TIPPING points, biodiversity, resilience and ecosystem services: PONDs as model systems – TIPPINGPOND

Ponds and shallow lakes have played a key role in the development of theory on regime shifts in ecosystems (Scheffer 2009), where resilience to environmental change is broken when a threshold disturbance is surpassed. Upon eutrophication or with temperature increase, ponds and lakes may shift from a clearwater to a turbid state with an associated decline in biodiversity (Declerck et al. 2005) and ecosystem services. Small inland waters are very important for regional biodiversity (Williams et al. 2004) and, due to their high number, have an important contribution to ecosystem services such as carbon storage (Giller et al. 2004; Downing et al. 2006; Tranvik et al. 2009). Ponds are very convenient model systems for ecological studies, being numerous and relatively easy to monitor and manipulate (De Meester et al. 2005). We here capitalize on these assets and the available ecological knowledge on ponds and lakes to engage in a combined survey and manipulative study to identify (1) the link between extant biodiversity and resilience to disturbance in natural systems (Ives and Carpenter 2007; Isbell et al. 2011)and(2)early warning signs of regime shifts that may cause a strong decline in ecosystem services(Scheffer et al. 2009).

Our approach is threefold:(A)We will engage in a large-scale field experiment capitalizing on extensive existing background information. In a large set of ponds that have been characterized for their abiotic environment(Declerck et al. 2006)and biota(11 organism groups; De Bie et al. ms), we will deploy enclosures in which we expose the resident communities to well-defined stressors (nutrient increase mimicking eutrophication; change in temperature) and monitor resilience of ecosystem functioning and community composition as a function of biodiversity and original state of the system. In a more limited number of systems, we will carry out a more detailed monitoring through time of the dynamics of different biotic and abiotic variables in response to experimental disturbances to help identifying early warning signals.(B)We will validate the results of our field experiment with data from field surveys on fish culture ponds and shallow lakes in Belgium, Sweden and France, and will link biodiversity to measures of ecosystem functioning.(C)Finally,we will use highly standardized laboratory systems (Planktotrons) to validate hypotheses generated from the field data.

The legacy of TIPPINGPOND will be: (1) Insights into the link between biodiversity, initial state and resilience to disturbance, providing key information to safeguard ecological integrity of freshwater habitats. These insights will be validated in a broad range of standing waters, informing predictions and generate policy value beyond ponds as model systems. (2) A deeper understanding of tipping points and early warning signs for regime shifts in aquatic systems, of crucial value for policy makers.

Ponds and wetlands are crucial to regional biodiversity and are important in nature conservation strategies. Our stakeholders include policy makers, nature conservation organisations, and institutes of applied biodiversity research, but also stakeholders of the socio-technical network linked to commercially exploited ponds (pond managers and owners, fish cooperatives, local politicians). Nature conservation organisation Natuurpunt (Belgium), representatives of fish pond networks (France) and HaV (Sweden) have expressed strong interest in our planned research.