bluuebunny/crossref_metadata_2025_split huggingface dataset:
The endemic spring snail Pyrgulopsis montezumensis in a high CO2 environment: Importance of extreme chemical habitats as refugia
Authors: O’Brien Chris , Blinn Dean W. 
Published: March 2003

1. We examined the distribution of the endemic spring snail, Pyrgulopsis montezumensis, along a gradient of dissolved free CO2 and on selected substrata in the collapsed travertine springmound of Montezuma Well, Arizona, U.S.A.2. Dissolved CO2 concentration ranged from 480 (SE ± 56) mg L−−1 near the bottom spring vents in the limnetic zone (12 m deep) of the well to < 20 mg L−−1 in an irrigation canal about 1400 m downstream from the well outlet. Spring snails occurred in habitats with 110–315 mg L−−1 dissolved CO2.3. Laboratory experiments showed that P. montezumensis tolerated a dissolved CO2 concentration up to about 400 mg L−−1 for 11 days, but displayed 40% (SE ± 4) mortality after 3 days at 728 mg L−−1 and 100% mortality after 24 h at 1200 mg L−−1. We also measured 100% mortality after 10 days at ambient concentrations (< 10 mg L−−1) of dissolved CO2.4. Although the concentration of dissolved CO2 was within the tolerance range for spring snails in the irrigation canal, inadequate substrata and increased predation probably restricted their distribution in the lower reaches of the canal. Both field measurements and laboratory selection experiments showed a significant (P < 0.001) preference for limestone substrata over submerged vegetation and fine sediments.5. We propose that springs with high dissolved CO2 may provide refugia from invertebrate and/or vertebrate predators not physiologically adjusted to the extreme chemical environment. These extreme chemical habitats probably reduce competition for resources and predation and allow resistant populations like P. montezumensis to attain high density.
Algal responses to experimental nutrient addition in the littoral community of a subtropical lake
Authors: Havens Karl E. , East Therese L. , Hwang Soon‐Jin , Rodusky Andrew J. , Sharfstein Bruce , Steinman Alan D. 
Published: March 2003

Summary1. An in situ experiment was performed in the littoral zone of a large, subtropical lake to quantify effects of phosphorus (P) and nitrogen (N) on algal biomass, productivity, nutrient content and phosphate uptake kinetics.2. We hypothesized that resident periphyton rapidly sequester added nutrients from the water column, but once a certain threshold is reached, nutrients remain in the water and permit a shift to a phytoplankton‐dominated community.3. Three duplicate sets of 1.2‐m diameter mesocosms were treated with 10, 20 or 50 μg P L−−1 in combination with 100, 200 or 500 μg N L−−1, respectively. The nutrients were added thrice weekly for 14 days, after which the treatment doses were doubled for an additional 9 days. The cumulative amounts of P and N added over the course of the study were 700 and 7000 μg L−−1, respectively. Two untreated mesocosms and two open reference sites were used as controls.4. The total P concentration in the water column of nutrient‐treated mesocosms remained low, even after prolonged high dosing. However, there was a two‐fold increase in the P content of surface algal mats and epiphyton. This indicates that some of the added P was sequestered by those components of the community. In contrast, metaphyton and epipelon displayed little or no increase in their P content. Large quantities of added P could not be accounted for in the periphyton community, and may reflect unmeasured losses to the sediments or other pools.5. Nitrogen also was depleted from the water column, but there were no significant increases in periphyton N content. Much of the added N could not be accounted for in mass balances, and may have been lost from the mesocosms through volatilization or other biochemical processes.6. Chlorophyll‐a in epiphyton increased significantly after 14 days in the highest nutrient treatment, where there also was a proliferation of Spirogyra on day 28.7. On day 28, water column samples from the highest nutrient treatment also displayed a significantly higher rate of carbon uptake, and a significantly higher concentration of midday dissolved oxygen.8. The hypothesis that phytoplankton become dominant at high nutrient loading rates was not supported. However, there were dramatic changes in community structure (increased dominance by epiphytic Spirogyra) and function (increased productivity and dissolved oxygen) in response to nutrient additions.
Effects of sequential depositional basins on lake response to urban and agricultural pollution: a palaeoecological analysis of the Qu'Appelle Valley, Saskatchewan, Canada
Authors: Dixit Aruna S. , Hall Roland I. , Leavitt& Peter R. , Quinlan Roberto , Smol JohN. P. 
Published: March 2003

