bluuebunny/crossref_metadata_2025_split huggingface dataset:
Application of an index of biological integrity (IBI) to fish assemblages of the rivers Khan and Kshipra (Madhya Pradesh), India
Authors: Ganasan V. , Hughes Robert M. 
Published: March 2003

1. A multimetric index of fish assemblage integrity was developed and similarity analyses were conducted on fish species in two central Indian rivers and the effects of distance from municipal and industrial effluents on those indices then evaluated.2. Five metrics from Karr et al. (1986
, Illinois Natural History Survey Special Publication 5, Urbana, IL) were adopted: intolerant species richness, % omnivorous individuals, % top carnivore individuals, total number of individuals and % individuals with anomalies. Seven new metrics (native species richness, native family richness, benthic species richness, water column species richness, % non‐native individuals, % tolerant individuals and % herbivorous individuals) were added.3. Non‐native individuals represented 1–55% of the assemblages at sampled sites which held fish.4. Fish were present at eleven sites and not collected at two sites, despite heavy metal concentrations exceeding U.S. Environmental Protection Agency acute criteria at all sites.5. Two types of metric scoring were examined. The traditional 5–3–1 method showed the same pattern as continuous scoring from 0 to 10, but produced a higher integrity class at one site.6. Scores on our modified index of fish assemblage integrity increased with distance downstream from a major effluent source in each river. Jaccard similarity scores between the least disturbed downstream site and all other sites decreased with increasing distance and disturbance.7. It was concluded that Karr’s original index and its theoretical foundations are easily adaptable, even to an ichthyofauna containing no species, and only two families (Cyprinidae, Poeciliidae), in common with the midwestern United States.
Migratory drift of larval freshwater shrimps in two tropical streams, Puerto Rico
Authors: March J. G. , Benstead J. P. , Pringle C. M. , Scatena F. N. 
Published: March 2003

Summary1. Migratory shrimps are often major biotic components of tropical stream communities, yet spatial and temporal patterns of their migration have yet to be described. This information is of increasing importance given the continued fragmentation of tropical streams by damming and water abstraction/diversion, which can disrupt migratory life cycles.2. Larval amphidromous shrimps are released by adult females in freshwater streams. They then drift passively to an estuarine habitat where they metamorphose before migrating back upstream. Drift of larval shrimps was sampled over two to five 24‐h periods at each of three sites along two rivers that drain the Luquillo Experimental Forest in Puerto Rico: the Espíritu Santo (10, 135 and 335 m a.s.l.) and the Mameyes (10, 90 and 290 m a.s.l.). A total of seventeen diel samplings were conducted.3. Shrimp drift increased in the downstream direction in both catchments, and had a significant positive exponential relationship with length of stream channel above each site. There was no significant difference between catchments with respect to mean daily drift rate per km of stream channel. Maximum observed larval shrimp density was 69 102 larvae 100 m–3 (1.7 g dry mass 100 m–3), which is high relative to published invertebrate drift studies.4. The pattern of shrimp drift agreed with the ’risk of predation hypothesis‘. In stream reaches with predatory fish, drift of larval shrimps occurred at night and was slight during the day. A nocturnal peak in drift occurred between 19.00 and 22.00 h. At a high‐altitude site, where predatory fish were absent, no diel pattern was discernible.5. The present study provides information on the timing of migratory drift of larval shrimps, which can minimize the adverse effects of water abstraction from streams draining the Luquillo Experimental Forest. Elimination of water withdrawal during peak larval drift after dark will significantly reduce shrimp mortality.
The impact of flash floods on microbial distribution and biogeochemistry in the parafluvial zone of a desert stream
Authors: Holmes Robert M. , Fisher Stuart G. , Grimm Nancy B. , Harper Bryan J. 
Published: March 2003

