Studies on the floating seaweeds - IV : Growth of some sargassaceous algae based on the material secured from floating seaweeds

The sargassaceous algae, with their usual habitat in the sublittoral zone where only infrequent studies have been made possible, are not well known on their process of growth. The present article contains some analytical studies on the subject based on the material secured from floating seaweeds collected monthly in the water near northern Kyushu lasting about one year from March, 1957. The major species found floating and dealt with here number 6 species : Sargassum patens, S. serratifolium, S. tortile, S. horneri, S. fullvellum, Cystophyllum sisymbrioides. The growth curve demonstrated by all the 6 species is sigmoid in shape but the study was not made possible to include young individuals measuring less than 0.5 m in length, which are not occurred in the floating material. For the annual species, such as S. horneri and S. fulvellum, there is about three-month-interval between the fruiting period and the occurrence of individual of the small size above mentioned (0.5 m in length), but for the perennial species the same interval is found usually shorter. Other items as to the growth of each species are shown in the following table.【Table】 The process of growth thus observed on the present material may be similar to that of sargassaceous algae growing on the coast of northern Kyushu, where the floating seaweeds probably originate.ホンダワラ類の生長に関する知見は,流れ藻の季節的な消長を理解する上に必要と考えられるが,潮間帯のヒジキ(片田1941, 須藤1951)を除き天然群落の直接の調査はこれまで報告されていないようである.このことはホンダワラ類の大部分が漸深帯に生育するため,その継続観察が容易でないことに起因するものであろう.筆者等は前述のような観点から,まず1957～8年の流れ藻調査の資料によつて,比較的材料の多い6種類につき調べてみた.以下それについて報告したい・本文に入るに先立ち,本研究に色々と便宜を計つて下さつた九大水産実験所長内田恵太郎教授並びに所員の方々に深謝する