The rewetting of drained peatlands alters peat geochemistry and often leads
to sustained elevated methane emission. Although this methane is produced
entirely by microbial activity, the distribution ...and abundance of
methane-cycling microbes in rewetted peatlands, especially in fens, is rarely
described. In this study, we compare the community composition and abundance
of methane-cycling microbes in relation to peat porewater geochemistry in two
rewetted fens in northeastern Germany, a coastal brackish fen and a
freshwater riparian fen, with known high methane fluxes. We utilized 16S rRNA
high-throughput sequencing and quantitative polymerase chain reaction (qPCR) on 16S
rRNA, mcrA, and pmoA genes to determine microbial community
composition and the abundance of total bacteria, methanogens, and
methanotrophs. Electrical conductivity (EC) was more than 3 times higher in
the coastal fen than in the riparian fen, averaging 5.3 and 1.5 mS cm−1,
respectively. Porewater concentrations of terminal electron acceptors (TEAs) varied
within and among the fens. This was also reflected in similarly high intra-
and inter-site variations of microbial community composition. Despite these
differences in environmental conditions and electron acceptor availability,
we found a low abundance of methanotrophs and a high abundance of
methanogens, represented in particular by Methanosaetaceae, in both
fens. This suggests that rapid (re)establishment of methanogens and slow
(re)establishment of methanotrophs contributes to prolonged increased methane
emissions following rewetting.
There have been widespread attempts to rewet peatlands in Europe and elsewhere in the world to restore their unique biodiversity as well as their important function as nutrient and carbon sinks. ...However, changes in hydrological regime and therefore oxygen availability likely alter the abundance of enzyme-inhibiting polyphenolic compounds, which have been suggested as a "latch" preventing large amounts of carbon from being released into the atmosphere by microbial mineralization. In recent years, a variety of factors have been identified that appear to weaken that latch including not only oxygen, but also pH. In minerotrophic fens, it is unknown if long-term peat mineralization during decades of drainage and intense agricultural use causes an enrichment or a decline of enzyme-inhibiting polyphenols. To address this, we collected peat samples and fresh roots of dominating plants (i.e., the peat parent material) from the upper 20 cm peat layer in 5 rewetted and 6 natural fens and quantified total phenolic content as well as hydrolysable and condensed tannins. Polyphenols from less decomposed peat and living roots served partly as an internal standard for polyphenol analysis and to run enzyme inhibition tests. As hypothesized, we found the polyphenol content in highly decomposed peat to be 8 times lower than in less decomposed peat, while condensed tannin content was 50 times lower in highly degraded peat. In addition, plant tissue polyphenol contents differed strongly between peat-forming plant species, with the highest amount found in roots of Carex appropinquata at 450 mg g-1 dry mass, and lowest in Sphagnum spp. at 39 mg g-1 dry mass: a 10-fold difference. Despite large and clear differences in peat and porewater chemistry between natural and rewetted sites, enzyme activities determined with Fluorescein diacetate (FDA) hydrolysis and peat degradation were not significantly correlated, indicating no simple linear relationship between polyphenol content and microbial activity. Still, samples with low contents of polyphenols and condensed tannins showed the highest microbial activities as measured with FDA.
Coastal zones connect terrestrial and marine ecosystems forming a unique environment that is under increasing anthropogenic pressure. Rising sea levels, sinking coasts, and changing precipitation ...patterns modify hydrodynamic gradients and may enhance sea-land exchange processes in both tidal and non-tidal systems. Furthermore, the removal of flood protection structures as restoration measure contributes locally to the changing coastlines. A detailed understanding of the ecosystem functioning of coastal zones and the interactions between connected terrestrial and marine ecosystems is still lacking. Here, we propose an interdisciplinary approach to the investigation of interactions between land and sea at shallow coasts, and discuss the advantages and the first results provided by this approach as applied by the research training group Baltic TRANSCOAST. A low-lying fen peat site including the offshore shallow sea area on the southern Baltic Sea coast has been chosen as a model system to quantify hydrophysical, biogeochemical, sedimentological, and biological processes across the land-sea interface. Recently introduced rewetting measures might have enhanced submarine groundwater discharge as indicated by distinct patterns of salinity gradients in the near shore sediments, making the coastal waters in front of the study site a mixing zone of fresh- and brackish water. High nutrient loadings, dissolved inorganic carbon, and dissolved organic matter originating from the degraded peat may affect micro- and macro-phytobenthos, with the impact propagating to higher trophic levels. The terrestrial part of the study site is subject to periodic brackish water intrusion caused by occasional flooding, which has altered the hydraulic and biogeochemical properties of the prevailing peat soils. The stable salinity distribution in the main part of the peatland reveals the legacy of flooding events. Generally, elevated sulfate concentrations are assumed to influence greenhouse gas emissions, mainly by inhibiting methane production, yet our investigations indicate complex interactions between the different biogeochemical element cycles (e.g. carbon and sulfur) caused by connected hydrological pathways. In conclusion, sea-land interactions are far reaching, occurring on either side of the interface, and can only be understood when both long-term and event-based patterns and different spatial scales are taken into account in interdisciplinary research that involves marine and terrestrial expertise.
