bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diets and food consumption rates of pelagic fish in Lake Malawi, Africa
Authors: ALLISON E.H. , IRVINE K. , THOMPSON A.B. , NGATUNGA B.P. 
Published: August 2010

SUMMARYStudies of diel feeding periodicity, rates of food consumption and diet composition of pelagic fish were undertaken to resolve the dispute regarding the existence of a vacant niche for a pelagic zooplanktivore in Lake Malawi.Six species of zooplanktivore were abundant in the offshore pelagic zone, these were:Diplotaxodon limnothrissa, D.‘bigeye’,Rhamphochromis longicepsandCopadichromis quadrimaculatus(all haplochromine cichlids),Synodontis njassae(Mochokidae) andEngraulicypris sardella(Cyprinidae). The main piscivores were cichlids of the genusRhamphochromis.All cichlids were daytime feeders; some showed peaks in feeding activity at dawn and dusk that were related to vertical migration patterns of their prey.Synodontis njassaewas able to feed throughout the day, but fed most actively at night.Food consumption: biomass ratios (Q/Byr‐1) calculated from diel stomach contents data were 5.87–7.13 forD. limnothrissa, 12.79 forD.‘bigeye’, 4.20–24.7 forR. longicepsand 6.45 forS. njassae.AnnualQ/Bratios for other species, which ranged from 4.74 to 9.28, were obtained from an empirical model relating food consumption to fish morphology. Published estimates were used forE. sardellaandOpsaridium microcephalum(Cyprinidae). An estimate of total prey consumption by the pelagic fish population was obtained fromQ/Bratios and fish biomass estimates from acoustic surveys covering the entire offshore pelagic zone of the lake (24 000 km2).Diplotaxodon limnothrissa, R. longicepsandC. quadrimaculatushad a broad range of diets, with the ability to switch from crustacean zooplankton to larvae and pupae ofChaoborus edulis(Diptera) or larval and juvenileE. sardella. Diplotaxodon‘bigeye’ andS. njassaefed almost exclusively on fourth‐instar larvae and pupae ofC. edulis. Engraulicypris sardellafed mainly on crustacean zooplankton. The main prey of the large piscivorousRhamphochromisspecies wereDiplotaxodonspp. andE. sardella.The fish community consumed only 3% of estimated crustacean zooplankton production directly. Predation pressure was intense (> 80% of estimated production consumed by predators) on late instars of the zooplanktivorousC. edulislarvae and onE. sardellalarvae.Rhamphochomisspp. consumed 22–43% of estimated production of the zooplankton‐eating fishes.Although many members of the fish community do not feed directly on crustacean zooplankton, so that the food‐chain supporting fish production involves an extra trophic level, it is considered that the endemic fish community is well adapted to feeding on the low‐density prey in the pelagic zone, and that there is no vacant feeding niche.
Interannual variability in phytoplankton biomass and species composition in a subtropical reservoir
Authors: HARRIS GRAHAM P. , BAXTER GRAHAM 
Published: August 2010

