Salinity Monitoring 2024 2nd Quarter Report (2024)

Introduction

The Pensacola Bay System has had a history of environmental problems. Declining water quality, loss of habitat, and the decline of fisheries and wildlife have all been problems for the bay.

One area of interest for Florida Sea Grant has been the status of our seagrasses and bay scallop. Based on a 2016 report from the U.S. Environmental Protection Agency seagrasses in the bay system began declining in the 1950s. There were 9,530 acres reported in 1960. Currently the acreage is estimated to be between 4000-5000. Many around the state have tried restoring seagrasses with little success. However, there has been success with natural seagrass recruitment and restoration when the environmental stressors that initiated the decline were removed. Florida Sea Grant is currently partnering with the University of West Florida to monitor the state of seagrass within the bay area to determine whether it is restoring on its own. Turtle grass (Thalassia testudinum) is a species of particular interest due to its relationship with the life cycle of the bay scallop.

Bay scallops (Argopecten irradians) began to decline within the bay system at about the same time as the seagrass. A variety of factors were probably to blame for the decline of both populations. Increased nutrients spawned the growth of drift algae that covered the seagrass blocking needed sunlight. The run-off that brought the nutrients also brought suspended solids that decreased water clarity which also blocked needed sunlight. Overharvesting of bay scallops mostly likely played a role as well.

One environmental parameter to be monitored is salinity. Both turtle grass and bay scallops need the salinity to be at, or above, 20 parts per thousand (ppt). In recent years the annual rainfall in the area has increased. Along with this has been an increase in development leading to an increase in stormwater run-off into the bay. One question we are looking at is whether the increase in freshwater run-off has decreased the salinity nearshore to levels that would not support either turtle grass or bay scallop restoration.

Method

Florida Sea Grant trained local residents how to monitor the salinity using a refractometer. Participating volunteers were asked to monitor their assigned location once a week for a total of 100 readings (about two years). The data was logged by the Sea Grant Extension Agent and the central tendency of the data (mean, median, and mode) were calculated.

Data

The Big Lagoon Area

The Santa Rosa Sound Area

The Downtown Pensacola Area

Results

Big Lagoon Area

9 sites have been monitored in the Big Lagoon area. 5 of those have reached the 100-reading mark. 3 of those 5 sites have salinities at or above 20 ppt.

Of the remaining 4 sites, 1 (Perdido Key State Park) is at 95 readings. The remaining 3 sites have not been monitored in a while.

Santa Rosa Sound Area

4 sites have been monitored in the Santa Rosa Sound area. 2 of those have reached the 100-reading mark.

Both of those sites are at, or above, 20 ppt. The remaining 2 are both actively being monitored and are near their 100-reading mark.

Downtown Pensacola Area

9 sites have been monitored in the Downtown Pensacola Area. 2 of those have reached the 100-reading mark.

One of those, Sanders Beach, is at, or above, 20 ppt. The other, Bayou Texar, is not.

Of the remaining 7 sites, only Hawkshaw is actively being monitored.

Discussion

The Big Lagoon area has the highest number of actively monitored sites, as well as the highest number of sites that have reached the 100-reading mark. Those monitored in Big Lagoon and the Intracoastal Waterway have salinities high enough to support both turtle grass and scallops. Lower Perdido Bay did not, but it is not believed that historically it did either. One site of interest was within Big Lagoon State Park. This site did reach the 100-reading mark, but the central tendency of the data was between 15-18 ppt. The mean for that site was 18 ppt ±7.5. It ranged between 0-30 ppt. A closer look at this site is needed but the large variation suggests impacts from run-off.

Though there are fewer sites monitored in Santa Rosa Sound all are currently at, or above, 20 ppt. This suggests that this body of water can support both turtle grass and bay scallop restoration.

There is no literature that suggests either turtle grass or bay scallops historically existed in the downtown Pensacola area. Other than Sanders Beach, the salinity data does not support this either. That said, our Eyes on Seagrass monitoring project has found seagrass growing there. The species found is widgeon grass (Ruppia maritima) with some shoal grass (Halodule wrightii). Both these species can tolerate lower salinity.

The 2024 3^rd quarter report will be posted in October.

Reference

Lewis, M., J.T. Kirschenfeld, T. Goodhart. Environmental Quality of the Pensacola Bay System: Retrospective Review for Future Resource Management and Rehabilitation. U.S. Environmental Protection Agency, Gulf Breeze FL, EPA/600/R-16/169, 2016.

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