Nutrient Pollution in Pensacola Bay; the 2019 LAKEWATCH Report for Escambia County Waters

Water quality is something that concerns many in our community.  Older folks will remember the days of large fish kills in our bayous, reports of PCB in sediments and some species of fish tissue, and more recently health advisories.  Area waters have suffered from several stressors over the years, and things have improved quite a bit – but there is still more to do.

 

One of the more famous issues we have had to deal with are the large fish kills of the 1970s.  Thousands, sometimes hundreds of thousands, of dead fish were found in the early morning hours covering the surface of our local bayous.  There are several stressors that can cause a large fish kill, some of them natural, but the primary one is excessive nutrients triggering low dissolved oxygen in the water.

 

As the term implies, nutrients are important for organism growth.  Excessive amounts can cause excessive growth – algal blooms.  These algal blooms reduce water clarity, stressing benthic seagrass communities, and reduce the amount of dissolved oxygen for aquatic life.  When the algal bloom dies, the increased decomposition by bacteria draws the dissolved oxygen levels even lower and fish kills occur.  This process is known as eutrophication and is what is currently occurring in the Lake Okeechobee / Indian River area of our state.

 

Nutrients can come from a variety of sources.  Natural run-off from land would include leaf litter, and other organics, that are decomposed by bacteria and release nutrients (nitrogen and phosphorus) into the system to be absorbed by the plants.  But in the past decades human development has increased the amount of leaf litter with raked debris on the streets, fish cleaning stations, animal and human waste discharged into waterways, and commercial fertilizers we put on our lawns.  In addition to increasing nutrients in the run-off, we have removed the plant communities along the shoreline that could buffer the amount reaching the water, making the situation even worse.

 

One response to this situation is to monitor local waters for nutrients, and the concentration of phytoplankton (microscopic algae/plants).  The University of Florida County Extension conducts the LAKEWATCH program.  In this program, volunteers are trained on how to sample, and preserve, water samples to be analyzed by technicians at the LAKEWATCH lab in Gainesville.  Though the program was originally developed to monitor Florida lakes, it now includes some coastal estuaries.

 

In Escambia County we have four such volunteers who monitor Bayou’s Chico, Texar, and Grande, as well as lower Perdido Bay.  Each volunteer uses their boats to monitor three stations within their body of water.  They are monitoring for total nitrogen, total phosphorus, chlorophyll a (a proxy for algal bloom), and water clarity.  UF IFAS LAKEWATCH also measures salinity of these samples.  Below is the 2019 update report for each body of water.

 

Bayou Texar

We have 12 years of data from 2007 to the present.  The three sample stations are at

1)      Near the 12th Avenue Bridge

2)      Off of Hyde Park Road

3)      Off of Bayview Park

The phosphorus concentrations are like the other bodies of water, albeit Chico is higher.

Texar has the highest nitrogen concentrations of the four water bodies, with the highest near the 12th Avenue Bridge.

The chlorophyll concentrations (measure of phytoplankton growth) are slightly elevated from Grande and lower Perdido, but MUCH lower than Chico.

Water clarity is around 4 feet and improves as you move from the 12th Avenue Bridge towards the bay.

Mean salinities run between 8 and 10 parts per thousand.

All metrics indicate that Bayou Texar is eutrophic (high nutrients), but you would expect an estuary to be at this level.

 

Phosphorus Nitrogen Chlorophyll
Site Max Min Mean Max Min Mean Max Min Mean
1 23 13 17 1074 676 803 8 3 6
2 25 13 18 845 593 675 13 4 8
3 27 14 18 778 433 595 14 5 8

 

 

Bayou Chico

We have 5 years of data from 2014 to the present.  The three sample stations are

1)      Lower Jones Creek

2)      Off the Pensacola Shipyard

3)      Near the Bayou Chico Bridge

The phosphorus concentrations are higher in Chico than the other bodies of water.  They are higher in the upper portions of the bayou.

The nitrogen levels are not as high as they are in Texar but higher than the other two bodies of water.

