In Biscayne Bay report card, no region received a ‘good’ score. Northern areas are worsening.

Adriana Brasileiro
·4 min read

The health of Biscayne Bay is worsening as nutrients and bacteria from canals that feed into the bay continue to pollute its blue waters.

The 2021 Biscayne Bay Report Card announced Thursday by Miami-Dade County Mayor Daniella Levine Cava showed that all regions of the bay received a “fair” or “poor” score in 2021 and not a single region received a “good” score.

The eastern half of the open south-central bay, which was in the “good” range in two prior assessments, fell into the “fair” category this time. The north central inshore region, which includes the Coral Gables waterway and the Snapper Creek Canal, received a “poor” score this year compared with “fair” in prior years.

“It’s a central takeaway from the updated 2021 Biscayne Bay report card that the bay continues to face enormous challenges. As a community, we must remain engaged and committed to protecting our bay,” Levine Cava said during a virtual presentation of the assessment on Thursday.

Multiple efforts have tried to address the bay’s woes over the past decades as population growth and development in Miami-Dade increased pollution. Last year, a fish kill that left some parts of northern Biscayne Bay covered with carcasses shocked residents and spurred the county into projects to better identify and reduce pollution sources. The green, yellow and red stoplight-style report card is one of the tools to monitor indicators and paint a picture of water quality in the bay.

Irela Bagué, appointed the county’s first Chief Bay Officer earlier this year, said the tool will help educate the public on how individual actions can have an impact on Biscayne Bay.

“Biscayne Bay is Miami-Dade County’s most vital quality of life asset, and it’s the mainstay of our economy,” she said.

High surface water temperatures led to a sudden drop in oxygen, which led to the fish kill in northern Biscayne Bay last year.
High surface water temperatures led to a sudden drop in oxygen, which led to the fish kill in northern Biscayne Bay last year.

Before water gets to the bay, it travels through miles of canals that receive stormwater runoff, a major source of pollutants and nutrients that feed algae blooms. Sewage that leaks from septic tanks and broken pipes often ends up in canals that flow to the bay. All that is getting worse as climate change is making storms more frequent, supercharging rainfall and heating up surface water, which leads to deadly drops in dissolved oxygen. Sea rise is increasing groundwater, causing septic tanks to overflow.

Water clarity and chlorophyll indicators, for example, worsened in the Miami River and Coral Gables waterway areas, according to the report card.

Lee Hefty, head of the county’s Division of Environmental Resources Management, said chlorophyll concentrations are elevated in many areas of the bay, a sign that nutrient loads are increasing and threatening seagrass beds. Submerged aquatic vegetation scores declined across northern Biscayne Bay, where the fish kill happened. A 2019 report by the National Oceanic and Atmospheric Administration had sounded the alarm that the bay was undergoing a regime shift, with algae proliferating because of high nutrient loads while seagrass was dying.

Nutrient pollution is increasing algae blooms and contributing to a decline in seagrass meadows in Biscayne Bay.
Nutrient pollution is increasing algae blooms and contributing to a decline in seagrass meadows in Biscayne Bay.

The online tool includes results for combined water quality scores as well as nine individual parameters, including total phosphorus, total nitrogen, water clarity, bacteriological indicators and chlorophyll-a. Habitat quality indicators include submerged aquatic vegetation such as seagrass and macroalgae, as well as sponges.

While results were mostly poor in the northern part of the bay, there was some improvement in the south central inshore area around Cutler Bay, with “fair”overall conditions compared with “poor” in the previous report card.

Hefty said the latest results were based on 2020 numbers, which were compared with a target data set developed with 1996-2004 indicators.

“We picked that time period because water quality can vary throughout the year and from year to year, so we picked some of the better water quality from that time frame as a target and goal for measuring our water quality today,” Hefty said.

The county late last year unveiled a plan to address its 120,000 septic tanks, an important source of nutrients that end up in the bay. It plans to phase out about 1,900 septic tanks that are most vulnerable to compromise or failure and are next to sewage system pipes. They are “low-hanging fruit” and should be completed as soon as the county works out a solution for who pays what, according to Bagué.

Earlier this week county commissioners approved new legislation that bans the application of fertilizers on lawns during the rainy season in an effort to reduce nutrient runoff into the bay.

It’s the first set of Miami-Dade regulations targeting water run-off after the August fish kill.

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