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Climate change, especially in the form of precipitation and temperature changes, can alter the transformation and delivery of nitrogen on the land surface and to aquatic systems, impacting the trophic states of downstream water bodies. While the expected impacts of changes in precipitation have been explored, a quantitative understanding of the impact of temperature on nitrogen loading is lacking at landscape scales. Here, using several decades of nitrogen loading observations, we quantify how individual and combined future changes in precipitation and temperature will affect riverine nitrogen loading. We find that, contrary to recent decades, rising temperatures are likely to offset or even reverse previously reported impacts of future increases in total and extreme precipitation on nitrogen runoff across the majority of the contiguous United States. These findings highlight the multifaceted impacts of climate change on the global nitrogen cycle.
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Species invasions are predicted to increase in frequency with global change, but quantitative predictions of how environmental filters and species traits influence the success and consequences of invasions for local communities are lacking. Here we investigate how invaders alter the structure, diversity and stability regime of simple communities across environmental gradients (habitat productivity, temperature) and community size structure. We simulate all three-species trophic modules (apparent and exploitative competition, trophic chain and intraguild predation). We predict that invasions most often succeed in warm and productive habitats and that successful invaders include smaller competitors, intraguild predators and comparatively small top predators. This suggests that species invasions and global change may facilitate the downsizing of food webs. Furthermore, we show that successful invasions leading to species substitutions rarely alter system stability, while invasions leading to increased diversity can destabilize or stabilize community dynamics depending on the environmental conditions and invader's trophic position.
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Ecosistema , Cadena Alimentaria , Animales , Temperatura , Tamaño Corporal , Conducta PredatoriaRESUMEN
MAIN CONCLUSION: The combined photoinhibitory and PSII-reaction centre quenching against light stress is an important mechanism that allows the green macroalga Ulva rigida to proliferate and form green tides in coastal ecosystems. Eutrophication of coastal ecosystems often stimulates massive and uncontrolled growth of green macroalgae, causing serious ecological problems. These green tides are frequently exposed to light intensities that can reduce their growth via the production of reactive oxygen species (ROS). To understand the physiological and biochemical mechanisms leading to the formation and maintenance of green tides, the interaction between inorganic nitrogen (Ni) and light was studied. In a bi-factorial physiological experiment simulating eutrophication under different light levels, the bloom-forming green macroalga Ulva rigida was exposed to a combination of ecologically relevant nitrate concentrations (3.8-44.7 µM) and light intensities (50-1100 µmol photons m-2 s-1) over three days. Although artificial eutrophication (≥ 21.7 µM) stimulated nitrate reductase activity, which regulated both nitrate uptake and vacuolar storage by a feedback mechanism, nitrogen assimilation remained constant. Growth was solely controlled by the light intensity because U. rigida was Ni-replete under oligotrophic conditions (3.8 µM), which requires an effective photoprotective mechanism. Fast declining Fv/Fm and non-photochemical quenching (NPQ) under excess light indicate that the combined photoinhibitory and PSII-reaction centre quenching avoided ROS production effectively. Thus, these mechanisms seem to be key to maintaining high photosynthetic activities and growth rates without producing ROS. Nevertheless, these photoprotective mechanisms allowed U. rigida to thrive under the contrasting experimental conditions with high daily growth rates (12-20%). This study helps understand the physiological mechanisms facilitating the formation and persistence of ecologically problematic green tides in coastal areas.
