Nutrient Concentrations Research Articles

Continental-scale nutrient and contaminant delivery by Pacific salmon.

The movement of large amounts of nutrients by migrating animals has ecological benefits for recipient food webs1,2 that may be offset by co-transported contaminants3,4. Salmon spawning migrations are archetypal of this process, carrying marine-derived materials to inland ecosystems where they stimulate local productivity but also enhance contaminant exposure5-7. Pacific salmon abundance and biomass are higher now than in the last century, reflecting substantial shifts in community structure8 that probably altered nutrient versus contaminant delivery. Here we combined nutrient and contaminant concentrations with 40 years of annual Pacific salmon returns to quantify how changes in community structure influenced marine to freshwater inputs to western North America. Salmon transported tonnes of nutrients and kilograms of contaminants to freshwaters annually. Higher salmon returns (1976-2015) increased salmon-derived nutrient and contaminant inputs by 30% and 20%, respectively. These increases were dominated by pink salmon, which are short-lived, feed lower in marine food webs than other salmon species, and had the highest nutrient-to-contaminant ratios. As a result, the delivery of nutrients increased at a greater rate than the delivery of contaminants, and salmon inputs became more ecologically beneficial over time. Even still, contaminant loadings may represent exposure concerns for some salmon predators. The Pacific salmon example demonstrates how long-term environmental changes interact with nutrient and contaminant movement across large spatial scales and provides a model for exploring similar patterns with other migratory species9.

Review of the facilitators and barriers to adoption of biofortified foods and food products.

Biofortification - the process of increasing the concentrations of essential nutrients in staple crops - is a means of addressing the burden of micronutrient deficiencies at a population level via existing food systems, such as smallholder farms. To realise its potential for global impact, we need to understand the factors that are associated with decisions to adopt biofortified crops and food products. We searched the literature to identify adoption determinants, i.e. barriers to (factors negatively associated) or facilitators of (factors positively associated) adoption, of biofortified crops and food products. We found 41 studies reporting facilitator(s) and/or barrier(s) of adoption. We categorised the factors using the Consolidated Framework of Implementation Research 2.0, resulting in a set of factors that enable or constrain adoption of biofortified foods across twenty-four constructs and five domains of this meta-theoretical determinant framework from implementation science. Facilitators of orange sweet potato adoption included knowledge about importance, relative advantage, efficient production and management practices; barriers included lacking timely access to quality vines and market remoteness (28 studies total). Facilitators of vitamin A cassava adoption included awareness of its benefits and access to information; barriers included poor road networks and scarcity of improved technology including inadequate processing/storage facilities (8). Facilitators of high-iron bean adoption included farmers' networking and high farming experience; barriers included low knowledge of bean biofortification (8). Barriers to vitamin A maize adoption included low awareness and concerns regarding yield, texture and aflatoxin contamination (1). These barriers and facilitators may be a starting point for researchers to move towards testing implementation strategies and/or for policymakers to consider before planning scale-up and continuous optimisation of ongoing projects promoting adoption of biofortified crops and food products.

Ecological Implications of Seasonal Variations in Physicochemical Parameters and Phytoplankton Community in an Effluent‐Receiving Wetland in the Gulf of Guinea, Cameroon

