Saturday, October 18, 2008

The Salt of the Sea and the Muck of the Mangroves

October 16, 2008 - Thursday
John U. Lloyd State Park
Dania Beach, Florida

Finally, we are seeing a change of seasons, after a very long summer of heat, humidity and thunderstorms, the weather is shifting. Today, under blue skies we explored the beauty of the barrier island ecosystem. The breeze kept us cool and refreshed and reminded us of the coming of Halloween and Thanksgiving.

The changes are very subtle here and you have to be familiar with Florida in order to recognize them. Even a drop in a few degrees beckons feelings of Autumn to us Floridians. People start flocking outside, heading to the beach, going camping, maybe a little hiking, or just walking more around their neighborhoods. Then we get the folks coming from the north, leaving the grey cold to enjoy the best time of the year in Florida. I always say that summer here is like winter elsewhere, people stay home more because of the heat and rain and mosquitoes - we curl up with a good book in the air conditioning and wait out the storms! Not quite like a warm fire, a bowl of soup and a book in a winter storm, but the best we have!

Now, back to our nature class. Today was our first homeschooling class after the summer and the turn out was wonderful, including very determined and curious racoons and squirrels. There are alot of new families who are so excited to get out in nature and discover what Florida has to offer, and I am so happy to have them in my class.

John U. Lloyd State Park is a beautiful strip of beach stretching from just North of Dania Pier to Port Everglades Waterway. The Atlantic borders the east, the intracoastal the west, creating a barrier island ecosystem. Along the Atlantic coast side, the beach is long and skinny, caused by tidal erosion, sometimes at low tide, pools of water form - creating fantastic areas to play and dig. The beach is anchored up the shore by the very important dunes. The state park has done a wonderful job restoring these dunes and replanting dune grasses, like the hearty Sea Oats that are everywhere. The dune plants hold on to the sand and prevent it from eroding rapidly. The dunes create a natural barrier and protect the land beyond from the wind and tides. They create an environment for all kinds of critters - beach mice, snakes and other small reptiles, rabbits, insects, nematodes and many amazing plants.

Just inland from the dunes is a calm, shallow and protected inlet of brackish water. The water flows in from the coast on one side and the intracoastal on the other. The intracoastal is fed by both the ocean and fresh water coming from the Everglades. This brackish environment is perfect for sustaining a mangrove habitat. These mangrove forests are the cradle of life in the ocean. Babies of all kinds of animals, including crocodiles, sharks, most fishes, crabs, sea turtles, and birds begin their lives in the shallows of these forests.

The outstretched legs (also known as "prop roots") of the Red Mangrove provide shelter and food; like, mussels, little fish, algae, bacteria and fungi, and small invertebrates. The water below the mangroves is a rich soup of nutrients made up of a recipe of decomposed leaves and branches, animal droppings, and decomposed life forms. This peat is trapped by the roots of the mangroves and serves as a delicious formula for the beginnings of life.

Mangroves are special trees because they can survive not only in water, but in salt water. Across the world there are over fifty different types of mangroves, there are three in Florida, the Red, the Black, and the White. The Red mangroves grow closest to the water and have the "prop roots", or "spider legs", as I call them, they also have the long skinny seeds, called propagules that we see floating in on the tides or littering the beaches. Their seeds can live for at least a year while just floating around. If they happen to find a shallow, muddy area along the coast they will take root. The Black mangroves are notable because the backsides of their rounded leaves are coated with a yummy layer of salt - in the sun they sparkle. Young naturalists love to lick these like salt popsicles. The Black mangrove is expelling the salt for survival. Another way to recognize the Black mangrove is by its "cable roots", which look like sticks popping out of the mud, they are like a snorkle for the tree, providing oxygen while submerged. Further behind the Red and Black mangroves are the White. The White mangroves grow more in the drier, elevated areas, don't have prop roots and have sharper looking eliptical, yellowish green leaves.

Mangroves thrive in salt, why is the sea salty? There are many different legends all over the world which elaborate on various reasons: there is a magic grinding mill from Norway that is infinitely grinding salt into the ocean, and there is the case of the giant from the Phillipines who spread his legs across the ocean so the people could walk across and share his salt - after putting his foot in an ant pile he couldn't keep his legs on the ground and subsequently all of the salt spilt into the ocean. (Go to this link to read the full story: ) Can you come up with your own story?

In our times, we know (or think we do) that the salt comes from mineral and sediments ground away from the earth by water and wind. The salt is carried to the ocean by rivers and deposited into the ocean. Each day water is evaporated and the salt remains, creating fresh water for rain and salt water for the ocean. Some scientists now believe that our oceans would be ridiculously salty if earthquakes didn't continue shaking it all up and redistributing the salt, see the article: The Shaky Solution for a Too-Salty Sea, by Carla Helfferich on Of course, humans and other animals consume the salt, which is absolutely necessary for our survival, and help in its dispersal.

After hearing the story of the giant and his salt and then taking a wonderful nature walk on the boardwalk through the mangroves the kids and I did a little science experiment. We collected water in jars from the ocean, the inlet, and the bathroom sink. Then we put an egg (uncooked) in each jar. The idea was that the egg in the ocean water would float due to the density of the salt in the water. However, none of the eggs floated. Our scientific reason for this was that the fresg water from the great amounts of rain we have had recently has diluted the seawater a bit. We think the flow from the intracoastal has also lessened the salt content.

Our class ended at the beach. We played sharks and minnows to the great approval of most of the kids, others went exploring or swimming, or just relaxed on this beautiful day. The naturalists found sponges, pieces of coral, and one giant seed pod (still unknown). They played tag with the waves and watched an osprey hunting for fish.

It was a beautiful day.

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