Monitoring a changing Arctic: Recent advancements in the study of sea ice microbial communities

Sea ice continues to decline across many regions of the Arctic, with remaining ice becoming increasingly younger and more dynamic. These changes alter the habitats of microbial life that live within the sea ice, which support healthy functioning of the marine ecosystem and provision of resources for human-consumption, in addition to influencing biogeochemical cycles (e.g. air–sea CO₂ exchange). With the susceptibility of sea ice ecosystems to climate change, there is a pressing need to fill knowledge gaps surrounding sea ice habitats and their microbial communities. Of fundamental importance to this goal is the development of new methodologies that permit effective study of them. Based on outcomes from the DiatomARCTIC project, this paper integrates existing knowledge with case studies to provide insight on how to best document sea ice microbial communities, which contributes to the sustainable use and protection of Arctic marine and coastal ecosystems in a time of environmental change.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13280-021-01658-z.     

Biogeochemical consequences of a changing Arctic shelf seafloor ecosystem

Unprecedented and dramatic transformations are occurring in the Arctic in response to climate change, but academic, public, and political discourse has disproportionately focussed on the most visible and direct aspects of change, including sea ice melt, permafrost thaw, the fate of charismatic megafauna, and the expansion of fisheries. Such narratives disregard the importance of less visible and indirect processes and, in particular, miss the substantive contribution of the shelf seafloor in regulating nutrients and sequestering carbon. Here, we summarise the biogeochemical functioning of the Arctic shelf seafloor before considering how climate change and regional adjustments to human activities may alter its biogeochemical and ecological dynamics, including ecosystem function, carbon burial, or nutrient recycling. We highlight the importance of the Arctic benthic system in mitigating climatic and anthropogenic change and, with a focus on the Barents Sea, offer some observations and our perspectives on future management and policy.     

Modelling Phosphorus Retention in Lakes and Reservoirs

Steady-state models for the prediction of P retention coefficient (R) in lakes were evaluated using data from 93 natural lakes and 119 reservoirs situated in the temperate zone. Most of the already existing models predicted R relatively successfully in lakes while it was seriously under-estimated in reservoirs. A statistical analysis indicated the main causes of differences in R between lakes and reservoirs: (a) distinct relationships between P sedimentation coefficient, depth, and water residence time; (b) existence of significant inflow–outflow P concentration gradients in reservoirs. Two new models of different complexity were developed for estimating R in reservoirs: , where τ is water residence time (year), was derived from the Vollenweider/Larsen and Mercier model by adding a calibrated parameter accounting for spatial P non-homogeneity in the water body, and is applicable for reservoirs but not lakes, and , where [P_in] is volume-weighted P concentration in all inputs to the water body (μg l⁻¹), was obtained by re-calibrating the OECD general equation, and is generally applicable for both lakes and reservoirs. These optimised models yield unbiased estimates over a large range of reservoir types.     

Cement/clay interactions-- a review: experiments, natural analogues, and modeling

The concept of storing radioactive waste in geological formations calls for large quantities of concrete that will be in contact with the clay material of the engineered barriers as well as with the geological formation. France, Switzerland and Belgium are studying the option of clayey geological formations. The clay and cement media have very contrasted chemistries that will interact and lead to a degradation of both types of material. The purpose of this review is to establish an exhaustive list of laboratory experiments so as to identify the reaction sequences in the evolution of both the clay minerals and accessory minerals during their alteration in an alkaline environment. We review the data on clay dissolution kinetics in this environment, and include an invaluable study of natural analogues that allow one to correlate the phenomena in time. The available data and experiments make it possible to construct predictive numerical models. However, as the quality of the data is inhomogeneous, we recommend a continuation of the thermodynamic and kinetic data acquisition. It is obvious that the numerical modeling of the alkaline disturbance will be more relevant if it can combine the advantages of the different detailed models: mineralogical completeness, combined modeling of the clay and cement media, evolution of the porosity, consideration of the pCO2 and all the surface reactions.     

