北海道日本海南西部岩内のホソメコンブ群落に出現した海藻種とその葉上動物

Abstract

Horizontal and vertical distributions of algal species and occurrence of phytal animals on the algae were investigated in the kelp bed, Laminaria religiosa, at Iwanai on the southwestern coast of Hokkaido, Japan, in June, 2001. A belt transect (1 m wide) was put on the sea floor from 0 to 250 m out from the shore line, and algae found along the transect were identified and counted. Laminaria religiosa was mostly abundant between 2 m and 140 m from the shore line, coverage recorded there being over 50%. Phytal animals on L. religiosa and other 13 algal species were collected by net (1 mm mesh) at a distance of 20 m from the shore line and a depth of 1.5 m. Forty-seven species were collected on 14 algal species, including 6 species of gastropods, 3 bivalves, 10 polychaets, and 25 crustaceans. The lacunid gastropod Temanella turrita was the dominat species on most of the algae. Species diversity of phytal animals was highest for Dictyota dichotoma (number of species occurring=22), followed in order by Symphyocladia latiuscula (21), Polysiphonia morrowii (17), and Sargassum confusum (17). The poorest phytal species diversity was recorded on L. religiosa. The degree of similarity in phytal animal species composition between the algal species was calculated by Kimoto's C11 index, and cluster analysis was done by UPGMA method. Three clusters were recognized, L. religiosa alone, a cluster formed of 11 algal species with a phytal fauna dominated by Temanella turrita, and a cluster formed of 2 algal species with a phytal fauna dominated by crustaceans.