bluuebunny/crossref_metadata_2025_split huggingface dataset:
Using diatoms to assess the biological condition of large rivers in Idaho (U.S.A.)
Authors: Fore Leska S. , Grafe Cynthia 
Published: March 2003

SUMMARY 1. Diatoms were collected from 49 sites located on 23 rivers and identified to species. We defined 26 attributes of the diatom assemblage on the basis of tolerance and intolerance, autecological guild, community structure, morphological guild and individual condition.2. We grouped sites into three geographical regions on the basis of altitude, land cover and use. Within each region, we tested for an association between diatom attributes and human disturbance.3. We selected nine attributes for inclusion in a multimetric index, the river diatom index (RDI): percentage of valves belonging to species sensitive to disturbance, percentage of valves belonging to species very tolerant of disturbance, eutrophic species richness, percentage of valves belonging to nitrogen heterotrophic species, percentage of valves belonging to polysaprobic species, alkaliphilic species richness, percentage of valves belonging to species that require high oxygen, percentage of valves belonging to very motile genera and percentage of deformed valves.4. The RDI was significantly correlated with measures of human disturbance made at the site (conductivity, percentage of fine sediments and number of human activities) and at the catchment level (percentage of urbanisation and agriculture in the upstream catchment).5. The percentage of the total variance of RDI related to transect location was very small (1%) compared with among‐site differences (73%) and time of sampling (26%). The RDI could reliably detect approximately three categories of biological condition based on annual monitoring and potentially more if sampling were restricted to the same month each year.
The balance between photosynthesis and grazing in Antarctic mixotrophic cryptophytes during summer
Authors: Marshall William , Laybourn‐Parry Johanna 
Published: March 2003

SUMMARY 1. Grazing and photosynthetic contributions to the carbon balance of planktonic, mixotrophic cryptophytes in Lakes Fryxell and Hoare in the Taylor Valley, Antarctica were measured during November and December 2000.2. The cryptophytes never became entirely photosynthetic, although carbon derived from grazing decreased in December. Individual grazing rates ranged between 5.28 and 10.08 bacteria cell−1 day−1 in Lake Fryxell and 0.36–11.76 bacteria cell−1 day−1 in Lake Hoare. Grazing rates varied temporally and with depth in the water column. In Lake Fryxell, which is a meromictic lake, highest grazing occurred just above the chemocline. Individual photosynthetic rates ranged from 0.23 to 1.35 pg C cell−1 h−1 in Lake Fryxell and 0.074 to 1.08 pg C cell−1 h−1 in Lake Hoare.3. Carbon acquisition by the cryptophyte community gained through grazing ranged between 8 and 31% during November in Lake Fryxell, dropping to between 2 and 24% in December. In Lake Hoare grazing contributed 12–21% of the community carbon budget in November and 1–28% in December. Around 4% of the carbon acquired from grazing and photosynthesis was remineralised through respiration.4. Mixotrophy is probably a major survival strategy for cryptophytes in the extreme lakes of the Dry Valleys, because perennial ice‐cover severely limits light penetration to the water column, whereas these phytoflagellates are not normally mixotrophic in lower latitude lakes. The evidence suggests that mixotrophy may be a mechanism for supplementing the carbon budget, as well as a means of acquiring nutrients for growth.
Preparation of phosphorus and carbohydrate microcapsules for manipulating dietary C : P ratio for aquatic suspension‐feeders
Authors: Kreeger Daniel A. , Kilham Susan S. , Lanka Sujani , Linder Alison 
Published: March 2003

