What’s that in the lake and where did it come from?

MANDEVILLE, LA (WGNO) -- Causeway commuters, perhaps you've noticed some large, green patches floating on the lake as you drive near the Mandeville end of the bridge.

Over the years, we've seen multiple algae blooms caused by the warm lake water.  Sometimes, the blooms pose health risks.  But according to the Lake Pontchartrain Basin Foundation, what you're seeing this go 'round on the lake is not algae.

Instead, the large mats of green could be any number of plants that are generally called duckweed.  They float on the water and can cause problems in areas of waters with borders like canals or marinas.

According to the foundation, the recent rains that caused so much flooding in the state also sent water surging out of the Tchefuncte River and into the lake.  The plants went along for the ride.

The Lake Pontchartrain Basin Foundation says the plants are covering only a small portion of the lake's surface which spans over 600 square miles.  Also, the plants in this case do not fare as well in salt or even moderately brackish water.

Bottom line, the plants aren't expected to make it very long in the lake, especially as cooler temperatures arrive this fall.  Also, there's no concern at this point that the plants pose any sort of risk to the oxygen level in the water that fish and aquatic plant life need to survive.