2021 Fall Salinity Update

Historically the Pensacola Bay area receives around 60 inches of rainfall each year. This makes us one of the wettest places in the U.S. but in recent years that rainfall amount has increased. Over the last decade the annual average was 71 inches, twice we had more than 90 inches for the year, and we are currently at 88.23 inches for 2021.

Historically most of this rain would fall on the landscape and percolate into the sandy soils recharging the aquifer. Some would runoff as streams and creeks making its way to the estuary. However, over the last fifty years or so we have paved much of the landscape and engineered systems so much of this runoff flows into the estuary. This excess rainfall and runoff could decrease the salinity of the bay system, possibly low enough to impact some biological systems such as seagrass and scallops.

In 2019, Florida Sea Grant began training volunteers to monitor surface waters nearshore to see how the salinity may be changing. Based on information from resource managers, selected seagrasses – turtle grass (Thalassia) and shoal grass (Halodule) – as well as the bay scallop (Argopecten) require salinities at (or above) 20 parts per thousand (ppt).

Trained volunteers monitor selected sites once a week and send numbers to Florida Sea Grant in Escambia County. The MEAN, MEDIAN, and MODE are all calculated using the numbers to determine what the central tendency of these readings are. We are hoping to get 100 readings from each site before volunteers cease. Below are the numbers up through the end of 2021.

2021 Results

Only one site (Lower Perdido Bay) has reached the 100-reading benchmark we are shooting for at this point. Kees Bayou is only a couple of readings short of this mark.

Based on their results, Lower Perdido Bay has salinities too low to support the species mentioned above. However, it is believed that historically Perdido Bay was a more freshwater system and would not have supported these species anyway.

Kees Bayou on the other hand would, and their numbers are at this benchmark. This is encouraging.

Big Sabine is at the 50-reading mark and Little Sabine is almost there. So, both are at the halfway point. These were both locations where the seagrass and scallops mentioned existed. The two species of seagrasses still exist there and there are reports of scallops in some parts of the intracoastal waterway in our area. The salinity readings, at this point, support the growth of these species and this too is encouraging. BUT A REMINDER – THEY ARE ONLY HAVE WAY TO THE 100 READING BENCHMARK.

In addition to these citizen scientists monitoring salinity, we do have volunteers monitoring those seagrasses and search for the bay scallops. We will continue this effort in 2022.

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