bluuebunny/crossref_metadata_2025 huggingface dataset:
Internet‐supported sourcing of complex material
Authors: Kersten Wolfgang , Schroeder Kirsten A. , Schulte‐Bisping André
Published: February 2004

Currently, automotive original equipment manufacturers (OEMs) aim at developing Internet‐based methods to redesign their relationships with the suppliers. The majority of the manufacturers believe this to be a possibility to improve the relationships to their suppliers, especially regarding transparent cost‐structures. Suppliers on the other hand are very skeptical about methods in this area. Their fears of rising price pressure and potential losses of know‐how and competitive advantages are high. This article examines how strategic sourcing can be supported by Internet‐based methods. Thus, it tries to answer the question how the relationship between OEMs and suppliers will develop regarding the sourcing of complex material: will the Internet‐based relationships enhance collaboration or increase competition? An empirical study within the German automotive industry shows that the views of suppliers and OEMs differ substantially regarding the benefits and risks of an Internet‐based support of strategic sourcing. Hence, it seems that non‐technological problems are the main obstacles in the transition of these methods. It is evident that suppliers generally fear increased transparency within their structures in many different areas.
COVES: an e‐business case study in the engineering domain
Authors: Sindhu Emilda , Lee Alex , Mohamed Salim Shaik
Published: February 2004

The paper discusses how to succeed in the new economy by utilizing e‐business in transforming business processes and strategy. The Collaborative One‐Stop Virtual Engineering Services (COVES) portal provides users with collaborative engineering services for government agencies and private sectors involved in various areas like safety, health and environment. The portal helps in design through modeling and simulation over the Internet for the above sectors. The portal provides a Web‐based environment for tackling the above issues during the design of a factory via the use of e‐computational fluid dynamics. Besides the above, COVES has re‐engineered the traditional business processes associated with construction industry by integrating various enterprises. The portal also improves competitiveness by installing a strong culture of knowledge collaboration and increased accessibility to expensive high‐performance‐computing (HPC) resources and tools. The integrated inter‐enterprise workflow with various public and private parties has simplified the procedure and expedites building plan approvals.
Determinants of Canadian bilateral aid allocations: humanitarian, commercial or political?
Authors: Macdonald Ryan , Hoddinott John
Published: February 2004

Abstract.  In this paper we examine the determinants of the allocation of Canadian bilateral aid over the period 1984–2000. We draw on models of donor behaviour that allow us to incorporate humanitarian, commercial and political considerations – the ‘trinity of mixed motives’– that affect Canadian aid. We find that allocations are moderately altruistic. Recipient country human rights and membership in the Commonwealth and La Francophonie also affect aid flows. Most strikingly, our results suggest that Canadian aid flows became less altruistic over this period and commercial motives became increasingly important. JEL Classification: H50, O10
Lumpy consumer durables, market power, and endogenous business cycles
Authors: Krishna Kala , Yavas Cemile
Published: February 2004

Abstract.  In this paper we show that lumpy consumer durables and market power can generate endogenous cycles consistent with the facts. Past sales determine the current market size of durable goods. Larger past sales, ceteris paribus, thus naturally result in a smaller current market size and income. In this manner, the seeds of a downturn are sown in an upturn. JEL Classification: E32, E13
Sources of aggregate labour productivity growth in Canada and the United States
Authors: Tang Jianmin , Wang Weimin
Published: February 2004

Abstract.  In this paper we propose a decomposition technique to examine the sources of industrial contribution to aggregate labour productivity growth. We show that in terms of pure labour productivity growth, the manufacturing and service sectors contributed equally to the aggregate Canada‐U.S. labour productivity growth gap during the 1987–98 period. But, in terms of total industrial contributions, which also take into account the contributions from a change in relative size, the service sector was the largest contributor. We also find that high labour productivity growth industries did not attract resources from stagnant industries – a phenomenon consistent with Baumol's cost disease of stagnant industries. JEL Classification: O47, C43
Tariffs versus quotas in the presence of imperfect competition and cross‐border externalities
Authors: Furusawa Taiji , Higashida Keisaku , Ishikawa Jota
Published: February 2004

Abstract.  We consider trade policies intended to affect the production of a foreign monopolist that generates negative externalities. We derive the optimal tariff and optimal import quota and examine which policy measure should be used to maximize domestic welfare. We find that if the domestic government does not have full information on the foreign firm's production method and if cross‐border externalities exist, import quotas are in some cases preferable to tariffs. Otherwise, however, tariffs are preferable to quotas. JEL Classification: F13, F18
The determinants of bilateral trade
Authors: Lai Huiwen , Chun Zhu Susan
Published: February 2004

