Introduction
Many scientists would agree that one of the countries’ number one water quality issues are excessive nutrients. Excessive nutrients can lead to algal blooms which in turn can reduce dissolved through the process of eutrophication leading to fish kills, or triggering a fish kill from the toxins released by the algae themselves (harmful algal blooms). Most of you have probably heard of the problems they are having with this in central and south Florida, some of which have had a large economic impact on those communities.
Though we have not seen large fish kills in Escambia County since the 1960s and 1970s, smaller ones still occur. Local agencies and non-profits continue to monitor nutrients in local waterways and the University of Florida’s Lakewatch program is one of them.
Method
Florida Sea Grant trains local volunteers to monitor one of six local waterway bodies. Within each waterbody, the volunteer will sample three stations accessed via their personal vessel. Once on station, water clarity is measured using a secchi disk. A 1-liter water sample is pulled to analyze total nitrogen and total phosphorus. And a 1-gallon sample is pulled to be filtered and analyzed for chlorophyll a (a proxy for the concentration of algae in the water). Samples are collected by Florida Sea Grant and sent to the Lakewatch lab in Gainesville FL for analysis. Samples are collected every other month and an annual report is provided in the summer.
Results
The results provided below are the geometric means of all data since monitoring of that waterbody began. The geometric mean is calculated using the product of the values instead of the sum. The nth square root of this product is the value presented.
PENSACOLA BAY
2019 – 2020 – 2 Years
Station 1 – 30.4140°N; -87.1874 W
| Parameter | Range | Geometric Mean | Trend over Time |
| Total Phosphorus (µg/L) | 7 – 16 | 10 | Insufficient data |
| Total Nitrogen (µg/L) | 296 – 300 | 298 | |
| Total Chlorophyll a (µg/L) | 3 – 7 | 4 | |
| Water Clarity (feet) | 6.6 – 8.5 | 7.5 | |
| Salinity (ppt) |
Station 2 – 30.4071°N; -87.1853 W
| Parameter | Range | Geometric Mean | Trend over Time |
| Total Phosphorus (µg/L) | 13 – 17 | 15 | Insufficient data |
| Total Nitrogen (µg/L) | 269 – 280 | 275 | |
| Total Chlorophyll a (µg/L) | 4 – 6 | 5 | |
| Water Clarity (feet) | 7.0 – 7.6 | 7.3 | |
| Salinity (ppt) |
Station 3 – 30.3965°N; -87.1800 W
| Parameter | Range | Geometric Mean | Trend over Time |
| Total Phosphorus (µg/L) | 14 – 15 | 14 | Insufficient data |
| Total Nitrogen (µg/L) | 180 – 310 | 236 | |
| Total Chlorophyll a (µg/L) | 5 -8 | 6 | |
| Water Clarity (feet) | 6.8 – 8.1 | 7.4 | |
| Salinity (ppt) |
Pensacola Bay Summary
Total Phosphorus – Values are about the same at all three stations: 10-15 µg/L. Only two years of data; insufficient to assess trends.
Total Nitrogen – Values are about the same, slightly lower at Station 3 (near middle of bay): 236-298 µg/L.
Total Chlorophyll a – Values are about the same, they increase as you move from the mouth of Bayou Texar to the center of the bay: 4-6 µg/L.
Water Clarity – Values are about the same: 7 feet.
Salinity – insufficient data for this.
BAYOU TEXAR
2007 – 2022 – 16 Years
Station 1 – 30.4520°N; -87.2003 W
| Parameter | Range | Geometric Mean | Trend over Time |
| Total Phosphorus (µg/L) | 13 – 23 | 16 | Decreasing |
| Total Nitrogen (µg/L) | 676 – 1704 | 800 | No change |
| Total Chlorophyll a (µg/L) | 2 – 11 | 6 | No change |
| Water Clarity (feet) | 2.7 – 4.7 | 3.6 | Increasing |
| Salinity (ppt) | 3 – 27 | 8 |
Station 2 – 30.4456°N; -87.1878 W
| Parameter | Range | Geometric Mean | Trend over Time |
| Total Phosphorus (µg/L) | 13 – 25 | 17 | Decreasing |
| Total Nitrogen (µg/L) | 593 – 845 | 670 | No change |
| Total Chlorophyll a (µg/L) | 3 – 13 | 7 | Decreasing |
| Water Clarity (feet) | 2.9 – 4.6 | 3.9 | Increasing |
| Salinity (ppt) | 4 – 15 | 9 |
Station 3 – 30.4344°N; -87.1860 W
| Parameter | Range | Geometric Mean | Trend over Time |
| Total Phosphorus (µg/L) | 12 – 27 | 17 | Decreasing |
| Total Nitrogen (µg/L) | 433 – 778 | 589 | No change |
| Total Chlorophyll a (µg/L) | 3 – 14 | 7 | No change |
| Water Clarity (feet) | 3.0 – 5.0 | 3.9 | Increasing |
| Salinity (ppt) | 5 – 17 | 10 |
Bayou Texar Summary
Total Phosphorus – Values are the same throughout the bayou and have been improving over time: 16-17 µg/L.
