We completed a two-year study (2018-2019) to investigate the sources and pathways of nutrients, specifically phosphorus, that can fuel algae blooms in Hicklin Lake. In this study, we assessed water quality conditions in Hicklin Lake and calculated relative loads of nutrients and metals from within the watershed, including Mallard Lake. The purpose of the Hicklin Lake Water Quality Management Assessment is to assist in determining where to focus management efforts to reduce nutrients’ influence on the lake. Highlights from the study include:
• Hicklin and Mallard Lake strongly stratify in the summer. Under anoxic conditions, the lake sediments release phosphorus and ammonium nitrogen. During lake-mixing events the phosphorus and ammonium nitrogen becomes available to algae, causing blooms that may be toxic.
• Nutrient and metal concentrations in the inlets to Hicklin and Mallard Lake were similar across all sites for each parameter.
We also identified potential strategies aimed to manage algae blooms in Hicklin Lake. These strategies focus on reducing both watershed and internal loads of phosphorus to Hicklin Lake since phosphorus is the primary driver of toxic algae blooms in Puget Lowland lakes.
Potential management strategies include:
• Algicides or chemical and physical inhibition
• Source control, including identification and removal of illicit sewage connections and other illicit discharges, pet waste management, and erosion control
• Stormwater and surface runoff treatment including detention facilities, rain gardens, and regional treatment facilities
• Dredging
• Dilution
• Applying a phosphorus-binding chemical to the lake