Coastal residents have been saying for years that estuaries have become choked with aquatic weeds and clouded with floating algae.
State scientists have decided to try to determine whether that is true, and what the causes and effects might be.
The Southwest Florida Water Management District, or Swiftmud, has announced it will start a two-year water-quality study of the largest spring-fed rivers in Hernando and Citrus counties.
The research will focus on vegetation in the Weeki Wachee, Homosassa, Chassahowitzka, Crystal and Withlacoochee rivers. The Swiftmud governing board decided to begin the project because earlier tests showed an increasing nitrogen level in the rivers, said Scott Stevens, manager for the upcoming research project.
"It was most pronounced in the Weeki Wachee, but we're seeing similar trends in all the springs," Stevens said.
"There's just been an increase in nitrogen in all the springs that we have studied," said Michael Molligan, Swiftmud spokesman.
It was determined from the chemical makeup of the nitrogen compounds that they probably came from the increased use of lawn fertilizers in recent decades.
When preliminary results of that study were released in January, several coastal residents said they had long noticed the effects of nitrogen: increased vegetation.
The new study will address the obvious question raised by the earlier study:
"What is this doing to the estuary?" Stevens said.
Stevens and his team of scientist, assisted by a group from the University of Florida that the district is paying $274,000, will establish 10 sampling stations in each of the five rivers. They will measure for chemicals and vegetation, and take a plant inventory both on the shoreline and in the riverbed.
They also will look for signs of "vegetation on vegetation, or algae coating the leaves of other plants," Stevens said.
That is one of the surest signs of excessive nitrogen in the water, he said.
A healthy and vital river system will support some aquatic plants, Stevens said. But too many can accelerate the process of an estuary being transformed into a marsh. Algae, covering aquatic plants, can kill them. As plant matter decays, it creates more bacteria in the water, and more muck on the ground.
The water will become cloudier, which can starve shellfish beds of the sunlight they need, Stevens said.
"Too much of anything is a bad thing," he said.