Nutrient Export Research Articles

Assessing nutrient budgets and N2O emission of newly constructed rice-giant freshwater prawn co-culture on reclaimed land

In recent years, newly constructed rice-giant river prawn (Macrobrachium rosenbergii) co-culture has been widely applied on reclaimed land in southeast China. Raising M. rosenbergii in paddy fields can alter nutrient budgets and have environmental impacts. However, the exact impacts remain unclear. Here, a field experiment was conducted using M. rosenbergii and Macrobrachium nipponense in reclaimed paddy fields to assess and compare the nutrient budgets and N2O emissions of the two ecosystems, henceforth referred to as RS1 and RS2, respectively. Each ecosystem was stocked with 150,000 post-larvae per ha and then compared with a rice monoculture system (RM) to evaluate the environmental impacts of rice-shrimp co-culture. In RS1, the main inputs for N and P were fertilizer and artificial feed, accounting for 59.35% and 34.01% of the total N inputs and 53.15% and 41.43% of the total P inputs, respectively. In RS2 and RM, fertilizers dominated the nutrient budget, accounting for more than 79.28% of the total nutrient input. Nutrient exports were dominated by rice (straw+grain) and commercial shrimp in RS1, accounting for 33.44% and 18.66% of N and 55.56% and 20.02% of P, respectively. The wastewater drainage, NH3 volatilization, and N2O emissions contributed to the remainder nutrient budget. Particularly, the N2O emission fluxes in RS1 (2.21 ± 0.32 kg·ha−1·yr−1) were significantly higher than those in RS2 (1.78 ± 0.24 kg·ha−1·yr−1) and RM (1.56 ± 0.17 kg·ha−1·yr−1) over the one-year experiment. Changes in environmental variables (including NH4+-N, NO2--N, DO, pH, SP, etc.) significantly contributed to the enhanced N2O emissions following the conversion from the reclaimed paddy field to RS1. These results implied that RS1 improved the yields of shrimp and rice grains but at the cost of increasing N2O emissions. Considering the wide distribution of reclaimed paddy fields in southeast China, M. rosenbergii could serve as an ideal alternative species in rice-shrimp co-culture systems to increase nutrient utilization efficiency, although N2O emissions still need to be reduced to mitigate the negative environmental impacts.

Spatial distribution and export of nutrients and metal elements in the subterranean estuary of Daya Bay

Spatial distribution and export of nutrients and metal elements in the subterranean estuary of Daya Bay

Lake and Stream Buffer Zone Widths' Effects on Nutrient Export to Lake Rawapening, Central Java, Indonesia: A Simple Simulation Study

Lake ecosystems in Indonesia face serious environmental problems. One of those problems is eutrophication caused by excessive plant nutrients, particularly nitrogen (N) and phosphorus (P). Water quality degradation and biodiversity loss are the effects of eutrophication. The government of Indonesia (GoI) has issued a regulation on determining lake and stream buffer zones, but it has not been fully implemented in the field. Additionally, the data related to the effects of each buffer zone width is not available. This study aims to begin to fill this gap. It simulates the effect of lake and stream buffer zone widths on nutrient export to Rawapening Lake. The Nutrient Retention sub-model, which is part of InVEST (Integrated Valuation of Environmental Services and Tradeoffs) software, has been used for this research to analyse information from several data sources, including a Digital Elevation Model (DEM) and measurements of soil depth, annual rainfall, land cover/use, watershed/sub-watershed boundaries, and biophysical conditions. Several studies of eutrophication in Rawapening Lake have measured the magnitude of eutrophication but have not discussed the effects of buffer zone widths. Therefore, this study accommodates the updated data on how much effect of buffer zone widths on the reduction of nutrient export. Five scenarios of buffer zone width are considered: 30 m., 90 m., and 150 m, where the lake buffer zone widths and the stream buffer zone width are 30 m. The results indicated that the maximum nutrient export reduction of lake buffer zones was only 2.63% (for N) and 3.56% (for P). On the other hand, the 30 m stream buffer zone width reduced the nutrient export to Rawapening Lake by up to 43.05% for N and by 44.90% for P. A 30 m combined lake and stream buffer zone width slightly increases the nutrient export reduction effectiveness, i.e., 0.41% and 0.56% for N and P, respectively.

