Energy-based Modeling to Study Population Growth Rate and Production for the Midge Chironomus riparius in Ecotoxicological Risk Assessment

Ecotoxicology ◽  
2004 ◽  
Vol 13 (7) ◽  
pp. 647-656 ◽  
Author(s):  
A. R. R. P�ry ◽  
R. Mons ◽  
J. Garric
Keyword(s):  
Risk Assessment ◽  
Growth Rate ◽  
Population Growth ◽  
Population Growth Rate ◽  
Chironomus Riparius ◽  
Ecotoxicological Risk Assessment ◽  
Ecotoxicological Risk ◽  
Study Population

scholarly journals Population growth rate as a basis for ecological risk assessment of toxic chemicals

2002 ◽  
Vol 357 (1425) ◽  
pp. 1299-1306 ◽  
Author(s):  
Valery E. Forbes ◽  
Peter Calow
Keyword(s):  
Risk Assessment ◽  
Growth Rate ◽  
Life Cycle ◽  
Population Growth ◽  
Ecological Risk ◽  
Population Growth Rate ◽  
Toxic Chemicals ◽  
Ecological Risks ◽  
Individual Level ◽  
Rate Analysis

Assessing the ecological risks of toxic chemicals is most often based on individual–level responses such as survival, reproduction or growth. Such an approach raises the following questions with regard to translating these measured effects into likely impacts on natural populations. (i) To what extent do individual–level variables underestimate or overestimate population–level responses? (ii) How do toxicant–caused changes in individual–level variables translate into changes in population dynamics for species with different life cycles? (iii) To what extent are these relationships complicated by population–density effects? These issues go to the heart of the ecological relevance of ecotoxicology and we have addressed them using the population growth rate as an integrating concept. Our analysis indicates that although the most sensitive individual–level variables are likely to be equally or more sensitive to increasing concentrations of toxic chemicals than population growth rate, they are difficult to identify a priori and, even if they could be identified, integrating impacts on key life–cycle variables via population growth rate analysis is nevertheless a more robust approach for assessing the ecological risks of chemicals. Populations living under density–dependent control may respond differently to toxic chemicals than exponentially growing populations, and greater care needs to be given to incorporating realistic density conditions (either experimentally or by simulation) into ecotoxicological test designs. It is impractical to expect full life–table studies, which record changes in survival, fecundity and development at defined intervals through the life cycle of organisms under specified conditions, for all relevant species, so we argue that population growth rate analysis should be used to provide guidance for a more pragmatic and ecologically sound approach to ecological risk assessment.

scholarly journals Biological scaling in green algae: the role of cell size and geometry

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Helena Bestová ◽  
Jules Segrestin ◽  
Klaus von Schwartzenberg ◽  
Pavel Škaloud ◽  
Thomas Lenormand ◽  
...  
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Population Growth Rate ◽  
Internal Diffusion ◽  
Scaling Exponent ◽  
Power Scaling ◽  
Nutrient Distribution ◽  
Metabolic Scaling ◽  
Key Factor ◽  
Size And Morphology

AbstractThe Metabolic Scaling Theory (MST), hypothesizes limitations of resource-transport networks in organisms and predicts their optimization into fractal-like structures. As a result, the relationship between population growth rate and body size should follow a cross-species universal quarter-power scaling. However, the universality of metabolic scaling has been challenged, particularly across transitions from bacteria to protists to multicellulars. The population growth rate of unicellulars should be constrained by external diffusion, ruling nutrient uptake, and internal diffusion, operating nutrient distribution. Both constraints intensify with increasing size possibly leading to shifting in the scaling exponent. We focused on unicellular algae Micrasterias. Large size and fractal-like morphology make this species a transitional group between unicellular and multicellular organisms in the evolution of allometry. We tested MST predictions using measurements of growth rate, size, and morphology-related traits. We showed that growth scaling of Micrasterias follows MST predictions, reflecting constraints by internal diffusion transport. Cell fractality and density decrease led to a proportional increase in surface area with body mass relaxing external constraints. Complex allometric optimization enables to maintain quarter-power scaling of population growth rate even with a large unicellular plan. Overall, our findings support fractality as a key factor in the evolution of biological scaling.

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