Published: Nov 30, 2011 12:50 PM EST

Red tide is showing up in higher concentrations off the Southwest Florida coast. Scientists with the Sanibel-Captiva Conservation Foundation found high levels of red tide around Sanibel and the causeway area. But, there are very few obvious signs of the microscopic algae so far. It can kill fish, but only a few have washed on shore. Red tide generally isn't dangerous to people, but it can cause breathing problems for some. Nobody knows how long red tide could be a problem, but scientists say time and cooler water temperatures should help clear it up.