bluuebunny/crossref_metadata_2025_split huggingface dataset:
Recent advances in understanding the circulation and hydrography of the East China Sea
Authors: Lie Heung‐Jae , Cho Cheol‐Ho 
Published: March 2003

AbstractThe physical oceanography of the East China Sea (ECS) has been studied extensively through comprehensive observing programmes conducted in the 1990s, allowing clarification of the major oceanographic processes involved in establishing the hydrography and circulation. An overview of the general circulation and hydrography in the ECS is given here, mainly based on the new observational results and with special attention to the Kuroshio bifurcation north‐east of Taiwan and south‐west of Kyushu and the major currents in the outer continental shelf. A new schematic circulation pattern of the ECS is sketched using these observations. The oceanographic conditions and fisheries environments of the ECS are not only seasonally variable because of the response of the basin to the seasonally varying atmospheric conditions, but also spatially and temporally complicated because of the wide spectrum of phenomena that coexist with various scales.
Identification of Atlantic bluefin tuna (Thunnus thynnus) stocks from putative nurseries using otolith chemistry
Authors: Rooker Jay R. , Secor David H. , Zdanowicz Vincent S. , De Metrio Gregorio , Relini Lidia Orsi 
Published: March 2003

AbstractChemical signatures in the otoliths of teleost fishes represent natural tags that may reflect differences in the chemical and physical characteristics of an individuals' environment. Otolith chemistry of Atlantic bluefin tuna (Thunnus thynnus) was quantified to assess the feasibility of using these natural tags to discriminate juveniles (age 0 and age 1) from putative nurseries. A suite of six elements (Li, Mg, Ca, Mn, Sr and Ba) was measured in whole otoliths using solution‐based inductively coupled plasma mass spectrometry. Otolith chemistry of age‐1 T. thynnus collected from the two primary nurseries in the Mediterranean Sea and western Atlantic Ocean differed significantly, with a cross‐validated classification accuracy of 85%. Spatial and temporal variation in otolith chemistry was evaluated for age‐0 T. thynnus collected from three nurseries within the Mediterranean Sea: Alboran Sea (Spain), Ligurian Sea (northern Italy), and Tyrrhenian Sea (southern Italy). Distinct differences in otolith chemistry were detected among Mediterranean nurseries and classification accuracies ranged from 62 to 80%. Interannual trends in otolith chemistry were observed between year classes of age‐0 T. thynnus in the Alboran Sea; however, no differences were detected between year classes in the Tyrrhenian Sea. Age‐0 and age‐1 T. thynnus collected from the same region (Ligurian Sea) were also compared and distinct differences in otolith chemistry were observed, indicating ontogenetic shifts in habitat or elemental discrimination. Findings suggest that otolith chemistry of juvenile T. thynnus from different nurseries are distinct and chemical signatures show some degree of temporal persistence, indicating the technique has considerable potential for use in future assessments of population connectivity and stock structure of T. thynnus.
Trophic interactions in rockpool food webs: regulation of zooplankton and phytoplankton byNotonectaandDaphnia
Authors: Arnér Marie , Koivisto Sanna , Norberg Jon , Kautsky Nils 
Published: March 2003

We studied trophic interactions in experimental rockpools with three different food web structures: phytoplankton and small‐bodied zooplankton; phytoplankton, small‐bodied zooplankton and Daphnia; and phytoplankton, small‐bodied zooplankton, Daphnia and Notonecta. Nutrients, primary productivity, chlorophyll a and zooplankton species composition and biomass were measured over eight weeks.2. Daphnia had a negative impact on other zooplankton and reduced the phytoplankton biomass and primary productivity. In the absence of Daphnia, small‐bodied zooplankton species were abundant, in particular cyclopoid copepods. Concentrations of dissolved nutrients were lower and the standing crop of primary producers was higher when Daphnia was absent.3. The presence of the invertebrate predator Notonecta produced a top‐down effect which was similar to that reported for planktivorous fish, i.e. a selective reduction of daphnids followed by an increase of small‐bodied zooplankton species and phytoplankton biomass.4. The study showed that consumer regulation of Daphnia by Notonecta and of algae by Daphnia are important, but also demonstrated that trophic level biomasses were controlled by a combination of predation and resource limitation.
Dispersal and recruitment ofTasiagma ciliata(Trichoptera: Tasimiidae) in rainforest streams, south‐eastern Australia
Authors: Hughes Jane M. , Bunn Stuart E. , Hurwood David A. , Cleary Cath 
Published: March 2003

