Elevated Nutrient Research Articles

Testing for terrestrial and freshwater microalgae productivity under elevated CO2 conditions and nutrient limitation

BackgroundMicroalgae CO2 fixation results in the production of biomass rich in high-valuable products, such as fatty acids and carotenoids. Enhanced productivity of valuable compounds can be achieved through the microalgae’s ability to capture CO2 efficiently from sources of high CO2 contents, but it depends on the species. Culture collections of microalgae offer a wide variety of defined strains. However, an inadequate understanding of which groups of microalgae and from which habitats they originate offer high productivity under increased CO2 concentrations hampers exploiting microalgae as a sustainable source in the bioeconomy.ResultsA large variety of 81 defined algal strains, including new green algal isolates from various terrestrial environments, were studied for their growth under atmospheres with CO2 levels of 5–25% in air. They were from a pool of 200 strains that had been pre-selected for phylogenetic diversity and high productivity under ambient CO2. Green algae from terrestrial environments exhibited enhanced growth up to 25% CO2. In contrast, in unicellular red algae and stramenopile algae, which originated through the endosymbiotic uptake of a red algal cell, growth at CO2 concentrations above 5% was suppressed. While terrestrial stramenopile algae generally tolerated such CO2 concentrations, their counterparts from marine phytoplankton did not. The tests of four new strains in liquid culture revealed enhanced biomass and chlorophyll production under elevated CO2 levels. The 15% CO2 aeration increased their total carotenoid and fatty acid contents, which were further stimulated when combined with the starvation of macronutrients, i.e., less with phosphate and more with nitrogen-depleted culture media.ConclusionGreen algae originating from terrestrial environments, Chlorophyceae and Trebouxiophyceae, exhibit enhanced productivity of carotenoids and fatty acids under elevated CO2 concentrations. This ability supports the economic and sustainable production of valuable compounds from these microalgae using inexpensive sources of high CO2 concentrations, such as industrial exhaust fumes.

Integrated effects of co-evolutions among climate, land use and vegetation growing dynamics to changes of runoff quantity and quality

Climates, Land use/land cover (LULC) and vegetation growing dynamics have been regarded as the main factors affecting terrestrial hydrological process. However, the mechanisms underlying their integrated effects on terrestrial runoff and nutrient dynamics are not understood well. Here, we constructed a framework to disentangle and quantify the independent and coupled contributions of climate, LULC and vegetation leaf area index (LAI) changes to watershed runoff and nutrient yields changes. Long series of changing meteorological, LULC and LAI data between 1990 and 2020 were integrated into a factor-controlled simulation protocol in a distributed hydrological model, to quantify their comprehensive contributions (individual contribution of single factor change and coupling contribution of multiple factor synchronous changes) to runoff and nutrient changes. The results showed that changes of runoff and nutrient yields are more induced by climate change, rather than LULC and LAI transformations. Increase in annual precipitation significantly elevated runoff and nutrient yields. TP yield was more sensitive to climate change than runoff and TN yields. LULC transformation and climate change have synergistic effects on runoff and nutrient yields. Shift of vegetation areas to construction lands will amplify the effect of climate change on runoff and nutrient yields. Single LAI change has weak effect on runoff and nutrient yields, but it can significantly alter the hydrological effects derived from climate change and the synergistic effects between climate change and LULC transformation. This study considered the coupling and potential synergistic effects among climate change, LULC conversion and LAI variation, which elucidated the comprehensive effects of changing environment on runoff and nutrients evolutions in a more systematic and integrated perspective.

Wildfires in the western United States are mobilizing PM2.5-associated nutrients and may be contributing to downwind cyanobacteria blooms.

