Increased Nutrient Levels Research Articles

Bioponics—An Organic Closed-Loop Soilless Cultivation System: Yields and Characteristics Compared to Hydroponics and Soil Cultivation

Sustainable food production has become increasingly important. Soilless cultivation systems offer several advantages, such as water and nutrient use efficiency, and can be implemented where traditional agriculture is impossible. Bioponic systems use locally or regionally available nutrient sources from organic waste streams (either fluid or solid) and can thus contribute to closing nutrient cycles locally. Bioponics harnesses the metabolic processes of microorganisms which release nutrients from organic matter. This study aimed to set up a bioponic system, by using biogas digestate concentrate and biochar as nutrient sources, and promoting nutrient release from the organic sources by including a biofilter in the system. The development of water quality, plant growth, and quality was monitored extensively. In addition, the influence of either the fungal biocontrol agent Trichoderma atrobrunneum or UV-C treatment of the nutrient solution on plant health and growth was investigated. Three cultivation cycles with Lactuca sativa (“HAWKING” Salanova®) in bioponic (BP), hydroponic (HP), and soil (SO) cultivation were performed. The study showed that healthy lettuces could be produced in BP systems, using a biogas digestate concentrate and biochar as nutrient sources, despite salt accumulation in the nutrient solution. In plant sap analyses, lettuces cultivated in BP systems contained less nitrate but more ammonium and chloride. The yield of the lettuces grown in the BP systems was intermediate, compared to the HP and the SO. The fungus, T. atrobrunneum, strain, T720, survived in soil and soilless cultivation systems. Compared to the HP and the SO systems, the shoot height of lettuces grown in the BP system, with the application of Trichoderma, was significantly increased. In SO systems with Trichoderma application, a significantly higher chlorophyll and flavonoid content, but significantly lower shoot height was observed. The fresh weight of lettuce roots was significantly higher in HP systems with Trichoderma treatment. Cultivating plants by using organic waste streams requires commitment and experience from producers. In BP systems, a biofilter (either within the system or externally, to increase nutrient levels) can help to rapidly convert the ammonium-rich fertilizer to plant-available nutrients. Unlike conventional HP systems, in BP systems, nutrients are released slowly over time, requiring close monitoring and adjustments. In conclusion, healthy lettuces for human consumption can be produced in BP systems, and the application of the biocontrol agent used has some beneficial influence on plant growth.

Assessing the Native Plant Species for Phytoremediation of Freshwater Bodies in Southern Ontario, Canada

Many Canadian freshwater ecosystems are polluted by agricultural runoff, impairing their function with increased nutrient levels. Here, we simulated the water filtration function of wetlands, which uses aquatic plant species to create a phytoremediation system that can address the contamination of freshwater ecosystems with excess nutrients. We collected the water samples from three of Ontario’s freshwater bodies: the Holland Marsh, a highly agricultural area; the Nottawasaga River, a river in a rural area and part of a greater Nottawasaga watershed and Lake Ontario, near industrial sites in the Niagara region. To filter nitrogen (N), phosphorus (P) and potassium (K) from the collected samples, we determined the effectiveness of five local wetland and agricultural plant species: duckweed (Lemnoideae), watercress (Nasturtium officinale), coontail (Ceratophyllum demersum), thyme (Thymus praecox) and parsley (Petroselinum crispum). During a five-month experiment, plants were grown in collected water samples to determine their ability to uptake N, P and K. Along with monitoring their effectiveness in lowering nutrient levels, we tracked the health and growth of each plant species. The results showed that duckweed was the most tolerant to high nutrient concentrations and the most effective at overall nutrient reduction. From the Holland Marsh sample with the highest nutrient concentrations among all collected samples, the duckweed reduced N, P, and K by 11%, 53%, and 21%, respectively, compared to the control sample (i.e., with no plant). This filtration system allows for ecosystem restoration and prevention of further damage and contamination from agricultural runoff and nutrient pollution.