With increasing global temperatures, it remains unclear, how seedling emergence and survival will be affected in highly dynamic ecosystems like salt marshes. Our study combines passive and active ...warming treatments with the natural inundation dynamics of salt marshes. We studied the effects of active soil and passive air warming (ambient temperature, + 1.5°C and + 3.0°C) on seedling numbers of different species in three salt marsh zones (pioneer zone, low marsh, and high marsh) and on seedling survival (lifespan), seedling diversity and species richness in two salt marsh zones (low marsh and high marsh) in situ. We found a significant influence of warming on Shannon diversity at two dates, but we found no significant effects of warming on seedling number and survival. However, we found trends, which differed between zones. In the pioneer zone, seedling numbers were slightly higher in the warming treatments than in the ambient treatment from April to June. Whereas, in the high marsh, seedling numbers decreased more in the warming treatments during the same period. The median lifespan was slightly reduced under warming treatments. We conclude warming might have increased drought stress for seedlings in the high marsh, which led to the trend of lower seedling numbers and shorter survival times. Seedling number decreased with elevation, which could be attributed to both species‐specific strategies and differences in available space. Median survival differed significantly between species, which we assume is due to differing life‐history traits like seed size and if the species are annual or perennial.
Organic carbon sequestration in salt marsh soils is a function of factors that influence both spatial variability and chemical stability of accumulating carbon. Refractory carbon (slowly decomposed) ...may be the most important in terms of long-term sequestration and is widely referred to in models of carbon storage; however, little information exists about the quantity and variability of refractory carbon accumulation in marshes. In this study, total (CT), labile (CL) and refractory (CR) organic carbon accumulation rates were measured for Spartina alterniflora-dominated marshes representing different geomorphological settings with a range of vertical accretion rates. Three 50-cm long cores were collected in each of three marshes in Barnegat Bay and three marshes in Delaware Estuary, USA. Rates of C accumulation were calculated using Cesium-137 dating and the relative stability of soil organic carbon was quantified using acid-hydrolysis. CT accumulation ranged over fourfold among marshes from 72 to 346 g m−2 yr−1. CT and CL accumulation increased with increasing mineral sediment accumulation, while CR accumulation was uniform across cores averaging 78 ± 5 g m−2 yr−1. Similar rates of CR accumulation across marsh areas with different accretion and mineral sediment accumulation rates was associated with a decline in the CR:CL density ratio as mineral volume increased. Our results suggest that carbon accumulation is higher in salt marshes with higher mineral sedimentation due, primarily, to the burial of labile carbon, and that there is a limit on the rate of chemically recalcitrant carbon accumulation in marsh soils.
