Editorial: the oceanic particle flux and its cycling within the deep water column Conte, Maureen H.; Pedrosa-Pamies, Rut; Honda, Makio C.; Herndl, Gerhard J. The oceanic particle flux transfers energy and material from the surface through the water column to the seafloor. (See review by Conte (2019) and references therein). The particle flux fuels life below the sunlit photic zone, exerts a major control on the global cycling of carbon and particle-associated elements, and also plays a major role in long-term carbon sequestration. In this Research Topic we present a collection of articles that provide a broad overview of current research on the interlinked processes controlling the magnitude and composition of the oceanic particle flux, and its cycling and depth attenuation within the deep water column. © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Conte, M., Pàmies, R., Honda, M., & Herndl, G. Editorial: the oceanic particle flux and its cycling within the deep water column. Frontiers in Earth Science, 10, (2022): 1020065, https://doi.org/10.3389/feart.2022.1020065.

The diversity and functional capacity of microbes associated with coastal macrophytes Miranda, Khashiff; Weigel, Brooke L.; Fogarty, Emily C.; Veseli, Iva A.; Giblin, Anne E.; Eren, A. Murat; Pfister, Catherine A. Coastal marine macrophytes exhibit some of the highest rates of primary productivity in the world. They have been found to host a diverse set of microbes, many of which may impact the biology of their hosts through metabolisms that are unique to microbial taxa. Here, we characterized the metabolic functions of macrophyte-associated microbial communities using metagenomes collected from 2 species of kelp (Laminaria setchellii and Nereocystis luetkeana) and 3 marine angiosperms (Phyllospadix scouleri, P. serrulatus, and Zostera marina), including the rhizomes of two surfgrass species (Phyllospadix spp.), the seagrass Zostera marina, and the sediments surrounding P. scouleri and Z. marina. Using metagenomic sequencing, we describe 63 metagenome-assembled genomes (MAGs) that potentially benefit from being associated with macrophytes and may contribute to macrophyte fitness through their metabolic activity. Host-associated metagenomes contained genes for the use of dissolved organic matter from hosts and vitamin (B1, B2, B7, B12) biosynthesis in addition to a range of nitrogen and sulfur metabolisms that recycle dissolved inorganic nutrients into forms more available to the host. The rhizosphere of surfgrass and seagrass contained genes for anaerobic microbial metabolisms, including nifH genes associated with nitrogen fixation, despite residing in a well-mixed and oxygenated environment. The range of oxygen environments engineered by macrophytes likely explains the diversity of both oxidizing and reducing microbial metabolisms and contributes to the functional capabilities of microbes and their influences on carbon and nitrogen cycling in nearshore ecosystems. © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Miranda, K., Weigel, B., Fogarty, E., Veseli, I., Giblin, A., Eren, A., & Pfister, C. The diversity and functional capacity of microbes associated with coastal macrophytes. MSystems, 7(5),(2022): e0059222, https://doi.org/10.1128/msystems.00592-22.

Cross-site comparisons of dryland ecosystem response to climate change in the US long-term ecological research network Hudson, Amy R.; Peters, Debra P. C.; Blair, John M.; Childers, Daniel L.; Doran, Peter T.; Geil, Kerrie L.; Gooseff, Michael N.; Gross, Katherine; Haddad, Nick M.; Pastore, Melissa A.; Rudgers, Jennifer A.; Sala, Osvaldo E.; Seabloom, Eric W.; Shaver, Gaius R. Long-term observations and experiments in diverse drylands reveal how ecosystems and services are responding to climate change. To develop generalities about climate change impacts at dryland sites, we compared broadscale patterns in climate and synthesized primary production responses among the eight terrestrial, nonforested sites of the United States Long-Term Ecological Research (US LTER) Network located in temperate (Southwest and Midwest) and polar (Arctic and Antarctic) regions. All sites experienced warming in recent decades, whereas drought varied regionally with multidecadal phases. Multiple years of wet or dry conditions had larger effects than single years on primary production. Droughts, floods, and wildfires altered resource availability and restructured plant communities, with greater impacts on primary production than warming alone. During severe regional droughts, air pollution from wildfire and dust events peaked. Studies at US LTER drylands over more than 40 years demonstrate reciprocal links and feedbacks among dryland ecosystems, climate-driven disturbance events, and climate change. © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Hudson, A. R., Peters, D. P. C., Blair, J. M., Childers, D. L., Doran, P. T., Geil, K., Gooseff, M., Gross, K. L., Haddad, N. M., Pastore, M. A., Rudgers, J. A., Sala, O., Seabloom, E. W., & Shaver, G. Cross-site comparisons of dryland ecosystem response to climate change in the US long-term ecological research network. Bioscience, 72(9), (2022): 889–907, https://doi.org/10.1093/biosci/biab134.

