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Ecosystems are shaped by physical, chemical, and biological drivers, which affect the quality and quantity of basal energy sources, with impacts that cascade to higher trophic levels. In coastal, shelf, and marine habitats, terrestrial-derived organic matter (ter-OM) can be a key driver of ecosystem structure and function. Climate change is expected to alter land–ocean connectivity in many regions, with a broad range of potential consequences for impacted ecosystems, particularly in the coastal zone. The benthic compartment is an important link between the large organic carbon pools stored on land and the marine environment. At the same time, the macrofauna plays a key role in the processing, biological uptake, and fate of ter-OM in the aquatic environment, with implications for coastal ecosystem functioning, benthic–pelagic coupling, carbon burial, and biogeochemical cycles. However, information about relationships between land–ocean connectivity (including ter-OM loads) and coastal benthic community responses remains spread across disciplines, and a broad perspective on the potential impacts of a changing climate is still missing. Here, we explore the interplay between benthic macrofaunal communities and ter-OM through a paired narrative and research weaving analysis, which combines systematic mapping and bibliometric analysis. The review describes the past development and status of the research field as well as the lack of information in some geographical regions and habitats worldwide. We highlight the role of macrofauna in carbon cycling and the growing evidence that ter-OM plays a key role in the structure and function of benthic communities, not strictly limited to estuarine habitats. Climate change poses challenges for the prediction of future ter-OM fluxes and potential macrofauna responses to this additional stressor, thus requiring new methodological approaches (e.g., multimarker approaches for OM characterization) and long-term monitoring programs across different habitats and spatiotemporal scales.

Sedimentary dynamics in the Palamós Canyon are influenced by river inputs and storm resuspension, as well as by bottom trawling on the canyon flanks. In this study, we estimate recent sediment deposition patterns along the canyon axis using the excess activity concentration of the short-lived radiotracer [sup.234]Th (half-life of 24.1 days). Sediment cores were obtained at various locations along the canyon axis from a depth of approximately 800 m to 2100 m in June 2023 and August 2024. Excess [sup.234]Th ([sup.234]Th[sub.xs]) was detected in all sampled sites with variable penetration depths (0.5–3.5 cm). [sup.234]Th[sub.xs]-derived estimations of mixing rates decreased downcanyon from up to 15.6 cm[sup.2] y[sup.−1] at the canyon head (~800 m) to negligible mixing at the canyon mouth (~2100 m). [sup.234]Th[sub.xs] inventories, a proxy of recent sediment deposition, were high (1800–3490 Bq m[sup.−2]) at the canyon head and at the upper canyon (~1400 m) close to fishing grounds and decreased downcanyon (82–694 Bq m[sup.−2]) at the lower canyon (~1800 m) and canyon mouth. Inventories varied 2-fold across years presumably attributed to enhanced riverine and bottom trawling sediment fluxes. Similar [sup.234]Th-derived sediment deposition patterns can be found in submarine canyons worldwide, highlighting the value of this radiotracer for sedimentary dynamics studies in such complex environments.

A high percentage of the litter entering the marine environment is assumed to come from land-based sources, but freshwater litter inputs have not been quantified. The lack of data and knowledge on fluxes of riverine litter to the sea, i.e., quantities and sources, hinders implementation of appropriate environmental regulations and mitigation measures. Estimations of riverine litter inputs require a consistent and harmonized approach to gather comparable data. The visual observation of floating litter on rivers has been selected as a simple and robust methodology for litter monitoring. A collaborative network of 36 institutions has been set-up for large spatial coverage. Currently 58 rivers are being observed regularly. A tablet computer application has been developed for the monitoring of floating macro litter (> 2.5 cm) to harmonize the visual observations. The application allows recording of the observed items, their size and geo-position data during monitoring sessions. A common agreed list of litter items and size ranges is used, providing a common harmonized approach for data collection and reporting. © 2017 González-Fernández and Hanke.

