Introduction
Since I was selected to be the Sea Grant Extension Agent in Escambia County, water quality has been a top priority with both my advisory committee and the public I have had contact with. There are numerous issues impacting the water quality of the Pensacola Bay System and, historically, excessive nutrients have been one of them.
Excessive nutrients can lead to a eutrophication problem. In this case, nutrients enter the local waterways – they enhance plant and phytoplankton growth (particularly in warmer weather) – enhanced phytoplankton growth can decrease water clarity, which can negatively affect submerged seagrasses – some species of phytoplankton release toxic compounds creating what are called harmful algal blooms (HABs) – though enhanced plant growth can produce more oxygen via photosynthesis, plants respirate at night thus decreasing the amount of dissolved oxygen (DO) – this can lead to low enough DO by morning that a fish kill is triggered. Again, this has been an issue in our local waterways in the past, with large fish kills occurring in our bayous.
Such fish kills have not happened in several decades, and HABs are all but non-existent, but monitoring nutrient levels is still a need. Long-term monitoring provides useful information on how the system is working. The two nutrient compounds of interest are total nitrogen and total phosphorus. Trained LAKEWATCH volunteers with Florida Sea Grant / UF IFAS Extension have been monitoring portions of the Pensacola Bay System since 2002. Below is the 2024 report. The data provided is the geometric mean over the course of monitoring, not just this year.
Methods
Trained volunteers use their personal boats to sample three sites within the body of water they are monitoring. Once on site, the boat is anchored, and water clarity is determined using a Secchi disk. Afterwards a 250-ml water sample is collected and iced to be analyzed by the lab. An additional 1-quart sample is collected for filtering back at the dock. Once a site is completed, the volunteer moves to the other two sites to repeat.
Back at dock the 1-quart sample is filtered for phytoplankton and stored in a bottle of desiccant. The 250-ml samples, and the desiccant bottle, are frozen until samples can be sent to the UF IFAS LAKEWATCH lab in Gainesville Florida.
In Gainesville the 250-ml samples are analyzed for total nitrogen and total phosphorus. The filtered sample in desiccant is treated to release the chlorophyll from the phytoplankton and analyzed for total chlorophyll a.
2024 Pensacola Bay Area Updates
BAYOU CHICO
Bayou Chico – Site 1
| Parameter | No. of samples | Minimum annual geometric mean | Maximum annual geometric mean | GRAND GEOMETRIC MEAN | Trend over time |
| Total Phosphorus
(µg/L) |
10 | 12 | 75 | 26 | No trend |
| Total Nitrogen
(µg/L) |
10 | 272 | 851 | 506 | No trend |
| Total Chlorophyll a
(µg/L) |
10 | 6 | 89 | 13 | No trend |
| Secchi
(ft) |
9 | 3 | 4 | 3 | Increasing |
Bayou Chico – Site 2
| Parameter | No. of samples | Minimum annual geometric mean | Maximum annual geometric mean | GRAND GEOMETRIC MEAN | Trend over time |
| Total Phosphorus
(µg/L) |
10 | 15 | 93 | 25 | No trend |
| Total Nitrogen
(µg/L) |
10 | 344 | 990 | 537 | No trend |
| Total Chlorophyll a
(µg/L) |
10 | 7 | 42 | 12 | No trend |
| Secchi
(ft) |
9 | 3 | 5 | 4 | No trend |
Bayou Chico – Site 3
| Parameter | No. of samples | Minimum annual geometric mean | Maximum annual geometric mean | GRAND GEOMETRIC MEAN | Trend over time |
| Total Phosphorus
(µg/L) |
