The meeting of the fresh water from the Snohomish River and the salt water from Possession Sound creates a unique habitat that is important for many species that make up the biodiversity within this ecosystem. The purpose of this investigation was to observe seasonal variation trends from the pH, chlorophyll, dissolved oxygen (DO) and temperature data at the Deep site in the Possession Sound in Everett, Washington. The study was conducted using a Yellow Springs Instrument 85 and Exo Sonde to collect temperature, dissolved oxygen, pH, and chlorophyll data between 0-3 meters in comparison to 7-10 meters in the the water column. It was hypothesized that during the spring and summer months, there will be a higher chlorophyll concentration due to photosynthesis causing an increase in pH and DO throughout the water column. We also predicted during fall and winter months, there will be a decrease in photosynthesis causing a decrease in chlorophyll, pH, and DO. The hypothesis was not supported. There was an inverse relationship between temperature and dissolved oxygen; as temperature was increasing during the summer months, dissolved oxygen was decreasing. When the temperature was decreasing during the Fall and Winter months, there was a increase in dissolved oxygen.