The Effect of Boundary Sea Level Height on the Salinity Distribution in the Seto Inland Sea

Abstract A novel brown algal genus and species Setoutiphycus delamareoides (Ectocarpales sensu lato) is described from the Seto Inland Sea, Japan. The species is similar to Delamarea attenuata in gross morphology and anatomy, but distinctive in having longer thalli with rare branching, shorter cortical cells, and occurrence of branches at the tip of plurilocular zoidangia. Erect thalli were epilithic, solitary or caespitose, filiform, simple or rarely branched, attenuated towards the base, blunt at the tip, with uneven surface, yellowish brown in color, up to about 15 cm in height and 2 mm in diameter, parenchymatous, solid when young and later becoming hollow, composed of 1–2 layers of large colorless inner cells, subcortical cells, barrel-shaped large cortical cells of up to 100 µm in height and up to 60 µm in diameter, and phaeophycean hairs. Plurilocular and unilocular zoidangia developed on the same thallus, the former conical to lanceolate, sometimes branched at the tip and projected from the cortical cells, and the latter ovate. Each cell contained many discoidal chloroplasts with projected pyrenoids. In the molecular phylogeny using concatenated DNA sequences of mitochondrial cox1, cox3 and chloroplast atpB, psaA, psbA and rbcL genes, the novel alga nested in the clade composed of ectocarpalean genera of diffuse growth, with parenchymatous thalli with multiple chloroplasts, but was distinctive. Therefore, we propose the establishment of a new genus and species Setoutiphycus delamareoides gen. & sp. nov. for the novel alga, and provisionally place it in Chordariaceae, Ectocarpales sensu lato. As to the biogeography, the Seto Inland Sea repeatedly dried by sea level regression during the glacial periods and the present sea level has recovered after the LGM of ca. 10,000 years ago. Therefore, it is unlikely that the evolution of the genus and species occurred within this area, and its isolated distribution may be explained as a remnant population that survived in the refugia in southern Japan during LGM. It is possible that the species also has a broader distributional range, at least in Japan, such as northern Honshu, but if not, the species can be endangered due to the raise of seawater temperature in the area by global climate change, because the Seto Inland Sea is enclosed at its northern end, so the population cannot spread to colder more northern coasts.

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Discovery of a novel brown algal genus and species Setoutiphycus delamareoides (Phaeophyceae, Ectocarpales) from the Seto Inland Sea, Japan

Scientific Reports ◽

10.1038/s41598-021-93320-7 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Hiroshi Kawai ◽

Takeaki Hanyuda

Keyword(s):

Sea Level ◽

Mitochondrial Gene ◽

Seto Inland Sea ◽

New Genus And Species ◽

Cortical Cells ◽

The Seto Inland Sea ◽

Algal Genus ◽

Sympodial Growth ◽

Glacial Periods ◽

The Last Glacial

AbstractWe describe a new genus and species of brown algae from the Seto Inland Sea, Japan. This species is similar to Delamarea in gross morphology and anatomy, but distinctive in having longer thalli with rare branching and shorter cortical cells. In culture, pluri-zoids derived from plurilocular zoidangia on the erect thalli developed into filamentous gametophytes bearing ectocarpoid plurilocular zoidangia, but also formed parenchymatous erect thalli of sub-sympodial growth similar to Trachynema often having branches, and formed lateral and terminal plurilocular zoidangia. Molecular phylogenies using concatenated chloroplast and mitochondrial gene sequences showed the new alga nested in the clade composed of ectocarpalean genera with diffuse growth, parenchymatous thalli, and multiple chloroplasts, but this species is distinctive. Therefore, we propose Setoutiphycus delamareoides gen. & sp. nov. for this new alga, and provisionally place it in Chordariaceae, Ectocarpales. The Seto Inland Sea repeatedly dried during sea level regressions during glacial periods, and the present sea level recovered after the last glacial maximums (LGM), ca. 10,000 years ago. Therefore, it is unlikely that the species evolved within this area. Its distribution in the area may be explained as a remnant population that survived in refugia in southern Japan during the LGM.

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EVALUATION OF MOUNTAIN AREA AS NON-POINT SOURCE OF NITROGEN FOR SETO INLAND SEA: THE NORTHERN SHIKOKU REGION, JAPAN

Proceedings of International Conference "Managinag risks to coastal regions and communities in a changinag world" (EMECS'11 - SeaCoasts XXVI) ◽

10.31519/conferencearticle_5b1b9389d98135.84095825 ◽

2017 ◽

Author(s):

Shohei Morisawa ◽

Yukio Komai ◽

Takao Kunimatsu ◽

...

Keyword(s):

Average Concentration ◽

Point Sources ◽

Seto Inland Sea ◽

Mountain Streams ◽

Unit Load ◽

Mountain Areas ◽

Mountain Area ◽

The Seto Inland Sea ◽

Unit Load Method ◽

Important Position

The northern Shikoku region is located in the Western part of Japan and faces towards the Seto Inland Sea. The forest area, which is one of the non-point sources in the Seto Inland Sea watershed, occupies 75% of the land use in the watershed of the northern Shikoku region. The amount of loadings of nutrients and COD in the Seto Inland Sea has been estimated by the unit load method but actually the data has not been investigated. It is however, necessary to know the real concentration of nitrogen in mountain streams to evaluate the role which is the mountain area plays as non-point sources. Therefore, more water samples of mountain streams in the watershed need to be taken and the concentrations of nitrogen analyzed. The mountain streams in the northern Shikoku area were investigated from April, 2015 to November, 2015. The number of sampling sites was 283, in addition to the past data by Kunimatsu et al. The average concentration of nitrate nitrogen in Ehime, Kagawa, and Tokushima was 0.61mg/L, 0.78mg/L and 0.34mg/L, respectively. The environmental standard range for nitrogen in the Seto Inland Sea is from between less than 0.2mg/L and less than 1mg/L. Therefore, the average concentration of nitrogen in these regions was over category II, and those of mountain streams in Kagawa Prefecture exceeded category III. About 20% of mountain streams were more than 1mg/L. It has become clear that mountain areas occupy an important position as non-point sources for the Seto Inland Sea.

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