Engineered Nanoparticles Interact with Nutrients to Intensify Eutrophication in a Wetland Ecosystem Experiment

Despite the rapid rise in diversity and quantities of engineered nanomaterials produced, the impacts of these emerging contaminants on the structure and function of ecosystems have received little attention from ecologists. Moreover, little is known about how manufactured nanomaterials may interact with nutrient pollution in altering ecosystem productivity, despite the recognition that eutrophication is the primary water quality issue in freshwater ecosystems worldwide. In this study, we asked two main questions: (1) To what extent do manufactured nanoparticles affect the biomass and productivity of primary producers in wetland ecosystems? (2) How are these impacts mediated by nutrient pollution? To address these questions, we examined the impacts of a citrate‐coated gold nanoparticle (AuNPs) and of a commercial pesticide containing Cu(OH)2 nanoparticles (CuNPs) on aquatic primary producers under both ambient and enriched nutrient conditions. Wetland mesocosms were exposed repeatedly with low concentrations of nanoparticles and nutrients over the course of a 9‐month experiment in an effort to replicate realistic field exposure scenarios. In the absence of nutrient enrichment, there were no persistent effects of AuNPs or CuNPs on primary producers or ecosystem productivity. However, when combined with nutrient enrichment, both NPs intensified eutrophication. When either of these NPs were added in combination with nutrients, algal blooms persisted for \u3e 50 d longer than in the nutrient‐only treatment. In the AuNP treatment, this shift from clear waters to turbid waters led to large declines in both macrophyte growth and rates of ecosystem gross primary productivity (average reduction of 52% ± 6% and 92% ± 5%, respectively) during the summer. Our results suggest that nutrient status greatly influences the ecosystem‐scale impact of two emerging contaminants and that synthetic chemicals may be playing an under‐appreciated role in the global trends of increasing eutrophication. We provide evidence here that chronic exposure to Au and Cu(OH)2 nanoparticles at low concentrations can intensify eutrophication of wetlands and promote the occurrence of algal blooms

Dual controls on carbon loss during drought in peatlands

Peatlands store one-third of global soil carbon(1). Drought/drainage coupled with climate warming present the main threat to these stores(1-4). Hence, understanding drought effects and inherent feedbacks related to peat decomposition has been a primary global challenge(5,6). However, widely divergent results concerning drought in recent studies(3,7-11) challenge the accepted paradigm that waterlogging and associated anoxia are the overarching controls locking up carbon stored in peat. Here, by linking field and microcosm experiments, we show how previously unrecognized mechanisms regulate the build-up of phenolics, which protects stored carbon directly by reducing phenol oxidase activity during short-term drought and, indirectly, through a shift from low-phenolic Sphagnum/herbs to high-phenolic shrubs after long-term moderate drought. We demonstrate that shrub expansion induced by drought/warming(2,6,10,12,13) in boreal peatlands might be a long-term self-adaptive mechanism not only increasing carbon sequestration but also potentially protecting historic soil carbon. We therefore propose that the projected 'positive feedback loop' between carbon emission and drought in peatlands(2,3,14,15) may not occur in the long term

Appendix B. Tables and a figure showing (1) summary statistics for the partial redundancy analysis, (2) results from the ANOSIM test, and (3) regression results.

Tables and a figure showing (1) summary statistics for the partial redundancy analysis, (2) results from the ANOSIM test, and (3) regression results

Appendix A. Tables showing supplemental data including (1) watershed characteristics, (2) temperature and hydrology treatments, (3) plant species, and (4) chemical and physical properties of the study sites.

Tables showing supplemental data including (1) watershed characteristics, (2) temperature and hydrology treatments, (3) plant species, and (4) chemical and physical properties of the study sites

