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The establishment of young organisms in harsh environments often requires a window of opportunity (WoO). That is, a short time window in which environmental conditions drop long enough below the hostile average level, giving the organism time to develop tolerance and transition into stable existence. It has been suggested that this kind of establishment dynamics is a noise-induced transition between two alternate states. Understanding how temporal variability (i.e. noise) in environmental conditions affects establishment of organisms is therefore key, yet not well understood or included explicitly in the WoO framework. In this paper, we develop a coherent theoretical framework for understanding when the WoO open or close based on simple dichotomous environmental variation. We reveal that understanding of the intrinsic timescales of both the developing organism and the environment is fundamental to predict if organisms can or cannot establish. These insights have allowed us to develop statistical laws for predicting establishment probabilities based on the period and variance of the fluctuations in naturally variable environments. Based on this framework, we now get a clear understanding of how changes in the timing and magnitude of climate variability or management can mediate establishment chances.

The ebb-tidal delta of the Ameland Inlet system is of great ecological importance since it hosts a variety of benthic habitats. In a pilot project, a (mega)nourishment of 5 million cubic meters of sand was carried out on the outer ebb-tidal delta. Since the strong correlation between habitat preference and sediment characteristics on the ebb-tidal delta, it is crucial to gain insight in the mechanisms governing sediment sorting in this area. To study the initial response of grain size distribution patterns, and subsequently potential changes to benthic habitats, process-based models are useful tools. Here, we present a hydro- morphodynamic model of the Ameland Inlet which is able to simulate grain size sorting patterns. Building upon previous modelling efforts, we specifically focus on the inclusion of graded sediment transport and bed stratigraphy. The simulations, here with the nourishment excluded, reveal that the model results on grain size distribution can be related well to the forcing in combination with the local depth. Particularly, it turns out that tidal motion is responsible for the sorting pattern in the deeper parts of the ebb-tidal delta, whereas the grain size distribution in the shallower, offshore parts is particularly shaped by wind and wave processes. Model sensitivity to several numerical parameters (thickness transport layer, MORFAC) is also investigated and seems relatively small, although further investigation is needed here. A preliminary comparison reveals that the model results compare qualitatively well to field data, although the shallower offshore areas seem to be predicted too coarse in the model

Tidal flats are biogeomorphic landscapes, shaped by physical forces and interaction with benthic biota. We used a metabolic approach to assess the overarching effect of bioturbators on tidal landscapes. The benthic bivalve common cockle (Cerastoderma edule) was used as model organism. The effect of C. edule on sediment resuspension was approximated as a function of the overall population metabolic rate per unit of area. We combined i) laboratory observations on how C. edule affect sediment resuspension along gradients of bioturbation activity, sediment cohesiveness and hydrodynamic force with ii) spatial data on on the natural distribution of intertidal C. edule populations. This allowed us to build an integrated model of the C. edule effect on sediment resuspension along the tidal gradient. Owing to the temperature dependence of metabolic rate, the model also accounted for seasonal variation in bioturbators activity. Laboratory experiments indicated that sediment resuspension is positively related to the metabolic rate of the C. edule population especially in cohesive sediments. Based on this observation, we predicted a clear spatial and seasonal pattern in the relative importance of C. edule contribution to sediment resuspension along a tidal transect. At lower elevations, our model indicates that hydrodynamics overrules biotic effects; at higher elevations, inter-tidal hydrodynamics should be too low to suspend bioturbated sediments. The influence of C. edule on sediment resuspension is expected to be maximal at the intermediate elevation of a mudflat, owing to the combination of moderate hydrodynamic stress and high bioturbator activity. Also, bio-mediated sediment resuspension is predicted to be particularly high in the warm season. Research into metabolic dependency of bio-mediated sediment resuspension may help to place phenomenological observations in the broader framework of metabolic theories in ecology and to formulate general expectations on the coastal ecosystem functioning.

