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Contains fulltext : 290193.pdf (Publisher’s version ) (Open Access)

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Coastal ecosystem functioning often hinges on habitat-forming foundation species that engage in positive interactions (e.g. facilitation and mutualism) to reduce environmental stress. Seagrasses are important foundation species in coastal zones but are rapidly declining with losses typically linked to intensifying global change-related environmental stress. There is growing evidence that loss or disruption of positive interactions can amplify coastal ecosystem degradation as it compromises its stress mitigating capacity. Multiple recent studies highlight that seagrass can engage in a facultative mutualistic relationship with lucinid bivalves that alleviate sulphide toxicity. So far, however, the generality of this mutualism, and how its strength and relative importance depend on environmental conditions, remains to be investigated. Here we study the importance of the seagrass-lucinid mutualistic interaction on a continental-scale using a field survey across Europe. We found that the lucinid bivalve Loripes orbiculatus is associated with the seagrasses Zostera noltii and Zostera marina across a large latitudinal range. At locations where the average minimum temperature was above 1 °C, L. orbiculatus was present in 79% of the Zostera meadows; whereas, it was absent below this temperature. At locations above this minimum temperature threshold, mud content was the second most important determinant explaining the presence or absence of L. orbiculatus. Further analyses suggest that the presence of the lucinids have a positive effect on seagrass biomass by mitigating sulphide stress. Finally, results of a structural equation model (SEM) support the existence of a mutualistic feedback between L. orbiculatus and Z. noltii. We argue that this seagrass-lucinid mutualism should be more solidly integrated into management practices to improve seagrass ecosystem resilience to global change as well as the success of restoratio

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 inter

Contains fulltext : 240937.pdf (Publisher’s version ) (Open Access)

25 februari 2022, Contains fulltext : 249328.pdf (Publisher’s version ) (Open Access)

01 juni 2021, Contains fulltext : 235953.pdf (Publisher’s version ) (Open Access)

17 mei 2021, Contains fulltext : 239385.pdf (Publisher’s version ) (Open Access)

Combining foreshore ecosystems like saltmarshes and mangroves with traditional hard engineering structures may offer a more sustainable solution to coastal protection than engineering structures alone. However, foreshore ecosystems, are rapidly degrading on a global scale due to human activities and climate change. Marsh-edges could be protected by using connected ecosystems, such as shellfish reefs and seagrass beds, which can trap and stabilize sediments, thereby reducing hydrodynamics loads on the saltmarsh edge. In our study, we aimed to test the effect of large-scale biodegradable artificial reefs on tidal flat accretion and/or stabilization. We hypothesized that the structures would attenuate waves and trap sediment. For this, a large-scale experiment was conducted on the tidal flats of the Dutch Wadden Sea, by installing biodegradable artificial reefs along 630 m. Waves, sediment dynamics and sediment properties around the structures were monitored over three years. Our results demonstrate that intact structures attenuated circa 30% of the wave height with water levels below 0.5 m. Variability in wave-attenuation increased when the wind direction was parallel to the structures/foreshore. Sediment dynamics were variable due to the exposed nature of the location and environmental heterogeneity because of the landscape-scale set-up. We observed local sediment accretion up to 11 cm, however the effect did not expand beyond 10 m from the landward edge of the structures and up to 10 cm scouring was also found. Additionally, near sediment properties were not affected by the presence of the artificial reefs. Long-term effects could not be assessed due to the degradation of the structures during the experimental period. In general, we conclude that artificial reefs have the potential to attenuate waves and trap sediment on tidal flats. However, to benefit connected foreshore ecosystems like salt marshes, an even larger implementation scale and the use of more resistan

Contains fulltext : 206091.pdf (publisher's version ) (Open Access)

Coastal exploitation and human‐mediated modifications have markedly altered the community composition and functioning of coastal wetlands worldwide. Although recent work has shown that harnessing positive density‐dependent feedbacks can greatly enhance the recovery of habitat‐modifying species in degraded wetlands, the role of these intraspecific feedbacks in explaining the persistence of altered, unfavorable plant communities remains largely unexplored. Here, we experimentally tested whether intraspecific facilitation may explain the persistence of common reed (Phragmites australis) in human‐modified coastal wetlands. We performed a full‐factorial mesocosm experiment crossing low‐density pioneer versus high‐density established development stages with saline (20 psu) versus freshwater conditions. Results showed a clear shift in plant growth response from intraspecific competition under freshwater conditions to self‐facilitation in saline treatments. We identified two positive feedback mechanisms enabling the established treatment to overcome salinity stress: (1) Enhanced root oxygenation of the sediment at higher plant density decreased accumulation and intrusion of phytotoxic sulfide, and (2) density‐dependent rainwater infiltration into the soil lowered salinity in the dense root mat, preventing salt stress. Our study demonstrates that intraspecific facilitation can be an important factor in explaining the persistence of Phragmites australis in coastal wetlands. We emphasize the importance of integrating positive interactions in coastal restoration but argue that they should either be harnessed when restoring vegetation or broken when eradication of nontarget species is the management objective.

Contains fulltext : 75572.pdf (publisher's version ) (Closed access)

Contains fulltext : 29282.pdf (publisher's version ) (Closed access)