SUMMARY 1. Dietary phosphorus can be limiting for aquatic animals such as suspension‐feeders. However, our understanding has been limited by the difficulty of manipulating dietary P without altering other aspects of food quality. We microencapsulated various forms of bioavailable P with carbohydrate to manipulate dietary C : P ratio for suspension‐feeders.2. Calcium phosphate, sodium hexametaphosphate, sodium tripolyphosphate and tetrasodium pyrophosphate were each mixed with a concentrated solution of a carbohydrate base (either maltodextrin or potato starch) and microencapsulated using an interfacial polymerisation technique. Each of the 10 types of capsules produced had a particle size ideal for suspension‐feeders (3–10 μm).3. Leakage rates were low (<12% of capsule weight per day). Relative enzymatic breakdown in vitro by carbohydrases (amylase or cellulase) was similar among the 10 capsule types and was always at least 15 times the comparable leakage rate.4. Release of dissolved P from enzyme‐treated capsules varied depending on capsule P content. Liberation of P from capsules prepared from 20% w/w sodium hexametaphosphate in maltodextrin (molar C : P = 1.8) was three times greater than all other types, and this combination appears most suitable as a dietary supplement for zooplankton.5. Although P content and capsule integrity were greatly influenced by choice of carbohydrate, choice of P compound, and the mixing ratio of the two, P‐rich artificial microparticles can be produced that have low leakiness, high digestibility, and a physical size suitable for aquatic suspension‐feeders. Therefore, microcapsules represent promising tools for manipulating dietary C : P for suspension feeders.
Modelling the impact of benthic filter‐feeders on the composition and biomass of river plankton
Authors: Descy J.‐P. , Everbecq E. , Gosselain V. , Viroux L. , Smitz J. S. 
Published: March 2003

SUMMARY 1. The POTAMON model [Everbecq E. et al. (2001) Water Research, 35, 901] has been used to simulate the effect of benthic bivalves (mainly Dreissena polymorpha) on the phytoplankton and zooplankton in a lowland Western European river (the Moselle). Here we use a modified version of the POTAMON model with five categories of phytoplankton (Stephanodiscus, Cyclotella‐like, large diatoms, Skeletonema and non‐siliceous algae) to model filter‐feeding effects of benthic bivalves in the Moselle. Zooplankton has been represented in the model by two categories, Brachionus‐like and Keratella‐like rotifers.2. According to density estimates from field surveys (Bachmann V. et al. (1995) Hydroécologie Appliquée, 7, 185, Bachmann V. & Usseglio‐Polatera P. (1999) Hydrobiologia, 410, 39), zebra mussel density varied among river stretches, and increased through the year to a maximum in summer. Dreissena filtration rates from the literature were used, and mussels have been assumed to feed on different phytoplankton categories (but less on large and filamentous diatoms) as well as on rotifers.3. The simulations suggest a significant impact of benthic filter‐feeders on potamoplankton and water quality in those stretches where the mussels are abundant, their impact being maximal in summer. Consequently, different plankton groups were not affected to the same extent, depending on their period of development and on indirect effects, such as predation by mussels on herbivorous zooplankton.4. A daily carbon balance for a typical summer shows the effect of benthic filter‐feeders on planktonic and benthic processes: the flux of organic matter to the bottom is greatly enhanced at high mussel density; conversely, production and breakdown of organic carbon in the water column are reduced. Mussel removal would drive the carbon balance of the river toward autotrophy only in the downstream stretches.
Behavioural fitness component effects of the alba polymorphism of Colias (Lepidoptera, Pieridae): resource and time budget analysis
Authors: Nielsen M. G. , Watt W. B. 
Published: March 2003

1. Alba, a white wing colour morph of butterflies of the genus Colias, makes fitness‐related changes at several levels of phenotypic organization: physiology, development and behaviour. Two sympatric species of Colias are studied, which differ greatly in their frequency of alba vs its sister yellow/orange morph. How resource and time constraints on Colias interact with the morphs’ different patterns of pupal resource allocation to alter the balance of the morphs’ fitness components in the two species is discussed. 2. These species, C. alexandra and C. scudderi, differ in melanin‐based solar energy absorption, in larval dietary richness and in local adult nectar resources. The two female morphs determine alternate thermal balance, internal resource allocation and behavioural effects in each species, thus changing the morphs’ time budgets and fitness‐component impacts between the species. In particular, female egg output differences between the morphs appears to reverse between species: alba fecundity is greater than yellow fecundity in C. scudderi, but alba is less than yellow in C. alexandra. 3. These differences are consistent with the large observed differences in alba frequency between the species. Some important questions about the selective regime maintaining a polymorphism here, rather than an alternation of monomorphisms, remain.
Effect of water‐borne zinc on osmoregulation in the freshwater amphipod Gammarus pulex (L.) from populations that differ in their sensitivity to metal stress
Authors: Spicer J. I. , Morritt D. , Maltby L. 
Published: March 2003