Wildfire activity is increasing in the continental U.S. and can be linked to climate change effects, including rising temperatures and more frequent drought conditions. Wildfire emissions and large fire frequency have increased in the western U.S., impacting human health and ecosystems. We linked 15 years (2006-2020) of particulate matter (PM2.5) chemical speciation data with smoke plume analysis to identify PM2.5-associated nutrients elevated in air samples on smoke-impacted days. Most macro- and micro-nutrients analyzed (phosphorus, calcium, potassium, sodium, silicon, aluminum, iron, manganese, and magnesium) were significantly elevated on smoke days across all years analyzed. The largest percent increase was observed for phosphorus. With the exception of ammonium, all other nutrients (nitrate, copper, and zinc), although not statistically significant, had higher median values across all years on smoke vs. non-smoke days. Not surprisingly, there was high variation between smoke impacted days, with some nutrients episodically elevated >10 000% during select fire events. Beyond nutrients, we also explored instances where algal blooms occurred in multiple lakes downwind from high-nutrient fires. In these cases, remotely sensed cyanobacteria indices in downwind lakes increased two to seven days following the occurrence of wildfire smoke above the lake. This suggests that elevated nutrients in wildfire smoke may contribute to downwind algal blooms. Since cyanobacteria blooms can be associated with the production of cyanotoxins and wildfire activity is increasing due to climate change, this finding has implications for drinking water reservoirs in the western United States, and for lake ecology, particularly alpine lakes with otherwise limited nutrient inputs.

AWWA Water Science Author Spotlight

<i>AWWA Water Science</i> Author Spotlight

Preparation of nitrogen-doped carbon dots and their enhancement on lettuce yield and quality.

Nanotechnology is an effective way to stimulate the yield potential of crops. Various nano-fertilizers and nano-carriers are gradually being developed to bring about a technological revolution in the agricultural industry. As a biocompatible water-soluble nanomaterial, carbon dots (CDs) have attracted the attention of researchers for applications in agriculture. In this study, we prepared nitrogen-doped CDs (N-CDs) as a type of water-soluble carbon nanofertilizer by a one-pot hydrothermal method, and investigated its effects on lettuce biomass and quality. 100 and 200 mg L-1 of N-CDs substantially promoted lettuce biomass accumulation (41.70%), elevated lettuce nutrient content, as well as promoted the accumulation of major nutrients. Moreover, 100 mg L-1 N-CDs increased the chlorophyll a content by 12.68%, significantly increased the electron transport rate (ETR) by 38.61%, significantly increased the light energy conversion efficiency (Y(II)) by 31.24% and increased the Rubisco activity by 60.61%, which are important reasons for its increase in actual photosynthesis rate. N-CDs also have a positive effect on plant nitrogen metabolism by promoting the activity of glutamine synthetase. The significant benefits of N-CDs on lettuce make them have great potential for agricultural yield increase and quality improvement.

Intake of energy, protein, amino acidsand minerals by dogs under energy restriction for body weight loss when fed with commercial weight loss diets.

This retrospective study evaluated energy and nutrient intake of dogs in a weight loss programme. Ninety-four obese dogs were divided into three groups: G5-15: from 5% to 15% body weight (BW) loss (n = 55); G155-25: from 15.1% to 25% BW loss (n = 29); and G > 25: more than 25.1% BW loss (n = 10). Five brands of kibble diets designed for weight loss were analysed for crude protein, amino acids, fat, dietary fibre, and minerals. The food metabolizable energy (ME) was estimated (NRC, 2006). Data were compared inside each group using the paired t test and between groups with analysis of variance and Tukey tests (p < 0.05). The BW loss (weeks in regimen) was: G5-15, 9.8% ± 2.7% (13.5 ± 5.7 weeks); G15-25, 17.5% ± 2.7% (22.6 ± 11.9 weeks); G > 25, 30.0% ± 2.1% (50.4 ± 17.4% weeks; p < 0.01). The mean weekly BW loss rate was similar between groups (0.8% ± 0.3%; p > 0.05) but was higher during the first (0.96.6% ± 0.5%) than in the second (0.64% ± 0.4%) half of the regimen (p < 0.01). At beginning ME intake for BW loss did not differ (251.6 ± 32.2 kJ/kg0.75 /day), but it was lower for G > 25 in the second half of the regimen (230.3 ± 44.3; p = 0.02). Considering the observed ME intake of each dog, depending on the commercial product, intake below recommended for maintenance was verified for crude protein in 1%-20% of the dogs, methionine in 4%-38% of dogs, methionine plus cystine in 4%-22% of dogs, tryptophan in 7%-93% of dogs, potassium in 2%-85% of dogs and magnesium in 1% up to 95% of dogs. Although the diets presented elevated nutrient concentrations per MJ, due to the reduced energy allowance, the estimated intake of several nutrients was lower than the recommendations, highlighting the importance of changing the formulation perspective, which must prioritize the actual nutrient intake per kg of BW during the energy deficit.

