With significant financial assistance from the Southwest Florida Water Management District, volunteers with Save Crystal River employed a suction dredge to remove benthic algae and organic sediments from areas within the canals and replanted those areas with cultivated eelgrass, first in manatee-exclusion cages, and later in open areas.
Unfortunately, two years after initial suction dredging and replanting, there was little evidence of recolonization of sea grasses. Noxious filamentous algae and low water clarity were still prevalent.
Fast forward to early November of this year. I was pleasantly surprised to see a very different sight — healthy eelgrass flourishing and expanding throughout Kings Bay and markedly improved water clarity. While eelgrass planting had been confined to the canals closest to Hunter and Three Sisters springs, plant community monitoring confirmed that eelgrass has fully colonized much larger areas in the open bay and river.
According to district scientists, by August 2020 these seagrass populations had expanded, followed by extensive grazing by the large manatee population last winter. By August of this year the eelgrass had rebounded to the pre-manatee season abundance. It appears that eelgrass re-establishment to levels that can withstand intense grazing by wintering manatees has been successful — at least for the time-being.
Eelgrass re-planting in Kings Bay and at other Florida locations has previously been attempted with little lasting success. As an aquatic ecologist interested in habitat restoration, I wish to understand why this recent effort was successful. If similar thriving eelgrass beds can be established in the Indian River Lagoon or in the lower St. Johns River, Florida’s starving east-coast manatees and other wildlife species dependent on healthy grass flats might also benefit.
While water quality in Kings Bay is an issue of concern, nutrient levels have not been reduced by recent state and local actions. Reduced nitrogen pollution is not the explanation for the recent eelgrass recovery in King’s Bay.
The Florida Springs Institute published the Kings Bay/Crystal River Springs Restoration Plan in 2016. That study noted that the most detrimental factor affecting the bay was the proliferation of free-floating micro-algae that reduced water clarity, reducing the light needed for seagrasses.
This algal bloom was directly attributed to reduced spring flows feeding the bay. Lower spring flows result in slower water flushing and in turn promote excessive phytoplankton growth and cloudy green water.
Existing flow data indicate that the 70-plus springs that feed Kings Bay have lost on average 58% of their historic flow. This flow loss was partly attributed to lower-than-average rainfall (13%), but increased groundwater pumping is the primary cause (45%). The lowest annual flow on record was recorded in 2012 at only 30% of the historic average flow.
While there has been no reduction in regional groundwater pumping over the past decade there has been higher than average rainfall since 2018. Average spring flows respond rapidly to increased rain and have shown a significant increase over this recent time frame. Increased flows lead to reduced phytoplanktonic algal growth and clearer water, environmental factors which provide favorable conditions for the survival and propagation of eelgrass.
This plausible explanation for eelgrass recovery in no way diminishes the success of the homeowners’ heroic restoration efforts. But it does present a cautionary note.
In 2018, the water management district passed a minimum flow for the Kings Bay springs that allows groundwater pumping to be increased. In the absence of above-average rainfall, Crystal River’s long-term average spring flows will continue to decline as long as additional groundwater withdrawal permits are issued. Reduced flows will promote algal blooms, shade out the eelgrass plant community, and result in the return of green and cloudy water.
Lasting Kings Bay restoration will only be achieved by significantly reducing groundwater pumping. Healthy, flowing springs are the lifeblood of the Florida manatee and Crystal River’s economic future.
