Estimates of Phosphorus and Nitrogen Cycling by Fish Using a Bioenergetics Approach

1992 ◽  
Vol 49 (12) ◽  
pp. 2596-2604 ◽  
Author(s):  
Clifford E. Kraft
Keyword(s):  
Yellow Perch ◽  
Nutrient Recycling ◽  
Nitrogen Excretion ◽  
Age Classes ◽  
Phosphorus Excretion ◽  
P Content ◽  
Young Of The Year ◽  
Yoy Fish ◽  
Modelling Approach

A modelling approach based on bioenergetics was used to estimate the role of fish in nutrient recycling. Phosphorus excretion (PU) and nitrogen excretion by young-of-the-year (YOY) and older yellow perch (Perca flavescens) were estimated for a limnetic system: Lake Memphremagog. This model successfully predicted PU by comparison with previous estimates for yellow perch. YOY fish contributed more to limnetic nutrient cycling through excretion than older age-classes, and YOY fish could also serve as an important P sink relative to algal sinking losses. Volumetric PU by YOY yellow perch reached a maximum of 0.3 μg P∙L−1∙d−1; N excretion peaked at 10 μg N∙L−1∙d−1. The ratio of excreted N: P varied fourfold during the summer. PU estimates were also sensitive to changes in fish P content, for which few values have been reported for early life stages.

Cyclic dynamics of a yellow perch (Perca flavescens) population in an oligotrophic lake: evidence for the role of intraspecific interactions

1999 ◽  
Vol 56 (9) ◽  
pp. 1534-1542 ◽  
Author(s):  
Beth L Sanderson ◽  
Thomas R Hrabik ◽  
John J Magnuson ◽  
David M Post
Keyword(s):  
Yellow Perch ◽  
Perca Flavescens ◽  
Age Classes ◽  
Intraspecific Interactions ◽  
Important Challenge ◽  
Cyclic Dynamics ◽  
Young Of The Year ◽  
Mature Fish

Understanding the extent to which repeated oscillations in fish populations are driven by external factors or internal processes within the population is an important challenge. We document cyclic dynamics in a population of yellow perch (Perca flavescens) in oligotrophic Crystal Lake. Since 1981, we have observed three cases of cohort dominance in which two age-classes dominated the population for roughly 5 years. Young-of-the-year (YOY) perch were caught in 1981-1982, 1986-1987, and 1990-1991, whereas few to no YOY were caught during the midyears. The presence of YOY was negatively related to juvenile perch abundance and positively related to adult perch abundance. Mechanisms that may be responsible for these patterns include cannibalism of YOY by either juveniles or adults, potential for reproduction by adults, and competition between YOY and juveniles. YOY were abundant primarily in years when reproductively mature fish were in the lake, suggesting that the repeated oscillations are driven predominantly by pulses of abundant, reproductive, adult perch. As these young perch grow to juveniles, they exclude the possibility of survival by successive cohorts through cannibalistic and competitive interactions. This exclusion occurs until they themselves become reproductively mature and the cycle then repeats. Ultimately, long-term patterns in Crystal Lake suggest that cyclic dynamics are generated by intraspecific interactions.

Biological weathering in soil: the role of symbiotic root-associated fungi biosensing minerals and directing photosynthate-energy into grain-scale mineral weathering

2008 ◽  
Vol 72 (1) ◽  
pp. 85-89 ◽  
Author(s):  
J. R. Leake ◽  
A. L. Duran ◽  
K. E. Hardy ◽  
I. Johnson ◽  
D. J. Beerling ◽  
...  
Keyword(s):  
Carbon Allocation ◽  
High Surface ◽  
Turgor Pressure ◽  
High Surface Area ◽  
Volume Ratio ◽  
Mineral Weathering ◽  
Mycorrhizal Associations ◽  
P Content ◽  
Biological Weathering

AbstractBiological weathering is a function of biotic energy expenditure. Growth and metabolism of organisms generates acids and chelators, selectively absorbs nutrient ions, and applies turgor pressure and other physical forces which, in concert, chemically and physically alter minerals. In unsaturated soil environments, plant roots normally form symbiotic mycorrhizal associations with fungi. The plants provide photosynthate-carbohydrate-energy to the fungi in return for nutrients absorbed from the soil and released from minerals. In ectomycorrhiza, one of the two major types of mycorrhiza of trees, roots are sheathed in fungus, and 15—30% of the net photosynthate of the plants passes through these fungi into the soil and virtually all of the water and nutrients taken up by the plants are supplied through the fungi. Here we show that ectomycorrhizal fungi actively forage for minerals and act as biosensors that discriminate between different grain sizes (53—90 μm, 500—1000 μm) and different minerals (apatite, biotite, quartz) to favour grains with a high surface-area to volume ratio and minerals with the highest P content. Growth and carbon allocation of the fungi is preferentially directed to intensively interact with these selected minerals to maximize resource foraging.