The Effect of Adding Vinasse for Biochar Production from Bagasse by Pyrolysis Method

The increasing industrial waste was caused problems for the environment. Bagasse is a solid waste produced from the sugar industry. Vinasse is bioethanol industry liquid waste from molasses which contains much nutrients. The vinasse and bagasse in this study was developed into biochar. This study aimed to determine the effect of vinasse addition on biochar characteristics. The yield and characteristics of the biochar were then compared. Based on gravimetric, pH, and SEM-EDX analysis, the result indicated that adding vinasse to the biochar was increasing yield, water content and ash content, lowering pH, and tend to increase nutrient levels (carbon, nitrogen, and potassium). The biochar produced from bagasse and vinasse by pyrolysis had a yield of 6.682-9.406%; water content of 7.0-8.2%; ash content of 4.8-13.6%; at pH 8.4-88; carbon content (C) of 65.07-80.88%; nitrogen (N) content of 2.06-8.66%; and potassium (K) levels of 0.00-2.15%, while phosphorus (P) levels were not detected in SEM-EDX analysis. Based on the consideration of the highest levels of nitrogen and potassium elements needed by plants, the optimum biochar was obtained from bagasse with a vinasse of 7.5%.

Gross pelagic primary production in the Ems-Dollard estuary

Anthropogenic changes to estuaries, usually highly productive systems, may result in increased turbidity levels, suppress pelagic primary production and negatively affect ecosystem functions. The Ems-Dollard estuary, enclosed between the Netherlands and Germany, is such an estuary with a long history of human induced changes. From the mid-19th century until 1992, discharges of potato starch and straw-board industry waste water, with high contents of organic matter, negatively affected oxygen concentrations and increased nutrient levels of the system. The growing awareness of the deteriorating effects of these discharges on the ecosystem invoked a large research program, BOEDE, between 1976 and 1980. The aim of the current paper was to establish the recent gross pelagic primary production, to compare the results with the late seventies data and to relate possible changes to environmental variables such as suspended matter and nutrients. To this end, six stations from the North Sea into the inner area of the Dollard were visited 39 times in 2012–2013. During each sampling cruise, a so-called PocketBox, containing a number of sensors, provided a high spatial data resolution between stations. At each station, samples were collected for carbon fixation incubations using 14C. Average chlorophyll-a concentrations as reported in this study were lower compared to 1978–1980 for the seaward stations, and higher for the most inward station in 2012 and almost similar in 2013. Light attenuation coefficients in the outer areas were lower in 2012–2013 (1.22 m−1) compared to the values reported in the period 1976–1980 (1.59 m−1), indicating somewhat less turbid conditions. For the two other stations, light attenuation coefficients in the present study were similar to the late seventies' values, for the station near the entrance of the Ems River in the Ems-Dollard area, the coefficient was substantially higher. Pelagic primary production in the 2012–2013 period was about 120 g C m−2 y−1, mainly determined by the most seaward areas. The largest differences in gross primary production in the current study compared to the 1976–1980 period were found at the seaward stations where production in the late seventies was about 60% higher. In the Dollard-area, production hardly changed since the late seventies, but also stations near the Ems-river entrance into the Ems-Dollard area showed a clear decrease. Changes at the inward stations are to be contributed to an increased turbidity; the decrease at the outer areas to a decreased nutrient level, especially dissolved phosphorus and silicate, but possibly also nitrogen.

Biomass composite with exogenous organic acid addition supports the growth of sweet sorghum (Sorghum bicolor 'Dochna') by reducing salinity and increasing nutrient levels in coastal saline-alkaline soil.

In coastal saline lands, organic matter is scarce and saline stress is high. Exploring the promotion effect of intervention with organic acid from biological materials on soil improvement and thus forage output and determining the related mechanism are beneficial to the potential cultivation and resourceful, high-value utilization of coastal mudflats as back-up arable land. Three exogenous organic acids [humic acid (H), fulvic acid (F), and citric acid (C)] were combined with four kinds of biomass materials [cottonseed hull (CH), cow manure (CM), grass charcoal (GC), and pine needle (PN)] and applied to about 0.3% of medium-salt mudflat soil. The salinity and nutrient dynamics of the soil and the growth and physiological differences of sweet sorghum at the seedling, elongation, and heading stages were observed under different treatments to screen for efficient combinations and analyze the intrinsic causes and influencing mechanisms. The soil salinity, nutrient dynamics, and forage grass biological yield during sweet sorghum cultivation in saline soils differed significantly (p < 0.05) depending on the type of organic acid-biomass composite applied. Citric acid-pine needle composite substantially reduced the soil salinity and increased the soil nutrient content at the seedling stage and improved the root vigor and photosynthesis of sweet sorghum by increasing its stress tolerance, allowing plant morphological restructuring for a high biological yield. The improvement effect of fulvic acid-pine needle or fulvic acid-cow manure composite was manifested at the elongation and heading stages. Citric acid-pine needle composite promoted the growth of saline sweet sorghum seedlings, and the effect of fulvic acid-pine needle composite lasted until the middle and late stages.