ABSTRACTPhysicochemical parameters, chlorophyll a (Chl a) concentration, and phytoplankton community structure were assessed in the Wouri estuarine mangrove sector of the Douala Bassa Industrial Zone of Cameroon over two seasons. Three sets of water samples were collected from 10 sites for these analyses. Some physicochemical parameters were measured in situ using multiparameter equipment (HANNA 8289). The data were subjected to analyses of significant difference by an independent sample t‐test. Correlation and principal component analysis conducted between variables Temperature, salinity, total dissolved solids (TDS), resistivity, and turbidity showed a strong seasonal variation among sites. Mean Chl a concentration (3.7–48.29 µg/L for dry and 0.1–20.1 µg/L for rainy season) revealed that most sites were eutrophic, with the Euglenophycean index less than 1 in all the sites. Phytoplankton species richness exhibited seasonal and spatial variation, with a total of 74 taxa and 51 taxa for the dry and rainy seasons, respectively. The division Bacillariophyta was the most abundant, with 19 families and 24 species during the dry season and 17 families and 16 species during the rainy season. Other phytoplankton divisions present included Chlorophyta > Cyanophyta > Charophyta > > Myzozoa > Euglenophyta in the dry season; the less diverse divisions in the rainy season were Rhodophyta > Cryptophyta > Xanthophyta > Euglenophyta. High concentrations of nutrients and the presence of eutrophic species such as Microcystis aeruginosa suggest pollution and a need to monitor activities carried out along the water course with respect to the quantity and quality of industrial effluents discharged into the stream. The observed eutrophication explains the noxious odor across the city of Douala, especially during the dry season. The human health implications could be severe, with communities dependent on this contaminated stream for fish and other necessities a scenario that repeats itself in communities dependent on urban wetlands in industrial zones globally.

Interannual and seasonal variability of the air–sea CO2 exchange at Utö in the coastal region of the Baltic Sea

Abstract. Oceans alleviate the accumulation of atmospheric CO2 by absorbing approximately a quarter of all anthropogenic emissions. In the deep oceans, carbon uptake is dominated by aquatic phase chemistry, whereas in biologically active coastal seas the marine ecosystem and biogeochemistry play an important role in the carbon uptake. Coastal seas are hotspots of organic and inorganic matter transport between the land and the oceans, and thus they are important for the marine carbon cycling. In this study, we investigate the net air–sea CO2 exchange at the Utö Atmospheric and Marine Research Station, located at the southern edge of the Archipelago Sea within the Baltic Sea, using the data collected during 2017–2021. The air–sea fluxes of CO2 were measured using the eddy covariance technique, supported by the flux parameterization based on the pCO2 and wind speed measurements. During the spring–summer months (April–August), the sea was gaining carbon dioxide from the atmosphere, with the highest monthly sink fluxes typically occurring in May, being −0.26 µmol m−2 s−1 on average. The sea was releasing the CO2 to the atmosphere in September–March, and the highest source fluxes were typically observed in September, being 0.42 µmol m−2 s−1 on average. On an annual basis, the study region was found to be a net source of atmospheric CO2, and on average, the annual net exchange was 27.1 gC m−1 yr−1, which is comparable to the exchange observed in the Gulf of Bothnia, the Baltic Sea. The annual net air–sea CO2 exchanges varied between 18.2 (2018) and 39.1 gC m−1 yr−1 (2017). During the coldest year, 2017, the spring–summer sink fluxes remained low compared to the other years, as a result of relatively high seawater pCO2 in summer, which never fell below 220 µatm during that year. The spring–summer phytoplankton blooms of 2017 were weak, possibly due to the cloudy summer and deeply mixed surface layer, which restrained the photosynthetic fixation of dissolved inorganic carbon in the surface waters. The algal blooms in spring–summer 2018 and the consequent pCO2 drawdown were strong, fueled by high pre-spring nutrient concentrations. The systematic positive annual CO2 balances suggest that our coastal study site is affected by carbon flows originating from elsewhere, possibly as organic carbon, which is remineralized and released to the atmosphere as CO2. This coastal source of CO2 fueled by the organic matter originating probably from land ecosystems stresses the importance of understanding the carbon cycling in the land–sea continuum.

Spatial and Temporal Variability in the Bottom Sediment Characteristics of a Shallow Lake under Backwater Separation and Application of Effective Microorganisms