Diel light cycles affect phytoplankton competition in the global ocean Tsakalakis, Ioannis; Follows, Michael J.; Dutkiewicz, Stephanie; Follett, Christopher L.; Vallino, Joseph J. Aim Light, essential for photosynthesis, is present in two periodic cycles in nature: seasonal and diel. Although seasonality of light is typically resolved in ocean biogeochemical–ecosystem models because of its significance for seasonal succession and biogeography of phytoplankton, the diel light cycle is generally not resolved. The goal of this study is to demonstrate the impact of diel light cycles on phytoplankton competition and biogeography in the global ocean. Location Global ocean. Major taxa studied Phytoplankton. Methods We use a three-dimensional global ocean model and compare simulations of high temporal resolution with and without diel light cycles. The model simulates 15 phytoplankton types with different cell sizes, encompassing two broad ecological strategies: small cells with high nutrient affinity (gleaners) and larger cells with high maximal growth rate (opportunists). Both are grazed by zooplankton and limited by nitrogen, phosphorus and iron. Results Simulations show that diel cycles of light induce diel cycles in limiting nutrients in the global ocean. Diel nutrient cycles are associated with higher concentrations of limiting nutrients, by 100% at low latitudes (−40° to 40°), a process that increases the relative abundance of opportunists over gleaners. Size classes with the highest maximal growth rates from both gleaner and opportunist groups are favoured by diel light cycles. This mechanism weakens as latitude increases, because the effects of the seasonal cycle dominate over those of the diel cycle. Main conclusions Understanding the mechanisms that govern phytoplankton biogeography is crucial for predicting ocean ecosystem functioning and biogeochemical cycles. We show that the diel light cycle has a significant impact on phytoplankton competition and biogeography, indicating the need for understanding the role of diel processes in shaping macroecological patterns in the global ocean. © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Tsakalakis, I., Follows, M. J., Dutkiewicz, S., Follett, C. L., & Vallino, J. J. Diel light cycles affect phytoplankton competition in the global ocean. Global Ecology and Biogeography, 31(9), (2022): 1838-1849, https://doi.org/10.1111/geb.13562.

N and P constrain C in ecosystems under climate change: role of nutrient redistribution, accumulation, and stoichiometry Rastetter, Edward B.; Kwiatkowski, Bonnie L.; Kicklighter, David W.; Barker Plotkin, Audrey; Genet, Helene; Nippert, Jesse B.; O'Keefe, Kimberly; Perakis, Steven S.; Porder, Stephen; Roley, Sarah S.; Ruess, Roger W.; Thompson, Jonathan R.; Wieder, William R.; Wilcox, Kevin R.; Yanai, Ruth D. We use the Multiple Element Limitation (MEL) model to examine responses of 12 ecosystems to elevated carbon dioxide (CO2), warming, and 20% decreases or increases in precipitation. Ecosystems respond synergistically to elevated CO2, warming, and decreased precipitation combined because higher water-use efficiency with elevated CO2 and higher fertility with warming compensate for responses to drought. Response to elevated CO2, warming, and increased precipitation combined is additive. We analyze changes in ecosystem carbon (C) based on four nitrogen (N) and four phosphorus (P) attribution factors: (1) changes in total ecosystem N and P, (2) changes in N and P distribution between vegetation and soil, (3) changes in vegetation C:N and C:P ratios, and (4) changes in soil C:N and C:P ratios. In the combined CO2 and climate change simulations, all ecosystems gain C. The contributions of these four attribution factors to changes in ecosystem C storage varies among ecosystems because of differences in the initial distributions of N and P between vegetation and soil and the openness of the ecosystem N and P cycles. The net transfer of N and P from soil to vegetation dominates the C response of forests. For tundra and grasslands, the C gain is also associated with increased soil C:N and C:P. In ecosystems with symbiotic N fixation, C gains resulted from N accumulation. Because of differences in N versus P cycle openness and the distribution of organic matter between vegetation and soil, changes in the N and P attribution factors do not always parallel one another. Differences among ecosystems in C-nutrient interactions and the amount of woody biomass interact to shape ecosystem C sequestration under simulated global change. We suggest that future studies quantify the openness of the N and P cycles and changes in the distribution of C, N, and P among ecosystem components, which currently limit understanding of nutrient effects on C sequestration and responses to elevated CO2 and climate change. © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Rastetter, E., Kwiatkowski, B., Kicklighter, D., Plotkin, A., Genet, H., Nippert, J., O’Keefe, K., Perakis, S., Porder, S., Roley, S., Ruess, R., Thompson, J., Wieder, W., Wilcox, K., & Yanai, R. N and P constrain C in ecosystems under climate change: role of nutrient redistribution, accumulation, and stoichiometry. Ecological Applications, (2022): e2684, https://doi.org/10.1002/eap.2684.