SUMMARY

The interannual variability of the dominant phytoplankton populations is described in a subtropical reservoir in Queensland using weekly data for a 16‐year period between 1978 and 1994. North Pine Dam, Brisbane, is in an area characterized by strong interannual variability in rainfall. This variability is linked to El Nino Southern Oscillation (ENSO) events. Between 1978 and 1994 periods of drought (during strong ENSO events) were interspersed by periods of flooding rains. Rainfall on the catchment and temperature and oxygen within the dam showed strong 40‐day periodicities which also varied in strength interannually in response to ENSO events. Similar patterns of fluctuations in the 40‐day periodicity have been found elsewhere in SE Australia. Seasonal cycles of stratification in the dam were a function of both hydrographic and hydrological events. Intermittent rain storms caused partial turnovers and large outflows. As much as 90% of the dam volume was exchanged in a single flood event.
The dominant phytoplankton species were similar to those frequently found in tropical and subtropical lakes and reservoirs. The phytoplankton community switched between cyanobacterial blooms (Cylindrospermopsis, Microcystis) during drought and falling water levels and diatom blooms (Aulacoseira) in response to inflows and seasonal turnovers. There appeared to be a subtle interaction between inflows, water column stability, the periodic overturns and the occurrence of the dominant species. All the dominant species showed long periods (2–4 years) of exponential increase or decrease superimposed on top of the seasonal fluctuations in abundance. These patterns of abundance led to marked interannual variability in the phytoplankton biomass. Climate variability had a major impact on the seasonal and interannual changes of the dominant phytoplankton species.
Phytoplankton biomass tended to be depressed for about 3 months after individual storm events but the data also displayed long‐term lag effects (2–4 years) which destroyed any significant correlation between water residence time and biomass. Summer maxima of biomass dominated by cyanobacteria disappeared between 1985 and 1990 and were replaced by smaller winter peaks. The data presented here are not capable of unequivocally identifying the precise reason for these longer‐term effects. Because of the implications for water quality management in subtropical and tropical reservoirs they warrant further study.
The influence of stream invertebrate composition at neighbouring sites on local assemblage composition
Authors: SANDERSON R. A. , EYRE M. D. , RUSHTON S. P. 
Published: August 2010

Summary1. The composition of freshwater invertebrate assemblages at a location is determined by a range of physico‐chemical and biotic factors in the local environment, as well as larger‐scale spatial factors such as sources of recruits. We assessed the relative importance of the species composition of local neighbourhoods and proximal environmental factors on the composition of invertebrate assemblages.2. Macroinvertebrate assemblages were sampled at 188 running‐water sites in the catchment of the River Rede, north‐east England. A total of 176 species were recorded.3. Environmental data, in the form of 13 biotic and abiotic measurements that described stream physical structure, aquatic vegetation and water characteristics, were recorded for each site. Detrended correspondence analysis was then used to simplify nine of these stream environmental variables to create an index of stream structure.4. The species composition of the invertebrate assemblages was related to the environmental variables, using an information theoretic approach. The impact of the species composition of neighbouring sites on each site was determined using Moran's I and autoregressive modelling techniques.5. Species composition was primarily associated with water pH and stream structure. The importance of the species composition of neighbouring sites in determining local species assemblages differed markedly between taxa. The autoregressive component was low for Coleoptera, intermediate for Trichoptera and Plecoptera, and high for Ephemeroptera.6. We hypothesise that the observed differences in the autoregressive component amongst these orders reflects variation in their dispersal abilities from neighbouring sites.
Release rates and potential fates of nitrogen and phosphorus from sediments in a eutrophic reservoir
Authors: NOWLIN WESTON H. , EVARTS JENNIFER L. , VANNI MICHAEL J. 
Published: August 2010

Summary1. Nutrients released from lake sediments can influence water column nutrient concentrations and planktonic productivity. We examined sediment nutrient release [soluble reactive phosphorus (SRP) and ammonia (NH)] at two sites in a eutrophic reservoir (Acton Lake, OH, U.S.A.) that differed in physical mixing conditions (a thermally stratified and an unstratified site).2. Sediment nutrient release rates were estimated with three methods: sediment core incubations, seasonal in situ hypolimnetic accumulation and a published regression model that predicted sediment phosphorous (P) release rate from sediment P concentration. All three methods were applied to the deeper stratified site in the reservoir; however, we used only sediment core incubations to estimate SRP and NH release rates at the shallow unstratified site because of the lack of thermal stratification. We also compared the total P concentration (TPS) of sediments and the concentration of P in various sediment fractions at both sites.3. Anoxic sediments at the stratified site released SRP at rates more than an order of magnitude greater than oxic sediments at the shallow unstratified site. However, P accumulated in the hypolimnion at much lower rates than predicted by sediment core incubations. In contrast, NH was released at similar rates at both sites and accumulated in the hypolimnion at close to the expected rate, indicating that P was ‘lost’ from the hypolimnion through biogeochemical pathways for P, such as precipitation with inorganic material or biological uptake and sedimentation.4. TPS was significantly greater at the deeper stratified site and organically bound P accounted for >50% of TPS at both sites.5. We examined the magnitude of SRP fluxes into the study reservoir in 1996 by comparing the mean summer daily SRP fluxes from anaerobic sediments, aerobic sediments, stream inflows and gizzard shad excretion. While the SRP release from anaerobic sediments was high, we hypothesise that little of this SRP gained access to the epilimnion in mid‐summer. SRP flux to the reservoir from aerobic sediments was less than from gizzard shad excretion and streams. Large interannual variability in thermocline stability, gizzard shad biomass and stream discharge volumes, will affect SRP loading rates from different sources in different years. Therefore, construction of P budgets for different years should account for interannual variation in these parameters.
Diversity in the influence of temperature on the growth rates of freshwater algae, and its ecological relevance
Authors: BUTTERWICK C. , HEANEY S. I. , TALLING J. F. 
Published: August 2010