Investigating relationships between climate controls and nutrient flux in surface waters, sediments, and subsurface pathways in an agricultural clay catchment of the Great Lakes Basin

Water quality within agricultural catchments is governed by management practices and climate conditions that control the transport, storage, and exchange of nutrients between components of the hydrologic cycle. This study aims to improve knowledge of nitrogen (N) and phosphorus (P) transport in low permeability agricultural watersheds by considering spatial and temporal trends of surface water nutrient concentrations in relation to hydroclimatic drivers, sediment quality, shallow hyporheic exchange, groundwater quality, and tile drain discharge over a 14-month field study in a clay hydrosystem of the Lake Huron basin, one of the five Great Lakes. Results found that events of varying magnitude and intensity enhanced nutrient release from overland flow and subsurface pathways. Tile drain discharge was found to be a consistent and elevated source of P and N to surface waters when flowing, mobilizing both diffuse nutrients from fertilizer application and legacy stores in the vadose zone. Surface water quality was temporally variable at the seasonal and event scale. Targeted sampling following fertilization periods, snowmelt, and moderate precipitation events revealed catchment wide elevated nutrient concentrations, emphasizing the need for targeted sampling regimes. Controls other than discharge magnitude and overland flow were found to contribute to peak nutrient concentrations, including internal nitrate loading, soil-snowmelt interaction, catchment wetness, and freeze thaw cycles. Sediments were found to store P in calcium minerals and have a high P storage capacity. Instream mechanisms such as sediment P fixation and hyporheic exchange may play a role in mediating surface water quality, but currently have no discernable benefit to year-round surface water nutrient concentrations. Best management practices need to focus on reducing sources of agricultural nutrients (e.g., field phosphorus concentrations and tile drain discharge loading) at the watershed scale to reduce nutrient concentrations and export in flashy clay catchments.

Cyanobacterial Blooms Are Not a Result of Positive Selection by Freshwater Eutrophication.

Long-standing cyanobacterial harmful algal blooms (CyanoHABs) are known to result from synergistic interaction between elevated nutrients and superior ecophysiology of cyanobacteria. However, it remains to be determined whether CyanoHABs are a result of positive selection by eutrophic waters. To address this, we conducted molecular evolutionary analyses on the genomes of 9 bloom-forming cyanobacteria, combined with pangenomics and metatranscriptomics. The results showed no positive selection by water eutrophication. Instead, all homologous genes in the species are under strong purifying selection based on the ratio of divergence at nonsynonymous and synonymous sites (dN/dS) and phylogeny. The dN/dS < 0.85 (median = 0.3) for all homologous genes are similar between the genes in the pathways driving CyanoHABs and housekeeping functions. Phylogenetic support for non-positive selection comes from the mixed clustering of strains: strains of the same species from diverse geographic origins form the same clusters, while strains from the same origins form different clusters. Further support lies in the codon adaptation index (CAI) and single nucleotide polymorphism (SNP). The CAI ranged from 0.42 to 0.9 (mean = 0.75), which indicates high-level codon usage bias; the pathways for CyanoHABs and housekeeping functions showed a similar CAI. Interestingly, CAI was negatively correlated with gene expression in 3 metatranscriptomes. The numbers of SNPs were concentrated around 5 to 50. As the SNP number increases, the gene expression level decreases. These negative correlations agree with the population-level dN/dS and phylogeny in supporting purifying selection in bloom-forming cyanobacteria. In summary, superior ecophysiology appears to be acquired prior to water eutrophication. IMPORTANCE CyanoHABs are global environmental hazards, and their mechanisms of action are being intensively investigated. On an ecological scale, CyanoHABs are consequences of synergistic interactions between biological functions and elevated nutrients in eutrophic waters. On an evolutionary scale, one important question is how bloom-forming cyanobacteria acquire these superior biological functions. There are several possibilities, including adaptive evolution and horizontal gene transfer. Here, we explored the possibility of positive selection. We reasoned that there are two possible periods for cyanobacteria to acquire these functions: before the onset of water eutrophication or during water eutrophication. Either way, there should be molecular signatures in protein sequences for positive selection. Interestingly, we found no positive selection by water eutrophication, but strong purifying selection instead on nearly all the genes, suggesting these superior functions aiding CyanoHABs are acquired prior to water eutrophication.

