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Nitrates
in the Floridan Aquifer
Breathe in...
78% of what you just inhaled is nitrogen.
Nitrogen is present in all living things and considered a building block of our DNA.
Without it, life on Earth would not be possible.
To understand nitrogen's impact on the Floridan Aquifer, we must first understand the aquifer itself.
THE FLORIDAN AQUIFER
Divers in Peacock Springs, 2018. Photo by John Moran.
KARST (/kärst/)
A landscape underlain by limestone which has been eroded by dissolution.
Much of Florida's geology consists of limerock formations known as karst terrain. Formed 25-60 million years ago when the region was still the sea, Florida's limerock base is composed of fossilized skeletons of marine organisms that have been compressed over time.
A karst landscape is characterized by the presence of sinkholes, springs, and underground streams. These traits are distinctive to karst because they form as [slightly acidic] rainwater percolates down into the aquifer, dissolving soluble limerock as it travels.
Karst riverbank along the Suwanee River.
AQUIFER (/äkwəfər/)
A body of permeable rock which can contain or convey groundwater.
The Floridan Aquifer is considered one of the most productive in the world, due to its vast size (100,000 square miles) and the ability of groundwater to travel easily through its porous limerock.
Exploring the karst of Chassahowitzka, 2016. Photo by John Moran.
Depending on geological conditions, the Floridan Aquifer may be confined or unconfined.
A confining layer is a geological formation through which water cannot penetrate.
In Florida, the confining layer is often a layer of fine sediment or clay.
In unconfined areas, rainwater enters the aquifer directly after percolating through well drained, sandy soils. This crucial process is known as aquifer recharge.
An unconfined aquifer is great for recharge, but this is also where the aquifer is most vulnerable to contaminants from the surface.
That brings us back to nitrogen.
Nitrogen continually cycles through our environment, transforming as it interacts with various natural systems. This process is known as the nitrogen cycle.
An important part of the nitrogen cycle is nitrogen fixation.
Nitrogen fixation is when nitrogen gas in the atmosphere is transformed into organic nitrogen by soil and plant bacteria, making nitrogen that is otherwise unavailable useful for plant growth.
Attenuation is when plants take up excess nitrogen by drawing water with nitrogen into their roots and storing this nutrient in their cells.
Attenuation helps to reduce the amount of nitrogen that reaches the groundwater.
Humans alter the nitrogen cycle by adding nitrogen to the environment in excessive quantities. This is called nitrogen loading.
Fertilizers, human wastewater, and livestock waste are the primary sources of nitrogen loading from activities at the land surface.
Nitrates from human activities may enter the Floridan Aquifer either directly through karst features like sinkholes, or after percolating through sandy soils into the groundwater.
NITRATES IN FLORIDA'S SPRINGS
Many of Florida's water bodies are impaired. The Florida Department of Environmental Protection (FDEP) is required to create plans to identify and reduce the pollutants, including nitrogen. These plans are called Basin Management Action Plans (BMAPs).
When creating BMAPs, FDEP assessed the sources of nitrogen loading for each BMAP area. These sources can be broken into three main categories:
- Development - nitrogen from landscape fertilizers and human wastewater
- Agriculture - nitrogen from farm fertilizers and livestock waste
- Atmospheric Deposition - nitrogen from the atmosphere as gases and precipitation
Use the interactive map below to explore springs BMAP areas and their main sources of nitrogen loading.
Click on the BMAP area to learn how they are impacted by development and agriculture.
BMAPs are described by FDEP as "blueprints for restoring impaired waters by reducing pollutant loading..." Unfortunately, many of these plans fall short in the effort to protect Florida's springs.
Springs advocacy groups are challenging five of the BMAPs under the coordination of the Florida Springs Council .
SANTA FE RIVER BMAP AREA
To learn more about the effects of development and agriculture, we're going to focus on one of the five spring BMAPs being challenged - the Santa Fe River BMAP . The Santa Fe River BMAP area is located in northern Florida and includes the Santa Fe River, the Ichetucknee River, and dozens of springs.
The Santa Fe River. Photo by Hillary Skowronski
The Santa Fe River BMAP Area
Let's take a closer look at two sources of nitrates: development and agriculture.
DEVELOPMENT
Roughly 8 million people lived in Florida in 1974.
By 2016, Florida's population had grown to 20 million.
Fertilizers and human wastewater are the two main sources of nitrate pollution from developed areas.
The impact from fertilized lawns is multiplied many times over in neighborhoods across Florida.
Fertilizers are used on residential lawns, commercial landscapes, and recreational areas such as golf courses and baseball fields.
Human wastewater is also a source of nitrogen. Of the various methods of human wastewater treatment and disposal, septic tanks have the highest nitrogen load and impact on the aquifer.
AGRICULTURE
AQUIFER VULNERABILITY
According to an analysis done by the Florida Geological Survey, certain areas of the Floridan Aquifer are more vulnerable to contamination. Much of Florida's Springs Region has the highest level of vulnerability, meaning that contaminants introduced at the ground level here can enter the aquifer more directly.
AGRICULTURAL LANDS
Much of Florida's agricultural lands lie atop these vulnerable areas in the springs region.
This means that nitrogen from animal waste and the fertilizers used on agricultural crops has a larger impact on the aquifer.
In Florida, location matters.
Fertilizers and livestock waste are the two main sources of nitrate pollution from agricultural areas.
Fertilizers are used on crops across the springs region, with some crops requiring larger amounts of fertilizer.