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Chlorophyta , Algas Comestibles , Algas Marinas , Ulva , Ecosistema , Nitratos , Especies Reactivas de Oxígeno , NitrógenoRESUMEN
External nutrient loading can cause large changes in freshwater ecosystems. Many local field and laboratory experiments have investigated ecological responses to nutrient addition. However, these findings are difficult to generalize, as the responses observed may depend on the local context and the resulting nutrient concentrations in the receiving water bodies. In this research, we combined and analysed data from 131 experimental studies containing 3054 treatment-control abundance ratios to assess the responses of freshwater taxa along a gradient of elevated nutrient concentrations. We carried out a systematic literature search in order to identify studies that report the abundance of invertebrate, macrophyte, and fish taxa in relation to the addition of nitrogen, phosphorus, or both. Next, we established mixed-effect meta-regression models to relate the biotic responses to the concentration gradients of both nutrients. We quantified the responses based on various abundance-based metrics. We found no responses to the mere addition of nutrients, apart from an overall increase of total invertebrate abundance. However, when we considered the gradients of N and P enrichment, we found responses to both nutrients for all abundance metrics. Abundance tended to increase at low levels of N enrichment, yet decreased at the high end of the concentration gradient (1-10 mg/L, depending on the P concentration). Responses to increasing P concentrations were mostly positive. For fish, we found too few data to perform a meaningful analysis. The results of our research highlight the need to consider the level of nutrient enrichment rather than the mere addition of nutrients in order to better understand broad-scale responses of freshwater biota to eutrophication, as a key step to identify effective conservation strategies for freshwater ecosystems.
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Ecosistema , Invertebrados , Animales , Agua Dulce , Biota , Peces , Nutrientes/análisis , Fósforo/análisis , Nitrógeno/análisis , EutrofizaciónRESUMEN
Blooms of microalgal red tides and macroalgae (e.g., green and golden tides caused by Ulva and Sargassum) have caused widespread problems around China in recent years, but there is uncertainty around what triggers these blooms and how they interact. Here, we use 30 years of monitoring data to help answer these questions, focusing on the four main species of microalgae Prorocentrum donghaiense, Karenia mikimotoi, Noctiluca scintillans, and Skeletonema costatum) associated with red tides in the region. The frequency of red tides increased from 1991 to 2003 and then decreased until 2020, with S. costatum red tides exhibiting the highest rate of decrease. Green tides started to occur around China in 1999 and the frequency of green tides has since been on the increase. Golden tides were first reported to occur around China in 2012. The frequency of macroalgal blooms has a negative linear relationship with the frequency and coverage of red tides around China, and a positive correlation with total nitrogen and phosphorus loads as well as with atmospheric CO2 and sea surface temperature (SST). Increased outbreaks of macroalgal blooms are very likely due to worsening levels of eutrophication, combined with rising CO2 and SST, which contribute to the reduced frequency of red tides. The increasing grazing rate of microzooplankton also results in the decline in areas affected by red tides. This study shows a clear shift of algal blooms from microalgae to macroalgae around China over the past 30 years driven by the combination of eutrophication, climate change, and grazing stress, indicating a fundamental change in coastal systems in the region.
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Dinoflagelados , Microalgas , Algas Marinas , Cambio Climático , Dióxido de Carbono , Eutrofización , ChinaRESUMEN
Warming and eutrophication influence carbon (C) processing in sediments, with implications for the global greenhouse-gas budget. Temperature effects on sedimentary C loss are well understood, but the mechanism of change in turnover through priming with labile organic matter (OM) is not. Evaluating changes in the magnitude of priming as a function of warming, eutrophication, and OM stoichiometry, we incubated sediments with 13 C-labeled fresh organic matter (FOM, algal/cyanobacterial) and simulated future climate scenarios (+4°C and +8°C). We investigated FOM-induced production of CH4 and microbial community changes. C loss was primed by up to 17% in dominantly allochthonous sediments (ranging from 5% to 17%), compared to up to 6% in autochthonous sediments (-9% to 6%), suggesting that refractory OM is more susceptible to priming. The magnitude of priming was dependent on sediment OM stoichiometry (C/N ratio), the ratio of fresh labile OM to microbial biomass (FOM/MB), and temperature. Priming was strongest at 4°C when FOM/MB was below 50%. Addition of FOM was associated with activation and growth of bacterial decomposers, including for example, Firmicutes, Bacteroidetes, or Fibrobacteres, known for their potential to degrade insoluble and complex structural biopolymers. Using sedimentary C/N > 15 as a threshold, we show that in up to 35% of global lakes, sedimentation is dominated by allochthonous rather than autochthonous material. We then provide first-order estimates showing that, upon increase in phytoplankton biomass in these lakes, priming-enabled degradation of recalcitrant OM will release up to 2.1 Tg C annually, which would otherwise be buried for geological times.
