Marine Life In & Around Port Tampa Bay Part 2 – Ted Davis

“Port Tampa Bay.” Wikipedia, Wikimedia Foundation, 4 June 2021,

Port Tampa Bay, previously known as the Port of Tampa (up until January 2014), is the largest port in the state of Florida and is overseen by the Tampa Port Authority, a Hillsborough County agency. The port is in Tampa, Florida near downtown Tampa’s Channel District. The port directly accesses Tampa Bay on the western coast of the Florida Suncoast and is approximately 25 sea miles from the Gulf of Mexico. The port district includes parts of Tampa Bay, Hillsborough Bay, McKay Bay, Old Tampa Bay, and the Hillsborough River. The port serves container ships, tank ships, and cruise lines.

Tampa Bay is a large natural harbor and shallow estuary connected to the Gulf of Mexico on the west-central coast of Florida, comprising Hillsborough Bay, McKay Bay, Old Tampa Bay, Middle Tampa Bay, and Lower Tampa Bay. The largest freshwater inflow into the bay is the Hillsborough River, which flows into Hillsborough Bay in downtown Tampa. Many other smaller rivers and streams also flow into Tampa Bay, resulting in a large watershed area.

Geological oceanographer Al Hine and colleagues Beau Suthard and Stan Locker of the University of South Florida’s College of Marine Science explain the origins of Tampa Bay’s bottom, which dates back many million years. “Millions of people live around Tampa Bay. We travel over it on bridges and swim and fish in it,” says Hine. ” It’s a part of our daily life, but we know very little about how it came to be.”

Florida has unique origins. What would become the basement rocks of Florida were once part of other continents. During the early part of the Cenozoic Era, Florida was submerged under a warm, shallow, ocean which explains why our entire state has hundreds to thousands of feet of limestone beneath it! Land emerged from the ocean as sea level fell during the Oligocene Epoch. 

During the latter part of the Cenozoic Era, quartz sand and clays were transported to Florida, via rivers and marine currents, from the Appalachian Mountain belt as it eroded over millions of years. Great pods of migrating whales would come to the shallow seas that would eventually become Tampa Bay. Gigantic sharks called Megalodons would follow them into the shallow waters and feed.

“Florida Department of Environmental Protection. (2021, December), Florida Geologic Formations

“The basin that is now Tampa Bay formed between 15 and 7 million years ago when the underlying limestone was deformed by collapses,” explained Hine. “The basement of Tampa Bay consists of ancient sub-basins deformed into sinks, folds, sags and warps, later filled in by the by the sand sediments. “About four to six million years ago, the wrinkled, shallow bottom was topped off by a massive transport of quartz sand that originated 1000 miles north. “Ever since the first geologist walked local beaches in the early part of the last century, it was obvious to him that what we call the Florida Platform received a shipment of sand in the region’s deep, geologic past,” explains Hine. How the sand got here is still not very well understood. But millions of years after it arrived, the ancient sand shipment was remobilized locally, probably in very wet years by river flow, and it flowed into and filled in the bottom of Tampa Bay. According to USF researchers, the foreign sand originated in silicate-rich bedrock in the Appalachian Mountains and Piedmont area in what is now the eastern U.S. mid-Atlantic region. The rocks that weathered to produce the sand were already hundreds of millions of years old., “Oceanographers Explain the Origins of Tampa Bay” (2006, November),  Tampa Bay is Florida’s largest open-water estuary, extending over 400 square miles and forming coastlines of Hillsborough, Manatee and Pinellas counties.

The freshwater sources of the bay are distributed among over a hundred small tributaries, rather than a single river. The Hillsborough River is the largest such freshwater source, with the Alafia, Manatee, and Little Manatee rivers the next largest sources. Because of these many flows into the bay, its large watershed covers portions of five Florida counties and approximately 2,200 square miles. The bottom of Tampa Bay is silty and sandy, with an average water depth of only about 12 feet. The relatively shallow water and tidal mudflats allow for large sea grass beds, and along with the surrounding mangrove-dominated wetlands, the bay provides habitat for a wide variety of life.

More than 200 species of fish are found in the waters of the Bay, along with bottlenose dolphins, manatees, and many types of invertebrates including oysters, scallops, clams, shrimp, and crab. More than two dozen species of birds, including brown pelicans, several types of heron and egret, Roseate spoonbills, cormorants, and laughing gulls make their year-round home along its shores and small islands, with several other migratory species joining them in the winter. The cooler months are also when warm-water outfalls from power plants bordering the bay draw one out of every six West Indian manatees, an endangered species, to the area. Tampa Bay has been designated an “Estuary of National Significance” by the United States Environmental Protection Agency. Two National Wildlife Refuges are in Tampa Bay: Pinellas National Wildlife Refuge and the refuge on Egmont Key. Most of the islands (including several man-made islands built from dredge spoil) and sandbars are off-limits to the public, due to their fragile ecology and their use as nesting sites by many species of birds. The Tampa Bay Estuary Program keeps watch over the Bay’s health.

Tampa Bay was once teeming with fish and wildlife. People of the Safety Harbor culture lived almost entirely from mullet, shellfish, sea turtles, manatees, crabs, and other bounties harvested from the sea. As late as the early 20th century, visitors still reported huge schools of mullet swimming across the bay in such numbers that they “impeded the passage of boats”.

The establishment and rapid growth of surrounding communities during the 20th century caused serious damage to the bay’s natural environment. Heavy harvesting of fish and other sea life, constant dredging of shipping channels, and the clearing of mangroves for shoreline development were important factors. Most damaging was the discharge of wastewater and other pollutants into the bay, which drastically degraded water quality. The bay’s health reached a low point in the 1970s. The water was so murky that sunlight could not reach the shallow bottom, reducing sea grass coverage by more than 80% compared to earlier in the century and severely impacting the marine ecosystem. Many previously common species became scarce, and bay beaches were regularly closed due to unsafe levels of bacteria and pollutants.

Beginning in the early 1980s after federal and state legislation to improve water quality, authorities installed improved water treatment plants and tightened regulation of industrial discharge, leading to slow but steady improvement in water quality and general ecological health. By 2010, measures of seagrass coverage, water clarity, and biodiversity had improved to levels last seen in the 1950s. However, industrial, and agricultural runoff along with runoff from developed areas pose a continuing threat to marine ecosystems in the bay, particularly by clouding the water with sediments and algae blooms, and seagrass coverage declined slightly in the late 2010s. Wastewater pollution from old phosphate plants near the shoreline has been a particular problem. For example, in 2004, a leak of 65 million gallons of acidic water from a Cargill phosphate plant on the bay’s southern shore severely impacted wetlands in the vicinity of the spill. And in April 2021, a breach of a wastewater reservoir at the long-closed Piney Point phosphate plant sent over 200 million gallons of nutrient-rich mine tailings streaming into lower Tampa Bay. The resulting growth of red tide alga led to ecocide (extensive ecological destruction which would have a significant consequence on Earth’s ecological systems) and killed over 1000 tons of fish in the bay and along the nearby gulf coast and may lead to further damage to seagrass beds. Tampa bay, like other parts of Florida, is extremely vulnerable to sea level rise caused by climate change. Already sea level has risen 8 inches since 1946. A category 5 Imagehurricane in Florida is of most concern in the Tampa Bay area, and climate related sea level rise of as little as six inches would exacerbate its impact. The Tampa Bay Regional Resiliency Coalition coordinates the region’s response to climate change. Communities throughout the Bay, including St. Petersburg, Florida and Tampa, Florida are adapting infrastructure and buildings to face changes in sea level.