Based on the text, which choice best explains why kelp recovery did not occur in the inner fjords despite high otter de…
Researchers studying kelp forest dynamics off the Aleutian Islands observed that while the reintroduction of sea otters (Enhydra lutris) typically suppresses herbivorous sea urchins and promotes kelp resurgence, this trophic cascade was absent in sheltered inner fjords despite high otter densities. Urchin examinations revealed that inner-fjord urchins subsisted primarily on drift kelp transported by currents from open-water reefs, whereas outer-reef urchins actively grazed live kelp holdfasts. Because inner-fjord urchins fed on drift kelp that accumulated in deep rock crevices, they remained concealed in these crevices rather than foraging on exposed surfaces. Consequently, otters in inner fjords rarely preyed upon them, leaving a persistent urchin population capable of consuming establishing kelp whenever drift kelp supplies intermittently declined.