Understanding the impact of waste disposal sites on soil quality for agricultural production: A case study of the Kiteezi landfill, Uganda

AbstractLeachate from waste disposal sites (WDS) can significantly affect the soil physical, chemical and biological qualities, reducing soil health and agricultural productivity. However, there is a paucity of data on soil quality for understanding soil health impact due to WDS in Uganda. This study's aim was to understand, using the Kiteezi landfill site, how WDS impact soil properties. Soil samples were collected over 4 months in and around the landfill from three locations, and the soil quality data of the nearby area were used as baseline data for assessing the impact on soil due to WDS in the area. There were significant increases in the concentration of all studied parameters at the landfill except total N. The concentrations of ammonium (14.84 ± 1.76 mg/kg), nitrate (127.96 ± 18.36 mg/kg), and pH (7.8) were above the optimum levels. The levels of available P (181.4 ± 28.9 mg/kg) and exchangeable bases; K (2.23 ± 0.24 mg/kg), Na (1.17 ± 0.14 mg/kg), Mg (3.35 ± 0.3 mg/kg) and Ca (14 ± 1.1 mg/kg) cmol (+)/kg were optimal for plant growth. The calculated CEC of 20.75 cmol (+)/kg) showed that soils have a good potential to supply plant nutrients. Heavy metal levels were still below the permissible limit. Hence, the study shows that although WDS may contribute to the increase of soil fertility, they can potentially reduce the overall productivity of soil by increasing nutrient levels beyond optimum levels.

The response of benthic diatom community to anthropogenic eutrophication of a river basin under agricultural influence in NE China

Anthropogenic eutrophication has universally threatened river ecological health and has been a key issue in river conservation. Agricultural sewage, which leads to increased nutrient levels and results in the loss of ecological function and biodiversity, results from the growth of agricultural activity and human populations. Consequently, attention has increasingly been focused on developing a relevant tool to describe the relationship between the biotic communities and anthropogenic eutrophication. The benthic diatom community has been widely used as an effective tool for indicating the ecological status of river systems especially in the context of recent international Water Framework Directive policies (WFD). In this study, a statistical method consisting of trophic status index (TSI), Specific Polluosensitivity Index (IPS), Descy Index (DES), redundancy analysis (RDA), and the geographic information system (GIS) technique was conducted to explore the response of benthic diatom community to anthropogenic eutrophication. Initially, the TSI, IPS and DES were determined to differentiate the trophic gradient along a gradient in agricultural intensity. Subsequently, RDA was used to identify spatial distribution patterns of environmental parameters and benthic diatom communities. Finally, the RDA scores as calculated and spatially interpolated were applied to GIS technology to reveal the response of benthic diatom communities to anthropogenic impacts along the trophic gradient. Our results revealed that the studied basin mostly exceeded the eutrophic level. Two different patterns of diatom communities response to ecological gradient were identified based on RDA, one representing the agriculture eutrophication discharges in electrical conductivity (EC) and the other representing organic pollution as chemical oxygen demand (COD). The developed method in this study highlight that the EC was more effective than the nutrient indices in determining diatom distribution in a eutrophic agriculturally-influenced river system.

Optimization of Neochetina eichhorniae Warner and Neochetina bruchi Hustache for the management of water hyacinth, Eichhornia crassipes (Mart.) Solms in the Central Rift Valley lakes through the use of different nutrient levels in Ethiopia