Abstract.  In this paper we present a monopolistic competition model that incorporates asymmetric trade barriers and international differences in production costs. The model implies a highly non‐linear bilateral trade equation. Estimation of this equation yields parameters for the elasticity of substitution and trade costs that are more reasonable than those found in previous studies. A simulation indicates that trade liberalization will shift trade from rich countries to poor countries and from within continental trading partners with preferential trade agreements to intercontinental trading partners. JEL Classification: F1
Common markets and trade liberalization
Authors: Hadjiyiannis Costas
Published: February 2004

Abstract.  The GATT Rounds show that trade liberalization is essentially a cooperative non‐stationary dynamic process. Therefore, the impact of Regionalism on trade liberalization possibly changes over time. I adapt the trade liberalization model of Devereux (1997) to examine how this impact varies. Common markets lead to a one‐time shock in immediate tariffs, as well as to a change in their rate of decline. I find that common markets that happen late in the trade liberalization process are more likely to lead to a decline in immediate tariffs. Common markets also increase the rate of decline of tariffs after their formation. JEL Classification: F03, F15
The Late Triassic Schilderia Adamanica and Woodworthia Arizonica Trees of the Petrified Forest National Park, Arizona, Usa
Authors: Creber G. T. , Ash S. R.
Published: February 2004

Two fossil tree species, both with unusual characteristics, occur in the Upper Triassic of the Petrified Forest National Park, Arizona, USA and adjacent areas. The first, Schilderia adamanica, has a highly idiosyncratic secondary xylem structure which contains normal uniseriate and broad complex multiseriate ‘herring‐bone’ rays. The trunk cross‐section of the secondary xylem may be either of a normal pycnoxylic type with a central pith and rays radiating from that or it may consist of appressed ‘xylem masses’ with rays curving towards one another at their extremities. The second, Woodworthia arizonica, has narrow, horizontal vascular traces traversing the entire radial width of the secondary xylem. By analogy with extant tree species, these traces would have terminated on preventitious buds deeply embedded in the bark which, in the case of these fossil trunks, have failed to be silicified. Such buds have the capacity to develop into epicormic shoots when the crown foliage of the tree is damaged. A further specimen of W. arizonica is recorded for the first time from the Permian of southern Brazil. Reconstruction drawings of both trees are produced.
Phylogeny and Systematics of Holasteroid Echinoids and Their Migration Into the Deep‐sea
Authors: Smith Andrew B.
Published: February 2004

Holasteroids are a major clade of irregular echinoids that today is confined to the deep‐sea, but which has a rich fossil record extending back to the start of the Cretaceous Period. A cladistic analysis of this clade, encompassing the great majority of living and fossil genera, is undertaken based on new data on test architecture. The classification of the group is reviewed and a new hierarchical scheme is proposed. The highly atypical apical disc structure of pourtalesiid holasteroids is discussed and critical data for understanding its plate homologies are provided by the most primitive pourtalesiid, the Late Cretaceous Galeaster. This supports the idea that plates previously identified as posterior genital plates in pourtalesiids are in fact ocular plates II and IV. An evolutionary tree for holasteroids is constructed by calibrating the cladogram against the stratigraphic record. This is then used to examine how holasteroid diversity and ecology have changed through time. Holasteroids have migrated into the deep‐sea at least four times independently. Three of these lineages can be traced back to sister taxa living in deep‐water continental shelf environments in the Late Cretaceous–early Tertiary, while a fourth represents a very much younger migration event, possibly Late Miocene in age.
Peer Support: Expectations and Realities
Authors: Baginsky Mary
Published: February 2004

This article describes an evaluation of fourteen peer‐support schemes in seven primary schools and seven secondary schools where NSPCC advisers worked closely with the schools. Each school received a questionnaire at the start of their involvement and, after about 12 months, the researcher visited each of the schools to conduct in‐depth interviews with the person who had completed the original questionnaire. The evaluation explored why the schools had undertaken this work and what the potential benefits to the schools and the students were. The details of the schemes and the findings specific to primary and secondary sectors are also discussed. In particular, training, unrealistic expectations about behaviour and the uses of staff times are debated. The author concludes that peer‐support schemes can be mistakenly seen as a panacea.
Should Children Attend Their Parent's Funerals?
Authors: Holland John
Published: February 2004

The paper discusses elements of the findings of ‘Iceberg’, a doctoral study at the University of York addressing many issues of child bereavement through a retrospective study of nearly one hundred individuals who had either experienced the death of a parent when they were at school, or were the surviving parent of such a child. The research revealed issues of lack of control and information for children after a parental death. Forty‐seven per cent of those in the study attended the funeral of their parent. There was correlation between the age of children and attendance at the funeral. Of the fifty‐three per cent of children not attending, twenty‐four per cent of them were forbidden to attend, whilst eleven per cent of them were distracted from attending the funeral, such as being sent to school or a neighbours and being unaware that it was taking place. None of the children attending the funeral reported any negative experiences, and two thirds of them reported it as a positive or helpful event. In contrast, over three‐quarters of those not attending later wished that they had. Over a third had feelings of regret, others feeling that they had been excluded from the family at the time of the death, and felt anger, hurt, and frustration. The conclusion was that the best strategy is to give children informed choice about whether or not to attend. If children do attend a negative outcome seems unlikely, but it would be prudent to prepare them as to what to expect at the ceremony.
An Evaluation of Strategies and Professional Development Needs on Attendance Issues within an LEA
Authors: Reid Ken
Published: February 2004

