Study: Bimini dredging leaves its mark on sharks’ DNA

Scientists have discovered changes in DNA patterns for juvenile lemon sharks that lived through a dredging event to construct a commercial marina in Bimini, Bahamas.

According to the Florida International University, dredging the waters off Bimini for a marina undoubtedly affected the environment. It also left an indelible mark at the molecular level on young lemon sharks in a nearby nursery.

Andria Beal, a Ph.D. candidate in the Institute of Environment, led the first of its kind study to uncover one of the greatest mysteries – how environmental stressors impact sharks.

She found that the dredging event led to epigenetic responses in the sharks, specifically on the DNA markers influenced by changes in the environment.

There are two major lemon shark nurseries in Bimini, a small group of islands about 50 miles east of Miami that are part of the Bahamas. The nursery along North Bimini was directly impacted by the dredging to construct the marina for Resorts World Bimini.

During the dredging, scientists noticed fewer of the younger lemon sharks in the north nursery surviving. They presumed that harmful metals were introduced into the environment but did not investigate further.

Beal was determined to uncover the truth. She examined an archive of fin tissue samples that had been collected before, during and after the dredging event by The Bimini Sharklab in South Bimini. She wasn’t sure what she’d find. After all, she was using a very novel approach. And fin tissue isn’t the ideal way to look for trace metals.

That’s where epigenetics became key to unraveling the mystery.

Although relatively complex, epigenetics stems from the simple fact that every living thing on earth is a product of where it lives. The basic rulebook for life is DNA.

Environmental factors, including trace metals, control what sections of the rulebook will be used – and the bookmarks on those sections are called epigenetic markers.

These makrers determine how the rules are read and what changes are activated. Some can stay for a long time and even be passed on to new generations. Over time, the markers can become a record that tells the story of what stressors a living organism experienced.

Photo: fiu.edu