Water hyacinth, Eichhornia crassipes (Mart.) Solms, is an alien invasive weed in Ethiopia that has been established in freshwater bodies. Eichhornia crassipes negatively affects water transportation, fishing and biodiversity among others. Hence, implementation of eco-friendly management option such as biological control is a mandatory. The weevils, Neochetina eichhorniae Warner and N. bruchi Hustache, are the principal biocontrol agents against E. crassipes in their native ranges and have been introduced to Ethiopia for the management of the weed. The weevils and their host are affected by the nitrate and phosphate contents of the water body. Thus, this study was conducted to investigate the effect of N. bruchi and N. eichhorniae in relation to water nutrient contents in the management of E. crassipes. The experiment was conducted in a randomized complete block design with three replications in a 4x4x3 factorial arrangement. Eight weeks after the treatments’ application, the population of the weevils and E. crassipes growth parameters were recorded. The larval population was significantly (p &lt; 0.05) affected only by the interaction effect of N. bruchi and the nutrient levels. Among the treatments, the highest mean number of larvae was found on the plants given high and medium nutrient levels. There was also a significant interaction (p &lt; 0.05) between the two weevils adult density. The mean number of emerged adult density of the weevils increased with increasing nutrient levels. The nutrients and weevils exhibited a significant interaction effect on E. crassipes leaf scarring and petiole tunnel. Leaf scarring at the highest weevil density and nutrient level was sixfold greater than that at the lower nutrient level and weevil density. The tunnel length of the weed was threefold higher at the highest nutrient level regardless of the weevil density. The growth parameters of E. crassipes were found to be greater at high nutrient level, except for the mean number of flowers. Conversely, the growth parameters showed a non-uniform trend with the increasing density of the weevils. The current result suggests reduction in E. crassipes could be achieved by lowering the water nutrient levels and use of N. bruchi and N. eichhorniae.&#x0D;

Introduction of exotic species Sonneratia apetala alters diazotrophic community and stimulates nitrogen fixation in mangrove sediments

Mangrove restoration by exotic mangrove species Sonneratia apetala has been practiced as a strategy to reconstruct mangrove wetlands. Diazotrophs in mangrove sediment are nitrogen suppliers for mangrove ecosystems. However, the response of sediment diazotrophs, especially their nitrogen fixation rates, to the introduction of exotic S. apetala remains unclear. In the present study, we compared the variations in sediment physicochemical properties, N2 fixation rate, and the composition of total bacterial and diazotrophic communities in mangrove sediments between exotic species (S. apetala) and three native species (i.e., Aegiceras corniculatum, Lumnitzera racemosa, and Rhizophora apiculata). Our results indicated that the introduction of exotic S. apetala significantly (P < 0.05) increased nutrient levels (including TC, TN, and TS) and improved the N2 fixation rate in sediments. Though S. apetala introduction had not caused significant changes in bacterial and diazotrophic alpha diversity, their community structure and composition were altered. The dominant diazotrophic groups were sulfur-oxidizing (SOB) and sulfate-reducing (SRB) bacteria. The relative abundance of Chromatiaceae (affiliated with SOB) significantly increased (P < 0.05), while the relative abundance of Desulfuromonadaceae (affiliated with SRB) decreased in S. apetala sediments. In addition, several SOB and SRB groups were identified as putative keystone taxa by network analysis, suggesting that SOB/SRB groups potentially played a central role in the biogeochemical cycles involving nitrogen (N) and sulfur (S) of the mangrove ecosystem. Redundancy analysis revealed that C/N and NH4+-N were the key factors (P < 0.05) driving sediment diazotrophic communities. This study provides new insights into the ecological impact of exotic S. apetala introduction, which has important implications for the sustainable management and restoration of mangrove ecosystems.

Six decades of field observations reveal how anthropogenic pressure changes the coverage and community of submerged aquatic vegetation in a eutrophic lake

Six decades field observation data series on submerged aquatic vegetation (SAV), water level and water quality from Lake Taihu were compiled to reveal the dynamics in coverage and species composition of SAV and their anthropogenic drivers. We found that both SAV species composition and coverage area declined significantly in Lake Taihu during the period, and the increasing nutrient levels and water level as well as decreasing water clarity were responsible for these change trends. Specifically, the decrease in species richness could be particularly well predicted by total nitrogen (TN) and the ratio of water clarity (i.e., Secchi disk depth (SDD)) to water level (WL), contributing 47.3 % and 32.3 %, respectively, while the coverage of macrophytes was most strongly related to the water level, accounting for 70.1 % of the variation. A classification tree analysis revealed a threshold of TN of 3.2 mg/L and SDD/WL of 0.14 that caused a shift to a eutrophic low-macrophyte dominated state. Our results highlight that SDD/WL must be improved for SAV recolonization, rather than merely reducing nutrient input and regulating water level. Our findings provide scientific information for lake managers to prevent plant degradation in macrophyte-dominant lakes and facilitate a shift to a macrophyte-dominant state in eutrophic lakes.

