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Sanriku Fukkō NP, Iwate / Miyagi
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Sanriku is not all ria: around Miyako, the coast changes character. Northward, uplifted marine terraces end in cliffs up to 200 m; southward, drowned valleys make jagged bays and peninsulas.
These bays are drowned river valleys, not glacier-carved fjords: streams cut valleys into southern Sanriku, then post-Ice Age sea-level rise flooded them, leaving branching inlets between ridges.
At Shizugawa Bay, more than 220 seaweed and seagrass species have been recorded. Remarkably, cold-water kelp and warm-water arame grow together there—northern and southern underwater forests in one bay.
These sheltered inlets support wakame, scallop, oyster and sea-squirt farming; offshore, cold Oyashio meets warm Kuroshio. Forest-fed streams add nutrients, helping sustain plankton and a varied seafood harvest.
Each winter, Shizugawa Bay's seagrass and seaweed beds feed visiting Brent geese; the bay also hosts white-tailed and Steller's sea eagles. It became a Ramsar wetland in 2018.
The V-shaped coves are beautiful, but their shape matters in an emergency: Japan's Cabinet Office says tsunami force can concentrate at the head of such Sanriku bays, raising local wave heights.
“Ria” comes from the Spanish coastal inlets of Galicia; German geographer Ferdinand von Richthofen introduced the landform term in 1886. Sanriku carries a Galician word across the Pacific.
Iwate began farming wakame in 1949; today, some coastal schools help fishers seed and harvest it, then package the crop—some classes even sell it in Tokyo during school trips.
