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Coastal vegetated ecosystems including mangroves, seagrasses, and salt marshes are often shaped by positive plant–environment feedbacks. Plants improve their own living conditions with increasing patch size and density by attenuating hydrodynamics and stabilizing sediments. As these habitat modifications are critical for survival and growth, the positive density-dependent nature of these feedbacks can lead to establishment thresholds for young plants in absence of mature conspecifics. Although feedback strength is known to depend on hydrodynamic exposure and plant traits (e.g. stiff versus flexible stems), it remains unclear how 1) opposing morphological plant traits affect establishment in contrasting environments, and 2) whether trait plasticity influences establishment success. Here, we investigate this by transplanting two tidal species with opposing growing strategies – Spartina anglica forms tussocks of stiff stems while Zostera noltii forms patches of stress-avoiding flexible shoots – from two different donor sites in eight experimental locations. Results show that the survival and growth of both species was most successful at field locations with diverging environmental characteristics, while overall survival was highest for Z. noltii. Mainly, S. anglica survival was highest at locations with high organic matter and silt content and higher elevation relative to the tidal amplitude. In contrast, Z. noltii survival was highest at locations with larger grainsize and lower relative elevations. Furthermore, despite initial differences in plant traits between the two donor sites of Z. noltii, we found no effects of donor origin. Contrastingly, we found a significant effect of donor origin on S. anglica growth, even though transplants from the two donor sites showed no initial trait differences. Collectively, these results suggest that the stress-tolerance strategy of S. anglica hampers establishment in exposed conditions, whereas the stress-avoiding Z. noltii a

Foundation species that modify their habitat can facilitate other species, including other foundation species. Most studies focus solely on a single foundation species, overlooking such facilitation cascades. In this study, we investigated the interactions between the two coastal foundation species Mytilus edulis (blue mussel) and Lanice conchilega (sand mason worm). We investigated whether these species engage in facilitative interactions or if their association simply reflects a shared ecological niche on the soft-sediment intertidal flats of the Dutch Wadden Sea. To do so, we performed species distribution modeling, manipulative field experiments, and field surveys. We found a positive association between both foundation species, with a 2.45 times higher occurrence of both species compared to a random distribution. In addition, these species partially occupied the same ecological niche. We demonstrated that L. conchilega provided settlement substrate for M. edulis spat, increasing densities by 400 times compared to bare plots. Furthermore, M. edulis reefs facilitated L. conchilega occurrence in the wake of the reef. Biogenic reef development revealed that this interspecific facilitation resulted in spatial habitat heterogeneity. Therefore, we conclude that interspecific facilitation can significantly enhance the occurrence of these two important intertidal foundation species. Acknowledgment of such complex facilitation interactions has an untapped potential for improving the success of restoration and conservation programs.

Coastal ecosystems provide vital services, but human disturbance causes massive losses. Remaining ecosystems are squeezed between rising seas and human infrastructure development. While shoreline retreat is intensively studied, coastal congestion through infrastructure remains unquantified. Here we analyse 235,469 transects worldwide to show that infrastructure occurs at a median distance of 392 meter from sandy shorelines. Moreover, we find that 33% of sandy shores harbour less than 100 m of infrastructure-free space, and that 23–30% of this space may be lost by 2100 due to rising sea levels. Further analyses show that population density and gross domestic product explain 35–39% of observed squeeze variation, emphasizing the intensifying pressure imposed as countries develop and populations grow. Encouragingly, we find that nature reserves relieve squeezing by 4–7 times. Yet, at present only 16% of world’s sandy shores have a protected status. We therefore advocate the incorporation of nature protection into spatial planning policies., Coastal Engineering

Reef-forming species form integral aspects of coastal ecosystems, but are rapidly degrading world-wide. To mitigate these declines, nature managers increasingly rely on the restoration of habitat-structuring, reef-forming species by, for example, introducing artificial reefs that may directly function as complex reef habitat. Since the use of biodegradable structures to restore biogenic reefs is becoming a popular technique, its effectiveness as reef habitat must be assessed. Therefore, we examine the trophic complexity on experimental large-scale biodegradable artificial reefs using food web network analysis. We placed biodegradable artificial reefs on soft-sediment intertidal flats in the Dutch Wadden Sea in a large-scale (~650 m) and 2.5-year-long experiment. We compared food web networks and biodiversity indicators between biodegradable reefs and bare controls and quantified species composition inside and near the artificial reef community to assess the expansion of the reef community. During 2.5 years, we observed that artificial reefs changed food web networks compared to bare controls: in species richness (+76%), link density (the number of interactions per species; +15%) and the fraction of basal species (species of lowest trophic level; +40%), but lowered the connectance: the realized fraction of all possible links between species (−33%). Their effects on food web networks increased over time with a higher species richness (+22%) and more complex food web (link density +13%) on the artificial reef 2.5 years after deployment compared to 1.5 years. However, the effects of the reefs did not extend beyond the reef structures; the species composition and biodiversity of macrozoobenthos near the reefs were comparable to the control. Synthesis and applications. This study shows that biodegradable artificial reefs offer an effective tool for the restoration of food web complexity and biodiversity of intertidal soft-sediment systems. However, application needs to be

This dataset contains the data obtained and utilized for the manuscript: On the use of large-scale biodegradable artificial reefs for intertidal foreshore stabilization. The aim was to study the effect of biodegradable artificial reefs, aimed at mussel bed restoration, on i) wave attenuation, ii) soil properties and iii) soil elevation. In 2017 biodegradable artificial reefs were deployed in the tidal flats from Griend, a small island in the dutch Wadden Sea. Waves, sediment properties and soil elevation were monitored until 2019. The dataset is divided in 3 parts: wave analysis, soil properties analysis and elevation change analysis. The analysis is divided in different steps, and each step has a corresponding folder with the input data needed for the analysis., This dataset contains the data obtained and utilized for the manuscript: On the use of large-scale biodegradable artificial reefs for intertidal foreshore stabilization. The aim was to study the effect of biodegradable artificial reefs, aimed at mussel bed restoration, on i) wave attenuation, ii) soil properties and iii) soil elevation. In 2017 biodegradable artificial reefs were deployed in the tidal flats from Griend, a small island in the dutch Wadden Sea. Waves, sediment properties and soil elevation were monitored until 2019. The dataset is divided in 3 parts: wave analysys, soil properties analysis and elevation change analysis. The analysis is divided in different steps, and each step has a corresponding folder with the input data needed for the analysis.

In biogeomorphic landscapes, plant traits can steer landscape development through plant‐mediated feedback interactions. Interspecific differences in clonal expansion strategy can therefore lead to the emergence of different landscape organisations. Yet, whether landscape‐forming plants adopt different clonal expansion strategies depending on their physical environment remains to be tested. Here, we use a field survey and a complementary mesocosm approach to investigate whether sediment deposition affects the clonal expansion strategy employed by dune‐building marram grass individuals. Our results reveal a consistent shift in expansion pattern from more clumped, Brownian‐like, movement in sediment‐poor conditions, to patchier, Lévy‐like, movement under high sediment supply rates. Additional model simulations illustrate that the sediment‐dependent shift in movement strategies induces a shift in optimisation of the cost–benefit relation between landscape engineering (i.e. dune formation) and expansion. Plasticity in expansion strategy may therefore allow landscape‐forming plants to optimise their engineering ability depending on their physical landscape.