Summary1. Growth rates of seven species of planktonic algae were determined in culture over a range of temperature from 2 to 35 °C. Additional observations on growth and viability were made for 13 species in the temperature range 20–35 °C.2. There was a wide range of growth rates between species at their optimal temperatures, from 1.7 divisions day−1 (Asterionella formosa) to 0.3 divisions day−1 (Ceratium furcoides).3. There were considerable differences between species for growth at low and high temperature. Certain algae, including the diatom A. formosa and the flagellates Cryptomonas marssonii, Dinobryon divergens and Eudorina unicocca var. unicocca, had growth rates of 0.4 divisions day−1 or more at 5 °C. The cyanophyte Tychonema (formerly Oscillatoria) bourrellyi, the xanthophyte Tribonema sp., the desmid Staurastrum cingulum and the large dinoflagellate C. furcoides grew poorly or not at all at this temperature. All 21 species tested could grow at 25 °C, but many – including most of the diatoms, some cyanophytes, and all the flagellates – failed to grow persistently at 30 °C. Only Aphanizomenon flos‐aquae survived with moderate increase at 35 °C, a lethal temperature for the other species.4. The applicability was considered of proposed quantitative formulations of the rate‐temperature relationship. Simple exponential relationships applied only to very limited lower ranges of temperature. The relationship proposed by Bĕlehrádek was a better fit over a wider temperature range, but still excluded rate‐decline at high temperature.5. The interspecific differences found are of potential significance for restrictions in natural distributions associated with season, altitude (especially above 500 m) and latitude.
Responses of a beaded Arctic stream to short‐term N and P fertilisation
Authors: BENSTEAD JONATHAN P. , DEEGAN LINDA A. , PETERSON BRUCE J. , HURYN ALEXANDER D. , BOWDEN WILLIAM B. , SUBERKROPP KELLER , BUZBY KAREN M. , GREEN ADRIAN C. , VACCA JAY A. 
Published: August 2010

Summary1. Oligotrophic Arctic streams are likely to be sensitive to changes in hydrology and nutrient inputs predicted to occur as a consequence of future climate and land use change. To investigate the potential consequences of nutrient enrichment for low‐order Arctic streams, we added ammonium‐N and phosphorous to a second‐order beaded, tundra stream on Alaska's north slope. We measured responses in nutrient chemistry, chlorophyll a standing crop, and in the breakdown and macroinvertebrate colonisation of leaf litter over a 38‐day summer period.2. During the addition, nutrient concentrations immediately downstream of the dripper averaged 6.4 μm ammonium‐N and 0.45 μm soluble reactive P. Concentrations upstream of the dripper averaged 0.54 μm ammonium‐N and 0.03 μm soluble reactive P. Uptake of both nutrients was rapid. Concentrations were reduced on average to 28% (ammonium‐N) and 15% (inorganic P) of maximum values within 1500 m. Standing crops of chlorophyll a on standardised samplers were significantly higher by the end of the experiment. Breakdown rates of senescent willow (Salix sp.) and sedge (Carex sp.) litter and associated fungal biomass were also significantly increased by nutrient addition.3. Fertilisation resulted in four‐ to sevenfold higher macroinvertebrate abundance and two‐ to fourfold higher macroinvertebrate biomass in litter bags, as well as an increase in late‐summer body mass of larval Nemoura stoneflies.4. Our results are consistent with those of similar studies of larger streams in the high‐Arctic region. Based on our short‐term experiment, increased inputs of nutrients into these ecosystems, whether caused by climate change or more local disturbance, are likely to have profound ecological consequences. Longer‐term effects of enrichment, and their interaction with other components of future change in climate or land use, are more difficult to assess.
Flood‐mediated dispersal versus hatching: early recolonisation strategies of copepods in floodplain ponds
Authors: FRISCH DAGMAR , THRELKELD STEPHEN T. 
Published: August 2010