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Cianobacterias , Lagos , Lagos/química , Biomasa , Carbono/química , Fitoplancton , Sedimentos Geológicos/química , Eutrofización , ChinaRESUMEN
Nitrogen (N) is a limiting nutrient for primary productivity in most terrestrial ecosystems, but whether N limitation is strengthening or weakening remains controversial because both N sources and sinks are increasing in magnitude globally. Temperate marshes are exposed to greater amounts of external N inputs than most terrestrial ecosystems and more than in preindustrial times owing to their position downstream of major sources of human-derived N runoff along river mouths and estuaries. Simultaneously, ecosystem N demand may also be increasing owing to other global changes such as rising atmospheric [CO2]. Here, we used interannual variability in external drivers and variables related to exogenous supply of N, along with detailed assessments of plant growth and porewater biogeochemistry, to assess the severity of N-limitation, and to determine its causes, in a 14-year N-addition × elevated CO2 experiment. We found substantial interannual variability in porewater [N], plant growth, and experimental N effects on plant growth, but the magnitude of N pools through time varied independently of the strength of N limitation. Sea level, and secondarily salinity, related closely to interannual variability in growth of the dominant plant functional groups which drove patterns in N limitation and in porewater [N]. Experimental exposure of plants to elevated CO2 and years with high flooding strengthened N limitation for the sedge. Abiotic variables controlled plant growth, which determined the strength of N limitation for each plant species and for ecosystem productivity as a whole. We conclude that in this ecosystem, which has an open N cycle and where N inputs are likely greater than in preindustrial times, plant N demand has increased more than supply.
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Dióxido de Carbono , Nitrógeno , Humedales , Nitrógeno/metabolismo , Nitrógeno/análisis , Dióxido de Carbono/metabolismo , Dióxido de Carbono/análisis , Desarrollo de la Planta , Plantas/metabolismo , SalinidadRESUMEN
Due to various human activities, including intensive agriculture, traffic, and the burning of fossil fuels, in many parts of the world, current levels of reactive nitrogen emissions strongly exceed pre-industrial levels. Previous studies have shown that the atmospheric deposition of these excess nitrogen compounds onto semi-natural terrestrial environments has negative consequences for plant diversity. However, these previous studies mostly investigated biodiversity loss at local spatial scales, that is, at the scales of plots of typically a few square meters. Whether increased atmospheric nitrogen deposition also affects plant diversity at larger spatial scales remains unknown. Here, using grassland plant community data collected in 765 plots, across 153 different sites and 9 countries in northwestern Europe, we investigate whether relationships between atmospheric nitrogen deposition and plant biodiversity are scale-dependent. We found that high levels of atmospheric nitrogen deposition were associated with low levels of plant species richness at the plot scale but also at the scale of sites and regions. The presence of 39% of plant species was negatively associated with increasing levels of nitrogen deposition at large (site) scales, while only 1.5% of the species became more common with increasing nitrogen deposition, indicating that large-scale biodiversity changes were mostly driven by "loser" species, while "winner" species profiting from high N deposition were rare. Some of the "loser" species whose site presence was negatively associated with atmospheric nitrogen deposition are listed as "threatened" in at least some EU member states, suggesting that nitrogen deposition may be a key contributor to their threat status. Hence, reductions in reactive nitrogen emissions will likely benefit plant diversity not only at local but also at larger spatial scales.
