Presentation Abstract
Eelgrass (Zostera marina) is a critical nearshore marine habitat for juvenile Pacific salmon (Oncorhynchus spp.) as they depart from their natal streams. Given the poor marine survival of Coho (O. kisutch) and Chinook (O. tshawytscha) salmon juveniles in recent decades, it is hypothesized that deteriorating eelgrass habitats could contribute to their low survival. For three small estuaries in the Southern Gulf Islands of British Columbia, changes in eelgrass area coverage and shape index over the period of 1932-2016 were assessed using historic aerial photographs and Unmanned Aerial Vehicle (UAV) imagery. In addition, changes in eelgrass area and shape index were evaluated in relation to landscape level coastal environmental indicators, namely shoreline activities and alterations and residential housing density. All three eelgrass meadows showed a deteriorating trend in eelgrass condition; on average, eelgrass area coverage decreases by 41% while meadow complexity as indicated by the shape index increases by 76%. Shoreline activities (number of boats, docks, log booms, bulkhead) and residential housing density increase dramatically at all sites over the study period, which are moderately to very strongly correlated to eelgrass area coverage and shape index. Changes in these landscape level indicators over this time period corroborate the observed decline in eelgrass habitat condition as they suggest an overall deterioration of coastal environmental health in the Salish Sea due to increased use of the coastal zone as well as declines in water quality due to urbanization.
Session Title
The Salish Sea Marine Survival Project: Juvenile Salmonid Growth and Survival
Keywords
Aerial photography, Eelgrass, Long-term change
Conference Track
SSE11: Species and Food Webs
Conference Name
Salish Sea Ecosystem Conference (2018 : Seattle, Wash.)
Document Type
Event
SSEC Identifier
SSE11-256
Start Date
5-4-2018 10:30 AM
End Date
5-4-2018 10:45 AM
Type of Presentation
Oral
Genre/Form
presentations (communicative events)
Contributing Repository
Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.
Subjects – Topical (LCSH)
Eelgrass--Monitoring--Salish Sea (B.C. and Wash.); Pacific salmon--Effect of human beings on--Salish Sea (B.C. and Wash.)
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
Included in
Fresh Water Studies Commons, Marine Biology Commons, Natural Resources and Conservation Commons, Terrestrial and Aquatic Ecology Commons
Long-term spatial-temporal eelgrass (Zostera marina) habitat change in the Salish Sea (1932-2016)
Eelgrass (Zostera marina) is a critical nearshore marine habitat for juvenile Pacific salmon (Oncorhynchus spp.) as they depart from their natal streams. Given the poor marine survival of Coho (O. kisutch) and Chinook (O. tshawytscha) salmon juveniles in recent decades, it is hypothesized that deteriorating eelgrass habitats could contribute to their low survival. For three small estuaries in the Southern Gulf Islands of British Columbia, changes in eelgrass area coverage and shape index over the period of 1932-2016 were assessed using historic aerial photographs and Unmanned Aerial Vehicle (UAV) imagery. In addition, changes in eelgrass area and shape index were evaluated in relation to landscape level coastal environmental indicators, namely shoreline activities and alterations and residential housing density. All three eelgrass meadows showed a deteriorating trend in eelgrass condition; on average, eelgrass area coverage decreases by 41% while meadow complexity as indicated by the shape index increases by 76%. Shoreline activities (number of boats, docks, log booms, bulkhead) and residential housing density increase dramatically at all sites over the study period, which are moderately to very strongly correlated to eelgrass area coverage and shape index. Changes in these landscape level indicators over this time period corroborate the observed decline in eelgrass habitat condition as they suggest an overall deterioration of coastal environmental health in the Salish Sea due to increased use of the coastal zone as well as declines in water quality due to urbanization.