This is the first article to focus specifically on an evaluation of the existing strategic policies and related professional development needs on attendance within an LEA. Such evaluations are becoming more important as LEAs respond to their first ever OFSTED and prepare for follow‐up visits and/or second inspections. Recent evidence suggests that attendance issues are becoming central to overall outcomes in OFSTED visits and in their subsequent reports to LEAs.

This paper outlines the evidence from recent international and British research, considers the national scene and role of the education welfare service and then examines existing practice on attendance within an LEA. The findings of an in‐depth investigation into attendance issues within the LEA are then presented followed by key recommendations, an analysis of professional training needs as well as providing evidence on the LEA's progress since these training needs have been fulfilled.
Fostering Spirituality in a Pastoral Care Context
Authors: English Leona M. , Fenwick Tara J. , Parsons Jim
Published: February 2004

This article addresses the issue of promoting spirituality as a dimension of pastoral care in schools. The everyday practice of caring and giving may leave carers tired, depleted of spiritual sustenance, and without practices that nurture their spirituality. This article proposes that spirituality is an essential element of pastoral care, and that it can be promoted through examination of one's sense of vocation, bodywork, journal writing and nurturing soul friends.
Spontaneous Coronary Artery Dissection with Pseudoaneurysm Formation Diagnosed by Intravascular Ultrasound: A Case Report
Authors: Aqel Raed A. , Zoghbi Gilbert J. , Iskandrian Ami E.
Published: February 2004

Spontaneous coronary artery dissection is a rare cause of myocardial ischemia. Coronary artery pseudoaneurysm may occur after percutaneous coronary interventions and rarely spontaneously. We present a patient who had spontaneous coronary artery dissection with formation of a pseudoaneurysm diagnosed by intravascular ultrasound. (ECHOCARDIOGRAPHY, Volume 21, February 2004)
The Mind's Nose
Authors: Djordjevic J. , Zatorre R.J. , Petrides M. , Jones-Gotman M.
Published: February 2004

We examined odor imagery by looking for its effects on detection of weak odors. Seventy-two healthy subjects performed a forced-choice odor detection task in one of three conditions: after being told to imagine an odor (odor imagery), after being told to imagine an object (visual imagery), or without having received imagery instructions (no-imagery control). For the two imagery conditions, the presented and imagined stimuli were either the same (matched) or different (mismatched). There was a significant difference between detection in the matched and mismatched conditions for odor imagery, but not for visual imagery. We conclude that our paradigm does measure odor imagery and that the effect of imagery on detection is both content- and modality-specific. Further, the difference between conditions was due to lower detection with mismatched odor imagery than without imagery, indicating that interference underlies the effect.
True Photographs and False Memories
Authors: Lindsay D. Stephen , Hagen Lisa , Read J. Don , Wade Kimberley A. , Garry Maryanne
Published: February 2004

Some trauma-memory-oriented psychotherapists advise clients to review old family photo albums to cue suspected “repressed” memories of childhood sexual abuse. Old photos might cue long-forgotten memories, but when combined with other suggestive influences they might also contribute to false memories. We asked 45 undergraduates to work at remembering three school-related childhood events (two true events provided by parents and one pseudoevent). By random assignment, 23 subjects were also given their school classes' group photos from the years of the to-be-recalled events as memory cues. As predicted, the rate of false-memory reports was dramatically higher in the photo condition than in the no-photo condition. Indeed, the rate of false-memory reports in the photo condition was substantially higher than the rate in any previously published study.
Cherry Pit Primes Brad Pitt
Authors: Burke Deborah M. , Locantore Jill Kester , Austin Ayda A. , Chae Bryan
Published: February 2004

This study investigated why proper names are difficult to retrieve, especially for older adults. On intermixed trials, young and older adults produced a word for a definition or a proper name for a picture of a famous person. Prior production of a homophone (e.g., pit) as the response on a definition trial increased correct naming and reduced tip-of-the-tongue experiences for a proper name (e.g., Pitt) on a picture-naming trial. Among participants with no awareness of the homophone manipulation, older but not young adults showed these homophone priming effects. With a procedure that reduced awareness effects (Experiment 2), prior production of a homophone improved correct naming only for older adults, but speeded naming latency for both age groups. We suggest that representations of proper names are susceptible to weak connections that cause deficits in the transmission of excitation, impairing retrieval especially in older adults. We conclude that homophone production strengthens phonological connections, increasing the transmission of excitation.
Attention and the Processing of Emotional Words and Names
Authors: Harris Christine R. , Pashler Harold
Published: February 2004

