bluuebunny/crossref_metadata_2025_split huggingface dataset:
Selective predation on an introduced zooplankter (Bythotrephes cederstroemi) by lake herring (Coregonus artedii) in Harp Lake, Ontario
Authors: Coulas Robert A. , Macisaac Hugh J. , Dunlop Warren 
Published: March 2003

1.Bythotrephes cederstroemi(Crustacea: Onychopoda: Cercopagidae) invaded Harp Lake, Ontario in 1993, since when the zooplankton community has shifted from dominance of small‐bodied to large‐bodied species. During 1995 diets of adult lake herring (Coregonus artedii), Harp Lake’s primary planktivorous fish, were examined to determine the extent to which this conspicuous zooplankter has become integrated into the lake’s foodweb and whether fish condition has been affected in consequence.2.BythotrephesandDaphnia galeata mendotaewere strongly preferred prey, whilstHolopedium gibberumand calanoid and cyclopoid copepods were negatively selected by lake herring. Predation onBythotrephesandHolopediumwas not size‐selective, althoughD. galeata mendotaeand calanoid copepods (Leptodiaptomus minutusandL. sicilis) consumed by herring were significantly larger than co‐occurring conspecifics in the lake.3. Caudal spines ofBythotrephesmay form boluses in lake herring stomachs. However, the number of caudal spines in fish digestive tracts did not differ significantly from the number ofBythotrephes’ mandible pairs, indicating that the former were not differentially retained.4. Lake herring weight‐at‐length relationships in lakes in Muskoka, Ontario, invaded byBythotrephesdid not differ from those in adjacent non‐invaded lakes, indicating thatBythotrephesinvasion of lakes apparently has not affected condition of lake herring.
Abiotic aspects of channels and floodplains in riparian ecology
Authors: Huggenberger P. , Hoehn E. , Beschta R. , Woessner W. 
Published: March 2003

Summary1. The ecology of riparian zones is enormously influenced by the heterogeneous sedimentary structures and associated complex hydrologic flow paths that mediate surface‐ and groundwater exchanges. Sedimentary structures form a three‐dimensional, dynamic framework that controls subsurface flow and the vertical and horizontal exchange of water between channels and floodplains in gravel bed rivers. The modern structure of the bed sediments reflects the legacy of cut and fill alluviation for a particular river basin.2. Highly permeable sedimentary textures, particularly open framework gravels, allow rapid exchange between surface and groundwaters.3. Ground penetrating radar provides high resolution information on the nature and three‐dimensional distribution of the sediments within the shallow subsurface (4–25 m) of gravel bed rivers. Bed sediments can be mapped at the decimeter scale.4. Exchange and mixing of ground and channel water occurs along losing, gaining and flow‐through reaches as determined by the hydraulic gradient and transmissivity of the bed sediments.5. Spatial and temporal patterns of surface‐ and groundwater interactions can be quantified by mass flux measurements and by assessing geochemical contrasts. Natural tracers, such as temperature or radon, are well suited for mapping exchange sites and quantifying interactions. Artificial signals produced by injecting anions, like chloride, bromide and organic dyes are also useful.6. The study of riparian ecosystems requires an understanding of the geomorphic structures and processes that build and maintain bed sediments and flow pathways through them.
Effects on phytoplankton of nutrients added in conjunction with acidification
Authors: Findlay D. L. , Hecky R. E. , Kasian S. E. M. , Stainton M. P. , Hendzel L. L. , Schindler E. U. 
Published: March 2003

