fish kill blog

Consensus Statement on Fish Kill and Algae Bloom in Biscayne Bay

Biscayne Bay is a jewel of our state and the treasured community backyard of Miami. Biscayne Bay generates billions of dollars annually, fueling an active clean water-based economy of real estate, tourism, boating, fishing, sailing, and more. The Bay is a designated Outstanding Florida Water, and hosts the Biscayne Bay Aquatic Preserve, the Bill Sadowski Critical Wildlife Area, and Biscayne National Park. It is also home to over a dozen threatened and endangered species.

On August 10th, a widespread and severe fish kill was observed in northern Biscayne Bay. Reports of dead wildlife, with some fish observed struggling to breathe, were recorded from a wide area within and around northern Biscayne Bay over the following five days.  Reports spanned from the Julia Tuttle Causeway to Miami Shores and east to North Bay Village and Pelican Harbor Seabird Station. Dozens of species were impacted, including toadfish, pufferfish, barracuda, rays, snook, eels, and lobsters.  The size and severity of this fish kill appear unparalleled for Biscayne Bay. This is not a “normal” occurrence, but rather a sign that the ecosystem of Biscayne Bay is seriously out of balance.

Available data point to the immediate cause of the fish kill being low dissolved oxygen (DO) events. Low DO conditions often result from too much nutrient pollution, which fuels the growth of algae and bacteria. Algal and bacterial growth are fueled by the buildup of nutrients, especially phosphorous and nitrogen, from pollution inputs such as sewage leaks, septic tank leachate, stormwater runoff, and fertilizer overuse. As a result, both chronic and acute pollution inputs are likely the ultimate driver of the fish kill.

Dissolved oxygen (DO) is the amount of oxygen available for all life in the water -- both plants and animals. DO levels are one of the key indicators of the health of a body of water. Low DO conditions can often result from excessive algal and bacterial build-up, which results in more DO being used than is being produced. Low DO levels in nutrient-rich water are a known cause of fish kills and “dead zones” in waterbodies, especially in the summer, as warmer water holds less oxygen. Nutrient pollution makes the Bay more vulnerable to increasingly-high temperatures and other stressors. Fish kills and algae blooms have occurred in other parts of the country, but have not been seen on this scale in Biscayne Bay in recent memory. 

(Photo Credit: Tom El-Sahieh)       

        (Photo Credit: Adam Cohen)

Some areas of Biscayne Bay have also lost over 80% of their seagrass over the last few years, with some of the worst losses occurring in northern Biscayne Bay – the same area experiencing this recent fish kill. The seagrass die-off and the fish kill likely have the same underlying cause: excessive nutrient pollution.

On August 21st, we also began receiving reports of a white foam and severe algae blooms in northern Biscayne Bay. The foam and blooms are most likely the result of the decay of so much marine life, i.e., seagrasses and fish, in an already-stressed system. The algal blooms could be a secondary effect of fish kill.

The fish kill event coincided with high flows from the Little River canal this year – over 3.5 times the 10-year average since May. While Biscayne Bay needs fresh water inputs, canal water can have high nutrient and bacteria levels acquired as it passes through urbanized areas on its way to the Bay. We are looking closely at the quality, quantity and timing of input from canals. In the future, flow timing and quantity could be adjusted to potentially minimize the chance of fish kills.

Biscayne Bay is very sensitive to nutrient pollution, and scientists have long warned that the Bay was reaching a tipping point -- shifting from a seagrass-dominated system to an algae-dominated system. This is the tipping point about which scientists have been warning.

The remedy for the seagrass die-off, fish kills, and algae blooms must be addressed by curtailing sewage leaks, converting septic tanks to centralized wastewater treatment, cleaning and treating stormwater, and reducing fertilizer overuse.




Rachel Silverstein, Ph.D.

Executive Director and Waterkeeper, Miami Waterkeeper


Spencer Crowley, M.A., J.D., M.B.A.

Miami-Dade County FIND Commissioner and FL Sea Grant Advisory Council


Todd A. Crowl, Ph.D.

Executive Director, Institute of Environment, Florida International University

Professor, Department of Biological Sciences, Florida International University


Henry O. Briceño, Ph.D.

Professor, Institute of Environment, Florida International University 


Kevin Boswell, Ph.D.

Associate Professor, Institute of Environment, Florida International University


Rolando O. Santos, Ph.D.

Assistant Professor, Institute of Environment, Florida International University


Bradley Schonhoff, MSc

Program Manager, Institute of Environment, Florida International University


Ligia Collado-Vides, Ph.D.
Professor, Institute of Environment, Florida International University


Piero R. Gardinali, Ph.D.

Associate Director, the Institute of Environment, Florida International University


J.S. Rehage, Ph.D.

Associate Professor, Earth & Environment Florida International University


Chris Langdon, Ph.D.

Professor, University of Miami Rosenstiel School of Atmospheric Science


Diego Lirman, Ph.D.

Associate Professor, University of Miami Rosenstiel School of Atmospheric Science


Andrew C. Baker, Ph.D.

Professor, University of Miami Rosenstiel School of Atmospheric Science


Michael C. Schmale, Ph.D.

Professor, University of Miami Rosenstiel School of Atmospheric Science


Joe Serafy, Ph.D.

Research Professor, University of Miami Rosenstiel School of Atmospheric Science


Catherine Macdonald, Ph.D.

Director, Field School & Lecturer, Rosenstiel School of Atmospheric Science


Ana Zangroniz

Florida Sea Grant Extension Agent, UF/IFAS Extension Miami-Dade County


Chris Boykin

Executive Director, Pelican Harbor Seabird Station


David Doebler 

Executive Director,


Dara Schoenwald 



Christine Rupp

Executive Director, Dade Heritage Trust


Seth Bloomgarden

Chair, Surfrider Foundation Miami Chapter


Theodora Long

Executive Director, Marjory Stoneman Douglas Biscayne Nature Center


Matthew Schwartz

Executive Director, South Florida Wildlands Association


Caiti Waks, Esq.

Co-Founder, Debris Free Oceans


Madeline Kaufman, MSc 

Program Director, Debris Free Oceans


Daniel Sebastian Padilla Ochoa

Florida Conservation Partnerships Manager, Ocean Conservancy


Benjamin Blanco

President, Everglades Guides Association


Laura Reynolds

Founder, Conservation Concepts LLC


Melissa E. Abdo, Ph.D.

Regional Director, Sun Coast, National Parks Conservation Association


Steve Friedman

Commodore, FKFGA


Kellie Ralston

Southeast Fisheries Policy Director, American Sportfishing Association


Luiz Rodrigues, MA

Founder/Owner, Eco-Logical Solutions, LLC

Emilio Lopez

Steering Committee Chair, Biscayne Bay Marine Health Summit


Sam Van Leer

President & Founder, Urban Paradise Guild


Eve Samples 

Executive Director, Friends of the Everglades


Paola Ferreira

Executive Director, Tropical Audubon Society


Jim McDuffie

President and Chief Executive Officer, Bonefish & Tarpon Trust


Aaron J. Adams, Ph.D.

Director of Science and Conservation, Bonefish & Tarpon Trust


Ross Boucek, Ph.D.

Director of Florida Keys Initiative, Bonefish & Tarpon Trust


Yoca Arditi-Rocha

Executive Director, The CLEO Institute 


Bruce Matheson

President, Friends of Biscayne Bay


JP Brooker, JD.

Director of Florida Conservation, Ocean Conservancy


Sarah Curry

Founder and Executive Director, Sereia Films

To read more about the fish kill and algae bloom, click HERE and learn more about Miami Waterkeeper's ongoing campaign.

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