Tropical beaches provide coastal flood protection, income from tourism, and habitat for flagship species. They urgently need protection from erosion, which is being exacerbated by changing climate and coastal development. Traditional coastal engineering solutions are expensive, provide unstable temporary solutions, and often disrupt natural sediment transport. Instead, natural foreshore stabilization and nourishment may provide a sustainable and resilient long-term solution. Field flume and ecosystem process measurements, along with data from the literature, show that sediment stabilization by seagrass in combination with sediment-producing calcifying algae in the foreshore form an effective mechanism for maintaining tropical beaches worldwide. The long-term efficacy of this type of nature-based beach management is shown at a large scale by comparing vegetated and unvegetated coastal profiles. We argue that preserving and restoring vegetated beach foreshore ecosystems offers a viable, self-sustaining alternative to traditional engineering solutions, increasing the resilience of coastal areas to climate change.

On 1-2 January 2019, an incident happened north of the Dutch Wadden Sea, in which the MSC Zoe lost part of her cargo. Among the cargo lost were plastic pellets of two different types: relatively large (several mm) high-density poly-ethylene pellets and small (0.5 mm) polystyrene granules.As part of the agreement between the Dutch government and MSC, the present study investigated whether significant damage is caused or likely to be caused to the EU protected habitats and species located in Natura 2000 sites, due to the incident with the MSC Zoe. The focus is on the detection of possible effects of ingestion of microplastics at population level. The study is based on many thousands of samples of the macrobenthos in the Wadden Sea (collected in the SIBES monitoring of NIOZ and the WOT shellfish survey of WMR) and the coastal North Sea (collected in the WOT shellfish survey of WMR), on bird counts in the Wadden Sea and North Sea (sea ducks, collected by Rijkswaterstaat and WMR) and bird counts of the Wadden Sea (collected by SOVON). All data span at least one decade. The species selected for analysis are flagship species that are protected through European directives and stand as a model for other species with similar trophic or habitat requirements, or with similar exposure to plastic particles. Only abundant species that can be analyzed with full statistical power have been selected.The best possible estimation of the spatial distribution of plastics lost by MSC Zoe did not permit to sharply delineate affected areas and use these as fixed factors in the analysis. An exploratory approach had to be used instead. The analysis looked for deviant spatial patterns between the year 2019 and the preceding (for birds also following) year and used expert judgement to evaluate whether any such patterns could be caused by plastic pollution from the MSC Zoe incident.The available data were modelled with a statistical model that took account of (1) physical cofactors (bottom shear stress due to currents and waves, grain size of the sediment, salinity) through non-linear GAM smoothers, (2) the type of statistical distribution of the data, including the number of zero observations, and (3) the spatial and temporal autocorrelations in the data. A Bayesian approach using R-INLA has been used. Possible effects of the Zoe incident were identified by comparing the unexplained (by physical factors) spatially structured variability in the populations between the samplings before and after the incident.All populations studied are characterized by relatively high variability in both space and time. Within the bird species, variability was very high for sea ducks (e.g. the Eider duck and the Scoter) and some waders, but more limited in shelducks and bar-tailed godwits. For none of the bird species, any important difference between the observations in early 2019 with those of 2018 or 2020 could be detected. Thus, no evidence for an effect of the MSC Zoe was found. Within the benthic species, recruitment processes that are highly variable from year to year and that dominate the population dynamics of the shellfish, were the prime cause of variability in the data set. Six species were each examined for abundance and biomass, yielding in total 12 analyses. Of these 12 analyses, four showed important differences between the spatial pattern in 2019 with that in 2018. In two cases, the cockle and the razor clam, this was clearly linked to a very high recruitment in 2018. In two other cases, the mussel and the Baltic tellin, the changes in spatial pattern concerned the appearance and disappearance of small-scale spatial hotspots. The important differences concerned only a few percent of the total number of comparisons. In half of the cases the values increased from 2018 to 2019. In the other half, they decreased. This was interpreted as part of the natural dynamics of these species. The study concludes that no evidence has been found for a negative influence of the MSC Zoe incident on dominant protected flagship species in the Wadden Sea and in the Dutch coastal North Sea.