Summary1. The impact of flash flooding on microbial distribution and biogeochemistry was investigated in the parafluvial zone (the part of the active channel lateral to the surface stream) of Sycamore Creek, a Sonoran Desert stream in central Arizona.2. It was hypothesized that subsurface bacteria were dependent on the import of algal‐derived organic matter from the surface stream, and it was therefore predicted that microbial numbers and rates of microbially mediated processes would be highest at locations of surface to subsurface hydrologic exchange and at times when algal biomass was high.3. Prior to a flash flood on 19 July 1994, chlorophyll a was high (≈ 400 mg m–2) in the surface stream and microbial numbers were highest at the stream–parafluvial interface and declined along parafluvial flowpaths, supporting the hypothesized algal–bacterial linkage. Immediately following the flash flood, chlorophyll a was low (≈ 7 mg m–2), and microbial numbers were reduced at the stream–parafluvial interface.4. Counter to expectations, parafluvial functioning (in terms of nitrate production and dissolved oxygen decline along flowpaths) re‐established immediately after the flood receded. Therefore, material other than algal exudates supported parafluvial metabolism immediately postflood, and terrestrially derived dissolved organic matter is the likely source.5. Algae in the surface stream recovered quickly following flooding, but recovery of parafluvial bacteria lagged somewhat behind. These results highlight the importance of surface–subsurface interaction to stream ecosystem functioning and show that the nature of these interactions changes substantially in successional time.
Estimating the effective clearance rate and refiltration by zebra mussels, Dreissena polymorpha, in a stratified reservoir
Authors: Yu Neng , Culver David A. 
Published: March 2003

Summary1. The grazing impact of zebra mussels, Dreissena polymorpha Pallas, is often evaluated by applying the individual filtration rate measured in the laboratory to the field abundance and then by comparing the total volume of water filtered with the whole lake volume. Since this approach overlooks refiltration, it overestimates the grazing impact of zebra mussels. To deal with this problem, the present authors developed an in situ method for collecting faeces and pseudofaeces to measure the actual volume of water that is cleared of suspended particles by Dreissena in a unit time under a given set of environmental conditions. This is termed the effective clearance rate (ECR).2. The experiment was conducted in Hargus Lake, OH, U.S.A., a small thermally stratified reservoir, to test the effects of spatial aggregation, mussel density and the concentration of particulate inorganic matter (PIM) on the effective clearance rate of Dreissena.3. Over 40 measurements, the ECR values ranged from 15.3 to 68.6 mL ind−−1 h−−1. Much of the variation can be explained by colony form, mussel density and seston concentration. The effects of these variables were all statistically significant. The average ECR for isolated individuals was higher than that for those in clumps (40.4 versus 32.8 mL ind−−1 h−−1), which is attributed to increased refiltration in the cores of the clumps. The ECR decreased with increased zebra mussel density because of intensified competition for food particles within the group. The ECR increased with increased PIM concentration in the lake water, which may be interpreted as a result of enhanced water mixing which ultimately caused increases in both sediment resuspension and particle delivery to the mussels.4. Taking the filtration rates for a 20‐mm mussel to be between 116 and 234 mL ind−−1 h−−1, based on data from the literature, the clumped mussels under the present experimental conditions would have a refiltration ratio between 3.4 and 6.9.5. The present authors developed an areal clearance model which predicts that seston removal by the Dreissena population is limited by the particle delivery from the ambient water to the mussel bed and will reach a maximum value beyond which no further increase will occur with increased population density.6. It is concluded that the direct grazing impact of zebra mussel on phytoplankton in thermally stratified lakes is much less effective than predicted from simple filtration rate estimation.
Pectoral fin size in a fish species with paternal care: a condition‐dependent sexual trait revealing infection status
Authors: Bakker Theo C. M. , Mundwiler Beat 
Published: March 2003

