Search Results (161)

This study compiles and updates data to construct the phosphorus budget of the Archipelago Sea (northern Baltic Sea, Europe), with a particular focus on estimating phosphorus pools associated with fish populations. Biomass data and species-specific phosphorus content were utilized, and a bioenergetic modeling approach was applied to Baltic herring (Clupea harengus membras) and European perch (Perca fluviatilis) to estimate species-specific food consumption and nutrient excretion. Between 2001 and 2024, average total phosphorus concentrations were 28% higher than during the baseline period of 1983–1989. From 1998 to 2023, the annual average fish catch in the Archipelago Sea was 15,516.5 tons (16.3 kg/ha), with 73.1% consisting of commercially harvested herring. Other abundant catch species included, for example, pikeperch (Sander lucioperca), northern pike (Esox lucius), and European smelt (Osmerus eperlanus). On average, the annual catch contained 83.4 tons of phosphorus. Fishing may have annually removed an amount of phosphorus equivalent to approximately 0.6% of the total phosphorus pool in the water column and surface sediment, or 1.4% of the estimated total phosphorus load to the Archipelago Sea. The contribution of fish to phosphorus turnover is minor, as nutrient recycling is dominated by plankton. Planktivorous fish and their prey recycle nutrients already present in the water column and are therefore not the primary drivers of eutrophication. Full article

Inland saline wetlands in the Ebro Basin (Spain) are protected by international regulations but are also threatened by the expansion of animal farms. We studied the input–output budgets of N from animal farms in four catchments of wetlands in the central Ebro Basin designated as Nitrate Vulnerable Zones. We used the N produced in animal farms as inputs and the N extracted by the crops on which manures and slurries are applied as outputs in each catchment. The balances considered the regulations concerning the slope of land where animal excreta may be applied and the doses of application. At a detailed scale, we applied the Water Erosion Prediction Program (WEPP) to the Farnaca catchment to assess the runoff and nutrients arriving to its wetland. While the Bujaraloz-Sástago basin showed a high excess of N load, in the Gallocanta basin, N extraction by crops was significantly higher than the N produced by the animal farms. Despite this lack of surplus of N from animal excreta, the groundwaters in the Gallocanta catchment are polluted by nitrates. The emphasis on N from animal farms in plans to prevent water pollution is missing the role of mineral fertilizers as the sources of pollution in basins with small N loads from animal farms. Agricultural plots in the Farnaca catchment produce significant amounts of sediments and nutrients that eventually pollute the wetland. Modelling approaches at detailed scales are required to assess the flows of materials to individual wetlands. Full article

This study quantitatively investigates monsoon-driven bedload sediment transport mechanisms in the Qiongzhou Strait using the SCHISM model, revealing three key findings: (1) Monsoon seasonality governs net sediment flux through contrasting hydrodynamic regimes, with the winter monsoon establishing spatially coherent westward transport pathways, while the summer monsoon induces counteracting flow patterns that suppress net transport. (2) Winter conditions exhibit opposing transport vectors between tidal and monsoon forcing at both strait entrances, with monsoon dominance at the western entrance contrasting tidal predominance in the eastern sector. (3) Summer monsoon–tide hydrodynamic decoupling results in transport magnitudes ≤ 10% of tidal-driven quantities across critical cross-sections. The research elucidates sediment budget partitioning mechanisms in monsoon-dominated shelf seas, particularly revealing a spatial reversal of dominant transport drivers between eastern and western gateways that mechanistically explains observed sedimentary architecture asymmetries. By innovatively quantifying spatiotemporal coupling effects of meteorological and tidal forcing, this work advances theoretical understanding of sediment flux allocation under monsoonal systems and provides scientific support for seabed resource management and geomorphological evolution predictions. Full article