1. Palaeolimnological analyses of fossil diatoms and pigments were conducted in four lakes of the Qu'Appelle Valley, Saskatchewan, Canada, to quantify the effect of upstream depositional basins on lake response to urban and agricultural human activities. Pasqua, Echo, Mission and Katepwa lakes exhibit similar modern limnological characteristics, lie sequentially downstream from urban point sources of growth‐limiting nitrogen (N), yet drain similarly large areas of farmland (38–40 × 103 km2).2. Analyses indicated that all lakes were naturally productive, contained eutrophic diatoms (i.e. Stephanodiscus niagarae, S. hantzchii, S. parvus and Aulacoseira granulata), and supported blooms of colonial (as myxoxanthophyll) and potentially toxic N‐fixing cyanobacteria (aphanizophyll), even prior to the onset of European settlement (ca. 1890) and urban development (ca. 1930).3. The onset of agricultural practices ca. 1890 had only modest effects on algal communities in the Qu'Appelle lakes, with subtle increases in eutrophic diatom species (Pasqua, Mission and Katepwa lakes) and 25–50% increases in pigment‐inferred algal abundance (Echo, Mission and Katepwa lakes).4. Despite naturally high production, total algal abundance (β‐carotene) in upstream Pasqua Lake increased by more than 350% after intense urbanization beginning ca. 1930, while eutrophic diatoms became more common and cyanobacteria populations increased ten‐fold. Principal components analysis (PCA) explained 64% of diatom variance, and identified three eras corresponding to baseline, pre‐agricultural communities (1776–1890), an era of high production (ca. 1925–1960) and recent variable community composition following tertiary treatment of urban sewage (ca. 1977–1990).5. Analyses of three downstream lakes demonstrated that urban impacts following 1930 remained evident in fossil profiles of β‐carotene and myxoxanthophyll, but that large blooms of N‐fixing cyanobacteria were restricted to the past 25 years at downstream Mission and Katepwa lakes. Similarly, PCA showed that fossil diatom assemblages exhibited little directional variation until the 1970s.6. Together, these analyses support the hypothesis that upstream lakes were effective at reducing the impacts of point‐source urban nutrients on downstream lakes. In contrast, diffuse agricultural activities had only limited impacts on water quality and these were less well ameliorated by upstream basins.
Movements of adult fish in a hybrid zone revealed by microsatellite genetic analysis and capture‐recapture data
Authors: Chenuil Anne , Crespin Laurent , Pouyaud Laurent , Patrick Berrbi 
Published: March 2003

SummaryBarbus barbusandBarbus meridionalis(Cyprinidae) form a hybrid zone in the Lergue river (southern France). We attempted to characterise the pattern of adult dispersal with the aim of understanding the evolutionary interactions maintaining this hybrid zone. In a previous capture/recapture study, movements between localities at a distance of 2.5 km or more appeared extremely rare. We therefore decided to investigate adult movement using a different method, based on genetic markers.As this hybrid zone has produced allele frequency clines, massive population movements would produce temporal variations in genetic composition at a given locality. In order to determine the relationship between gene frequency and position, we surveyed four diagnostic or semidiagnostic microsatellite loci over the hybrid zone and estimated the cline produced by introgression. Then, we focused on a single locality at the centre of the hybrid zone and established its introgression index over 11 periods during two years.The introgression index varied between periods producing significant Fst. A synthetic hybrid index, based on principal component analysis of the logit frequencies, was used for regression analyses and appeared significantly correlated with the river flow. This may be explained by displacement of adult fishes in response to flow increase. Using the information from the cline, we estimate that the most important gene frequency changes among dates, if created exclusively by population movement, correspond to a distance of 1500 m.Additionally, we performed recaptures on a finer geographic scale than previously, around the central locality. No recaptured fishes were observed at 1875 m or more downstream, and at 875 m or more upstream, from the central locality. A high proportion of recaptured fishes (20% and 12%) was found in the nearest points (312 m downstream and 437 m upstream, respectively).Thus, we established that (i) individual movements appear limited to a few hundred metres and (ii) individuals in a location tend to move in the same direction at the same time, probably in response to the same environmental factor.
Differences in nutrient limitation and grazer suppression of phytoplankton in seepage and drainage lakes of the Adirondack region, NY, U.S.A
Authors: Saunders Patricia A. , Shaw William H. , Bukaveckas§ PauL. A. 
Published: March 2003

