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Project: Wadden engine - A human-driven regime shift through the loss of ecosystem engineers: conseque...

Project details

Acronym : Wadden engine
Full project name : A human-driven regime shift through the loss of ecosystem engineers: consequences for the trophic structure and recovery potential of the Wadden Sea ecosystem
Initiating organisation : NIOZ Royal Netherlands Institute for Sea Research, Texel
Project leader : B.D.K.H. Eriksson
Supporting organisation(s)NIOZ Royal Netherlands Institute for Sea Research, Texel
NIOZ Royal Netherlands Institute for Sea Research, Yerseke
Financing :
Project number : 83908310
Start date : Jan 01, 2009
End date : Dec 31, 2013


Programme :ZKO - Carrying Capacity: Line 3 - National Programme Sea and Coastal Research (ZKO) - Carrying Capacity: Line 3 - Hypothesis-driven Research
Main project :-


Description :

Across the world, human-dominated marine ecosystems are experiencing an accelerating loss of populations and species, with a strong risk of permanently impairing key ecosystem functions and recovery potential. In The Netherlands, the Wadden Sea ecosystem experienced similar deterioration over the last few centuries due to strong intensification of human activities, causing the extinction of many species, strong modification of ecological and landscape processes, and large alterations in the carrying capacity for the remaining characteristic bird, fish, mammal and invertebrate species.
The Wadden Sea has been subject of numerous scientific studies focused on specific landscape-forming (e.g., sedimentation, hydrodynamics), biogeochemical and ecosystem processes (as primary production), as well as on several individual species and their specific ecological interactions (e.g., knots-bivalves). This would suggest that overall ecosystem functioning and trophic structure are well understood, allowing confident predictions on future harvesting of marine resources and optimal locations for restoration of key ecological phenomena, as mussel banks. Unfortunately, this is not true. Surprisingly, no study has yet been successful in putting available knowledge on the interactions among all of the different trophic groups together; jointly with the associated changes in the key environmental factors. The few large-scale, mostly conceptual/theoretical studies on ecosystem functioning of the Wadden Sea that are available, are based on observations combined with modeling only. There is clear need for further identification of the processes that determine ecosystem functioning at large spatial scales, and experimental validation of mechanisms and predictions.
We hypothesize that this lack of a synthetic framework of the functioning of the Wadden Sea is due to an important, but still poorly understood property of soft-bottom intertidal communities: the dependence between the dominant benthic consumers low in the food web (as bivalves and worms), and their main environmental determinants (as sediment texture and stability, water turbulence and geomorphology). Species with such a bi-directional interplay with their environmental factors are called ecosystem engineers. We propose the novel hypothesis that two types of ecosystem engineers can potentially dominate the same habitat in the Wadden Sea. The first group contains filter-feeding reef builders (bivalves) that stabilize the sediment, and promote the local settlement of fine-grained material. The second group consists of deposit feeders (as lugworms) that destabilize the sediment and promote resuspension of fine-textured sediments. Through data compilation, modelling and experiments we will test the hypothesis that overexploitation of the Wadden Sea has induced a regime shift from a spatially heterogeneous state dominated of sediment-stabilizing ecosystem engineers to a more homogenous state dominated by sediment-destabilizing ecosystem engineers. The thought that ecosystem engineers, such as mussels and sea grasses, have historically played a key role in maintaining biodiversity in the Wadden Sea, is not new. What is however new is our planned full reconstruction and experimental testing of how the structure of the food web depends on the abundance and distribution of these ecosystem engineers, and how the food web in turn determines the abundance of specific engineering species. This has important consequences for understanding changes in carrying capacity, as sometimes irreversible responses are expected to further reductions in fishing, to climate change and to reduction of nutrient loads.
We will use existing long-term data collected by our research groups, historical and novel spatial data and GIS methods to analyze them, modeling and large-scale field experiments to test the two main ideas/hypothesis indicated in bold above. We emphasize the importance of our experimental approach, despite its costs. A combination of just monitoring and modeling is insufficient to identify multiple stable states and regime shifts in ecosystem as it does not allow the discrimination against alternative hypotheses, as ''unseen'' sudden changes in external forcing factors, or fixed, imposed abiotic heterogeneity causing patchiness Deliverables of the program will include maps of predicted (potential) occurrence of key ecosystem engineers, expected shifts in spatial distributions under alternative scenarios of use, experimental data that allow validation of the hypothesis on regime shifts in ecosystem engineers, and a full construction of the Wadden Sea food web, with identification of the main drivers of the different species groups.