TC PALM: Rainfall runoff lowering salinity, increasing risk of deadly bacteria

This week’s monsoon-like rainfall is dramatically lowering salinity in the St. Lucie River and Indian River Lagoon, and that’s raising the risk of a potentially deadly bacteria.

The fresh rainwater has dropped salinity at some sites, particularly in the lagoon, into the “happy place” for the bacteria Vibrio vulnificus: between 5 and 25 parts per thousand, said Gabrielle Barbarite, a researcher at Florida Atlantic University’s Harbor Branch Oceanographic Institute in Fort Pierce.

“According to my local study and others throughout the (United States), late summer/early fall is peak season for Vibrio because of the rain, low salinity and really warm water,” Barbarite said.

The increased Vibrio risks shouldn’t deter most people from getting on the lagoon this weekend, she said, but anyone with an open wound and/or weak immune systems should avoid contact with the water.

In the St. Lucie River, water quality monitors installed by the Ocean Research & Conservation Association and Harbor Branch indicated virtually no salt in the river Friday morning — below the threshold for Vibrio.

The reason: massive inflows of fresh water from canals stretching far into farmland and groves in western Martin and St. Lucie counties.

The Army Corps of Engineers and the South Florida Water Management District refer to the water as “local runoff,” but that’s a misnomer: The canals have vastly and artificially expanded the St. Lucie River’s natural watershed from about 180,000 acres to more than 514,000 acres.

On Friday morning, rainwater runoff in the C-44 (St. Lucie) Canal that connects Lake Okeechobee and the St. Lucie River was pouring through the St. Lucie Lock and Dam into the river at a rate of nearly 2.6 billion gallons a day. And two other canals — the C-23 and C-24 — were each dumping more than 1.6 billion gallons a day into the river.

Combined, the three canals sent enough runoff into the river to cover the entire city of Stuart with 3 feet 3 1/2 inches of water.

The Army corps pointed out Friday morning that none of the water entering the river and lagoon came from Lake Okeechobee, but the damage is the same.

In its weekly water quality outlook released Thursday, the Florida Oceanographic Society gave the St. Lucie River estuary a “D+” grade. Water in the South Fork got an “F” for its lousy visibility, nonexistent salinity and low level of dissolved oxygen, which can lead to fish kills.

“The question is: How long will the lack of salinity last?” said Mark Perry, Florida Oceanographic executive director. Near-zero salinity for three or four weeks will kill oysters and sea grasses, which are vital to the health of the estuary because they help clean water and provide habitat for fish and shellfish.

AVOID VIBRIO BY CHECKING SALINITY

Research at Florida Atlantic University’s Harbor Branch Oceanographic Institute at Fort Pierce shows the potentially deadly Vibrio vulnificus lives in water with a salinity level between 5 and 25 parts per thousand.
To check salinity levels in the Indian River Lagoon and St. Lucie River, go to tcpalm.com/franchise/indian-river-lagoon/health/worried-about-vibrio-check-salinity-levels

http://www.tcpalm.com/franchise/indian-river-lagoon/health/rainfall-runoff-lowering-salinity-increasing-risk-of-deadly-bacteria_21158305