A waterside traffic jam played out Friday as cargo ships waited for hours to reach Mount Pleasant and North Charleston terminals.

The scene of five cargo vessels idling roughly 15 miles off Charleston’s shoreline in the morning was the result of longshoremen walking off the job Thursday. The stoppage crippled ship operations at Wando Welch and North Charleston terminals for roughly nine hours. The dock workers returned to work Thursday night, shortly after a federal judge signed an order.

Friday’s vessel backlog was due to ships tied at Wando and North Charleston terminals for several hours longer than initially planned, said Allison Skipper, spokeswoman for the S.C. State Ports Authority.

The delays potentially resulted in wrinkles in the world’s supply chain and costly losses for vessel operators, one expert said.

“What we have here is this huge cost bubble that has risen and now it has to be worked off somehow,” said Jim Drogan, a maritime professor at State University of New York Maritime College. Drogan added that added costs such as overtime to catch up cargo will cut into shipper’s profits.

“Those costs will have to be paid someplace ... and I believe at the end it comes to the consumers who will have to pay that,” Drogan said.

The work stoppage was the result of an unspecified number of members of International Longshoremen’s Association Local 1771 Clerks and Checkers being fired for not agreeing to expanded duties outside their labor contract, Ken Riley, president of ILA Local 1422 said Thursday.

Riley did not return phone calls for further comment on Friday.

Clerks and checkers are charged with directing trucks that move in and out of the port. They are employed by stevedore’s, the third-party group that organizes and supervises the work done by longshoremen.

Riley said members of the Local 1422, which load and unload the shipping vessels, walked off the job Thursday as a sign of solidarity.

The longshoremen returned to work Thursday at 7 p.m., shortly after U.S. District Judge David Norton signed a temporary restraining order that told ILA members to return to work at the terminals.

Officials at ILA Local 1771 were not available for comment Friday. A spokesman at ILA’s corporate headquarters did not return a phone call seeking comment Friday.

The backlash of Thursday’s work stoppage was evident Friday morning.

Two cargo vessels were tied at Wando terminal and three ships waited several miles offshore for an OK to cruise into the terminal and unload their cargo. In addition, two ships were tied up at the North Charleston terminal as two other cargo vessels waited off the Charleston’s shoreline for its chance to come in, Skipper said.

The larger-than-usual cargo vessel traffic on Friday forced Charleston Branch Pilots Association to tap more staffers.

“We notified our standby pilots for what can be a flurry of traffic,” said John Cameron, executive director of the Charleston Branch Pilots Association. Harbor pilots guide the large vessels through Charleston Harbor.

Skipper added that SPA was expecting all ships would be worked on Friday.

By early Friday afternoon, there was some relief to the backlog when the Maersk Bratan steamed into Wando terminal. The 733-foot-long container vessel arrived five hours later than its original schedule, Skipper said.

The delays, however, continued as four vessels continued to idle offshore around 4 p.m.

Officials for shippers Maersk and MSC were not available for comment.

Drogan said the work stoppage disrupts supplies for customers needing shipments that are delayed. The disruption also has a ripple effect that impacts other companies like trucking firms and other staffers at the ports.

Drogan added that management should have made sure the labor issue didn’t escalate to the point of ILA staffers walking off the job.

“It’s a difficult time to be playing these power games,” Drogan said. “That’s not going to help the ports, which is trying to get a competitive advantage.”

Reach Tyrone Richardson at 843-937-5550 and follow him on Twitter @tyrichardsonPC.