Previous research has suggested that a person's own name or emotionally charged stimuli automatically “grab” attention, potentially challenging limited-capacity theories of perceptual processing. In this study, subjects were shown two digits surrounding a word and asked to make a speeded judgment about whether the parity of the two digits matched. When the subject's own name was presented on a few scattered trials, responses were markedly slowed (replicating a previous study). However, in a subsequent block of trials in which half the words were the subject's name, the slowing did not occur. The same slowing occurred (but even more fleetingly) when an emotionally charged word was presented between the digits. When the name was embedded among multiple distractor words, it ceased to slow reaction times. The results suggest that perceptual analysis of high-priority stimuli is subject to the usual capacity limitations of other stimuli, but when enough capacity is available for a high-priority stimulus to be perceived, a transient surprise reaction may interrupt ongoing processing.
Paying Attention to Meaning
Authors: Barnard P.J. , Scott S. , Taylor J. , May J. , Knightley W.
Published: February 2004

Several paradigms show that responses to one event compromise responses to a second event for around 500 ms. Such effects are generally attributed to attentional capacity limitations associated with processing information in the first event. In a task in which targets could be distinguished only by their meaning, we varied the semantic relationship between distractors and targets following at different lags. Semantic relatedness alone produced a classic attentional blink. We conclude by discussing how attention theory might best accommodate these new effects.
Unifying Representations and Responses
Authors: Spencer John P. , Schutte Anne R.
Published: February 2004

A dominant account of perseverative errors in early development contends that such errors reflect a failure to inhibit a prepotent response. This study investigated whether perseveration might also arise from a failure to inhibit a prepotent representation. Children watched as a toy was hidden at an A location, waited during a delay, and then watched the experimenter find the toy. After six observation-only A trials, the toy was hidden at a B location, and children were allowed to search for the toy. Two- and 4-year-olds' responses on the B trials were significantly biased toward A even though they had never overtly responded to this location. Thus, perseverative biases in early development can arise as a result of prepotent representations, demonstrating that the prepotent-response account is incomplete. We discuss three alternative interpretations of these results, including the possibility that representational and response-based biases reflect the operation of a single, integrated behavioral system.
Unconscious Color Priming Occurs at Stimulus- Not Percept-Dependent Levels of Processing
Authors: Breitmeyer Bruno G. , Ro Tony , Singhal Neel S.
Published: February 2004

Although past studies have shown that visual information can be processed without awareness, the types and levels of this processing have yet to be determined. We used metacontrast masking to explore unconscious priming effects of white, blue, and green stimuli generated on a color video display. We found that a white prime tends to act more like a green than a blue one. Color confusions among unmasked and masked primes and calibrations of the display phosphors show that physical rather than perceptual properties of the stimuli best explain the white prime's effects. We conclude that unconscious color priming in normal observers occurs at early wavelength-dependent levels of processing prior to later color-percept-dependent levels.
The Role of Motivation in the Age-Related Positivity Effect in Autobiographical Memory
Authors: Kennedy Quinn , Mather Mara , Carstensen Laura L.
Published: February 2004

This study reveals that older adults have a positivity effect in long-term autobiographical memory and that a positivity bias can be induced in younger adults by a heightened motivation to regulate current emotional well-being. Three hundred nuns, ages 47 to 102 years, recalled personal information originally reported 14 years earlier. They did so under experimental conditions that repeatedly primed them to focus on their current emotional states or on their memory accuracy, or that provided no instructional focus (control condition). Both older control participants and participants who were focused on emotional states showed a tendency to remember the past more positively than they originally reported in 1987. In contrast, both younger control participants and participants who were focused on accuracy tended to remember the past more negatively than originally reported.
An Anatomy of Price Dynamics in Illiquid Markets: Analysis and Evidence from Local Housing Markets
Authors: Capozza Dennis R. , Hendershott Patric H. , Mack Charlotte
Published: February 2004

This research analyzes the dynamic properties of the difference equation that arises when markets exhibit serial correlation and mean reversion. We identify the correlation and reversion parameters for which prices will overshoot equilibrium (“cycles”) and/or diverge permanently from equilibrium. We then estimate the serial correlation and mean reversion coefficients from a large panel data set of 62 metro areas from 1979 to 1995 conditional on a set of economic variables that proxy for information costs, supply costs and expectations. Serial correlation is higher in metro areas with higher real incomes, population growth and real construction costs. Mean reversion is greater in large metro areas and faster growing cities with lower construction costs. The average fitted values for mean reversion and serial correlation lie in the convergent oscillatory region, but specific observations fall in both the damped and oscillatory regions and in both the convergent and divergent regions. Thus, the dynamic properties of housing markets are specific to the given time and location being considered.
Is Real Estate Becoming Important Again? A Neo‐Ricardian Model of Land Rent
Authors: Barker David , Sa‐Aadu Jay
Published: February 2004