Summary1. The three‐spined stickleback, Gasterosteus aculeatus L., is a territorial fish with exclusive male parental care. Males oxygenate the eggs with fanning movements of their pectoral fins. The present authors investigated whether the apparent sexual differences in the functional demands of the pectoral fins have resulted in sexual differences in fin size. If males have relatively larger pectoral fins, females may use this as a signal to aid their mate choice for good fathers. Therefore, further objectives were to study the condition‐dependency of relative pectoral fin size in males and the relationship with male parasite load.2. Reproductively active males possessed relatively larger pectoral fins than females in both wild‐caught and laboratory‐bred fish.3. In the field, caring males with relatively large pectoral fins were in better physical condition and had more food in their stomachs.4. Relatively small pectoral fins and poor body condition were associated with infection by the intestinal parasite Pomphorhynchus laevis (Acanthocephala), the prevalent parasite species in the study population.
Periphyton removal related to phosphorus and grazer biomass level
Authors: Anderson E. L. , Welch E. B. , Jacoby J. M. , Schimek G. M. , Horner R. R. 
Published: March 2003

Summary1. The proliferation of nuisance periphyton in enriched streams may be dependent on the biomass of the grazing macroinvertebrates present. In the present study, the effectiveness of grazer size and biomass in controlling periphyton and the extent to which grazing effectiveness was affected by enrichment level were determined.2. Two sets of experiments with two caddisfly grazers were conducted in laboratory channels during spring and summer 1995 and 1996. The first set tested the combined effect of phosphorus enrichment and grazing, while the second set tested the effect of variable grazer biomass on periphyton biomass.3. Grazing reduced periphyton biomass in excess of 80%, compared to ungrazed controls. Grazers were equally effective in controlling filamentous green algae, Stigeoclonium, diatoms and small colonial greens. Near complete removal of periphyton biomass by grazing occurred at even at the lowest grazer biomass level (750 mg m−−2, i.e. approximately one‐third of natural levels).4. Grazing controlled periphyton biomass more than did enrichment with soluble reactive phosphorus (SRP).5. Grazing rates in the phosphorus‐grazing interaction experiments averaged about 6 mg chl a g invertebrate−−1 day−−1, which was similar to past work in these channels and elsewhere, while rates were about five‐fold higher in the variable grazer biomass experiments.6. Simulating effects of SRP and grazing with a calibrated model suggests that higher SRP levels would be necessary to exceed a nuisance periphyton biomass level if grazers were present. However, if grazer biomass was more than 1500 mg m−−2, a nuisance level would probably not be exceeded at any SRP.
Establishing the condition of lowland floodplain rivers: a palaeo‐ecological approach
Authors: Thoms M. C. , Ogden R. W. , Reid M. A. 
Published: March 2003

Summary1. Current approaches for determining river ‘health’ rely on the establishment of a ‘reference’ condition. This is often difficult to achieve for lowland floodplain river systems because of the lack of pristine or pre‐impacted sites and process models capable of predicting the effect of natural and human disturbances.2. Using examples from the River Murray, Australia, this paper highlights the benefits of using palaeo‐ecological studies in deciding on benchmark or pre‐European settlement conditions for lowland floodplain river systems.3. Physical, chemical and biological analyses of sediment obtained from shallow cores (< 2 m) extracted from a variety of floodplain sites on the River Murray and its tributaries reveal the extent and timing of catchment disturbances on this lowland river. Rates of sedimentation have increased by an order of magnitude since settlement; sediments now being deposited are finer, having implications for the nutrient status of the floodplain and the accumulation of heavy metals associated with these sediments. There has also been a sustained drop in the macrophyte cover of billabongs in the area, as inferred by chydorid cladoceran assemblages. The pre‐European settlement diatom assemblages do not resemble those presently accumulating in billabongs in the region.4. Whilst initially developed for lentic studies, palaeo‐ecological studies are relevant to the establishment of benchmark conditions for lowland floodplain rivers. They are relatively straightforward, incorporate both historical and contemporary ecological information and can be applied to any lowland system.
Invasion of North American drainages by alien fish species
Authors: Gido Keith B. , Brown James H. 
Published: March 2003

