Annual Production (annual + production)

Distribution by Scientific Domains


Selected Abstracts


Life history and production of Agapetus quadratus (Trichoptera: Glossosomatidae) in a temporary, spring-fed stream

FRESHWATER BIOLOGY, Issue 6 2005
MARUXA ÁLVAREZ
Summary 1. The life history and trophic basis of production of the caddisfly grazer Agapetus quadratus were studied in the torrent Gorg Blau, a spring-fed stream on the island of Majorca that dries annually during summer. 2. Quantitative random samples were taken every 2,3 weeks during an annual surficial flow period, from November 2000 to mid-July 2001. Instars of field-collected larvae were determined by measurements of head width and pronotum length, and the sex of all pupae was determined to study sexual dimorphism and sex ratio. 3. Stage-frequency histograms suggested a trivoltine population, with an average cohort time of 4 months. Larval development was asynchronous, with continuous growth and overlapping generations. Recruitment peaks were identified in mid-November, early March and late June, indicative of winter, spring and summer generations. On average, females were larger than males and the mean sex ratio was 2 : 3 (females : males). Population densities and biomasses derived from the field data were used to calculate production and turnover rate. 4. Annual production of A. quadratus in the torrent Gorg Blau (4.80 g dry mass m,2 year,1) was the highest ever reported for the genus, being comparable with that estimated for some insects with rapid development and multiple cohorts. 5. Estimates of production of A. quadratus were combined with foregut content analysis to estimate the fraction of total production derived from the principal food sources: algae and organic detritus. Algae supported a major proportion of the production of this grazer. 6. The low density of predators characteristic of many temporary streams, and the small amplitudes in discharge and temperature during most of the wet period that characterise the spring habitats might allow high levels of grazer production in this particular Mediterranean stream. [source]


Life Cycle, Feeding and Production of Isoptena serricornis(Pictet, 1841) (Plecoptera, Chloroperlidae)

INTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 2 2004
Derka
Abstract Some aspects of the biology and ecology (life cycle, feeding and production) of a population of Isoptena serricornis in the Rudava River (Slovakia) are studied, reported and discussed. The life cycle is annual, with slow growth in autumn-winter and fast growth in late summer and spring. The growth decreased two weeks before the Fall Equinox and increased two weeks after the Spring Equinox. The flight period spans from the end of May to the beginning of July. The presence of large sand particles in the gut of all studied nymphs is of note, and indicates that I. serricornis acts as a deposit-collector species. Nymphal food is principally composed of detritus, unicellular organisms and, in nymphs of intermediate or large size, Chironomidae larvae. Adult food is composed fundamentally of different types of pollen grains. Males usually have lower food content than females. Annual production of this species (,694,750 mg · m,2) is very high in relation to other previously studied Chloroperlidae. This is probably largely responsible for I. serricornis being one of the most abundant components of the macroinvertebrate community in its habitat in the Rudava River. A negative correlation between production and temperature was observed. [source]


Individual, Population, Community, and Ecosystem Consequences of a Fish Invader in New Zealand Streams