Classical economists believed that land rent as a share of total income would increase with economic growth. This belief was important to many 19th and 20th century critiques of capitalism. Land rents as a share of national income apparently declined for most of the 20th century, but increased during the 1990s. In this paper, we develop a model of the classical theory of land rent that allows rent to increase or decrease as a share of national income, depending on several parameters. It seems likely that the long decline in land rent is over and that land rent in the future will slowly increase as a share of national income.
The Economics of Maintenance for Real Estate Investments
Authors: Blazenko George W. , Pavlov Andrey D.
Published: February 2004

We propose a theory of urban decay. Following a negative real estate demand shock, property managers optimally suspend maintenance and the probability that they ever restart can be modest. Because maintenance expenditures are proportionately less risky than are the incremental building profits they generate, managers impose a more demanding profit standard on maintenance than on the initial investment. This differential in profit standards means that rather than maintain existing investments, property managers favor new investments, which, if marginally acceptable, they also leave unmaintained. Contractually required maintenance (e.g., for publicly subsidized real estate investments), increases the minimum profit for the initial investment acceptance and discourages subsidized real estate investments in favor of unsubsidized investments. However, the required profit for acceptance of a permanently maintained investment is below the profit boundary for maintenance if maintenance is not contractually required. Consequently, the subsidy that induces the investment is least expensive if maintenance is not required, more expensive if maintenance is permanently required and most expensive if maintenance is induced immediately after initial construction but thereafter is at the discretion of the manager. All of our findings are strongest for poorer quality properties.
Do Out‐of‐State Buyers Pay More for Real Estate? An Examination of Anchoring‐Induced Bias and Search Costs
Authors: Lambson Val E. , McQueen Grant R. , Slade Barrett A.
Published: February 2004

We explore the questions of whether and why out‐of‐state buyers pay more for real estate than their in‐state counterparts. Theoretically, we develop a model capable of explaining a premium if out‐of‐state buyers have high search costs, upwardly biased beliefs about prices or an unusually short time horizon to purchase. Empirically, we find that out‐of‐state buyers pay a statistically significant and economically meaningful premium for apartment complexes in the Phoenix area. We also find some evidence consistent with the premium being driven by high search costs, biased beliefs (anchoring) and haste associated with out‐of‐state buyers.
A Semiparametric Method for Estimating Local House Price Indices
Authors: Clapp John M.
Published: February 2004

Spatial autoregressive hedonic models utilize house prices lagged in space and time to produce local house price indices, for example, the spatial and temporal autoregressive (STAR) model might be used this way. This paper complements these models with a semiparametric approach, the Local Regression Model (LRM). The greater flexibility of the LRM may allow it to identify space–time asymmetries missed by other models. The LRM is fitted to 49,511 sales from 1972Q1 to 1991Q2 in Fairfax County, Virginia. The local price indices display plausible and significant variations over space and time. The LRM price indices in selected neighborhoods are shown to differ significantly from those in some other neighborhoods. A new method for estimating standard errors addresses an overlooked problem common to all local price indices: how to evaluate the amount of noise in the estimates. Out‐of‐sample prediction errors demonstrate that LRM adds significant information to the hedonic model.
Economic Depreciation of Residential Real Estate: Microlevel Space and Time Analysis
Authors: Smith Brent C
Published: February 2004

Three elements in the study of real estate depreciation that warrant further consideration are uncovered: the spatial variation of depreciation on a micro scale, the variability of depreciation within a single market across time and the recognition of land value as an influence in modeling real property prices. Taken together, these three dimensions provide an opportunity to further expand the understanding of residential economic depreciation while enhancing the predictive power of real estate market models. The analytical results, utilizing a land‐value‐adjusted hedonic model, indicate that both the intramarket location and the year in which the property sold have significant impacts on the observed rate of economic depreciation. Such information is vitally important to policymakers and others interested in accurate modeling of real estate markets.
Movement and dispersal of the invasive signal crayfish Pacifastacus leniusculus in upland rivers
Authors: Bubb Damian H. , Thom Timothy J. , Lucas Martyn C.
Published: February 2004

1. The American signal crayfish Pacifastacus leniusculus, an invasive species widely introduced throughout Europe, is a major threat to native European crayfish species and is causing increasing concern because of its wide impact on aquatic ecosystems.

2. Whilst various control and management methods have been proposed, very little is known about the factors influencing dispersal and movements of signal crayfish.