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Atmósfera , Biodiversidad , Nitrógeno , Plantas , Nitrógeno/análisis , Nitrógeno/metabolismo , Plantas/metabolismo , Europa (Continente) , Atmósfera/química , PraderaRESUMEN
Streams are significant contributors of greenhouse gases (GHG) to the atmosphere, and the increasing number of stressors degrading freshwaters may exacerbate this process, posing a threat to climatic stability. However, it is unclear whether the influence of multiple stressors on GHG concentrations in streams results from increases of in-situ metabolism (i.e., local processes) or from changes in upstream and terrestrial GHG production (i.e., distal processes). Here, we hypothesize that the mechanisms controlling multiple stressor effects vary between carbon dioxide (CO2) and methane (CH4), with the latter being more influenced by changes in local stream metabolism, and the former mainly responding to distal processes. To test this hypothesis, we measured stream metabolism and the concentrations of CO2 (pCO2) and CH4 (pCH4) in 50 stream sites that encompass gradients of nutrient enrichment, oxygen depletion, thermal stress, riparian degradation and discharge. Our results indicate that these stressors had additive effects on stream metabolism and GHG concentrations, with stressor interactions explaining limited variance. Nutrient enrichment was associated with higher stream heterotrophy and pCO2, whereas pCH4 increased with oxygen depletion and water temperature. Discharge was positively linked to primary production, respiration and heterotrophy but correlated negatively with pCO2. Our models indicate that CO2-equivalent concentrations can more than double in streams that experience high nutrient enrichment and oxygen depletion, compared to those with oligotrophic and oxic conditions. Structural equation models revealed that the effects of nutrient enrichment and discharge on pCO2 were related to distal processes rather than local metabolism. In contrast, pCH4 responses to nutrient enrichment, discharge and temperature were related to both local metabolism and distal processes. Collectively, our study illustrates potential climatic feedbacks resulting from freshwater degradation and provides insight into the processes mediating stressor impacts on the production of GHG in streams.
Os rios são grandes emissores de gases com efeito de estufa (GEE) para a atmosfera, e o crescente número de agentes de stress que degradam os rios pode exacerbar este processo, e constituir uma ameaça à estabilidade climática. No entanto, não é claro se o efeito dos impactos humanos nas concentrações de GEE na água está associado ao aumento do metabolismo local do rio (processos locais) ou ao aumento da produção de GEE nas zonas a montante dos rios ou nas zonas terrestres adjacentes (processos distais). A nossa hipótese é que os mecanismos que controlam os efeitos dos impactos humanos na emissão de GEE variam entre o dióxido de carbono (CO2) e o metano (CH4). A nossa previsão é que o CO2 responde principalmente a processos distais, enquanto o CH4 é mais influenciado por alterações no metabolismo local dos cursos de água. Para avaliar esta hipótese, medimos o metabolismo aquático e as concentrações de CO2 (pCO2) e CH4 (pCH4) em 50 rios que abrangem gradientes de enriquecimento em nutrientes, depleção de oxigénio, stress térmico, degradação da zona ribeirinha e caudal. Os nossos resultados indicam que estes agentes de stress tiveram efeitos aditivos no metabolismo e nas concentrações de GEE nos rios, e que as interações entre os agentes de stress tiveram pouca capacidade preditiva. O enriquecimento em nutrientes foi associado a um aumento da heterotrofia e pCO2, enquanto o pCH4 aumentou com a depleção de oxigénio e com a temperatura da água. O caudal estava positivamente correlacionado com a produção primária, a respiração e a heterotrofia, mas negativamente correlacionado com o pCO2. Os nossos modelos indicam que as concentrações equivalentes de CO2 podem duplicar em rios eutrofizados e com baixa concentração de oxigénio, em comparação com os rios oligotróficos e com águas bem oxigenadas. A aplicação de modelos de equações estruturais mostrou que os efeitos do enriquecimento em nutrientes e do caudal no pCO2 estavam relacionados com processos distais e não com o metabolismo local. Em contrapartida, as respostas do pCH4 ao enriquecimento de nutrientes, ao caudal e à temperatura estavam relacionadas tanto com o metabolismo local como com processos distais. O nosso estudo demonstra que a degradação dos rios e dos ecossistemas ribeirinhos pode ter efeitos negativos na estabilidade climática e fornece informação relevante sobre os processos biogeoquímicos que medeiam os impactos humanos na produção de GEE nos rios.
