TAMPA (WFLA) – It is something many Floridians have surmised, but a cause and effect relationship had not yet been established – until now.

A new study from the University of Florida, Sanibel-Captiva Conservation Foundation and Sarasota Bay Estuary Program found that although red tide often blooms naturally, humans are making them more intense and sustaining them longer due to an infusion of nutrient pollution, namely nitrogen.

The study explains that recent research suggests that natural processes explain the offshore bloom initiation and movement towards shore, however past studies have failed to detect compelling evidence linking coastal blooms to human-produced nutrients running off of land, into the waterways. This study found the connection.

The authors discovered that nitrogen-enriched Caloosahatchee River discharges have consistently intensified red tide blooms. They say river discharge was typically most influential at the earliest stages of blooms, while the total nitrogen concentration had the strongest influence on the blooms growth and maintenance stages.

To reach this conclusion, the study used an advanced analysis to find signals in the dynamics of red tide blooms, water quality and discharge of pollutants in the Charlotte Harbor region between 2012 and 2021.

The authors say their results show that nitrogen in discharges influence blooms in manner that proves causation. Also, the study traced the human influence upstream to Kissimmee River basin, which drains into Lake Okeechobee, which then drains into the Caloosahatchee River and eventually into the Gulf of Mexico.

As explained in the video above, nutrient pollution from agriculture, lawns, golf courses, etc. runs off into Florida’s watershed, especially during the summer rainy season. This is common in the Kissimmee River Basin. That water flows into Lake Okeechobee.

When the lake fills up the Army Corp of Engineers releases water east and west to prevent potential overflow in case of a heavy flooding event – like a hurricane. This is problematic because Lake Okeechobee has been accumulating nutrients for decades and when water is released the nutrients and toxic algae follow.

Once in the Gulf of Mexico, the excess nitrogen intensifies and sustains red tide outbreaks. Since these algae outbreaks thrive in warm water, the warming waters due to climate change can also help to intensify blooms.

Red tide toxins, and the low oxygen environment associated with it, lead to massive fish kills, cause respiratory issues in people and result in economic damage, especially to the tourism industry.

The paper concludes that what is needed to help lessen this problem is large-scale nutrient management and modifications to Lake Okeechobee discharge.

There is an ongoing joint effort between the federal government and the state – called Everglades Restoration – to build infrastructure necessary to send the water south of Lake Okeechobee, to be filtered by wetlands and the Everglades. This, they hope, will reduce the need to divert Lake Okeechobee water into the Caloosahatchee River.