bluuebunny/crossref_metadata_2025_split huggingface dataset:
Environmental factors influencing chlorophyll v. nutrient relationships in lakes
Authors: STAUFFER ROBERT E. 
Published: May 2006

SUMMARY.
1. A model relating log chlorophyll a concentration to log epilimnetic total phosphorus (TP) concentration was re‐examined based on: (a) comparative and temporal studies of four stratifying Wisconsin and other highly eutrophic temperate lakes; (b) comparative summer lake surveys from Iowa and Alberta.2. Although P‐limited, deeper lakes with long hydraulic residence times and low external and internal nutrient loading in summer had summer chlorophyll a yields below model predictions based on spring and summer epilimnetic TP concentrations.3. For lakes with summer epilimnetic TP between 30 and 80 mg m−3, chlorophyll a concentrations exceeded model predictions based on summer TP. This relationship held even for Lake Delavan, Wisconsin, where the ratio of available N to P was unfavourably low during spring turnover, and where the trans‐thermocline N:P flux ratio was sub‐optimal for algal needs in early summer.4. With increasing summer TP concentrations and/or increasing epilimnetic circulation depth (>5m), chlorophyll a concentrations fell below model predictions—independent of the potential for N‐limitation. This plateauing in chlorophyll a response occurred at lower epilimnetic TP content (<c. 400 mg m−2) in lakes with elevated non‐algal light extinction coefficients. Using Tailing's algorithm for the‘column compensation point’ (algal photosynthesis = algal respiration over diel cycle), light limitation best explains this fall‐off in chlorophyll a yield.5. The failure of the Dillon & Rigler (1974) spring TP v. summer chlorophyll a model for these Wisconsin lakes is unrelated to N‐limitation. Instead, it reflects internal adjustment in take TP in response to stratification and seasonal external P loading.
Movement patterns and ecology of Pteronarcys nymphs (Plecoptera)
Authors: FREILICH JEROME E. 
Published: May 2006

SUMMARY.
1. Individually tagged Pteronarcys californica (Newport) nymphs were caught and recaptured over a 3‐month period to determine their movement patterns and home range size. Sex/age structure, population density, and food habits (from gut contents) were also recorded. More than 1000 nymphs were tagged of which 256 (25%) were recaptured at least once. Tagged insects were confined to contiguous fast water, cobble riffles. Low velocity, silt‐bottomed pools acted as barriers.2. This stonefly has a 3‐year life cycle although only the two oldest nymphet size‐classes were tagged. Females were larger than males at all ages. The population sex ratio was skewed 60:40 towards females. Densities averaged 1.7 m−2±0.17 SE (range 0–19 m−2).3. Most movements were short, indicating that a majority of the stoneflies stayed within a few meters of their first capture point (mean 1.8 m downstream ±0.51 SE, range 44 m downstream to 40 m upstream). Significant patch size is a stream reach 24 m long that would contain 85% of the average individual's movements. Time between captures averaged 16 d ±0.734 SE (maximum 81 d). Eight individuals were notable for extremely rapid upstream movements ranging from 6 to 22 m d−1.4. Frequency of movements up and downstream differed significantly between the sexes. Pteronarcys distribution was clumped with certain quadrate representing‘zones of attraction.’The stoneflies moved rapidly between zones, then stayed many days in those areas. Movements differed significantly from random walk models.5. Guts contained 75% diatoms, 15% vascular plant material, and 8% animal remains. Females ate significantly more diatoms than males on a volumetric basis.
Immobilization of dissolved organic matter from groundwater discharging through the stream bed
Authors: FIEBIG DOUGLAS M. , LOCK MAURICE A. 
Published: May 2006

