瀬戸内海西部における褐藻クロメの生態学的特性 Ⅰ．現存量と生産量，および形態の多様性

クロメは瀬戸内海中央・西部海域に唯一分布するアラメ・カジメ類であり，藻場の構成種として極めて重要である。本報では2012～13年に瀬戸内海西部（平郡島，片島，屋代島）で調査したクロメの現存量，生産量などの諸元を取りまとめた。優占群落における繁茂期（6～7月）の平均現存量は0.7～1.3kg乾重 m-2であり，成体の平均密度はおおむね10～20個体m-2であった。片島と屋代島・松ヶ鼻において，葉状部のマーキング法で測定した生産量は，繁茂期に10.4～15.6g乾重m-2日-1，衰退期（10～11月）に1.8～5.3g乾重m-2日-1，成長期（2～3月）に5.8～12.9g乾重m-2日-1 であり，本海域のクロメは太平洋や東シナ海のクロメおよび近縁のカジメと同程度の生産力を有していた。繁茂期の成体の茎長や中央葉の長さと幅の比，PPNI値等には調査地間で有意な差異があり，クロメの形態にはそれぞれの生育環境を反映すると推測される多様性がみとめられた。

Ecklonia cava ssp. kurome is the only perennial kelp which is distributed in the central and western areas of the Seto Inland Sea, and is an important component of macroalgal beds in these areas. Biomass and production rates of this species were surveyed at three islands (Heigun-jima Is., Kata-shima Is. and Yashiro-jima Is.) in the western Seto Inland Sea during 2012–13. The mean biomass of dominant stands in the luxuriant season (June–July) ranged from 0.7 to 1.3 kg DW m-2 and the mean adult thallus density was approximately in the range of 10–20 inds. m-2. Net production was estimated by the leaf-marking method at Kata-shima Is. and Matsu-ga-hana in Yashiro-jima Is. Estimated production rates were 10.4–15.6 g DW m-2 d-1 in the luxuriant season, 1.8–5.3 g DW m-2 d-1 in the senescent season (October–November), and 5.8–12.9 g DW m-2 d-1 in the growth season (February–March). These trends were similar to those for E. cava ssp. kurome and its closely related E. cava ssp. cava reported in the Pacific Ocean and East China Sea, respectively. Morphological characteristics, such as stipe length, length/width ratio of the central blade and the primary pinna number index (PPNI) of adult E. cava ssp. kurome thalli exhibited significant differences in the luxuriant season among the survey sites, which reflected variable environmental conditions in their habitats.