1. Although there is some evidence that exposure to heavy metals can disrupt osmoregulation in crustaceans, most studies have been carried out on relatively pollution‐tolerant, marine or estuarine species. Consequently the effects of water‐borne zinc (Zn) on osmoregulation by the freshwater amphipod, Gammarus pulex (L.), from two populations that differ in their heavy metal sensitivity, have been compared. 2.‘Clean’ site animals (Clowne, Derbyshire) exhibited a marked haemoconcentration (after 4 days at 37·0 μmol Zn l–1, 5 days at 18·2 μmol Zn l–1) shown by an increase in haemolymph osmotic pressure (OPh) and [Na+] and [K+]. However, after 5 days at 37·0 μmol Zn l–1, haemolymph of survivors exhibited an OPh significantly less than controls. ‘Contaminated’ site animals showed a reduction in OPh (but not ions) only after 5 days at 76·2 μmol Zn l–1. 3. There were differences in the threshold and nature of osmoregulatory response to Zn between animals from ‘clean’ and ‘contaminated’ sites, but only at concentrations in excess of those (a) known to affect growth and reproduction in ‘clean’ site animals and (b) occurring at the ‘contaminated’ site. Clearly population differences in physiological capacity and tolerance do exist but their ecological significance is unclear.
The establishment of fucoid zonation on algal‐dominated rocky shores: hypotheses derived from a simulation model
Authors: Johnson M. P. , Hawkins S. J. , Hartnoll R. G. , Norton T. A. 
Published: March 2003

1. A model was developed for the growth of intertidal algae with photosynthesis simulated both in air and in a tidal water column. Morphological data on dry mass per unit area and length–area relationships were used to separate the growth of different fucoid species. The relative growth rate of fronds at any height on the shore depended on a trade‐off between net photosynthetic performance and tolerance to desiccation. 2. The simulated zonation patterns and growth rates were consistent with those observed previously for Fucus spp. and Pelvetia canaliculata. 3. The simulated growth of Ascophyllum nodosum was always slower than for the other species. This species did not form its characteristic distribution zones in simulations without including further processes in the model. However, Ascophyllum collected from the field could be separated into upper and lower shore morphologies which formed separate zones when they were simulated in competition with each other. 4. Several hypotheses were proposed concerning the relative locations and sharpness of interspecies boundaries on the shore. Zonation patterns were relatively insensitive to changes in most model parameters except the desiccation rate.
Life span and dynamics of leaves of herbaceous perennials in high‐elevation environments: ‘news from the elephant’s leg’
Authors: Diemer M. 
Published: March 2003

1. Leaf life spans, determined as half‐lives, of 16 herbaceous perennial plant species from the aseasonal, tropical Andes at altitudes between 4000 and 4600 m were on average 193±19 days and thus two to three times greater than those of herbaceous perennials from the seasonal northern hemisphere. The duration of lamina expansion was positively correlated with life span. Growth was continuous all year round, but rates of leaf initiation in the high‐elevation tropics were lower than in the temperate zone. 2. Significant positive inter‐relationships were found between leaf life span and mass‐based foliar nitrogen concentration of Andean taxa. The correlation between life span and leaf mass per area (LMA) was marginally significant, while life span and area‐based foliar N content were unrelated. 3. Leaf traits of 46 Andean herbaceous perennials (forbs and graminoids), spanning an altitudinal range of 1500 m, indicated that the 16 taxa utilized for growth and leaf life span determinations were representative. For graminoids no altitudinal changes in LMA or foliar N were observed across species. However, in forbs LMA and area‐based foliar N increased significantly with altitude. No differences in leaf traits were observed between herbaceous rosette and cushion growth forms. 4. The Andean data set was used in conjunction with data from the temperate, subarctic and arctic zones to evaluate the significance of leaf life spans in herbaceous plants from a biogeographical perspective. Leaf life span declined significantly with increasing seasonality, expressed as latitude and duration of the annual growth period. Because temperature regimes are similar along this gradient during the respective growth periods (Diemer 1996), observed differences should be the result of variation in the day length and/or duration of the growing season. 5. Data on leaf life spans and leaf traits of herbaceous plants from contrasting latitudes were used to evaluate the validity of general inter‐relationships proposed by Reich (1993). The high correlation between LMA and life span observed in both data sets indicates that this relationship holds for various growth forms. On the other hand, the apportionment of mass‐based foliar N concentration in relation to life span appears to differ between herbaceous and woody growth forms.
Confirmation of soil‐feeding termites (Isoptera; Termitidae; Termitinae) in Australia using stable isotope ratios
Authors: Tayasu I. , Inoue T. , Miller L. R. , Sugimoto A. , Takeichi S. , Abe T. 
Published: March 2003

