As Vanessa McDonough scanned the ocean floor off the South Florida coast, she spotted an empty beer bottle among the fish, corals, and sponges protected by Biscayne National Park. Only the bottle wasn’t empty. Upon closer examination, a small fish had swam inside, and pebbles and shells had blocked the exit.
“The poor fish was a prisoner in this Corona bottle,” she said.
That fish was granted a reprieve, as Mrs. McDonough set it free before removing the bottle from the seabed, but other underwater organisms haven’t been so lucky.
No one knows how much debris from humans is littered about Biscayne’s marine ecosystem, so park scientists have begun a study to document and clean up trash from the ocean floor in hopes of improving the environment and gaining a better understanding of where garbage accumulates. With global warming and disease already impacting the health of the park's coral reefs, debris from humans adds another threat to this delicate ecosystem, so they’re also tracking injuries and mortalities.
“The corals are already struggling,” Mrs. McDonough, a fishery and wildlife biologist at the park since 2007, said during a phone interview. “Then you throw a 50-pound anchor at them, and it’s not a pretty picture.”
Yes, anchors. “More anchors than I can count,” she said. Plus lobster traps, fishing weights, monofilament line, bottle caps, fishing weights, and so much more.
Every year, a half-million people flock to Biscayne, many to dive or snorkel among the colorful fish and coral reefs that are unique to the area. The largest marine park in the National Park System, more than 95 percent of Biscayne is covered by water. Boating and fishing are also popular activities, and that appears to be the source of much of the marine trash, with decades of accumulation from commercial trapping and recreational fishing.
The need for the study became clear while biologists were diving late last year to track lionfish, an invasive species, along Biscayne’s eastern boundary – where the ocean floor drops from 60 to 100 feet, and where a lot of boaters and fishermen congregate.
“It became painfully obvious how much garbage is down there,” Mrs. McDonough said.
In addition, a no-fishing Marine Reserve Zone, where only snorkeling and diving would be allowed, is included in the park’s recently approved General Management Plan. From a preservation perspective, the designation would aid in recovering fisheries and improve the health of the only tropical coral reef system in the continental United States. From a recreational standpoint, snorkelers and divers could admire the wildlife without garbage marring the experience.
The park selected 12 sites – six within the proposed Marine Reserve Zone and six outside -- to study. Each zone is 100 meters long by 10 meters wide. Three divers split up each area, spending about an hour going back and forth over the site at least two times. They scrutinize every part of the reef, in the process documenting the debris and injuries, and then removing what they can.
“If they’ve (debris) become overgrown with stony corals, for example, we don’t want to do more harm than good by taking them out of the environment and killing the corals, so we’ll just note their location and leave them there,” Mrs. McDonough said.
Sponges can grow through abandoned trap line, so “strategic cutting” could be necessary. A bit of the line would be left in the sponge, but cutting around the edges removes, for instance, 50 feet of line on each side that would have been pulled with tidal movement.
The scientists will return to each zone every three months to understand the different types of debris, how much there is, and how much damage it’s causing.
“From that, we’ll be able to calculate accumulation rates – how quickly is garbage regenerating there – and hopefully compare if garbage is accumulating at a slower scale within the Marine Reserve Zone where people won’t be fishing,” Mrs. McDonough said.
The park has completed its first dive at just half of the sites and already has collected 306 pounds (139 kilograms) of debris.
“It’s always hard to wrap your head around that because a lot of times also we’re picking up so much monofilament, and that doesn’t have mass, so you don’t get the essence of that,” Mrs. McDonough said. “But that includes things like anchors and lobster traps that are very heavy.”
So far, 750 individual impacts on organisms have been observed, including more than 400 sponges, as well as a lot of soft corals.
“More injuries than deaths, but we are documenting mortalities as well,” she said.
This information can assist park managers in determining where and how frequently reef cleanup efforts should occur. Biscayne does not have an ongoing debris removal program. Currently, some of the money collected as fines from boaters who run aground in the park is directed to habitat restoration that’s carried out by contractors. But it’s not a substantial amount of money, so most of the seafloor hasn’t been touched.
For the new study, park staff are adjusting their schedules, and it’s “turning out to be a pretty large effort.” In order to cover two zones in one day, half of the 12 people in the resource management division are required since the same three people can’t dive both areas without concern about decompression sickness.
“We’re doing it, but it comes at a cost of other things that we’re unable to do,” Mrs. McDonough said.
Biscayne offers guidelines to visitors for preventing and picking up debris. While boating, never intentionally dispose of garbage by tossing it overboard. Instead, keep trash confined and secured to prevent it from unintentionally getting blown or otherwise dumped overboard. Trash observed in a marine environment can be removed as long as it is safe to do so. (Gloves will help protect against rusty edges, sharp points, and stinging critters that settle on the debris). Large-scale occurrences of marine debris should be reported to the park, with the precise location.
And those actions are important because, while items from all over the world are found during shoreline cleanups, most of the debris below the ocean surface is from people who are using the park, such as fishermen who toss a beer bottle overboard.
“Unfortunately,” Mrs. McDonough said, “the stuff that’s underwater is from the local users.”