1 Introduction ................................................ 19
1.1 Overview ............................................... 19
1.2 Background ............................................. 19
1.2.1 Direct and indirect effects of pesticides ....... 19
1.2.2 Combined effects of pesticides and abiotic
environmental factors and species interactions .. 21
1.2.3 Individual vs. community level effects .......... 22
1.2.4 Use of outdoor microcosms in pesticide risk
assessment to assess community-level effects
of pesticides ................................... 26
1.2.5 Impact of climate change on aquatic ecosystems .. 28
1.3 Aim of the thesis ...................................... 28
1.3.1 Test system and substance used in the present
studies ......................................... 29
2 Environmental context determines community sensitivity of
freshwater Zooplankton to a pesticide ....................... 41
2.1 Abstract ............................................... 42
2.2 Introduction ........................................... 42
2.3 Materials and methods .................................. 44
2.3.1 Experimental design ............................. 44
2.3.2 Artificial outdoor pond system .................. 45
2.3.3 Application of esfenvalerate and monitoring ..... 45
2.3.4 Macroinvertebrates and environmental
parameters ...................................... 47
2.3.5 Data analyses ................................... 48
2.4 Results ................................................ 49
2.4.1 Esfenvalerate exposure dynamic .................. 49
2.4.2 Environmental parameters ........................ 49
2.4.3 Effects on the structure of the
macroinvertebrate community ..................... 50
2.4.4 Limitations of the community approach ........... 53
2.5 Discussion ............................................. 55
3 Community sensitivity to a xenobiotic can be predictable -
An evidence from a cross-Eurasia experiment ................. 63
3.1 Abstract ............................................... 64
3.2 Main text .............................................. 64
4 Two stressors and a community - Effects of hydrological
disturbance and a toxicant on freshwater Zooplankton ........ 77
4.1 Abstract ............................................... 78
4.2 Introduction ........................................... 78
4.3 Materials and methods .................................. 79
4.3.1 Experimental design ............................. 79
4.3.2 Water level fluctuations ........................ 80
4.3.3 Application and monitoring of esfenvalerate ..... 81
4.3.4 Zooplankton and environmental parameters ........ 82
4.3.5 Data analyses ................................... 83
4.4 Results ................................................ 85
4.4.1 Dynamics of esfenvalerate exposure .............. 85
4.4.2 Abiotic parameters and total density of
Zooplankton ..................................... 85
4.4.3 Effects on the community structure .............. 89
4.4.4 Effects on single-species dynamics .............. 90
4.5 Discussion ............................................. 94
4.5.1 General ......................................... 94
4.5.2 Esfenvalerate exposure .......................... 94
4.5.3 Relevance and sensitivity of the test system .... 95
4.5.4 Mechanisms underlying the combined effects ...... 95
4.5.5 Implications for basic ecology .................. 97
4.5.6 Implications for ecological risk assessment ..... 97
4.6 Acknowledgements ....................................... 98
5 Environmental stressors can enhance the development of
community tolerance to a toxicant .......................... 109
5.1 Abstract .............................................. 110
5.2 Introduction .......................................... 110
5.3 Materials and methods ................................. 111
5.3.1 Experimental design ............................ 111
5.3.2 Water level fluctuations ....................... 112
5.3.3 Esfenvalerate application and monitoring ....... 113
5.3.4 Zooplankton and environmental parameters ....... 113
5.3.5 Data analyses .................................. 114
5.4 Results ............................................... 115
5.4.1 Effects on community structure ................. 115
5.4.2 Population-level effects ....................... 117
5.5 Discussion ............................................ 118
5.5.1 General ........................................ 118
5.5.2 Mechanisms underlying the enhancement of
community tolerance ............................ 119
5.5.3 Community tolerance in higher organisms ........ 121
5.6 Conclusions ........................................... 121
6 Discussion ................................................. 125
6.1 Summary of the results ............................... 125
6.1.1 Environmental context determines community
sensitivity of freshwater Zooplankton to
a pesticide (Chapter 2) ........................ 125
6.1.2 Community sensitivity to a xenobiotic can be
predictable - A cross-Eurasia experiment
revealed strong and consistent modulations
(Chapter 3) .................................... 126
6.1.3 Two stressors and a community - Effects of
hydrological disturbance and a toxicant on
freshwater Zooplankton. (Chapter 4) ............ 127
6.1.4 Environmental stressors can enhance the
development of community tolerance to
a toxicant (Chapter 5) ......................... 129
6.2 Discussion of the major results and implications for
pesticide risk assessment ............................. 130
6.2.1 Influence of additional stressors on the
sensitivity of Zooplankton communities to
pesticides ..................................... 130
6.2.2 Abiotic factors ................................ 131
6.2.3 Species interactions ........................... 132
6.3 Importance of the present results for the future
ecological risk assessment of pesticides .............. 133
6.3.1 Representativity of the present outcomes for
the field ...................................... 133
6.3.2 Significance of the present results in terms
of on-going climate change ..................... 134
6.3.3 Implications for pesticide risk assessment
using outdoor micro- or mesocosms .............. 135
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