Lake Konin is a small and shallow lake under the influence of highly eutrophic riverine waters. Feeding the lake as a backwater during high water level periods, the River Obra had exerted a decisive impact on lake water quality, and thus a new dike with a closing device was created. Protective measures were followed by the application of Effective Microorganisms (EM), aiming at a reduction in nutrient concentrations and CyanoHABs. Positive changes in the ecosystem were initiated (increased phytoplankton diversity), but cyanobacteria blooms were still present due to high nutrient content. Some changes were observed in the lake sediments (phosphorus (P) and its fractions, P in pore waters, organic matter and experimental assessment of internal P loading) studied before and during treatment. A slight increase in P content in sediments was noted, as a result of an increase in the Res-P fraction. Simultaneously, a decrease in the most mobile fractions was observed. Summer internal P load was reduced from 5.4 kgP d−1 before the treatment to less than 1 kgP d−1 in the first year, but increased again in the second year to 4.5 kgP d−1. Similarly to lake water quality, positive changes were induced in the lake sediments; nevertheless, they still acted as an important source of nutrients for primary producers. Additional restoration methods shall be considered, as combined treatments used simultaneously are reported to be the most effective for water quality improvement.

Towards the understanding of genetic and morphological variations of a highly abundant seaweed-associated marine invertebrate

Unraveling the patterns of genetic structure and demographic history of marine species, as well as the factors that shape their genetic variations, is fundamental for informing conservation strategies for species and their environments. In this work, we investigate the current population structure and historical demographic patterns of the conspicuous seaweed-associated amphipod Hyale niger at a fine spatial scale in the subtropical SW Atlantic coast, in Brazil, by using both genome-wide and mitochondrial DNA markers. We also investigate how geographic distance, current oceanographic conditions, and variations in a key morphological trait contribute to the genetic variability of the amphipod. We observed an evident population genetic structure, even at a fine spatial scale, although genetic differentiation was lower than our expectations for a benthic direct brooder. Demographic history inferences were consistent across populations and showed two major demographic expansions on interglacial periods during the late Pleiostocene, before and after the last glacial maximum. We also demonstrated that isolation-by-environment (IBE) was the main driver of genetic differentiation, although we could not separate it from the effects of isolation-by-distance (IBD). Among environmental factors, nutrient concentrations in seawater were most relevant for explaining genetic structure. In addition, our data suggest that morphological variation in gnathopod 2 structure of males were not genetic-related and were probably plastic as a response to variations in macroalgae frond size. Our study reinforces the importance of using multiple molecular markers and analytical approaches to unveil patterns and processes generating genetic variation in natural populations.

Sedimentary record of primary productivity changes in a crater lake in Northeast China since the Last Glacial Maximum

High-resolution primary productivity records are valuable for identifying lacustrine ecosystem degradation in the context of long-term climatic variability. In this paper, we analyse primary productivity changes in a seasonally ice-covered crater lake (Lake Tuofengling) in northeast China since the Last Glacial Maximum using biogenic silica content and the carbon preference index of short-chain n-alkanes as proxies. Results show that primary productivity was lower during the cold and dry glacial period, whereas it was higher during the warm and humid Holocene. During the last deglaciation, primary productivity experienced a ∼ 1.5-kyr lagged response to Bølling-Allerød warming, and multiple oscillations during the Younger Dryas. Additionally, the peak productivity of the entire profile also occurred during this period. These fluctuations and the highest primary productivity are suggested to be the result of the combined influences of increased summer temperatures and regional permafrost melting. The current state of primary productivity in Lake Tuofengling is moderate but has been increasing since the abrupt increase in diatom productivity after ∼3 ka B.P. This stage is associated with increased dust deposition and longer ice-free periods under winter-warming conditions. We suggest that longer seasonal stratification under the current warmer winters and increased nutrient concentrations caused by decreased lake level will increase the risk of lake ecosystem degradation in the future.

Impact of water depth and flow velocity on organic matter removal and nitrogen cycling in floating constructed wetlands