CONSERVATION BIOLOGY, Issue 1 2003
Colin R. Townsend
But because invaders can have unexpected indirect effects in food webs, invasion ecologists need to integrate processes at the population level and other ecological levels. I describe a series of coordinated studies in New Zealand streams that address the effect of an exotic fish on individual behavior, population, community, and ecosystem patterns. Such case studies are important as an aid to the formulation of policy about invasions that are especially likely to become problematic. At the individual level, grazing invertebrates showed changes in behavior as a result of the introduction of brown trout ( Salmo trutta), a predator that exerts a very different selection pressure than do native fish. At the population level, trout have replaced nonmigratory galaxiid fish in some streams but not others, and have affected the distributions of crayfish and other large invertebrates. At the community level, trout have suppressed grazing pressure from invertebrates and are thus responsible for enhancing algal biomass and changing algal species composition. Finally, at the ecosystem level, essentially all annual production of invertebrates is consumed by trout ( but not by galaxiids), and algal primary productivity is six times higher in a trout stream. This leads, in turn, to an increased flux of nutrients from the water to the benthic community. The trout invasion has led to strong top-down control of community structure and ecosystem functioning via its effects on individual behavior and population distribution and abundance. Particular physiological, behavioral, and demographic traits of invaders can lead to profound ecosystem consequences that managers need to take into account. Resumen: Para desarrollar procedimientos y políticas de manejo efectivos a menudo será necesario conocer la biología de la población de especies invasoras. Sin embargo, debido a que los invasores pueden tener efectos indirectos inesperados en las redes alimenticias, ecólogos de invasión necesitan integrar procesos en la población y otros niveles ecológicos. Describo una serie de estudios coordinados en arroyos de Nueva Zelanda que enfocan el impacto de un pez exótico sobre los patrones de comportamiento individual, de la población, la comunidad y el ecosistema. Tales estudios de caso son importantes como un auxiliar para la formulación de políticas sobre invasiones que pueden ser especialmente problemáticas. Al nivel individual, los invertebrados que pastorean mostraron cambios de conducta como resultado de la introducción de la trucha café ( Salmo trutta), un depredador que ejerce una presión de selección muy diferente a la de los peces nativos. En el nivel de población, las truchas han reemplazado a peces galaxídos no migratorios en algunos arroyos pero no en otros y han afectado las distribuciones de cangrejos de río y otros invertebrados mayores. Al nivel de comunidad, las truchas han suprimido la presión de pastoreo por invertebrados y por lo tanto son responsables del incremento de la biomasa de algas y del cambio en la composición de especies de algas. Finalmente, a nivel de ecosistema, la producción anual de invertebrados esencialmente es consumida por las truchas ( pero no por galaxídos), y la productividad primaria de algas es seis veces mayor en arroyos con truchas. A su vez, esto conduce a incrementos en el flujo de nutrientes del agua hacia la comunidad béntica. La invasión de truchas ha conducido a un fuerte control de arriba hacia abajo de la estructura de la comunidad y del funcionamiento del ecosistema por medio de sus efectos sobre la conducta individual y la distribución y abundancia de la población. Las características fisiológicas, de conducta y demográficas particulares de los invasores pueden llevar a consecuencias profundas en los ecosistemas que los administradores necesitan tomar en consideración. [source]


Trophodynamic modeling of walleye pollock (Theragra chalcogramma) in the Doto area, northern Japan: model description and baseline simulations

FISHERIES OCEANOGRAPHY, Issue 2004
ORIO YAMAMURA
Abstract An age-structured trophodynamic model was constructed to quantitatively analyze factors affecting post-settlement mortality and growth of walleye pollock (Theragra chalcogramma) in the Doto area, the main nursery ground of the Japan Pacific population. The model included (i) multiple age classes of pollock, (ii) a generic predator, (iii) fisheries, and (iv) major prey of pollock. Major processes considered were (i) recruitment, (ii) bottom-up control of somatic growth, (iii) mortality because of predation, cannibalism and fishing, (iv) size-selective prey selection, (v) temperature-dependent bioenergetics such as conversion efficiency and daily consumption rate, and (vi) production and advective supply of prey. By assuming that pollock select prey based upon both relative abundance and predator,prey size relationships, the model accurately simulated seasonal and ontogenetic variations in the diet. However considering ontogenetic segregation, the model showed that, due to cannibalism, newly recruited fish would be totally consumed within 6 months after settlement. By considering segregation (10% overlap during spring and 0.1% during other seasons), an agreement of diet between the simulation and empirical data averaged 82.7% for the different seasons and fish sizes. Euphausiids, the most important prey of pollock, suffered the highest predation impact (22.2 ± 5.3 WWg m,2 yr,1) exceeding annual production in the model domain (17.2 ± 0.1 WWg m,2 yr,1), indicating that an advective supply of prey is necessary to support the pollock population. The daily ration of pollock during spring and summer averaged at 1.2 and 0.6% BW day,1 for small (,200 mm) and large (>200 mm) pollock, respectively; this daily ration was reduced by half during autumn and winter. [source]


Effects of temperature and sediment properties on benthic CO2 production in an oligotrophic boreal lake

