Restoration of coastal ecosystem engineers that trap sediment and dampen waves has proven to be difficult, especially in the wave-exposed and eroding areas where they are needed the most. Environmental stressors, such as hydrodynamic stress and predation, can only be overcome if transplanted organisms are able to establish self-facilitating feedbacks. We investigate if the artificial lowering of multiple environmental stressors can be used to give transplanted juveniles the opportunity to form a self-sustainable system and thereby increase their long-term survival on wave-exposed and eroding shores. We designed a large field experiment using juvenile mussels (Mytilus edulis) as model species on a wave-exposed tidal flat in the Oosterschelde estuary (the Netherlands). We tested if the environmental stress caused by a high predation pressure and wave-driven dislodgement could be reduced by a combination of artificial structures such as fences (to exclude predatory crabs), attachment substrates (such as coir-net or oyster shells), and breakwaters. Despite a low overall mussel survival (29%), we found that under strong hydrodynamic conditions, experimental fences and attachment substrates increased the retention of transplanted mussel seed. However, modification of local hydrodynamic conditions using breakwaters did not improve mussel coverage preservation. Overall, this study highlights the potential of using techniques that lower multiple environmental stressors to create a window of opportunity for establishment in highly dynamic ecosystems.

Estuarine landscapes form through interactions between fluvio-coastal processes and ecological processes within the boundaries imposed by hard substrate layers and man-made dikes and dams. As estuaries are ecologically valuable areas, monitoring and quantification of trends in habitats is needed for objective comparison and management. However, datasets of tidal flat and saltmarsh habitats along entire estuaries are scarce. The objective was to compare trends of biogeomorphological areas and habitat transitions along three estuaries in the Netherlands and assess whether these are generally comparable or mainly determined by system-specific histories. We present data for these estuaries obtained by automated classification of false-color aerial imagery. The automated method allows objective mapping of entire estuaries at unprecedented resolution. The estuaries are dominated by subtidal areas and tidal flats. The tidal flats have similar area along the estuaries while saltmarsh area decreases. Collective lengths of ecologically important transitions between saltmarsh, low-energy tidal flats and water differ more between the estuaries. These variations are due to presence of mid-channel bars and shore-connected embayments. Saltmarsh area is mainly determined by the different formation and embankment histories of the estuaries, embayments and side-branches. Much of the past saltmarsh flanking the estuaries was lost due to past land reclamation. In one system, ecologically important low-energy tidal flats are reduced by a sudden decrease of tidal amplitude, causing increase of subtidal area at the cost of intertidal area. Large areas of high-energy tidal flats in one estuary remain unexplained. The automated method can be applied in other estuaries, provided that high-quality areal imagery is available. Extensions of the data to other estuaries would allow for system-scale trend comparison between estuaries of ecologically relevant biogeomorphological characteristics.

ACHTERGRONDIn de Oosterschelde is door de aanleg van de stormvloedkering (1986) sprake van 'zandhonger'. Het getij is verminderd, waardoor het evenwicht tussen erosie en sedimentatie is verstoord. Bij rustig weer bouwt het intergetijdengebied zich niet meer voldoende op, terwijl er wel afbraak optreedt tijdens stormen. Dit sediment verdwijnt in de geulen.Door de zandhonger neemt het areaal en de droogvalduur van het intergetijdengebied af, dit heeft negatieve effecten voor de ecologie: het areaal droogvallende platen en slikken neemt af, alsmede de duur dat deze platen droogvallen tijdens laagwater. Hierdoor hebben vogels die voor hun voedsel van deze gebieden afhankelijk zijn steeds minder foerageerareaal ter beschikking en wordt ook de tijd dat hun voedsel, de bodemdieren, bereikbaar zijn steeds kleiner. Daarnaast zorgen zandplaten, slikken en schorren voor een natuurlijke demping tegen golven. Dijken met een voorland (slikken en platen) worden minder belast. Door de erosie van de slikken en platen, wordt de levensduur van dijken verkort of moeten dijken zwaarder worden aangelegd. Naast de gevolgen voor natuur en veiligheid, heeft de zandhonger ook een negatieve invloed op de landschappelijke waarden en sociaaleconomische belangen in het gebied.De Oosterschelde is een Natura-2000 gebied en in dit verband heeft de overheid de verantwoordelijkheid om de natuurdoelen te behouden, te herstellen en eventueel te verbeteren. Voor elk Natura-2000 gebied gelden instandhoudingsdoelen, die aangeven welke leefgebieden en welke soorten (planten en dieren) behouden of hersteld moeten worden. De maatregelen die nodig zijn om de instandhoudingsdoelen te realiseren worden opgenomen in het Beheerplan Deltawateren. Voor het formuleren van deze maatregelen is kennis nodig.

Abstract. Spatiotemporal geomorphological mapping of intertidal areas is essential for understanding system dynamics and provides information for ecological conservation and management. Mapping the geomorphology of intertidal areas is very challenging mainly because spectral differences are oftentimes relatively small while transitions between geomorphological units are oftentimes gradual. Also, the intertidal areas are highly dynamic. Considerable challenges are to distinguish between different types of tidal flats, specifically, low and high dynamic shoal flats, sandy and silty low dynamic flats, and mega-ripple areas. In this study, we harness machine learning methods and compare between machine learning methods using features calculated in classical Object-Based Image Analysis (OBIA) vs. end-to-end deep convolutional neural networks that derive features directly from imagery, in automated geomorphological mapping. This study expects to gain us an in-depth understanding of features that contribute to tidal area classification and greatly improve the automation and prediction accuracy. We emphasise model interpretability and knowledge mining. By comparing and combing object-based and deep learning-based models, this study contributes to the development and integration of both methodology domains for semantic segmentation.