3. Sixty‐four adult signal crayfish (carapace length 31.9–63.8 mm) were radiotagged in upland rivers in northern England, during four periods. Tracking was carried out at two sites, a low‐density establishing population and a high‐density established population. Tracking was carried out at both sites concurrently during midsummer (June to August 2002), during late summer (August to September 2001) at the low‐density population site and during autumn to winter (October to February 2000/01) at the high‐density population site.

4. Maximum movement occurred during midsummer. Temperature appeared to be a major factor influencing the timing and extent of movements between tracking periods.

5. The frequency distribution of the maximum distance moved upstream and downstream by radiotagged crayfish showed an inverse power relationship. The median maximal upstream and downstream distances moved were 13.5 m (range 0–283 m) and 15 m (range 0–417 m), respectively. There was a significant difference between the distributions of upstream and downstream ranges, with greater distances moved downstream.

6. All downstream movements made by crayfish appeared to be active movements and not the result of passive movement during periods of high discharge. There was no apparent influence of size, sex or density on the amount of movement recorded.

7. The study provides important information on the spatial and temporal behaviour of introduced crayfish in upland lotic systems. In contrast to lowland rivers, our results suggest that flow or gradient may influence the invasive potential of signal crayfish in an upstream direction in upland rivers.
Cyst bank life‐history model for a fairy shrimp from ephemeral ponds
Authors: Ripley Bonnie J. , Holtz Janette , Simovich Marie A.
Published: February 2004

1. Ephemeral wetland habitats provide a useful model system for studying how life‐history patterns enable populations to persist despite high environmental variation. One important life‐history trait of both plants and crustaceans in such habitats involves hatching/germination of only some of the eggs/seeds at any time. This bet‐hedging leads to the development of a bank composed of dormant propagules of many ages.

2. The San Diego fairy shrimp, Branchinecta sandiegonensis (Crustacea: Anostraca), a dominant faunal element of ephemeral ponds in San Diego, California, is a suitable organism for studying the consequences of highly fluctuating environmental conditions. As a result of large‐scale habitat loss, the species is also endangered, and this motivated our specific study towards understanding the hatching dynamics of its egg bank for planning conservation efforts such as pool restoration and re‐creation.

3. We formulated a matrix population model using egg age within the bank to study the relationship between adult survival and reproduction, and survival in and hatching from the egg bank. As vital rates for fairy shrimp are only poorly known, we generated 48 matrices with parameters encompassing ranges of likely values for the vital rates of B. sandiegonensis. We calculated population growth rates and eigenvalue elasticities both for a static model and a model with periodic reproductive failure.

4. The model shows that in good filling events, population growth rate is very high and the egg bank is increased dramatically. While population growth rate is insensitive to long‐term survival in the egg bank in our static deterministic model, it becomes sensitive to survival in the egg bank when a regime of periodically failed reproductive events is imposed.

5. Under favourable conditions, it was best for shrimp to hatch from eggs as soon as possible. However, under a regime where failed reproductive events were common, it was best to hatch after several pool fillings. Because conditions change from favourable to unfavourable unpredictably, variation in age within the egg bank appears to be critical for the persistence of the population. This attribute needs to be carefully considered when restoring or creating new pools for conservation purposes.
Dynamics and ecological significance of daily internal load of phosphorus in shallow Lake Balaton, Hungary
Authors: Istvánovics Vera , Osztoics András , Honti Márk
Published: February 2004

1. As supported by field data, turbidity recorded by light scattering sensors could reliably be converted into concentration of suspended particulate matter (SPM) and coefficient of vertical light attenuation (Kd) in Lake Balaton.

2. Autocorrelation analysis revealed that proper determination of SPM concentration and Kd required daily sampling. To approximate daily rate of resuspension, 15 min or more frequent measurements were needed. Thus, routine monitoring provides very little insight into environmental variability of shallow lakes as habitats for phytoplankton.

3. The internal P load was estimated from daily rate of resuspension and P desorption capacity of sediments. The latter was assumed to be proportionate to the potentially mobile inorganic P content of SPM. A comparison with net primary production and nutrient status of phytoplankton showed that the proposed method of estimating time series of internal P load captured seasonal trends.

4. The daily rate of resuspension was high whereas that of internal P load was low in Lake Balaton relative to other shallow lakes. The latter reflects favourable behaviour of the calcite‐rich sediments. As a consequence, carrying capacity of Basin 1 of Lake Balaton was P‐determined.

5. The timing of external and internal loads was radically different. While the former showed mostly seasonal changes, large pulses characterised the latter. As a consequence, internal load may supply more P to phytoplankton growth during the critical summer months than external load. However, the relative importance of these sources may show substantial interannual variability.

