Analysis: Is Martin County water to blame for blue-green algae bloom in Lake Okeechobee?

Yes, rainwater runoff from western Martin County is helping feed an algae bloom in Lake Okeechobee.

No, that water flowing into Lake O via the C-44 Canal has not been the primary source of nutrients feeding the bloom.

In fact, the C-44 did not send as much water and fertilizer runoff into the lake as did farmland south of the lake, according to data for January through July from the South Florida Water Management District.

The algae bloom was caused by "major inflows from the north," Terri Bates, the district's water resources director, told board members Aug. 3.

Bates specifically mentioned a "heavy flush of nutrients" early this summer from the Kissimmee River and creeks north and northwest of Lake O.

According to the district, about 8.7 billion gallons of water was back-pumped into the lake from the south to prevent flooding and save wildlife from drowning in vast marshes north of Everglades National Park.

A deeper dive into data from the water district, however, shows that wasn't all the southern flow into the lake.

According to numbers from the district's public database crunched by Gary Goforth, a Stuart environmental engineer and former district scientist, from January through July:

• More than 27 billion gallons of water flowed from the C-44 Canal into Lake Okeechobee, 15 percent of the total inflow.
• More than 42 billion gallons, 23 percent of the total inflow, came into the lake from the south, the 8.7 billion gallons from back-pumping and the rest in gravity flow from canals in Palm Beach and Hendry counties.
• Nearly 114 billion gallons (62 percent) came from the north and northwest, primarily the Kissimmee River, Lake Istokpoga, Taylor Creek and Fisheating Creek — the sources cited by Bates as the algae bloom's cause.

This year is an aberration. Normally, as farmers south of the lake like to correctly point out, more than 90 percent of the water flowing into Lake O comes from the north.

From 1995 to 2006, flows from the C-44 Canal averaged about 2 percent of the water going into the lake and inflow from the south was about 7 percent.

Nitrogen and phosphorus are fertilizer for crops, and they're also fertilizer for algae.

Goforth's numbers indicate that from from January through July:

• The C-44 Canal contributed 28 percent of the phosphorus and 19 percent of the nitrogen flowing into Lake O.
• Flow from south of the lake added 17 percent of the phosphorus and 31 percent of the nitrogen.
• Northern inflow added 55 percent of the phosphorus and half the nitrogen.

"We don't dispute the numbers," said Judy Sanchez, a spokeswoman for U.S. Sugar Corp., a major landowner south of the lake.

Sanchez did dispute picking a point in time to look at where the water comes from.

"What occurs in the lake is the result of a long period of time," she said. "As always, our main point is that the majority of the water comes from north of the lake."

'Martin's' water

In a July 18 Sunshine State News column, Nancy Smith wrote that "you hear not a single enviro's peep about the untreated stormwater flowing from Martin County INTO Lake O."

And a story appearing July 28 in the Okeechobee News and Aug. 3 in The Clewiston News, although under different bylines, refers to "phosphorus laden runoff from the Martin County watershed."

The emphasis seems to be that Martin County, the area that griped so much when algae-laden water caused a toxic algae bloom in the St. Lucie River last year, is contributing to the algae bloom in Lake O.

True, the water flows from Martin County, but only a small and very rural part of it.

Rainwater runoff from about 132,000 acres in western Martin County drains into the C-44 Canal.

Most of that, 59 percent is farmland; 28 percent has been left natural; and the remaining 13 percent is residential (classified as "urban and other"), according to 2016 data from the water district.

Runoff from the county's major population centers — Stuart, Jensen Beach, Palm City, Hobe Sound, Sewall's Point — doesn't flow into the C-44.

Runoff from Indiantown does, but 1,730 homes and businesses in the small town are on sewer systems, not septic systems, said Martin County Utilities Director John Polley.

Tests toxic

The Lake O bloom was first reported in mid-July and spread through much of the 730-square-mile lake by the end of the month before diminishing last week.

It's now mostly along the northwest corner of the lake.

A sample taken Aug. 1 on the lake shore near the Canal Point community in Palm Beach County contained the toxin microcystin at a level of 815 parts per billion. The World Health Organization considers levels more than 10 parts per billion to be hazardous in recreational contact.

By comparison, during the 2016 algae bloom in the St. Lucie River, microcystin levels reached 33,000 parts per billion at Central Marine marina in northern Stuart.

A DEP crew checked the same toxic site again Aug. 7 and reported finding no algae, so according to agency procedures didn't take any samples.

Wind has blown most of the bloom into the northwest corner of the lake, said Paul Gray, an Okeechobee expert for Audubon Florida, but conditions are still good for the algae to "spring back up" at any time.

Algae blooms occur in Lake O nearly ever summer, with or without water from the C-44 Canal.

Microcystin was found in Lake O 46 times from May 2012 through April 30, 2016, according to the water district's 2017 environmental report.

That doesn't include the massive lake bloom in the summer of 2016 that led to toxic blue-green algae piling up in the St. Lucie River.

In contrast, major algae blooms don't occur in the St. Lucie River unless there are large discharges of water from Lake O.

Last year, algae could be seen leaving a bloom in the lake, traveling east along the C-44 Canal and passing through the St. Lucie Lock Dam into the St. Lucie River.