The nitrogen budget and the effects of varying densities of sea grape (Caulerpa lentillifera) on water quality and the growth performance of Asian seabass (Lates calcarifer) in a polyculture system were evaluated. Four treatments were tested, each stocked with 20 fish (average weight: ~20 g; density: 2.66 kg/m³). Treatment 1 (control) contained no sea grapes, while treatments 2, 3, and 4 included 100, 200, and 400 g of sea grapes, corresponding to 0, 667 g/m³, 1333 g/m³, and 2666 g/m³, respectively. Significant (p < 0.05) reductions in total ammonia nitrogen (TAN), total suspended solids (TSS), and turbidity were observed with increasing sea grape density; however, no significant differences (p > 0.05) were found among the three sea grape treatments. Higher sea grape densities increased nitrite (NO₂–N) and nitrate (NO₃–N) concentrations due to enhanced nitrification. Approximately 65% of the nitrogen input originated from feed, but only 47.78–48.96% was assimilated into fish biomass. Nitrogen losses included 1.17–1.46% via water exchange and final drainage, while 45.27–50.76% was likely retained in sediments, volatilized, or lost through denitrification. Sea grapes effectively absorbed total nitrogen (TN), demonstrating their potential as biofilters for improving water quality without compromising fish growth performance. The optimal density was 100 g of sea grapes per 2.66 kg/m³ of seabass biomass, offering a sustainable strategy to enhance productivity while mitigating environmental impacts. Full article

The regional sea level budget in the East China Sea (ECS) was investigated with satellite gravimetry, altimetry, steric and sediment datasets over the period from April 2002 to December 2022. The “sediment effect” due to the difference between the change in sediment mass and the displaced original seawater should be removed from the total mass change observed by satellite gravimetry data to accurately estimate the manometric sea level change associated with the variations in seawater mass. We divided the whole ECS region into sediment and nonsediment areas. After accurately estimating the manometric sea level change, specifically the change in seawater mass, the ECS regional sea level budget could be closed within a 2-sigma uncertainty. Our results revealed that the linear trends of the regional mean sea level change in the ECS can be attributed mainly to the change in the manometric sea level (3.06 mm/year), followed by the steric component (0.44 mm/year), which contributes only ~12.57% of the total ECS regional mean sea level change rate observed via satellite altimetry. The linear trend residuals of the ECS regional sea level budget ranged from −0.12 mm/year to 0.10 mm/year, all within a 2-sigma uncertainty. Full article

This study explores the potential of repurposing historical aerial photographs to produce high-accuracy digital surface models (DSMs) at regional scales. A novel methodology is introduced, incorporating road points for quality control and refinement to enhance the precision and comparability of multitemporal DSMs. The method consists of two phases. The first is the photogrammetric phase, where DSMs are generated using photogrammetric and structure from motion (SfM) techniques. The second is the refinement phase, which uses a large number (millions) of points extracted from road centrelines to evaluate altimetric residuals—defined as the differences between photogrammetric DSMs and a reference DSM. These points are filtered to ensure that they represent stable positions. The analysis shows that the initial residuals exhibit geographical trends, rather than random behaviour, that are removed after the refinement. An application example covering the whole coast of the Valencian region (Eastern Spain, 518 km of coastline) shows the obtention of a series composed of six DSMs. The method achieves levels of accuracy (0.15–0.20 m) comparable to modern LiDAR techniques, offering a cost-effective alternative for three-dimensional characterisation. The application to the foredune and coastal environment demonstrated the method’s effectiveness in quantifying sand volumetric changes through comparison with a reference DSM. The achieved accuracy is crucial for establishing precise sedimentary balances, essential for coastal management. At the same time, this method shows significant potential for its application in other dynamic landscapes, as well as urban or agricultural monitoring. Full article

