A sulfate-reducing bacterial genus, Desulfosediminicola gen. nov., comprising two novel species cultivated from tidal-flat sediments

Tidal-flat sediments harbor a diverse array of sulfate-reducing bacteria. To isolate novel sulfate-reducing bacteria and determine their abundance, a tidal-flat sediment sample collected off Ganghwa Island (Korea) was investigated using cultivation-based and culture-independent approaches. Two Gram-stain-negative, strictly anaerobic, rod-shaped, sulfate-reducing bacteria, designated IMCC35004T and IMCC35005T, were isolated from the sample. The two strains reduced sulfate, sulfite, elemental sulfur, thiosulfate, Fe(III) citrate, and Mn(IV) oxide by utilizing several carbon sources, including acetate. The 16S rRNA gene amplicon sequencing revealed that the tidal-flat sediment contained diverse members of the phylum Desulfobacterota, and the phylotypes related to IMCC35004T and IMCC35005T were < 1%. The two strains shared 97.6% similarity in 16S rRNA gene sequence and were closely related to Desulfopila aestuarii DSM 18488T (96.1–96.5%). The average nucleotide identity, level of digital DNA–DNA hybridization, average amino acid identity, and percentages of conserved proteins determined analyzing the whole-genome sequences, as well as the chemotaxonomic data showed that the two strains belong to two novel species of a novel genus. Additionally, genes related to dissimilatory sulfate reduction were detected in the genomes of the two strains. Unlike the genera Desulfopila and Desulfotalea, IMCC35004T and IMCC35005T contained menaquinone-5 as the major respiratory quinone. Collectively, IMCC35004T and IMCC35005T were concluded to represent two novel species of a novel genus within the family Desulfocapsaceae, for which the names Desulfosediminicola ganghwensis gen. nov., sp. nov. (IMCC35004T = KCTC 15826T = NBRC 114003T) and Desulfosediminicola flagellatus sp. nov. (IMCC35005T = KCTC 15827T = NBRC 114004T) are proposed.

Distribution and Sources of Organic Carbon in Surface Intertidal Sediments of the Rudong Coast, Jiangsu Province, China

In this study, total organic carbon (TOC), total nitrogen (TN), and stable carbon isotopes (δ13C) were measured in surface intertidal saltmarsh and bare tidal flat sediments along the Rudong coast. The distribution and sources of organic carbon were examined under different depositional environments based on C/N ratios and a two-terminal mixing model. The results showed that the average TOC content of the vegetated saltmarsh sediments, bare tidal flat areas near vegetation (BF1), and bare tidal flat areas far from vegetation (BF2) were 4.05, 2.72, and 1.22 mg/g, respectively. The mean δ13C value within the vegetated saltmarsh area was −22.37‰, and the C/N ratio was 9.3; the corresponding values in the BF1 area were −23.27‰ and 7.95, respectively; and in the BF2 area, the corresponding values were −21.91‰ and 5.36, respectively. These C/N ratios reflect an increasing marine contribution with distance from the vegetated zone. Combined with the two-terminal mixing model, the organic carbon in the vegetated saltmarsh sediments was dominated by terrestrial sources, while the bare tidal flat sediments were more influenced by marine sources, and the bare tidal flat sediments nearer to the vegetated zone (BF1) were influenced by a combination of vegetation, marine sources, and other terrestrial factors.

The Periodic Response of Tidal Flat Sediments to Runoff Variation of Upstream Main River: A Case Study in the Liaohe Estuary Wetland, China

(1) Background: To reveal the intrinsic relationship between the tidal flat sediments in an estuary wetland and the runoff from the upstream river. This research was conducted in the tidal flats of the Liaohe estuary wetland. (2) Methods: The 137Cs and 210Pb dating technique was used to reconstruct the time correspondence between tidal flat sediments and runoff, and the periodic response was explored between the changes in the tidal flat sediments and runoff based on the spectrum analysis method. (3) Results: The average sedimentation rate in the tidal flat was 2.24 cm·year−1 during the past 50 years. The amount of fine sediment particles deposited on the estuary tidal flat was directly related to the amount of sediments transported by the river and inversely proportional to the ability of rivers to transport fine matter. The high frequency reproduction cycle of 14–15 years in the flood season flow and 5–6 years in the annual sediment discharge of the Liaohe River correspond to the high and low frequency reproduction cycles of the median size of sediments in Liaohe estuarine wetland tidal flats. (4) Conclusions: The research clarified the hydrological constraints of the action law between Liaohe River runoff and the estuarine sediments. The periodic response between Liaohe River runoff and the sediment was established.