- 19 Aug
Our FWC retired scientist, Walt Jaap, a Snell Isle resident offers the following update on the tremendous water lettuce problem that comes into Coffee Pot Bayou from Crescent Lake...
News from the Bayou
So, what is the floating green stuff in Coffeepot Bayou? Water Lettuce (WL), an invasive plant
Where does it come from? Crescent Lake via a culvert-drain that enters the bayou near 23rd Ave NE.
Why now? It grows like crazy in the summer and is difficult to control.
How is it managed? The Friends of Crescent Lake (FCL) are actively removing the WL by hand during monthly work days (as much as 7 tons on a Saturday). The city installed a floating barrier to minimize WL entering the culvert. The city applied herbicide (an action that was necessary because of the volume of WL at this time). The city has budgeted for a machine to harvest WL (that will not happen in the next few months). The FCL are planting native water plants that over time will displace WL.
What does WL do to the water quality in Coffeepot Bayou? When WL enters the bayou, it is in an unfavorable environment (salt water). It decomposes fairly rapidly. If it is a large floating mat and it sinks to the sea floor there could be an issue with oxygen depletion. We sampled water during a period of heavy WL concentration, we did not find any areas that were deficient in oxygen. In the most recent samples (13 August), water was 47 to 77% saturated with oxygen (31 sample records). This is not to say in an isolated pocket, buried under a mat of WL, there would not be anoxic conditions.
Fortunately the city and FCL have done a reasonable job of limiting WL entry into the bayou in the last few weeks. With all of the rain, it is a challenge and we hope that the measures they have employed will continue to keep WL at bay.