The configuration of water depth (WD) and flow velocity (FV) in floating constructed wetlands (FCWs) reflects the complex interactions between hydraulic conditions and wastewater treatment performance. Properly configuring hydraulic conditions can optimize performance. This study explored the removal and degradation of organic matter and nitrogen (N) in FCWs with three different WDs (50 cm (SD), 70 cm (MD), and 95 cm (DD)) under four FV conditions (0, 0.3, 1.0, and 1.5 m/d). It also analyzed the regulatory effects of hydraulic conditions on microbial community structure to provide new insights for configuring hydraulic conditions in FCWs. The results indicate that variations in WD and FV do not significantly affect COD removal (p > 0.05), with removal efficiency (RE) consistently reaching 90 % across all conditions. However, hydraulic conditions do influence the degradation rate (k) of COD, with increased FV enhancing the k in MD and DD. In contrast, WD significantly impacts the removal of NH4+−N (p < 0.05), with RE in SD exceeding 80 % across all four FVs. The primary reason is that increased WD reduced the abundance of nitrifying bacteria (Nitrosomonas and Nitrospira) and functional genes (hao and pmoABC-amoABC). Meanwhile, increased WD and FV significantly enriched the denitrifying bacteria genera (such as Massilia, Bacillus, Ensifer, and Rhodobacter) and certain functional genes (nap and nir), favoring the denitrification process and enhancing the dissimilatory nitrate reduction to ammonium (DNRA) process. Furthermore, microbial community diversity, richness, and the number of operational taxonomic units (OTUs) were highest in SD, but decreased with increased WD. This is mainly related to changes in oxygen (O2) transmission and nutrient concentration. These findings help us understand the mechanisms by which hydraulic regulation affects the removal of organic matter and N in FCWs. They also propose potential solutions from a hydraulics perspective to enhance N removal.

Assessment and prediction of Water Quality Index (WQI) by seasonal key water parameters in a coastal city: application of machine learning models.

The Water Quality Index (WQI) provides comprehensive assessments in river systems; however, its calculation involves numerous water quality parameters, costly in sample collection and laboratory analysis. The study aimed to determine key water parameters and the most reliable models, considering seasonal variations in the water environment, to maximize the precision of WQI prediction by a minimal set of water parameters. Ten statistical or machine learning models were developed to predict the WQI over four seasons using water quality dataset collected in a coastal city adjacent to the Yellow Sea in China, based on which the key water parameters were identified and the variations were assessed by the Seasonal-Trend decomposition procedure based on Loess (STL). Results indicated that model performance generally improved with adding more input variables except Self-Organizing Map (SOM). Tree-based ensemble methods like Extreme Gradient Boosting (XGB) and Random Forest (RF) demonstrated the highest accuracy, particularly in winter. Nutrients (Ammonia Nitrogen (AN) and Total Phosphorus (TP)), Dissolved Oxygen (DO), and turbidity were determined as key water parameters, based on which, the prediction accuracy for Medium and Low grades was perfect while it was over 80% for the Good grade in spring and winter and dropped to around 70% in summer and autumn. Nutrient concentrations were higher at inland stations; however, it worsened at coastal stations, especially in summer. The study underscores the importance of reliable WQI prediction models in water quality assessment, especially when data is limited, which are crucial for managing water resources effectively.

Influence of earthworms on the mobility and bioavailability of metals, metalloids and radionuclides in historically contaminated soil

While soil characteristics such as pH, cation exchange capacity and organic matter are known to influence the mobility of pollutants in soil and the transfer to vegetation, far less attention has been paid to the possible non-trophic influence of organisms on pollutant transfer to other species. When pollutants are present in a bound unavailable form in the mineral or organic fraction, they can be made available through bio-weathering and decomposition of organic material. Within this study, the impact of earthworms on the mobility of metal(loid)s and radionuclides in soil and their transfer to vegetation was evaluated and the pathways through which earthworms work were studied. Soil from a Belgian field, historically contaminated with metal(loid)s and radionuclides, was used and microcosm systems were applied to mimic the natural interactions between soil, earthworms (Lumbricus terrestris) and vegetation (Lolium perenne). Metal and radionuclide concentrations were determined in soil, pore water and grass. In addition, soil pH, (chromophoric) dissolved organic matter, the ionic composition of pore water and the soil microbial activity were analysed. In general, earthworm presence significantly increased the concentration of most pollutants in soil pore water. This could be a direct consequence of decreased soil pH and increased humification. The latter also lead to higher nutrient concentrations in pore water that were depleted in the root zone due to high accumulation by plants. Indications were found for earthworm-induced effects on the soil microbial activity. The results show that earthworm activity can increase leaching of metal(loid)s and radionuclides and enhance dispersion into the environment and transfer to other biota and the food chain. Biologically induced release or remobilization of pollutants in the soil should therefore be considered in the context of risk assessment and site management strategies.