Silicon Isotopes Highlight the Role of Glaciated Fjords in Modifying Coastal Waters

AbstractGlaciers and ice sheets are experiencing rapid warming under current climatic change and there is increasing evidence that glacial meltwaters provide key dissolved and dissolvable amorphous nutrients to downstream ecosystems. However, large debate exists around the fate of these nutrients within complex and heterogenous fjord environments, where biogeochemical cycling is still often poorly understood. We combine silicon (Si) concentration data with isotopic compositions to better understand silicon cycling and export in two contrasting fjordic environments in south‐west Greenland. We show that both fjords have isotopically light dissolved silicon (DSi) within surface waters, despite an apparently rapid biological drawdown of DSi with increasing salinity. We hypothesize that such observations cannot be explained by simple water mass mixing processes, and postulate that an isotopically light source of Si, most likely glacially derived amorphous silica (ASi), is responsible for further modifying these coastal waters within the fjords and beyond. Fjord to coastal exchange is likely a relatively slow process (several months), and thus is less impacted by short‐term (<seasonal) changes of glacial meltwater input into the fjord, which has implications when considering the role of glacial meltwaters on nutrient export beyond the shelf break. We highlight the need for isotopic studies combined with dissolved and particulate nutrient concentration analysis to provide a more detailed analysis into the biogeochemical cycles within these highly dynamic fjord environments.

Field‐scale analysis of miscanthus production indicates climate change may increase the opportunity for water quality improvement in a key Iowa watershed

AbstractThe Raccoon River Basin is the primary source for drinking water in Iowa's largest city and plays a major role in the Mississippi River Basin's high nutrient exports. Future climate change may have major impacts on the biological, physiological, and agronomic processes imposing a threat to ecosystem services. Efforts to reduce nitrogen (N) loads within this basin have included local litigation and the implementation of the Iowa Nutrient Reduction Strategy, which suggest incorporating bioenergy crops (i.e., miscanthus) within the current corn–soybean landscape to reach a 41% reduction in nitrate loads. This study focuses on simulating N export for historical and future land use scenarios by using an agroecosystem model (Agro‐IBIS) and a hydrology model (THMB) at the 500‐m resolution, similar to the scale of agricultural fields. Model simulations are driven by CMIP5 climate data for historical, mid‐century, and late‐century under the RCP 4.5 and 8.5 warming projections. Using recent crop profit analyses for the state of Iowa, profitability maps were generated and nitrogen leaching thresholds were used to determine where miscanthus should replace corn–soybean area to maximize reductions in N pollution. Our results show that miscanthus inclusion on low profit and high N leaching areas can result in a 4% reduction of N loss under current climate conditions and may reduce N loss by 21%–26% under future climate conditions, implying that water quality has the potential continue to improve under future climate conditions when strategically implemented conservation practices are included in future farm management plans.

Estuarine nutrient pollution impact reduction assessment through euphotic zone avoidance/bypass considerations

The feasibility of reducing nutrient pollution impact by redirecting the effluent to depths below the euphotic zone was investigated for the deep estuarine Puget Sound region of the Salish Sea in the Pacific Northwest of America. The hypothesis tested was that the thickness of the outflow layer in deep estuaries may be greater than the euphotic zone depth, allowing a fraction of nutrients to be exported out passively through the layers immediately below. The euphotic zone depth in Puget Sound varies from 8 to 25 m while the depth of the outflow layer can reach up to ≈ 60 m. Outfall relocation strategies were tested on 99% of the anthropogenic nutrient loads currently delivered to Puget Sound. The impact was quantified using the previously established biophysical Salish Sea Model, using gross primary production and exposure to low dissolved oxygen (DO) levels as the metric (< 2 mg/L for hypoxia and < 5 mg/L for impairment). Eliminating nutrient pollution (above natural) from rivers and wastewater reduced hypoxia exposure by 8.1% and 11.2%, respectively. Relocating the outfalls to deeper waters resulted in improvements, but only in the sill-less sub-basins such as Whidbey, where hypoxia and DO impairment exposure decreased (7.9% and 6.8%, respectively). The presence of multiple sills and circulation cells in Puget Sound resulted in increased exposure and rendered nutrient bypass goals unfeasible as originally envisioned. However, an alternate nutrient export pathway was identified through bottom exchange flow out of Puget Sound via Whidbey Basin and Deception Pass. An unexpected reduction in the exchange outflow magnitude (≈ 4%) due additional (22%) freshwater discharged to the estuary bottom was also noted. The potential loss in circulation strength due to rerouting of natural surface freshwater through submerged deep-water outfalls is identified as a new unforeseen anthropogenic impact.