Growth, yield and economics of fodder maize (Zea mays) as influenced by Jeevamrutha formulations under varying nutrient levels

A split plot experiment was conducted at research farm of Agronomy Section, ICAR–National Dairy Research Institute, Karnal, Haryana during kharif 2018–19 to evaluate various jeevamrutha formulations under the varying nutrient levels in fodder maize (Zea mays L.). In main plot four nutrient levels [Control (0), 50, 75 and 100% RDF] and in sub-plot, five jeevamrutha formulations [Control (without jeevamrutha), water based jeevamrutha @1000 l/ha, water based jeevamrutha @1500 l/ha, whey based jeevamrutha @1000 l/ha and whey based jeevamrutha @1500 l/ha] were taken as treatments and replicated thrice. Better growth attributes, viz. plant height, number of leaves per plant, stem girth and leaf:stem ratio were observed with increased nutrient levels. Application of 50, 75 and 100% RDF resulted in 35.01, 61.21 and 74.19% higher green fodder yield (GFY) over control. Jeevamrutha (whey/water based) formulations significantly improved growth. Significantly higher dry matter yield (DMY) (11.65 t/ha) was obtained with 100% RDF. Whey based jeevamrutha formulation @1500 l/ha ((52.83 and 11.09 t/ha) closely followed by water based jeevamrutha formulation @1500 l/ha (51.38 and 10.79 t/ha) resulted in higher GFY and DMY, respectively. The highest gross returns and net returns were obtained in 100% RDF with whey based jeevamrutha @1500 l/ha (`94.89 and 70.32 × 103/ha, respectively). Maximum benefit:cost ratio (2.89) was recorded in 100% RDF and water based jeevamrutha formulation @1500 l/ha. Interaction effect between jeevamrutha formulation and nutrient levels suggested that application of jeevamrutha formulation @1500 l/ha in both forms (Whey and water) can save 25%nutrient dose.

The influence of seabirds on their breeding, roosting and nesting grounds: A systematic review and meta-analysis.

Seabird species world‐wide are integral to both marine and terrestrial environments, connecting the two systems by transporting vast quantities of marine‐derived nutrients and pollutants to terrestrial breeding, roosting and nesting grounds via the deposition of guano and other allochthonous inputs (e.g. eggs, feathers).We conducted a systematic review and meta‐analysis and provide insight into what types of nutrients and pollutants seabirds are transporting, the influence these subsidies are having on recipient environments, with a particular focus on soil, and what may happen if seabird populations decline.The addition of guano to colony soils increased nutrient levels compared to control soils for all seabirds studied, with cascading positive effects observed across a range of habitats. Deposited guano sometimes led to negative impacts, such as guanotrophication, or guano‐induced eutrophication, which was often observed where there was an excess of guano or in areas with high seabird densities.While the literature describing nutrients transported by seabirds is extensive, literature regarding pollutant transfer is comparatively limited, with a focus on toxic and bioaccumulative metals. Research on persistent organic pollutants and plastics transported by seabirds is likely to increase in coming years.Studies were limited geographically, with hotspots of research activity in a few locations, but data were lacking from large regions around the world. Studies were also limited to seabird species listed as Least Concern on the IUCN Red List. As seabird populations are impacted by multiple threats and steep declines have been observed for many species world‐wide, gaps in the literature are particularly concerning. The loss of seabirds will impact nutrient cycling at localized levels and potentially on a global scale as well, yet it is unknown what may truly happen to areas that rely on seabirds if these populations disappear.

Do foliar applications of nickel increase urease activity and nutrient levels in pecan leaflets?

