Nutrient Enrichment Research Articles

Burning poop: chemical composition and carbon dynamics of large herbivore dung burned in African savanna fires

Background Fire and herbivores are essential to savanna ecosystems, consuming vegetation and recycling nutrients. Fire volatilises some elements and makes others readily available through ash, while herbivores redistribute nutrients via dung (excrement, faeces). Aims We investigate, for the first time, fire’s role in consuming dung and affecting nutrient cycling. Methods We examined the chemical characteristics of wild large herbivore dung (buffalo, elephant, giraffe, wildebeest, zebra) burned during African savanna fires (Kruger National Park, South Africa) and estimated carbon and nutrients losses from dung burning. Key results Smouldering combustion of dung led to high carbon loss to the atmosphere (C: 41% and 4.1% in unburned and burned dung) and high enrichment of nutrients (e.g. Ca, P) and metals (e.g. Cu, Fe, Zn) in the burned residue. Flaming combustion of grass resulted in lower carbon loss (C: 43% and 23% in vegetation and ash), leaving more carbon in the ash and lower relative enrichment of other nutrients and metals. Conclusions Burned dung forms nutrient hotspots with physicochemical characteristics distinct from vegetation ash. Implications Taking dung from wild or domestic herbivores into account in fuel inventories can improve estimations of fire-related carbon emissions and provide better understanding of fire impacts on nutrients cycling.

Forb diversity globally is harmed by nutrient enrichment but can be rescued by large mammalian herbivory

Forbs (“wildflowers”) are important contributors to grassland biodiversity but are vulnerable to environmental changes. In a factorial experiment at 94 sites on 6 continents, we test the global generality of several broad predictions: (1) Forb cover and richness decline under nutrient enrichment, particularly nitrogen enrichment. (2) Forb cover and richness increase under herbivory by large mammals. (3) Forb richness and cover are less affected by nutrient enrichment and herbivory in more arid climates, because water limitation reduces the impacts of competition with grasses. (4) Forb families will respond differently to nutrient enrichment and mammalian herbivory due to differences in nutrient requirements. We find strong evidence for the first, partial support for the second, no support for the third, and support for the fourth prediction. Our results underscore that anthropogenic nitrogen addition is a major threat to grassland forbs, but grazing under high herbivore intensity can offset these nutrient effects.

Reservoir eutrophication in the Brazilian semiarid: modeling of sediment removal and control of external loads as remediation measures.

Eutrophication, driven by nutrient enrichment, poses a global challenge, impacting the ecosystem, water supply systems, and ultimately, human health. In this research, water unavailability due to phosphorus pollution was assessed in Brazilian semiarid reservoirs with data measured over a decade. Management strategies to control eutrophication were simulated using physical-mathematical modeling of the phosphorus budget in the water and sediment layers. The model parameters were calibrated from 1976 to 2021, and the results were validated by comparing measured and modeled duration curves of phosphorus concentration. Water unavailability due to phosphorus pollution occurred approximately 61% of the time, indicating the need for effective control strategies. Simulation of sediment removal when the reservoirs dry up showed potential to contribute to water quality in reservoirs with high emptying frequency, while external phosphorus load reduction proved to be more widely efficient. The variation in the effectiveness of the techniques among the studied reservoirs emphasizes the need for approaches adapted to the specific conditions. This work contributes to improve the understanding of phosphorus dynamics in reservoirs with high water level fluctuations and appropriate management measures to control eutrophication in dry environments.

Rivers Under Threat: Assessing the Ecological Impact of Macrolitter in the Leça River, Portugal

Rivers provide vital ecosystem services for populations. However, these ecosystems face several anthropogenic threats, including macrolitter pollution, and their impacts remain inadequately understood. This study aimed to evaluate the ecological status of the Leça river (northern Portugal) according to the elements defined by the Water Framework Directive (WFD) and to quantify marginal macrolitter as a new ecological tool for river water quality assessment. Physical, chemical, and biological (photosynthetic pigments; benthic macroinvertebrates) elements were quantified to evaluate the ecological status, of seven sites (P1 to P7) along the Leça river throughout four seasons (autumn/23, winter/24, spring/24, summer/24). Macrolitter was collected on the riverbank of each site and was quantified and categorized according to standard protocols. Based on the physical and chemical elements, Leça river achieved Good ecological status in P1, and Moderate in P4 to P7 (mainly due to nutrient enrichment) with P2 and P3 varying between Good and Moderate. The ecological status according to the macroinvertebrate community varied between: Good and Moderate in P1; Moderate and Poor in P2 and P3; Poor in P4 and P5; and Poor and Bad in P6 and P7. From the 1717 macrolitter items (belonging to 86 categories), artificial polymer/plastic items were the most frequent (56.67 %). More abundance and diversity of items were collected in sites P3 to P7, coinciding with the increasing anthropic presence. A multivariate analysis revealed that items originating from recreational activities were associated with fewer alterations in the macroinvertebrate community, while items originating from the deposition of domestic, industrial, and commercial residues were associated with more degraded conditions. The results suggest that the evaluation of macrolitter can be used to indicate anthropogenic activities that threaten aquatic ecosystems.

