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Page 15 Attachment B: Supporting Research November 24, 2020 Update 2 — Research Review Phase of IRL Plan reduce certain forms of nitrogen to simplerforms —for example, ammonia is converted to nitrite nitrogen which is easily converted to nitrate nitrogen; the nitrogen in nitrate may be further reduced to nitrogen gas. The concentration of reduced forms of nitrogen in the ecosystem may also negatively impact ecosystem health, with excess amounts becoming toxic to certain plant species and leading to shortages of usable nitrogen in the ecosystem. Phosphorus occurs naturally in soils, rocks, and organic matter, and it is a.nutrient required for basic life processes. High concentrations in surface waters may indicate the presence of fertilizer runoff, discharge from wastewater treatment facilities or septic tanks, industrial chemicals, or detergents. Total phosphorus is the sum of inorganic phosphorus (dissolved orthophosphate), dissolved organic phosphorus compounds, and particulate phosphorus. In water quality samples, TP is mostly made up of orthophosphate concentrations. In water, phosphorus can be dissolved or be present as a particulate. It is important to take into account both dissolved and particulate concentrations because both can have an impact on water quality. Particulate phosphorus includes living and dead plankton, precipitates of phosphorus, and phosphorus adsorbed to particulates. Dissolved phosphorus can be organic phosphorus or inorganic phosphorus. Organic phosphorus is generally formed by biological processes and is bound to plant and animal tissues. It can occur from sewage and the breakdown of organic pesticides that contain phosphorus. Organic phosphorus can be soluble, present as loose fragments, or in bodies of aquatic organisms. Most areas of the Lagoon are sensitive to sudden influxes of nutrients and other pollutants because of the location of the inlets. The areas further from inlets depend on wind -driven circulation patterns to circulate water. The areas to the north have much longer residence times compared to areas in the central and southern portions of the Lagoon. According to the IRLNEP Comprehensive Conservation and Management Plan, the residence times in northern areas are in the range of 148 days to 3 days, in the central areas are in the range of 12 days to 1 day, and in the southern areas average about 16 days for water to flow through each specific area. Since the County has an inlet to the north and to the south, our waters are classified more as tidal -driven circulation than wind -driven circulation, and we have much lower residence times because of the location of the inlets. Residence times in Vero are approximately 10 days, and residence times in Sebastian are approximately 5 days. Nutrients in the Lagoon have been increasing from historical values because of increasing population growth and human development. Atmospheric deposition has also contributed to increasing TN concentrations in the Lagoon because of an increase in natural and human -made sources. Human -made sources include the burning of fossil fuels and agricultural activities. Natural sources include lightning (which increases the deposition of nitrogen in rainwater during the summer season), natural burns (such as wildfires), and microbial activities. Atmospheric deposition sources can be local sources, stationary sources, or mobile sources (such as automobiles). Assessing the impacts atmospheric deposition have on nutrient levels in the Lagoon is difficult since the process by which air pollution is transferred to water bodies and the watershed which surround them are not well understood, but Brevard County has estimated that approximately 19% of TN concentrations and 3% of TP concentrations in the Lagoon can be attributed to atmospheric deposition. Seagrasses act as a good indicator species of excess nutrients. However, seagrasses do require certain levels of nitrogen and phosphorus in order to grow and survive, so completely depleting these 116