1. The effects of nitric acidification on phytoplankton were studied in a small, eperimentally manipulated, oligotrophic lake (L302N) in the Eperimental Lakes Area of Canada. The focus was altered after 9 years of acidification to investigate the possibility of using nutrient additions to stimulate recovery, followed by a controlled incremental recovery, in which the pH was increased to a predetermined target level.2. Five years of additions of HNO3 to L302N reduced its pH from 6.5 to 6.1. Nitrate concentration increased because the algal community was severely P deficient. The phytoplankton community structure and productivity were not significantly affected by these additions.3. The phytoplankton community was significantly affected when pH was subsequently decreased over three successive years from 6.1 to 5.1 by the addition of HCl. Dominance shifted from chrysophytes to a co‐dominance of chlorophytes and dinoflagellates, which altered the size structure of the community. Species diversity significantly decreased, although phytoplankton productivity remained unchanged.4. At pH 5.1 nitrate and sulphate additions were made, creating conditions like those in lakes in eastern North America, which receive high loadings of nitrogen from the atmosphere. The phytoplankton assemblage shifted to dominance by small coccoidal chlorophytes. However, biomass and productivity were unaffected.5. Finally, phosphate, as phosphoric acid, was added, along with nitrate and sulphate, to the epilimnion, which stimulated internal alkalinity generation and productivity. It is concluded that CO2 concentrations and the form of N (nitrate vs. ammonia) affect algal composition but that P determines algal biomass and productivity. Chlorophytes were found to be good competitors for P when N and CO2 were high; it is epected that cyanobacteria would be more competitive for P in low CO2 systems. Conversely, dinoflagellates are most competitive in systems with low pH and high P, such as that which occurred in L302N. Although the P additions reduced N concentrations and created alkalinity, this is not a recommended remedial procedure in acidified lakes because it enhanced dinoflagellate abundance, which has been associated with fish kills.6. When all additions ceased, the pH of L302N recovered from 5.1 to 5.8, chrysophytes and chlorophytes became more abundant and dinoflagellates decreased in abundance. Phytoplankton biomass decreased and species diversity increased. Phytoplankton productivity remained unchanged
E‐mail: J.Laybourn‐Parry@nottingham.ac.ukAnnual plankton dynamics in an Antarctic saline lake
Authors: Bell Elanor M. , Laybourn‐Parry Johanna 
Published: March 2003

Summary1. The plankton dynamics of Ace Lake, a saline, meromictic basin in the Vestfold Hills, eastern Antarctica was studied between December 1995 and February 1997.2. The lake supported two distinct plankton communities; an aerobic microbial community in the upper oxygenated mixolimnion and an anaerobic microbial community in the lower anoxic monimolimnion.3. Phytoplankton development was limited by nitrogen availability. Soluble reactive phosphorus was never limiting. Chlorophyll a concentrations in the mixolimnion ranged between 0.3 and 4.4 μg L−−1 during the study period and a deep chlorophyll maximum persisted throughout the year below the chemo/oxycline.4. Bacterioplankton abundance showed considerable seasonal variation related to light and substrate availability. Autotrophic bacterial abundance ranged between 0.02 and 8.94 × 108 L−−1 and heterotrophic bacterial abundance between 1.26 and 72.8 × 108 L−−1 throughout the water column.5. The mixolimnion phytoplankton was dominated by phytoflagellates, in particular Pyramimonas gelidicola. P. gelidicola remained active for most of the year by virtue of its mixotrophic behaviour. Photosynthetic dinoflagellates occurred during the austral summer, but the entire population encysted for the winter.6. Two communities of heterotrophic flagellates were apparent; a community living in the upper monimolimnion and a community living in the aerobic mixolimnion. Both exhibited different seasonal dynamics.7. The ciliate community was dominated by the autotroph Mesodinium rubrum. The abundance of M. rubrum peaked in summer. A proportion of the population encysted during winter. Only one other ciliate, Euplotes sp., occurred regularly.8. Two species of Metazoa occurred in the mixolimnion; a calanoid copepod (Paralabidocera antarctica) and a rotifer (Notholca sp.). However, there was no evidence of grazing pressure on the microbial community. In common with most other Antarctic lakes, Ace Lake appears to be driven by ‘bottom‐up’ forces.
Dissolved organic matter and phosphorus leached from fresh and ‘terrestrially’ aged river red gum leaves: implications for assessing river–floodplain interactions
Authors: Baldwin D. S. 
Published: March 2003