Cretaceous to Palaeogene boundary events and palaeoenvironmental responses across pelagic sequences of the Žilina core section, Slovakia: Rock magnetic, biotic, and geochemical characterization

The Žilina-Hradisko borehole in Slovakia intersects a succession from the Cretaceous Hradisko formation to the Paleocene Hričovské Podhradie formation. In this paper, we mainly focus on the Cretaceous–Palaeogene (K–Pg) boundary interval, which is marked by an abrupt change in planktonic biota and magnetic properties. Micropalaeontological findings suggest a rapid change from a stable, oxygen-rich, oligotrophic environment during the Maastrichtian to an unstable, cooler environment with reduced oxygenation and evidence of biotic stress in the lowermost Danian strata. An abrupt change in the magnetite concentration in the same interval indicates increased detrital input and probably biogenic (soft) magnetite production. Evidence recorded in borehole with enhanced Hg input into the Maastrichtian Ocean suggests that the Deccan eruptions mostly occurred prior to the K–Pg boundary, whereas no volcanic Hg input was detected at the K–Pg boundary itself. Double peaks in multiple magnetic properties mark the Danian hyperthermal Dan-C2 event, which was characterised by a series of environmental changes, including enhanced terrigenous input, oxygen deficit, increased nutrient supply, high benthic productivity, and Parasubbotina acme. Prior to the Latest Danian event, foraminiferal assemblages were significantly affected by dissolution and oxygen depletion, followed by warming, water column stratification, and diversification of calcareous plankton groups. An increase in detrital input and nutrient export drove the productivity of deep-dwelling subbotinids and globanomalinids and were correlated with the mid-Paleocene biotic event (MPBE). The seafloor biota associated with the MPBE implies oxygen deficiency and the prevalence of benthic infauna. The Selandian–Thanetian strata markedly differ from planktonic foraminifera of older formations, with their rich content of large, diversified, and heavily calcified morozovellid and igorinid foraminifera, revealing the existence of water column stratification with surface-water productivity and meso- to oligotrophic conditions. The microfauna of ornate morozovellids and benthic biota from the lowermost formation implies the onset of environmental stress and CaCO3 dissolution during the Paleocene-Eocene Thermal Maximum (PETM).

Environmental potential for crop production and tenure regime influence fertilizer application and soil nutrient mining in soybean and maize crops

CONTEXTDifferences in land tenure regimes are one challenge to implementing soil conservation practices in agricultural systems. It is frequently assumed that tenants are less likely to adopt soil conservation strategies than owners, given a shorter-term engagement with the field. Also, the field's environmental potential (i.e., potential for agricultural production) may influence farmers' investment decisions, since high-potential fields increase the chances of achieving a return on the investment. OBJECTIVEUnderstand the effect of land tenure regimes and environmental potential on fertilization rates and balance of nitrogen, phosphorus, and sulfur in soybean and maize crops in Argentina. METHODSWe applied mixed-effects models on a database of 52,588 fields of soybean and maize farms, covering a total area of 3.8 M ha in Argentina during the period of 2017–2022. RESULTS AND CONCLUSIONSOverall, the balance of nitrogen, phosphorus, and sulfur was (mean ± SE) −29.11 ± 0.15, −2.58 ± 0.38, and 8.26 ± 0.044 kg ha−1 yr−1, respectively. Despite 8.04 and 0.63 kg ha−1 yr−1 more nitrogen and phosphorus were applied in high-potential compared to low-potential maize fields, nutrient outputs were still higher. Therefore, net nutrient exports of the most productive fields increased by 9.99 and 2.06 kg ha−1 yr−1 for nitrogen and phosphorus, respectively. In soybean fields, environmental potential had no effect on nutrient application, but the net export of nitrogen and phosphorus was 9.85 and 2.14 kg ha−1 yr−1 higher in high-potential fields compared to low-potential fields. Tenure regime had a weak effect, mainly on phosphorus. On average, owners applied 0.37 kg ha−1 yr−1 more and exported 0.28 kg ha−1 yr−1 less phosphorus than tenants in both crops. Sulfur application and balance were weakly affected by the studied variables, and the positive balance suggests overfertilization under the assumptions of this paper. We conclude that the Argentine farming system depletes some of the main nutrients, regardless of the field's environmental potential or the land tenure system. The effect of the tenure regime is overwhelmed by the impact of environmental potential on farmers' fertilization management, with high-potential fields degrading due to soil mining at a faster pace than low-potential fields, putting future yields at risk. SIGNIFICANCEBy exploring a farming system based on nutrient depletion, our results contribute to the general understanding of tenure regime consequences on soil degradation. Argentinean farmers should consider increasing N and P application and contemplate environmental heterogeneity to avoid nutrient mining and degradation of one of the most productive areas of the world.