1. Data from the literature were used to document colonization patterns by introduced freshwater fishes in 125 drainages across temperate North America. We analysed this data set to quantify susceptibility to invasion, success of the invaders and changes in species richness.2. Drainages with a high number of impoundments, large basin area and low native species diversity had the greatest number of introduced species. Those drainages containing few native fishes exhibited great variation in the number of invaders, while waters with a rich native fauna contained few introduced species. However, this pattern did not differ significantly from random simulations because the pool of potential invaders is greater for drainages with low species richness.3. In most drainages, there were more introduced than imperilled or extirpated species, suggesting that invaders tend to increase overall species richness.4. These patterns suggest that North American fish communities are not saturated with species, but instead, are capable of supporting higher levels of diversity if the pool of potential colonists and the rate of colonization from that pool is increased.
Crowding‐induced changes in growth, reproduction and morphology of Daphnia
Authors: Burns Carolyn W. 
Published: March 2003

SUMMARY

Daphnia may reach high population densities seasonally, or in patches, in lakes. To test the effects of chemicals released by high daphniid densities on their life‐history traits, nine species of Daphnia, D. magna, D. pulicaria, D. pulex, D. hyalina, D. galeata, D. laevis, D. lumholtzi, D. ambigua and D. cucullata, were grown in water from crowded Daphnia cultures in a flow‐through system in the presence of abundant food.
Water from Daphnia at 85 L‐1 depressed growth rate, and lowered body size and clutch at first reproduction of six species of small‐bodied Daphnia (adult body length < 1.8 mm), but had no significant effects on larger species. Two clones of D. pulex differed in their growth rate in response to crowding, indicating that response patterns may vary within species.
Chemicals released by crowded D. magna reduced tail spine length in D. lumholtzi and D. cucullata by 37% and 11%, respectively, and induced changes in carapace morphology in D. lumholtzi and D. ambigua.
Chemicals released by crowded conspecifics may provide an additional, density‐dependent mechanism of population regulation; when large species of Daphnia coexist at a high population density with small species, these chemicals may reinforce the competitive advantage of large species.
Minimal models of top‐down control of phytoplankton
Authors: Scheffer Marten , Rinaldi Sergio 
Published: March 2003

1. A set of models describing the dynamics of top‐down control of phytoplankton by Daphnia in lakes is reviewed. The basis of these models is a simple and well‐known model that has been used, among other things, to demonstrate the paradox of enrichment.  2. We discuss minimal extensions that allow this model to mimic the effects of spatial heterogeneity, planktivory, seasonality and inedible algae.  3. These models generate hypotheses about mechanisms that may cause patterns observed in the field such as:

Spatial heterogeneity stabilizes plankton dynamics, and causes enrichment to result in a gradual increase of both zooplankton and algal biomass.
Daphnia populations can collapse at a threshold level of predation pressure from fish, rather than gradually become less abundant.
Absence of Daphnia in summer may typically be caused by the combination of food shortage followed by suppression by fish.
The spring clear‐water phase and various other aspects of the typical seasonal dynamics of Daphnia and algal biomass can simply be explained from the seasonal rise and fall of rates of biological processes and the reproduction cycle of fish.
Depending on the conditions, cyanobacterial dominance can be stimulated but also suppressed by Daphnia.