Corrosion of the interior steel surfaces of offshore monopiles

ABSTRACT The present paper reports on four-year field investigations aimed at ascertaining internal corrosion rates for offshore wind-power generation monopiles, despite these being designed to obviate internal corrosion through oxygen exclusion. Results for mild steel strips within the enclosed, quiescent, uPVC simulated seawater environments are presented as a function of relative to mean tide level, period of exposure and localised pollution of seawater. Detailed pit depth measurements are also reported for various exposure periods, with the magnitude of such corrosion displaying a bi-modal behaviour as a function of exposure time, consistent with much other data. No evidence was found of the classical corrosion profile for vertical steel structures (e.g. piles) or of accelerated low water corrosion usually associated with microbiologically influenced corrosion caused by elevated seawater nutrient concentrations. It is proposed that the observed corrosion behaviours primarily are the result of the shielded quiescent environment. The practical implications are briefly discussed.

Spatio-temporal distribution, photoreactivity and environmental control of dissolved organic matter in the sea-surface microlayer of the eastern marginal seas of China

Abstract. As the boundary interface between the atmosphere and ocean, the sea-surface microlayer (SML) plays a significant role in the biogeochemical cycles of dissolved organic matter (DOM) and macronutrients in marine environments. In our study, the optical properties of DOM were compared between the sub-surface water (SSW) and the SML during spring, summer and winter in the East China Sea (ECS) and the Yellow Sea (YS). In addition, photoexposure experiments were designed to compare photochemical degradation processes of DOM between the SML and the SSW. Chromophoric DOM (CDOM), fluorescent DOM, dissolved organic carbon, chlorophyll a (Chl a), picoplankton, nutrients and bacteria were frequently enriched in the SML. The enrichment factors (EFs) of tryptophan-like component 4 were significantly higher than other fluorescence components; the longer wavelength absorption values of CDOM showed higher EFs in the SML, and a more significant relationship between CDOM and Chl a in the SML, indicating that autochthonous DOM was more strongly enriched in the SML than the terrestrial DOM. Higher EFs were generally observed in the SML in the off-shore regions than in the coastal regions, and CDOM in the SML was photobleached more after relatively strong irradiation, as also indicated by the lower percentages of humic-like DOM and lower specific UV absorbance values (SUVA254) in the SML than the SSW. Compared to the SSW, the elevated nutrients may stimulate phytoplankton growth, biological activity and then production of abundant fresh autochthonous DOM in the SML. Our results revealed a new enrichment model for exploring the air–sea interface environment, which can explain the more autochthonous properties of DOM in the SML than the SSW.

