千曲川付着性藻類の化学成分,とくに脂肪酸組成とMn量について

概要

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The sessile algae were collected from the artificially branched stream of CHIKUMA River in July (one sample) and August (3 samples) 1981. The major species were Nitzchia flusrum (75.1%) and N. romana (14.5%) in July, and N. palea (38.0%), Navicula radiosa (21.7%) and Diatoma vulgare (13.6%) in August. Protein contents were 15.5% of dry matter in July and 19.2% in August. β-Carotene was around 40% of total carotenoids which were 60-73mg per 100g of the samples. The major fatty acid constituents of the samples were 14:0, 16:0, 16:1, 16:2, 16:3, 18:2, 18:3, and 20:5 acids. Seasonal variations were observed on the 18:3 and 20:5 acid constituents of the fatty acid composition; the former was 8% in July and 1% in August, while the latter was 7% in July and 12-15% in August. Maturation of Ayu fish Plecoglossus altivelis in the river was supposed to be synchronized with the increase of 20:5 acid in the algal fatty acid composition. One of the August samples kept in an indoor tank for several days after removal from the stream contained less carotenoids and showed lower 20:5 acid composition than other August samples which were frozen immediately after removal. Frustules of diatoms obtained after acid digestion were 47-54% of the samples. Contents of P, Ca, Mg, Mn, Cu and Zn were 2.6-4.2mg/g, 4.5-5.2mg/g, 37-4.2mg/g, 1.1-1.7mg/g, 2.9-5.1mg/100g, and 11-20mg/100g of dry matter, respectively.