2024 SAVe OUR RIVER'S GRASSES EXPEDITION

Submerged aquatic vegetation (SAV) is the foundation of our river’s health – providing biofiltration, habitat & food for both commercial & recreational aquatic species, erosion protection, oxygenation of the water column, carbon sequestration & storage, and more. Unfortunately, the St. Johns River SAV is suffering mounting threats and stress resulting in the near demise of our river’s submerged grasses much to the alarm of scientists, fishermen, homeowners and river enthusiasts.

In May 2023, St. Johns Riverkeeper launched its SAVe Our River’s Grasses Expedition seeking answers and solutions to the disappearing SAV of the St. Johns. Over several days during each expedition field visit, our team surveys an 80-mile stretch of the river between Doctors Lake and Lake George searching for remaining grass beds, taking measurements, conducting water quality testing, and seeking solutions to restore this vital habitat.

We meet with riverfront residents, fishermen, scientists and community leaders to enhance our data collection by the observations of those who have lived on, explored, fished, or studied our river for decades.

This Story Map captures our 2024 Expedition which includes our findings, significance, and steps forward. We will continue to return to the field throughout the SAV growing season (March – October) each year for a total of five years in order to identify solutions to reverse this devastating loss of SAV.

Over four days, our team surveys 14 sites along an 80-mile stretch of river between Doctors Lake and Lake George. We identify remaining grass beds, collect detailed measurements, conduct water quality tests, and explore potential solutions to restore this essential habitat.

• Every monitoring site along the 80-mile expedition route had submerged aquatic vegetation (SAV).
• At several sites, grass lengths were observed to be longer than they were in 2023, and there appeared to be an improvement in canopy heights
• This year, the team discovered a greater diversity of grasses, encountering species not observed in 2023. Newly encountered species include: Najas guadalupensis, Potamogeton pusillus, and Eleocharis sp.
• Chara sp., an SAV that is actually a macroalgae, was still dominant at the Welaka and Georgetown sites. It was also discovered further north in East Palatka. Chara is considered to be a precursor species to eelgrass and other SAV species.
• An Exciting highlight from the May 2024 Expedition was the presence of long, healthy grasses within the temporary enclosures at Dancy Point and San Mateo that are part of the Florida Fish and Wildlife (FWC) agency pilot project. FWC has been installing temporary fencing to protect grasses from grazing wildlife, giving our river’s SAV a fighting chance. Once the grass beds are reestablished, the enclosures will be removed. Outside the Dancy Point enclosure, SAV was cropped like all the other unprotected areas, demonstrating the significant grazing pressure that makes it difficult for grass beds to grow and thrive.

SJRK’s August 2024 Expedition yielded mixed results, presenting both encouraging and discouraging findings:

• Canopy heights have improved at two sites since May of this year and at three sites since last August.
• Water temperatures were noticeably warmer, with elevated readings at seven sites compared to August 2023. Eelgrass does not tolerate excessively high temperatures well. Studies have shown that eelgrass thrives best in temperatures around 82°F. Four sites read in the mid-80s (84-85°F), while 10 sites ranged from the high 80s to low 90s (86-93.5°F).
• Chlorophyll-a indicates the concentration of algae in a waterbody. Eleven out of the 14 sites exceeded the healthy parameter for Chlorophyll-a, which should be less than or equal to 5.4 micrograms per liter (µg/L). 
• Similar to August 2023, seven of our 14 SAV sites had potentially toxic cyanobacteria present and prevented our team from entering the water following safety protocols. Cyanobacteria, a/k/a harmful algal blooms (HAB), can be highly toxic and dangerous to human health. Lab results revealed the presence of at least three types of potentially toxic cyanobacteria in the samples analyzed. 
• SAV was found at all the surveyed sites that were accessible.
• Grazing pressure from aquatic species continues to be a major stressor affecting the recovery of SAV, as evidenced by the sparse and heavily cropped grasses that were observed compared to that of the SAV within the protective enclosures.

• At Dancy Point, SAV density has improved both inside and outside the protective enclosure since May, while canopy heights inside the enclosure have seen a remarkable increase compared to last August. The average height measured 50 cm, a significant rise from last year’s average of just 6.3 cm. Some blades of SAV grew to nearly a meter in length.

• There was an alarming loss of SAV along the expedition route due to back-to-back hurricanes since our August field visit. 
• Consecutive hurricanes flooded the river with excess tannins from nearby swamps, transforming our blackwater river from iced tea clarity to a coffee-like opacity. These conditions block essential sunlight from reaching the river’s struggling eelgrass.
• Hurricane Milton’s floods were prolonged as its sustained northeasterly winds caused the river to reverse flow for several days. Downstream water levels remain elevated due to the slow flow of the St. Johns and seasonal king tides that increase tide levels by 1-2 feet. 
• The protective enclosure that was located at Dancy Point in East Palatka was compromised in early September. The eel grass that was reaching historic conditions was reduced to stubble succumbing to grazer pressure in approximately three weeks. 
• Post-storm conditions further complicated our survey efforts.
• Six of our 14 sites were inaccessible due to high, choppy water, and one site was inaccessible because of the presence of potentially toxic blue-green algae.
• At the accessible sites, we measured water depth and SAV using a modified survey method due to high, dark water. At Dancy Point, we conducted a full survey with consistent methods from past visits to capture conditions before and after the fence breach.

• FINDINGS FROM THE SEVEN ACCESSIBLE SITES :
• Average depths from each site were 66.1 cm - 112.7 cm.
• Average water temperatures were in the mid to low 70s, averaging 74°F

OPEN SITES:

• Average canopy heights ranged from 2-2.89 cm
• Average grass bed density ranged from 0%-34%

PROTECTED SITES:

• Average canopy heights of 10.5 cm
• Average grass bed density 67%

Our last visit for 2024 in October was a stark reminder that much more needs to be done to give our river’s grasses a fighting chance. 

We are consolidating data from our three 2024 field surveys, integrating additional agency data, and developing recommendations for advancing the restoration and protection of SAV in the St. Johns River. 

This effort would not be possible without the support of hosting riverfront residents and their neighbors, advising scientists, community leaders, anglers, and all those who care for the river.

Once finalized permits are received, we will install protective enclosures along our expedition route that will provide temporary relief for SAV from grazing pressures. While the enclosures are not the solution, they will provide valuable data as we search for long-term strategies to restore the river’s grasses.

To make this a reality, we appreciate the generous support of the Coastal Conservation Association (CCA) and Mighty River Recovery. Their dedication in conserving and restoring fish habitat aligns with our shared goal of the SAVe Our River’s Grasses Expedition.

Together, we are making a difference.

For The River. For Us All.