May 19, 2021
Journal Article

Has primary production declined in the Salish Sea?

Abstract

Declining primary productivity has been proposed as an explanation for the declines in coho and Chinook salmon in the Salish Sea over the last thirty years. Marine sediments maintain a continuous record of conditions in the overlying water. We used stables isotopes of organic carbon and nitrogen measured in twenty-one sediment cores to determine the contributions and fluxes of marine-derived and terrigenous organic matter over time. The flux of marine-derived organic matter has remained constant for at least the last 100 years. An apparent increase in the marine flux in recent years is due to remineralization of organic matter in the surface sediments. In contrast, the flux of terrigenous organic matter has increased over the last century in the Strait of Georgia, while in Puget Sound, terrigenous flux peaked in the mid-twentieth century. Total primary productivity has neither increased nor decreased in the Salish Sea over the last 100 years. Consequently, a decline in primary productivity cannot explain the decline in fish populations.

Published: May 19, 2021

Citation

Johannessen S.C., R.W. Macdonald, and J.E. Strivens. 2021. Has primary production declined in the Salish Sea?. Canadian Journal of Fisheries and Aquatic Sciences 78, no. 3:312-321. PNNL-SA-152842. doi:10.1139/cjfas-2020-0115