Follow the fertilizer.

One of the suspected culprits of the toxic algae blooms that have plagued south Florida waterways since June can be traced to farms and groves, lawns and golf courses, landscaping and Orlando theme parks. Even local governments may be feeding the blooms. Septic tank leakage has factored as well.

And, environmental experts said, climate change behind fiercer storms and increased heat can bear some blame.

But the trail to the truth, like the polluted water itself, appears murky.

A look at Florida’s fertilizer use by the numbers. Wochit

When the water level in Lake Okeechobee approaches 15 feet above sea level, water managers following orders from Congress drain the lake into the Caloosahatchee and/or St. Lucie Rivers. This releases a steady stream of nutrient-rich waters into the rivers, which have resulted in the algae blooms.

Fertilizer abounds on lands north of the lake, along the Kissimmee River and west of Orlando, the headwaters of that river.

Fertilizer can be found south of the lake, where 41 billion gallons of water, enough to fill about 78,000 Olympic-sized swimming pools, were back-pumped last year by the South Florida Water Management District because of flooding dangers to sugar farms and residential areas in Clewiston and other small towns.

And it can be found along the Caloosahatchee River’s watershed, regardless of the lake water releases.

Following the fertilizer leads to asking: What’s the line between having healthy farms and grass with having healthy waterways?