In the highest tech hospital, one of the first things they still do is simply take your pulse.

And if I could go back to when the Chesapeake Bay's health was better and make changes to keep it that way, a lot of them would focus on simply taking the estuary's vital signs.

A comprehensive, long-term and well-publicized monitoring of trends in water chemistry, aquatic life and land use throughout the watershed could have saved so much time and argument.

It could have saved money by preventing the worst declines and by guiding restoration more efficiently. Many of today's best Bay successes and restoration efforts sprang from excellent monitoring.

Monitoring will never lend itself to photo ops and happy press releases; indeed it may initially reveal bad news. Measuring vital parameters like the density and variety of burrowing organisms in Bay sediments is out of sight, out of mind - always a tempting budget cut.

Yet there are probably no ecosystems on Earth where continuous data collection is more crucial for managing than in estuaries like the Chesapeake.

The extraordinarily dynamic nature of the Bay, where oceanic saltwater tussles with freshwater rivers draining a good chunk of the whole East Coast, reflects the Latin root of the word estuary, which means to heave and boil, to surge and be in commotion.

A wet spring - or a wet decade as we had in the 1970s when many Bay systems crashed - can dramatically increase pollutants from the land and the rivers; just as a dry time - like the whole 1960s - can reduce polluted runoff by millions of pounds a year, making things look better than they are.

An ill-timed summer wind blowing out the Bay's mouth as baby blue crabs hatch around the Virginia capes can wash them to sea, depressing next year's harvests. Or the reverse can happen, as when in 1995 Hurricane Felix spun off the Bay's mouth and blew record numbers of blue crab larvae up the estuary.

Only good, long-term data can help sort an estuary's natural ups and downs from those humans are causing. Using short-term data to make any point about the Bay's health should raise caution flags.

It's daunting to think how much data would be ideal. Consider that Tropical Storm Agnes dumped 40 years' worth of polluting, smothering sediments into the Bay during five days in June 1972; and such storms occur only every 100-200 years on average.

You could have monitored sediment to the Bay for a very long time before Agnes and thought you knew what was going on.

In 2000, while researching the decline of coral reefs, I asked experts around the globe if cloudier water, associated with many downturns in the Chesapeake, had occurred.

Not so much, many said, citing measurements back 20-25 years. Then I met Ben Kropp, an Australian who filmed corals underwater for 50 years. The decline in "the viz" happened, he said, before my other experts were old enough to measure.

It was at around 30 years of age that an annual index of spawning success for rockfish came into its own. Done in obscurity by Maryland biologists since 1954, it provided the solid evidence of decline that political leaders needed to shut down fishing in 1984. The results: huge controversy, followed by a historic comeback.

More recently a blue crab survey carried out for more than 20 years by Virginia and Maryland compiled the evidence both states needed to enact controversial harvest limitations. The results: a halt to historic declines and the prospect we'll savor Callinectes sapidus for generations to come.

Not coincidentally, a third major Baywide species, the oyster - never the subject of good, Baywide monitoring - teeters on the edge of commercial extinction. This year, Maryland and Virginia launched an improved and coordinated oyster survey that may lead to a sustainable fishery.

Sometimes the data you need may not lie in the Bay. A chance finding of old water quality measurements made on the Patuxent River in the 1930s turned up in a university's attic. It supported a lawsuit that claimed pollution had worsened, and led to a restoration that continues today.

Many years of counting the insects and little fish that live in streams across Maryland have shown that about 5,000 miles are in decent shape and some 4,000 aren't.

The surveys are showing that even a little development begins degrading nearby waterways; and that restoration efforts may look pretty, but don't restore a stream's life.

Hard lessons indeed; but they are spurring efforts to stop developing our best remaining waterways - like Mattawoman Creek in southern Maryland - before they are irretrievably harmed.

New federal and state rules emerging to restore the Bay will put a larger emphasis on controlling runoff from development and agriculture. Without better monitoring of the results than currently exists, we will waste a lot of effort and money.

Some of the data are already there, collected by farmers who sample their soils; but it is not available to the public or water quality managers.

Other monitoring is available that tells us a lot about solutions to farm manure and runoff - the Green Run study on Maryland's Pocomoke River for example - but it is so little publicized I have to wonder who's afraid of offending whom.

So here's to the Bay's pulse takers - the citizen creek watchers, Riverkeepers and bird banders; the biologists probing the deep bottom muds, sieving plankton from the shallows or aerially surveying submerged grass beds; and to all the measurers and weighers and counters of oyster spat and juvenile herring, migrating silver eels and egg-laying diamondback terrapins.

You're the way we make sense of the complex and ever-changing Chesapeake.