Complete Mitochondrial Genome and Its Phylogenetic Position in Red Algae Fushitsunagia catenata from South Korea.

The mitogenome is an important tool in taxonomic and evolutionary studies. Only a few complete mitogenomes have been reported for red algae. Herein, we reported the complete mitochondrial genome sequence of Fushitsunagia catenata (Harvey) Filloramo, G.V. and Saunders, G.W. 2016, a monospecific genus. The genome was 25,889 bp in circumference and had a strongly biased AT of 70.4%. It consisted of 2 rRNAs, 23 tRNAs, and 24 protein-coding genes (PCGs). nad5 (1986 bp) was the largest and atp9 (231 bp) was the smallest PCG. All PCGs used ATG as an initiation codon and TAA as a termination codon, except TAG, which was the termination codon used in the sdh3, rps3, and rps11 genes. The general structure and gene content of the present findings were almost identical to those of other red algae genomes, particularly those of the Rhodymeniales order. The maximum likelihood analysis showed that F. catenata was closely related to Rhodymenia pseudopalmata. The mitochondrial genome data presented in this study will enhance our understanding of evolution in Rhodophyta species.

Field experiments on chemical and biological changes of thin-layer oyster shells capping sediments in dense aquaculture area.

Thin-layer oyster shell capping has been proposed as a method for improving contaminated coastal environments. Field experiments were conducted to investigate the effects of oyster shell capping on nutrient concentrations, microorganisms, and macrobenthic communities. The concentration of PO4-Pin the experimental area decreased by approximately 38% more than in the control, due to phosphorus fixation of oyster shells and the presence of Proteobacteria. Ammonia-oxidizing bacteria such as the order Pirellulales (phylum Planctomycetes) were related to the low ratio of NH3-N found in dissolved inorganic nitrogen in the experimental area, indicating nitrification promotion. The reduction in annular benthic organisms observed in the experimental area indicates a decline in sediment organic matter, which could potentially mitigate eutrophication. Oyster shell capping was confirmed to be an effective material for restoring coastal sediments by improving their chemical and biological properties.

Physicochemical effects of calcium on suppression of coastal sediment resuspension.

The coastal in-situ capping method can sequester contaminated sediment and suppress sediment resuspension. Few studies have investigated the suppression of sediment resuspension induced by calcium eluted from in-situ capping materials. We investigated the physicochemical suppression of calcium on sediment resuspension. A resuspension experiment was conducted in an annular flume using coastal sediment mixed with 0 g (CSM0), 1 g (CSM1), 5 g (CSM5), and 10 g (CSM10) of Ca(OH)2 under a stepwise increase in bottom shear stress. Calcium enhanced sediment erosion resistance, decreasing suspended sediment concentrations. Exponentially increased SSC in CSM0 and CSM1 was three times higher than that in linearly increased CSM10. Viscosity in CSM10 was approximately three times higher than that in CSM0 and CSM1. Calcium-induced cation exchange increased sediment viscosity via sediment structural rearrangement, calcium-silicate-hydrate production, and the development of larger aggregates. Consequently, calcium suppressed sediment resuspension by physiochemically changing the sediment properties.

A microcosm study of microbial community profiles during sediment remediation using pyrolyzed oyster shells.

The accumulation of organic and inorganic components in sediments leads to a deterioration in the environment and an imbalance in the coastal ecosystem. Currently, capping is the most effective technology for remediating polluted sediment and restoring ecosystems. A microcosm experiment was designed using pyrolyzed oyster shell (POS). These were mixed in with coastal sediment or added as a capping layer. The results showed that POS effectively decreased pollutants, including PO4-P and NH4-N. Metagenomics analysis was performed using 16S rRNA gene sequencing and the most abundant phyla identified in the POS treated and untreated sediments were Proteobacteria, followed by Firmicutes, Bacteroidetes, Chloroflexi, Fusobacteria, Nitrospirae, and Spirochaetes. The relative abundance of Proteobacteria members of the Class Gammaproteobacteria significantly increased, but Deltaproteobacteria gradually decreased throughout the experiment in POS-covered sediment. This suggests that the POS effectively promoted a shift from anaerobic to facultative anaerobic or aerobic microbial communities in the sediment. Dominant species of facultative anaerobic or microaerophilic bacteria from the order Chromatiales and phylum Nitrospirae were observed in the POS-covered sediment. Based on these study results, it can be concluded that POS is an effective covering material for sediment remediation and restores the microbial communities in sediments.

Seasonal Sampling of a Microbial Community in the Sediment of Geoje-Hansan Bay, Republic of Korea.

Several oyster farms are concentrated in Geoje-Hansan Bay, Republic of Korea, and there is concern about marine pollution. Hence, we monitored the sediment at this site for a year using 16S rRNA gene sequencing. The predominant phyla were Proteobacteria (69.9 to 79.1%) and Bacteroidetes (8.2 to 10.6%) in all seasons.

16S rRNA Gene Amplicon Sequencing of Contaminated Coastal Sediment Collected from the Taehwa River Estuary, South Korea.

The Taehwa River Estuary is one of the largest enclosed bays in east Korea. In order to understand the environment of the Taehwa River Estuary, the microbial diversity in the sediment of the estuary was investigated through 16S rRNA gene sequencing. The predominant phyla in all locations were Proteobacteria and Bacteroidetes.

A pilot study on remediation of muddy tidal flat using porous pile.

In order to prove that porous piles are effective in remediating muddy tidal flat sediments and increasing the biomass, field experiments were carried out at the tidal flat of a brackish river located in Hiroshima City, Japan. Porous piles with a diameter of 16cm and height of 50cm were installed in the muddy sediment that covers the sand layer of the tidal flat. After installation, concentrations of dissolved oxygen in interstitial water in and around the porous piles increased to a maximum concentration of 6mg/l due to enhancement of the groundwater flow. The increase of dissolved oxygen in the interstitial water produced a decrease in the concentration of ammonia and an increase in the individual number of benthos at the porous pile site. From these results, we concluded that the porous pile is an effective technology for remediation of muddy tidal flats.

Field experiments on remediation of coastal sediments using granulated coal ash.

Field experiments were carried out to evaluate the effect of Granulated Coal Ash (GCA) on remediation of coastal sediments in terms of removing phosphates and hydrogen sulfide. Phosphate concentrations in the sediment were kept below 0.2 mg/l after the application of GCA, whereas those in the control sites increased up to 1.0 mg/l. The concentration of hydrogen sulfide in the sediment was maintained at almost zero in the experimental sites (GCA application sites) for over one year, whereas it ranged 0.1-2.4 mg S L(-1) in control sites. Meanwhile, individual number of benthos increased in the experimental sites by several orders of magnitude compared to the control sites. The major process involved in hydrogen sulfide removal by GCA was thought to be the increase in pH, which suppresses hydrogen sulfide formation. From our findings, we concluded that GCA is an effective material for remediating organically enriched coastal sediment.