Summary1. We explored the quantitative contribution of two alternative recolonisation strategies by a combination of experimental and field data from the Little Tallahatchie floodplain (Mississippi, U.S.A.). In this area, several floods of short duration occur in winter and spring. During floods, lentic and lotic waterbodies of different size are connected for a limited period.2. Shortly before the onset of the flood season we collected sediment samples from six temporary ponds. The emergence of seven cyclopoid species was recorded from the experimentally flooded sediments and was quantified over a 4‐week period. Water samples were taken in the same ponds after flooding, from which eight further species were recorded and quantified.3. The contribution of flood‐dispersed individuals was variable among flooded ponds (between 38 and 94%), but numbers of flood‐dispersed colonists did not differ significantly from those of hatching individuals in flooded ponds. Our results demonstrate the equal importance of both hydrological connections and hatching from dormant stages as pathways for recolonisation by copepods if ponds are hydrologically connected.4. The significance of recolonisation by hatching individuals in disconnected waterbodies was apparent in an isolated temporary pond that was exclusively recolonised by cyclopoid copepods emerging from the sediment.
Leaf litter breakdown, microbial respiration and shredder production in metal‐polluted streams
Authors: Carlisle Daren M. , Clements William H. 
Published: August 2010

Summary1. If species disproportionately influence ecosystem functioning and also differ in their sensitivities to environmental conditions, the selective removal of species by anthropogenic stressors may lead to strong effects on ecosystem processes. We evaluated whether these circumstances held for several Colorado, U.S.A. streams stressed by Zn.2. Benthic invertebrates and chemistry were sampled in five second–third order streams for 1 year. Study streams differed in dissolved metal concentrations, but were otherwise similar in chemical and physical characteristics. Secondary production of leaf‐shredding insects was estimated using the increment summation and size‐frequency methods. Leaf litter breakdown rates were estimated by retrieving litter‐bags over a 171 day period. Microbial activity on leaf litter was measured in the laboratory using changes in oxygen concentration over a 48 h incubation period.3. Dissolved Zn concentrations varied eightfold among two reference and three polluted streams. Total secondary production of shredders was negatively associated with metal contamination. Secondary production in reference streams was dominated by Taenionema pallidum. Results of previous studies and the current investigation demonstrate that this shredder is highly sensitive to metals in Colorado headwater streams. Leaf litter breakdown rates were similar between reference streams and declined significantly in the polluted streams. Microbial respiration at the most contaminated site was significantly lower than at reference sites.4. Our results supported the hypothesis that some shredder species contribute disproportionately to leaf litter breakdown. Furthermore, the functionally dominant taxon was also the most sensitive to metal contamination. We conclude that leaf litter breakdown in our study streams lacked functional redundancy and was therefore highly sensitive to contaminant‐induced alterations in community structure. We argue for the necessity of simultaneously measuring community structure and ecosystem function in anthropogenically stressed ecosystems.
CD1a down‐regulation in primary invasive ductal breast carcinoma may predict regional lymph node invasion and patient outcome
Authors: La Rocca G , Anzalone R , Corrao S , Magno F , Rappa F , Marasà S , Czarnecka A M , Marasà L , Sergi C , Zummo G , Cappello F 
Published: August 2010