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Dióxido de Carbono , Gases de Efecto Invernadero , Metano , Ríos , Gases de Efecto Invernadero/análisis , Ríos/química , Dióxido de Carbono/análisis , Dióxido de Carbono/metabolismo , Metano/análisis , Metano/metabolismo , Cambio Climático , Temperatura , Oxígeno/análisis , Oxígeno/metabolismoRESUMEN
In this experiment, the eutrophication system was established by adding sucrose and yeast powder, and the pH and dissolved oxygen were measured in a bioreactor in real time to study the effect of aerobic environment on the fermentation process of Polygonati Rhizoma extract by Lactiplantibacillus plantarum. To further analyze metabolic changes, UPLC-Q-Exactive MS was used for metabolomic analysis and metabolic profiling. Multivariate analysis was performed using principal component analysis and Orthogonal projections to latent structures discriminant analysis. Finally, 313 differential metabolites were selected, 196 of which were annotated through database matching. After fermentation, the content of short-chain fatty acids, lactic acid, and their derivatives increased significantly, and there were 13 kinds and 4 kinds, respectively. Both compounds and their derivatives are beneficial to the intestinal flora. Consequently, incorporating L. plantarum into the aerobic fermentation process of Polygonati Rhizoma extract within the eutrophic system is potentially advantageous in enhancing the impact of its fermentation solution on the gut microbiota and its effects on human health. Our findings for this kind of edible and medicinal material research and development offer useful insights.
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Fermentación , Lactobacillus plantarum , Polygonatum , Rizoma , Polygonatum/química , Polygonatum/metabolismo , Rizoma/química , Lactobacillus plantarum/metabolismo , Eutrofización , Extractos Vegetales/metabolismo , Extractos Vegetales/química , Ácido Láctico/metabolismo , Ácidos Grasos Volátiles/metabolismo , Reactores Biológicos/microbiología , Microbioma Gastrointestinal , MetabolómicaRESUMEN
BACKGROUND AND AIMS: Maerl-associated communities have received considerable attention due to their uniqueness, biodiversity and functional importance. Although the impacts of human activities are well documented for maerl-associated macrofauna, the spatio-temporal variations of macroalgae have comparatively been neglected, and the drivers that influence their dynamics are poorly known. We investigate the links between maerl-associated macroalgal communities, anthropogenic pressures and environmental conditions, and hypothesize that sites under human pressure would exhibit different dynamics when compared to reference sites. METHODS: To better understand community variation through space and time, four subtidal maerl beds under different pressures were consistently monitored over one year in the bay of Brest, Brittany, France. Both macroalgae community monitoring and environmental data were acquired through field sampling and available models. KEY RESULTS: Higher macroalgal biomass was observed within eutrophic sites, especially in summer (more than ten times higher than in the Unimpacted site), caused by free-living forms of opportunistic red macroalgae. The Dredged site also exhibited distinct macroalgal communities during summer from the Unimpacted site. Nutrient concentrations and seasonality proved to be key factors affecting the macroalgal community composition, although dredging and its effects on granulometry also had a strong influence. Over the long term, fewer than half of the species identified during historical surveys were found, indicating major temporal changes. CONCLUSIONS: Human pressures have strong impacts on maerl-associated macroalgal communities. Nutrient concentrations and dredging pressure appear as the main anthropogenic factors shaping maerl-associated macroalgal communities. Additionally, our results suggest historical changes in maerl-associated macroalgal communities over 25 years in response to changes in local human pressure management. This study suggests that maerl-associated macroalgal communities could be used as indicators of anthropogenically driven changes in this habitat.
