Ecological studies on sea urchins-marine forests interactions in Kuroshio waters

为了阐明放牧海胆对褐大藻爱森藻森林生长和季节性海胆-海洋森林相互作用的影响，在日本西部和歌山县日米崎的一个永久地点进行了研究。5月至7月，由于大量淡水流入导致大量海胆死亡，两种海胆的密度均显著下降。无论在较暖的海洋条件下，大量死亡都能使自行车e.c r.i.幼鱼定植，并使成虫床扩大到1 m深的潮下上层。而在10 ~ 10 m的珊瑚层中，幼轮棘虫消失。早熟禾和早熟禾的成熟尺寸均为直径约18 mm。为了解不同藻类群落中pulcherrimus和a.p assispina在生长和性腺大小上的差异，于7月在日本和山县三滨的一个岩藻床和一个海带床以及两个藻地进行了研究。在顶极期以大型多年生Myagropsis和Ecklonia cava为主的岩藻床和海带床中，H.pulcherrimus的生长高于在几期以小型多年生关节珊瑚为主的藻草坪中。而在岩藻床中，草藻生长最快。两种海胆的性腺指数（性腺湿重× 100/体湿重）均以岩藻床最高。这些结果表明，尽管在顶极阶段的优势种藻类之间存在差异，但日本北部地区的H.pulcherrimus和A.crassispina的生长和性腺产生都受到藻系的影响，如H.pulcherrimus和Strongylocentrotus nudus。

To clarify the effect of grazing of the sea urchins Hemicentrotous pulcherrimus and Anthocidaris crassispina on growth of the brown large alga Eisenia bicyclis forest and seasonal sea urchins - marine forest interactions, study was undertaken in a permanent site at Hinomisaki, Wakayama Prefecture, western Japan. Densities of both the species of sea urchins markedly decreased from May to July due to mass mortality cased by a large amount of freshwater inflow. Mass mortality enabled to colonize juvenile E.bicyclis and the adult beds enlarged to upper subtidals at the depth of 1 m regardless of being under warmer oceanographic condition. While, in articulated corallines beds at the depths of>1 m, juvenile E.bicyclis disappeared. Maturation size of H.pulcherrimus and A.crassispina was>18 mm diameter. Adult H.pulcherrimus in articulated corallines migrated to the kelp bed from autumn to winter when gonads were in maturation to spawningTo clarify the differences in the growth and gonad size of H.pulcherrimus and A.crassispina among algal sere, the study was conducted in July at a fucoid bed and a kelp bed in Gobo and two algal turfs in Mihama, Wakayama Prefecture. The growth of H.pulcherrimus in the fucoid bed and the kelp bed, where the large perennial Myagropsis myagroides and Ecklonia cava at the climax stage dominated, respectively, are higher than that in the algal turfs dominated by the small perennial articulated corallines at the seral stage. While, the most rapid growth of A.crassispina was observed in the fucoid bed. The gonad indices (gonad wet weight x 100/body wet weight) of both species of the sea urchins were highest in the fucoid bed. These results suggest that growth and gonad production of H.pulcherrimus and A.crassispina are affected by algal sere as reported in H.pulcherrimus and Strongylocentrotus nudus in northern Japan, although they differed among dominant species of algae at the climax stage.