Differential response of multiple stream ecosystem processes to basin- and reach-scale drivers

Stream ecosystems are inherently dependent on their surroundings and, thus, highly vulnerable to anthropogenic impacts, which alter both their structure and functioning. Anchored in biologically-mediated processes, the response of stream ecosystem functioning to environmental conditions exhibits intricate patterns, reflecting both natural dynamics and human-induced changes. Our study aimed at determining the natural and anthropogenic drivers influencing multiple stream ecosystems processes (nutrient uptake, biomass accrual, decomposition, and ecosystem metabolism) at a regional scale. By examining 38 natural and anthropogenic variables across 63 stream reaches in Gipuzkoa (northern Iberian Peninsula), we used structural equation modeling to unravel the cascading effect of basin- and reach-scale drivers onto ecosystem process. The results reveal significant variability in ecosystem processes, with contrasting spatial patterns, suggesting that studied processes respond differently to environmental factors. Urban land-use emerged as a primary basin-scale driver, whereas reach-scale variables reflected both natural and anthropogenic influence. Nutrient uptake rates were primarily driven by nutrient concentrations in stream water, but models for biomass accrual, decomposition, and ecosystem metabolism exhibited more complex cause-effect relationships. Our findings highlight the impact of urban areas on multiple ecosystem processes and services, disproportionate when considering their small land cover. The present study emphasizes the convenience of measuring multiple ecosystem functions simultaneously to get a comprehensive diagnosis of the functional status of rivers.

Comparative Photosynthetic Capacity, Respiration Rates, and Nutrient Content of Micropropagated and Wild-Sourced Sphagnum

The rapid, effective restoration of degraded peatlands is urgently needed to reduce their current high levels of carbon loss. The re-introduction of Sphagnum moss, along with re-wetting, is key to returning carbon sequestration and retention capabilities to northern degraded bogs. Micropropagated Sphagnum has already been applied in large quantities, and more is planned, for restoration projects in Britain and parts of Europe. A comparison with wild-sourced Sphagnum material is therefore pertinent to demonstrate its safety and suitability for wide-scale application. Six Sphagnum species of both micropropagated and wild-sourced origin were assessed for photosynthetic capacity, nutrient content, form parity, chlorocyst size, and chloroplast numbers. Micropropagated Sphagnum had significantly higher light-saturated photosynthesis (Pmax) rates, little color expression, an open growth habit, greater chloroplast numbers, and more numerous, smaller shoot apices than wild-sourced Sphagnum. Higher Pmax rates were associated with a lower bulk density and higher tissue nutrient concentrations. Potentially, greater chloroplast numbers in micropropagated Sphagnum facilitate higher photosynthesis rates, driving rapid growth in early-stage plants, particularly in optimum moisture conditions. Micropropagated Sphagnum can be used confidently, propagated in large quantities, and will likely establish well on application to sites where re-wetting has already occurred, therefore making it highly beneficial for the restoration of degraded bogs.

Conversion of Oil Palm Empty Fruit Bunch Fiber Waste into Green Liquid Organic Fertilizer

Solid wastes generated from the oil palm industry contain valuable nutrients like nitrogen, phosphorus, and potassium that can significantly enhance plant growth and potentially elevate fertilizer production. This study aims to identify the optimal formulation of liquid organic fertilizer (LOF) derived from oil palm empty fruit bunch (OPEFB) fiber waste. Three formulations of LOF were prepared, comprising OPEFB waste, molasses, noni fruit, and cattle urine, designated as Formulation A, B, and C. These formulations underwent a 14-day anaerobic incubation period. The formulated OPEFB LOF was then analyzed for nutrient content, electrical conductivity, and total dissolved solids. This study also examines the soil properties and plant growth outcomes following the application of the formulated OPEFB LOF. The results indicated that Formulation A exhibited the highest nutrient concentrations, specifically 485 ppm nitrogen, 95 ppm phosphorus, and 1007 ppm potassium. In comparison to the other two OPEFB LOF formulations, Formulation A showed the lowest values for total dissolved solids (502 ppm) and electrical conductivity (8.14 dS/m). The findings demonstrated that Formulation A displayed the most favorable growth characteristics in terms of leaf count, plant height, leaf length, and leaf width. This is attributed to the nitrogen-boosting properties of cattle urine, along with the complementary effects of molasses and noni fruit as soil improver and bio-activator. This study confirms the viability of utilizing green organic fertilizer derived from OPEFB substrate in agriculture, replacing conventional inorganic fertilizers.

