Nightly News | September 29, 2013
>>> in florida , scientists say time is running out for a vital waterway now so polluted that soon the damage could be irreversible. thousands protests along the dying east coast threat. more tonight from nbc's mark potter .
>> reporter: environmental threat that has sign tifts on residents on high alert covers about a third of the florida 's east coast . they're now fouled with pollution and algae. some areas so toxic that they've urged people to stay out of the water.
>> it's not only beyond critical, it's disastrous. it's outrageous.
>> reporter: this is a lady who manages a boast store in florida . she took these pictures by her dock.
>> it burns your eyes and throat. it has a lot of different uncomfortable effects.
>> reporter: it's the indian river la goon system. home to 4300 plants and animal species . for years, the la goon has been filling up with fertilizer and sewage from agry culture and killing wildlife.
>> we're messing with mother nature and we don't want to get to the point of no return.
>> reporter: normally this sand bar is covered along the edges by boats and sunbathers. but now, with all that algae and posted health warnings, most people are staying away. in the south lagoon area, scientists say the natural balance is upset from lake water being released from lake okeechobee . and in there's an unusual high number of manatees and dolphins dying this year. and they're trying to protect them.
>> i'm angry. it needs to be fixed. it's not a -- it's not rocket science . there are solutions. they're all political solutions.
>> reporter: scientists warn efforts must begin soon to save this treasured waterway.