H2S is a small molecule known to have multiple signaling roles in animals. Recently, evidence shows that H2S also has signaling functions in plants; however, the role of H2S in invasive plants is unknown. Spartina alterniflora is a typical invasive species growing along the beaches of southern China. A physiological comparison proves that S. alterniflora is highly tolerant to salinity stress compared with the native species Cyperus malaccensis. To decipher the mechanism that enables S. alterniflora to withstand salinity stress, a chemico-proteomics analysis was performed to examine the salt stress response of the two species; an inhibitor experiment was additionally designed to investigate H2S signaling on salinity tolerance in S. alterniflora. A total of 86 proteins belonging to nine categories were identified and differentially expressed in S. alterniflora exposed to salt stress. Moreover, the expression level of enzymes responsible for the H2S biosynthesis was markedly upregulated, indicating the potential role of H2S signaling in the plant’s response to salt stress. The results suggested that salt triggered l-CD enzyme activity and induced the production of H2S, therefore upregulating expression of the antioxidants ascorbate peroxidase, superoxide dismutase, and S-nitrosoglutathione reductase, which mitigates damage from reactive nitrogen species. Additionally, H2S reduced the potassium efflux, thereby sustaining intracellular sodium/potassium ion homeostasis and enhancing S. alterniflora salt tolerance. These findings indicate that H2S plays an important role in the adaptation of S. alterniflora to saline environments, which provides greater insight into the function of H2S signaling in the adaptation of an invasive plant species.

A new member of the family Flavobacteriaceae was isolated from the biofilm of a stone at Nordstrand, a peninsula at the German North Sea shore. Phylogenetic analysis of the 16S rRNA gene sequence showed that strain ANORD1 T was most closely related to the validly described type strains Polaribacter porphyrae LNM-20 T (97.0 %) and Polaribacter reichenbachii KMM 6386 T (96.9 % 16S rRNA gene sequence similarity) and clustered with Polaribacter gangjinensis K17-16 T (96.0 %). Strain ANORD1 T was determined to be mesophilic, Gram-negative, non-motile and strictly aerobic. Optimal growth was observed at 20-30 °C, within a salinity range of 2-7 % sea salt and from pH 7-10. Like other type strains of the genus Polaribacter, ANORD1 T was tested negative for flexirubin-type pigments, while carotenoid-type pigments were detected. The DNA G+C content of strain ANORD1 T was 30.6 mol%. The sole respiratory quinone detected was menaquinone 6 (MK-6). The major fatty acids identified were C 15 : 0 , iso-C 15 : 0 , C 15 : 1 ω6c and iso-C 15 : 0 3-OH. Based on the polyphasic approach, strain ANORD1 T represents a novel species in the genus Polaribacter, with the name Polaribacter septentrionalilitoris sp. nov. being proposed. The type strain is ANORD1 T (=DSM 110039 T =NCIMB 15081 T =MTCC 12685 T ).

<p>Most research on submarine groundwater discharge (SGD) focuses on sandy beaches. Less studies have investigated environments with low hydraulic conductivity (K<sub>s</sub>) such as coastal peatlands, which are abundant along the southern Baltic Sea coast. Coastal peatlands, which have been drained for agricultural purposes, hold high quantities of carbon, nitrogen, and other compounds that could possibly be released to the sea upon rewetting of these sites. In this study, we simulated groundwater flow from a coastal rewetted fen with a peat layer extending out into the sea to understand the short– and long–term dynamics of SGD, quantify SGD water and matter fluxes, and assess the impact of a storm surge on SGD and seawater intrusion. Five-year (2016 – 2021) daily 2D numerical simulations of groundwater flow were based primarily on monitored groundwater and seawater level data and field-gathered soil hydraulic parameters. Hydraulic conductivities of geological layers were optimized against measured water levels. Manual seepage meter measurements were conducted and water samples were collected. The modeled seepage rates fitted the measured ones well. Our results reveal that SGD and seawater intrusion are highly dynamic and vary spatially and temporally. Two dominant submarine discharge areas were observed: 1) near the beach (up to ~30 m from shore) where mean seepage rates based on nodal water velocities reach up to 12.4 cm d<sup>-1</sup> with waters originating from the dune dike and recirculated seawater; 2) seeps from the aquifer at about 60 m distance from the coast with discharge rates of 1.1 cm d<sup>-1</sup> on average. Mean seepage rates from the discharge areas are comparable to other wetland and sandy environments. The low K<sub>s</sub> of the peat layer limits water exchange between the peatland and the Baltic Sea to these regions. The groundwater-seawater interface below the dune moves between the beach and the central dune on an hourly to weekly basis. However, the extent of the interface changes at a seasonal scale. Higher SGD fluxes occur in spring and summer while seawater intrusion increases during fall and winter, as a consequence of the seasonal variations of the peatland’s water level and the resulting hydraulic gradient. During storm surges, higher seawater intrusion fluxes are expected, while low seawater would lead to higher SGD fluxes. The mean daily net flux which represents land-derived SGD from the peatland is 0.15 m<sup>2</sup> d<sup>-1</sup> (range: -6.12 m<sup>2</sup> d<sup>-1</sup> to 1.63 m<sup>2</sup> d<sup>-1</sup>), with the highest intrusion occurring during the 2019 storm surge and the highest SGD occurring two days after the surge event. Our mean daily net flux compares well with previous studies but total SGD, which includes recirculated seawater, is likely underestimated. Nearshore carbon and nitrogen SGD concentrations are higher than ambient seawater concentrations demonstrating the potential impact of SGD on local biogeochemistry. Our findings show that SGD is an important coastal process even from low-lying and low K<sub>s</sub> coastal peatlands. We emphasize the importance of conducting more interconnection studies between peatland hydrogeology and geochemistry disciplines to better understand SGD processes in these environments.</p>

<p>There is a longstanding principle that the uppermost layer of aquatic sediment is the primary regulator of nutrient loads in the bottom water zone, pertaining to the fact that it is significantly biological in nature and thus the site of a myriad of biota-associated processes. Nevertheless, although this principle is seemingly obvious, there is unusually scant literature corroborating the impact of the uppermost sediment layer on water column nutrient fluxes, in particular soluble reactive phosphorus (SRP). It has also been theorized that in certain environments, large bacteria play a major role in phosphorus cycling in the sediment. This challenges the prevailing dogma that the control of bottom water phosphate (PO<sub>4</sub><sup>3-</sup>) is mainly attributed to the SRP flux contribution from iron (Fe) oxide-bound P in sediment or remineralisation under anoxia and warming conditions respectively. In this study, elevated temperature as well as anoxic incubation treatments were set up to demonstrate that in response to an increased level of PO<sub>4</sub><sup>3-</sup> being released under stressful conditions, the topmost bed sediment layer (TBSL) has an unmistakable impact on P sequestration and stabilisation of the bottom water PO<sub>4</sub><sup>3-</sup> fluxes. Likewise, we also show that large filamentous microorganisms residing in the TBSL were seemingly active in polyphosphate (polyP) accumulation during these stress-inducing conditions. This therefore strongly points to a new and important biological sink for the SRP flux at the benthic layer of an aquatic environment.</p>