The whitecaps were blackish-green at Ontario Beach on Wednesday morning, and the water had a familiar bouquet.

Algae, the bane of swimmers at local Lake Ontario beaches, were thick enough that the area was closed to swimming for the day.

But for a small crew of workers who gathered at the beach’s east end, the algae were almost a welcome sight — for it provided one last chance to test a system to pump algae-laden water away from the beach.

The monthlong test, conducted by the U.S. Army Corps of Engineers and Monroe County, was intended to see whether algae could be removed from near-shore waters, thus minimizing the chances that the foul-smelling aquatic growth would force closure of the beach. The system uses a portable pump to suck water from the east end of the beach and deposit it in the nearby Genesee River, which carries it out into Lake Ontario.

The general assessment was that the system, funded with $230,000 from the corps, worked well at removing algae that otherwise would have festered on the beach, possibly prompting closures or aesthetic complaints.

“We’re very happy with the results. I think we have shown that it can work,” said Bryan Hinterberger, project manager for the Army Corps in Buffalo.

That was before the final challenge on Wednesday, the day the test was scheduled to end. Overnight Tuesday, a wind shift had allowed copious amounts of algae to drift toward the sandy beach, creating a larger and more spread-out algal assault than others during the test.

So the pump, connected to an intake attached to the end of a long-armed excavator, was fired up. A front-loader motored back and forth through the surf just off the shore, herding algae-tainted water toward the intake.

By day’s end, thanks partly to uncooperative winds and waves, officials had decided to extend work into today to remove remaining algae.

“There might be times when it’s going to be a more efficient operation than others because of the meteorological conditions, but my sense was that it was working today,” said Charles Knauf, a county environmental health analyst working on the test.

Public swimming areas on Lake Ontario have been bedeviled for years by algae that grow on the lake bottom, break loose and wash ashore. By making the water cloudy and sometimes creating a habitat for bacteria, algae contribute to beach closures.

Ontario Beach has it bad because the west pier at the river mouth traps algae that otherwise would be carried away by the lake’s current.

Beginning more than a decade ago, the Corps of Engineers spent more than $2 million investigating various ideas for addressing the problem. One approach was construction of a large fixed-in-place pumping system, but its $10 million cost was considered far too high by local officials, who would have to foot the bill for any permanent algae-removal system.

This summer’s test, billed as one final effort to find an affordable solution, involved a small, portable system that could be deployed when needed. Two or three people are needed to run it, but some of them work at the beach already.

There’s no cost estimate yet of how much it would cost to make the system a fixture at the beach, though Knauf said it likely would be “extremely inexpensive” compared to the larger fixed pump system.

Ironically, the test period was extended because, until recent days, there had been little algae to test.

“The conditions right until two weeks ago were just astronomical,” Knauf said. “In general, conditions have been the best I’ve seen in 15 years down there.”

So far this summer, Ontario Beach has been closed only five days. Durand-Eastman beach, to the east, has closed only three days.

That’s far better than normal. Between 2006 and 2010, Ontario Beach was closed to swimming an average of 33 days each summer, or 43 percent of the time. Durand-Eastman beach, which first opened to lifeguard-monitored swimming in 2006, was closed an average of 27 days each summer, or 36 percent of the time.

Lack of rain in June and July contributed to the scarcity of beach closures but so did lack of algae. Knauf said one theory is that a harsh winter and rainy spring held down algal growth out in the lake.

Since algae began to reappear at the beach in Charlotte, there were seven occasions before Wednesday when the pump system was turned on. “In all cases they were able to remove the material in between 20 minutes and four hours,” Knauf said.

Local officials had wondered if algae pumped into the river would wash ashore elsewhere and spark complaints. But Knauf said the material seemed to be diluted in the river, and there have been no complaints from people living elsewhere on the lakeshore.

Whether the pump system becomes a fixture at the Charlotte beach remains to be seen. A report on the test is due from the Corps’ contractor by year’s end.

County spokesman Noah Lebowitz said the county would seriously consider deploying a pump system if the test proves it can help and funding could be secured.