6. Large resuspension events often followed each other during periods of 10–15 days. It has been shown that disturbances in this frequency range are of key importance in maintaining the diversity of phytoplankton. We propose that resuspension can be perceived not only as a disturbance factor but also as a factor that periodically relaxes nutrient stress. The former feature may dominate the instantaneous effect, whereas the latter may determine the persistent effect of resuspension on succession of phytoplankton.
Predation impact of Leptodora kindtii on population dynamics and morphology of Bosmina fatalis and B. longirostris in mesocosms
Authors: Chang Kwang‐Hyeon , Hanazato Takayuki
Published: February 2004

1. We assessed the impact of predation by the invertebrate predator Leptodora kindtii on Bosmina longirostris and B. fatalis, which show seasonal and reciprocal succession patterns in Lake Suwa, in a mesocosm experiment using 20‐L tanks with or without the predator under different food conditions. We also analysed morphological responses of the two Bosmina species to the predator in the tanks.

2. Bosmina fatalis dominated B. longirostris regardless of predator presence under high food density. However, the presence of Leptodora induced the dominance of B. fatalis more rapidly than its absence. On the contrary, no dominance of B. fatalis was observed in tanks with low food density, irrespective of the presence of the predator. Only B. fatalis showed morphological changes in response to the presence of Leptodora.

3. Mucrone length and antennule shape (angle between body and antennule and angle between antennules) showed marked responses at both high and low food densities, but antennule length responded only at high food density. Mucrone length seems to be a more effective defence against Leptodora.

4. The results suggest that B. fatalis is a superior competitor against B. longirostris and is more resistant to Leptodora predation, especially in good food conditions. The repeatedly observed seasonal succession of the two Bosmina species in the eutrophic Lake Suwa – the replacement of B. longirostris by B. fatalis following the occurrence of abundant Leptodora– seems to be caused by the selective predation of Leptodora on B. longirostris as well as the competitive ability of B. fatalis.
Factors regulating recruitment from the sediment to the water column in the bloom‐forming cyanobacterium Gloeotrichia echinulata
Authors: Karlsson‐Elfgren Irene , Rengefors Karin , Gustafsson Susanne
Published: February 2004

1. The influence of light, temperature, sediment mixing and sediment origin (water depth) on the recruitment of the cyanobacterium Gloeotrichia echinulata was examined in the laboratory.

2. Light and temperature were the most important factors initiating germination in G. echinulata.

3. The extent of germination (recruited biovolume) was mainly regulated by temperature and sediment mixing. Furthermore, sediment mixing significantly enhanced the frequency of observed heterocysts and colonies.

4. Despite the fact that the deep and shallow sediments contained a similar number of akinete colonies, the highest recruitment occurred from shallow sediments, indicating that akinetes from shallow sediments have a higher viability than those from deeper parts of the lake.

5. Our results support the hypothesis that shallow sediments are more important than profundal sediments for the recruitment of G. echinulata to the pelagic zone.
An HPLC analysis of the summer phytoplankton assemblage in Lake Baikal
Authors: Fietz Susanne , Nicklisch Andreas
Published: February 2004

1. The enormous size and spatial heterogeneity of Lake Baikal require rapid methods for large sample sets. We therefore tested the applicability of a novel, high‐performance liquid chromatography (HPLC)‐based, combination of methods for analysing phytoplankton. In July 2001, samples were collected in a transect across the lake at various depths down to 30 m. Phytoplankton (>3 μm) and autotrophic picoplankton (APP) were counted under light and epifluorescence microscopes, respectively. Pigments were analysed with HPLC.

2. The pigment data allowed the contributions of the dominant phytoplankton groups to the total chlorophylla(Chla) in the lake to be estimated by multiple linear regression and by the CHEMTAX matrix factorisation program. Three marker pigments, fucoxanthin, lutein and zeaxanthin, were shown to be useful indicators of the abundance and spatial distribution of certain phytoplankton groups. The relative contributions of the various phytoplankton groups to the total Chlain the lake determined using these marker pigments were similar, but not identical, to those determined by cell counts.

3. Pigment analyses of isolated strains from Lake Baikal and some European lakes confirmed that phycoerythrin‐containing Cyanobacteria with very high amounts of zeaxanthin were responsible for the low Chla/zeaxanthin ratios of the water samples. A picoplanktonic species of Eustigmatophyceae was isolated from the lake. Its high violaxanthin content, responsible for very low Chla/violaxanthin ratios of some water samples, can be used to estimate the contribution of this group to total Chla.
Salinity tolerance of diapausing eggs of freshwater zooplankton
Authors: Bailey Sarah A. , Duggan Ian C. , van Overdijk Colin D.A. , Johengen Thomas H. , Reid David F. , MacIsaac Hugh J.
Published: February 2004

1. Many freshwater zooplankton produce diapausing eggs capable of withstanding periods of adverse environmental conditions, such as anoxia, drought and extreme temperature. These eggs may also allow oligostenohaline species to survive increased salinity during periods of tidal flux or evaporation, and here we test the ability of diapause eggs to withstand such conditions.

