Ask an Explorer

Questions were sent to the science party during this expedition. Selected questions and answers are offered below.

Question from: La Quinta Middle School

My 6th grade students were fascinated by the photograph showing the fresh water and the ocean water, side by side, apparently not mixing together. Any good explanations I can give them?
Thanks & Have a great trip!
Suzanne Thomas
La Quinta Middle School
La Quinta, CA

Answer from: Richard Grant Gilmore, Jr., Ph.D.:

Thank you for your question! The image of St. Lucie Inlet with dark brown water, mostly freshwater running into the Atlantic Ocean is particularly dramatic. This is because there is very little tidal range at this location, major freshwater flow from the river (principally due to freshwater released from Lake Okeechobee through man made locks on the C-44 canal) just one mile from the highly saline Atlantic Ocean not too far from the western edge of the Gulf Stream (Florida Current).

The river water is brown due to tannins from swamp and inland plant materials that typically stain Florida peninsula freshwater tributaries. The demarcation between the two water masses of such different densities and chemistries is typical of most estuaries throughout the country. It is only accentuated at St. Lucie due to the proximity of the normally clear Gulf Stream.

The long shore drift is primarily North to South along this coast (right to left in the photo) so the brown freshwater is moving to the south.

I hope this helps your class.

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