Effects of grazing by two species of sea urchins (Strongylocentrotus franciscanus and Lytechinus anamesus) on recruitment and survival of two species of kelp (Macrocystis pyrifera and Pterygophora californica)
Effects of grazing by two species of sea urchins (Strongylocentrotus franciscanus and Lytechinus anamesus) on recruitment and survival of two species of kelp (Macrocystis pyrifera and Pterygophora californica)
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两种海胆（Strongylocentrotus franciscanus 和 Lytechinus anamesus）放牧对两种海带（Macrocystis Pyrifera 和 Pterygophora californica）补充和生存的影响
DOI：
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发表时间：
1984
期刊：
影响因子：
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通讯作者：
J. Dixon
中科院分区：
文献类型：
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作者：
T. Dean;S. Schroeter;J. Dixon
我们研究了 1978 年至 1981 年间两种海胆对南加州圣奥诺弗雷海带床中两种海带（Macrocystis Pyrifera 和 Pterygophora californica）的影响。红海胆 Strongylocentrotus franciscanus 和白海胆 Lytechinus anamesus 数量丰富，并且群居。紫海胆（S. purpuratus）在研究地点很罕见，因此没有被研究。红海胆的聚集体要么相对较小且静止（超过 3 年），要么相对较大且活动（以约 2 m mo−1 的速度前进）。同时观察到静止和移动聚集体，且彼此相距 100 m 以内。红海胆的固定聚集可能主要存在于漂流海带上，对海带补充或成年海带丰度没有影响。相比之下，大型的、活动的聚集体或“前沿”的红海胆几乎吃掉了它们路径上的所有大型藻类。性腺的状况表明，相对于小型、固定聚集体中的红海胆，前线的红海胆处于饥饿状态。海带丰度下降两年后（可能主要是由于风暴），形成了大型的、活动的聚集体。我们认为，作为食物的漂流藻类的缺乏会导致红海胆行为模式的改变，从而导致大型活动聚集体的形成。白海胆的聚集发生在海带床的近海边缘，规模很大，但相对静止。白海胆很少吃成年海带，但广泛捕食海带的早期发育阶段，显然阻止了海床向海的扩展。两种红海胆聚集体的空间分布似乎与鱼类或龙虾的捕食压力无关。
We studied the effects of grazing by two species of sea urchins on two species of kelp (Macrocystis pyrifera and Pterygophora californica) in the San Onofre kelp bed in southern California from 1978 through 1981. Both red sea urchins, Strongylocentrotus franciscanus, and white sea urchins, Lytechinus anamesus, were abundant and lived in aggregations. The purple sea urchin (S. purpuratus) was rare at the study site and was not studied. The aggregations of red urchins were either relatively small and stationary (for over 3 yr) or relatively large and motile (advancing at about 2 m mo−1). Both stationary and moving aggregations were observed at the same time, and within 100 m of one another. Stationary aggregations of red urchins probably subsisted mainly on drift kelp and had no effect on kelp recruitment or on adult kelp abundance. In contrast, red sea urchins in large, motile aggregations or “fronts” ate almost all the macroalgae in their path. The condition of their gonalds indicated that red urchins in fronts were starved relative to red urchins in the small, stationary aggregations. Large, motile aggregations developed after 2 yr of declining kelp abundance (probably due largely to storms). We propose that a scarcity of drift algae for food results in a change in the behavior pattern of the red urchins and thus leads to the formation of large, motile aggregations. The aggregations of white urchins, which occurred along the offshore margin of the kelp bed, were large, but relatively stationary. The white urchins rarely ate adult kelps, but grazed extensively on early developmental stages of kelps and evidently prevented seaward expansion of the bed. The spatial distribution of both types of red urchin aggregations appeared to be unrelated to predation pressure from fishes or lobsters.