10 | 15 | 36 | 31 | No trend |
| Total Nitrogen
(µg/L) |
10 | 298 | 438 | 358 | No trend |
| Total Chlorophyll a
(µg/L) |
10 | 4 | 24 | 8 | No trend |
| Secchi
(ft) |
9 | 3 | 6 | 4 | No trend |
BAYOU GRANDE
Bayou Grande – Site 1
| Parameter | No. of samples | Minimum annual geometric mean | Maximum annual geometric mean | GRAND GEOMETRIC MEAN | Trend over time |
| Total Phosphorus
(µg/L) |
11 | 11 | 26 | 14 | No trend |
| Total Nitrogen
(µg/L) |
11 | 172 | 475 | 296 | No trend |
| Total Chlorophyll a
(µg/L) |
10 | 1 | 7 | 3 | Decreasing |
| Secchi
(ft) |
10 | 2 | 9 | 5 | Increasing |
Bayou Grande – Site 2
| Parameter | No. of samples | Minimum annual geometric mean | Maximum annual geometric mean | GRAND GEOMETRIC MEAN | Trend over time |
| Total Phosphorus
(µg/L) |
11 | 11 | 22 | 14 | No trend |
| Total Nitrogen
(µg/L) |
11 | 192 | 405 | 276 | No trend |
| Total Chlorophyll a
(µg/L) |
10 | 2 | 10 | 4 | Decreasing |
| Secchi
(ft) |
10 | 3 | 8 | 6 | No trend |
Bayou Grande – Site 3
| Parameter | No. of samples | Minimum annual geometric mean | Maximum annual geometric mean | GRAND GEOMETRIC MEAN | Trend over time |
| Total Phosphorus
(µg/L) |
11 | 12 | 22 | 16 | Decreasing |
| Total Nitrogen
(µg/L) |
11 | 217 | 450 | 296 | No trend |
| Total Chlorophyll a
(µg/L) |
10 | 2 | 13 | 4 | Decreasing |
| Secchi
(ft) |
10 | 4 | 8 | 6 | Increasing |
BAYOU TEXAR
Note: Bayou Texar had two different LAKEWATCH surveys occur. One set, referred to as Bayou Texar South 1 and 2, were monitored between 2000-2002. Bayou Texar sites began monitoring in 2007.
Bayou Texar South – Site 1 (2000-2002)
| Parameter | No. of samples | Minimum annual geometric mean | Maximum annual geometric mean | GRAND GEOMETRIC MEAN | Trend over time |
| Total Phosphorus
(µg/L) |
3 | 16 | 32 | 22 | |
| Total Nitrogen
(µg/L) |
3 | 279 | 547 | 359 | |
| Total Chlorophyll a
(µg/L) |
3 | 3 | 12 | 6 | |
| Secchi
(ft) |
3 | 2 | 4 | 3 |
Bayou Texar South – Site 2 (2000-2002)
| Parameter | No. of samples | Minimum annual geometric mean | Maximum annual geometric mean | GRAND GEOMETRIC MEAN | Trend over time |
| Total Phosphorus
(µg/L) |
3 | 21 | 34 | 25 | |
| Total Nitrogen
(µg/L) |
3 | 369 | 483 | 406 | |
| Total Chlorophyll a
(µg/L) |
3 | 4 | 15 | 9 | |
| Secchi
(ft) |
3 | 1 | 4 | 2 |
Bayou Texar – Site 1 (2007-present)
| Parameter | No. of samples | Minimum annual geometric mean | Maximum annual geometric mean | GRAND GEOMETRIC MEAN | Trend over time |
| Total Phosphorus
(µg/L) |
18 | 13 | 23 | 17 | No trend |
| Total Nitrogen
(µg/L) |
18 | 587 | 1074 | 788 | No trend |
| Total Chlorophyll a
(µg/L) |
18 | 2 | 11 | 6 | No trend |
| Secchi
(ft) |
18 | 3 | 5 | 4 | Increasing |
Bayou Texar – Site 2 (2007-present)
| Parameter | No. of samples | Minimum annual geometric mean | Maximum annual geometric mean | GRAND GEOMETRIC MEAN | Trend over time |
| Total Phosphorus
(µg/L) |
18 | 13 | 25 | 17 | No trend |
| Total Nitrogen
(µg/L) |
18 | 525 | 845 | 660 | No trend |
| Total Chlorophyll a
(µg/L) |
18 | 4 | 13 | 8 | Decreasing |
| Secchi
(ft) |
18 | 3 | 5 | 4 | Increasing |
Bayou Texar – Site 3 (2007-present)
| Parameter | No. of samples | Minimum annual geometric mean | Maximum annual geometric mean | GRAND GEOMETRIC MEAN | Trend over time |
| Total Phosphorus
(µg/L) |
18 | 13 | 27 | 17 | No trend |
| Total Nitrogen
(µg/L) |
18 | 433 | 778 | 579 | No trend |
| Total Chlorophyll a
(µg/L) |
18 | 4 | 14 | 7 | Decreasing |
| Secchi
(ft) |
18 | 3 | 5 | 4 | Increasing |
BIG LAGOON
Note: Big Lagoon is one of the newer bodies of water we monitor.
