Environment

Where is bay pollution coming from? Scientists turn to the currents

In mangroves behind Vizcaya, plastic bottles, tampon applicators and bits of styrofoam regularly get trapped in the tangle of roots as if captured in a storm drain. Out the mouth of the Miami River and across Biscayne Bay on Miami Beach, stormwater flushes human and animal wastes and an array of foul stuff. On Virginia Key, a vial of blood sticks out of the sand.

How trash gets there and where that and other pollution flows around Biscayne Bay remain largely a mystery. But now a team of University of Miami scientists think they may know how to find the answer.

Using technology developed to track the Deepwater Horizon oil spill in the Gulf of Mexico, the researchers have teamed up with school kids and local museums to track the complex network of micro currents that crisscross the bay, spreading trash and pollution. While they concede the project is just a beginning, they hope mapping the currents will help inform government planners as they tackle a host of increasing threats to the urban but still vital bay — from flooding tied to rising seas to bigger ships sailing through the Panama Canal.

“We actually know very little because the geometry is so complicated,” said Rosenstiel School of Marine and Atmospheric Science oceanographer Tamay Özgökmen, who leads a consortium of 40 scientists from 14 universities studying the BP spill.

“Does it flush to the ocean or does it just stay where people live for a long time and then you have to worry about bacteria and all kinds of health issues?” he said. “Not flushing is not good.”

On Monday, Özgökmen’s team released 15 sensors specifically designed to measure currents at the surface of the water, where wind and waves can whip around much faster than deeper currents. The sensors — floating white rings attached to an underwater foot-wide pinwheel — include a small GPS tracker that lets the team calculate the speed and path of currents. While the technology seems simple, it took three scientists two years to come up with a device that was light, compact, biodegradable (the plastic was developed by MIT scientists for beach toys) and capable of separating the forces of waves, wind and ocean currents.

 
Tamay Ozgokmen / University of Miami

Özgökmen used the same technology when his team released 1,100 sensors across the Gulf to map the BP spill in an ongoing $20 million study to help predict the path future oil spills.

The sensors or “drifters” will be released every three months. An initial plotting Tuesday confirmed that the currents do indeed create a complex pattern, with swirling pockets and longer loops that hug shores. Five sensors dropped between Star Island and Miami Beach’s new drainage outfall pipes connected to massive pumps bounced back and forth like they were trapped in a mixing bowl.

Currents often act as the ocean’s mixer, helping spread and eventually dilute pollution. But increasingly, scientists understand that smaller local currents play a role equally important to larger forces like the Florida Current and Loop Current in the Gulf. They also believe existing ocean models don’t reflect their complexity. And in Biscayne Bay, with its ragged coastline, patchwork of islands and shallow seagrass banks, currents can become even more intricate with a profound effect on how pollution spreads.

“If it’s mixing with a lot of water, [it dilutes]. But there’s a lot of places where it’s not mixing. It just sits there and it doesn’t go anywhere,” Özgökmen said. “You can imagine if you put it in a hole, it’s going to concentrate.”

And that can make all the difference in deciding where to place stormwater outfall pipes or construct other solutions to deal with rising seas.

“The solution to one problem can often lead to another problem,” said UM marine anthropologist Kenny Broad, who studies how humans interact with the environment. “Everybody looks at the ocean and land as disconnected, but it’s really an interlinked system.”

The idea for the study came from a simple complaint: the never-ending wave of trash that washes up in mangroves along the mainland Miami shoreline. After repeatedly tossing around ideas during coastal clean-ups, Frost Science Museum restoration coordinator Chelle King said it finally dawned on her to approach UM, where Laura Bracken was working as outreach coordinator for Özgökmen’s team, the Consortium for Advanced Research on Transport of Hydrocarbon in the Environment (CARTHE).

“If we don’t tackle this from the root, it’s not a real solution,” said Vizcaya Museum & Garden schools program manager Diana Pena. “We’re hoping this information gives us enough to reach out to the public and realize how important they are to environmental stewardship.”

The project seemed like a perfect way to apply advanced research on a remote problem to solving a local issue. So in addition to the sensors, the team recruited volunteers — from school kids to seniors — to paint floating drift cards and released 320 Monday. The cards provide help drum up support by asking each finder to report its location and upload a photo to Instagram labeled #BayDrift.

“We’re not saying it should be this way or the other. We’re saying just look at it,” Özgökmen said. “This is just the start of trouble. The more human beings, the more we’re consuming, there’s constantly pressure and that pressure is not going away. It’s something we need to deal with.”

Follow Jenny Staletovich on Twitter @jenstaletovich

DRIFT CARDS

Scientists are hoping to collect additional information about Biscayne Bay’s ciculations through 320 drift cards released on Monday. Instructions for reporting are on each card. Finders are asked to report the location, date and time of a find via Instagram labeled #BayDrift or email BayDriftMiami@gmail.com.

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