Impoundment increases methane emissions in Phragmites‐invaded coastal wetlands Sanders-DeMott, Rebecca; Eagle, Meagan; Kroeger, Kevin D.; Wang, Faming; Brooks, Thomas W.; O'Keefe Suttles, Jennifer A.; Nick, Sydney K.; Mann, Adrian G.; Tang, Jianwu Saline tidal wetlands are important sites of carbon sequestration and produce negligible methane (CH4) emissions due to regular inundation with sulfate-rich seawater. Yet, widespread management of coastal hydrology has restricted tidal exchange in vast areas of coastal wetlands. These ecosystems often undergo impoundment and freshening, which in turn cause vegetation shifts like invasion by Phragmites, that affect ecosystem carbon balance. Understanding controls and scaling of carbon exchange in these understudied ecosystems is critical for informing climate consequences of blue carbon restoration and/or management interventions. Here, we (1) examine how carbon fluxes vary across a salinity gradient (4–25 psu) in impounded and natural, tidally unrestricted Phragmites wetlands using static chambers and (2) probe drivers of carbon fluxes within an impounded coastal wetland using eddy covariance at the Herring River in Wellfleet, MA, United States. Freshening across the salinity gradient led to a 50-fold increase in CH4 emissions, but effects on carbon dioxide (CO2) were less pronounced with uptake generally enhanced in the fresher, impounded sites. The impounded wetland experienced little variation in water-table depth or salinity during the growing season and was a strong CO2 sink of −352 g CO2-C m−2 year−1 offset by CH4 emission of 11.4 g CH4-C m−2 year−1. Growing season CH4 flux was driven primarily by temperature. Methane flux exhibited a diurnal cycle with a night-time minimum that was not reflected in opaque chamber measurements. Therefore, we suggest accounting for the diurnal cycle of CH4 in Phragmites, for example by applying a scaling factor developed here of ~0.6 to mid-day chamber measurements. Taken together, these results suggest that although freshened, impounded wetlands can be strong carbon sinks, enhanced CH4 emission with freshening reduces net radiative balance. Restoration of tidal flow to impounded ecosystems could limit CH4 production and enhance their climate regulating benefits. © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Sanders‐DeMott, R., Eagle, M., Kroeger, K., Wang, F., Brooks, T., Suttles, J., Nick, S., Mann, A., & Tang, J. Impoundment increases methane emissions in Phragmites‐invaded coastal wetlands. Global Change Biology, 28(15), (2022): 4539– 4557. https://doi.org/10.1111/gcb.16217.

Editorial: seagrasses under times of change Winters, Gidon; Teichberg, Mirta; Reuter, Hauke; Viana, Ines G.; Willette, Demian A. Awareness of the ecological importance of seagrasses is growing due to recent attention to their role in carbon sequestration as a potential blue carbon sink (Fourqurean et al., 2012; Bedulli et al.), as well as their role in nutrient cycling (Romero et al., 2006), sediment stabilization (James et al., 2019), pathogen filtration (Lamb et al., 2017), and the formation of essential habitats for economically important marine species (Jackson et al., 2001; Jones et al.). Despite their importance and the increasing public and scientific awareness of seagrasses, simultaneous global (e.g., ocean warming, increase in frequency and severity of extreme events, introduction and spread of invasive species) and local (e.g., physical disturbances, eutrophication, and sedimentation) anthropogenic stressors continue to be the main causes behind the ongoing global decline of seagrass meadows (Orth et al., 2006; Waycott et al., 2009). © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Winters, G., Teichberg, M., Reuter, H., Viana, I. G., & Willette, D. A. Editorial: seagrasses under times of change. Frontiers in Plant Science, 13, (2022): 870478, https://doi.org/10.3389/fpls.2022.870478.

Building a global ecosystem research infrastructure to address global grand challenges for macrosystem ecology Loescher, Henry W.; Vargas, Rodrigo; Mirtl, Michael; Morris, Beryl; Pauw, Johan C.; Yu, Xiubo; Kutsch, Werner; Mabee, Paula M.; Tang, Jianwu; Ruddell, Benjamin L.; Pulsifer, Peter L.; Bäck, Jaana K.; Zacharias, Steffen; Grant, Mark; Feig, Gregor; Zhang, Leiming; Waldmann, Christoph; Genazzio, Melissa A. The development of several large-, “continental”-scale ecosystem research infrastructures over recent decades has provided a unique opportunity in the history of ecological science. The Global Ecosystem Research Infrastructure (GERI) is an integrated network of analogous, but independent, site-based ecosystem research infrastructures (ERI) dedicated to better understand the function and change of indicator ecosystems across global biomes. Bringing together these ERIs, harmonizing their respective data and reducing uncertainties enables broader cross-continental ecological research. It will also enhance the research community capabilities to address current and anticipate future global scale ecological challenges. Moreover, increasing the international capabilities of these ERIs goes beyond their original design intent, and is an unexpected added value of these large national investments. Here, we identify specific global grand challenge areas and research trends to advance the ecological frontiers across continents that can be addressed through the federation of these cross-continental-scale ERIs. © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Loescher, H., Vargas, R., Mirtl, M., Morris, B., Pauw, J., Yu, X., Kutsch, W., Mabee, P., Tang, J., Ruddell, B., Pulsifer, P., Bäck, J., Zacharias, S., Grant, M., Feig, G., Zheng, L., Waldmann, C., & Genazzio, M. Building a global ecosystem research infrastructure to address global grand challenges for macrosystem ecology. Earth’s Future, 10(5), (2022): e2020EF001696, https://doi.org/10.1029/2020ef001696.