SUMMARY.
1. In laboratory experiments, 9.7–25.7% of dissolved organic carbon (DOC) in groundwater (at concentrations of 18.7–24.8 mg 1‐−1) was immobilized after perfusion through 8‐cm‐deep (22‐cm‐diameter) cores of stony stream‐bed substratum.2. This represented immobilization rates of 7.1–23.5 mg m−2 h−1 or, extrapolated across the year, potential immobilization rates within the stream bed of 62.2–205.9g m−2 yr−1. Actual rates in the entire stream bed were probably higher because perfusion through the experimental cores did not reduce groundwater DOC concentrations to levels measured in the adjacent stream.3. Natural concentrations of dissolved free amino acids (DFAAs) in groundwater were generally unchanged following perfusion through the cores, suggesting the maintenance of a dynamic equilibrium in their concentrations.4. Selective enrichments of amino acids in groundwater (up to 20‐fold) were entirely immobilized following perfusion, indicating their rapid retention and flux in this environment. Thus, immobilization of the bulk DOC in stream‐bed cores probably did not reflect net reductions in dissolved free, low‐molecular‐weight material, with higher molecular weight, more ‘refractory’ material being immobilized instead.5. We conclude that groundwater can contribute substantial amounts of DOC, both high and low molecular weight, to a stream ecosystem. The stream bed is the site at which much of this material could be initially immobilized and made available to the stream trophic structure.
Relative vulnerabilities of natural rotifer and ciliate communities to cladocerans: laboratory and field experiments
Authors: WICKHAM STEPHEN A. , GILBERT JOHN J. 
Published: May 2006

SUMMARY.
1. Two experiments with plankton communities from Storrs Pond (NH), one conducted in the laboratory and one in field enclosures, assessed the impact of different cladocerans on rotifers and ciliated protozoa.2. The smallest cladoceran, Bosmina longirostris, did not depress rotifer or ciliate growth rates while the intermediate sized dadoceran, Daphnia galeata mendotae, reduced ciliate growth rates in the enclosure experiment but had only a marginal effect in the jar experiment. D. galeata mendotae had no effect on any of the rotifers in either experiment.3. In both experiments the largest cladoceran, Daphniapulex, depressed the growth rates of ciliates and those rotifers known to be vulnerable to interference competition. Polyarthra vulgaris, previously shown to be resistant to cladoceran interference, was the only rotifer unaffected by D. pulex in the field experiment but was depressed by the much higher densities of this cladoceran in the laboratory experiment.4. Cladocerans did not affect phytoplankton or bacterioplankton abundance in either experiment. Therefore the mechanism most likely to be responsible for the suppressive effect of cladocerans on rotifers and ciliates in these experiments is direct mechanical interference or predation, rather than exploitative competition.
Within‐lake patterns in depth penetration of emergent vegetation
Authors: WEISNER STEFAN E.B. 
Published: May 2006

SUMMARY.
1. Within‐lake relations of wave exposure (WE), and substratum softness (cone penetration depth; CPD) and organic content (loss on ignition; LOI), to water depth penetration of the emergent vegetation (DPE) was investigated in seven eutrophic lakes in southern Sweden, ranging in area from 1 to 46km2.2. There was a positive relationship between WE and DPE within lakes. This relationship, however, only occurred for sites with relatively soft substrata, for which CPD and LOI were negatively related to both WE and DPE.3. Analysis of aerial photographs revealed that expansion of the emergent vegetation towards open water, or recession from open water, was not related to wave exposure or water depth, except in one lake where expansion mainly occurred at high exposures.4. For relatively static vegetation on soft substrata, regressions with CPD°.5 explained 62–88% of the within‐lake variation of DPE. These regressions did not differ among lakes. Expanding and recessing vegetation were significantly dislocated towards shallower and deeper water, respectively, than predicted from the regression models for static vegetation.5. Phragmites australis dominated at the lakeward edge of the emergent vegetation, followed in frequency by Typha angustifolia. More broad‐leaved species were generally restricted to shallow water and very soft substrata.6. The results suggest that changes in the distribution of emergent vegetation in moderately wave exposed eutrophic lakes can be predicted largely from substratum character and water depth.
The photosynthetic and growth rate responses of two freshwater angiosperms in lakes of different trophic status: responses to light and dissolved inorganic carbon
Authors: RATTRAY M. R. , HOWARD‐WILLIAMS C. , BROWN J. M. A. 
Published: May 2006