1. Carbon (δ13C) and nitrogen (δ15N) stable isotope ratios of termites (Isoptera) were examined in Darwin, northern Australia. It is suggested that the stable isotope technique, together with phylogenetics, is a useful tool to understand the evolution of functional groups in detritivores. 2. A high δ15N value was observed in the Termes‐Capritermes branch of the subfamily Termitinae and the genus Amitermes, two distinct taxonomic groups that evolved from wood‐feeding to soil‐feeding in Australia. Among eight Termes‐Capritermes branch species, only two species (Xylochomitermes melvillensis and Ephelotermes melachoma) were discernible as wood/soil interface feeders, the remaining six species analysed were soil‐feeders, where the diet preference was identified by using δ15N of workers. 3. The Termes‐Capritermes group in Australia contains both wood/soil interface feeders and soil‐feeders, whereas wood/soil interface feeders in Cameroon are from the Termes‐Capritermes branch while soil‐feeders are from Cubitermes group. The result confirmed that soil‐feeding forms evolved both in Australia and Africa, but from different phylogenetic groups.
Interaction between temperature and cadmium toxicity in the isopod Porcellio scaber
Authors: Abdel‐Lateif H. M. , Donker M. H. , Van Straalen N. M. 
Published: March 2003

1. Temperature has an important effect on all physiological processes in animals that rely on external sources of heat (ectotherms). In an attempt to elucidate the interaction between temperature and the response of ectotherms to heavy metals, a study was made of growth (increase of body mass) of the isopod Porcellio scaber under four constant temperature regimes (12, 16, 20, 24 °C), and four different exposures to cadmium (0·016, 0·071, 0·14 and 0·31 μmol g–1 in the diet), in a factorial experiment. 2. There were significant effects on growth rate for both cadmium and temperature, and the interaction between cadmium and temperature was also significant. The average growth rate per week increased with increasing temperature, but the results showed that when cadmium was present at concentrations higher than 0·071 μmol g–1, it disturbed the temperature‐induced growth enhancement. 3. There was a tendency for cadmium to be least toxic at intermediate temperature (16 °C), but the 50% and 10% effect concentrations in the diet, estimated by loglogistic curve fitting, did not significantly vary with temperature. The average values were EC50 = 0·330 μmol g–1 and EC10 = 0·041 μmol g–1. 4. The Arrhenius model was used to describe the temperature–growth rate relationship, and activation energies were estimated for each cadmium exposure. At the highest cadmium concentration the Arrhenius model did not describe the data very well. The lowest activation energy was observed at 0·14 μmol g–1. 5. Cadmium accumulation in isopods was linearly related to the cadmium concentration in food, for all temperature levels. The significant increase in cadmium concentration with temperature indicates that the effect of temperature on cadmium accumulation is stronger than its effect on body growth. As a whole the data illustrate the importance of taking temperature into account when conducting ecotoxicological studies with soil invertebrates.
Lineage‐dependent rates of evolutionary diversification: analysis of bivariate ellipses
Authors: Ricklefs R. E. , Nealen P. 
Published: March 2003