Landscape genomics provides evidence of ecotypic adaptation and a barrier to gene flow at treeline for the arctic foundation species Eriophorum vaginatum0 Stunz, Elizabeth; Fetcher, Ned; Lavretsky, Philip; Mohl, Jonathon E.; Tang, Jianwu; Moody, Michael L. Global climate change has resulted in geographic range shifts of flora and fauna at a global scale. Extreme environments, like the Arctic, are seeing some of the most pronounced changes. This region covers 14% of the Earth’s land area, and while many arctic species are widespread, understanding ecotypic variation at the genomic level will be important for elucidating how range shifts will affect ecological processes. Tussock cottongrass (Eriophorum vaginatum L.) is a foundation species of the moist acidic tundra, whose potential decline due to competition from shrubs may affect ecosystem stability in the Arctic. We used double-digest Restriction Site-Associated DNA sequencing to identify genomic variation in 273 individuals of E. vaginatum from 17 sites along a latitudinal gradient in north central Alaska. These sites have been part of 30 + years of ecological research and are inclusive of a region that was part of the Beringian refugium. The data analyses included genomic population structure, demographic models, and genotype by environment association. Genome-wide SNP investigation revealed environmentally associated variation and population structure across the sampled range of E. vaginatum, including a genetic break between populations north and south of treeline. This structure is likely the result of subrefugial isolation, contemporary isolation by resistance, and adaptation. Forty-five candidate loci were identified with genotype-environment association (GEA) analyses, with most identified genes related to abiotic stress. Our results support a hypothesis of limited gene flow based on spatial and environmental factors for E. vaginatum, which in combination with life history traits could limit range expansion of southern ecotypes northward as the tundra warms. This has implications for lower competitive attributes of northern plants of this foundation species likely resulting in changes in ecosystem productivity. © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Stunz, E., Fetcher, N., Lavretsky, P., Mohl, J., Tang, J., & Moody, M. Landscape genomics provides evidence of ecotypic adaptation and a barrier to gene flow at treeline for the arctic foundation species Eriophorum vaginatum. Frontiers in Plant Science, 13, (2022): 860439, https://doi.org/10.3389/fpls.2022.860439.

Particle fluxes in submarine canyons along a sediment-starved continental margin and in the adjacent open slope and basin in the SW Mediterranean Sea Tarrés, Marta; Cerdà-Domènech, Marc; Pedrosa-Pamies, Rut; Rumín-Caparrós, Aitor; Calafat, Antoni; Canals, Miquel; Sanchez-Vidal, Anna Investigating the transfer of particulate matter from the continental shelf to the deep basin is critical to understand the functioning of deep sea ecosystems. In this paper we present novel results on the temporal variability of particle fluxes to the deep in three physiographic domains of a 240 km long margin segment and nearby basin off Murcia and Almeria provinces in the SW Mediterranean Sea, which are submarine canyons forming a rather diverse set (namely Escombreras, Garrucha-Almanzora and Almeria), the adjacent open slope and the deep basin. This margin is located off one of the driest regions in Europe and, therefore, its study may help understanding how mainland aridity translates into the export of particles to deep margin environments. Five mooring lines equipped with currentmeters, turbidity-meters and sediment traps were deployed for one entire annual cycle, from March 2015 to March 2016. We combine oceanographic, hydrological and meteorological data with grain size and bulk elemental data (organic carbon, opal, CaCO3, lithogenic) from the collected sinking particles to understand what drives particle transfers in such an under-studied setting, and to quantify the resulting fluxes and assess their spatio-temporal variability. Weighted total mass fluxes in canyons range from 1.64 g m−2 d−1 in Almeria Canyon to 7.33 g m−2 d−1 in Garrucha-Almanzora Canyon system, which are rather low values compared to other submarine canyons in the Western Mediterranean Sea. This results from the absence of extreme wind-storm events during the investigated time period combined with the reduced sediment input to the inner shelf by river systems in the study area. Our results also show that wind-storms are the main trigger for off-shelf particle transport to the deep margin, both within submarine canyons and over the open slope. The most significant transfer period is associated to a set of north-eastern storms in early spring 2015, when the off-shelf transport likely was promoted by storm-induced downwelling. However, the prevailing oceanographic conditions restricts the advection of water down the canyon heads to a few hundred meters, thus promoting a bottom-detached transport of particles seaward. Overall physiography, canyon head incision into the continental shelf and the distance of the canyon head to the shoreline (e.g. very short in Garrucha Canyon) play a key role in particle trapping capability and, therefore, in easing downslope particle transport. Further, bottom trawling activities around the Garrucha-Almanzora Canyon system, feed a nepheloid layer at depths in excess of 400 m, subsequently enhancing particle fluxes throughout the study period. In contrast, maximum particle fluxes in the deep basin respond to seasonal phytoplankton blooms. Our study shows that particle export from the shallow inner margin to the deep outer margin in sediment-starved settings, even if limited, does occur as dominated by atmosphere and ocean driven short-lived events. However, that export does not reach too far as at several tens of kilometres from the shelf edge advective fluxes are replaced by vertical ones impelled by phytoplankton dynamics. © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Tarrés, M., Cerdà-Domènech, M., Pedrosa-Pàmies, R., Rumín-Caparrós, A., Calafat, A., Canals, M., & Sanchez-Vidal, A. Particle fluxes in submarine canyons along a sediment-starved continental margin and in the adjacent open slope and basin in the SW Mediterranean Sea. Progress in Oceanography, 203, (2022): 102783, https://doi.org/10.1016/j.pocean.2022.102783.