Temporal and Spatial Variations in Subterranean Estuary Geochemical Gradients and Nutrient Cycling Rates: Impacts on Groundwater Nutrient Export to Estuaries

AbstractSubterranean estuaries (STEs) form at the land‐sea boundary where groundwater and seawater mix. These biogeochemically reactive zones influence groundwater‐borne nutrient concentrations and speciation prior to export via submarine groundwater discharge (SGD). We examined a STE located along the York River Estuary (YRE) to determine if SGD delivers dissolved inorganic nitrogen (DIN) and phosphorus (DIP) to the overlying water. We assessed variations in STE geochemical profiles with depth across locations, times, and tidal stages, estimated N removal along the STE flow path, measured hydraulic gradients to estimate SGD, and calculated potential nutrient fluxes. Salinity, dissolved oxygen (DO), DIN, and DIP varied significantly with depth and season (p < 0.05), but not location or tidal stage. Ammonium dominated the DIN pool deep in the STE. Moving toward the sediment surface, ammonium concentrations decreased as nitrate and DO concentrations increased, suggesting nitrification. Potential sediment N removal rates mediated by denitrification were <8 mmoles N m−2 d−1. The total groundwater discharge rate was 38 ± 11 L m−2 d−1; discharge followed tidal and seasonal patterns. Net SGD nutrient fluxes were 0.065–3.2 and 0.019–0.093 mmoles m−2 d−1 for DIN and DIP, respectively. However, microbial N removal in the STE may attenuate 0.58% to >100% of groundwater DIN. SGD fluxes were on the same order of magnitude as diffusive benthic fluxes but accounted for <10% of the nutrients delivered by fluvial advection in the YRE. Our results indicate the importance of STE biogeochemical transformations to SGD flux estimations and their role in coastal eutrophication and nutrient dynamics.

A slurry approach to identify nutrient critical source areas from subtropical catchment erosion

Targeting catchment nutrient critical source areas (CSAs) (areas contributing most of the nutrients in a catchment) is an efficient way to prioritize remediation sites for reducing nutrient runoff to waterways. We tested if the soil slurry approach – with particle sizes and sediment concentrations representative of those in streams during high rainfall events – can be used to identify potential CSAs within individual land use types, examine fire impacts, and identify the contribution of leaf litter in topsoil to nutrient export in subtropical catchments. We first confirmed the slurry approach met the prerequisite to identify CSAs with relatively higher nutrient contribution (not absolute load estimation) by comparing the slurry sampling with stream nutrient monitoring data. We validated that: 1) differences in slurry total nitrogen to phosphorus mass ratios from different land uses were consistent with stream monitoring data; and 2) our estimated nutrient export contribution from agricultural land, via the slurry approach, was comparable to that derived from monitoring data. Additionally, we found nutrient concentrations in slurries differed across soil types and management practice within individual land uses, correlating with nutrient concentrations in fine particles. These results indicate the slurry approach can be used to identify potential small-scale CSAs. Slurry results from burnt soils were also comparable to other studies showing increased levels of dissolved nutrient loss and higher nitrogen than phosphorus loss, than non-burnt soils. The slurry method also showed the contribution of leaf litter to slurry nutrient concentrations from topsoil was greater for dissolved nutrients than particulate nutrients, indicating different forms of nutrients need to be considered for impacts of vegetation. Our study reveals that the slurry method can be used to identify potential small-scale CSAs within the same land use from erosion and can account for impacts of vegetation and bushfires, providing timely information to guide catchment restoration actions.

