SCCF Education Director was the guest speaker at Rotary on Friday, Oct. 9.
SCCF Education Director was the guest speaker at Rotary on Friday, Oct. 9.

EDITOR'S NOTE: The following report from the Rotary Club of Sanibel Captiva meeting at the Sanibel Community House on Friday, Oct. 9, was submitted by Shirley Jewell of the Rotary Club.

A big shout out and thank you to Kristie Anders, SCCF education director, for stepping in as our guest speaker last Friday morning, when the scheduled speaker had to cancel. Kristie’s topic presented some scientific facts about the influences the Moon and the Sun have on our Tides.

Somewhere around third-grade most of us learn about the Moon’s gravitational pull on the large bodies of water here on Earth cause our ocean tides to rise and fall. That’s about the only thing I knew before Kristie explained some other variables that factor into the tides. Anders definitely had more to present to us on the topic. Hopefully, I get some of this right beginning with the fact that the Sun’s gravitational pull is also part of the process but not as strong of a pull since the Sun is 380 times farther away from the Earth. As the Earth rotates, the Moon orbits our planet. The distance between the Earth and Moon changes slightly during rotation and the strength of the gravitational pull on Earth also changes.

The gravitational pull causes our oceans to bulge out in the direction of the moon and on the opposite side of Earth another bulge occurs because the Earth is being pulled toward the moon. The ocean bulges create our tides. High tide is when the pull is greatest. Now add to this land mass and breaks in large land masses, inlets, bays, rivers, estuaries, etc. Add positioning of the earth in its rotation, distance from the equator, and topography of the land masses, weather, and currents. Now we’re talking. Here on Sanibel the water masses originate in the transition region of the Loop Current and the Florida Current. “The Loop Current is an ocean current that transports warm Caribbean water through the Yucatan Channel between Cuba and Mexico. The current flows northward into the Gulf of Mexico, then loops southeastward just south of the Florida Keys (where it is called the Florida Current), and then just west of the westernmost Bahamas. Here, the waters of the Loop Current flow northward along the U.S. coast and becomes the Gulf Stream”, according to wunderground.com.

The ebb and flow of the tides in and out play an important role in our ecosystem. High tides bring nourishing sediment and sea life into the estuaries. “Estuaries are coastal areas where freshwater mixes with ocean water that is delivered by the tides. Estuaries are home to biologically diverse and unique plant and animal communities,” according to Encyclopedia.com. High tides bring in nutrients that create food for our fish, birds, and other wildlife. Shallow water pools provide nursery areas for fish and shellfish. Mangrove areas thrive along our island estuaries where many birds breed and nest.

Birds plan their feeding patterns on the tides. Long-legged and taller birds have a longer feeding time frame when the water is deeper and as the tide goes out shorter-legged birds feed in shallower water. Tides provide transport for organisms that begin life protected in the shallow areas of our estuaries and when mature use the tide to transport them out to the sea. Seagrasses are pollinated by water flow. Tides affect coastal shorelines in many ways…loss of beach sand and changing shorelines. Seashells are distributed along our shorelines, so much so, that Sanibel and Captiva are called the Shell Islands, known for the best shelling in the world.

When the sea level is rising or falling, water is flowing to and from the ocean. This flow causes currents called tidal currents. Tides enter San Carlos Bay through three narrow water passageways under the Causeway Bridge and one in Red Fish Pass. Depending on water flow restrictions and wind, tide times can reach different locations within our area and with as much as three hours difference. High tides drive ocean waters to our shores and along with wind drives currents through our water passageways and when the tide recedes causing low tide, it leaves sediment behind providing nutriments that our environment and wildlife thrive on.

Limitless and immortal, the waters are the beginning and end of all things on earth.” – Heinrich Zimmer, Historian.

The Sanibel-Captiva Rotary meets at 7 a.m. Friday mornings at the Sanibel Community House, Periwinkle Way. Guests are always welcomed.