SUMMARY 1. Two rooted freshwater macrophytes (Lagarosiphon major (Ridley) Moss; Myriophyllum triphyllum Orchard) were grown in two lakes of differing trophic status on sediments collected from an eutrophic lake. In the two experiments (summer and winter) in the oligotrophic lake (Lake Taupo, New Zealand), the relative growth rates of both species were approximately double those recorded in the experiments in the eutrophic take (Lake Rotorua, New Zealand). These growth responses occurred even though the light and temperature regimes were similar at the experimental sites in both lakes and the concentrations of inorganic nutrients were higher in the eutrophic lake water.2. Dissolved inorganic carbon (DIC) analysis of both lake waters indicated that the oligotrophic water had approximately 10‐fold more DIC than the eutrophic water. This corresponded, at natural pH, to a 2‐fold higher concentration of free‐CO2 in the oligotrophic lake water (49 μM) than in the eutrophic lake water (23 μM). Photosynthetic experiments demonstrated that the maximum rates of photosynthesis were 2.46 and 2.25‐fold higher in L. major and M. triphyllum, respectively, when the shoots were incubated in Lake Taupo water at Lake Taupo levels of free‐CO2 relative to Lake Rotorua water at Lake Rotorua levels of free‐CO2.3. It is concluded that these differences in photosynthetic rates would lead approximately to a 2‐fold difference in growth rate, thus explaining the growth responses observed in the field experiments.
The effect of the water‐lily beetle, Galerucella nymphaeae, on leaf production and leaf longevity of the yellow water‐lily, Nuphar lutea
Authors: KOUKI JARI 
Published: May 2006

SUMMARY.
1. The effect of the water‐lily beetle, Galerucella (=Pyrrhalta) nymphaeae (L.), (Coleoptera, Chrysomelidae), on the leaf production and leaf longevity of the yellow water‐lily, Nuphar lutea (=N. luteum) (L.) Sibth. & Sm., was studied experimentally in southern Finland during one growth season.2. Twelve cages, each containing a single rosette of the water‐lily, were established in the lake during May. Two treatments were randomly applied to cages: (i) control (herbivory not allowed), and (ii) fifty beetles added at the beginning of the season. Leaves were marked individually and the production of new leaves was followed until October.3. In both treatments the production of floating leaves continued until the end of August but declined towards the end of summer. Herbivory did not affect the number of leaves produced, i.e. the plants did not compensate for the loss of leaves.4. Leaf longevity was reduced dramatically (up to —60%) when herbivores were present. Leaves that emerged during the most intense period of larval growth had a life‐span one‐third of that of the control group.
Microhabitats and diel downstream migration of young grayling (Thymallus thymallm L.)
Authors: BARDONNET AGNÈS , GAUDIN PHILIPPE , PERSAT* HENRI 
Published: May 2006

SUMMARY.
1, Microhabitats chosen by young grayling (Thymallus thymallus L.) were investigated by electrofishing. The first feeding habitat was marginal areas where water velocity did not exceed 15 cms−1. Fry fed on drift in the first 10 cm of the water column below the surface. This location was very stable during the first weeks of growth (mid‐April to mid‐May). When they were 3–3.5 cm long, fry began using benthic areas and gradually moved away from the banks towards the channel.2. A downstream migration was noted from the beginning of emergence (mid‐April) to the end of May. This mainly nocturnal movement involved all fish sizes and caused a complete removal of young‐of‐the‐year by June from the spawning tributary.
Pesticides as chemical agents inducing helmet formation in Daphnia ambigua
Authors: HANAZATO TAKAYUKI 
Published: May 2006

SUMMARY.
1. Daphnia ambigua was exposed to harmful concentrations of pesticides (six insecticides, two herbicides, one fungicide) for 10 h from the final embryonic stage to the first instar, and effects on morphology were investigated.2. The animals developed helmets at the second instar after exposure to the insecticides, but did not show the same response when exposed to the herbicides and the fungicide.3. Some stimuli due to the insecticides on the nervous system of the animals may switch on the formation of the helmet, an antipredator morphology, which originally evolved as a response to chemicals released by predators.4. It is suggested that a range of chemicals other than the predator/prey kairomone can induce the helmet formation in Daphnia.
The influence of chemistry and habitat features on the microcrustacea of some upland Welsh streams
Authors: RUNDLE S.D. , ORMEROD S.J. 
Published: May 2006