FRESHWATER BIOLOGY, Issue 8 2010
IRINA BERGSTRÖM
Summary 1. Temperature and many other physical and chemical factors affecting CO2 production in lake sediments vary significantly both seasonally and spatially. The effects of temperature and sediment properties on benthic CO2 production were studied in in situ and in vitro experiments in the boreal oligotrophic Lake Pääjärvi, southern Finland. 2. In in situ experiments, temperature of the water overlying the shallow littoral sediment varied seasonally between 0.5 and 15.7 °C, but in deep water (,20 m) the range was only 1.1,6.6 °C. The same exponential model (r2 = 0.70) described the temperature dependence at 1.2, 10 and 20 m depths. At 2.5 and 5 m depths, however, the slopes of the two regression models (r2 = 0.94) were identical but the intercept values were different. Sediment properties (wet, dry, mineral and organic mass) varied seasonally and with depth, but they did not explain a significantly larger proportion of variation in the CO2 output rate than temperature. 3. In in vitro experiments, there was a clear and uniform exponential dependence of CO2 production on temperature, with a 2.7-fold increase per 10 °C temperature rise. The temperature response (slope of regression) was always the same, but the basic value of CO2 production (intercept) varied, indicating that other factors also contributed to the benthic CO2 output rate. 4. The annual CO2 production of the sediment in Lake Pääjärvi averaged 62 g CO2 m,2, the shallow littoral at 0,3 m depth releasing 114 g CO2 m,2 and deep profundal (>15 m) 30 g CO2 m,2. On the whole lake basis, the shallow littoral at 0,3 m depth accounted for 53% and the sediment area in contact with the summer epilimnion (down to a depth c. 10 m) 75% of the estimated total annual CO2 output of the lake sediment, respectively. Of the annual production, 83% was released during the spring and summer. 5. Using the temperature-CO2 production equations and climate change scenarios we estimated that climatic warming might increase littoral benthic CO2 production in summer by nearly 30% from the period 1961,90 to the period 2071,2100. [source]


Seasonal and inter-stream variations in the population dynamics, growth and secondary production of an algivorous fish (Pseudogastromyzon myersi: Balitoridae) in monsoonal Hong Kong

FRESHWATER BIOLOGY, Issue 9 2009
GRACE Y. YANG
Summary 1.,Balitorid loaches are widespread and highly diverse in Asian streams, yet their life history and ecology have received little attention. We investigated seasonal (wet versus dry season) and spatial variation in populations of algivorous Pseudogastromyzon myersi in Hong Kong, and estimated the magnitude of secondary production by this fish in pools in four streams (two shaded and two unshaded) over a 15-month period. 2.,Mean population densities of P. myersi ranged from 6.0 to 23.2 individuals m,2, constituting more than half (and typically >70%) of benthic fishes censused. Abundance was c. 25% greater in the wet season, when recruitment occurred. Significant density differences among streams were not related to shading conditions and were evident despite small-scale variations in P. myersi abundance among pools. Mean biomass varied among streams from 0.85 to 3.87 g ash-free dry weight (AFDW) m,2. Spatial and seasonal patterns in biomass and density were similar, apart from some minor disparities attributable to differences in mean body size among populations. 3.,All four P. myersi populations bred once a year in June and July, and life spans varied from 24 to 26 months. Populations consisted of three cohorts immediately after recruitment but, for most of the study period, only two cohorts were evident. Cohort-specific growth rates did not differ significantly among streams but, in all streams, younger cohorts had higher cohort-specific growth rates. 4.,Secondary production of P. myersi estimated by the size-frequency (SF) method was 2.7,11.5 g AFDW m,2 year,1 and almost twice that calculated by the increment-summation (IS) method (1.2,6.6 g AFDW m,2 year,1). Annual P/B ratios were 1.17,2.16 year,1 (IS) and 2.73,3.22 year,1 (SF). Highest production was recorded in an unshaded stream and the lowest in a shaded stream, but site rankings by production did not otherwise match shading conditions. Wet-season production was six times greater than dry-season production, and daily production fell to almost zero during January and February. Cool temperatures (<17 °C) may have limited fish activity and influenced detectability during some dry-season censuses. Estimates of abundance and annual production by P. myersi are therefore conservative. 5.,Comparisons with the literature indicate that the abundance and production of P. myersi in Hong Kong was high relative to other benthic fishes in tropical Asia, or their temperate counterparts in small streams. Manipulative experiments are needed to determine the influence of P. myersi, and algivorous balitorids in general, on periphyton dynamics and energy flow in Asian streams. [source]


Spatial and temporal patterns of microcrustacean assemblage structure and secondary production in a wetland ecosystem