The chlorophyll concentrations are MUCH higher in Jones Creek than any other station sampled and decrease as you move towards the bay – but all stations are much higher than other bodies of water.

Water clarity is between 3 and 4 feet and improves as you move from Jones Creek towards the bay.

Mean salinities run between 7 and 8 parts per thousand.

All metrics indicate that that stations 1 and 2 are hypereutrophic (excessively high nutrients) and reason for concern.  There have been no reports of large-scale fish kills within the bayou in recent years but identifying the sources of these nutrients should be determined and reduced.

 

Phosphorus Nitrogen Chlorophyll
Site Max Min Mean Max Min Mean Max Min Mean
1 75 19 31 851 396 514 132 10 31
2 93 15 30 990 389 601 64 8 18
3 36 15 23 430 320 357 24 6 11

 

Bayou Grande

We have 6 years of data from 2012 to present.  The three sample stations are

1)      Off Mac’s Marina

2)      Off Navy Point

3)      Near the mouth of Bayou Grande

The phosphorus concentrations are about the same as the other bodies of water, albeit Chico is higher.

The nitrogen concentrations are about the same as lower Perdido, and lower than the other two bayous.

The chlorophyll concentrations are also about the same, albeit Chico is higher.

Water clarity is clearer than the other two bayous between 4 and 5 feet and improves as you move towards the bay.

Mean salinities are higher in Grande running between 17 and 18 parts per thousand.

All metrics indicate that Bayou Grande is also eutrophic, but again – we expect this in an estuary.

 

Phosphorus Nitrogen Chlorophyll
Site Max Min Mean Max Min Mean Max Min Mean
1 26 12 16 475 271 349 7 3 5
2 22 12 16 405 255 321 10 3 5
3 22 15 19 450 276 340 13 3 6

 

Lower Perdido Bay

We have 5 years of data from 2014 to present.  The three sample stations are

1)      Off Innerarity Point

2)      Off the mouth of Bayou Garcon

3)      Off the mouth of Tarkiln Bayou

The phosphorus concentrations are about the same as the other bodies of water, albeit Chico is higher.

The nitrogen concentrations are about the same as Grande, and lower than Texar and Chico.

The chlorophyll concentrations are about the same as Grande, and lower than Texar and Chico.

Water clarity here is clearer than the other bodies of water between 5 and 6 feet.

Mean salinities run between 13 and 14 parts per thousand.  Less saline than Bayou Grande.

All metrics indicate that the lower Perdido Bay is eutrophic, but again – this is expected for an estuary.

 

Phosphorus Nitrogen Chlorophyll
Site Max Min Mean Max Min Mean Max Min Mean
1 19 13 16 390 342 358 6 5 5
2 18 13 15 394 326 356 6 4 5
3 21 13 16 394 334 362 7 5 6

 

Summary

As far as nutrient pollution is concerned, Bayou Grande and lower Perdido are in much better shape than Bayou’s Texar and Chico.  Bayou Chico has higher concentrations of nutrients than the others and have the only two stations that are considered hypereutrophic (lower Jones Creek and off the Pensacola Shipyard).  Despite these high nutrient and chlorophyll concentrations in Chico, no large-scale fish kills have occurred.  It is recommended that the source of these nutrients be identified and managed, and that dissolved oxygen concentrations be monitored near the bottom at these stations.  Currently, UF IFAS LAKEWATCH does not have funding to monitor dissolved oxygen, so another agency (or source of money for these volunteers) is needed.

 

Contact the Florida Sea Grant Agent, or the Coastal Sustainability Agent, at the Escambia County Extension Office for suggested management practices homeowners and businesses within the Bayou Chico watershed can adopt to help improve the nutrient situation here.

 

We have been given the go ahead to train volunteers to monitor Big Lagoon, Pensacola Bay, and Escambia Bay.  Volunteers will need a boat and will sample every other month over the course of the year.  If you are interested, contact Escambia County Sea Grant Rick O’Connor at (850) 475-5230 ext 111, or roc1@ufl.edu.