Stress Responses of Aquatic Plants to Silver Nanoparticles

Silver nanoparticles (AgNPs) are increasingly used in consumer products, biotechnology, and medicine, and are released into aquatic ecosystems through wastewater discharge. This study investigated the phytotoxicity of AgNPs to aquatic plants, <i>Egeria densa</i> and <i>Juncus effusus</i> by measuring physiologic and enzymatic responses to AgNP exposure under three release scenarios: two chronic (8.7 mg, weekly) exposures to either zerovalent AgNPs or sulfidized silver nanoparticles; and a pulsed (450 mg, one-time) exposure to zerovalent AgNPs. Plant enzymatic and biochemical stress responses were assessed using superoxide dismutase (SOD) and peroxidase (POD) activity, malondialdehyde (MDA) concentrations and chlorophyll content as markers of defense and phytotoxicity, respectively. The high initial pulse treatment resulted in rapid changes in physiological characteristics and silver concentration in plant tissue at the beginning of each AgNPs exposure (6 h, 36 h, and 9 days), while continuous AgNP and sulfidized AgNP chronic treatments gave delayed responses. Both <i>E. densa</i> and <i>J. effusus</i> enhanced their tolerance to AgNPs toxicity by increasing POD and SOD activities to scavenge free radicals but at different growth phases. Chlorophyll did not change. After AgNPs exposure, MDA, an index of membrane damage, was higher in submerged <i>E. densa</i> than emergent <i>J. effusus</i>, which suggested that engineered nanoparticles exerted more stress to submerged macrophytes

Tropical peatland carbon storage linked to global latitudinal trends in peat recalcitrance

Peatlands represent large terrestrial carbon banks. Given that most peat accumulates in boreal regions, where low temperatures and water saturation preserve organic matter, the existence of peat in (sub)tropical regions remains enigmatic. Here we examined peat and plant chemistry across a latitudinal transect from the Arctic to the tropics. Near-surface low-latitude peat has lower carbohydrate and greater aromatic content than near-surface high-latitude peat, creating a reduced oxidation state and resulting recalcitrance. This recalcitrance allows peat to persist in the (sub)tropics despite warm temperatures. Because we observed similar declines in carbohydrate content with depth in high-latitude peat, our data explain recent field-scale deep peat warming experiments in which catotelm (deeper) peat remained stable despite temperature increases up to 9 degrees C. We suggest that high-latitude deep peat reservoirs may be stabilized in the face of climate change by their ultimately lower carbohydrate and higher aromatic composition, similar to tropical peats.US Department of Energy Office of Biological and Environmental Research under the Terrestrial Ecosystem Sciences program [DE-SC0012272]; NASA Interdisciplinary Studies in Earth Science program [NNX17AK10G]; US Department of Energy Office of Biological and Environmental Research under the Genomic Science program [DE-SC0016440, DE-SC0004632, DE-SC0010580]; Geo. X, the Research Network for Geosciences in Berlin and Potsdam; US Department of Energy, Office of Science, Office of Biological and Environmental Research [DE-SC0012088]; NSF [0628647]; Natural Sciences and Engineering Research Council of Canada; National Research Foundation Singapore through the Singapore-MIT Alliance for Research and Technology's Center for Environmental Sensing and Modeling interdisciplinary research program; USA National Science Foundation [1114155, 1114161]; NASA LaRC POWER ProjectOpen access journal.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Tropical peatland carbon storage linked to global latitudinal trends in peat recalcitrance

Peatlands represent large terrestrial carbon banks. Given that most peat accumulates in boreal regions, where low temperatures and water saturation preserve organic matter, the existence of peat in (sub)tropical regions remains enigmatic. Here we examined peat and plant chemistry across a latitudinal transect from the Arctic to the tropics. Near-surface low-latitude peat has lower carbohydrate and greater aromatic content than near-surface high-latitude peat, creating a reduced oxidation state and resulting recalcitrance. This recalcitrance allows peat to persist in the (sub)tropics despite warm temperatures. Because we observed similar declines in carbohydrate content with depth in high-latitude peat, our data explain recent field-scale deep peat warming experiments in which catotelm (deeper) peat remained stable despite temperature increases up to 9 °C. We suggest that high-latitude deep peat reservoirs may be stabilized in the face of climate change by their ultimately lower carbohydrate and higher aromatic composition, similar to tropical peats.National Science Foundation (Grant 1114155)National Science Foundation (Grant 1114161)NSF (Award 0628647)US Department of Energy, Office of Science, Office of Biological and Environmental Research (contract DE-SC0012088)US Department of Energy Office of Biological and Environmental Research under the Genomic Science program (Award DE-SC0004632)US Department of Energy Office of Biological and Environmental Research under the Genomic Science program (Award DE-SC0010580)US Department of Energy Office of Biological and Environmental Research under the Genomic Science program (Award DE-SC0016440)NASA Interdisciplinary Studies in Earth Science program (Award NNX17AK10G)US Department of Energy Office of Biological and Environmental Research under the Terrestrial Ecosystem Sciences program (Award DE-SC0012272