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Situation
For decades resource managers and agencies have been interested in restoring seagrass in the Pensacola Bay system. Beginning in the mid-20th century seagrass habitat began to decline, in some locations over 80% were lost. This decline had been attributed to a variety of causes. Primarily stormwater run-off introducing sediment – which both decreases water clarity, blocking needed sunlight, and literally covering the grass. This stormwater also introduced excessive nutrients that supported plankton blooms, which also decreases water clarity, and supported the growth of epiphytic and drift algae – which smother the grasses reducing their light availability. To add to the problem boat propellers created deep scars in the grassbeds which can take up to a decade to restore themselves.
Along with the loss of seagrass, several estuarine creatures declined. Horseshoe crabs, sea urchins, and bay scallops to name three. Much of this was caused by declining water quality and loss of seagrass habitat, but in the case of the bay scallops – overharvesting by locals was an added problem.
As we mentioned, there have been discussions for years on how to restore these habitats and the creatures that use them. Active seagrass plantings have more often than not, been unsuccessful. Several estuaries in the state have seen natural restoration occur once the stressors causing problems for the seagrass were lowered. Despite the continued human growth in the Pensacola Bay area, there has been efforts to reduce these stressors as well. Retention ponds, baffle boxes, living shorelines, and more have been used to reduce stormwater issues in the bay. Anecdotal reports through the Florida Sea Grant Eyes on Seagrass project, and others, suggest that seagrasses are improving in some portions of the bay. Many of the Eyes on Seagrass volunteers have reported both an increase in seagrass density, and the increase is such species as Thalassia (turtle grass) and Syringodium (manatee grass) at their monitoring sites.
The Florida Horseshoe Crab Watch Project, a partnership between Florida Sea Grant and the Florida Fish and Wildlife Conservation Commission, has reported the presence of horseshoe crabs in Big Lagoon, Santa Rosa Sound, and some portions of the Pensacola Bay area – though we have not yet identified where they are nesting. The Florida Sea Grant Pensacola Bay Scallop Search has found live scallops in both Big Lagoon and Santa Rosa Sound, logging 133 in 2024. We think sea urchins are still not common in the bay and are considering adding this to our citizen science monitoring program.
One question hanging out there was the salinity of the water – was it high enough to support the restoration of turtle grass and bay scallops. Turtle grass beds are needed for the bay scallop life cycle and both species require a salinity of 20 parts per thousand (ppt) or higher. The Pensacola Bay area has experienced an increase in both rainfall and development in the last decade. The question was – was this increase enough freshwater run-off to lower the salinity to a level that would not support restoration – natural or otherwise? This led to an additional citizen science project where local volunteers would monitor salinity across the bay area to see where the central tendencies were.
Method
Between 2019 and 2025 Florida Sea Grant recruited 22 volunteers to monitor the salinity at 24 locations across the bay area. These volunteers would use a refractometer to measure salinity either at the shore, or at the end of a dock, at their assigned location. One concern with this method was that the volunteers were monitoring at the surface near the shoreline where both turtle grass and scallops do not grow. Increased salinity increases the density of water, and typically the more saline water will be on the bottom. With this we argued that if the mean salinity at the surface near shore was high enough to support these species, the salinity at depth would be as well.
We asked the volunteers to monitor the salinity at their assigned locations once a week until they reached 100 readings – about two years. This would provide information on both salinity over time, and over different seasons. Note: not all volunteers monitored at equal rates during each season.
The data was sent to Florida Sea Grant and stored in a spreadsheet. After 100 readings the mean, median, and mode were determined as well as the standard deviation of the mean. Our hope was that these three values for each site would be close together supporting this as being the central tendency of the salinity at that location. Below we also provide frequency tables for the salinities ranging between 0-10 ppt, 10-20 ppt, 20-30 ppt, 30 ppt and above. We also provide those same frequencies during the different seasons.
22 volunteers were trained to monitor 24 sites across the bay area. For this report we divided these into the following regions:
Lower Perdido Bay – 1 site.
Intracoastal Waterway between Innerarity Point and the Theo Baars Bridge – 5 sites.
Big Lagoon – 5 sites.
Santa Rosa Sound – 4 sites.
Pensacola Bay – 9 sites.
Not all sites were monitored to 100 readings, and those data that did not meet this mark were not used in some of the calculations.
