Nutrient pollution comes from ‘everywhere’

Posted 5/15/19

At their May 8 workshop meeting, the South Florida Water Management District Governing Board was briefed on the complicated issue of nutrient loading into waterways.

The nutrient load from north …

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Nutrient pollution comes from ‘everywhere’


At their May 8 workshop meeting, the South Florida Water Management District Governing Board was briefed on the complicated issue of nutrient loading into waterways.

The nutrient load from north of the lake is a complicated issue.

Even the term “nutrient pollution” can be confusing explained Tom Frick, director, Division of Environmental Assessment and Restoration, Department of Environmental Protection.

“We’re talking about things that are everywhere,” he said. Phosphorus and nitrogen come from the natural systems in Florida and worldwide.

He said as nutrients enter a body of water, the system becomes more productive because there is more food for the plants. This happens naturally over time.

“When that gets accelerated through excessive nutrients, that is when we know there is a problem,” he said. Those problems create shifts that can be detrimental to the water bodies.

Algae food same as plant food
Grass and vegetation is good for the lakes and rivers, he continued. The same nutrients that feed the aquatic vegetation also feed the algae. Under certain conditions, the algae become more competitive than the plants.

“If you lose your vegetation entirely, you come up with an algal system.”
Algae need heat, light and nutrients, he explained.

“Here in Florida we get seasonal changes. As the season goes on, as we’re warming. We have extended periods of light. All of that can cause growth especially if you have excessive loads of nutrients that are being delivered at that time,” said Mr. Frick.

The rainy seasons are delivering excessive nutrients in our water bodies, he continued. It’s a recipe to have some problems.

“Landscape changes are driving the excessive nutrients that are getting to our water bodies,” he said. “There’s more load because you have more volume of that water getting to our water bodies. You need to look if it is a concentration or intensity kind of problem or if it is a landscape change where we’re getting more water.

“Algae is natural. It is out there. It is ubiquitous,” he said. These aren’t exotic species that have been put here.

Those communities (of algae) will change and grow very rapidly especially where there has been excessive landscape changes in the watershed, Mr. Frick continued. Algae takes over the habitat in these systems.

Not all algae can produce toxins. Blue-green algae that can produce toxins does not always do so. Even if an algal bloom does not produce toxins, it can be harmful to the habitat because a thick bloom can shade out aquatic plants. A thick bloom can also reduce the oxygen in the water and if the fish cannot escape the bloom area, the low dissolved oxygen levels can result in fish kills.

Harmful blooms occur globally
Harmful Algae Blooms (HABs) are not unique to Florida, he said. “This is worldwide problem.”

He said worldwide there is a lot of research going on.

“We need to figure out what is triggering those blooms, why are they happening and why are they producing toxins,” he said.

Mr. Frick said the source of the nutrient overload is man made. “We have waste products that come out of all of us,” he said. “Those go into the environment.”

Wastewater treatment facilities and septic systems produce and concentrate nutrients.

Waste from animals including livestock and the wild animals native to Florida. Nutrient sources also include also fertilizer both on agricultural and urban side.

“We have a society that needs production on the agricultural side,” he said. “We have a society that likes green grass.”

A lot of folks like to live and recreate near the water sources, which means there are population centers near water bodies.

Septic systems do not treat for nutrients, Mr. Frick said. “They do a great job of treating for pathogens. They are not treating for nitrogen and phosphorus.”

Treatment plants discharge, too
Wastewater treatment facilities are the other option, he continued. There are 440 permitted domestic wastewater plants in the counties covered by the South Florida Water Management District. Of those 440 plants, 27 are direct discharging effluent into our water bodies, he said. Others are using spray fields or recycling wastewater.

“I am not saying we shouldn’t be worried about the amount of nutrient coming out of those,” he added.

The federal Clean Water Act regulates discharges to surface waters. The Florida Department of Environmental Regulation is responsible for setting the limits on nutrient load into Florida waterways. Urban fertilizer use can be controlled by local government.

Mr. Frick said education is important because homeowners don’t know how much fertilizer to use and if they use too much, the excess winds up in the runoff.