Assessing nutrient and sediment load reduction potential of vegetation by utilizing the nutrient tracking tool at the field and watershed scale in a Great Lakes priority watershed

PurposeNutrient and sediment pollution of surface waters remains a critical challenge for improving water quality. This study takes a user-friendly field-scale tool and assesses its ability to model at both the field and watershed scale within the Fox River Watershed (FRW), Wisconsin, USA, along with assessing how targeted vegetation implementation could attenuate nutrient and sediment exports.MethodsTo assess potential load reductions, the nutrient tracking tool (NTT) was used with a scoring system to identify areas where vegetation mitigation could be implemented within three selected FRW sub-watersheds. A corn soybean rotation, an implementation of a 10-m-vegetated buffer, a full forest conversion, and tiling were modeled and assessed. The corn–soybean results were aggregated and compared to watershed level gauge data in two sub-watersheds. Edge-of-field data was compared to modeled results using multiple parameterization schemes.ResultsThe agricultural areas that scored higher and were untiled showed greater potential nutrient and sediment export reduction (up to 80 to 95%) when vegetation mitigation was implemented in the model. Field-scale results aggregated to the watershed scale showed disparities between modeled and measured phosphorus exports but modeled sediment exports fell within observed gauge data ranges. Field-specific parameter adjustments resulted in more accurate modeled results compared to measured edge-of-field export data but needed further refinement.ConclusionTargeted mitigation using a vegetation-based scoring system with the NTT model was shown to be a helpful tool for predicting nutrient and sediment reductions. Using a field-scale model aggregated to the watershed scale presents tradeoffs regarding processes found beyond the edge of field.

Export of organic carbon, nutrients and metals by the mid-sized Pechora River to the Arctic Ocean

In contrast to good knowledge of export fluxes of carbon and metals from mainland to the Arctic Ocean by large Arctic Rivers, information on mid-sized rivers is limited, which prevents determining current status and foreseeing future changes in riverine export induced by climate change. Here we focused on one of the ‘middle eight’ Arctic rivers. The Pechora River (Swatershed = 322,000 km2) is the second largest European Arctic river draining through boreal forest and peatlands with partial (∼ 40%) permafrost coverage. Over 4 consecutive years (2015–2019), we measured weekly to monthly concentrations of carbon, major nutrients, and 40 major and trace elements in filtered (< 0.45 μm) river water at the terminal gauging stations for the Pechora River. The dependences between dissolved element concentration and river discharge over the full period of observation revealed 3 groups of major and trace solutes according to their seasonal behavior. Group 1 was comprised of Dissolved Inorganic Carbon (DIC), major anions (Cl, SO4), alkalis (Li, Na, K, Rb), alkaline-earth metals (Mg, Ca, Sr, Ba), elements present in the form of labile anions and neutral molecules (B, Si, Ge, Mo, Sb) and U. It demonstrated minimal concentrations during spring flooding and autumn high flow events, and maximal concentrations during winter base flow. Concentrations of these element negatively correlated with discharge. These elements primarily reflected the dominant sedimentary lithology of the Pechora catchment and were controlled by influx of underground waters hosted in carbonate rocks. Group 2 included DOC and low-mobility trivalent and tetravalent hydrolysates (Be, Al, Ga, Y, REEs, Ti, Zr, Hf, Th) and some trace metals (V, Cr, Cs, Nb). The transport of these elements to the river from the catchment likely occurred via surface and shallow subsurface waters due to leaching from organic-rich litter layer, and their concentrations positively correlated with discharge. Finally, group 3 involved major- (P, N, K) and micro-nutrients (Fe, Mn, Cu, Zn, Mo) and demonstrated features of both the 1st and 2nd groups as these elements originated from surface (organic-rich) and underground (sedimentary rock-hosted) sources and were removed by autochthonous biotic processes in the water column. As a result, the concentration of these nutrients exhibited a winter maximum and a summer minimum.Similar to other Arctic and subarctic rivers, the spring flood, which lasted from May to June, accounted for >50% of the annual export of DOC and generally insoluble trace metals. However, the winter baseflow provided sizable proportions of mobile elements such as DIC, major anions, cations, alkaline-earth elements, trace oxyanions and uranium. The size distribution of riverine solutes demonstrated 20–50% of DOC in the colloidal (3 kDa – 0.45 μm) form, dominance of low molecular forms (< 3 kDa) of soluble elements (alkali, alkaline earths, anions and neutral molecules) and essentially colloidal status of divalent metals (Cu, Zn, Cd, Pb, Ni), trivalent and tetravalent hydrolysates and U (from 30 to 93%). Seasonal variations in colloidal fractions of riverine solutes were consistent with the main mechanisms of element mobilization from the watershed to the Pechora River, as reflected in the 3 groups of elements according to their concentration – discharge relationship. Based on the present study and results of other mid-sized Arctic rivers (Severnaya Dvina, Taz), we demonstrate that mean discharges and solute concentrations in August can be used to adequately (± 20%) approximate mean annual values, hence allowing annual flux assessment via single month sampling campaign. A comparison of contemporary yields of Ca, Mg, Cl, SO4, DIC and DOC against historical data for the Pechora River basin demonstrated reasonable agreement within the inter-annual variations that is consistent with long-term data series on other Arctic rivers.

