h1

TY  - THES
AU  - Kulkarni, Devdutt
TI  - A combined approach of experiments and modelling for the implementation of freshwater copepods in ecological risk assessment
CY  - Aachen
M1  - RWTH-CONV-144042
SP  - 129 S. : graph. Darst.
PY  - 2014
N1  - Zsfassung in dt. und engl. Sprache
N1  - Aachen, Techn. Hochsch., Diss., 2014
AB  - Standardized test guidelines used in ecological risk assessment (ERA) consider a relatively small set of test species. For instance in most standard risk assessments, Daphnia magna is the only required species representing freshwater invertebrates which assumes that tests with such standard species in combination with relatively large assessment factors are protective for other species in the field. Standard test species are usually selected based on intrinsic sensitivity as well as practicability i.e. the ease of rearing. However, species in the field may employ variable life-history strategies which may have consequences concerning the ecological vulnerability of these species to toxicants. The variability in the intrinsic sensitivity of different species can be assessed by testing additional species and constructing species sensitivity distributions while ecological vulnerability can be addressed using community-level studies e.g. mesocosms and ecological modelling. Copepods are important animals in the aquatic food chain. They are predators of other plankton and act as prey for fish, consequently enabling the transfer of energy and substances though the food chain. Copepods, owing to their complex life-history strategies, are potentially vulnerable organisms and therefore, useful as ecological indicators of risk. For marine risk assessment, copepods are now being considered and an OECD test guideline for bottom-dwelling harpacticoid copepods is under way. However, in freshwater ecotoxicology, copepods are largely ignored except in mesocosm studies. To facilitate the consideration of freshwater copepods in higher-tier ERA there is a need for the development of robust test methods and models to facilitate extrapolation between environmental conditions, exposure patterns and species. This thesis delivers the basics of a combined approach of laboratory experiments and modelling for better consideration of freshwater copepods in ERA. With a particular focus on plant protection products, an exhaustive literature review was carried out to identify a representative species of freshwater copepods, which could be a good compromise between a potentially vulnerable relevant species as well as a good laboratory species. The literature review revealed Mesocyclops leuckarti as a good representative species for freshwater copepods for ecotoxicological studies. The suitability of this selected species was demonstrated by establishing a stable laboratory culture. To demonstrate the intrinsic sensitivity of this species, a model chemical, triphenyltin (TPT), was used to conduct acute toxicity tests with this species in the laboratory. Experiments confirmed M. leuckarti to be sensitive to TPT with the naupliar stages showing a higher sensitivity compared to older stages. Furthermore, various experiments to study the life-cycle processes of this species namely- feeding, development, reproduction, survival, etc. were conducted using different food sources and feeding regimes. To facilitate the extrapolation of individual-level effects to more relevant population-level responses, an individual-based model (IBM) was developed for this selected species. The model was parameterised based on parameters of eco-physiological processes obtained from laboratory experiments. The toxicokinetics and toxicodynamics of TPT were described and modelled using the General Unified Threshold model for Survival (GUTS) based on the aforementioned laboratory toxicity tests. The combined model was used to analyse the population-level effects TPT under different feeding regimes. The main outcome of model simulations was the identification of the synergistic effect of cannibalism as well as TPT stress on the nauplii as the cause of increased susceptibility of M. leuckarti populations under toxic exposure. Furthermore, a case study wherein the ecological sensitivity of M. leuckarti was compared to D. magna and Chaoborus crystallinus by means of population modelling was carried out. It was observed that population-level sensitivities of the three species used in the case study were higher than those on the individual level. Also, the species that was least sensitive at the individual level (C. crystallinus) was found to be most sensitive on the population level. Furthermore, M. leuckarti was less sensitive than D. magna at the individual level and more sensitive than D. magna at the population level. This thesis confirmed the relevance and practicability of copepods for ERA as well as the significance of population modelling in predicting population-level responses from individual-level data. This approach of combining laboratory experiments and population modelling of a representative vulnerable species to allow mechanistic extrapolation to the population level and to other exposure patterns can also be applied to other taxa in order to build up a set of test species and models useful for refined and more realistic ERA.
KW  - Umwelttoxikologie (SWD)
KW  - Pflanzenschutzmittel (SWD)
KW  - Modellierung (SWD)
KW  - Ruderfußkrebse (SWD)
LB  - PUB:(DE-HGF)11
UR  - https://publications.rwth-aachen.de/record/229066
ER  -