Orange seaweed washed up near a beach
Ocean chemistry can increase production of seaweed, a vital resource that, in abundance, can become deadly to sea life. Photo: Scott Atwell/NOAA

Protecting and preserving the ecosystems and habitats we depend on is an important part of the mission of Florida Keys National Marine Sanctuary. Learning about and understanding the threats to the sanctuary helps us to safeguard habitats and people from future harm. From the effects of rampant carbon dioxide emissions to missteps by people on the water, here are some of the threats that Florida Keys National Marine Sanctuary faces.

A Warming Ocean

When we burn fossil fuels like oil, coal, and methane gas to power our homes and for gas in our cars, we produce rampant carbon dioxide and release it into the atmosphere. This carbon dioxide builds up and acts like a heat-trapping blanket, warming the Earth and ocean. This process is known as climate change.

Corals depend on colorful photosynthetic algae for food and oxygen, but when the water becomes too warm, stressed corals evict their algae partners. Without the algae, corals become bleached and can die. In recent years, the Florida Keys have experienced widespread coral bleaching events.

Learn about current bleaching conditions in Florida Keys National Marine Sanctuary

Changing Ocean Chemistry

The ocean absorbs rampant carbon dioxide emitted into the atmosphere when we burn fossil fuels like coal, oil, and methane gas. This change in ocean chemistry, called "ocean acidification," reduces the amount of calcium carbonate in the ocean. Just as humans need calcium to build their bones, corals and other animals need calcium carbonate to build strong skeletons and shells. As a result, we are seeing "osteoporosis of the sea," with sea creatures' skeletons and shells becoming thinner or more brittle, or in the case of coral reefs, erosion of the underlying reef structure, which took calcifying organisms a very long time to build or "accrete."

Learn more about ocean acidification through these educational resources

The Ocean's Role in Climate Regulation

A watch on the seafloor next to white corals
A snapshot in time from July of 2023 when the temperature at Newfound Harbor reef caused corals to bleach. Photo: Florida Fish and Wildlife Commission

The ocean regulates the Earth's climate system the way your heart regulates the flow of blood throughout your body. As the heart of the climate's circulatory system, the ocean maintains Earth's temperatures. When we burn fossil fuels, we put a lot of stress on the ocean, damaging its ability to keep the climate stable. As a result of this stress, sometimes the ocean pumps too much heat and moisture throughout the system, and sometimes too little. A heart must be monitored and cared for to ensure overall health and functioning, and the best care is preventative care which involves reducing rampant carbon dioxide.

Learn more about the ocean's role in regulating Earth's climate

Poor Water Quality

An aerial image shows a dark plume of water exiting a channel, dispersing in the blue
                        waters of the ocean
Water gets discharged out the mouths of inlets around South Florida, such as this inlet near Boca Raton, Florida. Photo: Florida Department of Environmental Protection

Poor water quality affects the animals that call the ocean home and the people who depend on it for their livelihoods. Many facets of poor water quality affect Florida Keys National Marine Sanctuary, and nutrient pollution is one of the largest. Nutrient pollution occurs when excessive amounts of nutrients are released into the environment, what scientists call eutrophication. These high nutrient levels come from a variety of sources, both locally and globally from industrial, agricultural, and residential locations. Poorly treated wastewater and stormwater runoff washes nutrients like nitrogen and phosphorus into the ocean, which fuels algal blooms that harm coral and seagrass communities. Florida Keys National Marine Sanctuary is working to tackle this complex issue with our local community and partners.

Visit the Water Quality Protection Program page for more information.

Other Threats

An aerial image of a boat navigating a channel with damaged seagrass in shallow areas on
                        either side.
Prop scars on either side of this channel are illustrative of seafloor damage that occurs from recreational boats. Photo: U.S. Coast Guard.

It is important to be responsible as we live, work, and play in the sanctuary. We can make a difference by handling problems before they get worse with practical, step by step approaches to solve the challenges that face our beautiful ecosystem. Future generations depend on management actions to solve the pressures facing the sanctuary.

A boat submerged below the water line next to a moored sailboat.
This boat became derelict following a storm and now rests on seagrass near Key West. Photo: Scott Atwell/NOAA.

The Florida Fish and Wildlife Conservation Commission believes derelict vessels are a primary threat to the ecosystem. Hundreds of abandoned and derelict vessels litter nearshore waterways of the Keys, obstructing navigational channels, causing harm to the environment, and diminishing commercial and recreational activities. Derelicts originate in a variety of ways, from natural disasters such as hurricanes to boat ownership neglect. These vessels may sink at moorings, becoming semi-submerged in the intertidal zone, or become stranded on shorelines, reefs, or in marshes, and ultimately damage delicate coral reef, seagrass habitat and mangroves.

The shallow waters of the Florida Keys present a significant navigational challenge, even for the most seasoned boater. Hundreds of acres of seagrass are damaged by prop scarring each year, sacrificing the important role the habitat plays in water quality, seafloor stabilization and development of juvenile species. Protecting the seagrass flats is incredibly important, with fines for restoration as one tool to help protect and restore these critical nurseries. After the Big Cat Express, a 136-foot jet-powered catamaran ferry, ran aground in the sanctuary north of Key West harbor in 2016, the company was fined $2.2 million, with the bulk of the money being used to mitigate the damage.

An aerial image of many small vessels moored over a sandbar.
On-water activity has increased dramatically since the sanctuary was established. Photo: NOAA.

Since the sanctuary was established in 1990, Florida's population has increased by more than 75%, angler participation by almost 50%, and between 2010 and 2019, boat registrations in Monroe County leaped from 26,000 to 61,000. The indicators point toward increased use of the ecosystem. Overfishing can deplete key reef species and damage coral habitat, just as illegal activities upset the natural balance of the ecosystem.

A small waste basket caught in a seaweed pile.
Plastic makes up 80% of marine debris. Photo: Scott Atwell/NOAA.

Our oceans are filled with items that do not belong there. Huge amounts of plastics, metals, rubber, paper, textiles, derelict fishing gear, derelict vessels, and other lost or discarded items enter the marine environment every day. This makes marine debris one of the most widespread pollution problems facing the world's ocean and waterways.

A rooster walks on a seawall with orange debris in the distance.
A Key West rooster observing sunrise over a sea of Sargassum. Photo: Scott Atwell/NOAA.

In recent years, increased nutrients in ocean water have fueled larger than normal seaweed production. Massive amounts of Sargassum can form brown tides nearshore, smothering fauna and flora — including coral reefs. Sargassum mats may also clog water intake pipes used in critical infrastructure (for example, in desalination plants that produce drinking water). Sargassum also contains high levels of arsenic and other heavy metals, organic contaminants, and marine debris. Sargassum decomposing on the beach produces hydrogen sulfide, a gas that smells like rotten eggs, which can cause respiratory irritation. Cleanup options are limited and costly.

Want to make a difference?

Are you a young person passionate about the ocean and the natural environment? Want to become an environmental leader at your school or in your community? Looking for ways to develop the skills you need to engage in conservation opportunities? Apply to the new NOAA Ocean Guardian Youth Ambassador Program!