A red-tide bloom that has already killed a record number of manatees lingers along the Southwest Florida coast, with some patches being found this week along the mainland Monroe County coast.<BR><BR>Marine scientists in the Florida Keys are sampling local waters for signs of the "Karenia brevis" algae, a naturally occurring organism that becomes a red tide when its concentrations soar.</p><p>"Down here right now, there are very minimal traces to no traces" of the Karenia brevis algae, said Cory Walter, project coordinator for Mote Marine Laboratory's Florida Keys Red Tide Monitoring Program. </p><p>"It's more or less a background or minimal level," Walter said. "For this time of year, that's somewhat common."</p><p>The main bloom "has been pretty stationary" off the mainland, she noted. "If a tide does start to slowly move down, it would be this time of year." </p><p>Mote Marine staff and volunteers regularly take water samples near the Keys to check for signs of the harmful algae.</p><p>"The water samples collected by Mote Marine Lab and FWC provide natural-resource managers with important information on the distribution and severity of algal blooms, as well as potential risk to the Keys," said Karrie Carnes, information officer for the Florida Keys National Marine Sanctuary. "Such early detection and monitoring programs are critical, and help the science community better understand the nature and causes of events including harmful algal blooms, red tides and fish kills."</p><p>Red tide at a level that could cause breathing problems for people susceptible to its "respiratory impacts" could be possible from Sarasota County south to Lee County, the National Oceanic and Atmospheric Administration reported Monday.</p><p>"No respiratory impacts are expected elsewhere alongshore southwest Florida, including the Florida Keys, through Thursday," the NOAA report said. </p><p>"Over the last several days, reports of respiratory irritation were received from Charlotte County," it continued. "Reports of dead fish and discolored water were received from Lee County."</p><p>While not a direct threat to the Keys unless it starts moving, the current red tide appears to be the bloom with the most potential to affect the Keys since 2007.</p><p>The bloom so far has been blamed for the deaths of 174 manatees off the state's southwest coast, the largest number of manatee mortalities ever attributed to red tide.</p><p>The current bloom has lasted since September. Florida Fish and Wildlife Conservation Commission biologists have asked the public "to be on the lookout for manatees affected by red tide."</p><p>"Signs that a manatee is affected by red tide include a lack of coordination and stability in the water, muscle twitches or seizures and difficulty lifting its head to breathe," the FWC said.</p><p>Kevin Baxter of the FWC told the Miami Herald that agency scientists believe the manatees are killed by eating sea grass laden with the red-tide algae.</p><p>In 2008, Florida Bay was affected by a long-lasting bloom of blue-green algae. While not toxic itself, the blue-green algae clouded waters, killed sponges and caused some fish kills by sucking oxygen from water.