Nitrates

in the Floridan Aquifer

An underwater image of thick, bright green filamentous algae on a wall in Manatee Springs.

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 swim through caves at Peacock Springs as sun shines down from above.

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.

Riverbank highlighting the holes and crevices in karst along the Suwannee River.

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.

Two children swimming and exploring the caves at Chassahowtizka springs.

Exploring the karst of Chassahowitzka, 2016. Photo by John Moran.

Depending on geological conditions, the Floridan Aquifer may be confined or unconfined.

A 3d model of Florida's karst landscape with the ground surface on top and the Floridan Aquifer below.

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.

The same 3d model of the karst landscape, this time highlight the confining layer.

In unconfined areas, rainwater enters the aquifer directly after percolating through well drained, sandy soils. This crucial process is known as aquifer recharge.

Rain falling on grass.

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.

The same 3d model of the karst landscape with the layers of the aquifer and a highlight showing recharge from rain.

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.

Plants in different stages of growth.

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.

A side view of plants in the ground, showing their roots.

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.

A tractor spreading fertilizer

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.

A map showing developed land in Florida in 1974. There is a minimal amount of developed land.

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.

This GIF begins with aerial imagery zoomed into a few houses. It incrementally zooms out to show hundreds of houses in a large development.

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.

A map showing developed land in Florida in 2016. There is much more developed land

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.

This map shows Florida's Springs Region with information on levels of aquifer vulnerability along with river and spring locations.

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.

This map shows Florida's Springs Region with information on levels of aquifer vulnerability with river and spring locations as well as the location of agricultural lands, most of which are on top of the more vulnerable sections of aquifer.

Development in the Santa Fe River BMAP Area


FERTILIZERS

A sunny golf course with green grass.

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.

An image showing that a dump truck icon equals 28,000 pounds

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.

A map of the Santa Fe River BMAP area showing aquifer vulnerability levels, river and spring locations, and areas of developed lands. There are also 13 dump truck icons.

Agriculture in the Santa Fe BMAP Area


FARM FERTILIZERS

Agricultural fields, on the left side a green crop and hay and hay bails on the right.

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

A grassy field with many black and white cows and one brown and white cow.

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.

A map of the Santa Fe River BMAP area showing aquifer vulnerability levels, river and spring locations, and areas of developed and agricultural lands. There are also 63 dump truck icons.

THE IMPACTS

Half above water and half below water, Peacock Springs is full of thick, bright green algae.

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.

A kayak paddle is draped with thick, green filamentous algae and the river surface is covered in algae too.

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.

A diver is underwater at Peacock Springs and it is filled with filamentous algae.

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.

A historic photo most likely taken in the 60s or 70s of people tubing down the Ichetucknee River

Photo from the Florida State Archives

Video of swimming down the Ichetucknee River showing a white sandy bottom, clear water, and aquatic vegetation.

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

An underwater view of the Ichetucknee showing thick green aquatic vegetation and white sandy bottom.

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.

An underwater view of people tubing on the Ichetucknee, their legs dangling down into water with algae floating and covering the vegetation.

Ichetucknee River, 2014. Photo by John Moran

An image from 1995 at the Ichetucknee shows clear water and thick green vegetation. On the right is the Ichetucknee in 2012, with a man floating in murky water with mostly algae coating the bottom.

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 nitrates increasing from below 0.35 mg/l of NOx-N in the 60s to current levels of almost 80 mg/l of NOx-N. There is a photo of a spring vent in the background.

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

Divers in Peacock Springs, 2018. Photo by John Moran.

Karst riverbank along the Suwanee River.

Exploring the karst of Chassahowitzka, 2016. Photo by John Moran.

The Santa Fe River. Photo by Hillary Skowronski

This image was captured by John Moran at Peacock Springs, in June 2019.

Algal mats on the Santa Fe River, 2012. Photo by John Moran.

Filamentous algae overgrowth at Peacock Springs. Photo by John Moran.

This image is of snorkeling with healthy submerged vegetation at Ichetucknee Springs State Park, 2017. Photo by John Moran

Ichetucknee River, 2014. Photo by John Moran

Then and Now on the Ichetucknee, part of the Springs Eternal Project. Photos by John Moran

This graph shows the trend of increasing nitrate levels in the Ichetucknee.  Click here  for a detailed graph. Photo by J.S. Clark

Ichetucknee River, 2016. Photo by John Moran

The impact from fertilized lawns is multiplied many times over in neighborhoods across Florida.

Photo from the Florida State Archives

The Ichetucknee River, 2019

Ichetucknee Head Spring. Photo by Anne Barca