Variation in sediment and seagrass characteristics reflect multiple stressors along a nitrogen-enrichment gradient in a New England lagoon Haviland, Katherine Ann; Howarth, Robert W.; Marino, Roxanne; Hayn, Melanie We examined concentrations of organic carbon, dissolved sulfides, total sediment sulfur, and stable sulfur isotope ratios in seagrass leaf tissues across a nitrogen-enrichment gradient in a coastal marine ecosystem (Cape Cod, Massachusetts) in 2007–2010 and 2017–2019. We also measured seagrass aboveground and belowground biomass, epibiota biomass, and leaf chlorophyll content. Seagrasses were present at all sites in the former period but were lost at our most nitrogen-impacted site (Snug Harbor) by 2011. In 2007–2010, sediment organic carbon and dissolved sulfides were highest in Snug Harbor and decreased along the gradient; leaf tissues depleted in 34S also indicated higher sulfide intrusion into seagrass tissues in more eutrophic areas. By 2017–2019, sediment organic carbon and pore-water soluble sulfides had decreased in Snug Harbor, but had increased at the intermediate site, to levels found at the most impacted site prior to the seagrass die-off. Again, leaf tissue 34S depletion reflected this pattern, indicating seagrasses were exposed to the highest sulfides at the intermediate site. The decreases in sediment organic carbon and soluble sulfides in Snug Harbor years after the loss of the seagrasses illustrate a feedback between high organic matter in seagrass beds and increasing stressors like elevated soluble sulfides in nutrient-enriched systems. We found significant relationships between sediment conditions and seagrass responses, including greater aboveground to belowground biomass ratios, epibiota biomass, and 34S-depleted leaves at sites with high pore-water sulfide and highly organic sediments. Our research suggests that the reduction of anthropogenic nitrogen entering the harbor is necessary for improving sediment quality and preventing seagrass mortality. © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Haviland, K. A., Howarth, R. W., Marino, R., & Hayn, M. Variation in sediment and seagrass characteristics reflect multiple stressors along a nitrogen-enrichment gradient in a New England lagoon. Limnology and Oceanography, 67, (2022): 660-667, https://doi.org/10.1002/lno.12025.

Editorial: microbial communities and metabolisms involved in the degradation of cellular and extracellular organic biopolymers Ruff, S. Emil Most organic matter on Earth occurs in the form of macromolecules and complex biopolymers, which include the building blocks of every organism. Plant, animal, fungal, and microbial cells largely consist of macromolecules belonging to four compound classes: proteins, polysaccharides, nucleic acids, and lipids (Figure 1). The percentage of these compounds per dry weight can vary greatly between lineages, but also between individuals of the same species or developmental stages of the same organism. Living and lysing cells release a substantial quantity and variety of macromolecules to the environment. These compounds often contain nitrogen, phosphorus, and sulfur, in addition to carbon, and are thus ideal food sources for heterotrophic organisms. Although the degradation of biopolymers and macromolecules has received considerable attention, many knowledge gaps remain, particularly in very complex ecosystems such as soils and sediments. © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ruff, S. E. Editorial: microbial communities and metabolisms involved in the degradation of cellular and extracellular organic biopolymers. Frontiers in Microbiology, 12, (2022): 802619, https://doi.org/10.3389/fmicb.2021.802619.

Common environmental pollutants negatively affect development and regeneration in the sea anemone Nematostella vectensis holobiont Klein, Sylvia; Frazier, Victoria; Readdean, Timothy; Lucas, Emily; Diaz-Jimenez, Erica P.; Sogin, Mitchell L.; Ruff, S. Emil; Echeverri, Karen The anthozoan sea anemone Nematostella vectensis belongs to the phylum of cnidarians which also includes jellyfish and corals. Nematostella are native to United States East Coast marsh lands, where they constantly adapt to changes in salinity, temperature, oxygen concentration and pH. Its natural ability to continually acclimate to changing environments coupled with its genetic tractability render Nematostella a powerful model organism in which to study the effects of common pollutants on the natural development of these animals. Potassium nitrate, commonly used in fertilizers, and Phthalates, a component of plastics are frequent environmental stressors found in coastal and marsh waters. Here we present data showing how early exposure to these pollutants lead to dramatic defects in development of the embryos and eventual mortality possibly due to defects in feeding ability. Additionally, we examined the microbiome of the animals and identified shifts in the microbial community that correlated with the type of water that was used to grow the animals, and with their exposure to pollutants. © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Klein, S., Frazier, V., Readdean, T., Lucas, E., Diaz-Jimenez, E. P., Sogin, M., Ruff, E. S., & Echeverri, K. Common environmental pollutants negatively affect development and regeneration in the sea anemone Nematostella vectensis holobiont. Frontiers in Ecology and Evolution, 9, (2021): 786037, https://doi.org/10.3389/fevo.2021.786037.

