A.V. de Groot

Measuring sedimentation in tidal marshes: a review on methods and their applicability in biogeomorphological studies

It is increasingly recognised that interactions between geomorphological and biotic processes control the functioning of many ecosystem types as described e.g. by the ecological theory of ecosystem engineering. Consequently, the need for specific bio-geomorphological research methods is growing recently. Much research on bio-geomorphological processes is done in coastal marshes. These areas provide clear examples of ecosystem engineering as well as other bio-geomorphological processes: Marsh vegetation slows down tidal currents and hence stimulates the process of sedimentation, while vice versa, the sedimentation controls ecological processes like vegetation succession. This review is meant to give insights in the various available methods to measure sedimentation, with special attention to their suitability to quantify bio-geomorphological interactions. The choice of method used to measure sedimentation is important to obtain the correct parameters to understand the biogeomorphology of tidal salt marshes. This review, therefore, aims to be a tool for decision making regarding the processes to be measured and the methods to be used. We, subdivide the methods into those measuring suspended sediment concentration (A), sediment deposition (B), accretion (C) and surface-elevation change (D). With this review, we would like to further encourage interdisciplinary studies in the fields of ecology and geomorphology.

Modeling the biogeomorphic evolution of coastal dunes in response to climate change

Coastal dunes form in many parts of the world the first flood defense line against the sea. To study effects of climate change on coastal dune evolution, we used a cellular model of dune, beach and vegetation development (DUBEVEG). The model was calibrated and validated against field measurements of the Dutch coast, showing good performance for 10 year simulations. A sensitivity analysis showed that dune size and morphology are most sensitive to the rate of aeolian input and wave dissipation. Finally, 100-year climate-change scenarios were run to establish the impacts of sea-level rise and changes in vegetation growth rate on dune evolution. The results are in good agreement with conceptual models of dune evolution. Sea-level rise largely determines the direction of dune evolution: the rate of rising controls whether dunes are able to preserve their height or sand volume while migrating landward. The effect of changing vegetation growth rates, resulting from climate change, is most manifest in dune response to large disturbances. If vegetation is removed halfway into the simulation, vegetation growth rate determines whether a foredune will re-vegetate and recover its height. Low vegetation growth rates result in mobile dunes that lose sand. The good agreement between observations and predictions indicates that the model successfully incorporates the suite of biogeomorphic and marine processes involved in dune building.

Measuring and modeling coastal dune development in the Netherlands

In the past couple of years, new coastal-dune research has sprung up in the Netherlands. In this paper, we give an overview of ongoing projects at Wageningen UR, Deltares, TU Delft and UTwente: how these are connected and what type of questions are addressed. There is an increasing demand for the understanding and prediction of coastal dune dynamics, both on the short (year) and long (100 years) term. We approach this from a variety of angles: scientific and applied, short-term and long-term, data-driven and model-based, biotic and abiotic, process-based and rule-based, and focused on components and integrated. We give examples of results and end with a discussion of the benefits of this integrated approach.

ESTERIFICATION OF 4-METHYLOCTANOIC ACID WITH POLYETHYLENE GLYCOL AT DIFFERENT aw

Novozym 435® (immobilized Candida antarctica lipase B) was used to esterify 4-methyloctanoic acid with polyethylene glycols (PEGs) of different molecular weights (PEG-600, PEG-3000 and PEG-20000) at different water activities. A system composed of 4-methyloctanoic acid and PEG-600 was monophasic, except at a high water activity. Even at a water activity of 0.8, PEG was still converted to its mono- or diester, which proves the unique character of PEG. The PEG-esters accumulated in the apolar phase.

Opslibbing en vegetatie kwelder Ameland-Oost; Jaarrapportage 2013

Dit onderzoek is onderdeel van de lopende monitoring van de effecten van de bodemdaling door gaswinning. De observaties over 2013 passen binnen de tot nu toe geobserveerde trends in maaiveldhoogte en vegetatieontwikkeling als gevolg van de bodemdaling op Ameland (Dijkema et al., 2011) en de natuurlijke variatie in opslibbing en vegetatieontwikkeling. De vegetatieontwikkeling heeft op een aantal meetpunten een regressie naar een lagere vegetatiezone of veranderingen binnen een zone laten zien. Dit werd vaak veroorzaakt door een afname van gewone zoutmelde en het innemen van de open plekken door andere soorten, zoals bv. klein schorrenkruid.