Coastal waters have strong gradients in dissolved organic matter (DOM) quantity and characteristics, originating from terrestrial inputs and autochthonous production. Enclosed seas with high freshwater input therefore experience high DOM concentrations and gradients from freshwater sources to more saline waters. The brackish Baltic Sea experiences such salinity gradients from east to west and from river mouths to the open sea. Furthermore, the catchment areas of the Baltic Sea are very diverse and vary from sparsely populated northern areas to densely populated southern zones. Coastal systems vary from enclosed or open bays, estuaries, fjords, archipelagos and lagoons where the residence time of DOM at these sites varies and may control the extent to which organic matter is biologically, chemically or physically modified or simply diluted with transport off-shore. Data of DOM with simultaneous measurements of dissolved organic (DO) nitrogen (N), carbon (C) and phosphorus (P) across a range of contrasting coastal systems are scarce. Here we present data from the Roskilde Fjord, Vistula and Öre estuaries and Curonian Lagoon; four coastal systems with large differences in salinity, nutrient concentrations, freshwater inflow and catchment characteristics. The C:N:P ratios of DOM of our data, despite high variability, show site specific significant differences resulting largely from differences residence time. Microbial processes seemed to have minor effects, and only in spring did uptake of DON in the Vistula and Öre estuaries take place and not at the other sites or seasons. Resuspension from sediments impacts bottom waters and the entire shallow water column in the Curonian Lagoon. Finally, our data combined with published data show that land use in the catchments seems to impact the DOC:DON and DOC:DOP ratios of the tributaries most.

Arctic coasts, which feature land-ocean transport of freshwater, sediments, and other terrestrial material, are impacted by climate change, including increased temperatures, melting glaciers, changes in precipitation and runoff. These trends are assumed to affect productivity in fjordic estuaries. However, the spatial extent and temporal variation of the freshwater-driven darkening of fjords remain unresolved. The present study illustrates the spatio-temporal variability of suspended particulate matter (SPM) in the Adventfjorden estuary, Svalbard, using in-situ field campaigns and ocean colour remote sensing (OCRS) via high-resolution Sentinel-2 imagery. To compute SPM concentration (CSPMsat), a semi-analytical algorithm was regionally calibrated using local in-situ data, which improved the accuracy of satellite-derived SPM concentration by ~20% (MRD). Analysis of SPM concentration for two consecutive years (2019, 2020) revealed strong seasonality of SPM in Adventfjorden. Highest estimated SPM concentrations and river plume extent (% of fjord with CSPMsat > 30 mg L−1) occurred during June, July, and August. Concurrently, we observed a strong relationship between river plume extent and average air temperature over the 24 h prior to the observation (R2 = 0.69). Considering predicted changes to environmental conditions in the Arctic region, this study highlights the importance of the rapidly changing environmental parameters and the significance of remote sensing in analysing fluxes in light attenuating particles, especially in the coastal Arctic Ocean.

Rivers are major pathways for litter to enter the ocean, especially plastic debris. Yet, further research is needed to improve knowledge on rivers contribution, increase data availability, refine litter origins, and develop relevant solutions to limit riverine litter inputs. This study presents the results of three years of aquatic litter monitoring on the Adour river catchment (southwest of France). Litter monitoring consisted of collecting all litter stranded on river banks or stuck in the riparian vegetation in defined areas identified from cartographic and hydromorphological analyses, and with the support of local stakeholders. Litter samples were then sorted and counted according to a list of items containing 130 categories. Since 2014, 278 litter samplings were carried out, and 120,632 litter items were collected, sorted, and counted. 41% of litter could not be identified due to high degradation. Food and beverage packaging, smoking-related items, sewage related debris, fishery and mariculture gear, and common household items represented around 70% of identifiable items. Overall, the present study contributes to our knowledge of litter sources and pathways, with the target of reducing the amounts entering the ocean. The long-term application of this monitoring is a way forward to measure societal changes as well as assess effectiveness of measures.

Introduction: This study investigated the variability and main drivers of the carbonate system in Gayraca Bay and Chengue Bay, located on the northeastern Caribbean coast of Colombia, through monthly measurements of partial pressure of CO2 (pCO2), pH, total alkalinity (TA), and dissolved inorganic carbon (DIC) from 2017 to 2022. Statistical analyses and Taylor series decomposition were employed to determine the seasonal and interannual contributions of sea surface temperature, salinity, TA, and DIC to changes in pCO2, pH, and calcium carbonate saturation state (Ω).