4. We discuss the way in which such very simple models may contribute to the building of theories about plankton dynamics in the field, and the caveats of interpreting wrongly the message from models.
Role of transported particulate organic matter in the macroinvertebrate colonization of litter bags in streams
Authors: Dangles Olivier , Guerold François , Usseglio‐Polatera Philippe 
Published: March 2003

1. The exposure of mesh litter bags has been widely used to investigate the role of benthic macroinvertebrates in leaf processing in freshwaters. In this sense, several studies have related litter bag breakdown rates to the presence of colonizing invertebrates. A possible confounding factor in such experiments is that the litter bags trap suspended particulate organic matter that can itself attract invertebrate colonists, irrespective of the intended experimental treatment.2. We attempted to quantify the accumulation of particulate organic matter (POM) within litter bags and to investigate its possible impact on macroinvertebrate density and richness. In seven headwater forested streams we exposed mesh bags filled either with beech leaves (Fagus sylvatica) or with plastic strips of an equal surface area.3. Principal component analysis (PCA) showed that bag type and stream were the main explanatory variables for invertebrate colonization and POM accumulation within the bags. In contrast, there was little variation among sampling dates (6.4% of the total inertia).4. The accumulated POM within the bags was substantial (up to 8.83 g ash‐free dry mass (AFDM)) but highly variable among sites (mean from 0.32 to 4.58 g AFDM). At each of the seven sites, both richness and abundance of invertebrates were positively correlated with the mass of accumulated POM in bags. Macroinvertebrate colonization (notably taxon richness) was directly linked with the quantity of POM accumulated.5. Our findings provide evidence of a potential pitfall in linking invertebrates to litter processing in mesh bags, particularly when large amounts of POM, entrained in stream flow, accumulate within the bags. An evaluation of the POM mass trapped in litter bags could account for the erratic patterns sometimes observed in their colonization by invertebrates.
Response of bacterial extracellular enzymes to inundation of floodplain sediments
Authors: Burns A. , Ryder D. S. 
Published: March 2003

1. Bacterial extracellular enzymes provide a measure of microbial response to organic matter supply, pivotal to the recovery of riverine food webs after disturbances such as floods.2. We examined the effects of flood duration on extracellular enzyme response from riverbank and floodplain wetland sediments from the Murrumbidgee River, south‐east Australia.3. There were strong temporal peaks in enzyme activity from both riverbank and billabong sites, peaking between 1 and 5 days following flooding and with a general decline by 21 days. A dominance of non‐glucosidase and xylosidase enzymes resulted in no significant differences between billabong and riverbank sediments. This supports the hypothesis that regulated Australian river systems are driven by autochthonous carbon sources.4. The short response time of the glucosidase after flooding suggests that even short pulses (24 h) in high flows may stimulate bacterial activity, as dissolved organic carbon (DOC) loads also peak at this time. However, a longer wetting time may be needed to drive hydrolysis of the proteins, fatty acids and longer chain polysaccharides, whether in the littoral zone of the river or connection with the floodplain.
Spatio‐temporal variation in macroinvertebrate assemblages of glacial streams in the Swiss Alps
Authors: Robinson C. T. , Uehlinger U. , Hieber M. 
Published: March 2003

1. Changes in water chemistry, benthic organic matter (BOM), and macroinvertebrates were examined in four different glacial streams over an annual cycle. The streams experienced strong seasonal changes in water chemistry that reflected temporal changes in the influence from the source glacier, especially in water turbidity, particulate phosphorus and conductivity.2. Nitrogen concentrations were high (nitrate‐N values were 130–274 μg L–1), especially during spring snowmelt runoff. Benthic organic matter attained >600 g m–2 dry mass at certain times, peaks being associated with seasonal blooms of the alga Hydrurus foetidus.3. Macroinvertebrate taxon richness was two to three times higher (also numbers and biomass) in winter than summer suggesting winter may be a more favourable period for these animals. Benthic densities averaged 1140–3820 ind. m–2, although peaking as high as 9000 ind. m–2. Average annual biomass ranged from 102 to 721 mg m–2, and reached >2000 mg m–2 at one site in autumn.4. Taxa common to all sites included the dipterans Diamesa spp. and Rhypholophus sp., the plecopterans Leuctra spp. and Rhabdiopteryx alpina, and the ephemeropterans Baetis alpinus and Rhithrogena spp. Principal components analysis clearly separated winter assemblages from those found in summer.