Pilot project of mechanical-biological treatment of waste in Brazil

By mechanical-biological treatment (MBT) of residual municipal solid waste the behaviour of landfills can be significantly improved. After MBT the organic content (COD and BOD5), total organic carbon, and total nitrogen in the leachate, as well as the gas production rate, are reduced to values lower than 90% of the fresh untreated waste. The volume of the stabilized material to be disposed on landfills decreases enormously, by up to 70%. The monitoring effort for a landfill constructed under these conditions is reduced to a minimum and the stabilized material can be used in other ways, as material for reforestation, for cover material or for thermal utilization to produce energy. Environmental conditions are important in MBT, as well as waste characteristics. This paper describes the results of a pilot project of MBT performed in Rio de Janeiro, Brazil. The results have shown that this technology can be used successfully in developing countries, with economy for the society and important results for the environment.     

Impacts of land cover on stream hydrology in the West Georgia Piedmont, USA

The southeastern United States is experiencing rapid urban development. Consequently, Georgia's streams are experiencing hydrologic alterations from extensive development and from other land use activities such as livestock grazing and silviculture. A study was performed to assess stream hydrology within 18 watersheds ranging from 500 to 2500 ha. Study streams were first, second, or third order and hydrology was continuously monitored from 29 July 2003 to 23 September 2004 using InSitu pressure transducers. Rating curves between stream stage (i.e., water depth) and discharge were developed for each stream by correlating biweekly discharge measurements and stage data. Dependent variables were calculated from discharge data and placed into 4 categories: flow frequency (i.e., the number of times a predetermined discharge threshold is exceeded), flow magnitude (i.e., maximum and minimum flows), flow duration (i.e., the amount of time discharge was above or below a predetermined threshold), and flow predictability and flashiness. Fine resolution data (i.e., 15-min interval) were also compared to daily discharge data to determine if resolution affected how streams were classified hydrologically. Urban watersheds experienced flashy discharges during storm events, whereas pastoral and forested watersheds showed less flashy hydrographs. Also, in comparison to all other flow variables, flow frequency measures were most strongly correlated to land cover. Furthermore, the stream hydrology was explained similarly with both the 15-min and daily data resolutions.     

Sorption dynamics of organic and inorganic phosphorus compounds in soil

Phosphorus retention in soils is influenced by the form of P added. The potential impact of one P compound on the sorption of other P compounds in soils has not been widely reported. Sorption isotherms were utilized to quantify P retention by benchmark soils from Indiana, Missouri, and North Carolina when P was added as inorganic P (Pi) or organic P (beta-D-glucose-6-phosphate, G6P; adenosine 5'-triphosphate, ATP; and myoinositol hexaphosphate, IP6) and to determine whether soil P sorption by these organic P compounds and Pi was competitive. Isotherm supernatants were analyzed for pH and total P using standard protocols, while Pi and organic P compounds were assayed using ion chromatography. Under the controlled conditions of this study, the affinity of all soils for P sources followed the order IP6 > G6P > ATP > Pi. Each organic P source had a different potential to desorb Pi from soils, and the order of greatest to least Pi desorption was G6P > ATP > IP6. Glucose-6-phosphate and ATP competed more directly with Pi for sorption sites than IP6 at greater rates of P addition, but at the lesser rates of P addition, IP6 actually desorbed more Pi. Inositol hexaphosphate was strongly sorbed by all three soils and was relatively unaffected by the presence of other P sources. Decreased total P sorption due to desorption of Pi can be caused by relatively small additions of organic P, which may help explain vertical P movement in manured soils. Sorption isotherms performed using Pi alone did not accurately predict total P sorption in soils.     