2. Salinity tolerance may also enable organisms to invade new environments. The increased rate of introduction of non‐indigenous species to the Laurentian Great Lakes since 1989, when ballast water exchange regulations (to replace fresh/brackish water at sea with full seawater) were first implemented for transoceanic vessels, has stimulated studies that explore mechanisms of introduction, other than of active animals, in ballast water. One hypothesis proposes that freshwater organisms transported in ballast tanks as diapausing eggs may be partially responsible for the increased rate of species introduction, as these eggs may tolerate a wide array of adverse environmental conditions, including exposure to saline water.

3. We collected ballast sediments from transoceanic vessels entering the Great Lakes, isolated diapausing eggs of three species (Bosmina liederi, Daphnia longiremis and Brachionus calyciflorus), and measured the effect of salinity on hatching rate. In general, exposure to salinity significantly reduced the hatching rate of diapausing eggs. However, as non‐indigenous species can establish from a small founding population, it is unclear whether salinity exposure will be effective as a management tool.
Salinity, depth and the structure and composition of microbial mats in continental Antarctic lakes
Authors: Sabbe Koen , Hodgson Dominic A. , Verleyen Elie , Taton Arnaud , Wilmotte Annick , Vanhoutte Koenraad , Vyverman Wim
Published: February 2004

1. Lakes and ponds in the Larsemann Hills and Bølingen Islands (East‐Antarctica) were characterised by cyanobacteria‐dominated, benthic microbial mats. A 56‐lake dataset representing the limnological diversity among the more than 150 lakes and ponds in the region was developed to identify and quantify the abiotic conditions associated with cyanobacterial and diatom communities.

2. Limnological diversity in the lakes of the Larsemann Hills and Bølingen Islands was associated primarily with conductivity and conductivity‐related variables (concentrations of major ions and alkalinity), and variation in lake morphometry (depth, catchment and lake area). Low concentrations of pigments, phosphate, nitrogen, DOC and TOC in the water column of most lakes suggest extremely low water column productivity and hence high water clarity, and may thus contribute to the ecological success of benthic microbial mats in this region.

3. Benthic communities consisted of prostrate and sometimes finely laminated mats, flake mats, epilithic and interstitial microbial mats. Mat physiognomy and carotenoid/chlorophyll ratios were strongly related to lake depth, but not to conductivity.

4. Morphological‐taxonomic analyses revealed the presence of 26 diatom morphospecies and 33 cyanobacterial morphotypes. Mats of shallow lakes (interstitial and flake mats) and those of deeper lakes (prostrate mats) were characterised by different dominant cyanobacterial morphotypes. No relationship was found between the distribution of these morphotypes and conductivity. In contrast, variation in diatom species composition was strongly related to both lake depth and conductivity. Shallow ponds were mainly characterised by aerial diatoms (e.g. Diadesmis cf. perpusilla and Hantzschia spp.). In deep lakes, communities were dominated by Psammothidium abundans and Stauroforma inermis. Lakes with conductivities higher than ±1.5 mS cm−1 became susceptible to freezing out of salts and hence pronounced conductivity fluctuations. In these lakes P. abundans and S. inermis were replaced by Amphora veneta. Stomatocysts were important only in shallow freshwater lakes.

5. Ice cover influenced microbial mat structure and composition both directly by physical disturbance in shallow lakes and by influencing light availability in deeper lakes, as well as indirectly by generating conductivity increases and promoting the development of seasonal anoxia.

6. The relationships between diatom species composition and conductivity, and diatom species composition and depth, were statistically significant. Transfer functions based on these data can therefore be used in paleolimnological reconstruction to infer changes in the precipitation–evaporation balance in continental Antarctic lakes.
Seasonal patterns of sediment loading and benthic invertebrate community dynamics in Lake Tanganyika, Africa
Authors: Donohue Ian , Irvine Kenneth
Published: February 2004

1. This study investigated the spatiotemporal dynamics of benthic invertebrate communities located close to the mouths of the Kalambo and Lunzua Rivers, at the southern end of Lake Tanganyika, and subject to varying degrees of sediment load.

2. Metrics of exposure to riverine sediments were associated inversely with abundance and diversity of benthic organisms at sampling locations adjacent to both river mouths, indicating a major effect of riverine sediments on the structure of near‐shore benthic communities.

3. A lower abundance of benthos was found at the mouth of the Lunzua River, which exports significantly higher sediment loads than the Kalambo.

4. Seasonal cycles of abundance and diversity in the benthos varied with distance from river mouths. This has important implications for monitoring programmes investigating benthic communities close to the mouths of rivers.

5. Our findings suggest that recent increases in the sediment loading of Lake Tanganyika, owing to anthropogenic catchment disturbance, impact significantly on biological diversity throughout the lake littoral, which provides habitat for the majority of species in the lake.