1. For seepage and drainage lakes of the Adirondack mountain region (NY, U.S.A) hydrologic regime is correlated with physical and chemical differences that can affect phytoplankton and planktonic food webs (e.g. presence and influence of wetlands, dissolved organic carbon concentration, anoxia, nutrient cycling). We conducted short‐term (48 h), in situ enclosure experiments to evaluate the relative importance of macrozooplankton grazing and nutrient limitation of phytoplankton biomass in small Adirondack seepage and drainage lakes (N = 18, 1–137 ha). Epilimnetic dissolved organic carbon (DOC) concentrations and pH values represented the diversity of the region. We measured chlorophyll a changes in response to grazer removal (> 120 μm) and nutrient addition (∼ 10× ambient N, P, or N + P), and evaluated changes with respect to in situ light, temperature, NO3, NH4, SRP, and crustacean assemblage characters.2. Nutrient addition stimulated significant increase in chlorophyll a concentration at 11 of 18 sites (GLM, Tukey–Kramer). Phytoplankton of clearwater drainage lakes were P‐limited, whereas clearwater and brownwater seepage lakes responded to additions of N and/or N + P. Relative light availability explained half the variance in response to nutrient addition in drainage (r2 = 0.48), but not seepage lake experiments (P > 0.05).3. We observed responses to grazer removal at eight of 18 sites, usually clearwater drainage lakes. Crustacean grazing may be as significant as nutrient limitation of [chl a] for many drainage lake phytoplankton assemblages. Responses were related to in situ density of zooplankton only in drainage lakes. Light explained some variability in response to grazer removal for drainage (r2 = 0.35) and seepage lake experiments (r2 = 0.35).4. These experiments provide evidence that hydrology may ultimately play an important role in determining nutrient and grazer regulation of phytoplankton. Proximate mechanisms affecting our results may be associated with differences in wetland vegetation, [DOC], and nutrient cycling.
Riffles as barriers to interpool movement by three cyprinids (Notropis boops, Campostoma anomalum and Cyprinella venusta)
Authors: Schaefer Jacob 
Published: March 2003

1. The effects of riffles as barriers to movement of stream fish was investigated in a set of eight large outdoor artificial streams. Pools were 183 cm in diameter and 45 cm deep; riffles were 183 cm long and 43 cm wide. Rates of movement of three species of minnows (Cyprinidae) (Campostoma anomalum, Cyprinella venusta and Notropis boops) among pools were measured at four riffle current velocities (0, 15, 30 and 45 cm s–1), three thalweg depths (10, 50 and 100 mm), two riffle lengths (183 and 549 cm), and with and without the threat of predation. Visual observation and video cameras were used to quantify movement rate.2. Mean movement rate (percentage of fish crossing a riffle each 30 min) was 18.1% at 0 cm s–1 and only 1.8 at 45 cm s–1. Movement rate was 7.2% with no predators present and 20.2% with caged predators in pools. Notropis boops had a lower rate of movement than C. venusta or C. anomalum across all trials. The mean group size (number of individuals crossing a riffle together) was 1.2 fish overall, indicating most movement was by individuals and not groups. Group size was significantly greater only with shallow riffles or under the threat of predation.3. Overall biotic and abiotic factors in these artificial streams do influence movement rates and may affect movement among pools in natural streams.
The influence of macrophytes on the spatial distribution of littoral rotifers
Authors: Duggan Ian C. , Green John D. , Thompson Keith , Shiel Russell J. 
Published: March 2003