Lake Trafford, a 600-ha subtropical lake in southwestern Florida, has suffered from over 50 years of cultural eutrophication, resulting in the invasion of Hydrilla verticillata and organic sediment accumulation due to herbicide treatments. This study aimed to assess the effects of dredging on nutrient dynamics. A pre-dredging nutrient budget, developed using land use models and climatic data, estimated nutrient loads of 190 kg d⁻¹ for total nitrogen (TN) and 18.6 kg d⁻¹ for total phosphorus (TP), with total maximum daily loads (TMDLs) of 70.4 kg d⁻¹ for TN and 4.15 kg d⁻¹ for TP. Post-dredging analysis, using detailed spatiotemporal data, showed higher nutrient loads of 274.3 kg d⁻¹ for TN and 24.2 kg d⁻¹ for TP. While dredging reduced legacy nutrient accumulation, it led to increased nutrient influx from groundwater, caused by the exposure of organic sediment, as evidenced by increased lake water electrical conductivity. These findings demonstrate the importance of conducting thorough pre-dredging assessments to mitigate unintended consequences, offering practical insights for managing nutrient loads and improving restoration strategies in eutrophic lakes. Full article

The shelf-edge trajectory is comprehensively controlled by tectonics, sediment supply, sea level, and climate fluctuations; its migration and evolution have a strong influence on what happens in the deep-water depositional system during the Quaternary. The shelf-edge trajectory pattern, sediment-budget partitioning into deep-water areas, and reservoir evaluations are focused topics in international geosciences. In this paper, the Qiongdongnan Basin (QDNB) in the northern South China Sea is taken as an example to study how shelf-edge trajectory migration patterns can influence the types of deep-water gravity flow which are triggered there. Through quantitatively delineating the Quaternary shelf-edge trajectory in the QDNB, four types of shelf-edge trajectory are identified, including low angle slow rising type, medium angle rising type, high angle sharp rising type, and retrogradation-slump type. A new sequence stratigraphic framework based on the migration pattern of shelf-edge trajectory is established. There are four (third-order) sequences in the Quaternary, and several systems tracts named lowstand systems tract (LST), transgressive systems tract (TST), and highstand system tract (HST) are identified. This study indicates that the type of deep-water gravity flow can be dominated by the shelf-edge trajectory migration patterns. When the shelf-edge trajectory angle (α) ranged between 0° and 4°, the continental canyons were mostly small-scaled and shallowly incised, with multiple large-scale sandy submarine fan deposits with few MTDs found in the deep-water area. When the angle (α) ranged from 4° < α < 35°, the size and incision depth of the continental slope canyons increased, relating to frequently interbedded sandy submarine fan deposits and MTDs. When angle (α) ranged from 35° < α < 90°, only a few deeply-incised canyons were present in the continental slope; in this condition, large-scaled and long-distance MTDs frequently developed, with fewer submarine fans deposits. When angle (α) ranged from 90° < α < 150°, the valley in the slope area was virtually undeveloped, sediments in the deep-sea plain area consisted mainly of large mass transport deposits, and submarine fan development was minimal. Since the Quaternary, the temperature has been decreasing, the sea level has shown a downward trend, and the East Asian winter monsoon has significantly enhanced, resulting in an overall increase in sediment supply in the study area. However, due to the numerous rivers and rich provenance systems in the west of Hainan Island, a growing continental shelf-edge slope has developed. In the eastern part of Hainan Island, due to fewer rivers, weak provenance sources, strong tectonic activity, and the subsidence center, a type of destructive shelf-edge slope has developed. The above results have certain theoretical significance for the study of shelf-edge systems and the prediction of deep-water gravity flow deposition type. Full article

Carbon burial patterns in lakes and their dynamic changes significantly impact terrestrial carbon sink fluxes and global carbon budgets. In this study, multi-indicator analysis of sediment core samples (P1, P2, and P3) from Pipahai Lake was conducted. Integrating the chronological sequences of ²¹⁰Pb and ¹³⁷Cs, we identified the historical changes and spatial characteristics of total organic carbon (TOC) and inorganic carbon (TIC) burial in Pipahai Lake since 1884. The results show that the TOC content was higher than that of the TIC. They exhibited an increasing trend with decreasing depth. Linear regression results indicated that the variation of TOC is less directly affected by precipitation (R = 0.39) and temperature (R = 0.58), while temperature may have a greater impact on TOC. From 1884 to 1995, nutrients were not the primary factor influencing changes in TOC. The synchronous variation in TIC and TOC contents reflects a higher contribution of external inputs to carbon burial in the Pipahai Lake basin. After 1996, nutrients may have begun to affect variations in TOC. The TOC primarily originates from distal aeolian transport or autochthonous sources, though human activity has played a role in its evolution. The TIC content is controlled by the TOC content and autochthonous sources. This study will contribute to the understanding of the carbon cycling dynamics and their influencing mechanisms in a high-altitude lake ecosystem. Full article