Effects of riverine nutrient enrichment and sediment reduction on high primary productivity zone in the Yangtze River estuary: historical reconstruction and future perspective

The high primary productivity zone (HPPZ) of estuaries is known for its flourishing fisheries and active interactions with coastal and oceanic ecosystems. However, the spatiotemporal patterns and underlying mechanisms that regulate the HPPZ remain unclear, especially in the face of drastic changes in riverine inputs. Using 40 years of in situ monitoring data along the Yangtze River estuary, the spatiotemporal evolution of the HPPZ regulated by basin-estuarine-offshore flux fluctuations has been reconstructed for the past and conclusions drawn for future developments. Moreover, the biological processes that influence the formation of the HPPZ were explored within the context of estuarine filtration and buffering effects. The obtained dataset includes chlorophyll a (Chl-a) concentrations and multiple environmental factors. The results displayed that the HPPZ is characterized by a high annual average Chl-a concentration of 3.6 ± 2.4 μg/L, which is driven by sufficient light and nutrient availability that promote phytoplankton blooms. In contrast, the inner high turbidity zone exhibits an average annual Chl-a concentration of 1.0 ± 0.7 μg/L, primarily due to limited light availability inhibiting phytoplankton growth. Meanwhile, the outer lower nutrient zone, with an average annual Chl-a concentration of 0.9 ± 1.1 μg/L, results from nutrient deficiencies that limit phytoplankton growth. Notably, the synergistic effect of sediment declines and eutrophication has resulted in a 6.5 μg/L increment of the HPPZ’s annual Chl-a concentration and a 3628 km² expansion of its area extent over 40 years. This significant change is attributed to the increase in water transparency resulting from a reduction in sediment transported from the watershed to the sea, along with an increase in riverine nitrogen and phosphorus discharge. A future projection, based on the historical total suspended matter and nutrients over the past 40 years, suggests that annual Chl-a concentration in the HPPZ will reach 10.5 μg/L, and the area is projected to increase to 7,904 km² by 2050. This study presents the first quantification of Chl-a concentrations and spatial range of the HPPZ in the estuary, focusing on the interaction between riverine and oceanic materials. These findings offer a deeper understanding of managing ecological risks in large estuaries.

Record-setting cyanobacterial bloom in the largest freshwater lake in northern China caused by joint effects of hydrological variations and nutrient enrichment.

Record-setting cyanobacterial bloom in the largest freshwater lake in northern China caused by joint effects of hydrological variations and nutrient enrichment.

Emerging environmental risks to the largest coastal lagoon (Pinqing Lagoon) on the Chinese mainland: Assessment through a water-sediment-ecological perspective.

Emerging environmental risks to the largest coastal lagoon (Pinqing Lagoon) on the Chinese mainland: Assessment through a water-sediment-ecological perspective.

Biodegradation of trimethoprim and sulfamethoxazole in secondary effluent by microalgae-bacteria consortium.

Biodegradation of trimethoprim and sulfamethoxazole in secondary effluent by microalgae-bacteria consortium.

Effect of nutrient enrichment and climate change on historical changes of the cyanobacterial community in a shallow north temperate lake in China

Effect of nutrient enrichment and climate change on historical changes of the cyanobacterial community in a shallow north temperate lake in China

Detritivore identity modulates effects of nutrient enrichment and a common fungicide presence on leaf litter decomposition and fungal community

Detritivore identity modulates effects of nutrient enrichment and a common fungicide presence on leaf litter decomposition and fungal community

Applications of inorganic nutrient enrichment in eucheumatoid seaweed farming: A double-edged sword?

Applications of inorganic nutrient enrichment in eucheumatoid seaweed farming: A double-edged sword?

Implications of coastal upwelling and mud banks on the structuring of phytoplankton communities in the nearshore waters of Alappuzha, southwest coast of India.

Implications of coastal upwelling and mud banks on the structuring of phytoplankton communities in the nearshore waters of Alappuzha, southwest coast of India.