Modelling sarcoplasmic reticulum calcium ATPase and its regulation in cardiac myocytes

2009 ◽  
Vol 367 (1896) ◽  
pp. 2181-2202 ◽  
Author(s):  
Jussi T. Koivumäki ◽  
Jouni Takalo ◽  
Topi Korhonen ◽  
Pasi Tavi ◽  
Matti Weckström
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Large Scale ◽  
Cardiac Myocyte ◽  
Model Complexity ◽  
Transport Mechanisms ◽  
Physiological Properties ◽  
Theoretical Considerations ◽  
Sarcoplasmic Reticulum Calcium ◽  
Modelling Approach

When developing large-scale mathematical models of physiology, some reduction in complexity is necessarily required to maintain computational efficiency. A prime example of such an intricate cell is the cardiac myocyte. For the predictive power of the cardiomyocyte models, it is vital to accurately describe the calcium transport mechanisms, since they essentially link the electrical activation to contractility. The removal of calcium from the cytoplasm takes place mainly by the Na + /Ca 2+ exchanger, and the sarcoplasmic reticulum Ca 2+ ATPase (SERCA). In the present study, we review the properties of SERCA, its frequency-dependent and β -adrenergic regulation, and the approaches of mathematical modelling that have been used to investigate its function. Furthermore, we present novel theoretical considerations that might prove useful for the elucidation of the role of SERCA in cardiac function, achieving a reduction in model complexity, but at the same time retaining the central aspects of its function. Our results indicate that to faithfully predict the physiological properties of SERCA, we should take into account the calcium-buffering effect and reversible function of the pump. This ‘uncomplicated’ modelling approach could be useful to other similar transport mechanisms as well.

scholarly journals Fertilization of Algal Resources By an Exotic Snail May Facilitate Invasion

2003 ◽  
Vol 27 ◽  
pp. 116-122
Author(s):  
Leslie Riley ◽  
Mark Dybdahl ◽  
Robert Hall
Keyword(s):  
Chlorophyll A ◽  
Field Experiments ◽  
Gross Primary Production ◽  
Nutrient Recycling ◽  
Algal Growth ◽  
Grazing Pressure ◽  
Nitrogen Excretion ◽  
Macroinvertebrate Communities ◽  
Negative Effects ◽  
The Difference

We studied positive and negative effects of snail consumers on their resource to determine if positive consumer effects may be facilitating invasion. Consumer- resource interactions often focus on losses to the resource, even though the resource might benefit if consumers recycle nutrients. The New Zealand mudsnail, Potamopyrgus antipodarum, an exotic in western U.S. rivers, attains high densities and dominates macroinvertebrate communities. In one well-studied river, it consumes the majority of primary productivity, cycles most nitrogen and can grow faster at higher densities. In field experiments, we tested the hypothesis that this invasive grazer stimulates algal growth via nitrogen excretion, which might explain its self-facilitation and invasiveness. Using in-stream cages subdivided into "with snails" and "without snails" sections, we examined the response of periphytic algae to snail grazing and excretion and snail excretion alone at various levels of snail biomass. We found that chlorophyll a and GPP (gross primary production) decreased as the biomass of snails increased in the grazed sections. Snail excretion, in the absence of grazing, increased both chlorophyll a and GPP, demonstrating a positive effect of snails on the resource, consistent with the nutrient recycling and enrichment hypothesis. We found no evidence for increased algal growth at intermediate snail densities in grazed treatments, as predicted by the Herbivore Optimization Curve hypothesis. However, the difference in chlorophyll a between "with snails" and "without snails" treatments increased as snail biomass increased. This suggests that snail compensation of the resource, through excretion, decreases at extremely high levels of grazing pressure and the net effect of snail grazing becomes negative. Together, these results suggest that invasiveness in some rivers may be fostered by this self-facilitation and recycling of essential nutrients.

Dietary uptake efficiency of 2,2ǐ,4,4ǐ,5,5ǐ-hexachlorobiphenyl in yellow perch and rainbow trout: Role of dietary and body lipids

1999 ◽  
Vol 18 (5) ◽  
pp. 938-945
Author(s):  
Henryka Dabrowska ◽  
Susan W. Fisher ◽  
Konrad Dabrowski ◽  
Alfred E. Staubus
Keyword(s):  
Rainbow Trout ◽  
Yellow Perch ◽  
Uptake Efficiency ◽  
Dietary Uptake

The ecology ofBartonellaspp. infections in two rodent communities in the Mazury Lake District region of Poland

Parasitology ◽  
2010 ◽  
Vol 137 (7) ◽  
pp. 1069-1077 ◽  
Author(s):  
RENATA WELC-FALĘCIAK ◽  
ANNA BAJER ◽  
JERZY M. BEHNKE ◽  
EDWARD SIŃSKI
Keyword(s):  
Bacterial Infections ◽  
Ecological Factors ◽  
Myodes Glareolus ◽  
Apodemus Flavicollis ◽  
Lake District ◽  
Age Classes ◽  
Adult Age ◽  
North Eastern ◽  
Rodent Communities

SUMMARYPrevalence and abundance ofBartonellaspp. infections were studied over a 3-year period in woodland and grassland rodents in North-Eastern Poland. Prevalence of bacterial infections was similar in the two rodent communities, with one leading host species in each habitat (46·3% inApodemus flavicollisversus 29·1% inMyodes glareolusin forest, or 36·9% inMicrotus arvalisversus 13·7% inMi. oeconomusin grassland). Prevalence/abundance of infections varied markedly across the 3 years with 2006 being the year of highest prevalence and abundance. Infections were more common during autumn months inMy. glareolusandA. flavicollis, and in juvenile and young adult (age classes 1 and 2)My. glareolusandMi. oeconomusthan in adults (age class 3). Higher prevalence and abundance ofBartonellainfections were found in maleA. flavicollisin comparison to females. These data are discussed in relation to the parasite genotypes identified in this region and with respect to the role of various ecological factors influencingBartonellaspp. infections in naturally infected host populations.

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