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Indian River Lagoon seagrass losses and ongoing actions to address the issues A healthy Indian River Lagoon contains two primary types of submerged aquatic vegetation— seagrasses and macroalgae. Seagrasses are rooted plants valued for providing habitat for animals, including those supporting commercial and recreational fisheries, trapping sediment that would otherwise reduce water clarity, and absorbing nutrients generated by use of the land. In the lagoon, macroalgae that are unattached—drift algae—also provide habitat and absorb nutrients from the water column. When seagrasses and macroalgae absorb nutrients, they can reduce the occurrence of microalgal blooms that discolor the water and oftentimes "crash"to cause reduced dissolved oxygen levels that result in fish kills. These phytoplankton blooms also block sunlight, which seagrasses and macroalgae need to thrive. In 2011, the Indian River Lagoon experienced extensive, persistent phytoplankton blooms, extending from the southern Mosquito Lagoon to just north of Fort Pierce Inlet. Two blooms can be distinguished based on the dominant species of microalgae, an intense bloom north of Melbourne and a lesser bloom extending south from Melbourne to Vero Beach and Fort Pierce. The scientific community has hypothesized that the more severe, northern bloom was caused by two winters with low water temperatures (2009 and 2010)that led to an apparent collapse of the lagoon's drifting macroalgae, which, in turn, would have decreased uptake of nutrients and possibly released nutrients as the macroalgae decayed. This change in nutrient cycling may have favored the subsequent growth of phytoplankton, in addition, the long-term drought that dominated much of Florida's weather from the 1990s through 2012 promoted hypersaline conditions in northern portions of the system. Along with cold water, high salinities may have increased mortality for small, aquatic animals, including those that feed primarily on phytoplankton. Hypersalinity probably acted as a key determinant of the species of microalgae that dominated the bloom. Thus, these two weather events may have created conditions that promoted the growth of the phytoplankton species responsible for the 2011 "superbloom" in the Banana River and northern Indian River lagoons. A change in the way nutrients were cycled due to a loss of macroalgae also may have played a role in supporting the second, less intense bloom along southern Brevard and Indian River counties.Eight-months later, in the summer of 2012, the area affected by the superbloom was subjected to an unprecedented brown tide that started in the Mosquito Lagoon and spread into the northern Indian River Lagoon. This bloom was dominated by a different species of microalgae that also tolerates high salinities, and it resulted in extremely high levels of chlorophyll o, a measure of microalgal biomass in the water column. Both blooms have receded, and water clarity has improved throughout much of the lagoon. These blooms drastically reduced the amount of light reaching seagrasses for an unusually long time. Consequently,the St. Johns River Water Management District (SJRWMD) recorded a loss of nearly 34,000 acres of seagrasses between 2009 and 2010 in the lagoon north of Fort Pierce. Data from 2011 showed stable or expanding seagrass beds south of Fort Pierce Inlet and in the southern Indian River Lagoon, areas not impacted by the blooms. SJRWMD will be tracking water quality and the health of seagrasses as it has done since the 1980s. SJRWMD continues to partner with the South Florida Water Management District(SFWMD) to map seagrasses from aerial photography every 2-3 years. In 2013, the Florida Department of Environmental Protection(DEP) has agreed to fund this effort. In addition, more than 80 seagrass transects are surveyed twice each year and approximately 12 are surveyed monthly to document the Prepared by the Indian River Lagoon National Estuary Program January 22, 2013 96 -A-g