Results
LOWER PERDIDO BAY
| Site | # of readings | Salinity range (ppt) | Mean (standard deviation) | Median | Mode |
| Lower Perdido Bay | 100 | 4 – 26 | 16 ±5 | 15 | 20 |
ICW INNERARITY POINT TO THEO BAARS BRIDGE
| Site | # of readings | Salinity range (ppt) | Mean (standard deviation) | Median | Mode |
| Galvez Landing | 100 | 7 – 31 | 22 ±5 | 22 | 22 |
| Perdido Key State Park | 100 | 9 – 39 | 24 ±6 | 25 | 25 |
| Old River | 36 | ||||
| Kees Bayou | 100 | 5 – 31 | 20 ±6 | 21 | 14 |
| Innerarity Point | 1 |
BIG LAGOON
| Site | # of readings | Salinity range (ppt) | Mean (standard deviation) | Median | Mode |
| Ft. McRee | 4 | ||||
| Big Lagoon State Park Boat Ramp | 1 | ||||
| Big Lagoon | 100 | 19 – 32 | 26 ±3 | 26 | 25 |
| Big Lagoon State Park East Beach | 101 | 0 – 30 | 18 ±8 | 19 | 15 |
| Siguenza Cove | 11 |
SANTA ROSA SOUND
| Site | # of readings | Salinity range (ppt) | Mean (standard deviation) | Median | Mode |
| Big Sabine | 100 | 14 -31 | 23 ±4 | 23 | 26 |
| Little Sabine | 100 | 12 – 30 | 23 ±4 | 23 | 25 |
| Oriole Beach | 100 | 15 – 36 | 26 ±4 | 26 | 30 |
| Shoreline Park | 100 | 10 – 36 | 26 ±5 | 25 | 25 |
PENSACOLA
| Site | # of readings | Salinity range (ppt) | Mean (standard deviation) | Median | Mode |
| Navy Point | 42 | ||||
| Bayou Grande | 29 | ||||
| Bayou Chico | 9 | ||||
| Dickinson Boat Ramp | 12 | ||||
| Hawkshaw Lagoon Memorial Park | 100 | 2 – 30 | 13 ±0.3 | 12 | 10 |
| Hawkshaw Lagoon 9th Ave | 100 | 5 – 30 | 17 ±6 | 15 | 15 |
| Bayou Texar | 100 | 1 – 27 | 14 ±6 | 14 | 15 |
| Bruce Beach | 1 | ||||
| Sanders Beach | 102 | 0 – 34 | 20 ±7 | 20 | 20 |
Frequency Tables for Salinity by Location and Season (only sites 100 readings used)
LOWER PERDIDO BAY
| Salinity range (ppt) | Overall | Winter | Spring | Summer | Fall |
| 0 – 10 | 7 | 2 | 2 | 3 | 0 |
| 10 – 20 | 32 | 9 | 10 | 13 | 0 |
| 20 – 30 | 51 | 22 | 10 | 9 | 10 |
| 30+ | 12 | 5 | 0 | 0 | 7 |
ICW INNERARITY POINT TO THEO BAARS BRIDGE
| Salinity range (ppt) | Overall | Winter | Spring | Summer | Fall |
| 0 – 10 | 6 | 0 | 0 | 6 | 0 |
| 10 – 20 | 77 | 6 | 39 | 16 | 6 |
| 20 – 30 | 193 | 66 | 60 | 28 | 48 |
| 30+ | 22 | 5 | 0 | 9 | 16 |
BIG LAGOON
| Salinity range (ppt) | Overall | Winter | Spring | Summer | Fall |
| 0 – 10 | 14 | 0 | 1 | 13 | 0 |
| 10 – 20 | 46 | 6 | 24 | 13 | 3 |
| 20 – 30 | 126 | 52 | 51 | 8 | 15 |
| 30+ | 22 | 9 | 8 | 0 | 5 |
SANTA ROSA SOUND
| Salinity range (ppt) | Overall | Winter | Spring | Summer | Fall |
| 0 – 10 | 0 | 0 | 0 | 0 | 0 |
| 10 – 20 | 49 | 7 | 9 | 23 | 10 |
| 20 – 30 | 287 | 94 | 93 | 48 | 37 |
| 30+ | 61 | 22 | 4 | 1 | 34 |
PENSACOLA
| Salinity range (ppt) | Overall | Winter | Spring | Summer | Fall |
| 0 – 10 | 52 | 11 | 9 | 17 | 1 |
| 10 – 20 | 200 | 56 | 55 | 39 | 3 |
| 20 – 30 | 126 | 32 | 17 | 21 | 41 |
| 30+ | 16 | 6 | 0 | 0 | 8 |
Discussion
LOWER PERDIDO BAY
For lower Perdido Bay the mean salinity was 16 ±5 and most of the readings were in the 20ppt range.
The mean, median, and mode did not align as much as hoped and was most likely due to heavy rain events.
There was a decrease in salinity during the summer where most of the readings were in the 10ppt range, most likely due to the rainy season. Fall was more saline than other seasons.
