On the wave of unwanted publicity over unruly youths downtown, owners of businesses around the Inner Harbor were probably none too thrilled to have the smell of dead fish wafting through the air last weekend. Naturally, they brushed it off as having no impact on tourism — but you can bet that the odor was about as welcome as another Pat McDonough press conference.

The likely culprit was mahogany tide, an algae that feeds on excess nutrients. This creates huge blooms that eventually die, rot and suck the oxygen out of the water, leaving other forms of aquatic life to suffocate. The fish kill in the Inner Harbor was actually small potatoes (estimated at about 1,000 fish) compared to the 100,000 or so dead fish counted in creeks and tributaries in nearby northern Anne Arundel County.

Algae blooms are nothing new, of course, but to experience such a large fish kill so early in the season is disconcerting, at best. The unusually warm weather likely contributed, but it's also a reminder that the Chesapeake Bay and its tributaries, the Patapsco River included, are in a fragile state because of man-made pollution.

Fish kills aren't a particularly exact way to monitor water quality. Weather can be a determining factor, as can water temperature, droughts, overcrowding and even spawning, all of which can cause excess stress on fish. But the most common cause of fish kills is low dissolved oxygen — and that can be traced to excess nitrogen, phosphorus and sediments from human development and activity.

Efforts to improve the health of the Chesapeake Bay too often are cast as environmentalism versus economic opportunity. Whether it's restrictions on poultry waste; increasing the "flush tax" to pay for upgraded sewage treatment; or requiring new, more effective septic systems, opponents can be counted on to complain of "job-killing" regulations or tax increases.

But that's not really true — and a fish kill in the Inner Harbor demonstrates why. It's not just the health of fish or crabs that's at stake, but the livelihood and well-being of people.

The day that the Inner Harbor is regarded as an open sewer instead of a scenic waterway is the day that the hotels, restaurants and other attractions may as well close up shop. That's not some trivial concern. Billions of dollars in the tourism trade are at stake.

And it doesn't stop there. The buying and selling of waterfront real estate is a huge industry in Maryland as well. You can bet that home values would plunge should fish kills become the norm and not the exception. Who wants to look out from one's balcony to a malodorous pool of foam, brown slime and floating menhaden?

The seafood industry, sportfishing, sightseeing, boating, and waterfront hotels, restaurants and resorts together represent tens of thousands of jobs and a huge chunk of the local economy. An estimated 34,000 jobs and more than $3 billion in annual sales are associated with the Maryland and Virginia commercial seafood industry alone.

Obviously, it would be great if one could simply turn off the pollution spigot — if, let's say, the culprit for the Inner Harbor's woes was coming from some local factory discharge. But the problem is more complex, and so the solution is, too. It requires upgrading sewage treatment, investing in storm water controls, more sustainable farm practices, encouraging smarter patterns of growth, and on and on.

Ignoring fish kills or other evidence of the bay's pollution problems is to allow matters to get worse. To delay pollution-fighting efforts — particularly the federally guided pollution "diet" currently under attack in Congress — is to put Maryland's economic livelihood at risk. That's not just a city problem, or a rural problem; it's everyone's problem.

And while there are legitimate concerns about public safety in Baltimore, teen flash mobs are clearly not the greatest threat facing the region's economic prosperity. The Chesapeake Bay is not only the nation's largest estuary and Maryland's most prized geographic feature; its value in plain old dollars and cents is enormous.

If it takes a fish kill to remind people of that fact, then those thousands of creatures will not have died in vain. Restoration of the Chesapeake Bay is still possible, but what must be accomplished is neither simpler nor cheap. It first requires people to appreciate how much is at stake — and how much worse its circumstances could become.