Portrait of shorebird royal tern Thalasseus on beach

Red Tide has been linked to royal tern deaths on the Sanibel Causeway.

Many residents and visitors have called Sanibel-Captiva Conservation Foundation, the City of Sanibel, and CROW (the Clinic for the Rehabilitation of Wildlife) with concerns about royal terns over the past few weeks and the sight of their carcasses on causeway bridges, SCCF officials said in a release issued Tuesday.

“Although our Marine Lab scientists have detected decreasing levels of Karenia brevis, the dinoflagellate that blooms into red tide, at island beaches over the last two weeks, the number of wildlife impacts has increased,” the release states.

“There have been a large number of sick royal terns observed on our islands and the causeway bridges. Our staff covered all of Sanibel and Captiva on foot last week for the state-wide winter shorebird survey and observed several dead royal terns on the beach,” said SCCF Shorebird Biologist Audrey Albrecht. “I would say across both islands there were several dozen, maybe close to 50 royal terns that appeared sick with possible brevetoxicosis.”

CROW has admitted 60 royal terns since Feb. 1, with 38 deaths, 20 still receiving care, and two birds that have recovered and been released, the release states, adding so far in 2021, CROW has admitted a total of 90 royal terns compared to a total of 49 in all of 2020.

High level of Brevetoxins

Test results on deceased royal terns confirmed Monday they had high levels of brevetoxins, the neurotoxin associated with red tide. On Tuesday, CROW had planned to send several birds to the Southeastern Cooperative Wildlife Disease Study for further analysis, but they were delayed due to bad weather conditions.

“We are planning to send out several birds to SCWDS for full necropsy and testing to see if it is only red tide or if there may be some other secondary disease process as well,” said CROW Medical & Research Director Dr. Heather Barron. “We are currently treating the terns for brevetoxins, and several are being treated for secondary infections since they’re already immunosuppressed.”

Preliminary results are expected in a couple of weeks and final results in about 3-4 weeks.

“They are very thorough. The amount of testing that they do is incredible,” she added.

The city of Sanibel is reminding callers that the Causeway Islands and roadway are outside of the City’s jurisdiction and governed solely by Lee County personnel. Because the terns are being hit on the bridges, drivers are not encouraged to try and rescue injured birds due to traffic concerns.

Red tide still out there?

Though Karenia cell counts have been lower and absent in red tide samples collected from the beaches, SCCF Marine Lab scientists say that doesn’t mean there isn’t a patch out there somewhere.

“The royal terns are feeding on planktivorous fish that have been exposed to a patch of the red tide bloom. The deaths on the causeway are because the birds are sick and resting on the rails or on the road. They can’t avoid the vehicles and are lethargic,” said Marine Lab Director Eric Milbrandt, Ph.D.

The red tide that persisted for two months offshore Lee and Collier Counties is having a lingering affect on Southwest Florida’s coastal ecosystems.

“Some planktivorous fish eat red tide. The terns pick them off when the fish start getting nervous system problems. And then the terns get sick,” Research Scientist Rick Bartelson.Ph.D. said.

“We are working together with CROW and Florida Fish & Wildlife Conservation Commission (FWC) to determine the cause of this sudden increase in sick and dying royal terns, and if possible sickness is leading to the sudden increase in royal terns being hit on the causeway bridges,” SCCF Shorebird Biologist Audrey Albrecht said.

New SCCF logo features royal tern

SCCF on Tuesday launched a new logo featuring imagery of its three pillars of work — land, water, and wildlife. Inspired by a royal tern, the shorebird in the new logo represents the monitoring and research work SCCF scientists do on a variety of species, including shorebirds, sea turtles, terrestrial turtles, and indigo snakes.

“The timing of our new logo launch and the unfortunate situation with our royal terns gives us a chance to deepen the conversation about what is happening with these birds and how it is connected to our water quality issues,” said SCCF CEO Ryan Orgera.

CROW also admitted these avian patients this week: 12 double-crested cormorants (two died, 10 are still at CROW). These birds were admitted and died: one cattle egret, two anhingas, one great blue heron, one herring gull, and two ring-billed gulls.

Sea turtle strandings

SCCF’s sea turtle team has also documented five strandings of sea turtles over the past two weeks. All five washed up dead. Currently, there isn’t any funding available to test these turtles for possible red tide poisoning. To learn more about how you can help meet this unfunded need, please call Development Director Cheryl Giattini at 239-395-2768.

SCCF will continue to monitor the situation and will provide updates on wildlife impacts and testing results.

Source: SCCF