FRESHWATER BIOLOGY, Issue 7 2009
A. MARIA LEMKE
Summary 1. In contrast to extensive studies of zooplankton in lakes, the role of microcrustaceans in wetlands is not well studied. In this study, spatial and temporal patterns of microcrustacean assemblage structure and secondary production were quantified over a 2-year period in a southeastern U.S.A. wetland. 2. Thirty-two species, including 19 cladocerans, 10 copepods and three ostracods, generated different temporal patterns of density and production between vegetated (Nymphaea) and non-vegetated (open-water) zones reflecting species-specific differences in life histories. 3. Summer assemblages were dominated by small, planktonic filter-feeders, typified by high annual production/biomass (P/B) and daily production. In contrast, winter assemblages were dominated by larger, epibenthic detritivores with low P/B and high biomass. Seasonal shifts in the relative importance of planktonic species in the warmer months to benthic and epiphytic species in the cooler months suggest that energy flow pathways through microcrustaceans may vary seasonally. 4. Total annual production was higher during both years in the Nymphaea zone (13.0 g and 13.6 g DM m,2 year,1) than the open-water (8.2 and 6.3 g DM m,2 year,1), and was similar between years for the entire wetland pond (12.3 and 12.2 g DM m,2 year,1). 5. Although wetland ecosystems have been the subject of considerable ecological research in the past 20 years, our study is one of the few to demonstrate a highly diverse and relatively productive microcrustacean assemblage. Such comprehensive production studies can be used to quantify the ecological importance of microcrustaceans in freshwater wetland ecosystems. [source]


Lifetime reproductive success in relation to morphology in the house sparrow Passer domesticus

JOURNAL OF ANIMAL ECOLOGY, Issue 4 2004
Henrik Jensen
Summary 1In this study we relate variation in lifetime reproductive success (LRS) of male and female house sparrows Passer domesticus to morphological characteristics. 2Our analyses demonstrated no sex-specific difference in the distribution of LRS. The variance in LRS was influenced mainly by variation in individual annual reproductive success, and to a lesser extent by variation in individual lifespan. 3Phenotypic traits explained a significant proportion of the variation in LRS in males, but not in females. The effect of male morphology on LRS operated mainly through an effect on the number of recruiting daughters. 4The size of the patch of black feathers on the chest of males (badge size) and male bill length were both positively associated with LRS. Lifespan and bill length were positively related and reproductive success increased with badge size. In females, number of recruiting daughters was positively related to bill length, body mass and body condition index due to the positive effect of these traits on annual production of daughters. 5These results indicate that identifying factors causing the large individual variation in LRS, which is likely to be closely related to fitness, will be important to understand microevolutionary processes in this metapopulation, and hence their demographic feedbacks. [source]


Trophic state, fish community and intensive production of salmonids in Alicura Reservoir (Patagonia, Argentina)

LAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 4 2001
P. F. Temporetti
Abstract The Governments of the Provinces located in Patagonia, Argentina, promote the intensive breeding of salmonids in the Andean Patagonian region. Although annual production is low (450 ton ha,1 year,1), some effects are significant. Waste produced by salmonid breeding (feed losses, faeces and excretion) increases nutrient and organic matter concentrations, which cause modifications of water quality, sediments and biota. A consequent risk is the elevation of eutrophication levels. Possible changes in water composition, sediments, algae and wild fish populations were studied. Sites affected by fish farming showed increased nutrient concentration, and phytoplankton and periphyton biomass. Chlorophyll a was similar at both sites (affected and unaffected by fish farm sites). Sediments clearly reflect fish farm waste inputs: total phosphorus and organic matter increased 12-fold and fourfold, respectively. The species present in the gill-net catches were the autochthonous Percichthys trucha, Odontesthes hatcheri, Diplomystes viedmensis, and the introduced salmonids Oncorhynchus mykiss, Salmo trutta, Salmo salar sebago and Salvelinus fontinalis. About 50% of the total catch was salmonids. A major portion of the catch per unit weight was composed of rainbow trout, followed by perch. The catch per unit weight obtained for this reservoir agrees with the range of values previously determined (Quiros 1990) for Patagonian reservoirs. Compared with previous studies by Freyre et al. (1991), a variation in catch composition exists. This consists mainly of an increase in the numbers and condition of O. mykiss and a decrease in P. trucha. Presence of fish that escaped from hatcheries, recognizable by their eroded fins, was observed; particularly in a sampling station near the fish cage systems. Variations in catches could be caused by cyclical changes in fish populations (Wooton 1991), by direct and indirect effects of intensive fish farming, or by a combination of both events, and can only be understood through long-term studies of catch variation. [source]


Grid-connected photovoltaic systems: the Brazilian experience and the performance of an installation

PROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 5 2001
Sérgio Henrique Ferreira de Oliveira
Just as in several other countries, the Brazilian experience of installing in place solar photovoltaic technology was first aimed at meeting the needs of rural areas. More recently, the effects of the international trend towards grid-connected photovoltaic systems are beginning to be felt in Brazil. In less than five years, the first four grid-connected photovoltaic systems have been installed, and other projects are in progress. This work presents the overall characteristics of the first four systems and the technical performance achieved by one of them, with an annual production in the range of 1500,kW,h/kWp. Copyright © 2001 John Wiley & Sons, Ltd. [source]


