The 4th of July weekend was a little different this year at the Ipswich Clambake. The restaurant was unable to serve its signature seafood thanks to an outbreak of a toxic alga known as red tide.

“We’re proud to serve our local clams because they’re the best,” said Ken Siegel, owner of Clambake.

But suppliers like Siegel and others on the North Shore breathe a sigh of relief this weekend after the state eased some of its restrictions on harvesting local soft-shell mussels in Essex. Harvest restrictions were put in place there — and on other stretches of coast in the state — last month.

Red tide shellfish, also known as paralytic shellfish poisoning, can cause illness or death in humans if consumed. It occurs when algae get out of control and produce toxins in their waters that are harmful to humans and animals. These toxins can build up in shellfish like clams, oysters, and clams. As the name suggests, it can also turn the surrounding water red.

Restrictions are being put in place to stop shellfish harvesting in areas where high levels of toxins are detected.

Siegel says when those restrictions are in place, he’s buying seafood from abroad, which is affecting him and his customers’ wallets.

“It also increases the price of replacements that we usually have to get from places like Maine, so it hurts everyone,” Siegel said.

He adds that gas prices and supply chain issues are also impacting his bottom line, and he expects this to continue.

Clam Box of Ipswich owner Johanna Pechilis Aggelakis is also buying Maine seafood when red tide restrictions apply.

“They’re more expensive, they’re not as tasty – but they’re still very good,” said Pechilis Aggelakis. “Maine’s clam flats don’t have the mineral richness of Ipswich, so that’s the difference in taste, but it really drives the prices up.”

Although restrictions have been partially lifted on parts of the North Shore, they remain in place across much of the Massachusetts coast, including Gloucester and the bays of Cape Cod and Massachusetts. These are meant to remain in place for at least a week to a month until toxicity levels show signs of a steady decline.

If people in the affected areas want to buy local shellfish, experts recommend buying it from reputable sources until restrictions are lifted.