1. This study examined genetic variation within and among populations of the caddis fly Tasiagma ciliata (Tasimiidae: Trichoptera) from rainforest streams in south‐east Queensland, Australia.2. Very low levels of genetic differentiation at large spatial scales, between subcatchments and between catchments, indicated that dispersal by the winged adults is widespread. However, significant genetic differentiation at the smallest spatial scale examined, within reaches in a single stream, suggested limited movement by larvae within streams.3. A patchy distribution of deviations from Hardy–Weinberg equilibrium and differences in patterns among allozyme loci suggested that populations in particular reaches were the result of only a few matings.4. These results are surprising, given the large numbers of larvae present within a single reach. We suggest that stochastic effects of recruitment may underlie much of the spatial and temporal variation in population numbers in these rainforest streams.
Locomotion in Elliptio complanata (Mollusca: Unionidae): a reproductive function?
Authors: Amyot Jean‐pierre , Downing John A. 
Published: March 2003

1. Temporal variation in the spatial aggregation of the freshwater bivalve Elliptio complanata was studied at a sandy site in an oligotrophic lake over three years.2. Epibenthic populations varied in aggregation over the season bringing animals closer together during spawning. The complex link between movements of mussels and aggregation dynamics suggested a functional reproductive role for horizontal locomotion of unionid mussels in lentic systems.3. The rate of locomotion did not differ systematically among males, females or hermaphrodites, and was independent of gravidity, whether compared during spawning, after spawning or throughout the ice‐free season.4. In spite of the high reproductive output of mussels and the energetic cost of locomotion, no relationship was found between the rate of movement of spawning gravid mussels and reproductive output.
Estimating age and growth in long‐lived temperate freshwater crayfish using lipofuscin
Authors: Belchier Mark , Edsman Lennart , Sheehy Matt R. J. , Shelton Peter M. J. 
Published: March 2003

1. In ecological studies on freshwater crayfish, determination of basic population parameters is often complicated by the lack of a suitable age estimation method.2. Previously, lipofuscin age pigment in the olfactory lobe cell masses (OLCM) of short‐lived tropical crayfish has been used for accurate age determination. Here we present the first test of this method on a longer‐lived, temperate species, the signal crayfish, Pacifastacus leniusculus.3. Confocal fluorescence microscopy and image analysis of histological sections were used to quantify OLCM lipofuscin in a reference sample of Swedish P. leniusculus from several known year‐classes, reared under naturally variable temperature conditions. Lipofuscin concentration was linearly associated with age (r2 = 92.4%) and produced much more accurate age estimates than conventional body size‐based procedures.4. A model derived from the crayfish of known‐age was used to estimate the ages of wild P. leniusculus from an English stream. The relationship between lipofuscin‐estimated age and carapace length suggested relatively slow growth in this wild population, consistent with a high population density and severe competition. The analysis also extended the known longevity of P. leniusculus to approximately 16 years.5. The lipofuscin method for determining age and growth may be widely applicable to freshwater crayfish, with probable further potential both within and outside the Crustacea.
In situ studies on heart rate and locomotor activity in the freshwater crayfish, Astacus astacus (L.) in relation to natural fluctuations in temperature and light intensity
Authors: Bojsen Berit H. , Witthøfft Hanne , Styrishave Bjarne , Andersen Ole 
Published: March 2003

