Two decades of data show climate change is transforming Biscayne Bay, study finds

Two decades of data show climate change is transforming Biscayne Bay, study finds

Twenty years of observations show that Biscayne Bay, the largest estuary on the Atlantic Coast of Florida is becoming warmer, saltier, and more acidic, raising concerns for South Florida ecosystems and water resources.

MIAMI, Fla. — Climate change and sea level rise are altering the chemistry of Biscayne Bay in ways that could threaten South Florida’s coastal ecosystems, water resources, fisheries, and recreation, according to a new study led by scientists from the University of Miami Rosenstiel School of Marine, Atmospheric, and Earth Science and Miami-Dade County’s Department of Environmental Resources Management. Researchers found that over the past 20 years, Biscayne Bay has become warmer, saltier, and more acidic. 

The findings, published in the scientific journal Estuarine, Coastal and Shelf Science, analyzed two decades of water quality observations collected between 2001 and 2021 across Biscayne Bay. 

“Biscayne Bay is changing in measurable ways as climate change accelerates,” said co-author Maria Josefina Olascoaga, a co-author of the study and a professor in the Department of Ocean Sciences at the Rosenstiel School. “We observed that parts of the bay are becoming saltier and warmer, while pH levels are declining, making the water more acidic. These changes can affect seagrasses, fisheries, wildlife, and the broader coastal ecosystem that South Florida communities depend on.”

The researchers evaluated long-term records of salinity, temperature, dissolved oxygen, and pH collected monthly from 34 monitoring stations throughout the bay. They compared changes across decades, seasons, and geographic regions of Biscayne Bay to identify climate-related trends.

The findings show a significant increase in salinity across several regions of Biscayne Bay, especially near canal mouths, where researchers also detected saltwater intrusion in bottom waters. Water temperatures rose throughout the bay, with North Bay warming the fastest. Overall, median temperatures increased by 0.5 degrees Celsius during the study’s second decade. Researchers also documented declining pH levels in most areas, indicating a growing influence of ocean acidification. Together, these changes point to a shift away from historically fresher, estuarine conditions toward saltier, warmer, and more ocean-like waters, reflecting the combined effects of climate change and sea level rise.

Long-term environmental monitoring is critical to understanding how a changing climate is affecting Biscayne Bay at the local level, providing data that help communities and resource managers anticipate and prepare for future impacts on coastal ecosystems and water resources. The authors note that these findings can also inform decisions on water management, restoration projects, and coastal protection efforts aimed at strengthening the bay’s resilience.

Why It Matters

Biscayne Bay encompasses approximately 429 square miles within the boundaries of Miami-Dade County and the City of Miami. It supports South Florida’s economy, tourism, fisheries, recreation, and wildlife habitats. In 2025, scientists from the Shark Research and Conservation Program identified Biscayne Bay as essential nursery habitat for juvenile great hammerhead sharks. The bay also plays a critical role in regional environmental health, including seagrass ecosystems, which are crucial sources of shelter and food for tiny invertebrates, fish, crabs, sea turtles, manatees, and other marine mammals. And the bay offers coastal resilience for Miami-Dade County. Rising salinity and temperature may place additional stress on aquatic organisms and habitats already experiencing environmental pressures. 

The study, “Climate Change Influence on Salinity, Temperature, Dissolved Oxygen and pH in Biscayne Bay (Florida): Two Decades of Observations (2001–2021),” was published online April 9, 2026 in the journal Estuarine, Coastal and Shelf Science.  The authors are Valentina Caccia; Miami Dade-County Department of Environmental Resources Management; Elizabeth Marie Janz, Maria Estevanez, and M. Josefina Olascoaga University of Miami Rosenstiel School of Marine, Atmospheric and Earth Science

The research was supported by the University of Miami through student support for Elizabeth Marie Janz.

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About the University of Miami and Rosenstiel School of Marine, Atmospheric and Earth Science

The University of Miami is a private research university and academic health system with a distinct geographic capacity to connect institutions, individuals, and ideas across the hemisphere and around the world. The University’s vibrant academic community comprises 12 schools and colleges serving more than 19,000 undergraduate and graduate students in more than 180 majors and programs. Located within one of the most dynamic and multicultural cities in the world, the University is building new bridges across geographic, cultural, and intellectual borders, bringing a passion for scholarly excellence, a spirit of innovation, and a commitment to tackling the challenges facing our world. The University of Miami is a member of the prestigious Association of American Universities (AAU).

Founded in 1943, the Rosenstiel School of Marine, Atmospheric, and Earth Science is one of the world’s premier research institutions in the continental United States. The school’s basic and applied research programs seek to improve understanding and prediction of Earth’s geological, oceanic, and atmospheric systems by focusing on four key pillars:

*Saving lives through better forecasting of extreme weather and seismic events. 

*Feeding the world by developing sustainable wild fisheries and aquaculture programs. 

*Unlocking ocean secrets through research on climate, weather, energy and medicine. 

*Preserving marine species, including endangered sharks and other fish, as well as protecting and restoring threatened coral reefs. www.earth.miami.edu.