Nutrient enrichment shapes litter micro-food webs in a subtropical plantation

Nutrient enrichment shapes litter micro-food webs in a subtropical plantation

Multiple Nutrient Additions Homogenize Multidimensional Plant Stoichiometry in a Meadow Steppe.

Human activities are altering terrestrial ecosystem biogeochemistry globally by augmenting the availability of multiple biologically essential nutrients, thereby potentially altering plant internal concentrations (i.e., stoichiometry) across a diverse array of elements. These shifts in plant nutrient concentrations may subsequently impact crucial ecosystem processes, including litter decomposition, herbivory by insects and large animals, and ecosystem productivity. However, most work on the alteration of plant stoichiometry has focused on a few macronutrients (e.g., nitrogen or phosphorus), despite the potential importance of many other elements. In this study, we conducted a comprehensive field experiment in the Inner Mongolia Steppe, manipulating eight distinct nutrients to examine their effects on both soil and plant tissue concentrations. Our findings reveal that adding most nutrients increased their corresponding available contents in the soil. In most cases, the addition of nutrients also increased their corresponding concentrations in plant tissues at both species and community levels. Besides, multiple nutrient additions had greater effects on soil available nutrient contents than on plant internal nutrient concentrations. Notably, the concurrent addition of multiple nutrients led to a significant homogenization of plant stoichiometry among different species within the same community. This homogenization might influence interspecific interactions and coexistence within grassland ecosystems. Our findings advanced our comprehension of how anthropogenic nutrient enrichment may simplify plant nutrient profiles, thereby influencing grassland biodiversity and ecosystem functionality.

Enhancing aerobic composting of cow dung and wheat straw with nanobubble water: Improved lignocellulose degradation and nutrient enrichment for increased crop biomass.

Enhancing aerobic composting of cow dung and wheat straw with nanobubble water: Improved lignocellulose degradation and nutrient enrichment for increased crop biomass.

Impacts of a prolonged marine heatwave and chronic local human disturbance on juvenile coral assemblages.

Coral reefs are threatened by climate change and chronic local human disturbances. Although some laboratory studies have investigated the effects of combined stressors, such as nutrient enrichment and heat stress, on growth and survival of early life stage corals, in situ studies remain limited. To assess the influence of multiple stressors on juvenile corals, we quantified densities of corals ≤ 5 cm at 18 forereef sites with different exposure levels to underlying chronic local human disturbance before, during, and after the 2015-2016 El Niño. This marine heatwave caused prolonged heat stress and devastating losses of coral cover on the shallow forereef's of Kiritimati, in the central equatorial Pacific Ocean. Here, we enumerated a total of 7732 juvenile corals from 13 different families. Over 80% of corals were from four families: 70% from Agariciidae, Merulinidae, or Poritidae, which all have stress-tolerant life history strategies, and 11% from Acroporidae which has a competitive life-history strategy. Both local disturbance and heat stress were significantly negatively related to juvenile coral densities. Prior to the heatwave, juvenile densities were on average 72% lower at the most disturbed sites (7.2 ± 1.9 m-2) compared to the least disturbed ones (15.3 ± 3.8 m-2). Overall, juvenile corals had a lower bleaching prevalence and lower mortality during the heatwave when compared to their adult counterparts. Still, the heatwave resulted in the loss of half (49%) of all juvenile corals, with those corals with competitive or weedy life history strategies undergoing greater declines than stress-tolerant ones. Although juvenile coral densities increased slightly in the year following the heatwave, the effect was statistically non-significant. Our results highlight the influence of chronic local anthropogenic and marine heatwaves on juvenile coral densities.

Revisiting lakes within the Rideau Canal system (Ontario, Canada) to assess the impacts of multiple environmental stressors over the past ~25 years using diatom-based paleolimnology

