At a time when large fish are rapidly disappearing from the world's oceans, one giant is making a comeback in Florida. The Goliath Grouper was facing extinction when it became a protected species in 1990. Since then, the population has had a chance to recover. Now, some members of the recreational fishing community are pushing to re-open the fishery. But scientists studying the colossal, slow-to-mature fish say such a move would be premature. Changing Seas joins scientists in the field to learn more about the life history of these awe-inspiring fish.

NOAA's Aquarius Reef Base is the only undersea research station operating in the world today. Located just three and a half miles offshore from Key Largo, Florida, at a depth of 60 feet, aquanauts spend ten day missions living and working on the seafloor. Changing Seas observed scientists during a recent mission as they studied the impacts ocean acidification is having on local reef ecosystems. Ocean acidification is caused by a change in the water's chemistry that could have potentially devastating impacts on corals in the future.

In the deep waters off Florida's Atlantic coast grow magnificent structures, capable of reaching 300 feet in height. These are the corals of the deep sea. Porcelain-white and centuries old, few humans have seen these delicate reefs. The Ivory Tree Coral, Oculina varicosa, and Lophelia pertusa flourish in harsh, sunless environments, yet these branch-like formations provide food and shelter for a variety of deep water organisms. Rich in biodiversity, this mysterious underwater kingdom is threatened by destructive fishing practices such as bottom trawling. However, a recently proposed 23,000 square mile marine protected area could save these fragile reefs from ruin.

An ever-growing demand for fresh seafood has pushed wild stocks around the world to the brink. Aquaculture is one alternative to meet the increasing need for fish and crustaceans. Some aquaculture methods have been highly criticized for their negative environmental impacts, but other, more environmentally friendly techniques, are being perfected at various research institutions in Florida. Changing Seas meets with experts who produce fish for food production and to replenish depleted wild populations.

How do you count two fish, three fish or even a school of fish? In Dry Tortugas National Park, located 70 miles from Key West, Florida, a group of scientists have joined forces to conduct a massive fish census. In this unprecedented collaboration, experts from four different agencies unite to count and analyze fish data from select sites. Changing Seas follows highly-skilled science divers as they determine the size of fish populations in hopes of better understanding how fishing pressures and environmental changes affect populations of marine resources within the park.

Bottlenose dolphins are a beloved Florida icon. But, recent studies show disturbing signs of immune system dysfunction and disease plaguing this charismatic mammal. These problems might be linked to legacy contaminants and other pollutants which bio-accumulate up the ocean food chain. Changing Seas meets with experts for an in-depth look at the health status of Florida's wild bottlenose dolphins.

An ancient species of flowering plants that grow beneath the surface of the world's oceans, seagrasses link coastal coral reefs with mangrove forests along the coastline. Today, these "prairies of the sea," along with mangroves, are declining globally. Scientists fear the diminishing vegetation could lead to an ecosystem collapse from the base of the food chain all the way to the top. Changing Seas joins experts in the field as they work to restore Florida's vital mangroves and seagrasses. Seagrasses and mangroves are "hotspots of biodiversity" since they attract and support a variety of marine life. However, damage and removal of these plants continue across the globe at a rapid pace. 'Changing Seas' journeys along Florida's coastline to better understand the significant roles mangroves and seagrasses play within the state.

In the turquoise blue waters of the Florida Keys, a new attraction is drawing scuba divers from around the world: The USNS General Hoyt S. Vandenberg. Laid to rest in the Florida Keys National Marine Sanctuary, the Vandenberg is the world's second largest intentionally sunk shipwreck. In her last mission as an artificial reef, this massive ship is already attracting a variety of fish and other marine life. Now, natural resources managers are trying to determine what impact this artificial reef has on fish populations and the health of the surrounding natural reefs.

In the waters of the western Atlantic and Caribbean, a voracious alien predator has taken hold. Native to the Indo-Pacific, the invasive lionfish is a major threat to biodiversity.

