Editorial: Coastal and marine environments responses to changes in fluvial environment: biotic and abiotic interplay

Caroline Fiório Grilo^1*Kyssyanne Samihra Oliveira^2*Diego Barcellos^3*

• ¹Technische Universiteit Delft, Delft, Netherlands
• ²Universidade Federal do Espirito Santo, Vitoria, Brazil
• ³Universidade Federal de Sao Paulo - Campus Diadema, Diadema, Brazil

solutions, with the aim of fostering innovative strategies for sustainable management of interconnected fluvial and marine environments. For instance, the beneficial use of dredged sediments for habitat restoration is gaining attention to support ecosystem resilience while maintaining navigable waterways. Unlike static hard infrastructure, NbS is dynamic and may be adapted to changing conditions such as sea level rise and storms, although the thresholds governing its performance under dynamic environmental conditions are still not fully understood. Despite these advantages, hard infrastructure remains the default option due to established engineering criteria and longstanding reliance.Withing this context, 4 articles featured in this Research Topic discuss ongoing efforts about NbS and other related topics. For instance, Davis et al. (2024) provides a compelling example of NbS implementation through the restoration of Swan Island, Maryland. The project aimed to enhance resilience to sea-level rise, maintaining the island's wave-breaking function, and increasing habitat diversity by using dredged sediments to build elevation gradients to support local vegetation. A comprehensive monitoring program assessed vegetation dynamics, sediment properties, topography, and hydrodynamics to evaluate restoration success. The containment barrier failed due to design limitations based on outdated hydrodynamic data, emphasizing the need for site-specific environmental characterization and continuous monitoring. Ongoing erosion further demonstrated the importance of hybrid (green-gray) approaches that combine ecological restoration with engineering measures when natural resilience is already compromised. Vegetation monitoring revealed strong species-specific responses to elevation and burial, highlighting the need to select stress-tolerant species for successful restoration. Yet, biodiversity assessments were limited, excluding broader ecosystem components such as phytoplankton and benthic communities, underscoring the importance of multi-trophic monitoring. Finally, the absence of detailed sediment composition data constrained understanding of bioticabiotic interactions, demonstrating that future NbS efforts must integrate comprehensive sediment characterization, adaptive design, and ecosystem-scale evaluation to ensure sustainable outcomes.Another interesting topic from this issue addresses the intermittent rivers and ephemeral streams (IRES), which occurs in regions with low precipitation and are important to provide ecosystems services along the fluvial perimeter and for coastal systems that depends upon these rivers. The work of Silva et al. (2024) demonstrated the fate of nutrients (such as phosphorus, P), which are vital for several ecosystems, along an intermittent river in the semiarid region of Brazil (State of Ceará). The authors sampled sediments and water to investigate seasonality in these drylands across the following hydroperiods: dry, rewetting, and flow. They found changes in P contents in sediments and water across the different hydroperiods and that P was closely correlated with organic matter from sediments. Additionally, IRES have been poorly investigated, mostly regarding sediments, soils, and water, although they exert an important function as a drain or source of nutrients for the downstream ecosystems, which impacts the land-sea continuum.Groundwater is important for the functioning of several ecosystems, impacting the fluvial and aftermath the estuarine ecosystems. Models to predict, understand, and prevail future scenarios of groundwater pumping (GWP) and water table depth (WTD) are still challenging and under development. The work from Kim et al. (2024) presents models including a regression-enhanced random forest (RERF) aimed to forecast WTD changes related to GWP in New Jersey State (United States), a State that contains terrestrial and coastal areas, bringing insights regarding water resources from land to sea. The authors demonstrated that the best variables for model predictions included the following: the average of the long-term WTD, the water balance of precipitation minus evapotranspiration (PME), and variations in the slope of the landscape. This study provides important information for decision-makers regarding the management to integrate continental and coastal areas subjected to GWP and WTD fluctuations and its impacts for the fluvial and marine systems.Complementing these biophysical perspectives, the study by Islam et al. (2025) addresses the social dimensions of coastal transformations, linking physical shoreline changes to the resilience of human livelihoods. Focusing on the Ganga-Brahmaputra-Meghna (GBM) delta in Bangladesh, the authors combined long-term geospatial analyses of shoreline migrationspanning the past 9,000 years-with satellite imagery from 1972 to 2020 and interviews with local experts to assess the impacts of climate-driven erosion, sediment deposition, and salinity intrusion on coastal communities. The study highlights that the combined influence of the major river systems, Ganga/Padma, Brahmaputra/Jamuna, and Meghna, particularly at the mouth of the Padma River, plays a key role in shaping the coastline and driving its continuous migration. This dynamic shoreline shift and land loss have intensified community vulnerability, prompting migration, livelihood diversification, and the adoption of community-led adaptation practices such as mangrove restoration and integrated water management. The study emphasizes that strengthening resilience in deltaic and coastal regions requires not only engineering or ecological interventions but also policies that integrate local knowledge, cultural values, and participatory governance to ensure equitable adaptation under accelerating climate change.Together, the four studies show that sustainable management of fluvial, estuarine, and coastal systems requires integrating biophysical and social perspectives. From sediment-based restoration (Davis et al., 2024), nutrient cycling in intermittent rivers (Silva et al., 2024), and groundwater modelling (Kim et al., 2024) to socio-environmental adaptation in deltaic regions (Islam et al., 2025), all emphasize the interdependence of land-sea processes and the need for continuous monitoring, adaptive design, and predictive tools under climate change. They also highlight that technological and ecological solutions must be complemented by community participation and local knowledge to enhance resilience. Collectively, these works reinforce that cross-disciplinary approaches and that Nature-based Solutions are essential to achieve ecological sustainability and social equity across interconnected riverine, estuarine, and coastal environments.