Like scientists seeking to unravel the mysteries of deep space to understand what lies beyond, a growing number of super-sleuths are turning their attention and sophisticated instruments on Tampa Bay. Already one of the world’s best-studied estuaries, the bay’s significance as a laboratory for marine research is growing. New monitoring efforts are expected to uncover even more details about the way the bay works – how healthy it is, how it responds under pressure and what happens when actions are taken to relieve those pressures.
All this probing, trawling, sampling and mapping not only provides a better understanding of our region’s most precious asset, it’s critical to bay management and protection efforts. Consider the plight of Tampa Bay back in the 1960s. Foul water was killing fish and seagrasses but the causes were unknown. A comprehensive study conducted then is believed to be the first ever to document the devastating effects on estuaries of excess nitrogen, which can spark massive algal blooms and rob the water of life-giving oxygen and sunlight.
That pioneering investigation led to improvements in sewage treatment that are credited with sparking the bay’s remarkable rebound. “It was really a keystone study for the world because people had ideas about what caused the problems, but it had never been clearly shown before,” said Roger Johansson, chief biologist for the City of Tampa’s Bay Study Group.
Studies begun in the 1970s by the Hillsborough County Environmental Protection Commission (EPC) created a water quality database that’s “unparalleled anywhere else in the world,” according to Holly Greening, senior scientist with the Tampa Bay Estuary Program. “Roger Stewart (former EPC chief) and Tom Cardinale have built an incredible gold mine of water quality data that is consistent over the last 30 years.”
Along with committed scientists who pushed for studies before other areas did, Tampa Bay benefits because it’s a relatively small system when compared to other estuaries. “It’s a scaled-down version, but the same processes occur here as in the larger systems,” says Dr. Ernst Peebles, a nationally recognized researcher who came to the University of South Florida from Louisiana in 1983 to earn a master’s degree in marine science – and never left. “The tractable size makes it much easier to study than the Chesapeake Bay, North Carolina or Louisiana.”
Monitoring programs underway at the local, regional and national level promise to help managers document impacts on the dynamic system, plus provide an early warning system to prompt changes if bay resources are threatened.
USGS selects Tampa Bay for pilot program
The opportunity to work with local scientists, plus the long-term database already in place, was a key consideration when the U.S. Geological Survey (USGS) decided to use Tampa Bay for its pilot program, notes Kim Yates, scientific project leader.
“We didn’t have to start from scratch,” she said. The five-year multidisciplinary effort is the first time scientists from all four USGS disciplines – geology, biological resources, water resources and mapping – have formed a fully integrated team. “We worked with the Tampa Bay Estuary Program and other agencies to determine where the research gaps were and how we could help, particularly how we could learn more about the bay as a system rather than collecting little pieces of data.”
One priority, for example, is figuring out how much ground water enters the bay because it affects both the bay’s salinity and nitrogen levels. To answer that question, USGS is deploying experts to create a map that shows salinity levels from the water’s surface to 30 feet below the sea floor.
With low-salinity zones identified, a seismic mapping team can identify karst features, sediment layers and other structures that would allow ground water to seep into the bay. Finally, chemists test the water for specific properties, ranging from radioisotopes and complex chemistry to nutrient and heavy metal content, “basically anything you could want to know,” Yates said.
The multidisciplinary approach also may yield new answers about wetlands and how they work. A team of biologists looks at fish populations and conditions, while botanists review the productivity of mangroves and other plants. If the botanists and biologists discover problems, a team of chemists could assess the effect of contaminants in water or sediments.
At the same time, geologists will determine which underground structures exist, the extent of saltwater intrusion and the potential for changes in surface elevations if underground water levels fluctuate. Archeologists work with the geologists to identify shell middens – typically placed at water’s edge – that indicate historic sea levels.
Even prehistoric data is important to the study. Another project collected samples that indicate Tampa Bay may have originally started life as a giant sinkhole that became a freshwater lake before the sea broke through. “If we know how it looked in the past, we can build models that use that information to validate what may happen in the future,” Yates said.
Beyond modeling
The limitations of modeling are emphasized by Hillsborough County’s ongoing concerns about the impact of Tampa Bay Water’s desalination plant and surface water withdrawals. Although models indicate no adverse impacts on natural resources, Hillsborough County established an intensive – and independent – monitoring program to ensure that those predictions hold true.
Baseline data from impacted rivers – including the Alafia, Hillsborough and Palm – has been collected since 1999. “We’ve been fortunate to have been able to measure extremes on both ends,” says Scott Emery, a consultant who helped design the independent monitoring program. “We had record rainfall with El Ni–o, and then record drought so we have good baseline data.”
Samples are collected during August and September, the hottest, rainiest months of the year – when organisms are most likely to be stressed. Bobbing on a small boat, scientists scoop sediment from the bay floor and measure basic water parameters using a sensor linked to an onboard laptop computer.
Sites – including 30 on the Hillsborough River, 43 on the Alafia and 60 near Big Bend where the world’s largest desalination plant will open later this year – are selected randomly so results are statistically valid for the entire waterbody. At five locations, sophisticated electronic sensors are dropped overboard where they measure water parameters every 15 minutes until they’re retrieved 24 hours later.
