The quality of water in Tampa Bay declined last year due to algae blooms. A report released by the Tampa Bay Estuary Program shows a decrease in the clarity of the water in multiple areas around Tampa Bay. The 2015 Tampa Bay Water Quality Assessment, which uses data collected from 45 stations across the bay, gauges the progress of water quality in Old Tampa Bay, Hillsborough Bay, Middle Tampa Bay and Lower Tampa Bay.
According to the report, the largest spike in algae, referred to as chlorophyll-a, was in Old Tampa Bay, north of the Gandy Bridge. The levels of chlorophyll-a observed there were well above the annual averages reported back to 1974. Another spike occurred in Middle Tampa Bay, which stretches from the southern end of Tampa to the tip of St. Petersburg. Old Tampa Bay and Middle Tampa Bay account for about 50 percent of the overall water body.
The algae blooms were caused by the heavy rains that fell on the region in July, August and September of last year. In some areas, the rains dumped, more than 20 inches over a two-week period. Except for those three months of heavy rain, all the targeted water clarity levels were met.
The areas where water quality declined and algae blooms spiked were near storm-water and sewage-treatment plants that overflowed during the rains. Treatment plants that were over capacity were forced to release untreated water into the bay. High concentrations of nutrients contained in that discharge resulted in massive algae blooms. According to estuary program officials, it was the first time in three years that water quality goals were missed.
Algae blooms block sunlight from reaching the bottom of the bay and can have a negative effect on seagrass beds. Seagrass beds flourish in less than 6 feet of clear water and are important nurseries and feeding grounds for numerous species native to the area, including shrimp, spotted sea trout, red drum and snook. The seagrass beds are considered one of the key building blocks of a healthy ecosystem.
Last year, the Southwest Florida Water Management District seagrass mapping survey counted 40,295 acres of healthy seagrass. This was the highest amount of seagrass found in the system since 1950. There has been a 47 percent increase in seagrass in the region, or about 3,273 additional acres, since 2012. The next water management district survey of seagrass beds in Tampa Bay is scheduled to be released in the spring of 2017.