Nickel (Ni) deficiency limits the production of pecan. Concentrations of mineral nutrients and urease activity in leaflets of young pecan plants cv. Pawnee were evaluated in response to foliar applications of Ni as Ni sulfate or Ni citrate, or as chelates with EDDHA, EDTA, or DTPA. Significant variations were found in N-total concentration with Ni-EDDHA (27.17 ± 0.98 g/kg) and Ni-sulphate (28 ± 0.89 g/kg), where the latter together with Ni-citrate were high in phosphorus concentrations. Levels of Ni&lt;sup&gt;2+&lt;/sup&gt; (3.70 mg/kg), Mn&lt;sup&gt;2+&lt;/sup&gt; (222.73 mg/kg) and Zn&lt;sup&gt;2+&lt;/sup&gt; (38.69 mg/kg) were all increased in leaflets sprayed with Ni-EDDHA but the Mn&lt;sup&gt;2+&lt;/sup&gt; concentrations were similar for leaflets sprayed with Ni-sulphate. The Ni-DTPA spray significantly reduced foliar Fe&lt;sup&gt;2+&lt;/sup&gt; concentration (73.66 ± 3.44 mg/kg). No significant effects of the sprays were observed on the concentrations of total chlorophyll or carotenoids. The plants sprayed with Ni-EDDHA showed significant increases in leaflet area and leaflet dry weight and also in root dry weight. The urease showed maximum activity in leaflets sprayed with Ni-EDDHA, Ni-citrate and Ni-sulphate. This study suggests growers of the pecan should consider foliar sprays of Ni-EDDHA or Ni-sulphate to increase the levels of Ni in their trees if Ni is a growth-limiting factor.

Nucleation by isolated emergent native trees can push back the shade-intolerant invader Broussonetia papyrifera (L.) L'Hér. ex Vent.

The facilitatory role that isolated trees play in the regeneration of degraded areas that are not under the cover of invasive exotic plants is well recognized. In contrast, the influence of isolated trees in restoring sites invaded by exotic plants has hardly been studied. Such studies are needed because conditions that favor native tree regeneration under isolated trees, such as microclimate amelioration, increased nutrient levels, and facilitated dispersal, may also be favorable to certain species of exotic plants. Using transects, we studied species richness, abundance and resilience (as indicated by re-sprouting) of trees regenerating underneath the crowns of 15 isolated native trees that are emergent over a near continuous canopy of paper mulberry Broussonetia papyrifera in a degraded area of Mabira Forest, Uganda. Data collected beneath emergent tree crowns were matched by control data from the area immediately beyond the crowns. Native tree species abundance and richness were significantly higher beneath than beyond crowns; while the opposite was true of the density of B. papyrifera seedlings and saplings. Species richness was significantly higher beneath than beyond crowns for late-, but not early-succession trees. Polynomial regressions of species richness and abundance showed that B. papyrifera abundance increased significantly from stem bases to crown edges and leveled-off beyond crowns; while the density of native tree species was constant from stem bases to crown edges and decreased thereafter. Native tree species richness peaked at crown edges. The proportion of re-sprouts assigned to cutting of native tree species was significantly higher beyond than beneath crowns. We attribute the higher abundances and species richness of native species underneath crowns to both facilitation by isolated trees and the apparent shade-intolerance of B. papyrifera. Significantly higher levels of re-sprouting by native tree species could be an indication that the regeneration underneath crowns is less resilient to disturbance than that beyond, or that less resilient species occur beneath crowns. Overall, the results suggest that in sites invaded by mulberry, isolated trees have potential to accelerate recovery of native tree species while suppressing mulberry. Peaking of species richness at crown edges is not a commonly reported finding for isolated trees and needs to be further investigated.

Serotonergic neurons translate taste detection into internal nutrient regulation

The nervous and endocrine systems coordinately monitor and regulate nutrient availability to maintain energy homeostasis. Sensory detection of food regulates internal nutrient availability in a manner that anticipates food intake, but sensory pathways that promote anticipatory physiological changes remain unclear. Here, we identify serotonergic (5-HT) neurons as critical mediators that transform gustatory detection by sensory neurons into the activation of insulin-producing cells and enteric neurons in Drosophila. One class of 5-HT neurons responds to gustatory detection of sugars, excites insulin-producing cells, and limits consumption, suggesting that they anticipate increased nutrient levels and prevent overconsumption. A second class of 5-HT neurons responds to gustatory detection of bitter compounds and activates enteric neurons to promote gastric motility, likely to stimulate digestion and increase circulating nutrients upon food rejection. These studies demonstrate that 5-HT neurons relay acute gustatory detection to divergent pathways for longer-term stabilization of circulating nutrients.

