Piazza San Marco in Venice is a bustling tourist destination drowning in history. And about a dozen times a year the historic landmark also drowns under a foot or two of tidewater.

Though the northern Italian island is commonly referred to as the “sinking city” of Venice, that is somewhat of a misnomer. Built upon wooden pylons, the city had been sinking due to damage done by aquifers built in the early 20th century.

Now, there’s a bigger problem in the rising tides of the lagoon that surrounds the island. Between the two factors, Venice is disappearing by about one to three millimeters each year.

Hoping to save the city from the fate of Atlantis, the Italian government convened a group of experts, and so was born the Modulo Sperimentale Elettromeccanico (Experimental Electromechanical Module), better known as the MOSE project.

Flooded Piazza San Marco. Photo by Francesco Maicu.

The MOSE project consists of 79 movable tidal barriers at Venice’s two main access points to the Adriatic Sea. During times of high tidal waters, the barriers would close to prevent flooding.

However, scientists are concerned that as the barriers reduce flooding, they will also hinder the critical tidal flushing of the historic lagoon canals, exacerbating sewage pollution problems.

Enter San Diego State University public health professor Rick Gersberg, who has been working with researchers from around the world to address the potential problems of this €5 billion project.

A recognized expert in water quality, Gersberg was tasked with determining just how bad the pollution levels could get in the Venetian canals. He is the first limnologist (specialist in inland waters – both fresh and saline) to do this kind of research in Venice.

Not So Pretty Under Water

Gersberg started by determining the current levels of pollution in the lagoon canals and nearby Lido beach. He found that one of the most romantic cities in the world is anything but when viewed from beneath the surface.

“Because Venice is made up of several small islands, there is no sewage system; residents just dump their raw sewage right into the canals,” Gersberg said. “Today, the tides come twice a day and flush everything out to sea, but with the barriers cutting off the tide, everything would just sit there.”

Venice. Photo courtesy of Al Zirino.

Over the course of three summers from 2003-2005, Gersberg spent weeks in Venice taking water samples. The results, which were published last year in the journal Water Research, did not paint a pretty picture.

Gersberg found that 78 percent of the Venice lagoon canals tested positive for both hepatitis A viruses and enteroviruses, which cause common gastrointestinal illnesses. At Venice’s beach island of Lido, a popular swimming spot separating the Venice lagoon from the Adriatic Sea, hepatitis A wasn’t detected, but enteroviruses were found in all samples.

“Right now, pollution in the Venetian canals is below European health standards, and pollution at Lido beach is just near the acceptable levels,” Gersberg said. “When the barriers are closed, we expect to see an increase in contamination. How bad it gets will depend on how often they are closed.”

The Bigger Picture

No matter what the research shows, construction on the vastly debated MOSE project continues and should be done in less than five years.

In the meantime, European scientists are relying on Gersberg to pinpoint the prospective hazards of more frequent exposure to the flood waters around Venice.

Rick Gersberg, professor, SDSU Graduate
School of Public Health.

With Gersberg’s research as the benchmark, local environmental consultant Al Zirino is creating a computer model of the canals to examine the potential problems. These could include a lack of oxygen and nutrients in the water and an increase in toxins and viruses.

Zirino’s model will mimic water flow and all of the physical processes that play into the change in water levels and water quality. In the worst global warming scenario, which could occur in less than 100 years, the barriers would have to close up to 100 days each year, Zirino said.

Life Without Venice?

Though more than half of the population has moved out of Venice since 1930, the city remains a huge tourist destination. On an average day, more than 150,000 tourists wander its streets and explore its canals, stopping to see the Doges’ Palace, Piazza San Marco and the adjacent island of Murano.

Critics have been protesting the MOSE project since its inception. But with a lagoon that measures 10 times the size of San Diego bay, Venice has few alternatives, Zirino explained.

Continued flooding over a period of 10 years could further weaken buildings and, eventually, lead to their collapse.

“This project is critical,” said Zirino, an adjunct professor at SDSU. “Not building it would be disastrous for the city.”

SDSU’s Water Warrior

Gersberg’s research is not confined to Italy. It has stretched across the globe from Germany to Thailand and back home to San Diego, where he is director of the new SDSU Coastal Waters Lab.

A collaboration between SDSU and the U.S. Geological Survey, the lab will become a center for the development of programs that promote international collaboration in coastal zone and estuarine science

Gersberg’s research has also exposed potential health dangers lurking in waters at the San Diego-Mexico border. Currently, he is working with the City of San Diego to analyze runoff from the Point Loma wastewater treatment plant.

Gersberg with Refugio (Cuquis) Robles, a doctoral student
in ecology. Photo by Tom Farrington.

Though seemingly straightforward, the process of assessing water quality worldwide is fraught with controversy. Most countries base health standards on bacterial levels in the water, but much of Gersberg’s research focuses on viruses.

Bacteria have been shown to die off more quickly than many viruses. In order to measure the true human health risk in water, it is important to evaluate the viral levels as well, Gersberg said.

“The San Diego region's image and prosperity, as measured through tourism, is inextricably linked to beach water quality and the perception that we offer clean beaches,” Gersberg said. “My research offers a local resource for the best data and interpretation of what the real health risks are.”

Related information

• Gersberg 2007 Monty Award Video
• Coastal Waters Lab
• News Release: SDSU Study Detects Harmful Viruses in Local Coastal Waters
• Graduate School for Public Health

Credits

• Story by Gina Speciale
• Story edited by Coleen L. Geraghty
• Graphics by John Signer
• Photographs by Tom Farrington, Gina Speciale and Al Zirino