Portland’s cruise-ship season kicks off today with the visit from the Clelia II, a recently refurbished super-yacht carrying 100 passengers.

Its arrival marks the start of the harbor’s busiest season for the city, with 77 ships carrying 75,370 passengers expected to stop by between now and the end of October.

The cruise ship passengers do more than look at Portland’s historic architecture. Many of them also spend money.

According to a 2008 study done by the University of Maine, the typical cruise ship passenger spends an average of $28 a day on food and beverages and $21 on apparel. When combined with spending on fine art, jewelry and transportation, the average visitor spends $80 a day, or $109 if you count tours provided by the cruise lines.

Since they don’t have their cars, these tourists don’t add to traffic congestion or put pressure on parking facilities.

Portland’s good luck this season is largely the result of trends in the industry based on events far from here.

A new tax and environmental restrictions in Alaska have driven more business to the East Coast.

And cruise lines have been building new ships, and are sending more of the older vessels our way.

But Maine may not always be so lucky, and will have to do more if it is going to keep this business and grow it over time. A proposal to build a deep-water berth at Ocean Gateway is on the ballot next month, as part of the Transportation Bond Question 3.

This project would allow two large ships to visit at the same time, doubling Porltand’s capacity at the peak season for cruise ship visits, which is in late August and September.

Growing the cruise ship business is not a cure-all for Maine’s economy, but it would be a welcome addition to many small businesses during what has been a difficult recession.

In the meantime, we should just welcome the Clelia II, and the others who will follow in the months ahead.