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Date Permissions Signed

8-15-2019

Date of Award

Summer 2019

Document Type

Masters Thesis

Department or Program Affiliation

Huxley College (Environmental Science)

Degree Name

Master of Science (MS)

Department

Environmental Sciences

First Advisor

Love, Brooke

Second Advisor

Yang, Sylvia

Third Advisor

Bingham, Brian L., 1960-

Abstract

Seagrass meadows, common to coastal habitats, have been identified as potential short-term refugia for calcifying organisms from ocean acidification (OA). In nearshore, soft-sediment habitats of the Salish Sea, eelgrass (Zostera marina L.) is the dominant seagrass species, and several studies have found that eelgrass is effective at taking up inorganic carbon and may be carbon-limited, potentially increasing uptake potential in the future. However, irradiance levels vary throughout a day and can therefore influence rates of carbon uptake and release through the relative rates of photosynthesis and respiration. Eelgrass meadows vary in terms of meadow size, shoot density and morphology, and water residence time which could affect rates of carbon uptake of eelgrass meadows and their influence on localized water chemistry. We conducted a series of mesocosm experiments manipulating pCO2, irradiance, and leaf area index (LAI) to assess how these factors interact and contribute to OA variability in the nearshore environment. Our findings demonstrate that increased pCO2 may release the eelgrass from carbon limitation and increase carbon uptake rates. The effect of increased pCO2 on eelgrass carbon uptake was only evident at high irradiance, and high LAI. While greater shoot density increased overall carbon uptake, this effect may diminish as self-shading and/or carbon limitation brought on by photosynthetic carbon uptake emerge at high density. Therefore, eelgrass meadows could potentially measurably drawdown carbon but only when eelgrass with sufficiently high LAI is exposed to saturating irradiance conditions with relatively long water residence times and/or with shallow water depth. We identified rates of carbon uptake and rates of pH increase as a function of LAI. This information will help natural resource managers understand variability of OA due to the photosynthetic activity of eelgrass in meadows throughout the Salish Sea.

Type

Text

Keywords

Leaf Area Index, pCO2, Light

Publisher

Western Washington University

OCLC Number

1112782311

Subject – LCSH

Eelgrass--Pacific Coast (North America); Seagrasses--Pacific Coast (North America); Zostera marina--Pacific Coast (North America); Coastal ecology--Pacific Coast (North America); Carbon--Absorption and adsorption; Ocean acidification

Geographic Coverage

Pacific Coast (North America)

Format

application/pdf

Genre/Form

masters theses

Language

English

Rights

Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author’s written permission.

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