When:   4-5 September 2014
Where:   TU-HH, Hamburg, Germany
Details and
Registration (till 30 April):

The overarching goal of the workshop is to identify and define system states and conditions for naturally and anthropogenically triggered transitions in the physical and biogeochemical states of tidal estuaries and their environmental and socio-economic consequences.


Concept for a new DFG Priority Programme (SPP):

“System states and transitions of tidal estuaries”

Estuaries – semi-enclosed bodies of water where riverine freshwater mixes with marine waters – are the epitome of transition zones in the Earth system. Estuarine systems bracket the continuum from the non-tidal river end to the coastal regions of freshwater influence (ROFIs). Interfacing land and sea, they are hotbeds of physical mixing and chemical transformations (many being microbially mediated) andprovide habitat for a multitude of biological communities. High-frequency and high-amplitude temporal and spatial variability is an inherent feature in all estuaries. Here, (semi-) diurnal, long-term and directed variability in external forcing interact with human-induced changes which shift baselines of natural variability to create a complex and often unpredictable interplay of reactions.

Deepening of navigational channels to allow ships of ever increasing size access to up-estuarine harbours and narrowing for the purpose of coastal protection and land reclamation are the most extreme human interventions to tidal estuaries. These abrupt geometrical alterations and, together with modified river loads (eutrophication/oligotrophication), have led to transitions in the physical-sedimentary parameter space in the past in several European estuaries. The most prominent implications of such transitions were shifts towards hyper-turbid conditions with dramatic consequences for the estuarine ecosystem, including extensive hypoxia. Although conceptual and analytical models give some hints about the functioning of such transitions, a process-based quantitative understanding is lacking. Given this deficit, ecological consequences of human interventions to estuaries are literally unpredictable. Moreover, the projected societal benefits (safer coasts, more agricultural land, more prosperous harbours) may be cancelled out by detrimental effects such as extensive hypoxia, increased harbor sedimentation, reduced ecosystem services or ever increasing dredging costs. We consider here estuaries in their environmental and socio-economic context as part of a feedback cycle between socio-economic drivers and so far unpredictable environmental reactions.

We propose therefore a DFG priority programme that responds to the world-wide increasing human pressure on estuarine systems. The long-term system changes due to human impacts are often unforeseeable, due to gaps in integrated system understanding, which can now be closed by combining new scientific methods and opportunities. By carrying out program-oriented interdisciplinary and integrated research on the national scale in connection to international efforts, the proposed PP will bring together the currently dispersed German estuarine research community.