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Algas Marinas , Algas Marinas/fisiología , Francia , Humanos , Ecosistema , Estaciones del Año , Biodiversidad , Efectos Antropogénicos , Biomasa , Dinámica Poblacional , Eutrofización , Actividades HumanasRESUMEN
BACKGROUND AND AIMS: Freshwater nitrogen inputs are increasing globally, altering the structure and function of wetland ecosystems adapted to low nutrient conditions. Carnivorous wetland plants, Utricularia spp., are hypothesised to reduce their reliance on carnivory and increase their assimilation of environmental nutrients when the supply of ambient nutrients increases. Despite success in using stable isotope approaches to quantify carnivory of terrestrial carnivorous plants, quantifying carnivory of aquatic Utricularia requires improvement. METHODS: We developed stable isotope mixing models to quantify aquatic plant carnivory and used these models to measure dietary changes of three Utricularia species: Utricularia australis, U. gibba, and U. uliginosa in 11 wetlands across a 794 km gradient in eastern Australia. Diet was assessed using multiple models that compared variations in the natural abundance nitrogen isotope composition (δ15N) of Utricularia spp. with that of non-carnivorous plants, and environmental and carnivorous nitrogen sources. KEY RESULTS: Carnivory supplied 40 - 100 % of plant nitrogen. The lowest carnivory rates coincided with the highest availability of ammonium and dissolved organic carbon. CONCLUSIONS: Our findings suggest that Utricularia populations may adapt to high nutrient environments by shifting away from energetically costly carnivory. This has implications for species conservation as anthropogenic impacts continue to affect global wetland ecosystems.
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Eutrophication and brownification are ongoing environmental problems affecting aquatic ecosystems. Due to anthropogenic changes, increasing amounts of organic and inorganic compounds are entering aquatic systems from surrounding catchment areas, increasing both nutrients, total organic carbon (TOC), and water color with societal, as well as ecological consequences. Several studies have focused on the ability of wetlands to reduce nutrients, whereas data on their potential to reduce TOC and water color are scarce. Here we evaluate wetlands as a potential multifunctional tool for mitigating both eutrophication and brownification. Therefore, we performed a study for 18 months in nine wetlands allowing us to estimate the reduction in concentrations of total nitrogen (TN), total phosphorus (TP), TOC and water color. We show that wetland reduction efficiency with respect to these variables was generally higher during summer, but many of the wetlands were also efficient during winter. We also show that some, but not all, wetlands have the potential to reduce TOC, water color and nutrients simultaneously. However, the generalist wetlands that reduced all four parameters were less efficient in reducing each of them than the specialist wetlands that only reduced one or two parameters. In a broader context, generalist wetlands have the potential to function as multifunctional tools to mitigate both eutrophication and brownification of aquatic systems. However, further research is needed to assess the design of the generalist wetlands and to investigate the potential of using several specialist wetlands in the same catchment.
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Ecosistema , Humedales , Eutrofización , Nitrógeno , AguaRESUMEN
Lake Victoria is well known for its high diversity of endemic fish species and provides livelihoods for millions of people. The lake garnered widespread attention during the twentieth century as major environmental and ecological changes modified the fish community with the extinction of approximately 40% of endemic cichlid species by the 1980s. Suggested causal factors include anthropogenic eutrophication, fishing, and introduced non-native species but their relative importance remains unresolved, partly because monitoring data started in the 1970s when changes were already underway. Here, for the first time, we reconstruct two time series, covering the last approximately 200 years, of fish assemblage using fish teeth preserved in lake sediments. Two sediment cores from the Mwanza Gulf of Lake Victoria, were subsampled continuously at an intra-decadal resolution, and teeth were identified to major taxa: Cyprinoidea, Haplochromini, Mochokidae and Oreochromini. None of the fossils could be confidently assigned to non-native Nile perch. Our data show significant decreases in haplochromine and oreochromine cichlid fish abundances that began long before the arrival of Nile perch. Cyprinoids, on the other hand, have generally been increasing. Our study is the first to reconstruct a time series of any fish assemblage in Lake Victoria extending deeper back in time than the past 50 years, helping shed light on the processes underlying Lake Victoria's biodiversity loss.
