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 10, 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.
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 21, 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.
Signed,
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
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, Volunteercleanup.org
Dara Schoenwald
Co-Founder, Volunteercleanup.org
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