Diatom-based paleolimnological studies conducted ~25 years ago on five lakes (i.e., Big Rideau, Upper Rideau, Lower Rideau, Indian and Otter lakes) within the Rideau Canal system (Ontario, Canada) tracked extensive catchment disturbances related to canal construction (starting ca. 1828). Over the past three decades, these lakes have experienced additional environmental stressors including invasive zebra mussels and accelerated climate warming, warranting a paleolimnological re-assessment. We examine diatom compositional changes and visible range spectroscopy-inferred chlorophyll-a (VRS-Chla) trends over the past >200 years from sediment cores collected in 2019-2020 from these same lakes, with the aim of assessing environmental changes registered in these records since the original studies were undertaken ~25-30 years ago. Despite large-scale cultural disturbances, including extensive deforestation and flooding for canal construction, the most ecologically notable diatom changes in all sediment records occurred in the past ~25-30 years, and coincided with increases in VRS-Chla. During this recent period, small cyclotelloid and elongate planktonic diatoms increased in relative abundance, while large-celled Aulacoseira taxa declined. Exceptions to this trend include Upper Rideau Lake, where planktonic diatoms were scarce throughout the core and shifts occurred among benthic taxa, and Big Rideau Lake, which has a large littoral zone, where epiphytic diatoms became prominent in the past decade. These recent diatom changes could not be explained by nutrient enrichment, as measured total phosphorus (TP) concentrations have declined significantly since the 1970s. Increases in small planktonic taxa in some of the lakes also pre-date the ca. 1990 arrival of zebra mussels. We conclude that these recent changes were best explained by regional warming and declining wind speed resulting in new lake physical regimes. Such climate-driven changes are also consistent with the recent development of cyanobacterial blooms in these lakes, despite declining nutrient levels.

Effects of arsenic and trace metals on bacterial denitrification process from estuarine sediments and associated nitrous oxide emission.

Effects of arsenic and trace metals on bacterial denitrification process from estuarine sediments and associated nitrous oxide emission.

Enhancing tiny millets through genome editing: current status and future prospects.

This study aims to address the critical need for genetic improvement of small millets, which are vital yet underutilized cereal crops cultivated in semi-arid regions of Africa and Asia. Given their high nutritional value and climate resilience, small millets hold significant potential for food security and sustainable agriculture in arid regions. However, traditional breeding methods have proven to be time-consuming and inefficient in enhancing desirable traits. This study highlights the transformative potential of genome editing technologies, particularly the CRISPR/Cas9 system, in accelerating the development of improved small millet varieties. The findings presented in this paper detail recent advancements in using CRISPR/Cas for enhancing resistance to biotic stresses, including bacterial, viral, and fungal pathogens. Additionally, we explore how genome editing can be applied to improve abiotic stress tolerance, addressing challenges such as drought, cold, heat, and herbicides in small millets. We discuss the existing challenges faced by breeders, including issues related to ploidy levels, off-target effects, and limitations in organelle genome modification. The review also suggests potential strategies for overcoming these bottlenecks, aiming to develop stress-resistant super cultivars. Overall, this paper provides an overview of the current state of genome editing research in small millets while identifying future opportunities to enhance key traits for nutrient enrichment and climate resilience, ultimately paving the way for advancements in these crucial crops.

High nutrient requirement on the photosynthetic performance of a diatom species of the genus Nitzschia (Bacillariophyta) isolated from the high‐altitude wetland, Salar de Huasco, Chile

SUMMARYThis study characterizes the ecophysiological responses and growth dynamics of Nitzschia palea isolated from Salar de Huasco, Chile, a high‐altitude wetland located at 3800 m above sea level. The culture was maintained at 17°C under cool‐white fluorescent light with a 14:10 h light/dark photocycle and a photon flux of 50 μmol photons m−2 s−1. The diatom was identified morphologically and genetically, with phylogenetic analysis confirming its close relationship to known N. palea strains. Photophysiological responses were measured along with a series of media and temperature conditions in N. palea strain. Modified f/2 media supplemented with different concentrations of Si, Se and vitamins were tested. Subsequently, growth in the double‐Si f/2 media was assessed at three different temperatures. Lastly, the diatom strain was incubated at 17°C and 27–29°C in f/2 + double‐Si (NN: non‐extra nutrient addition) and a highly eutrophic state of f/2 (WN: with nutrient enrichment addition). The highest growth was observed using the f/2 media WN at 17°C (day 5, 4.46 × 105 ± 3.15 × 104 SD cells mL−1). Temperature significantly influenced growth; 17°C supported higher cell densities and more stable photosynthetic parameters compared 27–29°C. Nutrient enrichment further enhanced photosynthetic efficiency (αETR) and maximal quantum yield (Fv/Fm), particularly under control temperature conditions. Photosynthetic performance, assessed via rapid light‐response curves, showed significant temperature and nutrient dependent variation. Nitzschia palea cultures at 27–29°C exhibited increased in relative maximal ETR (rETRmax,184.1 μmol m−2 s−1) compared to control conditions. In nutrient enriched treatments, photosynthetic efficiency peaked on day 5, but declined by day 8. These findings highlight the adaptive capacity of N. palea to fluctuating environmental conditions and underscore its potential as a model organism for studying diatom responses to nutrient and temperature stress in extreme ecosystems.