Dr. Quinton White, executive director of Jacksonville University’s Marine Science Research Institute, takes on the topic of our river’s saltwater — or lack of it — in the latest installment of his regular River Life column in The Florida Times-Union Friday, Sept. 27.
White notes that he’s studied the St. Johns River for decades and is surprised by how its salinity level has fallen.
“Jacksonville University sits about 20 miles from the mouth of the St. Johns River, and salinity has traditionally been between 12 to 18 parts per thousand,” he writes. “High tide pushes seawater upstream, while more rain pushes the freshwater toward the mouth. During the drought years, salinity went to 28-32 ppt, but now we are experiencing the reverse, with lows approaching freshwater.”
The changing salinity stresses plants and animals, he noted.
More development along the river and its drainage system means heavy rainfalls flow more quickly into the river, which may cause the salinity level to decline, he writes.
“In addition to the upland development that has occurred, we have also significantly changed the river by dredging, filling and shifting its flow. These collective activities were done with good intentions and with an expectation of positive results. The unintended consequences have resulted in a river dramatically different than the one Jean Ribault named Rio De Mayo.”I do not know how much more we can do and still expect to see fish, shrimp, manatees and dolphins in the St. Johns River. And I hope our grandchildren aren’t asking: ‘Why did they do that? Didn’t they know it was harmful to the river?’ ”