A bloom of the toxic algae known as red tide continued to plague parts of Southwest Florida’s coastline over the past week with fish kills and respiratory irritation. Red tide has persisted since October, when elevated levels of algae reached the coast shortly after Hurricane Ian stirred up the Gulf of Mexico. “By virtue of killing fish, it generates its own nutrient supply,” University of South Florida emeritus oceanography professor Robert Weisberg said in October, when the bloom was just beginning to appear on the radar. “Once it does that, it’s off and running, and it’s very hard to stop i…