2023 Salinity Report – 3rd Quarter

We are getting close to the end of the year and here are the salinity numbers for the 3rd Quarter.


For those who have not been following this, we have trained volunteers to record the salinity at the surface near the shoreline around the bay area to determine where the central tendencies for salinity lie.  With the increase in rainfall in the last decade, and an increase in development, there is potentially an increase in stormwater run-off, which could decrease salinities below where some seagrass species, and bay scallop, can tolerate.  Turtle grass (Thalassia) and bay scallops need the salinity central tendencies to be at (or above) 20 parts per thousand (ppt).  We have asked each volunteer to check their site once a week until they have logged 100 readings (about 2 years).


Below are the cumulative data for each site as of the end of the 3rd quarter 2023.


Area Body of Water Number of readings Mean Median Mode
Big Lagoon Big Lagoon

Sea Glades

15 23 23 20
Big Lagoon

State Park

101 18 18 15
Ft. McRee 4 22 22 19
Galvez Landing 100 22 22 22
Kees Bayou 100 20 21 14
Lower Perdido Bay 100 16 15 20
Old River 36 23 23 25
Perdido Key

State Park

71 23 25 15
Siguenza Cove 11 22 21 21
Santa Rosa Sound Big Sabine 85 23 22 26
Little Sabine 100 23 23 25
Oriole Beach 98 26 26 30
Shoreline Park 54 26 25 25
Pensacola Bayou Grande 29 20 21 21
Navy Point SE 41 18 20 20
Navy Point SW 42 17 18 20
Bayou Texar 90 13 13 15
Bayou Chico 7 10 5 5
Bruce Beach 1 18 18
Hawkshaw Memorial 61 13 12 15

9th Ave

36 17 18 15
Sanders Beach 98 19 20 20


For the Big Lagoon area 538 readings have been logged.  Lower Perdido Bay, Kees Bayou, Big Lagoon State Park, and Galvez Landing have all reached their 100-reading mark.  The mean/median/mode for the area is 21/21/19 ppt.

These are borderline for supporting Thalassia and bay scallops.  Most know that this body of water supported both bay scallops and Thalassia historically and based on other surveys we are conducting – they still do.  The bodies of water that caused the central tendencies to be lower are Lower Perdido Bay and Big Lagoon State Park.  Lower Perdido Bay is understandable, this body of water was historically a low salinity system – even supporting some freshwater submerged grasses.  But the lower salinity near the state park is a question we will be looking into.  The park also experienced a health advisory this year, which is not common.


For the Santa Rosa Sound area 337 readings have been logged.  Only Little Sabine has reached the 100-reading mark, but others are close.  The mean/median/mode for the area is 25/24/27 ppt. – more saline than Big Lagoon and certainly high enough to support Thalassia and bay scallops.  We know they historically did, and we also know they still do.


For the Pensacola area 405 readings have been logged.  None of the nine sites have reached the 100-reading mark at this time, though a couple are close.  The mean/median/mode for the area is 16/16/16 ppt.  This is below the 20 ppt threshold to support either Thalassia or bay scallops but we know that these areas did not historically have salinity high enough to support them.  It is worth noting here that there are species of seagrass – Widgeon grass (Ruppia) particularly – that can survive in these lower salinities.  So, people who recreate in these waters should not be surprised to see submerged seagrasses growing there.  Bayou Grande has beds of Shoal grass (Halodule) which do not need it as high as Thalassia but typically live in salinities similar it.  More samples from Bayou Grande are needed but at this time, the central tendency for salinity is near 20 ppt.


We will continue to monitor, and report, these local salinities.


Posted: November 30, 2023

Category: Coasts & Marine, Natural Resources
Tags: Florid Sea Grant, Salinity, Water Quality

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