scholarly journals Trophic status and local conditions affect microbial potential for denitrification versus internal nitrogen cycling in lake sediments

2021 ◽  
Author(s):  
Kathrin B.L. Baumann ◽  
Raoul Thoma ◽  
Cameron M. Callbeck ◽  
Robert Niederdorfer ◽  
Carsten Schubert ◽  
...  
Keyword(s):  
Lake Sediments ◽  
Aquatic Ecosystems ◽  
Essential Element ◽  
Oligotrophic Lake ◽  
Environmental Drivers ◽  
Nutrient Concentrations ◽  
Local Conditions ◽  
N Cycle ◽  
N Transformation ◽  
N Removal

The nitrogen (N) cycle is of global importance as N is an essential element and a limiting nutrient in terrestrial and aquatic ecosystems. Excessive anthropogenic N fertilizer usage threatens sensitive downstream aquatic ecosystems. Although freshwater lake sediments remove N through various microbial transformation processes, few studies have investigated the microbial communities involved. In an integrated biogeochemical and microbiological study on a eutrophic and oligotrophic lake, we estimated N removal rates in the sediments from porewater concentration gradients. Simultaneously, the abundance of different microbial N transformation genes was investigated using metagenomics on a seasonal and spatial scale. We observed that contrasting nutrient concentrations in the sediments were reflected in distinct microbial community compositions and significant differences in the abundance of various N transformation genes. Within each lake, we observed a more pronounced spatial than seasonal variability. The eutrophic Lake Baldegg showed a higher denitrification potential with higher nosZ gene (N2O reductase) abundance and higher nirS:nirK (nitrite reductase) ratio, indicating a greater capacity for complete denitrification. Correspondingly, this lake had a higher N removal efficiency. The oligotrophic Lake Sarnen, in contrast, had a higher potential for DNRA and nitrification, and specifically a high abundance of Nitrospirae, including some capable of comammox. In general, the oligotrophic lake ecosystems had a higher microbial diversity, thus acting as an important habitat for oligotrophic microbes. Our results demonstrate that knowledge of the genomic N transformation potential is important for interpreting N process rates and understanding the limitations of the N cycle response to environmental drivers.

scholarly journals Nitrogen removal processes in lakes of different trophic states from on-site measurements and historic data

2021 ◽  
Vol 83 (2) ◽  
Author(s):  
Beat Müller ◽  
Raoul Thoma ◽  
Kathrin B. L. Baumann ◽  
Cameron M. Callbeck ◽  
Carsten J. Schubert
Keyword(s):  
Eutrophic Lake ◽  
Oligotrophic Lake ◽  
Removal Rates ◽  
N Removal ◽  
Central Switzerland ◽  
Denitrification Activity ◽  
Historic Data ◽  
Anthropogenic Nitrogen ◽  
Removal Processes ◽  
Sediment Interface

AbstractFreshwater lakes are essential hotspots for the removal of excessive anthropogenic nitrogen (N) loads transported from the land to coastal oceans. The biogeochemical processes responsible for N removal, the corresponding transformation rates and overall removal efficiencies differ between lakes, however, it is unclear what the main controlling factors are. Here, we investigated the factors that moderate the rates of N removal under contrasting trophic states in two lakes located in central Switzerland. In the eutrophic Lake Baldegg and the oligotrophic Lake Sarnen, we specifically examined seasonal sediment porewater chemistry, organic matter sedimentation rates, as well as 33-year of historic water column data. We find that the eutrophic Lake Baldegg, which contributed to the removal of 20 ± 6.6 gN m−2 year−1, effectively removed two-thirds of the total areal N load. In stark contrast, the more oligotrophic Lake Sarnen contributed to 3.2 ± 4.2 gN m−2 year−1, and had removed only one-third of the areal N load. The historic dataset of the eutrophic lake revealed a close linkage between annual loads of dissolved N (DN) and removal rates (NRR = 0.63 × DN load) and a significant correlation of the concentration of bottom water nitrate and removal rates. We further show that the seasonal increase in N removal rates of the eutrophic lake correlated significantly with seasonal oxygen fluxes measured across the water–sediment interface (R2 = 0.75). We suggest that increasing oxygen enhances sediment mineralization and stimulates nitrification, indirectly enhancing denitrification activity.

