Another fish kill hits Biscayne Bay after record flooding: ‘We’re devastated’

Scientists warn fish kill is being fueled by climate change

By Louis Aguirre and Anastasia Brenman

MIAMI – It’s deja vu all over again as another fish kill hits Biscayne Bay, the fourth in as many years.

“This is unfortunately not the first time we’ve seen this type of event,” Miami-Dade Chief Bay and Water Resources Officer Loren Parra said. “We’re devastated to see these reports, certainly so early in the rainy season.”

Since Saturday, upwards of two thousand fish by some estimates have been seen floating on the surface of northern Biscayne Bay following the torrential rains that submerged South Florida last week. The event has spanned from Morningside to North Bay Village, all the way up to 95th Street.

“We’re seeing very low salinity, which is unusual, which tells us there was a significant amount of freshwater flowing into the bay,” explained Lisa Spadafina, the director of Miami-Dade’s Department of Environmental Resource Management.

The two hot spots are two conspicuous triggers of past events, the Biscayne Canal and the Little River, two of the dirtiest bodies of water in all of Miami-Dade County. Both locations have been overflowing with stormwater since June 11.

Biscayne Bay graph
Biscayne Bay graph (Miami Waterkeeper)

Source: Miami Waterkeeper

The graph above shows the flows from the Little River at rates of over 2000 cubic feet per second since Thursday.

“Flood water is extremely contaminated and has sewage in it, potentially septic tank effluent contamination from chemicals, pet waste debris, and all this stuff floating around,” explained Rachel Silverstein, who leads Miami Waterkeeper. “And it’s all eventually draining into Biscayne Bay and into the canals that lead to the bay.”

That dangerous nutrient-loaded water contains critically low oxygen levels. So far, the toadfish have been the most impacted.

“Those are our bottom-dwelling fish, where we mostly see the lowest values of dissolved oxygen,” Spadafina said.

It’s another blow to an already fragile Biscayne Bay that’s no longer resilient enough to withstand the effects of so much water coming in so quickly. It’s worrying scientists because these no-name storms are becoming more intense and happening more often.

“We’re seeing more and more frequent catastrophic rain events in South Florida and, really, the underlying root cause of that is climate change,” said Silverstein.

As our planet continues to heat up, climatologists warn that this can become the new normal. The warmer the air, the more moisture can be held by the atmosphere.

“For every degree Celsius, the atmosphere can hold 7% more moisture,” Jaynatha Obeysekera, the head of Florida International University’s Sea Level Solutions Center, said. “If all of that excess moisture falls, the volume or depth of rainfall could be higher in the future…and that is what we expect.”

Obeysekera said South Florida has accumulated about seven to nine inches of sea level rise in the past 30 years, depending on the location. But what’s concerning is that most of it happened in the last five to 10 years, meaning that sea level rise is accelerating.

“And when the sea is rising, all that extra water [and] extra pressure will cause the groundwater levels to be elevated,” he explained.

Obeysekera further explained that this combined with the intensification of rainfall is causing the compound flooding that South Florida has become more familiar with.

“So I call it a triple whammy, you know, all of them act together to make flooding worse,” he said. “And that’s what’s going on in our region.”

Yoca Arditi-Rocha, the Executive Director of The CLEO Institute, which works with policy-makers and stakeholders to build climate resiliency and climate action, calls these events “un-natural disasters” exacerbated by a warming climate.

“We need to understand that these events are anything but normal, these rain bomb events are becoming more often more frequent,” said Arditi-Rocha. “These are not our traditional tropical storm events, as some of our elected officials have said on television.”

The stakes have never been higher. Arditi-Rocha says it’s time to act urgently and dramatically reduce human emissions of heat-trapping gases that are spewing into our atmosphere to slow down our planet’s warming.

“We don’t need miracles we don’t need silver bullets, we have the solutions (and) it’s about scaling them with speed and intentionality,” she said. “So that gives me tremendous hope.”

How to report a fish kill or algae bloom in Miami-Dade County.

• Visit the environmental complaints webpage and fill out the online form

• Email

• Call 305-372-6955

South Florida Water Management District statement:

The South Florida Water Management District (District) operates the regional water management system, which serves over 9 million people in 16 counties from Orlando to the Florida Keys. Parts of the District experienced heavy rainfall from Invest 90L last week. The District actively monitored, managed and adjusted our primary water management system before, during and after the entire rain event. The District’s regional flood control system performed as designed and we are still monitoring and making operational adjustments as needed. Canal operating ranges were lowered in advance of the rain as part of pre-storm operations.

On the amount of rainfall that SFWMD is designed to handle, this varies basin by basin and depends on the rainfall duration.

When it comes to rainfall, please visit and click on “Raindar Estimates” and “Rainfall Historical” and you will see a dropdown menu with options for how you can see the data for rainfall.

Much of the Central and Southern Florida region has an interconnected water management system, and flood control is a shared responsibility between county/city governments, local drainage districts, communities (including Homeowner Associations or HOAs), and the District. The District continues to work with our drainage partners to provide as much drainage as possible in impacted areas.

Please also see this infographic Rain Drain: What to Expect in Your Neighborhood When It Rains for a close-up look at the interconnected drainage system.

We encourage residents to report flooding to their local drainage operator. They can type in their address and look up their local drainage operator at

Miami-Dade Water and Sewer Department statement:

With more than 20 inches of rain and the additional impact of flood waters to the Miami-Dade Water and Sewer Department’s wastewater infrastructure, the department received and treated roughly 3.74 billion gallons of flow at its three wastewater treatment plants between June 11 and June 16. While responding to the high pressures and high volumes throughout the system during this severe weather event, the department only had eight wastewater overflows (seven within public rights of way and one onsite at a treatment plant), and none made direct contact to surface waters. The successful response throughout the duration of the No-name storm can be attributed to the staffing of essential water professionals at critical department assets, as well as the vital upgrades, investments and improvements Water and Sewer has made to its system as part of the multi-year Capital Improvement Program.

Additional information:

The 3.74 billion gallons of wastewater treated at the plants is equivalent to approximately 5,600 Olympic size pools, while the combined volume of the unrecovered wastewater from overflows was less than 200,000 gallons or only .005 percent of the volume processed through the collection system.

Please note: There was a manhole overflow at US 1 and SW 17 Avenue on Wednesday, June 12 and a portion of the spill entered a nearby storm drain. Because it could not be determined at the time if the nearby storm drain was connected to US 1′s drainage system, in an abundance of caution, No-Swim advisory signage was placed near the drainage ditch at Kennedy Park. Miami-Dade County’s Department of Regulatory and Economic Resources is sampling the area.

Jennifer L. Messemer-Skold, Communications Manager Office of Public Engagement, Miami-Dade Water and Sewer Department

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