Total Nitrogen – Values decrease as you head towards the mouth of Texar and have not changed over time: 600-800 µg/L.
Total Chlorophyll a – Values are the same throughout the bayou and have decreased at Station 2 over time: 6-7 µg/L.
Water Clarity – Increases slightly as you move from the head towards the mouth of the bayou; 4 feet.
Salinity – Geometric means are about the same across the bayou; 8-10 ppt.
BAYOU CHICO
2014 – 2021 – 8 years
Station 1 – 30.4030°N; -87.2638 W
| Parameter | Range | Geometric Mean | Trend over Time |
| Total Phosphorus (µg/L) | 19 – 75 | 29 | No change |
| Total Nitrogen (µg/L) | 396 – 851 | 537 | No change |
| Total Chlorophyll a (µg/L) | 7 – 89 | 15 | No change |
| Water Clarity (feet) | 2.5 – 4.1 | 3.2 | No change |
| Salinity (ppt) | 1 – 13 | 5 |
Station 2 – 30.4050°N; -87.2594 W
| Parameter | Range | Geometric Mean | Trend over Time |
| Total Phosphorus (µg/L) | 15 – 93 | 27 | No change |
| Total Nitrogen (µg/L) | 389 – 990 | 562 | No change |
| Total Chlorophyll a (µg/L) | 7 – 42 | 12 | No change |
| Water Clarity (feet) | 2.8 – 4.4 | 3.4 | No change |
| Salinity (ppt) | 3 – 12 | 7 |
Station 3 – 30.4004°N; -87.2443 W
| Parameter | Range | Geometric Mean | Trend over Time |
| Total Phosphorus (µg/L) | 15-36 | 22 | No change |
| Total Nitrogen (µg/L) | 320-438 | 361 | No Change |
| Total Chlorophyll a (µg/L) | 4-24 | 8 | No Change |
| Water Clarity (feet) | 2.8-5.7 | 4.2 | No Change |
| Salinity (ppt) | 5-12 | 7 |
Bayou Chico Summary
Total Phosphorus – Values decline near the mouth and have not changed over time: 22-29 µg/L.
Total Nitrogen – Values also decline near the mouth and have not changed over time: 360-540 µg/L.
Total Chlorophyll a – Values again decline near the mouth and have not changed over time: 8-15 µg/L.
Water Clarity – Increases near the mouth of the bayou and has not changed over time; 3-4 feet.
Salinity – Values are about the same across the bayou and are below 10 ppt.
BAYOU GRANDE
2012 – 2022 – 9 years
Station 1 – 30.3718°N; -87.3109 W
| Parameter | Range | Geometric Mean | Trend over Time |
| Total Phosphorus (µg/L) | 11 – 26 | 15 | No change |
| Total Nitrogen (µg/L) | 172 – 475 | 301 | No change |
| Total Chlorophyll a (µg/L) | 2 – 7 | 4 | No change |
| Water Clarity (feet) | 2.5 – 7.0 | 4.7 | Increasing |
| Salinity (ppt) | 6 – 22 | 14 |
Station 2 – 30.3721°N; -87.2947 W
| Parameter | Range | Geometric Mean | Trend over Time |
| Total Phosphorus (µg/L) | 11 – 22 | 15 | No change |
| Total Nitrogen (µg/L) | 192 – 405 | 284 | No change |
| Total Chlorophyll a (µg/L) | 2 – 10 | 4 | No change |
| Water Clarity (feet) | 3.0 – 8.5 | 5.8 | No change |
| Salinity (ppt) | 9 – 21 | 16 |
Station 3 – 30.3731°N; -87.2792 W
| Parameter | Range | Geometric Mean | Trend over Time |
| Total Phosphorus (µg/L) | 10-22 | 16 | Decreasing |
| Total Nitrogen (µg/L) | 217-450 | 301 | No change |
| Total Chlorophyll a (µg/L) | 2-13 | 4 | No change |
| Water Clarity (feet) | 3.9-8.5 | 5.7 | Increasing |
| Salinity (ppt) | 13-22 | 17 |
Bayou Grande Summary
Total Phosphorus – Values are about the same across the bayou and have been decreasing near the mouth: 15-16 µg/L.