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Cíclidos , Lagos , Animales , Humanos , Factores de Tiempo , Tanzanía , Biodiversidad , Especies IntroducidasRESUMEN
Coastal zones account for 75% of marine methane emissions, despite covering only 15% of the ocean surface area. In these ecosystems, the tight balance between methane production and oxidation in sediments prevents most methane from escaping into seawater. However, anthropogenic activities could disrupt this balance, leading to an increased methane escape from coastal sediments. To quantify and unravel potential mechanisms underlying this disruption, we used a suite of biogeochemical and microbiological analyses to investigate the impact of anthropogenically induced redox shifts on methane cycling in sediments from three sites with contrasting bottom water redox conditions (oxic-hypoxic-euxinic) in the eutrophic Stockholm Archipelago. Our results indicate that the methane production potential increased under hypoxia and euxinia, while anaerobic oxidation of methane was disrupted under euxinia. Experimental, genomic, and biogeochemical data suggest that the virtual disappearance of methane-oxidizing archaea at the euxinic site occurred due to sulfide toxicity. This could explain a near 7-fold increase in the extent of escape of benthic methane at the euxinic site relative to the hypoxic one. In conclusion, these insights reveal how the development of euxinia could disrupt the coastal methane biofilter, potentially leading to increased methane emissions from coastal zones.
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Sedimentos Geológicos , Metano , Oxidación-Reducción , Sulfuros , Metano/metabolismo , Sedimentos Geológicos/química , Anaerobiosis , Agua de Mar/química , Eutrofización , Archaea/metabolismoRESUMEN
Validating paleo total phosphorus (TP) inference methods over long time scales is essential for understanding historic changes in lake P supply and the processes leading up to the present-day global lake eutrophication crisis. Monitored lake water TP time series have enabled us to identify the drivers of eutrophication over recent decades. However, over longer time scales, the lack of reliable TP inference means our understanding of drivers is speculative. Validation of lake water TP reconstruction, therefore, remains the "ultimate aim" of eutrophication studies. Here, we present the first critical comparison of two fully independent paleo TP inference approaches: the well-established diatom method (DI-TP) and a recently developed sediment geochemical method (SI-TP). Using lake sediment records from a small eutrophic U.K. lake (Crose Mere), we find a statistically significant agreement between the two inferred TP records with greater than 60% shared variance. Both records show identical timings, with a 19th century acceleration in TP concentration and subsequent declines following a peak in 1930. This significant agreement establishes the validity of long-term paleo TP inference for the first time. With this, we can now test assumptions and paradigms that underpin understanding of catchment P sources and pathways over longer time scales.
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Monitoreo del Ambiente , Eutrofización , Sedimentos Geológicos , Lagos , Fósforo , Fósforo/análisis , Lagos/química , Sedimentos Geológicos/química , Monitoreo del Ambiente/métodos , Diatomeas , Contaminantes Químicos del Agua/análisisRESUMEN
Long-term phosphorus (P) fertilization results in P accumulation in agricultural soil and increases the risk of P leaching into water bodies. However, evaluating P leaching into groundwater is challenging, especially in clay soil with a high P sorption capacity. This study examined whether the combination of PO4 oxygen isotope (δ18OPO4) analysis and the P saturation ratio (PSR) was useful to identify P enrichment mechanisms in groundwater. We investigated the groundwater and possible P sources in Kubi, western Japan, with intensive citrus cultivation. Shallow groundwater had oxic conditions with high PO4 concentrations, and orchard soil P accumulation was high compared with forest soil. Although the soil had a high P sorption capacity, the PSR was above the threshold, indicating a high risk of P leaching from the surface orchard soil. The shallow groundwater δ18OPO4 values were higher than the expected isotopic equilibrium with pyrophosphatase. The high PSR and δ18OPO4 orchard soil values indicated that P leaching from orchard soil was the major P enrichment mechanism. The Bayesian mixing model estimated that 76.6% of the P supplied from the orchard soil was recycled by microorganisms. This demonstrates the utility of δ18OPO4 and the PSR to evaluate the P source and biological recycling in groundwater.