Effects of deforestation on dissolved organic carbon and nitrate in catchment stream water revealed by wavelet analysis

Deforestation can lead to an increase in the availability of nutrients in the soil and, in turn, have an impact on the quality of water in receiving water bodies. This study assesses the impact of deforestation by evaluating the in-stream concentrations of dissolved organic carbon (DOC) and nitrate, their internal relationship, and those with stream discharge in the Wüstebach headwater catchment (Germany). This catchment has monitored stream water and associated environmental parameters for over a decade as part of the TERENO initiative. Additionally, there is a paired undisturbed forested catchment that serves as a reference stream. Our approach included a more advanced correlation analysis, namely wavelet analysis, that assists in determining changes in the correlation and lag time between the variables of interest over different time scales. This study found that after deforestation, there was an immediate increase in in-stream DOC concentrations, followed by an increase in nitrate ~1 year later. Overall, the mean DOC concentration increased, and mean nitrate concentration decreased across the catchment post-deforestation. Elevated stream water nutrient levels peaked around 2 to 3 years after the clear-cutting, and returned to pre-deforestation levels after ~5 years. The deforestation had no influence on the anti-correlation between DOC and nitrate. However, the correlation between both compounds and discharge was likely altered due to the increased soil nutrients availability as a result of deforestation. Wavelet coherence analysis revealed the “underlying” changing strengths and directions of the main correlations between DOC, nitrate and discharge on different time scales resulting from severe forest management interventions (here deforestation). This information provides new valuable impact insights for decision making into such forest management interventions.

Paralytic Shellfish Toxins of Pyrodinium bahamense (Dinophyceae) in the Southeastern Gulf of Mexico.

In September and November 2016, eight marine sampling sites along the coast of the southeastern Gulf of Mexico were monitored for the presence of lipophilic and hydrophilic toxins. Water temperature, salinity, hydrogen potential, dissolved oxygen saturation, inorganic nutrients and phytoplankton abundance were also determined. Two samples filtered through glass fiber filters were used for the extraction and analysis of paralytic shellfish toxins (PSTs) by lateral flow immunochromatography (IFL), HPLC with post-column oxidation and fluorescent detection (FLD) and UHPLC coupled to tandem mass spectrometry (UHPLC-MS/MS). Elevated nutrient contents were associated with the sites of rainwater discharge or those near anthropogenic activities. A predominance of the dinoflagellate Pyrodinium bahamense was found with abundances of up to 104 cells L-1. Identification of the dinoflagellate was corroborated by light and scanning electron microscopy. Samples for toxins were positive by IFL, and the analogs NeoSTX and STX were identified and quantified by HPLC-FLD and UHPLC-MS/MS, with a total PST concentration of 6.5 pg cell-1. This study is the first report that confirms the presence of PSTs in P. bahamense in Mexican waters of the Gulf of Mexico.

Co-application of biochar and pyroligneous acid improved peanut production and nutritional quality in a coastal soil

Coastal land is one of important marginal land types that have been considered as a potential reverse land source to alleviate the shortage of cultivated land. Biochar and pyroligneous acid have attracted much attention because of their good performance in improving the quality of infertile soil. However, the effect of co-application of biochar and pyroligneous acid on peanut production in coastal soil is poorly studied. In this work, a green-house experiment was conducted to compare the effects of individual and combined application of biochar (BC) and pyroligneous acid (PA) on the peanut yield and peanut kernel nutritional quality in a coastal soil, as well as soil properties, and soil microbiome. Compared with the individual application of BC or PA, the co-application of BC and PA dramatically increased peanut pod yield and amino acid contents. The ameliorated soil properties (e.g., water holding capacity) and elevated soil available nutrients (e.g., N, K and P) resulting from the co-application of BC and PA may contribute to the enhanced production of peanuts. High-throughput sequencing showed that both bacterial and fungal communities were altered regardless of individual or co-application, and co-occurrence network of bacterial community was significantly enhanced by the co-application of BC and PA. The abundances of soil beneficial bacteria (e.g. Arthrobacter, Blastococcus and Sphingomonas ) and beneficial fungi ( Humicola and Chaetomium ) were enhanced by the co-application of BC and PA. This study demonstrates that co-application of BC and PA is a potential strategy to reclaim coastal soil for peanut cultivation. • BC+PA enhanced peanut yield and nutritional quality in a coastal soil. • BC+PA improved soil properties and increased soil nutrient availability. • BC+PA shifted soil microbial community and enhanced abundance of beneficial taxa. • Co-occurrence network of bacterial community was enhanced by the co-application.

