How are the Nutrients in Our Bay?
It is not a question you hear every day – but you DO hear “is it safe to swim in the water?” “are there any fish kills?” and other questions that are directly, or indirectly, connected the amount of nutrients in our waterways.
Almost everyone has heard about the numerous harmful algal blooms (HABs) and red tides occurring around the Lake Okeechobee area of the state. Fish kills, green water, bad smells, dead marine mammals and turtles, the list goes. All of this has hurt property values and the tourism economy of that part of the state. We have heard of it, but we may not know that one (and some say the primary) cause is excessive nutrients in the waters.
Nutrients are just that, fertilizers to encourage growth and health in plants – animals need nutrients as well. However, too many nutrients can create large algal blooms that can (1) decrease water clarity killing needed submerged plants, (2) deplete the system of much needed dissolved oxygen, (3) some algae can release toxins – HABs. All are problematic.
Where do these excessive nutrients come from?
Lawn fertilizers, pet waste, grass clippings, discarded cleaned fish, ag fertilizers, livestock waste, septic tanks, sewage overflows, it goes on. These nutrient laden waste washes into stormwater systems and eventually make their way to the rivers, bays, and Gulf. When they arrive, they begin to do their thing and problems can follow. Sometimes serious problems.
So, what is the nutrient situation in the Pensacola Bay area?
Well, we certainly have rivers flowing in from the forestry and farmlands. We certainly have a residential and commercial development in the northern parts of the county where excessive soils and fertilizers from lawns can reach our waterways. The lower end of the county is highly developed with numerous sources of nutrients in septics, sewers, lawns, golf courses, and on. We have what it takes to kick off a problem in our bay – but do we have a problem?
One monitoring effort comes from the UF IFAS extension program called LAKEWATCH. Lakewatch is a citizen science program where volunteers with boats are trained on how to sample for nutrient testing. They collect samples for total nitrogen and phosphorous, chlorophyll, water clarity, and salinity. These samples are analyzed in the Lakewatch lab on campus at the University of Florida and an annual report comes out each August. We currently have six eager volunteers who sample one of six water bodies every other month. Some water bodies have been monitored for over 10 years, others are JUST starting, either way – we are learning about our system and what citizens may need to do to reduce the change of a problem.
What do the numbers say?
Here are the data from August 2019 report.
|Body of Water||Year monitoring began||Total Phosphorus (µg/L)||Total Nitrogen (µg/L)||Total Chlorophyll (µg/L)||Water clarity (ft.)||Salinity (‰)|
|Pensacola Bay||2019||ND||ND||ND||ND||Just started|
|Lower Perdido Bay||2014||15-16||350-360||5-6||5.3-6.1||13-14|
So, what does this tell us?
1) We are above state average with total nitrogen, and Bayou Texar is almost twice as high as the other bodies of water.
2) We are above average with total chlorophyll. This is a metric that gives you some idea how much algae are growing in the water. We have more than most bodies of water Lakewatch is monitoring.
3) Bayou Chico is above the state average for total phosphorus.
4) These bodies of water currently being monitored have low salinity.
As mentioned, high nitrogen can lead to high algal blooms and fish kills. Though we have high nitrogen in the water, we are not seeing the fish kills we saw in the 70s. This is good, but the high nitrogen levels can be concerning. There was a large fish kill in Bayou Chico in 2019. It was during the heat of the summer and extremely warm waters can lower dissolved oxygen enough to kill fish. Still, the levels are high, and residents should consider changing some practices to try and reduce this.
The higher than average chlorophyll numbers also suggest a lot of algae in the water. Again, fish kills are not what they were but reduction of nitrogen in the water is still something we should strive for.
How do we do this?
Several things can help
1) Try to keep sediments from reaching storm drain pipes. Sediment can carry sources of nitrogen that can spike total nitrogen readings.
2) Plant a lawn/garden that does not require fertilizers. If you must fertilize, have your soil tested at the county extension office so that you know how much you need. Excessive nitrogen will not be taken up by the plants and will eventually end up in our waterways.
3) Clean up after your pets.
4) Bag grass clippings and other yard waste in the new large paper bags. These can be mulched at the landfill.
5) If you are on septic, consider connecting to sewer. If this is not an option have your septic pumped out at least every five years. Also, watch what you flush. Food can release nitrogen as easily as human waste can.
6) If you are on sewer, watch what you flush. In addition to food (run down the disposal) releasing nitrogen, many flushable products are flushable – but they are not degradable and can clog the sewer lines causing sanitary sewage overflows. Many do not know, but milk can do the same. Do not pour milk down the drain, rather pour it on your garden.
If the entire community could a few of these suggestions, we could see our nitrogen numbers decline and avoid a chance of having large problem they you see in south Florida.