Vol. 17, No. 2

Contents: Coming Together to Address Student Aggression and School Safety, by William C. Kling Recent Developments, by the Student Editorial Board Further References, compiled by Margaret A. Chaplanhttps://scholarship.kentlaw.iit.edu/iperr/1063/thumbnail.jp

Vol. 17, No. 2

Contents: Coming Together to Address Student Aggression and School Safety, by William C. Kling Recent Developments, by the Student Editorial Board Further References, compiled by Margaret A. Chaplanhttps://scholarship.kentlaw.iit.edu/iperr/1063/thumbnail.jp

Benthic community metabolism in deep and shallow Arctic lakes during 13 years of whole–lake fertilization

Benthic primary production and oxygen consumption are important components of lake biogeochemical cycling. We performed whole–lake nutrient manipulations in Arctic Alaska to assess the controls of lake morphometry, nutrients, and light on benthic community metabolism. One deep, stratified lake (Lake E5) and one shallow, well–mixed lake (Lake E6) in the Alaskan Arctic were fertilized with low levels of nitrogen (56 mg N m−3 yr−1) and phosphorus (8 mg P m−3 yr−1) from 2001 to 2013. Benthic primary production was not stimulated by fertilization in either lake. In the deep lake, decreased water clarity is consistent with an increase in phytoplankton biomass during fertilization. Benthic GPP decreased by 7–47 mg C m−2 d−1 (not statistically significant) and benthic respiration increased from 87 ± 20 to 167 ± 9 (SE) mg C m−2 d−1. The areal hypolimnetic oxygen deficit increased by 15 mg O2 m−2 d−1 each year during the 13 yr of monitoring, apparently driven by lower (more negative) benthic NEP. In the shallow lake, phytoplankton concentration did not change with fertilization. As a result, the light environment did not change and benthic GPP did not decrease. Overall the data suggest that (1) benthic algae are not nutrient limited in either the deep or shallow lake, (2) lake morphometry modulated the overall nutrient impact on benthic metabolism by controlling the response of phytoplankton, and by extension, light and organic carbon supply to the benthos, (3) year–to–year variability in light attenuation explains considerable variability in benthic GPP between lakes and years, (4) correlations between both dissolved organic carbon concentrations and light attenuation coefficients (kd) between lakes suggests a regional control on light attenuation, and (5) the dissolved oxygen concentrations in the deep experimental lake are highly sensitive to nutrient enrichment.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/113758/1/lno10120.pd

Ecosystem responses to climate change at a Low Arctic and a High Arctic long-term research site

© The Author(s), 2017. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ambio 46, Supple. 1 (2017): 160-173, doi:10.1007/s13280-016-0870-x.Long-term measurements of ecological effects of warming are often not statistically significant because of annual variability or signal noise. These are reduced in indicators that filter or reduce the noise around the signal and allow effects of climate warming to emerge. In this way, certain indicators act as medium pass filters integrating the signal over years-to-decades. In the Alaskan Arctic, the 25-year record of warming of air temperature revealed no significant trend, yet environmental and ecological changes prove that warming is affecting the ecosystem. The useful indicators are deep permafrost temperatures, vegetation and shrub biomass, satellite measures of canopy reflectance (NDVI), and chemical measures of soil weathering. In contrast, the 18-year record in the Greenland Arctic revealed an extremely high summer air-warming of 1.3°C/decade; the cover of some plant species increased while the cover of others decreased. Useful indicators of change are NDVI and the active layer thickness.The Toolik research was supported in part by NSF Grants DEB 0207150, DEB 1026843, ARC 1107701, and ARC 1504006

Summer CO2 evasion from streams and rivers in the Kolyma River basin, north-east Siberia

Inland water systems are generally supersaturated in carbon dioxide (CO2) and are increasingly recognized as playing an important role in the global carbon cycle. The Arctic may be particularly important in this respect, given the abundance of inland waters and carbon contained in Arctic soils; however, a lack of trace gas measurements from small streams in the Arctic currently limits this understanding.We investigated the spatial variability of CO2 evasion during the summer low-flow period from streams and rivers in the northern portion of the Kolyma River basin in north-eastern Siberia. To this end, partial pressure of carbon dioxide (pCO2) and gas exchange velocities (k) were measured at a diverse set of streams and rivers to calculate CO2 evasion fluxes. We combined these CO2 evasion estimates with satellite remote sensing and geographic information system techniques to calculate total areal CO2 emissions. Our results show that small streams are substantial sources of atmospheric CO2 owing to high pCO2 and k, despite being a small portion of total inland water surface area. In contrast, large rivers were generally near equilibrium with atmospheric CO2. Extrapolating our findings across the Panteleikha-Ambolikha sub-watersheds demonstrated that small streams play a major role in CO2 evasion, accounting for 86% of the total summer CO2 emissions from inland waters within these two sub-watersheds. Further expansion of these regional CO2 emission estimates across time and space will be critical to accurately quantify and understand the role of Arctic streams and rivers in the global carbon budget

Pulse‐labeling studies of carbon cycling in arctic tundra ecosystems: Contribution of photosynthates to soil organic matter

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95486/1/gbc827.pd

A communal catalogue reveals Earth’s multiscale microbial diversity

Our growing awareness of the microbial world’s importance and diversity contrasts starkly with our limited understanding of its fundamental structure. Despite recent advances in DNA sequencing, a lack of standardized protocols and common analytical frameworks impedes comparisons among studies, hindering the development of global inferences about microbial life on Earth. Here we present a meta-analysis of microbial community samples collected by hundreds of researchers for the Earth Microbiome Project. Coordinated protocols and new analytical methods, particularly the use of exact sequences instead of clustered operational taxonomic units, enable bacterial and archaeal ribosomal RNA gene sequences to be followed across multiple studies and allow us to explore patterns of diversity at an unprecedented scale. The result is both a reference database giving global context to DNA sequence data and a framework for incorporating data from future studies, fostering increasingly complete characterization of Earth’s microbial diversity