Community reorganization stabilizes freshwater ecosystems in intensively managed agricultural fields

Abstract Sustainable intensification may depend on associating precision farming with the harnessing of ecological principles in crop fields, and integrating farms and non‐farmed land in productive landscapes. Small wetlands could play an important role in both pursuits for having high per‐unit‐area rates of element cycling and species richness while deeply penetrating crop fields. However, their potential for ecosystem service provisioning is unlikely to be met if land management intensification promotes ecosystem destabilization in biomass production. We tested the consequences of land use intensification on various dimensions of freshwater ecosystem stability by means of a large‐scale field experiment converting extensive pastures to intensive pastures and sugarcane plantations in Southeastern Brazil. Nested within experimental plots were 4000 L mesocosms simulating ponds and puddles commonly found in productive landscapes. Mesocosms were monitored for basic physico‐chemical parameters, nutrients, pesticides, phytoplankton standing crop, and the spontaneously colonizing biodiversity. Despite severe environmental change, the stability of sugarcane communities was no different from that of extensive and intensive pastures. This occurred because the local extinction of a sensitive top dragonfly predator following the application of vinasse and insecticide was compensated by colonization of a suite of more tolerant invertebrate mesopredators such as beetles and bugs. Community stability tended to increase with biomass asynchrony and species richness, evidencing a portfolio effect of biodiversity. Unfortunately, the species richness necessary to stabilize biomass production is unlikely to be available in many sugarcane fields and several other row crops. Synthesis and applications. Ponds and puddles could be effective centers of irradiation of ecosystem service provisioning in agricultural fields in terms of pest control; nutrient accumulation, cycling and export back to fields; and habitat and stepping stones for freshwater biodiversity. However, the impoverished biodiversity that results from a combination of harsh local conditions and spatial isolation renders pond communities inherently unstable. Given the unlikely, immediate reduction in agrochemical use in much of the intensively managed crop area, a combination of large, protected source wetlands at the margin of fields and small constructed or naturally forming ponds and puddles in plantations could contribute to sustainable intensification.

Nutrients in tropical and temperate rivers and floodplains – comparison of the Rivers Songkhram (Thailand) and Narew (Poland)

Ecological processes in floodplains may function differently across climate regions. We compared the river discharge, water chemistry, and nutrient budget and balance of floodplain vegetation in a temperate climate (River Narew, Poland) with those in a tropical climate (River Songkhram, Thailand). Both rivers show a discharge regime with a flood pulse, following snowmelt (Narew) or monsoon rainfall (Songkhram), with peak discharges roughly 25 times higher in the River Songkhram. Electrical Conductivity (EC) values of both rivers are generally comparable, while nutrient concentrations are somewhat higher in the temperate River Narew (with total phosphorus (TP) approximately 1.5 and total inorganic nitrogen (TIN) approximately 2.2 times higher than in Songkhram). A comparison of the nutrient budget of floodplain vegetation suggests that soil is the most important source of nutrients for most vegetation types, i.e., Narew sedge (N), Narew forest floor (N and P), Songkhram bamboo (N and P), and Songkhram grass (P). Additionally, floodwater is the main input source of P for the Narew sedge and a secondary input source for Songkhram grass. Vegetation close to the river tends to have higher productivity, emphasizing the nutrient-filtering function of floodplain vegetation. For both rivers, nutrient input into the floodplains by floodwater is higher than nutrient export from the floodplains, indicating that both floodplains have a nutrient sink function. These findings demonstrate that the floodwater pulse is a source of nutrient input for floodplain vegetation in both temperate and tropical climates, with the soil playing a vital role in the nutrient budgets and balance.

