We thought we’d step out of the car
for a breath of fresh air and a nice view as we passed by
Clear
Lake on Highway 20 on our way up to the Mendocino National Forest in Northern
California. Little did we know the air
was not so fresh! A putrid mass of dead
rotting algae clogged the entire shoreline.
I unfortunately made the assumption that this must be an invasive
species of algae out of control in the lake, but a little research proved
otherwise.
Over one hundred years ago Clear
Lake was described “…covered with a deep, dense moss, which sometimes rises to
the surface, and often to such an extent in summer as to seriously obstruct the
passage of boats through the water” and “the plants and moss from the bottom
float in great quantities in the water, and it becomes unfit to drink” (Stone 1873). It has been presumed that the “dense moss…
that rises to the surface” is in fact noxious scum forming blue-green algae,
also referred to as cyanobacteria. While
present in the lake for thousands of years, these species of noxious algae have
increased sense the late 1920’s and especially sense the 1940’s, primarily due
to increased erosion and nutrient loading from mining and land-use change
around the lake (Richerson et al. 1994).
These species of algae form “scums”
because they form colonies of individual algae cells and some cells fill with
gas and become buoyant to fix nitrogen from the atmosphere (Mioni et al. 2012). (This is a really cool ecological trick
utilizing bacteria, do web search on “nitrogen fixing bacteria” for more
info). Anyway, because these algal scums
are gross they bother the residence of the lake and reduce tourism at a cost of
millions of dollars a year (Richerson et al. 1994). For more
information a report was released earlier this year investigating cyanobacteria
blooms in Clear Lake and the Sacramento-San Joaquin River (Mioni et al. 2012). This whole exercise has really highlighted
for me the danger in making assumptions with little data and how “naturally
occurring” components of an ecosystem can become disruptive through the unconscious
consequences of modern development.
References
Mioni,
Cecile, Raphail Kudela, Dolores Baxa, and Meghan Sullivan. 2012. Harmful
Cyanobacteria Blooms and Their Toxins in Clear Lake and the Sacramento-San
Joaquin Delta ( California ).
Richerson, Peter J, Thomas H
Suchanek, Stephen J. Why, and Thomas Smythe. 1994. THE CAUSES AND CONTROL OF.
http://www.des.ucdavis.edu/faculty/Richerson/CleanLakesReport1994.pdf.
Stone, Livingston. 1873. XX.
-Report of Operations in California in 1873. http://www.co.lake.ca.us/Assets/WaterResources/Algae/Livingston+Stone.pdf.