1. By the aid of a computer technique, the in situ variations in heart rate and locomotor activity were recorded continuously for 7 days in sixteen individuals of the crayfish, Astacus astacus (Linnaeus 1758), in association with natural changes in water temperature and light intensity.2. All sixteen crayfish investigated were found to express circadian rhythmicity in heart rate with a periodicity of ≈ 24 h. For 88% of the animals investigated, rhythmicity was significant (P < 0.05). Ninety‐three per cent of the crayfish showed circadian rhythmicity in locomotor activity with a 24 ± 2 h periodicity and, for 67% of the animals, this rhythmicity was significant (P < 0.05). In general, the expression of circadian rhythms was associated with nocturnal behaviour, heart rates and locomotor activity levels being higher at night than by day.3. A positive correlation was observed between heart rate and locomotor activity. Temperature and light intensity exerted positive and negative influences on heart rate in A. astacus, respectively.4. In the first experiment, 84% of the variation in heart rate could be explained by the changes in locomotor activity, temperature and light intensity. In the second experiment 35% of the variation in the heart rate was explained using these parameters.
Macrophyte growth and sediment phosphorus and nitrogen in a Canadian prairie river
Authors: Carr Geneviève M. 
Published: March 2003

1. The role of sediment phosphorus (P) and nitrogen (N) in regulating growth of rooted macrophytes in a Canadian prairie river was investigated by means of in situ observations and artificial stream fertilization experiments.2. Biomass and percentage cover of rooted macrophytes in the South Saskatchewan River increased downstream of a municipal sewage treatment plant, with maximum abundance occurring between 25 and 100 km downstream of the outfall. Biomass in the river was related to sediment P but not N concentration, although sites of maximum biomass did not coincide with sites of maximum sediment P concentration.3. Artificial stream experiments revealed that while biomass was unaffected by addition of N to the sediment, it was enhanced by the addition of P to sediments, and further enhanced with the addition of N and P together, indicating a primarily P‐limited system, with secondary N limitation when P is in excess.4. Macrophyte biomass increased linearly with increasing sediment P concentration in the artificial streams, and tissue P concentration peaked at ≈ 400 μg g–1. Biomass did not respond to increasing sediment N concentration, and only a weak relationship was observed between tissue N and sediment N, with maximum tissue N corresponding to ≈ 140 μg g–1 sediment exchangeable N.5. A lack of concurrence between the sediment P concentration producing maximum biomass and tissue P concentration in situ vs. under experimental conditions indicates that other environmental factors have an important role in regulating macrophyte growth in rivers. Thus, while nutrient control may be one element in a river macrophyte control programme, a holistic ecosystem approach should be adopted to account for the other factors that may affect the growth of rooted plants.
Biological assessment of freshwater ecosystems using a reference condition approach: comparing predicted and actual benthic invertebrate communities in Yukon streams
Authors: Bailey Robert C. , Kennedy Matthew G. , Dervish Michael Z. , Taylor And Ronald M. 
Published: March 2003

1. The reference condition approach to bioassessment is based on comparing a biological community found at a test site to the range of communities observed at a set of reference sites. A community descriptor (e.g. number of taxa) is estimated for the test site. If the value of the descriptor falls outside of a given boundary, or biocriterion, from the distribution of the descriptors for the reference sites, the test site fails.2. The sensitivity of the reference condition approach can be increased by modelling and explaining variation in the community descriptor among the reference sites, and then using the predictive model to refine the expectation of the descriptor’s value at a test site.3. This study applied the reference condition approach, with predictive modelling, to the bioassessment, using benthic macroinvertebrate (BMI) communities, of streams exposed to placer gold mining effluent in central Yukon Territory, Canada. The major changes to the stream caused by mining are increased turbidity and metal concentrations.4. Among reference sites sampled from 1993 to 1995, a predictive model using year of sampling and simple geographical characteristics (distance to source of the stream, upstream catchment area, altitude, two‐way interactions) explained over half of the variation in each of five BMI community descriptors including richness (number of families), Simpson’s diversity, Simpson’s equitability, family biotic index and Bray–Curtis distance to the median reference community.5. Biocriteria (other than Bray–Curtis distance to the median community) based on the predictive models failed a far greater proportion of sites currently exposed to placer mining (50–100%) than biocriteria not based on predictive models (7–71%). A similar increase in the sensitivity of the bioassessment was seen when evaluating sites previously exposed to placer mining effluent. The simplest, most sensitivebioassessment of the effects of placer gold mining effluent on stream ecosystemsused richness (number of families) of the BMI community together with a predictivemodel.
Effects of buried leaf litter and vertical hydrologic exchange on hyporheic water chemistry and fauna in a gravel‐bed river in northern New South Wales, Australia
Authors: Boulton Andrew J. , Foster J. G. 
Published: March 2003