SUMMARY.
1. Microcrustaceans were sampled during September 1990 from three microhabitats (margins, stony riffles and gravel) at thirteen stream sites in mid‐Wales.2. Patterns in the distribution, abundance and community structure of microcrustacean taxa were related to stream chemistry, physiography, substratum composition and marginal habitat structure. Patterns of distribution between microhabitats were also assessed.3. Chemical variables were the strongest correlates with microcrustacean parameters. Total numbers of microcrustaceans and harpacticoid copepods were reduced at sites with high aluminium concentrations, and ostracods were scarce or absent at the most acidic sites. In contrast, cyclopoid copepods were more abundant and species rich at low pH.4. Microcrustacean communities were most species rich at sites with a high percentage cover of macrophytes on the substratum. Cladoceran species richness and abundance, and the abundance of several microcrustacean species, were also positively correlated with percentage macrophyte cover.5. Three site groupings produced by TWINSPAN classification were primarily related to percentage macrophyte cover and marginal habitat structure, with chemistry and land use also of importance.6. Total microcrustacean abundance was highest in margins, but of all the species, only the harpacticoid Bryocamptus cuspidatus showed a strong microhabitat preference.
Temporal and spatial patterns in the distribution and abundance of pico, nano and microphytoplankton in an upland lake
Authors: HAPPEY‐WOOD CHRISTINE M. 
Published: May 2006

SUMMARY.
1. An investigation of the seasonal and depth distribution of populations of autotrophic picoplankton (0.2–2 μm), nanophytoplankton (>2<20 μm) and larger microalgal plankton (>20μm) was carried out over 21/2 years, 1988–90, in Llyn Padarn, a mesotrophic upland lake in North Wales.2. Cell numbers of picophytoplankton ranged from <102 to >106 cells cm−3. Maximum numbers of nanoplankton were c. 104 cells cm−3 and the greatest abundance of microalgal plankton, diatoms, reached 12 × 103 cells cm−3.3. Three types of picoalgae were distinguished: coccoid to oval Synechococcus—Synechocystis, the rod‐shaped Synchecococcus capitatus Bailey‐Watts & Komárek and Chlorella minutissima Fott & Nováková, with maximum numbers of 1.2 × 106, 37.8 × 103 and 44.1 × 103 cells cm−3, respectively.4. Picophytoplankton exhibited periods of exponential growth: the first in spring, and the second in August—September with an intervening population minimum in early to midsummer. Specific rates of population increase for picophytoplankton were low, with minimum apparent generation times of 3.8 days in summer 1989.5. Nanophytoplankton included seven species of phytoflagellates and two non‐motile species. These algae were present for about 10 months in each year exhibiting a fluctuation in population density of 102−‐103 cells cm−3.6. There were spring and autumn maxima in chlorophyll a concentrations in the lake water corresponding to the growth of planktonic diatoms. Maximum total biomass concentration was 35 mg m−3 chlorophyll a, whereas pico, nano and microphytoplankton had individual maxima of 7.7, 8.4 and 31.0 mg m−3 chlorophyll a, respectively. Picophytoplankton often contributed > 60% of the total algal chlorophyll a in the epilimnion.7. The growth patterns and seasonal periodicities of the three size‐categories of planktonic algae in Llyn Padarn were distinct. Picophytoplankton persist throughout much of the year with periods of very low abundance, < 100 cells cm−3, occurring in winter and midsummer. Thus for much of the year, there was a large inoculum of these cells in the lake to initiate growth leading to the population maxima in spring and late summer. Nanoplankton populations, a diverse assemblage, fluctuated in numbers over the period February–November; no population decline in midsummer comparable to picophytoplankton was observed. The larger microphyloplankton exhibited classical seasonal periodicity, namely diatom growth in spring and late summer–autumn with growth of large‐celled chlorophytes in the intervening summer period.
Vegetation and seed‐bank relationships on a lakeshore
Authors: GRELSSON GUNNEL , NILSSON CHRISTER 
Published: May 2006

SUMMARY.
Possible convergence in species richness and species composition between the (standing) vegetation and soil seed bank was studied along gradients of wave exposure, estimated as soil organic matter content, on five levels of a shore of a river‐lake in northern Sweden.
Species with seeds having little natural ability to float were most common in the vegetation, whereas species with seeds capable of prolonged floating were most abundant in the seed bank. Species richness in the vegetation and seed bank varied with wave exposure in the same way. Species richness decreased with exposure in both communities at the upper three levels but did not vary with exposure at the lower levels.
Floristic similarity between the vegetation and seed bank was 0.25 (Sørensen's index of similarity) for the entire flora. The variation in floristic similarity between communities did not differ between levels. Floristic similarity per sample plot increased with wave exposure.
Temporal variations of trace metals in aquatic insects
Authors: HARE LANDIS , CAMPBELL PETER G.C. 
Published: May 2006