Sediment management is fundamental for managing mountain watercourses and their upslope catchment. A multidisciplinary approach—not limited to the discipline of hydraulics—is necessary for investigating the alterations in sediment transport along the watercourse by detecting those reaches dominated by erosion and deposition processes, by quantifying the sediment volume change, by assessing the functionality of the existing torrent control structures, and by delimitating the riparian vegetation patches. To pursue these goals, specific continuous monitoring is essential, despite being extremely rare in mountain catchments. The present study proposed an integrated approach to determine the hydro-morphological–sedimentological–ecological state of a mountain watercourse though field- and desk-based analyses. Such an integral approach includes a rainfall–runoff model, a morphological change analysis and the application of empirical formulations for estimating peak discharge, mobilizable sediment/large wood volume and watercourse hydraulic capacity, at reach and catchment scales. The procedure was tested on the Upper Adda River catchment (North Italy). The results identified where and with what priority maintenance and monitoring activities must be carried out, considering sediment regime, torrent control structures and vegetation. This study is an example of how it is possible to enhance all existing information through successive qualitative and quantitative approximations and to concentrate new resources (human and economic) on specific gaps, for drafting a scientifically robust and practical sediment management plan. Full article

The agricultural production of maize (Zea mays L.) increases the risk of water erosion. Perennial crops like cup plant (Silphium perfoliatum L.) offer a sustainable alternative to produce biomass for biogas plants. The assessment of soil conservation measures requires calibrated soil erosion models that spatially identify soil erosion processes. These support decision-making by farmers and policymakers. Input parameters for the physically based soil erosion model EROSION 3D for cup plant cultivation were established in a field study. Rainfall simulation experiments were conducted to determine the model input parameter’s skinfactor and surface roughness. The results showed a reduction of soil erosion and higher infiltration rates for cup plant resulting in higher skinfactors of 11.5 in June and 0.75 post-harvest (cup plant) compared to 1.2 in June and 0.21 post-harvest (maize). With the extended parameter catalogue of EROSION 3D for cup plant cultivation model simulations were conducted for a rainfall event in June (64 mm). The sediment budget would have been reduced by 92.6% through the growth of cup plant in comparison to conventionally grown maize. Perennial cup plant can, therefore, contribute to achieving the targets outlined in the European Green Deal by reducing soil erosion and enhancing soil health. Full article

Increased dust emissions from dryland areas and their effects on human health, ecosystem viability, and environmental change are a global concern in the face of the growing climate crisis. Dust plume emissions from the West African landmass, Sahara, and Sahel areas comprise a major fraction of the global aerosol budget. Dust plume intensity is closely related to regional winds (e.g., Harmattan, Sahara Air Layer), the Intertropical Convergence Zone, monsoonal seasonality, marine currents, and physiography. To study terrigenous material emitted from the continent over the last ~260 kyr (late Quaternary), we used X-ray fluorescence spectroscopy (XRF) to analyze a ~755 cm long marine sediment core from the eastern equatorial Atlantic Ocean, resulting in nearly 1400 discrete measurements. Spectral analysis results suggest that concentrations of elements (Rb, Sr, Si, Al) preserved in the sediments are correlated to different types of orbital climate forcing. Chemical weathering intensity indicated by the Rb/Sr ratio was sensitive to seasonal insolation variations controlled by precession cycles (23–18 kyr), which presumably reflects the relationship between monsoonal rainfall and sensible heating of the continent. Spectral analysis of silicate mineral grain size (Si/Al) showed significant 40 kyr cycles that were paced by obliquity. Based on these data, we infer that winter tradewind activity accelerated in response to the intertropical insolation gradient induced by high obliquity. High Rb/Sr ratios during the last glacial maximum and penultimate glacial maximum may have been due to a predominance of mechanical weathering over chemical weathering under dry/cool climates or the dissolution of Sr-bearing carbonates by corrosive glacial bottom waters. Full article