The area nearest the new desal plant will have more permanent monitoring stations per square mile than anywhere else in the bay, said Cardinale, assistant director of EPC’s water management division. “We’re hoping that we don’t see a measurable change, but you never know. Part of our concern is the cumulative effect – if we get lots of rain, the impact of desal probably won’t even be detected, but combined with dry conditions it could aggravate the situation.”
Along with water quality, EPC monitors the health, variety and abundance of benthic communities. Bottom-dwelling creatures – including crabs, shrimp and starfish as well as microscopic animals – are important because they help measure the impact of biological changes in water quality and salinity. They also are important food sources for more visible bay creatures, including fish and birds.
“Most of these critters live in specific zones, so we measure the type and abundance of animals in a sample,” said Stephen Grabe, environmental supervisor at the EPCHC. “The tricky part is figuring the optimal salinity for them – for instance, they may live in zones that range from 20 to 32 parts per thousand [salinity] but actually prefer 25 parts per thousand.”
To address that challenge, EPC measures benthos on a curve that shows where they appear less frequently in areas with low levels of salt, more frequently in their optimal zone and then less frequently again in high-salinity zones. They’ll also compare changes near Apollo Beach and in the Alafia River to changes in the Little Manatee River so natural fluctuations caused by rainfall can be discerned from human alterations.
Monitoring hydro-biological conditions
County monitoring initiatives are supplemented by the region’s largest water supplier, Tampa Bay Water, which spends a million dollars per year on hydro-biological monitoring as a condition of permitting for its surface water withdrawals (see lead story).
A key element in that program is monitoring low-salinity habitats. At USF, Peebles heads a team of scientists who trawl local rivers at night pulling a sample net. Aquatic animals – ranging from shrimp and crabs to juvenile redfish and sea trout – are divided by size and species and counted to determine current population. That data is correlated with salinity, season and flow levels.
Even before new potable water projects come online, fluctuations in freshwater inflow may range as high as 75 percent from year to year, Peebles notes. “It’s the difference between El Ni–o rains and La Ni–a drought. We’ve known for years that La Ni–a is bad for the production of estuarine fish and crabs, but there really isn’t anything to do about it.”
Seagrass monitoring critical
While many of the new monitoring initiatives focus on potential damage, ongoing efforts also highlight the results of positive actions. For instance, baseline studies that showed less than a half-acre of seagrass in Hillsborough Bay prior to the completion of an advanced wastewater treatment plant in 1979 now indicate more than 200 acres of vegetation are thriving in Hillsborough Bay. “We could show that the regrowth was directly attributable to water quality changes and the abatement of nutrient loading,” notes Walt Avery, a biologist at the Bay Study Group and an active member of the TBEP Seagrass Working Group.
Still, more recent seagrass studies indicate that the valuable habitat is not recovering as quickly as managers expected in some areas of the bay, so more intensive monitoring is underway. “We now know that nutrient control is the most important factor affecting seagrasses on a baywide basis, but it isn’t the only thing in every bay segment,” Greening notes. Some sites where seagrasses should be growing are still barren, and scientists are working to determine how other factors – including wave energy, color of the water and even natural disturbances caused by stingrays – impact seagrass growth.
Intense monitoring of six sites across the bay – four problem areas and two reference sites – began early this year and will run for 18 months. Two of those problem areas border Pinellas County – Feather Sound near the Howard Frankland Bridge and Coffeepot Bayou in St. Petersburg, said Andy Squires, environmental program manager for Pinellas County. Working with USGS, the county’s Water Resource Management Section is conducting a series of studies at Feather Sound to update bathymetric data, measure changes in seagrass growth and compare water clarity in different sections of Old Tampa Bay.
Across Tampa Bay, seagrasses are monitored by snorkelers who dive to preset transects and count the number of blades, plus note the species, epiphyte and algae coverage and measure light levels. Intensive efforts also are underway at Shell Key where 200 transects are being monitored as part of a plan that calls for limiting internal combustion engines to protect seagrasses and manatees.
Other monitoring programs created 10 years ago to help set priorities for developing watershed management programs are being revamped to emphasize new state standards for water quality. Those standards call for stringent load restrictions in “impaired” waters so they can recover sufficiently to be safe for fishing and swimming, Squires said. “We expect the list of impaired waters to be very similar to the priority list we’re already working on,” he adds.
Fast-growing Manatee County facing pressure
In Manatee County, monitoring activities focus on ambient water quality and seagrass growth. More recently, the county has been monitoring Bishop Harbor where discharges from an abandoned fertilizer plant carried more than 16 million tons of nitrogen last year.
Large developments planned for both sides of the Manatee River – which has traditionally been used for agriculture – also are creating new challenges, said Rob Brown, administrator for air and water quality in Manatee County. “There’s a lot of pressure for development with minimum buffers,” he said. “Plus everyone wants a boat ramp, and manatee protection has become a big issue.”
With two large rivers – the Manatee and the Braden – dammed to create reservoirs, the county’s potable water supplies aren’t as much an issue as they are in other parts of Tampa Bay. “The Manatee River is just an extension of Tampa Bay with similar habitats up to I-75,” Brown said. “The water supply system gets the highest priority, but we do have to make minimum releases.”