ORANGE PARK — The “Kingfisher” cut through the waves on Doctors Lake early Tuesday morning. Lisa Rinaman of the St. Johns Riverkeeper, an environmental advocacy group, waved to the residents who gathered along the bulkhead of a private Orange Park property.

The residents were united by a mutual, grassroots concern for the eelgrasses of Doctors Lake, an inlet of the St. Johns River that has suffered from toxic algae blooms and environmental degradation.

One resident claimed to have recently seen manatees in the water. They said they even had proof — a video they had taken of two manatees mating — and offered to show it if anyone wanted to. This was taken optimistically among the crowd, that the eelgrass beds may be returning.

This was confirmed when the SJRK waded into the water to take measurements.

"We found eelgrass,” Rinaman said.

Rinaman and other members of the SJRK voyaged from Jacksonville to measure the submerged aquatic vegetation (SAV) along the Doctors Lake shoreline in Orange Park. It was also an opportunity to collect water and sediment samples for testing.

Last Tuesday's voyage marked the second trip of the second year of the SJRK’s “SAVe Our River’s Grasses Expedition.”

Submerged grass beds are vital to the ecology of Doctors Lake and throughout St. Johns, Florida’s longest river. Rinaman calls eelgrasses “kidneys of the river” due to their biofiltering properties, and they serve as a crucial ecological link. The grass beds are homes for fish and a significant food source for Florida’s beloved marine mammal, the manatee.

Eelgrasses and other SAVs are threatened by algae blooms, which outcompete grasses for nutrients and sunlight. Algae blooms are like aquatic, viscous weeds that can potentially be toxic — which, in Doctors Lake's case, were multiple times this past summer.

“One of our safety protocols is we always make sure there are no visible signs of algae. If there are, we don't get in the river. But we'll take samples and test for toxins from cyanobacteria,” Rinaman said.

The SJRK measures “anything the river will give”: salinity, dissolved oxygen, water temperature, air temperature, pH (acidity), turbidity (clarity) and chlorophyll a. The data is compiled throughout the St. Johns, analyzed and used to paint a picture of the river's overall health.  

These confounding variables contribute to eelgrass growth or decay. But based on the most recent observation in Doctors Lake, eelgrass beds have been growing longer and spreading out further. This is a remarkable improvement, considering the first SAV expedition to Doctors Lake was disappointing. No SAV was observed. 

“There was no grass at all. The salinity was much higher," Rinaman said. "But now, we are seeing more grasses, and I am happy to report all the neighbors who joined us today mentioned manatees being out here. That's exactly what we want to see: Lots of grass. Lots of fish. Lots of manatees."

Long, slender eelgrass leaves may be a sign that the tide may be changing for Doctors Lake — changing color, that is. The shoreline has frequently festered a green hue all summer due to toxic algae blooms. Promisingly, eelgrass and other SAVs can absorb excess nutrients, such as phosphorous, from the water. This has the potential to prevent the blooms from cropping up in the first place. 

Indeed, the future health of Doctors Lake may depend on its recovering, vital underwater lawn.