1. The rates of leaching, speciation and bioavailability of dissolved organic matter (DOM) and dissolved phosphorus (P) leached from fresh leaves of the river redgum, Eucalyptus camaldulensis Dehnh, were compared to those from leaves which had been aged on the flood plain for 5_months. The DOM and P leaching rates from microbially inhibited aged leaves were first‐order with respect to leaf quantity. The kinetics of DOM and P leaching from fresh leaves were more complex; DOM leaching from fresh leaves appeared to be self‐inhibitory, while P leaching from leaves was potentially enzymatically mediated.2. The speciation and microbial bioavailability of DOM from fresh and aged leaves were completely different. At lower leaf biomass, almost all the DOM from fresh leaves was utilized by an introduced microbial consortium; at higher biomass, microbial utilization appeared to be nutrient limited. Conversely, only about 30% of the DOM leached from aged leaves was utilized by the introduced microbial consortium during the course of the experiment. The difference in microbial utilization could be a result of changes in DOM speciation as a consequence of terrestrial ageing.3. Weak‐anion exchange chromatograms of microbially inhibited fresh leaf extracts showed numerous (unassigned) DOM peaks, most of which could be used by the microbial consortium present. The weak‐anion exchange chromatograms of sterile aged leaves showed only three broad peaks and a number of smaller spikes. Only one of the broad peaks could be utilized by the microbial consortium.4. Phosphorus speciation was also determined by weak‐anion exchange chromatography. Most of the P leached from both fresh and aged leaves was free orthophosphate, and therefore, readily available. Two organic‐P species leached from microbially inhibited fresh leaves were also found to be readily available to the microbiota.
The importance of physical habitat assessment for evaluating river health
Authors: Maddock Ian 
Published: March 2003

Summary1. Physical habitat is the living space of instream biota; it is a spatially and temporally dynamic entity determined by the interaction of the structural features of the channel and the hydrological regime.2. This paper reviews the need for physical habitat assessment and the range of physical habitat assessment methods that have been developed in recent years. These methods are needed for assessing improvements made by fishery enhancement and river restoration procedures, and as an intrinsic element of setting environmental flows using instream flow methods. Consequently, the assessment methods must be able to evaluate physical habitat over a range of scales varying from the broad river segment scale (up to hundreds of kilometres) down to the microhabitat level (a few centimetres).3. Rapid assessment methods involve reconnaissance level surveys (such as the habitat mapping approach) identifying, mapping and measuring key habitat features over long stretches of river in a relatively short space of time. More complex appraisals, such as the Physical Habitat Simulation System (PHABSIM), require more detailed information on microhabitat variations with flow.4. Key research issues relating to physical habitat evaluation lie in deciding which levels of detail are appropriate for worthwhile yet cost‐effective assessment, and in determining those features that are biologically important and hence can be considered habitat features rather than simple geomorphic features.5. The development of new technologies particularly relating to survey methods should help improve the speed and level of detail attainable by physical habitat assessments. These methods will provide the necessary information required for the development of the two‐and three‐dimensional physical and hydraulic habitat models.6. A better understanding of the ways in which the spatial and temporal dynamics of physical habitat determine stream health, and how these elements can be incorporated into assessment methods, remains a key research goal.
The effects of disturbance events on phytoplankton community structure in a small temperate reservoir
Authors: Barbiero R. P. , James W. F. , Barko J. W. 
Published: March 2003

1 The effects of disturbances, in the form of storm events, on phytoplankton community structure were examined over the course of four years in Eau Galle Reservoir, Wisconsin, USA.2 Disturbances consistently brought about significant, but highly transient, increases in apparent phytoplankton species richness. It is likely that these resulted from temporary increases in the biomass of previously undetected rare species.3 Substantial shifts in community dominance were confined to large, early season events, and were seldom long‐lived. Later ‘climax’ communities were highly resistant to any changes in dominance, even when increases in species richness occurred.4 Regardless of when they occurred, disturbances tended to favour species from a narrow range of the successional sequence.
Bacterial production measured by leucine and thymidine incorporation rates in French lakes
Authors: Petit Muriel , Servais Pierre , Lavandier Pierre 
Published: March 2003