C:N stoichiometry and the fate of organic carbon in ecosystems of the northwest Pacific Ocean

Phytoplankton elemental composition regulates the efficiency of energy and material transfer in the interface between phytoplankton and their consumers. The ratio of particulate organic carbon to particulate organic nitrogen (POC:PON) shows considerable regional deviations from the canonical Redfield ratio in the global surface ocean. However, in certain oceanic regions such as the northwest Pacific Ocean (NWPO) POC:PON distribution and its ecological significance remain uncertain. We investigated surface ocean POC:PON distributions at 66 stations in the NWPO, and quantified the correlations between POC:PON and multiple biotic and abiotic factors including sea surface temperature (SST), nutrient concentrations and multiple lipid biomarkers (fatty acids and sterols), by combining correlation analyses and generalized additive models. POC:PON (range: 3.53–14.18 M ratios; median: 6.89) was overall higher in the (sub)tropical biome than that in the high-latitude biome. In the entire study region, SST, nutrient concentration and lipid-derived phytoplankton community structure explained 41 %, 33 % and 26 % of the variance in POC:PON, respectively, while the respective importance of each factor differed between the (sub)tropical and high-latitude biomes. Furthermore, we calculated the percentage of primary production consumed by herbivores (PPC; 54–156 %), showing a higher mean value (117 %) in the high-latitude biome and a lower one (92 %) in the (sub)tropical biome. The spatial distribution pattern of PPC can be attributed to multiple factors, with PPC correlating negatively with SST and positively with lipid-based indicators of phytoplankton food quality and POC concentrations. The increase in SST may be associated with a reduced nitrogen content, resulting in lower PPC in the (sub)tropical biome. This study highlights the significance of SST and elemental and biochemical composition of phytoplankton in regulating the transfer of organic carbon to herbivores in the NWPO.

Exploring Bark‐Water Interaction Effects on Stemflow Nutrient Concentrations in Urban Trees

ABSTRACTThis study investigates the influence of bark properties on nutrient fluxes in urban environments, focusing on the relationship between bark wettability, chemical composition, and the concentrations of nutrients in stemflow and adjacent soil across eight urban tree species. Through a comprehensive analysis involving chemical assays and ecohydrological measurements, we explored how variations in bark characteristics affect water interaction and subsequent chemical dynamics within urban landscapes. Contrary to the initial hypothesis that bark properties would significantly influence nutrient flux, results revealed a complex scenario where environmental and anthropogenic factors in urban settings seemingly overshadow the direct impact of bark characteristics on nutrient dynamics. Our findings indicate that while bark properties such as wettability and chemical composition do vary among tree species, these variations do not directly correlate with significant differences in stemflow or soil nutrient concentrations. This suggests a homogenising effect of urban environments on ecohydrological processes, highlighting the need for a broader understanding of urban forest ecology that incorporates both biological traits and urban‐specific environmental influences. This research contributes to the field of urban ecohydrology by underscoring the complexity of nutrient fluxes in urban forests and suggesting that effective urban tree management requires an integrated approach that considers the interplay between tree physiological traits and urban environmental conditions. Our study calls for further research to unravel the intricate dynamics of urban ecosystems, aiming to enhance the sustainability and ecological benefits of urban forests.