Proliferation of Chondrodonta as a proxy of environmental instability at the onset of OAE1a: Insights from shallow‐water limestones of the Apulia Carbonate Platform

AbstractChondrodonta is an opportunistic, oyster‐like bivalve, common in shallow‐water carbonates of the Cretaceous Tethyan Realm. Despite its high abundance and widespread geographic distribution, the precise relationship between the early Aptian proliferation and environmental perturbations resulting from the Oceanic Anoxic Event 1a (OAE1a), has not been investigated. Stratigraphic and geochemical analyses of the lower Aptian Chondrodonta bedsets within the inner platform limestones of the Apulia Carbonate Platform (Gargano Promontory, southern Italy) are conducted to assess the environmental controls on the Chondrodonta proliferation and its timing and causal relationship to OAE1a. Chondrodonta occurs with sparse to common individuals within requieniid rudist floatstone–rudstones, forms monospecific biostromes during the early phase of stressed environmental conditions and then rapidly disappears at the peak of OAE1a. It proliferates in dysoxic seawater with relatively increased trophic sources, which correlate to increasing nutrient levels in the nearby pelagic realm. Chondrodonta‐rich beds are associated worldwide with the onset of OAE1a and occur in a transitional context between a stable and a strongly stressed environment, where the opportunistic behaviour of Chondrodonta is rather efficient. Increasing nutrient load and unstable environmental conditions right below the peak of OAE1a created an environmental ‘window’ favourable for Chondrodonta to proliferate, outplaying the less tolerant benthos (for example, rudists). The occurrence, duration and position of the environmental window were controlled by local palaeogeographic and hydrodynamic settings (i.e. low energy, decreased seawater oxygenation and circulation). Further increase in inhospitable conditions, leading to OAE1a, constituted an upper threshold for Chondrodonta and allowed mesotrophic taxa like Bacinella–Lithocodium and orbitolinids to dominate the benthic communities. The present study suggests that the proliferation of Chondrodonta in shallow‐water platform carbonates can be used as proxy for the initial phase of ecological stress related to OAE1a.

Potentially peat‐forming biomass of fen sedges increases with increasing nutrient levels

Abstract Peat formation is a key carbon sequestration process in the terrestrial biosphere. In temperate fens, peat is mainly formed by below‐ground biomass of vascular plants. Nutrient availability in temperate fens is naturally variable, and nowadays increasing due to atmospheric deposition, runoff from agriculture and mineralization of peat caused by drainage. To maintain or restore peat formation, it is important to understand how increased nutrient availability influences the main controls of peat formation, that is, below‐ground biomass production and decomposition. We investigated above‐ and below‐ground biomass production and decomposition of five fen sedges (Carex spp.) grown under 12 different nutrient levels (realized with nitrogen amounts increasing exponentially across levels, with addition of phosphorous and potassium to ensure nitrogen limitation in each nutrient level) in a mesocosm experiment, designed to resemble a gradient of very low to very high nutrient availabilities in temperate fens. In addition, we measured nutrient stoichiometry in the biomass and related this to possible growth limitations and to root decomposition. Our results indicate that higher biomass production at higher nutrient levels was not offset by an increase in decomposition. Increase of above‐ and below‐ground biomass with higher nutrient levels was species‐specific. Decomposition of standardized plant material in mesocosms was not dependent on the species growing in the mesocosms and showed only slight, if any, variation with differing nutrient levels. Decomposition of roots grown under different nutrient levels was mainly correlated with species identity and root lignin:cellulose ratio. Our study suggests that the Carex spp. potentially peat‐forming root biomass, here defined as the root biomass which is not decomposed during one growing season, increases with increasing nutrient levels: higher root biomass production is not counteracted by increasing decomposition during the growing season. Based on this pattern of positive mass balance in five common sedge species with differing growth characteristics, we propose that sedge communities establishing after rewetting have the potential for renewed peat formation regardless of the prevailing trophic level. A free Plain Language Summary can be found within the Supporting Information of this article.

Land-use influence on the functional organization of Afrotropical macroinvertebrate assemblages

