare in situ the fate of two closely related fish in the same habitat.3. Our major aims were to assess whether G. gobio was able to establish in what seemed an unlikely environment, to compare populations trends and life‐history traits of both species and to assess whether we could explain or could have predicted our results, by considering their life‐history strategies.4. Data show that both species have established in the canal and have spread. Catches of P. parva have increased strongly and are now higher than those of G. gobio.5. The two cyprinids have the same breeding season and comparable traits (such as short generation time, small body, high reproductive effort), so both could be classified as opportunists. The observed difference in their success (in terms of population growth and colonization rate) could be explained by the wider ecological and physiological tolerance of P. parva.6. In conclusion, our field study seems to suggest that invasive vigour also results from the ability to tolerate environmental changes through phenotypic plasticity, rather than from particular life‐history features pre‐adapted to invasion. It thus remains difficult to define a good invader simply on the basis of its life‐history features.
Food quality, feeding preferences, survival and growth of shredders from temperate and tropical streams
Authors: Graça  , Cressa  , Gessner  , Feio  , Callies  , Barrios  
Published: March 2003

1. The importance of leaf quality to the nutritional ecology of lotic shredders is well established for temperate species but virtually unknown for tropical taxa. In the present study, we compared the feeding behaviour and performance of two tropical and two temperate shredders in a series of pair‐wise experiments.2. Specifically, we tested whether leaf conditioning status (stream‐conditioned versus unconditioned leaves) and geographical origin (temperate Alnus glutinosa versus tropical Hura crepitans leaves) affect the food preference, survivorship, and growth of selected shredders from low and high latitudes in a consistent manner. The animals used in experiments were the caddis‐flies Nectopsyche argentata and Phylloicus priapulus from Venezuela, Sericostoma vittatum from Central Portugal, and the amphipod Gammarus pulex from Northern Germany.3. In general, all shredders exhibited the same high preference for conditioned over unconditioned leaves, irrespective of the geographical origin of the leaf or shredder species.4. A corresponding tendency for higher growth was found for sets of animals offered conditioned leaves, with the differences in growth being clearer in the two tropical shredders. Survivorship of the two temperate species was consistently high (> 83%) regardless of the diet offered, whereas the tropical shredders survived better on conditioned (77–90%) as compared with unconditioned (54–87%) leaves, although not significantly so.5. With the exception of the temperate S. vittatum, shredders did not select or perform better on leaves to which they had previously been exposed, indicating a potential adaptation to native leaf species is over‐ridden by intrinsic leaf properties.6. Taken together, the results of this study suggest that tropical shredders may exhibit the same basic patterns of food exploitation as their temperate counterparts. Consequently, current concepts relating to the role of shredders in stream detritus dynamics may well be applicable to tropical streams, although essentially derived from temperate systems.
The functional role of burrowing bivalves in freshwater ecosystems
Authors: Vaughn Caryn C. , Hakenkamp Christine C. 
Published: March 2003

1. Freshwater systems are losing biodiversity at a rapid rate, yet we know little about the functional role of most of this biodiversity. The ecosystem roles of freshwater burrowing bivalves have been particularly understudied. Here we summarize what is known about the functional role of burrowing bivalves in the orders Unionoida and Veneroida in lakes and streams globally.2. Bivalves filter phytoplankton, bacteria and particulate organic matter from the water column. Corbicula and sphaeriids also remove organic matter from the sediment by deposit feeding, as may some unionids. Filtration rate varies with bivalve species and size, temperature, particle size and concentration, and flow regime.3. Bivalves affect nutrient dynamics in freshwater systems, through excretion as well as biodeposition of faeces and pseudofaeces. Excretion rates are both size and species dependent, are influenced by reproductive stage, and vary greatly with temperature and food availability.4. Bioturbation of sediments through bivalve movements increases sediment water and oxygen content and releases nutrients from the sediment to the water column. The physical presence of bivalve shells creates habitat for epiphytic and epizoic organisms, and stabilizes sediment and provides refugia for benthic fauna. Biodeposition of faeces and pseudofaeces can alter the composition of benthic communities.5. There is conflicting evidence concerning the role of resource limitation in structuring bivalve communities. Control by bivalves of primary production is most likely when their biomass is large relative to the water volume and where hydrologic residence time is long. Future studies should consider exactly what bivalves feed upon, whether feeding varies seasonally and with habitat, and whether significant overlap in diet occurs. In particular, we need a clearer picture of the importance of suspension versus deposit feeding and the potential advantages and tradeoffs between these two feeding modes.6. In North America, native burrowing bivalves (Unionidae) are declining at a catastrophic rate. This significant loss of benthic biomass, coupled with the invasion of an exotic burrowing bivalve (Corbicula), may result in large alterations of ecosystem processes and functions.
Population dynamics of Bythotrephes cederstroemii in south‐east Lake Michigan 1995–1998
Authors: Pothoven Steven A. , Fahnenstiel Gary L. , Vanderploeg Henry A. 
Published: March 2003

