Tuesday June 25, 2024

Bay Nature

From a single blade of eelgrass, life overflows. Amphipods build tiny hollow tube-homes on it, while marine snails eat it, and nudibranchs travel its length in search of prey. Small eelgrass sea hares graze epiphytes attached to the blades and lay their yellow eggs inside transparent jelly-like blobs on the thick green of the grass. Amid the meadows, pipefish hide and graceful rock crabs scavenge, and in the fall and spring, giant schools of silvery Pacific herring enter the San Francisco Bay, the end point of their weeks-long annual migration. On the eelgrass, they deposit clumpy beads of yellow roe on the order of hundreds of millions, like underwater honey drops. Or the eggs must taste that way to the thousands of birds that join the melee of feasting. Cormorants and loons dive after flashes of fish. Gulls circle above. Rafts of scaups, buffleheads, and more stretch across the water feeding on roe. During a spawn event, which can last for a few hours or several days, herring milt turns Bay waters a lighter hue.   

Even when the herring aren’t running, the eelgrass beds teem with food. Paige Fernandez remembers kayaking just off the shore of Sausalito. She was paddling over an eelgrass bed, likely brimming with slugs and tiny crustaceans—which were, from the surface, invisible to her. But she could see the harbor seals. And one in particular kept bobbing its head up over the waves, closer and closer. Now a program manager at Richardson Bay Audubon Center, Fernandez says it was “definitely one of the coolest encounters I’ve had in the Bay.” The surfacing seal’s forwardness surprised her, but in retrospect it made sense: she was above a bed of eelgrass. “That’s where they can find little snacks to munch on.” They go where the eelgrass goes—and so does a host of other marine life. 

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