@article{DenouxMartinCreuzburgKoussoroplisetal.2017,
  author    = {Denoux, Clemence and Martin-Creuzburg, Dominik and Koussoroplis, Apostolos-Manuel and Perriere, Fanny and Desvillettes, Christian and Bourdier, Gilles and Bec, Alexandre},
  title     = {Phospholipid-bound eicosapentaenoic acid (EPA) supports higher fecundity than free EPA in Daphnia magna},
  series = {Journal of plankton research},
  volume    = {39},
  journal   = {Journal of plankton research},
  publisher = {Oxford Univ. Press},
  address   = {Oxford},
  issn      = {0142-7873},
  doi       = {10.1093/plankt/fbx037},
  pages     = {843 -- 848},
  year      = {2017},
  abstract  = {Nutrition bioassays in which polyunsaturated fatty acids (PUFA)-deficient diets were supplemented with free long-chain PUFA (>= C20) consistently revealed positive effects on somatic growth and fecundity of Daphnia. However, free PUFA are hardly available in natural diets. In general, PUFA are bound to other lipids, especially to phospholipids and triglycerides. Here, we evaluate the potential of free and phospholipid-bound dietary eicosapentaenoic acid (EPA) to support somatic growth and fecundity of Daphnia magna. In a growth experiment, supplementation of a C20 PUFA-deficient diet with free or phospholipid-bound EPA improved somatic growth rates of D. magna equally. However, the increase in fecundity was significantly more pronounced when phospholipid-bound EPA was provided. Free and phospholipid-bound EPA were provided in the same concentrations in our experiment, suggesting that the allocation to reproduction-related processes is affected differently by phospholipid-bound PUFA and free PUFA. Our finding stresses the need to consider the distribution of dietary PUFA in different lipid classes to gain a better understanding of how PUFA influence life history traits of Daphnids in the field.},
  language  = {en}
}
@article{GabsiHammersWirtzGrimmetal.2014,
  author    = {Gabsi, Faten and Hammers-Wirtz, Monika and Grimm, Volker and Schaeffer, Andreas and Preuss, Thomas G.},
  title     = {Coupling different mechanistic effect models for capturing individual- and population-level effects of chemicals: Lessons from a case where standard risk assessment failed},
  series = {Ecological modelling : international journal on ecological modelling and engineering and systems ecolog},
  volume    = {280},
  journal   = {Ecological modelling : international journal on ecological modelling and engineering and systems ecolog},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0304-3800},
  doi       = {10.1016/j.ecolmodel.2013.06.018},
  pages     = {18 -- 29},
  year      = {2014},
  abstract  = {Current environmental risk assessment (ERA) of chemicals for aquatic invertebrates relies on standardized laboratory tests in which toxicity effects on individual survival, growth and reproduction are measured. Such tests determine the threshold concentration of a chemical below which no population-level effects are expected. How well this procedure captures effects on individuals and populations, however, remains an open question. Here we used mechanistic effect models, combining individual-level reproduction and survival models with an individual-based population model (IBM), to understand the individuals' responses and extrapolate them to the population level. We used a toxicant (Dispersogen A) for which adverse effects on laboratory populations were detected at the determined threshold concentration and thus challenged the conservatism of the current risk assessment method. Multiple toxicity effects on reproduction and survival were reported, in addition to effects on the F1 generation. We extrapolated commonly tested individual toxicity endpoints, reproduction and survival, to the population level using the IBM. Effects on reproduction were described via regression models. To select the most appropriate survival model, the IBM was run assuming either stochastic death (SD) or individual tolerance (IT). Simulations were run for different scenarios regarding the toxicant's effects: survival toxicity, reproductive toxicity, or survival and reproductive toxicity. As population-level endpoints, we used population size and structure and extinction risk. We found that survival represented as SD explained population dynamics better than IT. Integrating toxicity effects on both reproduction and survival yielded more accurate predictions of population effects than considering isolated effects. To fully capture population effects observed at high toxicant concentrations, toxicity effects transmitted to the F1 generation had to be integrated. Predicted extinction risk was highly sensitive to the assumptions about individual-level effects. Our results demonstrate that the endpoints used in current standard tests may not be sufficient for assessing the risk of adverse effects on populations. A combination of laboratory population experiments with mechanistic effect models is a powerful tool to better understand and predict effects on both individuals and populations. Mechanistic effect modelling thus holds great potential to improve the accuracy of ERA of chemicals in the future. (C) 2013 The Authors. Published by Elsevier B.V. All rights reserved.},
  language  = {en}
}
@article{SperfeldMartinCreuzburgWacker2012,
  author    = {Sperfeld, Erik and Martin-Creuzburg, Dominik and Wacker, Alexander},
  title     = {Multiple resource limitation theory applied to herbivorous consumers Liebig's minimum rule vs. interactive co-limitation},
  series = {Ecology letters},
  volume    = {15},
  journal   = {Ecology letters},
  number    = {2},
  publisher = {Wiley-Blackwell},
  address   = {Malden},
  issn      = {1461-023X},
  doi       = {10.1111/j.1461-0248.2011.01719.x},
  pages     = {142 -- 150},
  year      = {2012},
  abstract  = {There is growing consensus that the growth of herbivorous consumers is frequently limited by more than one nutrient simultaneously. This understanding, however, is based primarily on theoretical considerations and the applicability of existing concepts of co-limitation has rarely been tested experimentally. Here, we assessed the suitability of two contrasting concepts of resource limitation, i.e. Liebigs minimum rule and the multiple limitation hypothesis, to describe nutrient-dependent growth responses of a freshwater herbivore (Daphnia magna) in a system with two potentially limiting nutrients (cholesterol and eicosapentaenoic acid). The results indicated that these essential nutrients interact, and do not strictly follow Liebigs minimum rule, which consistently overestimates growth at co-limiting conditions and thus is not applicable to describe multiple nutrient limitation of herbivorous consumers. We infer that the outcome of resource-based modelling approaches assessing herbivore population dynamics strongly depends on the applied concept of co-limitation.},
  language  = {en}
}