1. Production of heterotrophic bacterioplankton was estimated monthly by the tritiated thymidine and leucine incorporation methods during the draining and filling of the mesotrophic Lake Pareloup (over a 2.5‐years sampling program).2. Rates of 3H‐leucine (leu) and 3H‐thymidine (thy DNA) incorporation generally paralleled each other but the ratio of leu/thy DNA incorporation rates was higher for the draining period (34.5 mean) than during and after filling (11.5 mean).3. After draining, the highest ratios were observed during periods of low temperature and low bacterial specific activity, while DNA labeling by 3H‐thymidine was reduced. However, bacterial production estimates obtained by 3H‐leucine (BPL) and 3H‐thymidine (BPT) incorporation methods were generally well correlated and the average BPL/BPT ratio was equal to 0.78.4. In addition, both methods were applied during a diel cycle in three lakes of different trophic status. An increase of leu/thy DNA incorporation rates was noted from the oligotrophic to the eutrophic system. In the absence of Cyanobacteria, BPL and BPT values were quite concordant on average.5. In situations of unbalanced growth, BPL and BPT values can diverge but when considered over a sufficient period of time they were found to be in agreement.
Variation in growth of the detritivore‐shredder Sericostoma personatum (Trichoptera)
Authors: Friberg Nikolai , Jacobsen Dean 
Published: March 2003

1. We investigated the growth of the detritivore‐shredder Sericostoma personatum by feeding groups of larvae on a fresh macrophyte, Potamogeton perfoliatus, conditioned sitka spruce needles, Picea sitchensis, conditioned alder leaves, Alnus glutinosa, conditioned ash leaves, Fraxinus excelsior, and a fresh filamentous green alga, Microspora sp. A sixth treatment group of larvae was fasted.2. The nitrogen content of the food items ranged from 1.4% dry weight (DW) for Picea needles to 4.4% DW for Microspora filaments. Consumption of the various food items by Sericostoma differed significantly, being highest for Picea, and lowest for Potamogeton and Microspora.3. The instantaneous growth rate ranged from −1.3% DW day−1 in the fasting group to 0.75% DW day−1 in the Alnus group. The growth rate of larvae fed on Alnus, Fraxinus and Microspora was similar, and significantly higher than that of the other three groups. An increase in the size of larval cases followed the same pattern as larval growth, although with less variation between food items.4. Larvae fed on Microspora exhibited the greatest increase in fat content, while that of the larvae fed on Picea and those in the fasting group decreased. The gross growth efficiency (G/I%) of Sericostoma (larva + case) ranged from 2% when fed on Picea to 34% when fed on Microspora. Consumption was significantly correlated with the nutrient content of food items, whereas G/I% and growth rate were only weakly related to food quality.5. The growth of Sericostoma varies with diet and the food items sustaining highest growth rate are not necessarily the ‘typical’ shredder food resources.
Landscape spatial patterns in freshwater snail assemblages across Northern Highland catchments
Authors: Lewis David Bruce , Magnuson JohN. J. 
Published: March 2003

1. Limnologists and landscape ecologists have illustrated how the spatial position of a lake in a landscape influences many of its properties, from the physical to the social. Taking a community ecology perspective, we investigated whether freshwater gastropod assemblages respond to lake landscape position.2. We determined: (a) whether there is any spatial pattern among lakes in either the species richness or composition of gastropod assemblages; (b) the form of any spatial pattern; and (c) if any explanatory variables (e.g. dispersal corridors and limiting local conditions) show a similar pattern.3. In three different hydrological catchments, snail species richness increased from isolated highland lakes to stream‐connected lowland lakes, probably reflecting increased colonization potential and less limiting local factors for lowland drainage lakes. Catchments appear to differ from one another with regard to relative species abundance, both in terms of macrophyte‐associated snail fauna and snails from all habitats aggregated. One or more historical events, such as chance dispersal, may have produced this pattern. Taken together, these results suggest that within‐catchment constraints produce repeated gradients in species richness, regardless of what species composition persists in the catchment.
Role of dissolved organic carbon in the attenuation of photosynthetically active and ultraviolet radiation in Adirondack lakes
Authors: Bukaveckas Paul A. , Robbins‐Forbes Marise 
Published: March 2003

