EU network of mesocosms facilities for research on marine and freshwater ecosystems open for global collaboration.

Task 9.2

Task 9.1 Transfer knowledge about key environmental challenges (WP2), best practices harmonization (WP3) and site specific environmental traits (WP6) into transnational joint research activities
Task 9.2 Performing joint experiments on key scientific questions along major environmental and bio-geographical gradients

Performing joint experiments on key scientific questions along major environmental and bio-geographical gradients (Lead: AU, Month 24-48)

Task 9.2 aims at investigating key challenges across two important environmental gradients, from freshwater to marine waters, and from European Arctic to Mediterranean systems. Such a task is only possible by effectively bundling the individual site-specific expertise of the consortium within joined research actions, thereby yielding synergistic results that cannot be achieved by individual institutions. The experimental approach will make use of the AQUACOSM network and will employ standardized methods (WP3 & 4) and new experimental setups (WP7 & 8). For initial actions and to ensure an efficient start of the approach, we will focus on environmental aspects that have been already identified as future key challenges for marine and freshwater systems within the context of global change research. One of these aspects is that global change is altering the movement of materials across landscapes, which is affecting functioning and stability of ecosystems. There is growing evidence that terrestrial ecosystems are exporting more dissolved organic carbon (DOC) to aquatic ecosystems than they did just a few decades ago (Clark et al., 2010). This “browning” phenomenon will alter the chemistry, physics, and biology of water bodies in complex and difficult-to-predict ways. Browning will directly influence primary production by higher light attenuation creating shading, thereby reducing primary production. At the same time, browning will increase bacterial production by supplying DOC, thereby shifting basal energy mobilization within aquatic food webs in complex and not easy to predict ways (Ask et al., 2009). Initial food-web configuration and traits will therefore largely affect the response of aquatic systems to browning. Experiments at different sites provide a unique opportunity to elucidate how browning will affect the stability and functioning of aquatic ecosystems and interact with local species pools and ecosystem characteristics.

We will conduct a joint research activity demonstration, by investigating the effects of increasing DOC exports from terrestrial ecosystems into aquatic systems along two important environmental gradients. We will perform manipulations of DOC loading at 3 sites along a salinity gradient from freshwater to marine and along 3 sites along a latitudinal gradient from Arctic to Mediterranean. We will install (in close cooperation with WP7 and WP8) standardized floatable mesocosm systems and instrumentation at all sites, including 9 mesocosms of 2m diameter and 3m depth equipped with modern sensor technologies. Experimental manipulations at all sites will include different degrees of enrichment with an already tested and well characterized terrestrial DOC source. Thereby we keep comparability between experiments as high as technically possible.

Subtask 2.1: Salinity gradients (Lead: AU, Co-Lead: SYKE, Contributors: SYKE, AU, Month 24-40)

This task is the first approach of successfully investigating “browning” with joint research actions including a limited number of partners at 3 sites covering a large salinity gradient in the same climate zone. Experiments will be performed at a freshwater site in Denmark (AU), a brackish site in Finland (Tvärminne) and a full marine site in Norway (Hopavagn, Sletvik Field Station, NTNU Trondheim). Hopavagn is a wind and wave protected bay north of Trondheim, characterized by a high degree of exchange with the open North Atlantic. The experiments at Sletvik Field Station will demonstrate the ability of the consortium to extend its activity to a larger network and also perform experiments at important and relevant sites that do not have a permanent installation of mesocosm systems. Additionally, Sletvik Field Station, NTNU Trondheim, is a member within the European HYDRALAB+ consortium; the planned experiments will thereby ensure a close interaction between these two large European research networks.

Building on experience from a highly standardised cross-European mesocosm experiment on shallow freshwater lakes, headed by AU (Landkildehus et al, 2014) in the FP7 REFRESH project, the experiments will allow testing basic strategies within a well arranged consortium of a small number of partners that are covering the important and challenging gradient from freshwater to full marine waters. These experiments will act as a proof of principle for the surplus value of cross-aquatic environment joint research activities within the AQUACOSM consortium. Experiences from subtask 2.1 will greatly improve strategies to further extend the joint research actions of the AQUACOSM consortium.

Subtask 2.2: Latitudinal gradients (Lead: UNI, Contributors: HCMR, M42-M48)

Subtask 2.2 is a logical extension of subtask 2.1. Based on knowledge achieved from subtask 2.1, we will further improve cooperation strategies to extend the above described experiments along a salinity gradient (9.2.1) to a marine latitudinal gradient from Arctic to Mediterranean systems. The two endpoints of the latitudinal gradient will be an Arctic site at Svalbard and a Mediterranean site at Crete, the midpoint is the experiment at the full marine site (Sletvik Field Station) already done within 9.2.1. The pilot test of the research strategy at Svalbard (NyAlesund) will be especially relevant as many partners will join, demonstrating the effectiveness of the transnational coordination abilities of the consortium to perform joint mesocosm experiments in important but difficult – and therefore under-investigated – environments such as Arctic waters, where already existing systems such as on most other sites are not available. The strategy performing a pilot project in Svalbard will be strongly based on the knowledge and techniques obtained in Subtask 2.1, WP7 and WP8; the experimental infrastructure has to withstanding harsh conditions.

Subtask 2.2 will demonstrate the ability of the consortium to develop successful research strategies to investigate global change related key research questions from the Arctic to the Mediterranean