Modeling nitrous oxide emissions from large-scale intensive cropping systems in the southern Amazon Costa, Ciniro; Galford, Gillian L.; Coe, Michael T.; Macedo, Marcia N.; Jankowski, KathiJo; O’Connell, Christine; Neill, Christopher Nitrogen (N) fertilizer use is rapidly intensifying on tropical croplands and has the potential to increase emissions of the greenhouse gas, nitrous oxide (N2O). Since about 2005 Mato Grosso (MT), Brazil has shifted from single-cropped soybeans to double-cropping soybeans with maize, and now produces 1.5% of the world's maize. This production shift required an increase in N fertilization, but the effects on N2O emissions are poorly known. We calibrated the process-oriented biogeochemical DeNitrification-DeComposition (DNDC) model to simulate N2O emissions and crop production from soybean and soybean-maize cropping systems in MT. After model validation with field measurements and adjustments for hydrological properties of tropical soils, regional simulations suggested N2O emissions from soybean-maize cropland increased almost fourfold during 2001–2010, from 1.1 ± 1.1 to 4.1 ± 3.2 Gg 1014 N-N2O. Model sensitivity tests showed that emissions were spatially and seasonably variable and especially sensitive to soil bulk density and carbon content. Meeting future demand for maize using current soybean area in MT might require either (a) intensifying 3.0 million ha of existing single soybean to soybean-maize or (b) increasing N fertilization to ~180 kg N ha−1 on existing 2.3 million ha of soybean-maize area. The latter strategy would release ~35% more N2O than the first. Our modifications of the DNDC model will improve estimates of N2O emissions from agricultural production in MT and other tropical areas, but narrowing model uncertainty will depend on more detailed field measurements and spatial data on soil and cropping management. © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Costa Jr, C., Galford, G. L., Coe, M. T., Macedo, M., Jankowski, K., O’Connell, C., & Neill, C. Modeling nitrous oxide emissions from large-scale intensive cropping systems in the southern Amazon. Frontiers in Sustainable Food Systems, 5, (2021): 701416. https://doi.org/10.3389/fsufs.2021.701416.

Sporadic P limitation constrains microbial growth and facilitates SOM accumulation in the stoichiometrically coupled, acclimating microbe-plant-soil model Pold, Grace; Kwiatkowski, Bonnie L.; Rastetter, Edward B.; Sistla, Seeta A. Requirements for biomass carbon (C), nitrogen (N), and phosphorus (P) constrain organism growth and are important agents for structuring ecosystems. Arctic tundra habitats are strongly nutrient limited as decomposition and recycling of nutrients are slowed by low temperature. Modeling interactions among these elemental cycles affords an opportunity to explore how disturbances such as climate change might differentially affect these nutrient cycles. Here we introduce a C–N–P-coupled version of the Stoichiometrically Coupled Acclimating Microbe-Plant-Soil (SCAMPS) model, “SCAMPS-CNP”, and a corresponding modified CN-only model, “SCAMPS-CN”. We compared how SCAMPS-CNP and the modified SCAMPS-CN models project a moderate (RCP 6.0) air warming scenario will impact tussock tundra nutrient availability and ecosystem C stocks. SCAMPS-CNP was characterized by larger SOM and smaller organism C stocks compared to SCAMPS-CN, and a greater reduction in ecosystem C stocks under warming. This difference can largely be attributed to a smaller microbial biomass in the CNP model, which, instead of being driven by direct costs of P acquisition, was driven by variable resource limitation due to asynchronous C, N, and P availability and demand. Warming facilitated a greater relative increase in plant and microbial biomass in SCAMPS-CNP, however, facilitated by increased extracellular enzyme pools and activity, which more than offset the metabolic costs associated with their production. Although the microbial community was able to flexibly adapt its stoichiometry and become more bacteria-like (N-rich) in both models, its stoichiometry deviated further from its target value in the CNP model because of the need to balance cellular NP ratio. Our results indicate that seasonality and asynchrony in resources affect predicted changes in ecosystem C storage under warming in these models, and therefore build on a growing body of literature indicating stoichiometry should be considered in carbon cycling projections. © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Pold, G., Kwiatkowski, B. L., Rastetter, E. B., & Sistla, S. A. Sporadic P limitation constrains microbial growth and facilitates SOM accumulation in the stoichiometrically coupled, acclimating microbe-plant-soil model. Soil Biology & Biochemistry, 165, (2022): 108489, https://doi.org/10.1016/j.soilbio.2021.108489.