In the emerging science of coral reef restoration, marine biologists and resource managers are discovering naturally occurring mechanisms that promote coral growth and restore ecological balance in these gardens of the sea. Since the late 1970s close to 98% of Staghorn and Elkhorn corals have disappeared from reefs in Florida and the Caribbean. Around the world, damage from boat groundings and other factors have placed these organisms on the "threatened" list of the Endangered Species Act. Staghorn and Elkhorn are considered principal reef building corals. In South Florida, scientists are using native sponges and spiny sea urchins in novel ways that may help attract corals to damaged sites. Can nature heal itself with a little help from marine experts? Can new technologies help restore the lost coral communities?

The oceans are part of America's newest medical frontier. In Florida, scientists are studying a variety of marine invertebrates which may hold the key to unlocking the secrets of our own biology. At Harbor Branch Oceanographic Institute in Fort Pierce, researchers are testing sea sponges for their potential anti-cancer properties. At The Whitney Laboratory for Marine Bioscience in Marineland, experts are taking a closer look at horseshoe crabs to better understand how eyes function and change with age. Scientists there are also studying sea slugs for insights into neurodegenerative disorders such as Alzheimer's and Parkinson's disease. What clues will these and other simple organisms reveal about the human body? Are there cures that lie beneath the waves?

The catastrophic oil spill in the Gulf of Mexico in April 2010 may no longer make headline news, but the story is far from over. Oceanographers continue to study the long-term effects this disaster might have on marine ecosystems. Among them are the scientists from the College of Marine Science at the University of South Florida, who have been studying the impacts of this spill from the beginning. Experts are analyzing water and sediment samples for hydrocarbon presence and toxicity and are studying the long-term effects the spill might have on a number of marine species. What impacts will low-level, chronic toxicity from oil and dispersants have on the environment? How long until the true extent of this disaster will be known?

Sharks are beleaguered species. The oceans' most formidable apex predators are overfished worldwide for their fins, which are considered a delicacy in many Asian countries. Shark populations have declined by up to 90 percent in some cases. But much is still unknown about the animals. Tiger sharks in particular display behaviors that are not well understood. Known to travel long distances, these fish have a broad diet and spend time in shallow, near-shore habitats as well as the depths of the open ocean. Scientists use satellite tags and DNA forensic tools to better understand their migration patterns. Such information is crucial for resource managers to make more informed fisheries management decisions in the future.

They are some the ocean's tiniest inhabitants. On coral reefs, microorganisms are copious creatures. But in a world that's invisible to the naked eye, drastic changes are taking place. Throughout Florida, scientists painstakingly work to identify key players within this microbial community. Recent breakthroughs revealed a direct link between a human pathogen and a devastating coral disease. With corals under immense stress, experts are using advanced genetic tools and a former aquarium "pest" to better comprehend these microscopic organisms. With experimental sites in the lab and in the sea, what will microbes reveal about coral health? How do human activities impact the microbial balance on the reef?

Join researchers from the Reef Environmental Education Foundation and the Cayman Islands Department of Environment as they study one of the last great reproductive populations of Nassau Grouper. Normally a solitary species, during the winter full moons Nassau Grouper travel, sometimes over great distances, to "group" together and spawn. While most of the known spawning sites in the Caribbean have been fished out over the years, the west end of Little Cayman in the Cayman Islands is home to largest known reproductive spawning aggregation of this endangered species.

On the southern tip of the Florida Everglades, the Shark River meets the Gulf of Mexico. This estuary is home to a number of predators, including the alligator and the bull shark. But despite its wild nature, the Everglades ecosystem is in trouble. Humans have greatly reduced water flows across the famed "River of Grass." Now, a large scale restoration project aims to re-direct some of the fresh water back into the Everglades. A team of scientists from Florida International University has been studying predators in the estuary. Their goal is to better understand how these animals will respond to the changes in water flows, to ensure they continue to fulfill their critical ecological role in the food web. This episode is a co-production of Symbio Studios and WPBT2.