During the past two summers Pensacola saw extensive rainfall. Residents will often notice the increase in turbid (muddy) water. This is sometimes followed by health advisories and, in extreme cases, fish kills. Residents and visitors alike become concerned about how safe it is to swim and fish in these waters and their use declines. These conditions are triggered by nutrient runoff during these rain events. Fertilizers, yard debris, and animal waste can all contribute to heavy loads of nitrogen, phosphorus, and organic material that support populations of coliform bacteria. The sources of this runoff are numerous – storm drains that reduce flooding on roads and private properties (there are 38 on Bayou Texar alone), cracks in sewer lines, improperly maintained septic tanks, lawn fertilizers, grass clippings and leaves, cleaned fish, and waterfront properties with landscaping that encourages runoff are all problematic. You can read more detail on this topic at this website. Go to the home page, move to MARINE SCIENCE on the left bar, and scroll down to Improving Water Quality; bringing back the bayous.
The turbid water citizens’ first notice after rain is caused either by sediments or tannins. Sediments can come from yard and home projects or other construction projects in the area. Tannins are released from leaf litter when they are in water giving a “tea” color. Neither of these are harmful to humans but can be detrimental for aquatic plants and some marine animals. Excessive amounts of clay can block needed sunlight and are known to actually smother benthic (bottom dwelling) invertebrates, which can indirectly impact us. In addition to the increased turbidity, the salinity of the water decreases which can also cause problems for marine life. People find the “muddy” water unpleasant and generally refrain from swimming or paddling there.
The health advisories issued by the Escambia County Health Department are associated with high levels of fecal coliform bacteria. These bacteria are common in the intestines of warm blooded animals. They in themselves are not pathogenic (disease causing) but are used as an indicator that pathogenic bacteria could be present. The county, state, and federal environmental agencies work together to define at what level these indicator bacteria pose a possible health risk to humans. Both the county and the state monitor bacteria concentrations in our area and post weekly results on their websites. The county website can be found at http://www.escambiahealth.com/eh/programs/beach_sampling.htm .The state website is http://www.dep.state.fl.us/northwest/Ecosys/waterquality/oulook.htm . These agencies monitor fecal coliforms for freshwater systems and Enterococcus bacteria for estuarine and marine ones. A single 100-ml freshwater sample should not contain more than 800 colonies of fecal bacteria and a marine sample should not have more than 104 colonies of Enterococcus. Samples of above this will trigger a re-sample for verification or, if extremely high, an automatic health advisory. Specific locations in the area can be monitored weekly at the two sites mentioned above and we will be posting on this website soon.
Though large fish kills have not occurred in several years (excluding the oil spill) they do happen from time to time. These are triggered by high levels of nutrients in the runoff. Nitrogen and phosphorus can cause a population increase of microscopic plants (phytoplankton) which can reduce water clarity. These phytoplankton consume dissolved oxygen from the water in the evenings. Low levels of oxygen can cause larger forms of marine life to either leave or die. Some of these phytoplankton release toxins, as in red tides, which can be lethal to some species of marine animals.
As mentioned in the article Improving Water Quality on this website there are programs residents can participate in that can help reduce the amount of this runoff. Over the next few weeks we will post articles highlighting one of these programs. If you are interested in learning more about any of them you can contact the UF/IFAS Extension office in Escambia County and we would be glad to answer questions, do a site visit, or do a presentation for a large group.
Next week – Florida Friendly Landscaping