Yukon River incision drove organic carbon burial in the Bering Sea during global climate changes at 2.6 and 1 Ma

Abstract. River erosion affects the carbon cycle and thus climate by exporting terrigenous carbon to seafloor sediment and by nourishing CO2-consuming marine life. The Yukon River–Bering Sea system preserves rare source-to-sink records of these processes across profound changes in global climate during the past 5 million years (Ma). Here, we expand the terrestrial erosion record by dating terraces along the Charley River, Alaska, and explore linkages among previously published Yukon River tributary incision chronologies and Bering Sea sedimentation. Cosmogenic 26Al/10Be isochron burial ages of Charley River terraces match previously documented central Yukon River tributary incision from 2.6 to 1.6 Ma during Pliocene–Pleistocene glacial expansion, and at 1.1 Ma during the 1.2–0.7 Ma Middle Pleistocene climate transition. Bering Sea sediments preserve 2–4-fold rate increases of Yukon River-derived continental detritus, terrestrial and marine organic carbon, and silicate microfossil deposition at 2.6–2.1 and 1.1–0.8 Ma. These tightly coupled records demonstrate elevated terrigenous nutrient and carbon export and concomitant Bering Sea productivity in response to climate-forced Yukon River incision. Carbon burial related to accelerated terrestrial erosion may contribute to CO2 drawdown across the Pliocene–Pleistocene and Middle Pleistocene climate transitions observed in many proxy records worldwide.

Response of calcareous nannoplankton to the Paleocene–Eocene Thermal Maximum in the Paratethys Seaway (Tarim Basin, West China)

The Paleocene-Eocene Thermal Maximum (PETM) was a rapid global warming occurred 56 million years ago and has been widely viewed as an ancient analogue to the ongoing warming driven by anthropogenic CO 2 emissions. The complete and continuous Paleogene shallow marine strata well preserved and outcropped in the Tarim Basin, northwestern China are ideal to study the paleoenvironmental change of the Paratethys Seaway during the PETM. To date, no high-resolution calcareous nannofossil biostratigraphy has been performed for the PETM interval in the Tarim Basin. Outcrop samples taken from the Qimugen Formation in the Kuzigongsu section contain abundant, moderately well preserved calcareous nannofossils, allowing for the establishment of a high-resolution biostratigraphic framework. Overall, 73 species of calcareous nannofossils from 33 genera were observed, with the dominant species including Coccolithus pelagicus , various Toweius species, Pontosphaera exilis , and Micrantholithus flos. The five calcareous nannofossil datums allow for the recognization of nannofossil Zone NP6 through Zone NP10. The common occurrence of shallow-water taxa ( Micrantholithus ) throughout the section suggests a middle to outer neritic setting as the depositional environment of the Kuzigongsu section. The stratigraphic distribution of “excursion taxa” ( Coccolithus bownii, Discoaster araneus , D. acutus, Rhomboaster spp.) is consistent with the range of negative excursions in δ 13 C carb and δ 18 O carb , indicating that these “excursion taxa” are micropaleontological markers for identifying the presence of the PETM in the Paratethys Seaway. During the PETM, the deteriorated preservation and extremely low abundance of nannofossils and near-zero wt% CaCO 3 values suggest that ocean acidification occurred in the shallow water of the Paratethys Seaway. In addition, a significant increase in the species Neochiastozygus junctus , which is a high productivity indicator suggests increased surface ocean productivity. Higher primary productivity may be triggered by enhanced continental weathering delivering increased nutrient through river runoff. • A new, shallow marine Paleocene–Eocene Thermal Maximum (PETM) record was discovered in the eastern Tethys. • High-resolution calcareous nannofossil biostratigraphy across the PETM was established. • The PETM “excursion taxa” are marker species for identifying PETM record in the eastern Tethys. • Low pre- and syn -PETM carbonate contents were attributed to ocean acidification and terrestrial dilution. • Marine productivity increased during the PETM due to elevated nutrient input from continental weathering.

