An unexpected snowstorm in early February slowed down Oregonians but not phytoplankton in the water. The Water Quality Researchers of Lake Oswego Corporation found this amazing phenomenon in Oswego Lake on February 11th. The phytoplankton grew exuberantly through ice cracks on the lake, forming long green strips.
Phytoplankton are photosynthesizing organisms, living in freshwater and ocean environments. Phytoplankton are generally considered to be beneficial because they perform an important ecosystem function as primary producers, providing food for zooplankton and fish. It is widely observed that phytoplankton favor eutrophic environments. Eutrophication is generally characterized by high nutrients, mainly nitrogen and phosphorous, and high primary production in freshwater system. However, when phytoplankton form blooms, odor and/or toxin problems reduce the use and/or function of freshwater resources. For instance, the noxious smell of blooms keep people away from swimming, boating and fishing in the water due to its unpleasantness. The oxygen depletion caused by blooms can kill fish and other aquatic organisms and have adverse impact on freshwater ecosystems.
Oswego Lake experienced significant phytoplankton blooms in the early 2000s. With great efforts of monitoring and management, lake water quality has substantially improved. Effective control of blooms has resulted through the use of hypolimntic aeration and aluminum sulfate injection to reduce phosphorous in the water column that favors algal blooms. Graduate students at Portland State University are currently studying these algal blooms and the effects of management actions.