Big Lagoon – Site 1
| Parameter | No. of samples | Minimum annual geometric mean | Maximum annual geometric mean | GRAND GEOMETRIC MEAN | Trend over time |
| Total Phosphorus
(µg/L) |
4 | 12 | 14 | 13 | Not enough data to determine |
| Total Nitrogen
(µg/L) |
4 | 159 | 277 | 218 | |
| Total Chlorophyll a
(µg/L) |
4 | 2 | 3 | 3 | |
| Secchi
(ft) |
4 | 9 | 11 | 10 |
Big Lagoon – Site 2
| Parameter | No. of samples | Minimum annual geometric mean | Maximum annual geometric mean | GRAND GEOMETRIC MEAN | Trend over time |
| Total Phosphorus
(µg/L) |
4 | 10 | 15 | 12 | Not enough data to determine |
| Total Nitrogen
(µg/L) |
4 | 137 | 253 | 184 | |
| Total Chlorophyll a
(µg/L) |
4 | 1 | 2 | 2 | |
| Secchi
(ft) |
4 | 9 | 12 | 10 |
Big Lagoon – Site 3
| Parameter | No. of samples | Minimum annual geometric mean | Maximum annual geometric mean | GRAND GEOMETRIC MEAN | Trend over time |
| Total Phosphorus
(µg/L) |
4 | 10 | 15 | 12 | Not enough data to determine |
| Total Nitrogen
(µg/L) |
4 | 137 | 253 | 184 | |
| Total Chlorophyll a
(µg/L) |
4 | 1 | 2 | 2 | |
| Secchi
(ft) |
4 | 9 | 12 | 10 |
PENSACOLA BAY
Note: Pensacola Bay is our newest body of water to be monitored.
Pensacola Bay – Site 1
| Parameter | No. of samples | Minimum annual geometric mean | Maximum annual geometric mean | GRAND GEOMETRIC MEAN | Trend over time |
| Total Phosphorus
(µg/L) |
4 | 7 | 16 | 11 | Not enough data to determine |
| Total Nitrogen
(µg/L) |
4 | 151 | 300 | 238 | |
| Total Chlorophyll a
(µg/L) |
4 | 1 | 7 | 3 | |
| Secchi
(ft) |
4 | 7 | 14 | 10 |
Pensacola Bay – Site 2
| Parameter | No. of samples | Minimum annual geometric mean | Maximum annual geometric mean | GRAND GEOMETRIC MEAN | Trend over time |
| Total Phosphorus
(µg/L) |
4 | 9 | 17 | 13 | Not enough data to determine |
| Total Nitrogen
(µg/L) |
4 | 161 | 280 | 237 | |
| Total Chlorophyll a
(µg/L) |
4 | 2 | 6 | 3 | |
| Secchi
(ft) |
4 | 7 | 16 | 10 |
Pensacola Bay – Site 3
| Parameter | No. of samples | Minimum annual geometric mean | Maximum annual geometric mean | GRAND GEOMETRIC MEAN | Trend over time |
| Total Phosphorus
(µg/L) |
4 | 9 | 15 | 13 | Not enough data to determine |
| Total Nitrogen
(µg/L) |
4 | 114 | 310 | 196 | |
| Total Chlorophyll a
(µg/L) |
4 | 2 | 8 | 4 | |
| Secchi
(ft) |
4 | 7 | 17 | 11 |
PERDIDO BAY
Perdido Bay – Site 1
| Parameter | No. of samples | Minimum annual geometric mean | Maximum annual geometric mean | GRAND GEOMETRIC MEAN | Trend over time |
| Total Phosphorus
(µg/L) |
