PORTLAND (AP) – Shellfish harvesters who were banned from digging clams because of polluted runoff from heavy rains and floods last month are now dealing with a growing problem of red tide on the southern coast.

The red tide closure expanded this week even as the state was lifting other closures caused by runoff on the Maine coast.

“Between the flood closures, all that rainfall we had, and now red tide, it’s competing problems for the poor harvesters,” said Amy Fitzpatrick, public health division director at the Maine Department of Marine Resources.

Red tide is a natural algae that accumulates under the right conditions. People who eat contaminated clams or other shellfish could get sick.

Consumers are protected because the state monitors the algae blooms and bans shellfishing when levels exceed safety limits. But some folks are worried about consumers being able to buy clams and mussels at all if the red tide persists.

Seafood dealers are already paying more than $100 for a bushel for steamers, and prices are creeping up as supply drops.

Josh Philbrick, manager of York Lobster & Seafood, said prices are already a dollar higher than last year for consumers.

“Last year, our prices never really got above $4.99 per pound,” he said. “The price is going to be as high as $5.99 for Father’s Day Weekend.”

The red tide that struck Maine and other parts of New England last year was the worst in more than 30 years. Maine and Massachusetts officials sought emergency financial assistance for clam diggers who were idled much of the summer.

Scientists have warned that this summer could be a costly one, too, based on the amount of the toxin found offshore.

The first red tide closures were in the Harpswell area in April. But signs of the algae remained fairly isolated through May.

“Then we had that storm with the northeast winds, so the bloom got pushed in further into the bays and the coast,” Fitzpatrick said. On Wednesday the closure spread from New Hampshire to Small Point in Phippsburg.

There’s no way to predict how long it will last, Fitzpatrick said. “Hopefully the winds won’t persist and the bloom will die down.”