scholarly journals Use of diffusion samplers in oligotrophic lake sediments: Effects of free oxygen in sampler material

1994 ◽  
Vol 39 (2) ◽  
pp. 468-474 ◽  
Author(s):  
Richard Carignan ◽  
Sylvie St-Pierre ◽  
Rene Gachter
Keyword(s):  
Lake Sediments ◽  
Oligotrophic Lake ◽  
Free Oxygen

scholarly journals Microplastics in the Environment: Raising Awareness in Primary Education

2020 ◽  
Vol 82 (7) ◽  
pp. 478-487
Author(s):  
Patricia Raab ◽  
Franz X. Bogner
Keyword(s):  
Everyday Life ◽  
Aquatic Ecosystems ◽  
Essential Element ◽  
Purchase Decisions ◽  
Marine Animals ◽  
Student Centered ◽  
Environmental Threat ◽  
Raising Awareness ◽  
Hands On ◽  
Hands On Learning

Microplastic pollution is an environmental threat with substantial effects on ecosystems. Persistence and ubiquity are the central causes of the problems microplastics generate, especially throughout water-based food webs. To limit microplastic pollution, accountability of individuals is needed, which requires reliable information for an individual to act accordingly. Knowledge about sources, contamination, fate, and effects of microplastic in the environment may be an essential element in enhancing students' motivation and sense of responsibility. Our module “Plastic Detectives – The Search for Plastic” offers consciousness-raising tasks that involve students in hands-on learning activities. Within student-centered activities, different tasks on sources in everyday life, sinks in aquatic ecosystems, effects on marine animals, and prevention strategies for microplastics are in focus. With an appropriate overview, students may be sufficiently enabled to ponder their purchase decisions and potentially limit microplastic pollution in everyday life.

scholarly journals The impact of accelerating land-use change on the N-Cycle of tropical aquatic ecosystems: Current conditions and projected changes

1999 ◽  
Vol 46 (1-3) ◽  
pp. 109-148 ◽  
Author(s):  
J. A. Downing ◽  
M. Mcclain ◽  
R. Twilley ◽  
J. M. Melack ◽  
J. Elser ◽  
...  
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Aquatic Ecosystems ◽  
N Cycle ◽  
Tropical Aquatic Ecosystems ◽  
Projected Changes ◽  
The Impact

scholarly journals Nitrogen transformations along a shallow subterranean estuary

2016 ◽  
Author(s):  
Mathilde Couturier ◽  
Christian Nozais ◽  
Alexandra Rao ◽  
Gwendoline Tommi-Morin ◽  
Maude Sirois ◽  
...  
Keyword(s):  
Groundwater Flow ◽  
Coastal Waters ◽  
Chemical Constituents ◽  
Flow Path ◽  
Discharge Zone ◽  
Nutrient Concentrations ◽  
N Transformations ◽  
N Removal ◽  
N Fluxes ◽  
Biogeochemical Transformations

