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Manatee grass washes on shores of Sanibel beaches

June 14, 2017
By MEGHAN McCOY (mmccoy@breezenewspapers.com) , Island Reporter, Captiva Current, Sanibel-Captiva Islander

Residents and visitors may have noticed something white while strolling the beaches recently. More than two weeks ago sun-dried manatee grass made an appearance at three separate locations.

Dr. Rick Bartleson, Sanibel-Captiva Conservation Foundation research scientist, said although they do not know exactly where manatee grass grows, they know some can be found in the Gulf of Mexico and Pine Island Sound at deep depths, as well as around the Florida Panhandle to the Big Bend area of the state.

"It doesn't grow at shallow (depths) like most grasses because of its structure. The structure of the blades keeps the blades erect," he said adding that such grasses as turtle grass lies down when the tide goes out and it's shallow. "That's why manatee dries out at low tide."

Article Photos

Manatee grass found at West Gulf Access 7 on May 25.

PHOTO PROVIDED

In 2009, Bartleson looked at the manatee grass under a scope for the first time although he had noticed the dry blades of the grass on shore before.

"The dry bits are really light weight and they sort of look like rice paper," Bartleson said.

The manatee grass has triangular shaped membranes, a distinction from other grasses.

"All the sea grasses have different structures inside and manatee grass has its own structure," he said.

When the manatee grass breaks off, the blades float because it is hollow. Bartleson said there is enough structure to the blade that keeps the air, or gas, inside enabling it to float.

"When they start out and break off they still float because of gas. Some of the gases, oxygen they produce, when they photosynthesis," Bartleson said. "That helps them float. While they are floating they get bleached because of the sun."

When a big patch floats by Sanibel it can wash up on the shore, or keep passing by.

One year, he said when Sanibel had manatee grass washing ashore, parts of Texas also had some hit their beaches. Bartleson said this happens because the manatee grass flows with the currents.

"The particles that are the same size and have the same floatation characteristics are going to end up in the same place in the Gulf. Just because of their sizes they are all going to end up in the same spot when the water moves around because they seem to move the same way," he said. "They get together in big patches and sometimes they wash up on the beach and sometimes you see them just coming into the pass under the causeway."

Bartleson said he has pictures of the manatee grass floating under the causeway from 2011.

About two weeks ago, he said colleagues of theirs from the City of Sanibel Natural Resources Department sent pictures of the manatee grass found at West Gulf Access 7. In addition, the SCCF sea turtle volunteers also saw manatee grass at Bowman's Beach and Tarpon Beach.

"It looked like a good size patch from the east end to the west end," Bartleson said.

He said there may be another patch that is getting closer to Sanibel, but without knowing how big the patch is there's no way of knowing for sure if the beaches will be littered with more manatee grass.

When the manatee grass washes ashore, it can float back into the water, or dry up and blow away because of how thin and light weight it becomes.

 
 

 

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