Composition, size and dynamics of the seed bank in a mediterranean shrubland of Chile

AUSTRAL ECOLOGY, Issue 5 2004
Javier A. Figueroa
Abstract Analysis was performed of the richness and abundance of woody species, forbs, and annual grasses in the easily germinating soil seed bank (henceforth seed bank) in a mediterranean shrubland of central Chile. The effects of successional development after fire and by microsite type (underneath or outside shrubs) on the density of seeds in the soil, and the relationship of species abundance in the seed bank with its abundance in the above-ground vegetation was examined. A total of 64 plant species were recorded in the seed bank, of which 44 were annual or biannual. Eight species were woody and another eight were perennial herbs. Four could not be identified to species level. The highest richness of established herbaceous species was recorded in late spring, with 31 species. The regeneration of the herbaceous vegetation was driven by the annual production of seeds and by a reserve of short-lived propagules in the soil. Density of all germinating seeds was significantly higher during late spring and late summer. Density of grass seeds was greater during late spring, while that of all other species was greater during late summer. Annual grass seeds accumulated in higher proportion at exposed microsites rather than under woody canopy, and in young (< 5 years old) and intermediate-age patches (10,20 years old) rather than in mature vegetation (30,50 years old). The abundance of established woody and herb species was uncorrelated with that of the seed bank. [source]


Microalgae for oil: Strain selection, induction of lipid synthesis and outdoor mass cultivation in a low-cost photobioreactor

BIOTECHNOLOGY & BIOENGINEERING, Issue 1 2009
Liliana Rodolfi
Abstract Thirty microalgal strains were screened in the laboratory for their biomass productivity and lipid content. Four strains (two marine and two freshwater), selected because robust, highly productive and with a relatively high lipid content, were cultivated under nitrogen deprivation in 0.6-L bubbled tubes. Only the two marine microalgae accumulated lipid under such conditions. One of them, the eustigmatophyte Nannochloropsis sp. F&M-M24, which attained 60% lipid content after nitrogen starvation, was grown in a 20-L Flat Alveolar Panel photobioreactor to study the influence of irradiance and nutrient (nitrogen or phosphorus) deprivation on fatty acid accumulation. Fatty acid content increased with high irradiances (up to 32.5% of dry biomass) and following both nitrogen and phosphorus deprivation (up to about 50%). To evaluate its lipid production potential under natural sunlight, the strain was grown outdoors in 110-L Green Wall Panel photobioreactors under nutrient sufficient and deficient conditions. Lipid productivity increased from 117 mg/L/day in nutrient sufficient media (with an average biomass productivity of 0.36 g/L/day and 32% lipid content) to 204 mg/L/day (with an average biomass productivity of 0.30 g/L/day and more than 60% final lipid content) in nitrogen deprived media. In a two-phase cultivation process (a nutrient sufficient phase to produce the inoculum followed by a nitrogen deprived phase to boost lipid synthesis) the oil production potential could be projected to be more than 90 kg per hectare per day. This is the first report of an increase of both lipid content and areal lipid productivity attained through nutrient deprivation in an outdoor algal culture. The experiments showed that this marine eustigmatophyte has the potential for an annual production of 20 tons of lipid per hectare in the Mediterranean climate and of more than 30 tons of lipid per hectare in sunny tropical areas. Biotechnol. Bioeng. 2009;102: 100,112. © 2008 Wiley Periodicals, Inc. [source]


National Competitiveness: A Question of Cost Conditions or Institutional Circumstances?

BRITISH JOURNAL OF MANAGEMENT, Issue 3 2004
Edmund R. Thompson
The issue of national competitiveness is a matter of considerable importance to both managers and public policy makers alike. Business scholars reflect this importance by their annual production of international indices of country competitiveness. Nevertheless, the notion of national competitiveness is controversial and has both (i) a narrow, concise conception that relates primarily to cost conditions as determined by exchange rates, and (ii) a broader, more nebulous conception that comprises the institutional and systemic circumstances of an economy, such as legal, governmental, public policy and other factors framing countries' wider business environments. In practical managerial terms, national competitiveness is a combination of both these narrow and broad conceptions. However, exactly how important cost conditions as opposed to institutional circumstances are to national competitiveness from a practical business perspective has never been investigated and is not known. This study uses qualitative and quantitative data gathered from senior firm executives in a specimen economy to find out. Hierarchical regression analyses suggest that institutional circumstances are significantly more important than cost conditions to the competitiveness of an economy from a practical managerial viewpoint. [source]