1. Large amounts of coarse particulate organic matter (CPOM) are buried in the sand and gravel beds of many rivers during spates. The effects of these patchily distributed resources on hyporheic invertebrates and water chemistry are poorly understood. Buried CPOM may provide local ‘hot‐spots’ of food for hyporheic detritivores and their predators, alter nutrient supply to nearby sediment biofilms, and generate habitat for some invertebrates.2. To examine potential short‐term effects on hyporheic water chemistry, nutrient concentrations and invertebrate assemblage composition, leaf packs were buried in downwelling (surface water infiltrating the hyporheic zone) and upwelling (hyporheic water emerging to the surface) zones at two sites along a gravel‐bed river in northern New South Wales. At one site, pits were excavated to simulate leaf burial (procedural control) and plastic ‘leaves’ were buried to test whether invertebrates might respond to leaves as refuges rather than food. Hyporheic CPOM, sediment size fractions, and interstitial silt content were also quantified at these sites.3. Dry weights of naturally buried CPOM (leaf litter and wood fragments) varied substantially (0.6–71.7 g L–1 sediment). Amounts of CPOM did not differ between up‐ vs. downwelling zones or between sites. Hyporheic dissolved oxygen saturation was generally high (> 75%), and was lower in upwelling zones. The hyporheos was dominated taxonomically by water mites (≈ 20 species), whereas small oligochaetes were most abundant (40% of total abundance). Tiny instars of elmid beetle larvae and leptophlebiid mayfly nymphs were also common. Before experimental manipulation, faunal composition differed between up‐ and downwelling zones. In upwelling zones, bathynellaceans and blind peracarids were found, whereas small individuals of the surface benthos were common in samples from downwelling zones. This validated stratification of the experiment across zones of hydrologic exchange.4. Twenty days after leaf burial, there was no effect of the treatments at either site on changes in most variables, including mean numbers of taxa and individuals per sample. Similarly, changes in faunal composition of the hyporheos in the treatments paralleled those in the controls except for a weak response in the buried leaves treatment in the upwelling zone at site 1. Artificially buried leaf litter does not seem to influence hyporheic water chemistry or fauna at these two sites. It is probable that naturally buried leaf litter is swiftly processed soon after entrainment and that repeating this experiment immediately after a flood may yield different results.
Aquatic bryophytes in Himalayan streams: testing a distribution model in a highly heterogeneous environment
Authors: Suren A. M. , Ormerod S. J. 
Published: March 2003

Summary1. Aquatic bryophytes were sampled from 108 streams spanning over 3000 m of altitude in four regions of Nepal. Richness, cover and community composition were related to physicochemistry using multiple regression, DECORANA ordination and TWINSPAN. The performance of a hierarchically scaled descriptive model, developed in New Zealand for predicting bryophyte distribution, was examined in this highly heterogeneous Himalayan region.2. Community composition and cover varied highly significantly with altitude, streambed stability and alkalinity, with evidence of effects of riparian land use on bryophyte cover. Cover was greatest in streams at low to middle altitudes with steep slopes (> 15°), high stability and low conductivity (< 60 μS cm–1), where communities were dominated by two Isopterygium spp., two Philonotis spp., Mnium punctatum and Lejeuneaceae.3. Richness, by contrast, increased significantly but weakly at high altitude and moderate stability, where streams were dominated by Eurynchium praelongum, Rhynchostegium spp., Fissidens grandifrons and Hygroamblystegium spp. Richness and cover were lowest in unstable streams at the lowest altitude, where no single taxon was consistently most abundant.4. Although these results were similar to those in the descriptive model developed for bryophytes in New Zealand, subtle differences were apparent. Substrate size, although influencing the presence of bryophytes in New Zealand streams, appeared to be unimportant in Nepal. By contrast, streambed stability was more important in Nepal than New Zealand, perhaps reflecting pronounced monsoonal floods, and subsequent increased frequency of bed movement in the former. A suggested habitat template indicates that large plant size and vegetative reproduction may be responsible for the widespread distribution of some species, even into unstable Himalayan streams.
Perspectives and predictions on the microbial ecology of the hyporheic zone
Authors: Storey R. G. , Fulthorpe R. R. , Williams D. D. 
Published: March 2003

