This memo summarizes findings from the first year (2022–2023) of marine water quality monitoring in Whidbey Basin. These data are being collected to better understand impacts of nutrients, particularly in shallow embayments, and to validate and improve regional models. Generally, the physical and chemical data were similar to limited previous observations. Dissolved oxygen was frequently below the Washington State numeric water quality standard (6 mg/L) but only Penn Cove was occasionally hypoxic (<2 mg/L). In comparing data between Whidbey Basin and Central Basin, phytoplankton growth occurred at different times and to different extents. Further work is needed to understand the role of nutrient inputs on phytoplankton growth dynamics.

Work is ongoing to install autonomous sensors at three locations in Whidbey Basin to collect continuous 15-minute data. Monthly data will be collected at 10 sites via the R/V SoundGuardian in 2024, and a tech memo summarizing the data is expected in fall 2024.