11 | 11 | 17 | 15 | No trend |
| Total Nitrogen
(µg/L) |
11 | 266 | 390 | 318 | Decreasing |
| Total Chlorophyll a
(µg/L) |
11 | 3 | 6 | 5 | Decreasing |
| Secchi
(ft) |
11 | 5 | 8 | 7 | No trend |
Perdido Bay – Site 2
| Parameter | No. of samples | Minimum annual geometric mean | Maximum annual geometric mean | GRAND GEOMETRIC MEAN | Trend over time |
| Total Phosphorus
(µg/L) |
11 | 12 | 18 | 15 | No trend |
| Total Nitrogen
(µg/L) |
11 | 252 | 394 | 311 | Decreasing |
| Total Chlorophyll a
(µg/L) |
11 | 3 | 6 | 5 | No trend |
| Secchi
(ft) |
10 | 4 | 7 | 5 | No trend |
Perdido Bay – Site 3
| Parameter | No. of samples | Minimum annual geometric mean | Maximum annual geometric mean | GRAND GEOMETRIC MEAN | Trend over time |
| Total Phosphorus
(µg/L) |
11 | 13 | 21 | 16 | No trend |
| Total Nitrogen
(µg/L) |
11 | 264 | 394 | 315 | Decreasing |
| Total Chlorophyll a
(µg/L) |
11 | 3 | 6 | 5 | Decreasing |
| Secchi
(ft) |
11 | 5 | 8 | 6 | Increasing |
COMPARING NUTRIENT PARAMETERS
Total Phosphorus (µg/L) Geometric Means
| Body of Water | Site 1 | Site 2 | Site 3 |
| Bayou Chico | 26 | 25 | 31 |
| Bayou Grande | 14 | 14 | 16 |
| Bayou Texar South | 22 | 25 | – |
| Bayou Texar | 17 | 17 | 17 |
| Big Lagoon | 13 | 12 | 12 |
| Pensacola Bay | 11 | 13 | 13 |
| Perdido Bay | 15 | 15 | 16 |
Total Phosphorus Summary
75% of the geometric means were less than 20 µg/L. All of the data from Bayou Chico was above 20 µg/L as were the data collected from Bayou Texar between 2000 and 2002. The total phosphorus has remained stable over the time Lakwatch has been monitoring.
Total Nitrogen (µg/L) Geometric Means
| Body of Water | Site 1 | Site 2 | Site 3 |
| Bayou Chico | 506 | 537 | 358 |
| Bayou Grande | 296 | 276 | 296 |
| Bayou Texar South | 359 | 406 | – |
| Bayou Texar | 788 | 660 | 579 |
| Big Lagoon | 218 | 184 | 184 |
| Pensacola Bay | 238 | 237 | 196 |
| Perdido Bay | 318 | 311 | 315 |
Total Nitrogen Summary
The geometric means for TN were spread over a larger range than TP. To better understand this range and how it is dispersed across the bay system I have divided the results into categories.
LOW (100-300 µg/L) – 45% of the geometric means fell into this category. These include all data from Bayou Grande, Big Lagoon, and Pensacola Bay.
MID (300-500 µg/L) – 30% of the data fell into this category. These include all data from Perdido Bay, Bayou Texar between 2000-2002, and one site in Bayou Chico. NOTE: TN has been declining at all sites in lower Perdido Bay.
