Change to the waterway happened quickly over the next few decades. Swept up in a national movement dubbed "City Beautiful," inspired by the 1893-1894 Chicago World's Fair, Lake Merritt was dredged, diked, and directed into its new role as a showplace of a recreational park. By 1915 its transformation was, if not complete, then irreversible. Adams Point, where lakeside development had begun less than a century before, had become Lakeside Park, sporting imported trees and shrubs as well as lawn bowling greens and tennis courts. The lake's Trestle Glenn arm had become Eastshore Park, which included an ornamental boat landing at East Eighteenth Street and an elaborate Pergola at Castro's Landing where the old wharf or embarcadero, had once existed. At the south end of the lake, the Oakland Civic Auditorium was created. The roadways brought in heavy traffic, and in 1925-in celebration of the encircling boulevard-Lake Merritt was gifted with its "Necklace of Lights." One hundred and twenty-six Florentine light standards and 3,400 pearly bulbs would shine from 1925 until 1941, when World War II blackout conditions forced them off. Ringed in concrete, circled in lights, the wild slough had been tamed, tarted up, and made suitable for community entertainment.

Today the lake is working hard. No longer a sewer, it now does duty as a wildlife refuge, recreational center, and a key component in Oakland flood control. More important, it's still at work for nature as a hydrologic mixing zone where freshwater run-off from the Oakland hills (now channeled through pipes, culverts, and storm drains) mingles, via the outlet beneath Twelfth Street, with the salt water of the Bay. These days, the inlet's water levels are highly manipulated. To assist in the process and to prevent the kind of flooding that would generally occur in periods of heavy rain, a pumping station was added in the 1970s. In winter, when rainfall and runoff from the surrounding hills is high, the water level is deliberately lowered. Salt water is flushed out; salinity decreases. In summer, when flooding is unlikely, the tidal inflow is encouraged; salinity jumps accordingly.

But shifts in salinity are only part of what is going on beneath this tidal inlet's ever changing surface. Lake Merritt is a virtual bouillabaisse. Ropes of microscopic algae float in and out with the tide. Tiny mussels, crabs, shrimp, and barnacle larvae and other drifters like bryozoans and jellyfish graze on the algae. Hordes of silvery anchovies gorge on both kinds of plankton, as do the smelt, those smaller relatives of salmon, that spawn in the lake in spring. And there are tubeworms; slug-like, fuzzy-antennaed mollusks called sea hares; fat rosettes of mature mussel and barnacle colonies; mud burrowing gobies and spiney stickleback-all part of the subaqueous host of squatters competing for the lake's underwater real estate.

Situated on the Pacific Flyway the western coastal highway for all migratory fowl-Lake Merritt is still a very popular stop. Its soupy brew draws pelicans and cormorants and terns and gulls and ducks and geese and herons, many of which nest and raise young on five man-made islands just off Adams Point. To really savor the flavor of this tidal bonanza, the fall and winter months-from September to February are best. Then, the general wildfowl population swells with seasonal visitors. Rafts of feisty American coots scud back and forth over the lake. Fat cheeked ruddy ducks dabble and dip far from shore. Emerald headed mallard drakes and their plain brown mates socialize in the shallows close to the banks. Greater and lesser scaups, canvasbacks, pied-billed grebes, and the occasional goldeneye drift and dive in the deeper waters. Robins, starlings, house sparrows, scrub jays, and red-winged blackbirds hop about and hunt along the shoreline, and generations of Canada geese forage on the surrounding lawns. On rainy days the whole crowd's at its best. Most sensible humans are hiding indoors, and Lake Merritt belongs once more, albeit briefly, to the birds.