Abstract. The transformations of chemical constituents in subterranean estuaries (STE) control the delivery of nutrient loads from aquifers to the coastal ocean. It is important to determine the processes and sources that affect nutrient concentrations at a local scale in order to accurately estimate global nutrient fluxes via submarine groundwater discharge (SGD), particularly in boreal environments, where data are still very scarce. Here, the biogeochemical transformations of nitrogen (N) species were examined within the STE of a microtidal boreal sandy beach located in the Îles-de-la-Madeleine (Québec, Canada). This study reveals the vertical and horizontal distribution of nitrate (NO3−), nitrite (NO2−), ammonia (NH4+), dissolved organic nitrogen (DON) and total dissolved nitrogen (TDN) measured in beach groundwater during four spring seasons (June 2011, 2012, 2013 and 2015) when aquifer recharge is maximal after snow melt. Inland groundwater supplied high concentrations of NOx− and DON to the STE, whereas inputs from seawater were very limited. Non-conservative behaviour was observed along the groundwater flow path, leading to low NOx− and high NH4+ concentrations in the discharge zone. The long residence time of groundwater within the beach (~ 82 days), coupled with oxygen-depleted conditions and high carbon concentrations created a favourable environment for N transformations such as heterotrophic denitrification and ammonium production. An estimate of SGD fluxes of N was determined to account for biogeochemical transformations within the STE. Fresh inland groundwater delivers 37.54 mol m−1 y−1 of NOx and 63.57 mol m−1 y−1 of DON to the STE, and NH4+ input was negligible. But the N load to coastal waters is dominated by NH4+ and DON, due to N transformations along the flow path. NH4+ represents 99 % of the DIN flux to coastal waters, at 42.80 mol m−1 y−1. Since N fluxes to the coastal bay (88 mol m−1 y−1) are slightly lower than N fluxes from fresh inland groundwater (102 mol m−1 y−1), the STE appears to be a sink of terrestrially-derived N. The net transformations of N in the STE led to N removal along the groundwater flow path along the groundwater flow path.

scholarly journals Socioeconomic and Environmental Impacts on Regional Tourism across Chinese Cities: A Spatiotemporal Heterogeneous Perspective

2021 ◽  
Vol 10 (6) ◽  
pp. 410
Author(s):  
Xu Zhang ◽  
Chao Song ◽  
Chengwu Wang ◽  
Yili Yang ◽  
Zhoupeng Ren ◽  
...  
Keyword(s):  
Population Density ◽  
Vegetation Index ◽  
Tourism Development ◽  
Temporal Variations ◽  
Tourism Industry ◽  
Environmental Drivers ◽  
Night Time ◽  
Local Conditions ◽  
Varying Coefficients ◽  
Economic Level

Understanding geospatial impacts of multi-sourced drivers on the tourism industry is of great significance for formulating tourism development policies tailored to regional-specific needs. To date, no research in China has explored the combined impacts of socioeconomic and environmental drivers on city-level tourism from a spatiotemporal heterogeneous perspective. We collected the total tourism revenue indicator and 30 potential influencing factors from 343 cities across China during 2008–2017. Three mainstream regressions and an emerging local spatiotemporal regression named the Bayesian spatiotemporally varying coefficients (Bayesian STVC) model were constructed to investigate the global-scale stationary and local-scale spatiotemporal nonstationary relationships between city-level tourism and various vital drivers. The Bayesian STVC model achieved the best model performance. Globally, eight socioeconomic and environmental factors, average wage (coefficient: 0.47, 95% credible intervals: 0.43–0.51), employed population (−0.14, −0.17–−0.11), GDP per capita (0.47, 0.42–0.52), population density (0.21, 0.16–0.27), night-time light index (−0.01, −0.08–0.05), slope (0.10, 0.06–0.14), vegetation index (0.66, 0.63–0.70), and road network density (0.34, 0.29–0.38), were identified to have nonlinear effects on tourism. Temporally, the main drivers might have gradually changed from the local macro-economic level, population density, and natural environment conditions to the individual economic level over the last decade. Spatially, city-specific dynamic maps of tourism development and geographically clustered influencing maps for eight drivers were produced. In 2017, China formed four significant city-level tourism industry clusters (hot spots, 90% confidence), the locations of which coincide with China’s top four urban agglomerations. Our local spatiotemporal analysis framework for geographical tourism data is expected to provide insights into adjusting regional measures to local conditions and temporal variations in broader social and natural sciences.

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