Dynamic water‐quality responses to wildfire in Colorado

AbstractIn 2020, Colorado experienced the most severe wildfire season in recorded history, with wildfires burning 625 357 acres across the state. Two of the largest fires burned parts of Rocky Mountain National Park (RMNP), and a study was initiated to address concerns about potential effects on drinking water quality from mobilization of ash and sediment. The study took advantage of a wealth of pre‐fire data from adjacent burned and unburned basins in western RMNP. Pre‐ and post‐fire data collection included discrete sample collection and high‐frequency water‐quality measurements using in‐stream sensors. Kruskal–Wallis tests on discrete data indicated that specific conductance, base cations, sulphate, chloride, nitrate, and total dissolved nitrogen concentrations increased post‐fire, whereas silica and dissolved organic carbon (DOC) did not (p ≤ 0.05). In‐stream sensors captured large spikes in concentrations of nutrients, turbidity, and DOC in the burned basin that were missed by discrete sampling. Sensor data indicated nitrate and turbidity increased by up to one and two orders of magnitude, respectively, from pre‐event concentrations during storms, and DOC increased up to 3.5×. Empirical regression equations were developed using pre‐fire data and applied to the post‐fire period to estimate expected stream chemistry in the absence of fire (a ‘no‐fire’ scenario). Overlays of actual post‐fire chemistry showed the timing and magnitude of differences between observed and ‘estimated’ chemistry. For most solutes, observed post‐fire concentrations were notably greater than expected under the ‘no‐fire’ scenario, and differences were greatest during storm events. Comparison of data from the burned and unburned basins indicated DOC concentrations were affected by climate as well as fire. Results from this study demonstrate the importance of both pre‐fire data and high‐frequency data for characterizing dynamic hydrochemical responses in wildfire‐affected areas.

Ocean warming enhances the competitive advantage of Ulva prolifera over a golden tide alga, Sargassum horneri under eutrophication

Recent years have seen the Ulva green tide and Sargassum golden tide become commonplace in the coastal waters of China. However, little is known on how the combination of ocean warming and eutrophication would affect the interaction of green and golden tides. In this study, we cultured the green tide alga Ulva prolifera and the golden tide alga Sargassum horneri under different temperatures (5, 10, 15, 20, 25, and 30°C) and two nutrient concentrations (Low nutrient, LN: 5 μM-nitrate and 0.5 μM-phosphate; High nutrient, HN: 500 μM-N and 50 μM-P) in both monoculture and coculture systems to investigate the physiological responses and their competitive relationships. In monocultures, the growth of U. prolifera and S. horneri, along with pigment concentrations and photosynthesis, increased with rising temperature, reaching a plateau at 15 - 25°C. However, when the temperature increased to 30°C, the growth of U. prolifera and S. horneri decreased abruptly, with S. horneri even suffering death. In coculture, the growth of both U. prolifera and S. horneri was inhibited compared to the monoculture, with the greatest decline observed in S. horneri at 25°C under two nutrient conditions. Our results show that U. prolifera would outcompete S. horneri under high temperature in coculture, suggesting that ocean warming would enhance the competitive advantage of green tide over golden tide under eutrophication in the future.

Long‐Term Variability of Phytoplankton Primary Production in the Ulleung Basin, East Sea/Japan Sea Using Ocean Color Remote Sensing

AbstractIn recent years, significant changes in environmental conditions and marine ecosystems have been observed in the East Sea/Japan Sea. This study investigates the long‐term environmental dynamics and phytoplankton responses in the Ulleung Basin, situated in the southwestern East Sea/Japan Sea, utilizing satellite and in situ data from 2002 to 2021. Over this period, there was a noticeable increase in sea surface temperature (SST) (r = 0.5739, p &lt; 0.01), accompanied by decreasing mixed layer depth (MLD) and chlorophyll‐a (Chl‐a) concentration (r = −0.6193 and −0.6721, respectively; p &lt; 0.01). Nutrient concentrations within the upper 50 m significantly declined for nitrate and phosphate. A reduction in the N:P ratio indicated a shift from phosphorus‐limited to nitrogen‐limited environment. Moreover, primary production (PP) demonstrated a decreasing trend (r = −0.5840, p &lt; 0.01), coinciding with an increase in small phytoplankton contribution (r = 0.6399, p &lt; 0.01). Rising SST potentially altered the water column's vertical structure, hindering nutrient entrainment from the deep ocean. Consequently, this nutrient limitation may increase small phytoplankton contribution, resulting in a decline in total PP. Under the IPCC's SSP5‐8.5 scenario, small phytoplankton contribution in the Ulleung Basin is projected to rise by over 10%, resulting in a 29% average PP decrease by 2100. This suggests a diminishing energy supply to the food web in a warming ocean, impacting higher trophic levels and major fishery resources. These findings emphasize the critical need for understanding and monitoring these environmental shifts for effective fisheries management and marine ecosystem conservation.