Studies investigating the effects of human activities on the functional organization of macroinvertebrate communities in tropical streams and rivers are very limited, despite these areas witnessing the greatest loss of natural forests globally. We investigated changes in taxon richness, numerical abundance and biomass of macroinvertebrate functional feeding groups (FFGs) in streams draining different land-use types in the Sosiani-Kipkaren River in western Kenya. Twenty-one sites in river reaches categorized as forested, mixed, urban or agricultural were sampled during the dry and wet seasons. Collected macroinvertebrates were identified to the lowest taxon possible (mainly genus) and classified into five major FFGs; collector-gatherers, collector-filterers, scrapers, predators and shredders. There were significant (p < 0.05) spatial variation in habitat quality, organic matter standing stocks, total suspended solids, electrical conductivity, dissolved oxygen, temperature and nutrient concentrations across land-uses, with forested sites recording lowest values in mean water temperature, electrical conductivity and nutrients while recording highest levels in dissolved oxygen concentrations. Responses in macroinvertebrates to changes in land-use varied with richness, abundance and biomass showing differences within FFGs. Biomass-based metrics responded more strongly to change in land-use while taxon richness was the least predictive, indicating replacement of taxa within FFGs across land-use types. Higher shredder abundance, biomass and richness were recorded in forested streams which were cooler with protected riparian areas and high biomass of coarse particulate organic matter. Collector-gatherers dominated agricultural and urban streams owing to an abundance of particulate organic matter and nutrients, while scrapers responded positively to increased nutrient levels and open canopy in mixed and agricultural streams where primary production and algal biomass was likely increased. Overall, this study provides further evidence of the effects of agricultural and urban land-uses on tropical streams and rivers and contributes to the use of macroinvertebrate FFGs as indicators of ecological health.

Can nutrient uptake by Carex counteract eutrophication in fen peatlands?

Ground- and surface-water-fed peatlands (i.e., fens) of temperate Europe face high anthropogenic nutrient loads from atmospheric deposition, agricultural catchment areas, and from peat decomposition, if drained. As a result, nitrogen loads may exceed a fen's natural nutrient removal capacity, leading to increased eutrophication of adjacent water bodies. Therefore, it is important to address possible means to decrease a fen's nutrient load, including nutrient uptake by fen plants. To assess how much fen plants can contribute to nutrient removal by uptake, nutrient stocks of above- and below-ground biomass need to be quantified. Therefore, we investigated nitrogen, phosphorous, and potassium uptake capacities of sedges (Carex species), which are common dominants in fen plant communities. We grew specimens of five Carex species with varying preferences in nutrient availability under controlled, different nutrient levels. We show that Carex above-ground biomass harvest can remove up to one third of a system's total nitrogen even at high loads of about 40 g nitrogen m−2. Species-specific differences in biomass production, rather than preferences in nutrient availability under natural conditions, were drivers of standing nutrient stocks: Highly productive species, i.e., C. acutiformis and C. rostrata, had highest nutrient standing stocks across all nutrient levels. Amounts of nutrients stored in shoots increased almost linearly with increasing nutrient levels, whereas below-ground nutrient stocks species-specifically increased, saturated, or decreased, with increasing nutrient levels. As a rough estimate, depending on the species, 6–16 cycles of annual above-ground harvest would suffice to decrease nitrogen concentrations from the highest to the lowest level used in this study. Overall, our results indicate that Carex biomass harvest can be an efficient means to counteract anthropogenic nitrogen eutrophication in fens.

Natural soil genesis in red mud and underlying microbial mechanism.

Soil genesis is important for ecological restoration of red mud disposal area. Soil genesis of red mud and the microbial mechanism were studied by analyzing the change of physicochemical and biochemical characteristics of red mud. We analyzed the microbial community structure in a red mud disposal area without any human-induced restoration through a space for time substitution approach. The results showed that, with the increases of storage time, the physical parameters of porosity, water-stable aggregates content, and mean weight diameter increased, but the bulk density decreased. The chemical parameters, including pH, electrical conductivity, acid neutralizing capacity, and exchangeable sodium percentage, decreased with increasing storage time. The bio-chemical parameters of total organic carbon, total nitrogen, available phosphorus, microbial biomass carbon and basal respiration increased, but the metabolic quotient decreased. The Shannon diversity index increased, and the dominant microflora in red mud changed from the oxygenic photosynthetic bacteria Cyanobacteria and thanaerobic anoxygenic phototrophic bacteria Chlorobi and Chloroflexi to Proteobacteria, Actinobacteria and Firmicutes. The ratio between eutrophic and oligotrophic bacteria substantially increased. The micromorphology results showed that the microorga-nism-red mud aggregates were formed through adsorption, linkage, intertwinement and package between red mud particles, microbial cells and their metabolites. The red mud biotope changed spontaneously from extreme and oligotrophic into soil-like under natural stockpiling. The soil genesis process was mediated by microbes through increasing nutrient level, decreasing alkalinity and sali-nity, and improving soil structure.