1.A method based on the calculation of major and minor axes of bivariate ellipses to estimate relative rates of evolutionary diversification of two traits is presented. The advantage of ellipse analysis over the more common allometric or regression approaches to variation in comparative data is that diversification of each trait is estimated relative to that of the other. This can reveal differences in the relative rates of diversification of two traits among sister groups or, through hierarchical analysis, over the history of a lineage.2.Equations are provided for calculating the size, shape and orientation of bivariate ellipses based on the variance–covariance matrix of the original data. Standard errors and biases of these parameters are also quantified.3.Applications of ellipse analysis to the relationship between egg size and incubation period in birds illustrate differences in the diversification of two traits between independent lineages. Nested analysis of covariance based on taxonomic levels further illustrates how relative rates of evolutionary diversification may vary through the history of a monophyletic group.4.A simple model incorporating both independent (special) and correlated (general) change in two traits shows how different shapes and orientations of bivariate ellipses can be produced by different rates of evolutionary diversification in special and general genetic factors.5.Ellipse analysis is a descriptive tool that can clarify patterns of diversification. It cannot distinguish differences in evolutionary responsiveness (phylogenetic constraint) from differences in the selective environment affecting the shape and orientation of the bivariate ellipse. It can, however, provide a more detailed characterization of trait evolution than other comparative methods, taking advantage of the additional information provided by the shape and, in some cases, the dimensions of the bivariate ellipse.
Effects of Free‐Air CO2 Enrichment (FACE) on experimental grassland communities
Authors: Norton L. R. , Firbank L. G. , Blum H. 
Published: March 2003

1. Experimental grassland communities (turves) were exposed to elevated (60 Pa) and ambient (35 Pa) CO2 partial pressures (pCO2) in a Free‐Air Carbon Dioxide Enrichment (FACE) experiment between 30 March 1995 and 4 July 1996. The vegetation was cut once during the experiment prior to the final harvest (harvest 2). 2. No significant treatment effects on total plant biomass at the whole turf level were detected, although biomass was typically about 25% higher under fumigation in year 1 and about 15% higher in year 2. 3. Biomass for two of the six sown species was significantly higher at harvest 2 than at harvest 1. There were no significant differences between individual species’ biomass under the two CO2 treatments at either harvest 1 or 2 or in terms of overall cumulative biomass. However, in four of the five sown species in both years biomass tended to be higher in the fumigated than in the control rings (Cerastium holosteiodes, Phleum pratense, Plantago lanceolata and Poa trivialis). In contrast, Lolium perenne showed increased biomass under the control treatment relative to the fumigated treatment in both years. Owing to the high variance both within and between rings for each of the two treatments the statistical power of most, but not all, of the analyses carried out was poor. 4. The relative proportions of each species in the turves under fumigated and control treatments was broadly similar after the first summer, with differences in the second year being mainly owing to the negative response of L. perenne to CO2 fumigation.
Effect of enhanced atmospheric CO2 on mycorrhizal colonization and phosphorus inflow in 10 herbaceous species of contrasting growth strategies
Authors: STADDON P. L. , GRAVES J. D. , FITTER A. H. 
Published: March 2003

1. Ten herbaceous species were grown over a 4‐month period under ambient (360 μmol mol–1) and elevated (610 μmol mol–1) atmospheric CO2 conditions. Plants were inoculated with the arbuscular mycorrhizal (AM) fungus Glomus mosseae and given a phosphorus (P) supply which was not immediately available to the plants. 2. Multiple harvests were taken in order to determine whether the effect of elevated CO2 on mycorrhizal colonization and phosphorus inflow was independent of its effect on plant growth. 3. All species grew faster under elevated CO2 and carbon partitioning was altered, generally in favour of the shoots. All species responded similarly to elevated CO2. 4. Elevated CO2 did not affect the percentage of root length colonized by AM fungi, but the total amount of colonized root length was increased, because the plants were bigger. 5. Elevated CO2 increased total P content, but had little or no effect on P concentration. At a given age, P inflow was stimulated by elevated CO2, but when root length was taken into account the CO2 effect disappeared. 6. In these host species there is no evidence for a direct effect of elevated CO2 on mycorrhizal functioning, because both internal mycorrhizal colonization and P inflow are unaffected. 7. Future research should concentrate on the potential for carbon flow to the soil via the external mycelial network.