Modelling the impacts of changing land use and climate on sediment and nutrient retention in Lake Tana Basin, Upper Blue Nile River Basin, Ethiopia

Natural ecosystems provide many different services such as carbon sequestration, regulation of climate change, biodiversity, and aesthetic value. Ecosystem functions are significantly impacted by both natural and man-made processes, such as sediment and nutrient deposition. The Lake Tana basin faces significant problems with soil depletion, sedimentation, and degradation. Thus, this study is designed to assess the effects of climate and land use change on the export of sediment and nutrients as well as their retention in the basin. This study used different data sources such as satellite data for land use and land cover and watershed preparation, climate data from Climate Hazards Group InfraRed Precipitation with Station data (CHIRPS) and Climate Model Intercomparison Project phase five (CMIP5), soil data from Ministry of Water, Irrigation and Electricity (MoWIE), and field data for model calibration. Five different Global Climate Models (GCMs) were employed to produce climate projections using the Long Ashton Research Station Weather Generator (LARS-WG) for the basin. The cellular automata (CA) and Markov chain has then been employed for future projections of changes in land use. Finally, the Integrated Valuation of Ecosystem Services and Tradeoff (InVEST) sediment delivery ratio (SDR) and nutrient delivery ratio (NDR) models have been applied to assess the changes in sediment and nutrient export between the baseline and future time periods. The findings indicated that between 1990 and 2019, there was a change in land use that led to an increase in sediment exports of 60.5% and a decrease in sediment retention of 12.8%. Projecting into the future, the amount of exported and retained sediment increases under the RCP4.5 and RCP8.5 scenarios in the 2040s by 8.4% and 17.8%, respectively due to the combined effects of climate and land use change. Equally, nitrogen and phosphorus exports rose under land use change scenarios but are projected to decrease under climate and integrated climate and land use change scenarios. Out of the 12 sub-watersheds that were designated, five were found to have a high mean annual rate of sediment and nutrient export and were then ranked in terms of priority level for conservation planning. Hence, this research shows that the integration of spatial data with the InVEST model can be used to aid land use planning and decision-making to combat nutrient and sediment exports and prioritize watersheds.

Effects of forest residue mulching on organic matter and nutrient exports after wildfire in North-Central Portugal

The quick implementation of emergency stabilization measures is vital for minimizing post-fire soil erosion and the associated fertility loss. Mulching has proven to be highly effective in minimizing post-fire soil erosion, however few studies have investigated its impacts on organic matter (OM) and nutrient mobilization from burned forest areas. This study evaluates the effectiveness of forest residue mulching at reducing OM, N and P losses within the sediments after a moderate-severity wildfire over a period of 5 years (Ermida, North-central Portugal). Untreated and mulched plots of ca. 100 m2 were bounded with geotextile fabric and sediments were collected from silt fences after a total of 29 periods.During the first five years after the fire, the accumulated OM, N and P exportations in the untreated plots were, respectively, 199, 5.2 and 0.38 g m−2; and mulch significantly reduced these figures in, respectively, 91 %, 94 % and 95 % (p < 0.05). The overall OM content in the sediments of the untreated plots (45 %) was not different from the OM content of the mulched plots (34 %, p = 0.16). However, the N (8.9 g kg−1) and Pav contents (0.62 g kg−1) in the untreated plots were significantly higher than the N (5.6 g kg−1; p < 0.05) and Pav contents (0.36 g kg−1; p < 0.05) in the mulched plots. This effect was especially noticeable in the first year after fire. OM and TN contents in the sediments were highly variable throughout the study period, whereas Pav contents declined sharply in the first post-fire rainfall events, maintaining low values afterwards. The main factors driving nutrient exports were ash and litter cover, whereas no significant relationship was observed for OM exports. The present work has shown that forest residues application can be a sustainable strategy for the conservation of soil carbon and nutrients in fire-affected areas.

Glacial Water: A Dynamic Microbial Medium.

Microbial communities and nutrient dynamics in glaciers and ice sheets continuously change as the hydrological conditions within and on the ice change. Glaciers and ice sheets can be considered bioreactors as microbiomes transform nutrients that enter these icy systems and alter the meltwater chemistry. Global warming is increasing meltwater discharge, affecting nutrient and cell export, and altering proglacial systems. In this review, we integrate the current understanding of glacial hydrology, microbial activity, and nutrient and carbon dynamics to highlight their interdependence and variability on daily and seasonal time scales, as well as their impact on proglacial environments.