We do not know whether turtle grass exists in lower Perdido Bay, and we have not conducted a scallop search there either. But historically we do not believe either existed there.
ICW INNERARITY POINT TO THEO BAARS BRIDGE
From the three sites where 100 readings were obtained the mean salinity runs between 20-24ppt ±5-6. Most readings were in the 20ppt range. Within the ICW itself the median and mode values were very close to the means – suggesting that the salinities are often at 20ppt or higher. Kees Bayou had more variation than the ICW. The mean was 20ppt ±6 but the mode was 14ppt, suggesting a freshwater input source not found in the ICW itself. It is worth noting that during the period of this monitoring we did experience Hurricane Sally and run-off into Kees Bayou could have been significant. As with lower Perdido Bay, the ICW did experience a decrease in salinity during the summer and some of the higher salinities in the fall – most likely for the same reasons. It is known that turtle grass does exist there, but we have not conducted a scallop search there. It is believed that this area could support the restoration of both species.
BIG LAGOON
Only two of the five monitored sites reached the 100 reading mark and were used in the analysis. One of them was along the north shore of Big Lagoon near the Sea Glades community. The mean salinity there was 26ppt ±3 with a median and mode of 26ppt and 25ppt respectively. These data suggest that the central tendency of the salinity in the northern portion of Big Lagoon is high enough to support both turtle grass and bay scallops. It is also known from the Eyes on Seagrass and Scallop Search projects that both species currently exist there.
The monitoring site at Big Lagoon State Park was near East Beach. The mean salinity here was 18ppt ±8. This is lower than the other site not far away and the standard deviation shows more variation in the data here. The range of salinity there was between 0 and 30ppt, which is between freshwater and almost full-strength seawater. These readings suggest there is a significant freshwater discharge source nearby – possibly a runoff issue – that could impede the restoration of both turtle grass and bay scallops. Data from our other two citizen science projects indicate that neither have been found there.
As with the other locations, there is a decrease in salinity during the summer months. There were no records of salinity at 30ppt or higher at either location during the summer and most of the readings were between 0 – 10ppt – suggesting a significant decline in the summer. But, as with the others, the highest salinities were in the fall. Again, Hurricane Sally could have influenced these observations.
SANTA ROSA SOUND
All four sites monitored in Santa Rosa Sound reached the 100 reading mark. The mean salinities here were between 23-26ppt ±4-5. The medians and modes ranged from 23-30ppt. These suggest the salinities within Santa Rosa Sound could support both turtle grass and bay scallops, and our other citizen science projects have confirmed both exist there now. It is worth noting that the salinities were never below 10ppt at any of the sites during the monitoring period. As with the other locations, there was a decline during the summer, with the highest salinity occurring during the fall. Though most of the readings were in the 20ppt range, there were a lot of readings at (or above) 30ppt at this location.
PENSACOLA
Due to the nearby tributaries, which provide freshwater input, we do not think this location supported either turtle grass or bay scallops in the past. However, we felt that some locations needed to be monitored and so included. Of the nine locations monitored, only four reached the 100 reading mark. The mean salinity from those sites ranged between 13-20ppt ±0.3-7. The medians and modes did not vary from the means by much. Most of the data was in the 10ppt range, too low to support either species we were interested in – and, again, this was expected. As with the other locations, there was a decrease in salinity during the summer (though the majority remained in the 10ppt range), and the highest salinity was in the fall. It is worth noting there were salinities at, or above, 30ppt within the bay during this monitoring period. It is also worth noting that seagrass does exist in Pensacola Bay (and neighboring bayous) but the species is widgeon grass (Ruppia) which can tolerate lower salinities. The widgeon grass planted at Project Greenshores is one of the seagrass restoration sites that was successful. In addition to widgeon grass, shoal grass (Halodule) has been found in Bayou Grande. Widgeon grass has also been found in Bayou’s Texar and Chico. There is anecdotal evidence that both widgeon and shoal grass beds expanded near locations where living shorelines were placed.
Conclusion
Based on these findings, we believe that efforts to restore turtle grass and bay scallop could be successful in Big Lagoon, the ICW between Big Lagoon and Perdido Bay, and Santa Rosa Sound. The Eyes on Seagrass and Scallop Search projects will continue.
We would like to acknowledge the following volunteers for their dedication to monitoring for the two-year period asked: THANK YOU!
Ed Bauer Paton Glaze Charles Krupnick Ricky Stackhouse
Jessica Bickell Marty Goodman Holly Langston Marybeth Stager
Gil Bixel Gina Hertz Ann Livingston Denise Tabor
Glenn Conrad Liz Hewson Charlie Lurton John Williams
Mark Cumpston Bob Jackson Julie Orr
Holly Forrester Emogene Johnson Tim Richardson
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