water quality blog

Flunking Biscayne Bay – The Report Card Is In

Biscayne Bay is an aquatic amenity for millions, bestowing on our community recreational values and economic prosperity in the form of fishing, tourism, and real estate industries… we can’t afford to let it die. I have lived in Miami my whole life, with some of my earliest memories being on the bay with my family swimming, fishing, and getting a little break from the bustling city of Miami. Regardless of socio-economic status, anyone can enjoy the beauty of nature, and this is why it’s important to protect the health of the Bay and provide everyone reasonable access to the water.

To a greater extent, Biscayne Bay is the economic lifeblood of Miami supporting commercial fishing, the shipment and import of goods, bolstering real estate values, and supporting a wide variety of recreational activities, including fishing and diving. An economic evaluation of Biscayne Bay by Hazen and Sawyer (2004) described the bay as contributing approximately $12.7 billion in county production, 137,600 jobs, and $6.3 billion in income to county residents. Not only is the bay a place where people can enjoy time in the beauty of nature, but it’s a substantial reason behind why Miami is as productive and successful as it is, being on par with some of the greatest cities in the world.

Yet for how valuable it is, the Bay faces great challenges in terms of its health and ecological prosperity. Scientists have pointed toward land use changes causing major physical and chemical shifts occurring in the bay since the early 2000s (Caccia & Boyer, 2005). In recent times, the people of Miami have seen (and smelled) some of the most pronounced indications of Biscayne Bay's degradation. 2020 showcased the largest recorded fish kill in Biscayne Bay, occurring from North Miami to Virginia Key and killing over 27 thousand marine creatures across 56 different species. This was a wake-up call to many Miami residents… instead of waking up and smelling the cafecito, people were waking up and smelling the scent of dead fish. 

To many Miami residents, this was an eye-opener to the well-established warning signs and cautionary statements spoken by scientists and activists alike. And unfortunately, to me, the issues we are seeing in the bay aren’t new... going back to the early 2010s, I remember seeing firsthand a shift in seagrass health and abundance in the Snapper Creek and Deering Estate area, with once lush seagrass beds that had turned to dispersed seagrass patches that were being covered by algae mats. These changes have been documented scientifically, with results showing that over the past decade, seagrass cover in Biscayne Bay has had an overall decrease of 70-80%, and over the past 20 years, there has been a total loss of 21 square miles of seagrass beds ("Biscayne Bay is in Danger", 2019). 

Fig. 1 Google Satellite images of seagrass coverage, represented in darker shading, near the Julia Tuttle Causeway in 2011 (pictured left), contrasted with coverage in 2016 (pictured right).

The Bay is suffering as a result of urban stormwater runoff, a lack of regulation, and not enough community action. These have ultimately led to the decline of the bay – to the point where it has been pushed close to its tipping point. We are seeing increased habitat loss and annual fish kill events when there used to be none. While the issues and challenges in the bay seem to keep piling up, there is, however, a silver lining: the bay is now a front-and-center priority for Miamians. The health concerns in the bay have sparked a large number of residents, NGOs, and government officials to come together and work toward a plan to restore and protect the bay and its many assets to our community. In particular, the Biscayne Bay task force, formed in 2020, began a concerted effort with the Department of Regulatory and Economic Resources’ Division of Environmental Resources Management in Miami-Dade to monitor and publish water quality and habitat indicators so that people could understand easily what was happening.  Out of this initiative, the Biscayne Bay report card was created.  It documents in easy-to-read graphics the improvement or decline of the bay’s health in different segments of the bay.  (Fig. 2). The latest annual 2023 Biscayne Bay report card was published on May 2, 2023, and presents an update on the health of the bay with data collected throughout 2022. This year’s report has once again shown the diminished health of the bay–even in worse condition than the previous year. The report card finds that the bay is suffering from elevated nutrient levels, algae blooms, and a decline in seagrass cover and sponge abundance. All regions of the bay showed an overall health score of ‘fair’ or ‘poor’ (Fig. 3), indicating a continued health decline similar to previous years. 


Fig 2. Graphic describing the six water quality and habitat parameters evaluated for the Biscayne Bay report card.

Fig. 3 Biscayne Bay report card overview (left and image of regions and their health status (right).

Increased urbanization, industrial activity, and the inability to properly manage wastewater have been surmised as some of the main reasons behind the decline of bay health as they all increase nutrient loading of nitrogen (N) and phosphorus (P) to the bay environment. While nutrients in and of themselves are not bad (rather, they are essential in the right quantities), too much of a good thing throws a system out of balance. High N and P loads to the bay are the driving factor behind some of the main health issues we see in Biscayne Bay, including the seagrass die-offs and fish kills. Increased N and P have led to a stark increase in algae growth in the water column, which blocks out sunlight from reaching the seagrass on the seafloor. Without light availability, the seagrass can’t undergo photosynthesis, and the grass beds die. When the algae and seagrass die and settle on the seafloor, bacteria work to decompose the organic matter and, in that process, use oxygen in the surrounding water. High oxygen use from bacterial decomposition leads to the lack of oxygen in the water available for the fish to use and causes the fish kills we have recently seen. 

Fig 4. Graphic provided by Sanibel-Captiva Conservation Foundation depicts the process of excess nutrient loading causing fish kills and habitat loss.

The nutrient pollution we see in the bay has built up for decades and is a problem where the fixes to it won’t correct the health of the bay in a few short years. It is a long-term issue that is going to take all of us, from all levels of government down to the community and its local citizens, to correct and maintain for future generations. Some of the most important solutions include shutting off polluted stormwater runoff, adhering to the summer fertilizer blackout period, converting septic tanks to the municipal sewage system, and ensuring the municipal sewage system has the capacity to handle additional demand as our city grows and develops. Some of the solutions needed to correct the health of the bay will prove to be major challenges for our city, but they will ultimately be necessary to ensure the continued prosperity of our environment that is very much intertwined with our economy. 

Call to Action: Apart from the major infrastructure changes that need to be implemented for long-term health management of the bay, you can take action and help the bay with some small but important solutions:

  • Follow the fertilizer ordinance and its May 15 - Oct 31 blackout period
  • Properly dispose of your trash- don’t let it get into a storm drain or blow into the bay.
  • Pick up pet waste and properly dispose of it. 
  • Support political candidates who know and care about the importance of our environment
  • Follow Miami Waterkeeper through social and on our website for updates on policy changes and to learn more about Biscayne Bay health initiatives


Miami Waterkeeper (2020) Fish Kill in Biscayne Bay: A Report and Plan

Caccia, Valentina G., and Joseph N. Boyer. "Spatial patterning of water quality in Biscayne Bay, Florida as a function of land use and water management." Marine Pollution Bulletin 50.11 (2005): 1416-1429.

Biscayne bay is in danger of a 'regime shift,' NOAA study finds. (2019, August 5 ). WLRN Miami South Florida. Retried on March 6, 2020 from https://www.wlrn.org/environment/2019-08-05/biscayne-bay-is-in-danger-of-a-regime-shift-noaa-study-finds

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    • Joshua Linenfelser
      published this page in Blog 2023-05-18 10:58:14 -0400