Presentation Abstract

A strong decline in phytoplankton productivity has been proposed as a principal cause of the decline in salmon survival in the Strait of Georgia over the last four decades. The best estimate of total annual primary productivity in the Strait in the 1970s was 280 gC m-2 yr-1 (Harrison et al., 1983). We tested whether or not primary productivity had declined since that time by calculating recent productivity from regional nitrogen budgets. We constructed the budgets using measurements (collected 2001-2011) of dissolved and particulate nitrogen and stable isotopes of nitrogen in seawater, river water, sinking particles, bottom sediments, atmospheric deposition, and effluents from pulp mills, aquaculture and municipal wastewater. The budgets indicated a total annual productivity of 280 ± 20 gC m-2 yr-1. The flux of marine-derived organic matter into sediment cores supports this observation. Primary productivity in the Strait of Georgia has neither increased nor decreased since the 1970s.

Session Title

The Salish Sea Marine Survival Project: Juvenile Salmonid Growth and Survival

Keywords

Phytoplankton, Nitrogen budget, Sediment cores, Stable isotopes

Conference Track

SSE11: Species and Food Webs

Conference Name

Salish Sea Ecosystem Conference (Seattle, WA : 2018)

Document Type

Event

SSEC Identifier

SSE11-617

Start Date

5-4-2018 11:15 AM

End Date

5-4-2018 11:30 AM

Type of Presentation

Oral

Contributing Repository

Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.

Geographic Coverage

Salish Sea (B.C. and Wash.)

Rights

This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.

Type

text

Language

English

Format

application/pdf

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Apr 5th, 11:15 AM Apr 5th, 11:30 AM

Has primary productivity declined in the Strait of Georgia since the 1970s?

A strong decline in phytoplankton productivity has been proposed as a principal cause of the decline in salmon survival in the Strait of Georgia over the last four decades. The best estimate of total annual primary productivity in the Strait in the 1970s was 280 gC m-2 yr-1 (Harrison et al., 1983). We tested whether or not primary productivity had declined since that time by calculating recent productivity from regional nitrogen budgets. We constructed the budgets using measurements (collected 2001-2011) of dissolved and particulate nitrogen and stable isotopes of nitrogen in seawater, river water, sinking particles, bottom sediments, atmospheric deposition, and effluents from pulp mills, aquaculture and municipal wastewater. The budgets indicated a total annual productivity of 280 ± 20 gC m-2 yr-1. The flux of marine-derived organic matter into sediment cores supports this observation. Primary productivity in the Strait of Georgia has neither increased nor decreased since the 1970s.