The Influence of Riverine Inputs and Nutrients on Plankton Abundance and Composition in the Pacific Northwest: The Importance of Silicate as a Limiting Nutrient

Abstract

Silicate levels are important for many types of plankton; Diatoms, radiolarians, and silicoflagellates use the silicate to create shells and are the only species which fix silica. Silicate availability in the San Juan Channel has been changing from 2005 to 2022. Silica levels are heavily influenced by the Fraser River output. Silicate and phosphate have been decreasing. Nitrate has been increasing. Silicate: Nitrogen ratio has been decreasing but has not dropped below the 1:1 threshold to become silicate limited. Silicate levels are stable and a change in the plankton community is not expected due to the decrease in silicate.