1. We surveyed eighty‐five lakes located in the Adirondack Mountain Region of New York State, U.S.A., to characterize the attenuation of photosynthetically active (PAR) and ultraviolet radiation (UVR) in relation to dissolved organic carbon (DOC) concentrations and pH. Attenuation of PAR was quantified in situ. Attenuation was also inferred by measuring the light absorption of filtered lake water samples at wavelengths (300, 340 and 440 nm) representing UV‐B, UV‐A and PAR.2. Substantial variation in transparency was observed among lakes in this region. Attenuation depths (z1%) for PAR ranged from 0.5 to greater than 20 m, while inferred values for UV‐B and UV‐A ranged from a few centimetres to > 5 m. Median values of UV‐A penetration (0.75 m) and UV‐B penetration (0.45 m) corresponded to 11% (UV‐A) and 6% (UV‐B) of lake maximum depth.3. Much of the variation in PAR and UVR attenuation was explained by differences in lake DOC. Univariate power models based solely on DOC accounted for 85% (PAR), 90% (UV‐A) and 91% (UV‐B) of the variation in absorption.4. Attenuation and absorption coefficients were generally lower for recently acidified lakes compared to acidic and circumneutral lakes which have not undergone recent acidification. However, differences among these three groups of lakes were not statistically significant. Our results suggest that the effects of acidification on the optical properties of a regional population of lakes, even in an area experiencing widespread acidification, are relatively subtle in comparison with other factors contributing to inter‐lake variability.5. The presence of near‐shore wetlands is probably a key factor influencing regional variability in DOC and light climate among Adirondack lakes. Temporal variability in climatic factors influencing wetland DOC production and export may mask more subtle influences on lake DOC associated with anthropogenic acidification.
Spatial variation in density, mean size and physiological condition of the holarctic amphipod Diporeia spp. in Lake Michigan
Authors: Nalepa Thomas F. , Hartson David J. , Buchanan Jennifer , Cavaletto Joann F. , Lang Gregory A. , Lozano Stephen J. 
Published: March 2003

Summary

We examined spatial patterns in population characteristics (density, biomass, mean body length) and physiological condition (lipid content, length‐weight) of the amphipod Diporeia spp. in Lake Michigan by collecting samples at up to 85 sites in late summer 1994 and 1995. Variables were examined relative to water depth and three lake regions: south, central and north. Most major river systems are found in the south, and this region is more nutrient‐enriched compared to the north.
Over all sites, mean density was 5240‐2, biomass was 4.1g dry wt m‐2, and mean body length was 5 mm. While maximum densities were related to depth, with a peak at 30–70 m, greatest densities occurred on the west side of the lake, and low densities were found in the south‐east, north‐east and lower Green Bay. High densities in the west probably resulted from upwelling, and reduced densities in the south‐east may reflect food competition with Dreissena polymorpha (zebra mussel).
Lipid content, weight per unit length, and mean length declined with increased water depth, but depth‐related trends were most evident in the south. Overall, mean lipid content and weight per unit length were significantly lower in the south (16.6% dry wt, 0.59 mg at 5 mm body length) compared to the north (23.7% dry wt, 0.78 mg at 5 mm body length). These regional differences may have resulted from greater diatom availability in the north and competition from D. polymorpha in the south. Triacylglycerols and phospholipids were the dominant lipid classes in all three regions. Although the mean proportion of triacylglycerols, the energy‐storage lipid, was lower in the south than in the north, regional differences in proportions of lipid classes were not significant.
Mean lipid content and weight per unit length of Diporeia in the south were lower than values found in the late 1980s prior to the establishment of Dreissena. Mean lipid content of mature individuals is now at levels considered a minimum for successful reproduction.