Research project P7/31 (Research action P7)
Aquatic organisms experience stress when an external stressor moves them away from their optimum physiological conditions. Stress factors experienced by aquatic organisms include temperature changes, suboptimal nutrition, toxicants and infections. Over the past decades, knowledge about biological and ecological responses across all levels of organization (molecular to community level) to each of these stressors has been well-developed. However, the focus on single stressors is in huge contrast with reality, in which the combined action of multiple stressors on aquatic biota is the rule rather than the exception. Unfortunately, the current knowledge on the effects of multiple stressors is still too fragmented to provide a robust scientific basis and has until now focused too much on easily observable effects at the individual level. There is a lack of understanding of effects of multiple stress at lower levels (e.g., molecular, cellular, immunological, physiological mechanisms) as well as at higher levels of biological organization (i.e., population, community, ecosystem). Therefore, the primary scientific objective of the current project proposal is to investigate multiple stress in aquatic systems across multiple levels of biological organization and to verify to what extent multiple stress effects occurring at higher levels of organization can be predicted/explained based on observations of effects occurring at lower levels.
Two research disciplines in which the impact of stressors on aquatic biota are of critical importance are aquaculture (i.e. sustainable production of healthy and safe aquatic food for human consumption) and ecotoxicology (i.e. the study of the effects of toxicants on biological organisms, especially at the population, community, ecosystem level). Traditionally, both disciplines have evolved alongside each other, eventually following different research approaches and methodologies. We are convinced of the innovative benefits for both disciplines of a closer research interaction adopting and developing methodological tools across disciplines, e.g. the use of gnotobiotic culture techniques for selected species (as practiced in aquaculture research to control microbial interference), by working on the same selected species, and by applying the same standardized/inter-calibrated analytical tools. The current project proposal aims at integrating complimentary expertise (especially with regard to research tools and methodologies) between top-class research teams in aquaculture (P1, P5, P6, INT2) and in ecotoxicology (P2, P3, P4, P5, P6 and INT1). Interactions within and between both disciplines will be ensured by the planning of joint PhD studies between partner labs.
The issue of multiple stressors is currently high on the research agenda in both disciplines because it compromises their scientific basis as well as their chances of achieving their societal aims. This is mainly so because the combined effects of multiple stressors might not simply be additive, but may often be less-than-additive or more-than-additive. It is exactly those (currently unpredictable) interactions that are likely to confound the decision-making process when dealing with multiple stress in aquaculture and ecotoxicology. As it is impossible to study all possible combinations of all possible stressors, we will focus our attention on four binary combinations of four stressors which are highly relevant in aquatic systems, because these are the drivers of ecosystem health and aquaculture productivity, namely: nutrient/nutritional stress, chemical stress (toxicants), temperature stress and infection stress. Based on the knowledge obtained in this research, we will also initiate research on combinations of more than two stressors. The primary scientific objective of this research proposal will be realized through achieving the major objectives within the different work packages:
- WP1: To determine combined effects of phosphorus and metal stress on primary producers and to unravel the mechanistic basis (molecular and physiological) of the observed interactions.
- WP2: To determine combined effects of nutritional quality (not quantity) and metal stress in zooplankton and the specific role of selected nutritional components.
- WP3: To determine the combined effect of nutrients (oligotrophic vs. eutrophic) and metal stress on freshwater micro-algae and algae-zooplankton dynamics and the potential role therein of phosphorus and metal stress on primary production and its nutritional quality effects cascading through the food web.
- WP4: To determine the effect of nutritional quality, tissue lipid status and selected lipids on the response of fish cells, tissues and individuals to metal stress.
- WP5: To determine the effect of selected (nutritional) compounds on immunological functioning and infection stress of aquatic vertebrates (fish) and invertebrates (shrimp).
- WP6: To understand the molecular and physiological pathways involved in combined thermal and metal stress effects under a number of relevant exposure scenarios (simultaneous and sequential; acute and chronic).
- WP7: To determine the importance of trans-generational effects of combined thermal and metal stress and the possible role of epigenetic control therein.
- WP8: To determine the impact of thermal stress on susceptibility to infection, including possible epigenetic control.
- WP9: To determine combined and combined effects of nutrient (P), thermal and metal stress on a freshwater pelagic community structure and functioning, using microcosm exposures and ecosystem models and to investigate if complex interaction patterns can be explained/predicted from effects observed at the individual level.
- WP10: To determine the effects of combinations of multiple stressors on the genetically fully characterized model zebrafish in chronic exposure scenarios. Mapping and interpretation of effects observed at transcriptomic, proteomic and metabolomic level to reveal mode(s) of action and explore functional links between effects at molecular and organism level.
As studying multiple stressors is complex both in terms of experimental methodologies and interpretation, there is a need for excellent and well-known, reliable and reproducible model systems and technologies, including (i) the use of model organisms with completed or nearly completed genome sequence information (ii) the use of state-of-the-art ‘omics’ tools for addressing some of our specific research goals (iii) the use of axenic/gnotobiotic test systems (i.e. the elimination of microbial interference in order to reduce variability). Experimental organisms selected on the basis of availability of gnotobiotic culture systems and ‘omics’ tools and genome sequence information include:
- for the freshwater environment: the alga Chlamydomonas, the invertebrate Daphnia and the vertebrates zebra fish (Danio rerio) and rainbow trout (Oncorhynchus mykiss)
- for the marine environment: the invertebrate Artemia and the vertebrate European sea bass (Dicentrarchus labrax)
The IAP AquaStress project will be managed at two organizational levels: Network level and Work Package level:
- on a quarterly basis the IAP coordinator will convene the Management Board (consisting of the IAP coordinator and WP coordinators, with the assistance of an Advisory Committee) to review project progress and problems, encourage WP interaction and discuss strategic matters.
- Each Work Package will operate under the leadership of 1 or 2 WP coordinator(s) who will follow up the scientific activities within the WP, eventually assisted by the joint PhDs assigned for inter WP cooperation.
The IAP coordinator will organize within the framework of the project:
- a special training course on the development and use of gnotobiotic culture systems for all PhD students and staff involved in the project (organized by P1 in the summer of 2012).
- an annual special information day to review and document the various enabling technologies available at partner institutions or through their networks
- an annual full-day IAP workshop with progress reports from all WP coordinators
- a quarterly PhD student forum to stimulate scientific and social interaction across the different disciplines
an intranet service to facilitate communication, exchange scientific literature and reports, etc.