Total Nitrogen – Values are about the same across the bayou and have not changed over time: 280-300 µg/L.
Total Chlorophyll a – Values are the same and have not changed over time: 4 µg/L.
Water Clarity – Increases slightly as you move from the head to the mouth of the bayou and has been improving over time; 5-6 feet.
Salinity – Increases as you move from the head to the mouth of the bayou; 15-17 ppt.
BIG LAGOON
2020 – 2022 – 3 years
Station 1 – 30.3087°N; -87.3881 W
| Parameter | Range | Geometric Mean | Trend over Time |
| Total Phosphorus (µg/L) | 12 – 14 | 13 | Insufficient data |
| Total Nitrogen (µg/L) | 185 – 277 | 232 | |
| Total Chlorophyll a (µg/L) | 2 – 3 | 2 | |
| Water Clarity (feet) | 8.8 – 12.9 | 10.1 | |
| Salinity (ppt) | 12 – 18 | 15 |
Station 2 – 30.3259°N; -87.3535 W
| Parameter | Range | Geometric Mean | Trend over Time |
| Total Phosphorus (µg/L) | 12 – 15 | 13 | Insufficient data |
| Total Nitrogen (µg/L) | 174 – 253 | 210 | |
| Total Chlorophyll a (µg/L) | 2 – 2 | 2 | |
| Water Clarity (feet) | 8.9 – 12.4 | 10.4 | |
| Salinity (ppt) | 14 – 18 | 16 |
Station 3 – 30.3242°N; -87.3307 W
| Parameter | Range | Geometric Mean | Trend over Time |
| Total Phosphorus (µg/L) | 10 – 14 | 12 | Insufficient data |
| Total Nitrogen (µg/L) | 155 – 284 | 197 | |
| Total Chlorophyll a (µg/L) | 2 – 2 | 2 | |
| Water Clarity (feet) | 9.3 – 12.5 | 10.8 | |
| Salinity (ppt) | 13 – 17 | 14 |
Big Lagoon Summary
Total Phosphorus – Values the same across the Lagoon: 12-13 µg/L. Only three years of data; not enough to assess trends.
Total Nitrogen – Values decrease as you move from the State Park towards Ft. McRee and Pensacola Pass: 200-230 µg/L.
Total Chlorophyll a – Values the same across the Lagoon: 2 µg/L.
Water Clarity – Values about the same across the Lagoon; about 10 feet.
Salinity – Values about the same across the Lagoon; 14-16 ppt.
PERDIDO BAY
2014 – 2022 – 9 years
Station 1 – 30.3239°N; -87.5044 W
| Parameter | Range | Geometric Mean | Trend over Time |
| Total Phosphorus (µg/L) | 11 – 17 | 15 | No change |
| Total Nitrogen (µg/L) | 265 – 390 | 323 | Decreasing |
| Total Chlorophyll a (µg/L) | 3 – 6 | 5 | Decreasing |
| Water Clarity (feet) | 5.3 – 8.2 | 6.7 | Increasing |
| Salinity (ppt) | 10 – 17 | 14 |
Station 2 – 30.3222°N; -87.4575 W
| Parameter | Range | Geometric Mean | Trend over Time |
| Total Phosphorus (µg/L) | 13 – 18 | 15 | No change |
| Total Nitrogen (µg/L) | 265 – 394 | 319 | Decreasing |
| Total Chlorophyll a (µg/L) | 2 – 6 | 4 | No change |
| Water Clarity (feet) | 4.1 – 7.0 | 5.5 | No change |
| Salinity (ppt) | 12 – 17 | 15 |
Station 3 – 30.3456°N; -87.4417 W
| Parameter | Range | Geometric Mean | Trend over Time |
| Total Phosphorus (µg/L) | 13 – 21 | 15 | No change |
| Total Nitrogen (µg/L) | 245 – 394 | 319 | Decreasing |
| Total Chlorophyll a (µg/L) | 3 – 6 | 5 | Decreasing |
| Water Clarity (feet) | 5.1 – 8.9 | 6.1 | Increasing |
| Salinity (ppt) | 11 – 17 | 14 |
Perdido Bay Summary
Total Phosphorus – Values are the same across the lower portion of the bay: 15 µg/L. There has been no change over time.