Use of beryllium-7 to document soil redistribution following forest harvest operations

Rapid and reliable methods for documenting soil erosion associated with forest harvest operations are needed to support the development of best management practices for soil and water conservation. To address this need, the potential for using 7Be measurements to estimate patterns and amounts of soil redistribution associated with individual post-harvest events was explored. The 7Be technique, which was originally developed for use on agricultural land, was employed to estimate soil redistribution associated with a period of heavy rainfall within a harvested forest area located in the Lake Region of Chile (39 degrees 44'7' S, 73 degrees 10'39' W; 22% slope; and mean annual rainfall 2300 mm yr(-1)). The results provided by the 7Be technique were validated against direct measurements of soil gain or loss during the same period obtained using erosion pins. The information produced by the two approaches was similar. The results of this study demonstrate the potential for using 7Be measurements to document event-based erosion in recently harvested forest areas.     

Effects of elevated atmospheric carbon dioxide on biomass and carbon accumulation in a model regenerating longleaf pine community

Plant species vary in response to atmospheric CO2 concentration due to differences in physiology, morphology, phenology, and symbiotic relationships. These differences make it very difficult to predict how plant communities will respond to elevated CO2. Such information is critical to furthering our understanding of community and ecosystem responses to global climate change. To determine how a simple plant community might respond to elevated CO2, a model regenerating longleaf pine community composed of five species was exposed to two CO2 regimes (ambient, 365 micromol mol(-1) and elevated, 720 micromol mol(-1)) for 3 yr. Total above- and belowground biomass was 70 and 49% greater, respectively, in CO2-enriched plots. Carbon (C) content followed a response pattern similar to biomass, resulting in a significant increase of 13.8 Mg C ha(-1) under elevated CO2. Responses of individual species, however, varied. Longleaf pine (Pinus palustris Mill.) was primarily responsible for the positive response to CO2 enrichment. Wiregrass (Aristida stricta Michx.), rattlebox (Crotalaria rotundifolia Walt. Ex Gmel.), and butterfly weed (Asclepias tuberosa L.) exhibited negative above- and belowground biomass responses to elevated CO2, while sand post oak (Quercus margaretta Ashe) did not differ significantly between CO2 treatments. As with pine, C content followed patterns similar to biomass. Elevated CO2 resulted in alterations in community structure. Longleaf pine comprised 88% of total biomass in CO2-enriched plots, but only 76% in ambient plots. In contrast, wiregrass, rattlebox, and butterfly weed comprised 19% in ambient CO2 plots, but only 8% under high CO2. Therefore, while longleaf pine may perform well in a high CO2 world, other members of this community may not compete as well, which could alter community function. Effects of elevated CO2 on plant communities are complex, dynamic, and difficult to predict, clearly demonstrating the need for more research in this important area of global change science.     

Phosphorus fractions in manure from growing pigs receiving diets containing micronized peas and supplemental enzymes

Different livestock feeds manipulations have been reported to reduce the total P concentration in manure. Information on the influence of these dietary manipulation strategies on the forms of P in manure is, however, limited. This study was, therefore, conducted to investigate the effect of diet manipulation through feed micronization and enzyme supplementation on the forms of P in swine manure. Eight growing pigs were fed four diets: barley-raw pea (BRP), barley-micronized pea (BMP), barley-raw pea with enzyme (BRPE), and barley-micronized pea with enzyme (BMPE) in a 4 x 4 Latin square design. Because we are interested in the effect of enzyme cocktail and pea micronization on manure P, we did not reduce the non-phytate P with enzyme addition in this study. The fecal material and urine were collected and analyzed for total P. Fecal material was fractionated to determine the total P in H2O-, NaHCO3-, NaOH-, and HCl-extractable fractions. The total P in the residual fractions was also determined. About 98% of the total P excreted by the pigs was found in the fecal material. Inclusion of micronized pea in pig diet did not have any significant effect (p > 0.1) on either the total P or the different P fractions in the manure. The labile P (the sum of H2O-P and NaHCO3-P) was significantly reduced (p < 0.05) by the addition of enzyme to swine diets. Pigs fed the BRPE and BMPE had 14 and 18% lower labile P, respectively, compared with pigs fed the BRP. Enzyme addition to pig diets reduced not only the total P in manure, but also the labile P fraction, which is of great environmental concern. Thus, the potential of P loss to runoff and the subsequent eutrophication can be reduced by enzyme addition to pig diets.