1. Population characteristics (density, size, reproductive patterns) of the predatory cladoceran Bythotrephes cederstroemii in south‐east Lake Michigan were monitored at an offshore station (110 m) in 1995–98 and at a nearshore station (45 m) in 1997–98.2. The mean density of B. cederstroemii at the offshore station was generally highest in July–September (145–914 m−2) and at the nearshore station in October–November (168–1625 m−2). In 1995 and 1998, density was also high at the offshore station in November (211–284 m−2). Fish predation may limit B. cederstroemii in nearshore regions in the summer. The maximum annual densities of B. cederstroemii for 1995–98 were generally similar to those reported from the late 1980s, when the species arrived in Lake Michigan.3. Body size increased rapidly each year to a maximum in August. Thereafter, body size declined and converged for stage‐2 and 3 individuals, suggesting food scarcity or size‐selective fish predation was affecting large individuals.4. Most reproduction occurred asexually (90%), and by stage 2 or 3 females (99%). Asexual brood size was highest when B. cederstroemii first appeared each year, and decreased in August, when larger neonates were produced. There appeared to be differences in reproductive mode for stage 2 and 3 females, with a higher percentage of stage 2 females reproducing sexually.
The macroinvertebrate communities of two contrasting Norwegian glacial rivers in relation to environmental variables
Authors: Brittain John E. , Saltveit Svein J. , Castella Emmanuel , Bogen Jim , Bønsnes Truls E. , Blakar Inggard , Bremnes Trond , Haug Ingrid , Velle Gaute 
Published: March 2003

1. Macroinvertebrate communities in two Norwegian glacial rivers, one in the western fjords (Dalelva) and one in the eastern mountains (Leirungsåi), were investigated during three time periods in 1996 and 1997.2. Channel stability variables (substratum heterogeneity/Pfankuch index/hydraulic stress) and water temperature accounted for 54% of the total inertia in the principal components analysis (PCA) ordination of environmental variables. The importance of these variables was confirmed by cluster analysis.3. The two rivers were well separated in the ordinations, with Leirungsåi showing much greater heterogeneity. This is explained by differences in altitudinal range, terrestrial vegetation and the importance and nature of tributary inputs.4. Channel stability and temperature were also important in determining faunal communities in the two glacial rivers, supporting the main determining variables in the conceptual model of glacial streams (Milner & Petts, 1994). However, clear temporal differences were apparent in the data, the two rivers being more similar during the summer period of high discharge dominated by glacial meltwater. During spring and especially during autumn environmental conditions and the macroinvertebrate fauna differed both within and between rivers.5. Diamesinae dominated in the upper reaches of both rivers, with Orthocladiinae becoming more common downstream. The dominance of Diamesinae persisted further down Dalelva because of the continued influence of glacial tributaries, whereas in Leirungsåi the influence of non‐glacial tributaries led to a change towards a greater proportion of Orthocladiinae. Lakes modified macroinvertebrate communities in both river systems.
Species richness and spatial distribution of blackflies (Diptera: Simuliidae) in streams of Central Amazonia, Brazil
Authors: Hamada Neusa , McCreadie John W. , Adler Peter H. 
Published: March 2003

1. The spatial distribution and species richness of blackflies were evaluated at 58 stream sites in Central Amazonia, Brazil. Samples were taken along a north–south axis of approximately 130 km and a east–west axis of approximately 220 km.2. Based on stream‐site characteristics, the occurrence of larvae of the six most frequently collected species was highly predictable (79.3–91.5% accuracy in prediction of occurrence). The predictive value of stream size and the presence of impoundments agrees with results of similar work in the Holarctic Region, suggesting a general responses of blackflies to environmental parameters.3. Although only 19.0% of interstream variation in species richness was explained by a regression model, results suggested that species richness was greater in larger, cooler, faster, covered streams with rocky beds than in smaller, warmer, slower, open streams with sandy bottoms. Overall, the species richness of blackflies (11 species in total) was lower than in the temperate zone suggesting, for some taxa at least, that aquatic communities do not follow the terrestrial pattern of greater species richness in the tropics.