Storage and export of nutrient and oxyhydroxide elements across glaciated soils and watersheds in western Massachusetts, USA

Quantifying the geologic, pedogenic, and human processes governing elemental release and transport in glaciated terrains is complex but has several important ramifications for nutrient storage, formation of secondary minerals, and protection of surface and groundwater resources.Here, soils and river waters were studied in three subwatersheds of the Deerfield river from October 2018 to January 2020 to determine if nutrient (Ca, K, P) and oxyhydroxide elements (Al, Fe, Mn) were retained within the soil or exported from the watershed via river water at comparable rates in: Supra-glacial till Forested soils, Fluvial Agriculture soils, and Sub-glacial Till Hydric soils. This study found higher soil storage, soil water transport, and watershed export of nutrients in the Fluvial Agriculture subwatershed compared with the Supra-glacial Till subwatershed. The Supra-glacial Till subwatershed had the greatest overall river water nutrient export as it was the largest subwatershed but when considered with area-normalized basis, the Fluvial Agricultural soils exported 3x to 6x higher nutrients. When considering the oxyhydroxide elements, Al was not significantly different among geologic deposits and land covers. Iron concentrations in soils and soil water were not significantly different between hydric and forest soils, despite higher acidity, higher dissolved organic carbon, and lower electropotential in the former. Agricultural soils were enriched in Mn likely due to continuous agriculture since 1677 CE, which is unreported in agricultural fields of New England with potential impacts on soil C dynamics or microbial communities.

Impacts on water quality in the peatland dominated catchment due to foreseen changes in Nordic Bioeconomy Pathways

The Nordic Bioeconomy Pathways (NBPs), conceptualized subsets of Shared Socioeconomic Pathways varying from environmentally friendly to open-market competition scenarios, can lead to plausible stressors in future for using bioresources. This study analysed the impacts of NBPs on hydrology and water quality based on two different land system management attributes: management strategy and a combination of reduced stand management and biomass removal at a catchment-scale projection. To understand the potential impacts of NBPs, the Simojoki catchment in northern Finland was chosen, as the catchment mainly covered peatland forestry. The analysis integrated a stakeholder-driven questionnaire, the Finnish Forest dynamics model, and Soil and Water Assessment Tool to build NBP scenarios, including Greenhouse gas emission pathways, for multiple management attributes to simulate flows, nutrients, and suspended solids (SS). For the catchment management strategy, an annual decrease in nutrients was observed for sustainability and business-as-usual scenarios. Reduced stand management and biomass removal also led to decreased export of nutrients and SS for the same scenarios, whereas, in other NBPs, the export of nutrients and SS increased with decreased evapotranspiration. Although the study was investigated at a local scale, based on the current political and socioeconomic situation, the approach used in this study can be outscaled to assess the use of forest and other bioresources in similar catchments.

High‐Resolution Coccolithophore Morphological Changes in Response to Orbital Forcings During the Early Oligocene

AbstractThe global climate of the early Oligocene was characterized by initiated Antarctic glaciation and meridional overturning circulation, which then led to profound eutrophication in the upper ocean. Generating a high‐resolution coccolith record helps to understand the responses of marine phytoplankton to the newly established environment. Using highly resolved (∼6 kyr time‐resolution) marine sediment samples from Deep Sea Drilling Project Site 522 in the South Atlantic Ocean, we conducted a comprehensive morphological study on coccoliths from the genera Reticulofenestra, Dictyococcites, and Coccolithus, which dominated the study interval between ∼33.1 and 32.8 Ma. Our results showed that the size variations of the three measured genera were significantly correlated (p &lt; 0.01) with each other, indicating homogeneous responses to the environmental changes. Moreover, spectrum analysis on integrated morphologic data of all measured coccoliths showed distinct obliquity (∼40‐kyr) and precession (∼23‐kyr and ∼18‐kyr) cycles. We suggest that these variations were mainly driven by temperate, short‐term ecological fluctuations, which periodically altered the nutrient conditions in the common living habitats of the studied coccolithophores. We proposed two tentative explanations focusing on the obliquity signal. First, the cyclic variation could result from obliquity‐modulated changes in ice volume and variations in ocean circulation intensity, which influenced nutrient export from deep waters to the upper ocean. Alternatively, the changes in coccolith size may indicate the strength of seasonality that influenced upper ocean mixing on the west coast of South Africa.