NOAA Leads restoration of seagrass meadow on the 55th anniversary of Earth Day.

By Scott Atwell

Restoration of a damaged seagrass meadow is underway in the Northwest Ship Channel off Key West, where a ferry boat damaged a large section of the seafloor after running aground and attempting to power off.  NOAA’s Florida Keys National Marine Sanctuary is overseeing the project, which is expected to last into June. Serendipitously, the start of the restoration coincides with Earth Day, which originated in 1970 to raise awareness about environmental issues.

The exposed area, within sight of Mallory Square, will be rehabilitated by filling the blow holes with up to 100 yards of pea gravel, and then laying out 14,000 sediment tubes, which are cotton bags filled with a mix of sand and gravel. Almost 2,000 planting units will then be inserted into the tubes, along with fertilizer spikes. “Our team will harvest manatee grass and shoal grass from nearby donor beds,” said Dr. Andy Risi of Sea & Shoreline, one of the contractors working on the project. “We will collect small, six-inch plugs of the seagrass and break them up into smaller groups of two to three seagrass shoots each, that will then get put into the sediment tubes with the fertilizer spikes.”

The ferry boat incident occurred in December of 2016, and the owner agreed to a financial settlement four years later. COVID-19 delayed restoration planning, and over time the damaged area expanded laterally, even as the holes filled with sand.  The Florida Keys ecosystem features 1.5 million acres of seagrass meadows—one of the world’s largest contiguous seagrass habitats—an important home for juvenile fish, lobsters, green sea turtles, queen conch, Bahama sea stars, manatees, and egrets among others.

This critical habitat is often found in shallow water, and when boaters are careless, seagrass is easily damaged by boat bottoms, propellers or, in the current restoration case, a jet propulsion system. “All boaters can make an Earth Day commitment by pledging to keep their bottom off the bottom,” said Lisa Symons, the sanctuary’s regional response coordinator, “and never, ever try to power off if you run aground, regardless of what size vessel you are operating. Please wait for high tide and call a salvor for assistance.  This limits the amount of injury to the corals, seagrasses and to vessels.”

Symons says the fertilizer spikes will be replaced every 90 days for a year and half, providing the plants with additional phosphorus, the main limiting nutrient for seagrass growth in the carbonate sediments of FKNMS. The spikes are a specific formulation of phosphorus and nitrogen that promotes growth of seagrass and not the proliferation of macroalgae or harmful algae associated with red tide events.  In waters with less current, NOAA and other partners can use bird stakes to increase the necessary nutrients for the seagrass.

Boaters will see a large barge and work boats at the site until late May or early June. “We would appreciate boaters in the area supporting the restoration by slowing down, so that the divers working on the project aren’t swamped by wakes,” said Symons. “In addition, the barge will be travelling from the work site to Stock Island every day for about four weeks.”

The sanctuary offers a free, online boater education course that can help vessel operators recognize the challenges of operating in Florida Keys waters, in addition to the Marine Sanctuary Explorer app, which provides QPS-enabled information about critical habitats.

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