SUMMARY1. Temporal fluctuations were measured in the concentrations of the trace metals cadmium (Cd), copper (Cu) and zinc (Zn) in six insect taxa collected from the same sites in a temperate zone lake over a 14‐month period. The consequences of temporal changes in insect contaminant concentrations for biomonitoring studies are assessed.2. Significant temporal fluctuations in the concentrations of the three metals were measured in almost all of the insect taxa studied. In no case was there a greater than sixfold change in the concentration of a trace metal over the course of the year. The extent of the fluctuations was generally greater for CD, a non‐essential metal, than for the essential micronutrients Cu or Zn.3. Temporal fluctuations in CD concentrations appeared to follow a seasonal periodicity for most taxa. Minima were measured during the winter period in the megalopteranSialisspp. and in the dipteran taxaChaoborus punctipennis, Glyptotendipessp., andProcladiusspp., whereas a maximum was measured in the mayflyHexagenia Hmbataduring the same season. In general, temporal fluctuations in Cu and Zn concentrations were less seasonal in character than were those of Cd.4. For some of the taxon—metal combinations studied, temporal fluctuations in metal concentrations could be ignored in biomonitoring studies, whereas in other cases a temporal window of minimum variability should be chosen for the collection of organisms from different sites.
Variation in genetic structure among populations of the caddisfly Helicopsyche borealis from three streams in northern California, U.S.A.
Authors: JACKSON JOHN K. , RESH VINCENT H. 
Published: May 2006

SUMMARY1. Allozyme electrophoresis was used to describe the genetic structure of Helicopsyche borealis caddisflies collected from three sites in each of three streams in northern California, U.S.A.: the Rice Fork of the Eel River; Big Sulphur Creek; and Alameda Creek. Between 7 and 11km separated adjacent sites within these three streams. Helicopsyche borealis from three additional streams in eastern North America (Christiana Creek, Indiana; Byrd's Mill Creek, Oklahoma; Susquehanna River, Pennsylvania) were also analysed electrophoretically to address taxonomic questions that arose during the study.2. Four genetically distinct groups of individuals were identified (i.e. Helicopsyche types A, B, C, and D). Lack of interbreeding between sympatric groups (as evidenced by fixed allelic differences) and large genetic differences (mean Nei's genetic distances = 0.396–0.693) indicate that these four groups of Helicopsyche were actually reproductively isolated species rather than genetic variants of a single species.3. Occurrence of Helicopsyche type A at multiple sites permitted an analysis of spatial variation in genetic structure. Within a drainage basin, small differences in allele frequencies were observed among sites in the Rice Fork and Big Sulphur Creek, but not in Alameda Creek. Larger genetic differences were found among sites in separate drainage basins. Genetic distances (Nei's) between Helicopsyche type A from California and from eastern North America sites (mean = 0.236) were greater than interpopulation differences commonly observed for insects, which suggests that Helicopsyche type A from California may represent a different species than Helicopsyche type A from eastern North America.4. Geographical and taxonomic differences observed in this study underscore the importance of understanding both population structure and genetic relationships among populations in the design and interpretation of stream faunal studies.
Contribution of benthic blue‐green algal recruitment to lake populations and phosphorus translocation
Authors: BARBIERO R.P. , WELCH E.B. 
Published: May 2006

SUMMARY1. A two‐season investigation was undertaken to determine the contribution of benthic recruitment to the population development of several species of blue‐green algae.2. Gloevtrichia echinulata populations were shown to be heavily subsidized by benthic recruitment, deriving on average 40% of their planktonic colonies from the benthos.3. Benthic recruitment of Aphanizomenon flos‐aquae, Anabaena flos‐aquae and a second Anabaena species contributed less than 2% to planktonic increases, while Microcystis aeruginosa recruitment was negligible.4. Phosphorus translocation via migrating G. echinulata accounted for most of the phosphorus (P) in the planktonic colonies, and constituted a significant portion of the internal loading of the lake.5. Estimated P translocation via Aph. flos‐aquae was relatively minor, although there was evidence of luxury uptake in the benthos.