1. The effect of macrophytes on the spatial distribution of littoral rotifers was examined in Lake Rotomanuka, New Zealand (37°55′S, 175°19′E). Total rotifer abundances and those of abundant species, were compared between three macrophyte species, Myriophyllum propinquum, Eleocharis sphacelata and Egeria densa, and spatially across a littoral transect in relation to these species.2. The abundances of many species, for example Euchlanis dilatata, Lecane closterocerca and L. lunaris, differed significantly between macrophyte species. More planktonic forms, Ascomorpha saltans, Keratella cochlearis and Synchaeta oblonga, however, showed no significant preference for macrophyte species.3. Differences in rotifer abundances were evident even when different species of macrophyte grew in close proximity to one another, indicating that variations in physical and chemical conditions, which occur in the littoral of Lake Rotomanuka, could be largely discounted for much of the variation between macrophyte species.4. Variation in rotifers between macrophytes was probably the result of a number of factors, including differences in macrophyte morphology, macrophyte age, epiphytic algal growths and the differential effects of predation by invertebrates and fish between macrophytes.5. Variability of rotifer abundances spatially across the ecotone was less marked than between macrophyte species. The species of macrophyte occurring, and therefore the community composition and distribution of macrophyte species in the littoral, appears to be a major influence in the spatial structuring of rotifer communities in the littoral region of lakes.
Long‐term changes of planktonic rotifers in a subtropical Chinese lake dominated by filter‐feeding fishes
Authors: Shao Zhaojun , Xie Ping , Zhuge Yan 
Published: March 2003

1. The long‐term changes (1956–1998) in density and species composition of planktonic rotifers were studied at two sampling stations (I, II) of Lake Donghu, a shallow eutrophic Chinese Lake densely stocked with filter‐feeding fishes. Annual average densities of rotifers increased with an increase in fish yield and eutrophication, whilst species number decreased from 82 in 1962–1963 to 62 in 1994–1998.2. During 1962–98, some species such asAnuraeopsis fissa,Polyarthraspp. (includingP. dolichoptera&P. vulgaris), Trichocerca pusillaandSynchaeta oblongaincreased their percentage in abundance remarkably, whilst the proportion ofKeratella cochlearisdecreased at two relatively eutrophic stations from 19 to 4.2% at Station I and from 30 to 3.2% at Station II.3. The highrmaxofA. fissaprobably made it more successful than other rotifers under high predation pressure by planktivorous fish. The decrease in theK. cochlearispopulation might be attributed partly to predation byCyclops vicinus.4. Small rotifers were less vulnerable to fish predation than large‐sized cladocerans. Decreases in cladocerans coincided with increases in rotifers, suggesting that the indirect effect of fish predation on cladocerans might have partly contributed to the population development of rotifers in Lake Donghu during recent decades.5. We also conducted surveys (1994–1998) of seasonal dynamics of rotifers at four sampling stations (I–IV) which have varied in trophic status after fragmentation of the lake in the 1960s. A total of 75 species were identified at the four stations. Both densities and biomass of rotifers were considerably higher in the two more eutrophic stations than in the two less eutrophic stations. This indicates that the population increase of rotifers at Stations I and II during recent decades might be partly attributed to eutrophication of the lake water.
Diurnal variations in the carbon chemistry of two acidic peatland streams in north‐east Scotland
Authors: Dawson J. J. C. , Billett M. F. , Hope D. 
Published: March 2003

1. Two acidic peatland upland streams in north‐east Scotland draining catchments of 1.3 and 41.4 km2 were sampled each season for 2 years to investigate diurnal variations in dissolved and gaseous forms of carbon. Stream metabolism, alkalinity, discharge, pH, air and water temperatures were measured to aid data interpretation.2. Free CO2 showed marked diurnal variation with lowest concentrations during the period from late morning to early afternoon and highest during the hours of darkness. Although alkalinity and pH also showed some diurnal fluctuations, in comparison with other more productive alkaline systems, variation was small. Dissolved organic carbon (DOC) showed no significant diurnal pattern. However, significant changes in stream discharge influenced DOC concentrations, as well as over‐riding diurnal patterns of free CO2, alkalinity and pH.3. The highest diurnal ratios (maximum concentration/minimum concentration) in CO2, gross primary productivity (GPP) and community respiration (CR) occurred in spring and summer and the lowest in autumn and winter. Variation in biotic in‐stream processes caused changes in CO2 concentrations and temperature affected both the solubility of CO2 and changes in up‐stream CO2 inputs. There was no significant difference in diurnal fluctuations between the two orders of stream studied.4. The mean GPP (as CO2) was 0.81 g CO2 m−2 day−1 and mean CR 2.67 g CO2 m−2 day−1. The mean primary production/respiration (P/R) ratio was 0.26 ± 0.09 and 0.33 ± 0.15 in the first and second order streams, respectively. These values are low compared with published data because these heterotrophic headwater streams are dominated by benthic respiration and upstream allochthonous inputs with little autotrophic metabolism, particularly during the colder autumn and winter months.5. The results have implications for the calculation of dissolved inorganic carbon (DIC) fluxes in streamwater. Samples taken during daylight hours tend to have lower concentrations of free CO2 and HCO3− than samples taken during darkness. During spring, concentrations of free CO2 were measured up to 2.4 (annual mean 1.8) times higher at night than during the day at a similar discharge. It is suggested that fluxes based on daytime measurements alone will under‐estimate the annual flux of these determinands in streamwater by as much as 40%.
Relationships between land use, spatial scale and stream macroinvertebrate communities
Authors: Sponseller R. A. , Benfield E. F. , Valett H. M. 
Published: March 2003