The spatial organization of CAFOs and its relationship to water quality in the United States

• Applied Nearest Neighbor Index and Moran’s I to quantify the spatial pattern of AFOs. • Watersheds with higher AFO NNI were associated with elevated nutrient levels. • Clustering of smaller farms (less regulated) also corresponded to high nutrients. • Results help to inform management of AFOs and other pollutant sources. Large animal operations in the United States (US) have expanded in recent decades as a solution for meeting increasing food demand. These operations can release large amounts of organic matter and nutrients into the environment, potentially impacting water quality conditions of nearby waterbodies. Often referred to as animal feeding operations (AFOs) or CAFOs (concentrated AFOs) based on nomenclature in federal regulations, these operations are usually clustered in space, which may intensify the impacts observed. However, the influence of the known spatial aggregation of CAFOs on water quality conditions has not been evaluated. This study investigates the spatial organization of CAFOs and its relationship to water quality conditions. We hypothesized that watersheds with clustered CAFOs are likely to be associated with higher concentrations of Total Phosphorus (TP) and Total Nitrogen (TN) in the US. We gathered and digitized CAFO locations in 16 US states and used TP and TN concentration data to evaluate our hypothesis. We calculated the flow-weighted mean concentration of TN and TP from 2005 to 2014 and averaged those values per season. We used the nearest neighbor index (NNI) to determine the spatial pattern (i.e., clustering or dispersed) of CAFOs per watershed and its significance level. Additionally, for states with animal number information per farm, we performed a Local Moran’s I analysis to understand if the clustering of CAFOs with a low or high number of animals relates to the TP and TN concentrations of each nearest water quality station. Overall, we found that watersheds with significant clustering patterns were associated with higher TP and TN levels. Seasonally, this finding also held principally during spring and summer seasons, when manure tends to be land applied. Our Local Moran’s I analysis also revealed that the clustering of smaller and medium-sized farms, usually less regulated, is associated with elevated TP and TN concentrations. This reveals that the small, yet potentially unregulated farms could be highly impactful to the environment, which warrants further study. Given the lack of information on the influence of CAFO clustering (and other pollutant source clustering) on water quality and that most states do not regulate emitters based on this aspect, our outcomes advance the knowledge of how these entities may be driving changes to the environment. This study also brings insights into new water quality modeling approaches and supports future policy decisions.

Assessing nutrient budget of ungauged catchment using intermittent water quality markers

This study is a preliminary spatial-temporal assessment method of the ungauged catchment to determine the variation in water quality (WQ) and the land use influence on river basins’ health. The intermittent WQ data, the principal component analysis, and the redundancy analysis were used to evaluate the (dis)similarity among the 10 ungauged streams and their significance in the entire catchment. These revealed some similarities/differences in nutrient pollution and latent land-use influence on the streams’ health. There were similarities between R6-R7, R9-R10, among R1 to R4 basins, while R5 and R8 had distinct variances in their WQ dynamics. The intensive vegetable and rice production in R5, R7, R8, R9, and R10 basins were the major sources of high nutrient concentrations. The unique variations, especially in R5 and R8 basins could be attributed to other different pollution sources. Hence, it’s of great significance to carry out comprehensive research in the above 5 river basins. That is the efficiency of management practices, identification of pollution sources, and the extent to which the elevated nutrients in the streams interact with biota within the river regime. This research offers a method to evaluate WQ dynamics in relation to human interferences in river basins of a catchment with limited data under similar climatic conditions.