Model responses to CO(2) and warming are underestimated without explicit representation of Arctic small-mammal grazing Rastetter, Edward B.; Griffin, Kevin L.; Rowe, Rebecca J.; Gough, Laura; McLaren, Jennie; Boelman, Natalie We use a simple model of coupled carbon and nitrogen cycles in terrestrial ecosystems to examine how “explicitly representing grazers” vs. “having grazer effects implicitly aggregated in with other biogeochemical processes in the model” alters predicted responses to elevated carbon dioxide and warming. The aggregated approach can affect model predictions because grazer-mediated processes can respond differently to changes in climate compared with the processes with which they are typically aggregated. We use small-mammal grazers in a tundra as an example and find that the typical three-to-four-year cycling frequency is too fast for the effects of cycle peaks and troughs to be fully manifested in the ecosystem biogeochemistry. We conclude that implicitly aggregating the effects of small-mammal grazers with other processes results in an underestimation of ecosystem response to climate change, relative to estimations in which the grazer effects are explicitly represented. The magnitude of this underestimation increases with grazer density. We therefore recommend that grazing effects be incorporated explicitly when applying models of ecosystem response to global change. © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Rastetter, E. B., Griffin, K. L., Rowe, R. J., Gough, L., McLaren, J. R., & Boelman, N. T. Model responses to CO(2) and warming are underestimated without explicit representation of Arctic small-mammal grazing. Ecological Applications, (2021): e02478, https://doi.org/10.1002/eap.2478.

Warming effects on arctic tundra biogeochemistry are limited but habitat-dependent: a meta-analysis Pold, Grace; Baillargeon, Natalie; Lepe, Adan; Rastetter, Edward B.; Sistla, Seeta A. Arctic tundra consists of diverse habitats that differ in dominant vegetation, soil moisture regimes, and relative importance of organic vs. inorganic nutrient cycling. The Arctic is also the most rapidly warming global area, with winter warming dominating. This warming is expected to have dramatic effects on tundra carbon and nutrient dynamics. We completed a meta-analysis of 166 experimental warming study papers to evaluate the hypotheses that warming changes tundra biogeochemical cycles in a habitat- and seasonally specific manner and that the carbon (C), nitrogen (N), and phosphorus (P) cycles will be differentially accelerated, leading to decoupling of elemental cycles. We found that nutrient availability and plant leaf stoichiometry responses to experimental warming were variable and overall weak, but that both gross primary productivity and the plant C pool tended to increase with growing season warming. The effects of winter warming on C fluxes did not extend into the growing season. Overall, although warming led to more consistent increases in C fluxes compared to N or P fluxes, evidence for decoupling of biogeochemical cycles is weak and any effect appears limited to heath habitats. However, data on many habitats are too sparse to be able to generalize how warming might decouple biogeochemical cycles, and too few year-round warming studies exist to ascertain whether the season under which warming occurs alters how ecosystems respond to warming. Coordinated field campaigns are necessary to more robustly document tundra habitat-specific responses to realistic climate warming scenarios in order to better understand the mechanisms driving this heterogeneity and identify the tundra habitats, communities, and soil pools most susceptible to warming. © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Pold, G., Baillargeon, N., Lepe, A., Rastetter, E. B., & Sistla, S. A. Warming effects on arctic tundra biogeochemistry are limited but habitat-dependent: a meta-analysis. Ecosphere, 12(10), (2021): e03777, https://doi.org/10.1002/ecs2.3777.

The transcriptional response of soil bacteria to long-term warming and short-term seasonal fluctuations in a terrestrial forest Chowdhury, Priyanka Roy; Golas, Stefan M.; Alteio, Lauren V.; Stevens, Joshua T. E.; Billings, Andrew F.; Blanchard, Jeffrey L.; Melillo, Jerry M.; DeAngelis, Kristen M. Terrestrial ecosystems are an important carbon store, and this carbon is vulnerable to microbial degradation with climate warming. After 30 years of experimental warming, carbon stocks in a temperate mixed deciduous forest were observed to be reduced by 30% in the heated plots relative to the controls. In addition, soil respiration was seasonal, as was the warming treatment effect. We therefore hypothesized that long-term warming will have higher expressions of genes related to carbohydrate and lipid metabolism due to increased utilization of recalcitrant carbon pools compared to controls. Because of the seasonal effect of soil respiration and the warming treatment, we further hypothesized that these patterns will be seasonal. We used RNA sequencing to show how the microbial community responds to long-term warming (~30 years) in Harvard Forest, MA. Total RNA was extracted from mineral and organic soil types from two treatment plots (+5°C heated and ambient control), at two time points (June and October) and sequenced using Illumina NextSeq technology. Treatment had a larger effect size on KEGG annotated transcripts than on CAZymes, while soil types more strongly affected CAZymes than KEGG annotated transcripts, though effect sizes overall were small. Although, warming showed a small effect on overall CAZymes expression, several carbohydrate-associated enzymes showed increased expression in heated soils (~68% of all differentially expressed transcripts). Further, exploratory analysis using an unconstrained method showed increased abundances of enzymes related to polysaccharide and lipid metabolism and decomposition in heated soils. Compared to long-term warming, we detected a relatively small effect of seasonal variation on community gene expression. Together, these results indicate that the higher carbohydrate degrading potential of bacteria in heated plots can possibly accelerate a self-reinforcing carbon cycle-temperature feedback in a warming climate. © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Chowdhury, P. R., Golas, S. M., Alteio, L., Stevens, J. T. E., Billings, A. F., Blanchard, J. L., Melillo, J. M., & DeAngelis, K. M. The transcriptional response of soil bacteria to long-term warming and short-term seasonal fluctuations in a terrestrial forest. Frontiers in Microbiology, 12, (2021): 666558, https://doi.org/10.3389/fmicb.2021.666558.