Salt marshes are important hotspots of long-term belowground carbon (C) storage, where plant biomass and allochthonous C can be preserved in the soil for thousands of years. However, C accumulation ...rates, as well as the sources of C, may differ depending on environmental conditions influencing plant productivity, allochthonous C deposition, and C preservation. For this study, we examined the relationship between belowground root growth, turnover, decay, above- and belowground biomass, and previously reported longer-term rates of total, labile, and refractory organic C accumulation and accretion in Spartina alterniflora-dominated marshes across two mid-Atlantic, US estuaries. Tidal range, long-term rates of mineral sedimentation, C accumulation, and accretion were higher and salinities were lower in marshes of the coastal plain estuary (Delaware Bay) than in the coastal lagoon (Barnegat Bay). We expected that the conditions promoting high rates of C accumulation would also promote high plant productivity and greater biomass. We further tested the influence of environmental conditions on belowground growth (roots + rhizomes), decomposition, and biomass of S. alterniflora. The relationship between plant biomass and C accumulation rate differed between estuaries. In the sediment-limited coastal lagoon, rates of total, labile, and refractory organic C accumulation were directly and positively related to above- and belowground biomass. Here, less flooding and a higher mineral sedimentation rate promoted greater above- and belowground biomass and, in turn, higher soil C accumulation and accretion rates. In the coastal plain estuary, the C accumulation rate was related only to aboveground biomass, which was positively related to the rate of labile C accumulation. Soil profiles indicated that live root and rhizome biomass was positively associated with labile C density for most marshes, yet high labile C densities below the live root zone and in marshes with high mineral sedimentation rates and low biomass signify the potential contribution of allochthonous C and the preservation of labile C. Overall, our findings illustrate the importance of sediment supply to marshes both for promoting positive plant-C accumulation-accretion feedbacks in geomorphic settings where mineral sediment is limiting and for promoting allochthonous inputs and preservation of labile C leading to high C accumulation and accretion rates in geomorphic settings where sediment supply is abundant.
Both the frequency and intensity of drought events are expected to increase, with unresolved alterations to peatland methane cycling and the involved microbial communities. While existing studies ...have assessed drought effects via experimental approaches under controlled conditions, to our knowledge, no studies have examined the in-situ effects of natural drought in restored temperate fens. In this study, we used quantitative polymerase chain reaction (qPCR) and high throughput 16S rRNA gene amplicon sequencing of DNA and complementary DNA (cDNA) to determine the abundances and community structure of total and putatively active microbial communities following the 2018 European summer drought. Together with geochemical and methane flux data, we compared these results to a non-drought reference dataset. During drought, water level and methane flux rates decreased to a new recent minimum in both fens. This corresponded with pronounced shifts in porewater geochemistry. Microbial community composition in the drought year differed markedly, and was characterized by a greater relative and total abundance of aerobic methanotrophs, and, in one of the two sites, by a decrease in total methanogen abundance. In contrast to the non-drought reference years, type I methanotrophs were clearly more dominant than type II methanotrophs in both fens. cDNA sequencing confirmed the activity of type I methanotrophs during drought, with Methylomonaceae having the highest average relative abundance of bacterial cDNA transcripts. We show that changes in microbial community dynamics, porewater geochemistry, and ecosystem methane fluxes can be substantial following natural drought in restored fens, and provide the first in-situ evidence from a natural drought which suggests type I methanotroph populations are more active than type II methanotrophs in response to drought effects. Type I methanotrophs may represent a key microbial control over methane emissions in restored temperate fens subject to natural drought.
•Drought decreased water level and ecosystem methane fluxes substantially.•Microbial community dynamics reflected drought conditions at the sites.•Methanogen gene abundances decreased in one of the two fens.•Proportion of type II methanotrophs was low and similar to a non-drought year.•Type I methanotrophs dominated the active bacterial community profile at both sites.
Multiple organ dysfunction syndrome (MODS) and the consecutive multiple organ failure (MOF) are severe and dreaded complications with a high mortality in multiple trauma patients. The aim of this ...study was to investigate the potential of the adipokines leptin, resistin, interleukin-17A and interleukin-33 as possible biomarkers in the early posttraumatic inflammatory response and for identifying severely traumatized patients at risk of developing MODS.
In total, 14 multiple trauma patients with an injury severity score (ISS) ≥ 16 as well as a control group of 14 non-multiple trauma patients were included in this study and blood samples were taken at the time points 0, 6, 24, 48 and 72 h after admission. For the trauma patients, the SIRS and Denver MOF score were determined daily. The quantitative measurement of the plasma concentrations of the adipokines was performed using ELISA.
In the statistical analysis, the multiple trauma patients showed statistically significant higher plasma concentrations of leptin, resistin, IL-17A and IL-33 compared to the control group. In addition, there was a statistically significant positive correlation between the concentrations of resistin, IL-17A and IL-33 and the corresponding SIRS scores and between the concentrations of resistin, IL-17A and IL-33 and the corresponding Denver MOF scores. Finally, ROC curve analysis revealed that the adipokines leptin and IL-17A are suitable diagnostic markers for the discrimination between multiple trauma patients with and without MOF.
Leptin and IL-17A could be suitable diagnostic markers to identify severely injured patients with a developing SIRS and MOF earlier, to adjust surgical therapy planning and intensive care.
PDF