Subsurface influences on watershed nutrient concentrations and loading in a clay dominated agricultural system

Water quality issues in the Great Lakes Basin persist despite management and monitoring efforts. With changing land use and climatic conditions, the need for improved understanding of nutrient loss from agricultural field to surface water is imperative to reduce consequences on human and aquatic life, such as perpetual algal blooms and contaminated drinking water. There remains a gap in holistic rural water management studies that investigate the understanding of the water cycle in rural settings and the interconnections between different components of the water cycle, including artificial drainage. In the current study, a year-round paired investigation of subsurface and nutrient dynamics was conducted in a small, intensively managed agricultural watershed within southwestern Ontario, Canada. Nutrients (Nitrate and Phosphorus) and stable isotopes of water (δ2H and δ18O) were sampled at varying scales (i.e., field and watershed), from multiple hydrologic components (e.g., groundwater, surface water, tile flow, and soil water), from 2020 to 2022. Results indicate that nutrient concentrations in surface water were elevated during the growing season, while nutrient loading was greater during the non-growing season in surface water. Monthly nitrate loads were found to be significantly (p < 0.01) related to groundwater elevation, soil moisture and tile flow, whereas total phosphorus loading was found to be significantly (p < 0.01) related to soil moisture and tile flow. δ2H and δ18O signatures revealed that during the growing season nutrient movement was predominantly through interflow pathways (including tile drainage) comprised of event-water. In the non-growing season, there was an increased subsurface influence on nutrient transport. This study highlights the importance of including subsurface characterization in nutrient management studies. A comprehensive understanding of varying seasonal hydrologic mechanisms that control nutrient movement within an agricultural watershed is essential to sustain growing rural communities.

Host genotype and age shape the microbial community in the rhizosphere soils of Camellia forests.

Microbiota living in the rhizosphere influences plant growth and fitness, from the opposite perspective; whether host genotypes control its root microbiota is of great interest to forest breeders and microbiologists. To improve low-yield plantations and promote sustainable management of Camellia oleifera, high-throughput sequencing was used to study the chemical properties and microbiome in rhizosphere soil of Camellia forests under three genotypes (common C. oleifera, local C. gauchowensis, and C. chekiangoleosa) and three growth stages (sapling stage at 4-year-old, primary fruit stage at 7-year-old, and full fruiting stage at 11-year-old). The results showed that the rhizosphere soil organic matter (OM), nutrient concentrations, diversity, and community composition of the microbiome were significantly varied among different Camellia genotypes. The relative abundance of symbiotic and pathotrophic fungi in the rhizosphere soil of C. chekiangoleosa was significantly higher than that of C. gauchowensis. Concentrations of OM, available phosphorus (AP), and bacterial alpha diversity increased with tree age. Fungi of Saitozyma, Mortierella, and Glomeromycota and bacteria of Burkholderia-Caballeronia-Paraburkholderia and Vicinamibacterales had potential for fertilizer development for Camellia plantation. Camellia genotypes and growth stages were significantly correlated with the rhizosphere soil pH, OM, and available potassium (AK). Soil pH and OM were key factors that affected the microbiome in the Camellia rhizosphere soils. In conclusion, tree genotypes and growth stages shaped microbial communities in Camellia rhizosphere soils, and some plant growth-promoting rhizobacteria were identified as preliminary candidates for improving Camellia plantation growth.