Success and succession in species and ecosystem recoveries: kelp forest community dynamics following decades of sea otter re-establishment
Presentation Abstract
The recovery of predators has the potential to restore ecosystems and fundamentally alter the services they provide. One of the most iconic examples of this potential comes from keystone predation by sea otters in nearshore habitats of the Northeast Pacific. On the outer coast of Washington state, USA, a population of sea otters re-introduced in 1969-1970 exhibited a more than 10-fold increase during the 1980s and 1990s. This population increase led to a pronounced decline in sea otter prey, particularly kelp-grazing sea urchins. Here we show that the reduction in invertebrate prey coincided with an expansion of kelp beds coastwide until the turn of the century. However, while sea otter and kelp population growth rates were positively correlated prior to 2000, this association diminished substantially in the last 15+ years. A recent 2015 survey of benthic invertebrates shows that sea otter prey have continued to decline as the sea otter population has continued to expand, but kelp abundance is not closely related to these trends. However, variability in kelp abundance has declined in the most recent 15 years of the time series. Altogether these results suggest that initial nearshore community responses to sea otter population expansion follow predictably from trophic cascade theory, but now other factors may be as or more important in influencing community dynamics. Thus, the role of sea otter predation may be context-dependent with shifting environmental conditions strongly affecting their utility in ecosystem restoration.
Session Title
Kelp Distribution and Recovery Strategies in the Salish Sea: Part I
Conference Track
SSE1: Habitat Restoration and Protection
Conference Name
Salish Sea Ecosystem Conference (2018 : Seattle, Wash.)
Document Type
Event
SSEC Identifier
SSE1-641
Start Date
6-4-2018 8:45 AM
End Date
6-4-2018 9:00 AM
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)
Sea otter--Populations--Salish Sea (B.C. and Wash.); Sea otter--Effect of predation on--Salish Sea (B.C. and Wash.); Sea urchins--Predators of--Ecology--Salish Sea (B.C. and Wash.); Kelp bed ecology--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
Success and succession in species and ecosystem recoveries: kelp forest community dynamics following decades of sea otter re-establishment
The recovery of predators has the potential to restore ecosystems and fundamentally alter the services they provide. One of the most iconic examples of this potential comes from keystone predation by sea otters in nearshore habitats of the Northeast Pacific. On the outer coast of Washington state, USA, a population of sea otters re-introduced in 1969-1970 exhibited a more than 10-fold increase during the 1980s and 1990s. This population increase led to a pronounced decline in sea otter prey, particularly kelp-grazing sea urchins. Here we show that the reduction in invertebrate prey coincided with an expansion of kelp beds coastwide until the turn of the century. However, while sea otter and kelp population growth rates were positively correlated prior to 2000, this association diminished substantially in the last 15+ years. A recent 2015 survey of benthic invertebrates shows that sea otter prey have continued to decline as the sea otter population has continued to expand, but kelp abundance is not closely related to these trends. However, variability in kelp abundance has declined in the most recent 15 years of the time series. Altogether these results suggest that initial nearshore community responses to sea otter population expansion follow predictably from trophic cascade theory, but now other factors may be as or more important in influencing community dynamics. Thus, the role of sea otter predation may be context-dependent with shifting environmental conditions strongly affecting their utility in ecosystem restoration.