1. Studies of hyporheic microbial ecology have suggested an important role for hyporheic microbial processes in stream ecosystem functioning. Using evidence from microbial communities in other aquatic habitats, some predictions are made concerning the diversity of microbial types and microbial processes likely to occur in the hyporheic zone, and the relative importance of these various types to the hyporheic ecosystem.2. It is predicted that the biofilm growth form of interstitial micro‐organisms will create a variety of microniches, allowing coexistence of a great diversity of microbial types, and promoting the activity of some otherwise poor competitors. It is further predicted that the confluence of reduced groundwaters and aerobic surface waters will favour chemolithotrophic processes in the hyporheic zone, but that these will contribute significantly to hyporheic production only if surface water is very low in dissolved organic carbon, or the groundwater is extremely reduced, such as by the influence of riparian wetlands. A variety of anaerobic respiratory pathways, such as nitrate, ferric ion, sulphate and even methanogenic respiration will be employed in the hyporheic zone, with biofilm dynamics permitting these to occur even in aerobic sediments. Anaerobic pathways may account for a significant proportion of total hyporheic organic matter mineralization.3. The role of fungi in hyporheic dynamics is, as yet, almost completely unstudied. However, it is expected that they will be important in breaking down buried particulate organic matter (POM), which may account for a large proportion of total stream POM.4. Physicochemical conditions in hyporheic sediments appear to be highly heterogeneous, and this heterogeneity may be very important in the cycling of certain nutrients, especially nitrogen, which involves a series of steps requiring different conditions.5. Various new techniques are now available by which biofilm dynamics and in situ microbial processes may be measured. Studies are recommended of intact microbial communities both at the microscale of the biofilm and at the scale of the heterogeneities occurring in hyporheic sediments. Studies are needed that measure actual rates of microbial processes under in situ conditions.
Competitive abilities and related strategies in four aquatic plant species from an intermediately disturbed habitat
Authors: Greulich S. , Bornette G. 
Published: March 2003

Summary1. High species richness in disturbed habitats is commonly attributed to the coexistence of species with diverse competitive abilities and, more generally, to the coexistence of different plant strategies sensu Grime (1977, 1979). The present study tests this assumption for the case of intermediately disturbed, species‐rich macrophyte habitats.2. Four species, Sparganium emersum, Hippuris vulgaris, Groenlandia densa and Luronium natans that coexist solely in one flood‐disturbed, cut‐off channel of the Upper Rhone River (France) were selected for this study. Apart from this common, disturbed habitat, they presented different distribution patterns within the floodplain. The present study aimed to establish both a hierarchical ranking of their competitive abilities and their respective strategies according to the C‐S‐R‐model.3. The study was carried out during one growth season in a de Wit experimental design with supplementary monitoring of growth characteristics. Whereas a clear ranking of species competitiveness could not be established, the experiment revealed differences in their traits and strategies.4. S. emersum possesses the traits of a competitor, whereas the other species present intermediate secondary strategies, with a C‐R‐strategy in G. densa, a C‐S‐strategy in H. vulgaris, and a C‐S‐R or S‐R‐strategy in L. natans. These strategies are well matched to the distribution of the species within the floodplain, since the distribution of S. emersum reaches far into weakly disturbed and undisturbed, and supposedly competition intensive sites, whereas Luronium occupies a habitat that is both disturbed and relatively nutrient‐poor. Only the presence of Hippuris in disturbed habitats seems not to correspond to the established strategy, but this might be explained by its need for only moderately intensive competition and by particularities of its regeneration strategy. The revealed differences in strategy may also make it possible to interpret the patchy pattern in vegetation cover within disturbed habitats.