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Additional Background for <br /> ASSUMPTIONS FOR ACTION PLAN Agenda Item 14.C.1 <br /> THINGS WE KNOW NOW <br /> ➢ There has been a significant loss of habitat for juvenile fish and other organisms in the <br /> lagoon. <br /> ➢ There are multiple sources of nutrients entering the lagoon including upland runoff <br /> sources (agriculture activities, runoff from cattle, domestic pet waste, residential fertilizer <br /> use, grass clippings, etc) as well as possible sources from old septic tanks leaching into <br /> the water table. <br /> ➢ The Indian River Lagoon is a significant economic driver having a positive $3.7 billion <br /> annual contribution along its 156 mile length. Economically, it's worth fixing. <br /> ➢ Stopping pollution at its source is the most cost effective solution to lagoon pollution <br /> ➢ Restoration activities will range from relatively inexpensive to significantly expensive. It <br /> will require the coordination of local, state and federal agencies to implement solutions. <br /> Most importantly, it will require the support of the general population. A healthy lagoon <br /> benefits the entire community. It will take the entire community to help fix it. <br /> THINGS WE DON'T KNOW NOW <br /> ➢ What really caused the seagrass die-off. There seems to be multiple theories with the <br /> primary ones as follows. <br /> o Hyper saline conditions in the northern portion of the lagoon (north of Melbourne) <br /> either killed off the drift (macro) algae (without drift algae to uptake nutrients <br /> microalgae blooms resulted, thereby killing off sea grasses due to sunlight <br /> blockage), or hyper saline conditions are more favorable to microalgae, allowing <br /> them to bloom and block sunlight to the sea grasses. In addition, some of the <br /> blooms, in particular the brown algae, may be directly toxic. The microalgae <br /> blooms migrated south into Indian River county, killing off sea grasses down to <br /> 17`h St. bridge. (see attachment 1.) <br /> o Excessive nutrient run off into the lagoon triggered microalgae blooms, again <br /> killing off sea grasses by blocking sunlight. <br /> o Excessive hydrogen sulfide released from mosquito control impoundments, <br /> converts to sulfate and deposits into the sediment at levels high enough to be <br /> directly toxic to sea grasses, killing off the grass. With sea grasses gone and <br /> unavailable to uptake nutrients, microalgae blooms result. <br /> N.-A-I <br />