Aquaculture is increasing globally, providing protein to a growing population, but little is known regarding the nutrient budgets in aquaculture. To obtain insight into how management practices impact nutrient fluxes in freshwater aquaculture earthen ponds worldwide, we conducted a literature review. Our literature search yielded 23 papers in which nutrient budgets were reported. Our results showed that the main nutrient inputs are inlet water, feed, and fertilizers, but they varied according to location and management practices. Overall, feed and fertilizers constituted the predominant nutrient sources, accounting for up to 99% of the total inputs. The most quantified outputs were outlet water, fish, and sedimentation. Our findings indicate that only up to 20% of carbon, 45% of nitrogen, and 60% of phosphorus are assimilated by the fish. In some systems, up to 80% of carbon, 80% of nitrogen, and 60% of phosphorus accumulate in pond bottoms; in other systems, the outflow represents substantial losses of up to 16% of carbon, 76% of nitrogen, and 55% of phosphorus. More insight into nutrients’ fate in fishponds is crucial from a sustainability perspective, as feed and fertilizer use can likely be optimized, reducing operational costs and the potential impact on the surrounding environment and atmospheric greenhouse gas concentrations. Full article

The present study examines the recent evolution of a cliff coast along the Aegean Sea, considering its geotectonic context, oceanographic factors, sediment dynamics, and human impact. Initially, the formation of this coastal stretch was influenced by neotectonic faults, oriented both semi-parallel and diagonally relative to the present coastline orientation (NE–SW). Subsequently, the delivery of terrestrial sediment from ephemeral rivers and cliff erosion, along with nearshore wave-induced hydrodynamics have played a secondary role in shaping its current configuration, which includes a beach zone along the base of the cliff. This secondary phase of coastal evolution occurred over the past 4–5 thousand years, coinciding with a period of slow sea level rise (approximately 1 mm/year). Evidence such as uplifted notches and beachrock formations extending to around 5 m water depth suggests intervals of relative sea level stability, interrupted by episodic tectonic events. Anthropogenic interventions, related to both changes in coastal sediment budget and coastal engineering projects, have caused beach erosion, particularly in its central and northern sectors. Full article

Humans have influenced the sediment transport of rivers on a centurial scale. Our goal was to use the rate of lateral channel processes as a proxy to reconstruct sediment budget (SB) changes of a lowland river (Middle Tisza, Hungary) on a historical scale (1838–2017). The gross sediment budget (GSB) refers to the total area of eroded and accumulated surfaces, and the net sediment budget (NSB) indicates the sediment sink or source characteristics. At the beginning (1838–1890), the artificial cut-offs increased the slope and channel erosion, but the eroded sediment deposited in the oxbows, so the reach acted as a sediment sink (NSB: +0.1–0.8 m²/m/y). Then (1890–1929), a quasi-equilibrium state developed (NSB: −0.2 m²/m/y to +0.4 m²/m/y). Later (1929–1976), the bank protections impeded lateral erosion, so the system became a sediment sink again (NSB: +0.1–0.7 m²/m/y). Finally (1976–2017), the erosional processes accelerated due to dam construction and revetment collapses, and now the river is a sediment source (NSB: −0.03 to −0.08 m²/m/y). This study proved that (1) the actual SB could not be projected in the long term, as it was heavily modified, and (2) lateral channel changes could be used as a proxy to estimate long-term SB. Full article