HIGH (500 µg/L and above) – 25% of the data fell into this category. Two of the three sites from Bayou Chico and all data from Bayou Texar since 2007 has.
Total Chlorophyll (µg/L) Geometric Means
| Body of Water | Site 1 | Site 2 | Site 3 |
| Bayou Chico | 13 | 12 | 8 |
| Bayou Grande | 3 | 4 | 4 |
| Bayou Texar South | 6 | 9 | – |
| Bayou Texar | 6 | 8 | 7 |
| Big Lagoon | 3 | 2 | 2 |
| Pensacola Bay | 3 | 3 | 4 |
| Perdido Bay | 5 | 5 | 5 |
Total Chlorophyll Summary
90% of all the TC data was below 10 µg/L. The only body of water with geometric means above 10 µg/L was Bayou Chico.
Water Clarity (feet) Geometric Means
| Body of Water | Site 1 | Site 2 | Site 3 |
| Bayou Chico | 3 | 4 | 4 |
| Bayou Grande | 5 | 6 | 6 |
| Bayou Texar South | 3 | 2 | – |
| Bayou Texar | 4 | 4 | 4 |
| Big Lagoon | 10 | 10 | 10 |
| Pensacola Bay | 10 | 10 | 11 |
| Perdido Bay | 7 | 5 | 6 |
Water Clarity Summary
40% of the data has geometric mean for water clarity at, or below, 5 feet. Those include one site in Bayou Grande, and all sites from Bayou Texar and Bayou Chico.
60% of the data had geometric means above 5 feet water clarity. Those include two of the sites in Bayou Grande and all sites in the open bays and Big Lagoon.
DISCUSSION
There are some generalizations we can make from the LAKEWATCH nutrient data collected by our volunteers.
- Bayou Chico and Bayou Texar tend to have higher nutrients, higher chlorophyll a, and lower water clarity than the more open bay sites. The trend has not changed in Bayou Chico over the last decade. Bayou Texar has seen improvement with both chlorophyll a and water clarity.
- Bayou Grande data is lower than the other bayous and more like the open bay data. Bayou Grande has also seen improvements in chlorophyll a and water clarity over the last decade.
- Bayou Chico is elevated in all categories. Total phosphorus, total nitrogen, and total chlorophyll a values are all higher than most of the other water bodies being monitored. Again, these values seem to have remained the same over the past decade.
- Total nitrogen in the upper reaches of Bayou Texar is very high as compared to the other water bodies being monitored. There has been a slight drop since the 2023 report, but the values are still very high.
- The total nitrogen in lower Perdido Bay has been decreasing over the last decade.
- Though the nutrient values, and water clarity data, are good for Big Lagoon and upper Pensacola Bay, few samples have been collected there.
The Florida Department of Environmental has nutrient thresholds defined for the western panhandle of Florida. The last review of these thresholds was in July of 2024. Those thresholds were:
| Body of Water | Total Phosphorus
(µg/L) |
Total Nitrogen
(µg/L) |
Total Chlorophyll a
(µg/L) |
| Big Lagoon | 36 | 610 | 6.4 |
| Lower Perdido Bay | 110 | 780 | 6.9 |
| Upper Pensacola Bay | 84 | 770 | 6.0 |
Understanding that the thresholds for other bodies of water may be different, if we use these values for comparison for all the water bodies we sample, the total nitrogen in upper Bayou Texar and the total chlorophyll a in Bayou Chico are possibly at their thresholds. Nutrient mitigation plans for these two water bodies should be considered. With the large concentration of total nitrogen found at the upper reach of Bayou Texar, Carpenter’s Creek could be a possible source of nutrient pollution.
Overall, besides that mentioned above for Texar and Chico, the nutrient pollution situation is not bad, and is actually improving in some locations.
Acknowledgments
We would like to thank our LAKEWATCH volunteers for their dedication to this project.
Bob Jackson Guy Fisher
Simone Sandifer Steve Nicosia
John Blackwell Julie Parsons
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