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Page 7 Attachment B: Supporting Research November 24, 2020 Update 2 — Research Review Phase of IRL Plan Algal blooms are created through the combination of various factors. Algal blooms are typically experienced after a prolonged dry period followed by periods of rain. This rain increases the freshwater flow in the Lagoon, which brings with it nutrients from the land. Blooms typically occur in warmer months as well, so the combination of eutrophic conditions with warm waters is often a driver for these to occur. Unlike other areas within the Lagoon system, Indian River County sits in an area of the Lagoon with more consistent flushing from the inlets, leading to shorter residence times for polluted waters in the system. Lagoon areas to the north have prolonged residence times, which allow polluted waters to sit longer in the system before they are able mix with seawater from an inlet or are able to flush out from new freshwater sources. Areas to the south have shorter water residence times, but are affected by releases from Lake Okeechobee when water levels become too high in the lake. While the County still has its fair share of algal bloom concerns, our geographic location acts as a benefit when dealing with the risk and impacts of algal blooms. Studies conducted by the University of Florida over a ten-year time period show that different sections of the Lagoon are impacted differently by the species of algal blooms produced and the amounts of nutrients received. The County's portion of the Central Lagoon, which ranges from the Sebastian Inlet to the Fort Pierce Inlet, receives consistent freshwater inflow from rivers and canals, with more of an agricultural influence than the northern portions, which includes the Banana River and areas of the main stem of the Lagoon north of the Sebastian Inlet. This study however found that Central Lagoon algal blooms were not tied to periods of high rainfall, but instead, were associated with expanding human development and population growth. In the Central Lagoon, total phosphorus levels were more of a driver of blooms when compared to total nitrogen levels present in the water. However, the opposite was found to be true in the northern portion of the Lagoon. Within the Central Lagoon, strategist species within the phytoplankton community, which are opportunistic species of small size and high growth rates, were found to be favored. Nutrient limitation also plays an important part in the creation and growth of algal blooms. A nutrient is considered limiting when the addition of that nutrient, or combination of nutrients, results in significantly greater growth rates compared to control samples. Studies showed that the presence of surplus bioavailable nutrients at the time of sampling increased growth rates in the control sample when compared to the initial control sample that did not have excess bioavailable nutrients present. Studies of nitrogen to phosphorus ratios conducted within the County show that our portion of the Lagoon is potentially nitrogen limited, which differs from study areas in the northern portion of the Lagoon, which were found to be potentially phosphorus limited. This study also showed that these northern portions are more susceptible to algal blooms forming at faster rates. since excess nutrients do not need to be available in the water over a long period in order for a bloom to occur. These algal blooms also have a tremendous effect on dissolved oxygen concentrations in the Lagoon. During the day, algal species produce oxygen through photosynthesis. At night, dissolved oxygen levels reduce as no sunlight present results in no photosynthesis. As the algae dies off, it drops to the Lagoon floor, decomposes, and consumes oxygen. This die off can occurfrom a combination of high cloud cover resulting in reduced photosynthesis and an increase in biological oxygen demand resulting from 108