Microplastics (MPs) and nanoplastics (NPs) have emerged as pervasive pollutants across different aquatic systems on a global basis, yet integrated assessments linking wastewater, riverine, and marine environments remain scarce. The present study provides the first comprehensive evaluation of MPs in three interconnected aquatic matrices of Northern Greece, namely surface seawater from the Thermaic Gulf, surface freshwater from the Axios River, and influent and effluent wastewaters from the Thessaloniki WWTP (Sindos). During two sampling periods spanning late 2023 and spring 2024, suspected MPs were isolated, morphologically classified by stereomicroscopy, and chemically characterized through pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS). MPs were ubiquitously detected in all substrates, exhibiting distinct spatial and compositional patterns. Seawater samples displayed moderate concentrations (1.5–4.8 items m−3) dominated by fibers and fragments, while riverine samples contained slightly higher levels (0.5–2.5 items m−3), enriched in fibrous forms and polyolefins (PE, PP). Wastewater influents showed the highest MP abundance (78–200 items L−1; 155.6–392.3 µg L−1), decreasing significantly in effluents (11–44 items L−1; 27.8–74.3 µg L−1), corresponding to a removal efficiency of 81–87.5%, being the first indicative removal efficiencies in a Greek WWTP. Among the different polymers detected, polyethylene, polypropylene, and poly(ethylene terephthalate) were identified as the most prevalent polymers across all matrices. Interestingly, a shift toward smaller size classes (125–500 µm) in effluents indicated in-plant fragmentation processes, while increased concentrations during December coincided with increased rainfall, highlighting the influence of hydrological conditions on MP fluxes. The combined morphological and polymer-specific approach provides a holistic zunderstanding of MP transport from inland to marine systems, establishing essential baseline data for Mediterranean environments and reinforcing the need for integrated monitoring and mitigation strategies.

Arctic coastal zones serve as a sensitive filter for terrigenous matter input onto the shelves via river discharge and coastal erosion. This material is further distributed across the Arctic by ocean currents and sea ice. The coastal regions are particularly vulnerable to changes related to recent climate change. We compiled a pan-Arctic review that looks into the changing Holocene sources, transport processes and sinks of terrigenous sediment in the Arctic Ocean. Existing palaeoceanographic studies demonstrate how climate warming and the disappearance of ice sheets during the early Holocene initiated eustatic sea-level rise that greatly modified the physiography of the Arctic Ocean. Sedimentation rates over the shelves and slopes were much greater during periods of rapid sea-level rise in the early and middle Holocene, as a result of the relative distance to the terrestrial sediment sources. However, estimates of suspended sediment delivery through major Arctic rivers do not indicate enhanced delivery during this time, which suggests enhanced rates of coastal erosion. The increased supply of terrigenous material to the outer shelves and deep Arctic Ocean in the early and middle Holocene might serve as analogous to forecast changes in the future Arctic.

BACKGROUND AND OBJECTIVES: The concentration of particulate organic carbon serves as a key indicator of biological productivity within the euphotic zone. Estimating its variability delivers key perspectives on the overarching trends in. The objective of this study is to explore the distribution of particulate organic carbon over time and space, as well as to model its fluctuations in Jakarta Bay, thereby enriching the knowledge of organic carbon dynamics in coastal ecosystems. METHODS: Monthly moderate-resolution imaging spectroradiometer satellite data for surface particulate organic carbon and chlorophyll-a during 2011 to 2023 periods were collected. In addition, seasonal in-situ data of salinity, sea surface temperature, dissolved oxygen, nitrate, and phosphate, were examined to assess the potential impact of natural processes on the fluctuations of particulate organic carbon variability in this bay. The seasonal autoregressive integrated moving average model was selected for particulate organic carbon forecast. FINDINGS: The concentration of particulate organic carbon varied between approximately 230 and 340 within the observed range. Significant concentrations were noted in the nearshore areas owing to the river's outflow into the bay. The seasonal variation indicates that the highest concentrations occur during the north west monsoon. Meanwhile, the lowest concentrations were observed during the Inter-monsoon II. In spite of the considerable variability, the trend in particulate organic carbon is almost constant (Coefficient of determination 0.0002) from retrospective analysis to predictive modeling. CONCLUSION: The results showed that in Jakarta Bay, particulate organic carbon variability is primarily influenced by a combination of biological production and physical transport processes modulated by monsoonal forcing. The predictions indicate that, under the current pressures, there will be negligible near-term shifts in the dynamics of particulate organic carbon along the northern coastline of Jakarta.