During the final days of the past month, a whale shark, the world’s largest shark, washed up on the Florida coast in the precise location of Sanibel Island. The cause of death is suspected to be red tide.
Red tide is a harmful algal bloom that often kills thousands of fish with its blooms. It consists of the organism Karenia Brevis, a toxic organism.
Like most algal blooms, phosphorus (found in both fertilizers and animal manure), can fuel red tide. Fertilizer and animal agricultural runoff, as a result, can support the growth of harmful algal blooms such as red tide.
Sources: https://www.washingtonpost.com/news/speaking-of-science/wp/2018/08/03/a-red-tide-ravaging-florida-may-have-killed-a-whale-shark-for-the-first-known-time/?utm_term=.00bfcecfd495
Turning The Tide 