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Agua Subterránea , Fósforo , Fósforo/análisis , Fosfatos , Suelo , Isótopos de Oxígeno/análisis , Adsorción , Teorema de BayesRESUMEN
Data from the International Stormwater Best Management Practices (BMP) Database were used to compare the phosphorus (P) control performance of six categories of stormwater BMPs representing traditional systems (stormwater pond, wetland basin, and detention basin) and low-impact development (LID) systems (bioretention cell, grass swale, and grass strip). Machine learning (ML) models were trained to predict the reduction or enrichment factors of surface runoff concentrations and loadings of total P (TP) and soluble reactive P (SRP) for the different categories of BMP systems. Relative to traditional BMPs, LIDs generally enriched TP and SRP concentrations in stormwater surface outflow and yielded poorer P runoff load control. The SRP concentration reduction and enrichment factors of LIDs also tended to be more sensitive to variations in climate and watershed characteristics. That is, LIDs were more likely to enrich surface runoff SRP concentrations in drier climates, when inflow SRP concentrations were low, and for watersheds exhibiting high impervious land cover. Overall, our results imply that stormwater BMPs do not universally attenuate urban P export and that preferentially implementing LIDs over traditional BMPs may increase TP and SRP export to receiving freshwater bodies, hence magnifying eutrophication risks.
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Fósforo , Contaminantes Químicos del Agua , LluviaRESUMEN
There is a longstanding debate about the role of nitrogen (N) vs phosphorus (P) in limiting primary production in lakes and whether co-nutrient limitation should be considered for managing eutrophication. We evaluated nutrient limitation and eutrophication at a subcontinental scale. Using U.S. Environmental Protection Agency National Lakes Assessment data, we assessed broad-scale patterns in nutrient limitation and compared samples of all surveyed lakes and lakes resurveyed in multiple surveys. We found that N correlated more strongly with productivity in the western U.S., while P correlated more strongly in the eastern U.S. The aggregated subcontinental effect suggests the importance of factors like N-deposition, terrestrial vegetation, underlying geology, and land use for understanding drivers of nutrient dynamics in lakes. Our study showed how patterns can aggregate across subcontinental scales yet still demonstrate considerable variation when more deeply examined on an individual lake level. Overall, we found that nutrient limitation is dynamic over space and time, with most lakes being co-limited. The prevalence of co-limitation also increased from 2007 to 2017. Trophic states within each limitation category varied substantially. Our findings underscore the need for combined N and P reductions to mitigate accelerated eutrophication.
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Eutrofización , Lagos , Nitrógeno , Nutrientes , Fósforo , Estados Unidos , Monitoreo del AmbienteRESUMEN
Excessive anthropogenic phosphorus (P) emissions put constant pressure on aquatic ecosystems. This pressure can be quantified as the freshwater eutrophication potential (FEP) by linking P emissions, P fate in environmental compartments, and the potentially disappeared fraction of species due to increase of P concentrations in freshwater. However, previous fate modeling on global and regional scales is mainly based on the eight-direction algorithm without distinguishing pollution sources. The algorithm fails to characterize the fate paths of point-source emissions via subsurface pipelines and wastewater treatment infrastructure, and exhibits suboptimal performance in accounting for multidirectional paths caused by river bifurcations, especially in flat terrains. Here we aim to improve the fate modeling by incorporating various fate paths and addressing multidirectional scenarios. We also update the P estimates by complementing potential untreated point-source emissions (PSu). The improved method is examined in a rapidly urbanizing area in Taihu Lake Basin, China in 2017 at a spatial resolution of 100 m × 100 m. Results show that the contribution of PSu on FEP (62.6%) is greater than that on P emissions (58.5%). The FEP is more spatially widely distributed with the improved fate modeling, facilitating targeted regulatory strategies tailored to local conditions.