Livestock waste is another source of nitrates. Livestock operations in the springs region range from smaller operations to large concentrated feeding operations.
Development in the Santa Fe River BMAP Area
FERTILIZERS
According to the Florida Department of Environmental Protection, approximately 161,000 pounds of nitrogen reach the groundwater each year in the Santa Fe BMAP area from residential, commercial, and sports turf fertilizers.
To help visualize the amount of nitrogen, we'll equate it to the load of a dump truck.
That's 5.75 dump trucks of nitrogen in our groundwater each year.
HUMAN WASTEWATER
Approximately 203,000 pounds of nitrogen reach the aquifer each year in the Santa Fe BMAP area from human wastewater.
That's 7.25 dump trucks of nitrogen in our groundwater each year.
Agriculture in the Santa Fe BMAP Area
FARM FERTILIZERS
Approximately 1.05 million pounds of nitrogen reach the aquifer each year in the Santa Fe BMAP area from farm fertilizers.
That's 37.5 dump trucks of nitrogen in our groundwater each year.
LIVESTOCK WASTE
Approximately 347,000 pounds of nitrogen reach the aquifer each year in the Santa Fe BMAP area from livestock waste.
That's 12.4 dump trucks of nitrogen in our groundwater each year.
In total, about 63 dump trucks of nitrogen enter our groundwater each year from human activities in the Santa Fe River BMAP area.
THE IMPACTS
This image was captured by John Moran at Peacock Springs, in June 2019.
An obvious sign of an unhealthy spring is excessive algae growth.
Algae are plant-like organisms that are naturally found in Florida's aquatic systems. Natural levels of nitrogen help aquatic plants grow.
When groundwater with excessive nitrate levels flows into springs and spring-fed rivers, it can act like fertilizer for algae. This can cause algae to grow and spread more rapidly, especially in areas of low water flow.
Algal mats on the Santa Fe River, 2012. Photo by John Moran.
As excessive algae grows, it may form mats at the water’s surface or cover native vegetation underwater, making it difficult for sunlight to reach existing plants.
When vegetation cannot photosynthesize properly, it limits the aquatic food chain and the amount of dissolved oxygen released into the water, making it difficult for aquatic life to thrive.
Filamentous algae overgrowth at Peacock Springs. Photo by John Moran.
Nitrates in the Santa Fe River BMAP area
The Santa Fe River BMAP area, located in northern Florida, contains dozens of springs, including Gilchrist Blue Springs, the Ginnie Spring System, and the Ichetucknee Spring System.
Let's take a closer look at the Ichetucknee River and Spring System as an example of how the Santa Fe River BMAP area is affected by nitrates.
The Ichetucknee River is a six mile long spring-fed river in the Santa Fe BMAP area.
Ichetucknee Springs State Park received over 258,000 visitors in 2018, making it one of the most well known spring systems in Florida.
The Ichetucknee River has long been a favorite spot for tubing.
Photo from the Florida State Archives
The Ichetucknee River, 2019
Ichetucknee Head Spring is a second magnitude spring in the Ichetucknee spring system.
Ichetucknee Head Spring. Photo by Anne Barca
"The Ichetucknee and its run, the most beautiful landscape in the world" -Florida naturalist Archie Carr
This image is of snorkeling with healthy submerged vegetation at Ichetucknee Springs State Park, 2017. Photo by John Moran
If you saw the Ichetucknee River for the first time today, you would invariably be struck by its beauty. But today's Ichetucknee is different than the river once experienced by Archie Carr.
CHANGES IN THE ICHETUCKNEE
For many years the Ichetucknee River and its springs were considered an example of a healthy and thriving spring system. Over time, its water quality has begun to decrease. Increased nitrate levels have contributed to imbalanced algae growth along sections of the river.
Ichetucknee River, 2014. Photo by John Moran
Then and Now on the Ichetucknee, part of the Springs Eternal Project. Photos by John Moran
The Florida Department of Environmental Protection determined that a healthy spring should have a nitrate level of 0.35 mg/L or less.
This graph shows the trend of increasing nitrate levels in the Ichetucknee. Click here for a detailed graph. Photo by J.S. Clark
Data collected in the 1960s show that the Ichetucknee was a healthy spring system, with nitrate levels under 0.35 mg/l. Since then, nitrate levels have more than doubled.
Roughly 80% of Florida's 1,000+ freshwater springs exceed the nitrate limit for healthy springs.
Human activities are disrupting the natural balance of nitrates and algae in Florida's spring ecosystems.
The Floridan Aquifer and its springs are an integral part of Florida's natural heritage.
It's not too late to protect them.
Ichetucknee River, 2016. Photo by John Moran
WHAT CAN I DO?
Awareness and understanding are the first steps. The Blue Water Audit was created by the Howard T. Odum Florida Springs Institute to estimate and visualize human impact on the aquifer. Visit the Blue Water Audit site to learn more about the aquifer and springs, calculate your aquifer footprint, and explore impacts on the aquifer with the Blue Water Audit Interactive Map.
To learn more about springs science, visit www.FloridaSpringsInstitute.org
Cover photo: Manatee Spring, 2013. Wall of Algal Shame by Mark Long
Story map photos: Unless otherwise credited, photos by Florida nature photographer John Moran
3D aquifer models: Haley Moody
Story Map: The Howard T. Odum Florida Springs Institute - Angeline Meeks & Haley Moody