Aims:  CD1a is a molecule belonging to the highly conserved group of CD1 proteins. Its expression in dendritic cells is related to the presentation of tumour‐derived glycolipid antigens to T cells and, consequently, the development of a successful antitumour response. The aim was to investigate the presence of CD1a+ cells in both primary tumours and lymph nodes (LN) of a series of 35 invasive ductal carcinomas by both immunohistochemistry and reverse transcription‐polymerase chain reaction.Methods and results:  CD1a antigen was more expressed in N0 than N1 breast cancer (P < 0.0001) in both primary lesions and LN metastases and correlated positively and significantly with oestrogen (ER) (P = 0.0025) and progesterone (P = 0.0226) receptor (PR) status, as well as CD4+ and CD8+ T‐lymphocyte infiltration.Conclusions:  This is the first report to show a link between CD1a+ mononuclear cells in breast cancer and in paired LN metastases. The positive and significant correlations between the number of CD1a+ cells and positivity of the primary tumour for ER and PR suggest a possible role for CD1a as a prognostic marker for breast cancer, raising the possibility that hormone receptor‐positive breast cancer patients may have a better prognosis in the presence of greater dendritic cell infiltration.
Overexpression of prostate stem cell antigen is associated with gestational trophoblastic neoplasia
Authors: Feng H C , Tsao S W , Ngan H Y S , Xue W C , Kwan H‐S , Siu M K Y , Liao X‐Y , Wong E , Cheung A N Y 
Published: August 2010

Aims:  Hydatidiform mole (HM) is the most common type of gestational trophoblastic disease. A proportion of patients with HM develop gestational trophoblastic neoplasia (GTN) requiring chemotherapy. The aim was to identify differentially expressed genes that are associated with development of GTN.Methods and results:  Using cDNA microarray, differential expression of prostate stem cell antigen (PSCA) was identified in HMs that developed GTN compared with those that spontaneously regressed. Significant overexpression of PSCA RNA (P = 0.037) and protein (P < 0.05) in aggressive HM was verified by real‐time polymerase chain reaction (PCR) and immunohistochemical analysis in 10 first‐trimester placentas, 36 HM that subsequently regressed and 11 HM that developed GTN. A high level of PSCA expression was also found in three choriocarcinomas and three placental site trophoblastic tumours. A positive correlation was observed between PSCA expression and proliferation and apoptotic indices as assessed by Ki67 (P = 0.01), mcm7 (P = 0.001) and M30 (P = 0.016), as well as p53 (P < 0.01), p21WAF1/CIP1 (P < 0.01) and mdm2 (P = 0.002) expression.Conclusions:  Overexpression of PSCA is associated with development of GTN in HM. PSCA probably plays a role in the regulation of cell growth through p53‐related signaling pathways.
Recurrent aphthous ulceration in children—a review
Authors: FIELD E. ANNE , BROOKES VANITA , TYLDESLEY WILLIAM R. 
Published: August 2010

Summary. The clinical presentation or recurrent aphthous ulceration in children is described together with current views on the aetiology and pathogenesis of the disease. Factors that predispose to this type of oral ulceration are discussed and a rational approach to the management of recurrent aphthous ulceration in children is proposed.Resumé.Les auteurs font la description de la présentation clinique de l'ulcération aphthteuse périodique chez les enfants et des opinions courantes sur l'aétiologie et al pathogénésie de cette maladie. Les facteurs prédisposant à ce genre d'ulcération orale sont discutés et les auteurs proposant un méthode raisonné pour traiter l'ulcération aphteuse périodique enfantine.Zusammenfassung.Dieser Artikel beschreibt klinisches Bild der chronisch rezidivierenden Mundaphthen in Kindern und die derzeitige Sicht auf die Ätiologie und Pathogenese dieser Krankheit. Die Autoren befassen sich mit den prädisponierenden Faktoren für diese Art von Mundulzeration und schlagen eine razionale Methode fur die Behandlung von rezidivierenden Aphthen in Kinder vor.Resumen.La presentación clinica de úlceras aftosas recurrentes en niños es descrita junto con los actuales puntos de vista sobre la etiología y patogénesis de dicha enfermedad. Los factores que predisponen a este tipo de ulceración oral son discutidos y los autores proponen un método racional a seguir ante la presentación de úlceras aftosas recurrentes en niños.