Streaming Media
Presentation Abstract
Local studies across the Salish Sea show variable patterns of kelp change, ranging from total losses to resilient populations as a result of processes that operate on different scales. Here, we present a high-resolution satellite imagery approach to defining changes in kelp extent from 2005 to 2019 for the Gulf Islands and Southern Vancouver Island. We further related these changes to sea surface temperature (SST) from the Landsat thermal sensor and the number of weeks under high SST from lighthouse data. The analysis showed that (i) semi-exposed kelp areas such as Race Rocks, were characterized by strong tidal currents, high salinity (31±1), low SST variability (10oC±1), and low variability of kelp extent (20-35% with relation to the max. kelp area) for all years, including the El Nino years. The exception was 2009 (not an El Nino year), where a larger kelp extent was observed (55%). For this region, SST rarely rose above 12oC, except in strong El Nino when for about four weeks SST was higher than 12oC. (ii) Protected kelp areas such as Mayne Island in the Gulf Islands, were characterized by low tidal currents, lower salinity (26±3), and warmer (18oC±3) waters, and presented high variability (1-35%) of kelp extent. Maximum kelp extent (~30%) was observed in years 2012, 2013, 2017, and 2019, generally characterized by no or weak El Nino influence. These years showed SST around 17oC (±1) and 16 weeks of the spring/summer when the ocean was warmer than 14oC. The lowest kelp areas (~1%) were observed in El Nino years, in which SST in July was 19oC (±1), and temperatures were above 14oC for about 20 weeks. This analysis highlights the complexity of defining kelp resilience in the Salish Sea, and it indicates the potential for defining kelp sentinel regions covering different environmental conditions.
Session Title
Kelp Monitoring - Collaboration & Technology
Conference Track
SSE9: Nearshore
Conference Name
Salish Sea Ecosystem Conference (2022 : Online)
Document Type
Event
SSEC Identifier
SSE-traditionals-197
Start Date
26-4-2022 11:30 AM
End Date
26-4-2022 1:00 PM
Type of Presentation
Oral
Genre/Form
conference proceedings; presentations (communicative events)
Contributing Repository
Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.
Subjects – Topical (LCSH)
Kelps--British Columbia--Gulf Islands; Kelps--British Columbia--Vancouver Island; Remote sensing--British Columbia
Geographic Coverage
Salish Sea (B.C. and Wash.); Gulf Islands (B.C.); Vancouver Island (B.C.)
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.
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
Spatial-temporal changes in kelp extent in the Gulf Islands and Southern Vancouver Island: a remote sensing approach
Local studies across the Salish Sea show variable patterns of kelp change, ranging from total losses to resilient populations as a result of processes that operate on different scales. Here, we present a high-resolution satellite imagery approach to defining changes in kelp extent from 2005 to 2019 for the Gulf Islands and Southern Vancouver Island. We further related these changes to sea surface temperature (SST) from the Landsat thermal sensor and the number of weeks under high SST from lighthouse data. The analysis showed that (i) semi-exposed kelp areas such as Race Rocks, were characterized by strong tidal currents, high salinity (31±1), low SST variability (10oC±1), and low variability of kelp extent (20-35% with relation to the max. kelp area) for all years, including the El Nino years. The exception was 2009 (not an El Nino year), where a larger kelp extent was observed (55%). For this region, SST rarely rose above 12oC, except in strong El Nino when for about four weeks SST was higher than 12oC. (ii) Protected kelp areas such as Mayne Island in the Gulf Islands, were characterized by low tidal currents, lower salinity (26±3), and warmer (18oC±3) waters, and presented high variability (1-35%) of kelp extent. Maximum kelp extent (~30%) was observed in years 2012, 2013, 2017, and 2019, generally characterized by no or weak El Nino influence. These years showed SST around 17oC (±1) and 16 weeks of the spring/summer when the ocean was warmer than 14oC. The lowest kelp areas (~1%) were observed in El Nino years, in which SST in July was 19oC (±1), and temperatures were above 14oC for about 20 weeks. This analysis highlights the complexity of defining kelp resilience in the Salish Sea, and it indicates the potential for defining kelp sentinel regions covering different environmental conditions.
