Posted by: lauraearly | August 3, 2011

Not far off the beaten path

fiddler crab

Alex gets a closer look at a male fiddler crab.

Being on an island, we have access to several marine environments other than the sandy beaches usually associated with a subtropical vacation. We were excited to make use of one of these spots on the bay side of Captiva Island for our new course on the mangroves this past week.

The main road that runs through South Seas Island Resort is lined with mangroves on either side for much of the two-mile distance between the entrance at the south end and the northern tip of the island. It’s easy to pass them by without giving them much attention, but they actually harbor a rich ecosystem just itching to be explored.

We hopped off the trolley on the side of the road, and covered ourselves in bugspray. We crossed the road to an opening in the thick line of trees, and I set my stuff down not more than five feet from the shoulder of the road. “Where are we going?” one of the students asked, confused about why I was stopping at the side of the road.

We were greeted by the smell of rotten eggs, a result of hydrogren sulfide produced from the decaying organic matter that makes this environment so rich. As we stepped into the soft black mud, squeals of surprise erupted as the students’ feet disappeared into the mud followed by a sucking sound as they attempted to pull them out. Once we were steady on our feet, we noticed hundreds of small holes in the mud that were not the result of toes in unfamiliar territory. As we quieted and looked closer, we discovered several of little crabs scurrying across the mud, in and out of holes, dodging our curious fingers.

Exploring the "jungle gym" of red mangrove prop roots.

Surrounding the little muddy clearing, were wacky roots protruding in all directions–these were the roots of the mangroves. Closest to the road, knobby finger-like projections stuck up out of the ground. These aerial roots belong to the black mangrove and help with gas exchange in such a dense, anoxic mud. One black mangrove can have up to 10,000 of these aerial roots around its base!

Closer to the water, the prop roots of red mangroves reached out from the base, extended down from the branches, and created a tangle of structure around us. The red mangroves’ prop roots help stabilize the tree and exclude salt while still allowing the tree to drink from its salty surroundings.

A snail leaves a trail of slime as it explores an alien territory.

We discovered though, that these roots are important for many other organisms besides the tree itself. In South Florida, 90% of commercially harvested marine species depend on mangroves at some point during their life. The roots provide structure for a myriad of intertidal creatures to attach, such as oysters, barnacles, tunicates, snails, and crabs just to name a few! Mangroves also act as a nursery, providing shelter to many juvenile marine species. As we climbed over and around the prop roots, we understood why it would be a safe spot to hide from large predators.

As an institution that strongly believes in experiential education, it is always a huge reward when kids so fully experience nature as these students did. The felt the mud squish between their fingers, watched the fiddler crabs wave their oversized claws in the air, heard the call of an osprey from a nearby perch, smelled the organic aroma of decay, and even tasted the salt that creates a harsh environment for many plants. They were exploring a totally new territory, just steps from a paved road, and in the words of 10-year-old, it was the coolest thing she had ever done.

A curious group of explorers among the red mangroves.

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