(CNN) -- Add Martina McBride and 38 Special to the list of musical acts canceling SeaWorld shows because of issues raised in the documentary "Blackfish."
"I've decided that given all the issues that have been aired recently, the time isn't right for me to play at Seaworld," the singer posted on her Facebook page over the weekend. "I have canceled my scheduled performance at the Bands, Blues & BBQ event in March 2014."
The announcement makes her at least the seventh to drop out.
The southern rock band 38 Special quickly followed with this Facebook posting: "Due to concerns raised by the CNN documentary 'Blackfish,' 38 Special will be canceling its scheduled March 9th concert at Seaworld. We appreciate the outpouring of support and especially apologize to our Orlando fans. We will try and schedule another performance in your area in the near future."
A promoter could put together a whale of a concert series with the acts that have canceled SeaWorld shows in the past several weeks, including Trisha Yearwood, Willie Nelson, Cheap Trick, Heart and Barenaked Ladies.
The acts bailed on the Orlando theme park's concert series amid pressure from fans who started online petitions and took to social media.
Only Justin Moore and Scotty McCreery remain from the original list of acts on the event calendar. Their representatives have not responded to CNN's repeated requests for comment.
The fans became upset after watching the documentary "Blackfish," which first aired on CNN in October. The film tells the story of the killing in 2010 of a SeaWorld trainer by an orca. It raises questions about the safety and humaneness of keeping killer whales in captivity.
SeaWorld confirmed the REO Speedwagon withdrawal Friday and referred CNN to its previous statements about the cancellations.
"We expect that other artists will be targeted in this campaign," SeaWorld spokesman Nick Gollattscheck told CNN in consecutive statements Wednesday and Thursday, starting with Cheap Trick's cancellation.
The park's six-week concert schedule has disappeared from SeaWorld's website. It now simply promises "incredible concerts with top artists in classic rock and country music."
SeaWorld is working to book replacement acts, Gollattscheck said. "We'll announce the full lineup of bands when all artists have been confirmed. We'll repost the schedule on our site then."
The Canadian rock band Barenaked Ladies was the first to cancel, reacting to a petition posted on Change.org.
"This is a complicated issue, and we don't claim to understand all of it, but we don't feel comfortable proceeding with the gig at this time," the band said on its Facebook page.
"I don't agree with the way they treat their animals," Willie Nelson said on December 6 when he canceled. "It wasn't that hard a deal for me."
Sisters Nancy and Ann Wilson of Heart did not elaborate last week when they announced their decision to cancel at SeaWorld, although they acknowledged it was "due to the controversial documentary film."
"We're disappointed a small group of misinformed individuals was able to deny fans what would have been great concerts at SeaWorld," Gollattscheck said.
SeaWorld said it would like the musical artists to learn for themselves about SeaWorld.
"The bands and artists have a standing invitation to visit any of our parks to see firsthand or to speak to any of our animal experts to learn for themselves how we care for animals and how little truth there is to the allegations made by animal extremist groups opposed to the zoological display of marine mammals," Gollattscheck said.
SeaWorld says the documentary ignores the park's conservation efforts and research.