1. The structure of lotic macroinvertebrate communities may be strongly influenced by land‐use practices within catchments. However, the relative magnitude of influence on the benthos may depend upon the spatial arrangement of different land uses in the catchment.2. We examined the influence of land‐cover patterns on in‐stream physico‐chemical features and macroinvertebrate assemblages in nine southern Appalachian headwater basins characterized by a mixture of land‐use practices. Using a geographical information system (GIS)/remote sensing approach, we quantified land‐cover at five spatial scales; the entire catchment, the riparian corridor, and three riparian ‘sub‐corridors’ extending 200, 1000 and 2000 m upstream of sampling reaches.3. Stream water chemistry was generally related to features at the catchment scale. Conversely, stream temperature and substratum characteristics were strongly influenced by land‐cover patterns at the riparian corridor and sub‐corridor scales.4. Macroinvertebrate assemblage structure was quantified using the slope of rank‐abundance plots, and further described using diversity and evenness indices. Taxon richness ranged from 24 to 54 among sites, and the analysis of rank‐abundance curves defined three distinct groups with high, medium and low diversity. In general, other macroinvertebrate indices were in accord with rank‐abundance groups, with richness and evenness decreasing among sites with maximum stream temperature.5. Macroinvertebrate indices were most closely related to land‐cover patterns evaluated at the 200 m sub‐corridor scale, suggesting that local, streamside development effectively alters assemblage structure.6. Results suggest that differences in macroinvertebrate assemblage structure can be explained by land‐cover patterns when appropriate spatial scales are employed. In addition, the influence of riparian forest patches on in‐stream habitat features (e.g. the thermal regime) may be critical to the distribution of many taxa in headwater streams draining catchments with mixed land‐use practices.
Long‐term effects of successive Ca(OH)2 and CaCO3 treatments on the water quality of two eutrophic hardwater lakes
Authors: Prepas Ellie E. , Babin Jay , Murphy Tom P. , Chambers Patricia A. , Sandland Greg J. , Ghadouani Anas , Serediak Mark 
Published: March 2003

1. Whole‐lake experiments were conducted in two hardwater lakes (Halfmoon and Figure Eight) in Alberta, Canada, to investigate the effectiveness of repeated lime (slaked lime: Ca(OH)2 and/or calcite: CaCO3) treatments (5–78 mg L–1) for up to 7 years.2. Randomized intervention analysis of intersystem differences between the experimental and three reference lakes demonstrated a decline in euphotic total phosphorus and chlorophyll a concentrations in the experimental lakes after repeated lime treatments.3. After the second lime application to Halfmoon Lake, mean winter total phosphorus release rates (TPRR) decreased to < 1 mg m–2 day–1 compared with 3.6 mg m–2 day–1 during the winter after initial treatment. In the final year of lime application, mean summer TPRR decreased to 4.5 mg m–2 day–1 compared with 7.6 mg m–2 day–1 in the pre‐treatment year.4. Mean macrophyte biomass declined and species composition was altered at 1 and 2 m depths in Figure Eight Lake during lime application. Over the first 6 years of treatment, macrophyte biomass at 2 m declined by 95% compared with concentrations recorded during the initial treatment year. In the last year of the study, macrophyte biomass at 2 m reached initial treatment concentrations, which coincided with the greatest water transparency. Over the treatment period, macrophyte species shifted from floating to rooted plants.5. Multiple lime applications can improve water quality in eutrophic hardwater lakes for periods of up to 7 years.