Improved fertilization efficiency of manure compost obtained by using oil shale semicoke as the bulking agent

Oil shale semicoke is a kind of solid waste produced during the retorting process of oil shale, which could cause environmental pollution without reasonable disposing. In our previous study, the abandoned semicoke was recycled as bulking agent to reduce the nitrogen loss and greenhouse gases emission during composting. But influences of the obtained semicoke-blended compost on soil properties and plant growth remained unclear, which would be discussed in this study. Through leaching experiments, it was found that the N/P/K retention capacity of soil mixed with semicoke-blended compost significantly increased for the good nutrients sorption capacity of oil shale semicoke. Subsequently, germination test showed the germination index of semicoke-blended compost could attain 120%, implying its low phytotoxicity. And pot experiments exhibited the biomass of cress and Brassica rapa significantly increased by 2–4 times when applying semicoke-blended compost as fertilizer, exhibiting its great benefits to plants. For the increase of crop yield, it was closely related to their elevated nutrients uptake efficiency, also might be related to the improved soil microbial community and activity as the microbial analysis indicated. Finally, results of pollutant detection showed the concentration of polycyclic aromatic hydrocarbons, Cr, As, Cd and Pb in the mature semicoke-blended compost obtained through composting was 2.82, 95.30, 5.95, 0.34 and 14.45 mg kg−1 respectively, meeting the standard for soil application. The research suggests composting could be an effective method for the harmless disposing and resource recycling of oil shale semicoke waste.

Phosphorus addition decreases soil fungal richness and alters fungal guilds in two tropical forests

Soil microbes regulate key functions of terrestrial ecosystems, but the effects and underlying mechanisms of elevated nutrient inputs on soil microbial diversity in tropical forests remain unclear. We evaluated the effects of seven-year nitrogen (N) and phosphorus (P) additions on soil microbial diversity in two tropical montane rainforests (P-limited primary forest and N-limited secondary forest). The results showed that soil bacterial richness was not sensitive to N or P addition, whereas soil fungal richness decreased under P and combined N and P additions. Furthermore, P inputs shifted soil fungal community composition: the relative abundance of mutualistic fungi increased and that of saprotrophic fungi decreased. The underlying mechanisms of these effects differed in the two forests. In the P-limited primary forest, the reduction in soil fungal richness was mainly related to a negative microbial interaction between microbial species and a stimulation in plant productivity. In the N-limited secondary forest, P inputs increased soil N and P imbalance, which caused a decline in the fungal richness. Overall, anthropogenic P enrichment could reduce soil fungal richness and alter fungal functional guilds in tropical forests, which will have divergent consequences on plant productivity and microbial functioning.

Carbonate platform drowning caught in the act: The sedimentology of Saya de Malha Bank (Indian Ocean)

AbstractMesophotic reefs, hardgrounds and current‐controlled pelagic to hemipelagic carbonates are facies marking carbonate platform drowning successions, irrespective of the factors controlling this evolution. A modern analogue of a carbonate platform in a state of drowning, where these facies occur has not been properly reported on to date. In the present study, the sedimentary environments of the Saya de Malha Bank are characterized using a multi‐disciplinary approach including sedimentology, hydroacoustics, seismics and oceanography. The Saya de Malha Bank edifice with a surface of 40 808 km2 is located in the tropical Indian Ocean and lies in a water depth of 8 to 300 m extending from the surrounding more than 2000 m deep ocean floor, with no reef reaching the sea surface. Mesophotic coral and red algal facies co‐exist with hemipelagic and bioclastic sands, together with a hardground. Ocean currents and internal waves are identified as major sedimentological controlling factors in the absence of elevated nutrient influx. Many features distributed along the present‐day Saya de Malha Bank were described from studies presenting fossil examples of carbonate platform drowning. The results herein can therefore be applied to other drowning examples, in some cases allowing for more accurate interpretation of the stratigraphic record.