Understanding the effects of climate change via disturbance on pristine arctic lakes-multitrophic level response and recovery to a 12-yr, low-level fertilization experiment Budy, Phaedra; Pennock, Casey A.; Giblin, Anne E.; Luecke, Chris; White, Daniel L.; Kling, George W. Effects of climate change-driven disturbance on lake ecosystems can be subtle; indirect effects include increased nutrient loading that could impact ecosystem function. We designed a low-level fertilization experiment to mimic persistent, climate change-driven disturbances (deeper thaw, greater weathering, or thermokarst failure) delivering nutrients to arctic lakes. We measured responses of pelagic trophic levels over 12 yr in a fertilized deep lake with fish and a shallow fishless lake, compared to paired reference lakes, and monitored recovery for 6 yr. Relative to prefertilization in the deep lake, we observed a maximum pelagic response in chl a (+201%), dissolved oxygen (DO, −43%), and zooplankton biomass (+88%) during the fertilization period (2001–2012). Other responses to fertilization, such as water transparency and fish relative abundance, were delayed, but both ultimately declined. Phyto- and zooplankton biomass and community composition shifted with fertilization. The effects of fertilization were less pronounced in the paired shallow lakes, because of a natural thermokarst failure likely impacting the reference lake. In the deep lake there was (a) moderate resistance to change in ecosystem functions at all trophic levels, (b) eventual responses were often nonlinear, and (c) postfertilization recovery (return) times were most rapid at the base of the food web (2–4 yr) while higher trophic levels failed to recover after 6 yr. The timing and magnitude of responses to fertilization in these arctic lakes were similar to responses in other lakes, suggesting indirect effects of climate change that modify nutrient inputs may affect many lakes in the future. © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Budy, P., Pennock, C. A., Giblin, A. E., Luecke, C., White, D. L., & Kling, G. W. Understanding the effects of climate change via disturbance on pristine arctic lakes-multitrophic level response and recovery to a 12-yr, low-level fertilization experiment. Limnology and Oceanography. (2021), https://doi.org/10.1002/lno.11893.

Emerging wetlands from river diversions can sustain high denitrification rates in a Coastal Delta Upreti, Kiran; Rivera-Monroy, Victor H.; Maiti, Kanchan; Giblin, Anne E.; Geaghan, James P. It is assumed that to treat excess NO3− high soil organic matter content (%OM) is required to maintain high denitrification rates in natural or restored wetlands. However, this excess also represents a risk by increasing soil decomposition rates triggering peat collapse and wetland fragmentation. Here, we evaluated the role of %OM and temperature interactions controlling denitrification rates in eroding (Barataria Bay-BLC) and emerging (Wax Lake Delta-WLD) deltaic regions in coastal Louisiana using the isotope pairing (IPT) and N2:Ar techniques. We also assessed differences between total (direct denitrification + coupled nitrification-denitrification) and net (total denitrification minus nitrogen fixation) denitrification rates in benthic and wetland habitats with contrasting %OM and bulk density (BD). Sediment (benthic) and soil (wetland) cores were collected during summer, spring, and winter (2015–2016) and incubated at close to in-situ temperatures (30°C, 20°C, and 10°C, respectively). Denitrification rates were linearly correlated with temperature; maximum mean rates ranged from 40.1–124.1 μmol m−2 h−1 in the summer with lower rates (<26.2 ± 5.3 μmol m−2 h−1) in the winter seasons. Direct denitrification was higher than coupled denitrification in all seasons. Denitrification rates were higher in WLD despite lower %OM, lower total N concentration, and higher BD in wetland soils. Therefore, in environments with low carbon availability, high denitrification rates can be sustained as long as NO3− concentrations are high (>30 μM) and water temperature is >10°C. In coastal Louisiana, substrates under these regimes are represented by emergent supra-tidal flats or land created by sediment diversions under oligohaline conditions (<1 ppt). Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Biogeosciences 126(5), (2021): e2020JG006217, https://doi.org/10.1029/2020JG006217.