Total Nitrogen – Values are about the same across the lower bay: 319-323 µg/L. Total nitrogen has been decreasing at all stations over time.
Total Chlorophyll a – Values are about the same across the lower bay: 4-5 µg/L. These have been decreasing over time.
Water Clarity – Clarity is between 6-7 feet across the lower bay and has been increasing over time.
Salinity – Values are about the same across the lower bay: 14-15 ppt.
OVERALL SUMMARY
Total Phosphorus
Most of the bodies of water have values between 10-20 µg/L, 15 µg/L about norm. By Lakewatch definition, these are mesotrophic (middle range). This is not surprising being an estuary and being in the Florida panhandle. The total phosphorus levels are typically lower here. Pensacola Bay is defined as oligotrophic (low range) for phosphorus but has not been monitored for very long. However, Bayou Chico is slightly eutrophic (high range).
Total Nitrogen
Nitrogen is more of a concern in our area and each body of water is a little different.
On the low (ranging between 200-300 µg/L) are Pensacola Bay, Bayou Grande, and Big Lagoon. Each would be defined as oligotrophic for total nitrogen.
Those falling between 300-400 µg/L include Bayou Chico and Lower Perdido Bay. These values are still considered oligotrophic. However, stations 1 and 2 (up within Bayou Chico) range between 400-1000 µg/L which is high range (eutrophic) with a significant decrease in total nitrogen near the mouth of the bayou.
Above 400 µg/L is considered eutrophic (high range). Bayou Texar has geometric means ranging from 600-800 µg/L. Station 1 (near 12th Avenue) has a geometric mean of 800 µg/L over the last 16 years. There is a nitrogen issue in Bayou Texar.
Total Chlorophyll a
Chlorophyll a is a proxy for the concentration of algae within the body of water – “are we heading towards an algal bloom?”. Almost all the waterbodies are below 10 mg/L and most are below 5 mg/L. The one exception is Bayou Chico. Here the range of geometric means is 8-15 µg/L. Eutrophic for this parameter would be geometric means at µg/L or higher. Bayou Chico would be consider eutrophic and Bayou Texar would be borderline.
Water Clarity
There are obvious differences between the more enclosed bayous and the more open Lagoons and Bays. Water clarity within the bayous ranges from 3-6 feet with Bayou Grande being the clearest. The bays and lagoons range from 7-10 feet. Eutrophic (high biological productivity) would have water clarity between 3-8 feet. This is what we see across our system.
Salinity
Estuarine waters are brackish (between 1-30 ppt).
Bodies of water with geometric means between 1-10 ppt include Bayou Texar and Bayou Chico.
Those between 10-20 ppt include Bayou Grande, Big Lagoon, and Lower Perdido Bay.
There has been insufficient data collected at Pensacola Bay to determine a geometric mean.
Though some areas within the lower estuary do have mean salinities at, or above 20 ppt, none of those monitored by Lakewatch do.
Discussion
Four of the six bodies of water being monitored have been so for 8 years or more. For these there have been some interesting trends.
- Though total phosphorus and water clarity are increasing, total nitrogen is the highest of our monitored locations and has not changed in 14 years. More attention needs to be paid to the source of this nitrogen (particularly near Station 1 – 12th Avenue).
- Bayou Chico has higher geometric means in all parameters (less total nitrogen), and lower water clarity, than the other bodies of water. This body of water has received a lot of attention over the last decades. These data suggest that the nutrients are still high and have not changed in the last eight years. Attention to this issue should be considered.
- Bayou Grande has not shown much change over the last nine years but remains the “best of the bayous” in terms of nutrients.
- Lower Perdido Bay has shown improvement in all parameters over the last nine years, and we hope it continues.
The other open bays have not been monitored long enough to determine long term trends, though they show no signs of nutrient issues at this time. Most of waterbodies are at, or below, the threshold of being eutrophic. The one concern is the total nitrogen in Bayou Texar. With the continued work of the city and county, hopefully these trends will continue in the right direction.
WE WOULD LIKE TO THANK OUR LAKEWATCH VOLUNTEERS!
Pensacola Bay Julie Parsons
Bayou Texar Steve Nicosia
Bayou Chico Jerri Johnson
Bayou Grande John Blackwell
Big Lagoon Don Loerch
Perdido Bay Bob Jackson
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