Presentation Abstract

King County built a new marine outfall in 2008 that discharges treated wastewater effluent to the Puget Sound Central Basin about 1.6 kilometers offshore at a depth of 183 meters (m). The outfall consists of two 1.6 m diameter HDPE pipes weighted with concrete anchors. To assess the artificial reef effect of the exposed pipes and its use as habitat by marine organisms, underwater video has been collected annually since 2009 at the shallower depths (to -91 m MLLW). Initial video showed rapid colonization by barnacles and other invertebrates. Several rockfish species have routinely been seen on the pipes, particularly at the -24 to -37 m MLLW depth range. Most of the typically solitary rockfish species appear to be subadults that are schooling together, suggesting the pipes might serve as transitional habitat. In 2014, WDFW observed a bocaccio rockfish near the pipes, the first confirmed Central Basin sighting in at least 12 years at that time. During the same survey, over 50 canary rockfish were also seen and canaries were also seen in 2017. To assess biological colonization of the pipes, ten pieces of pipe-material were deployed in 2012 at four depths near the pipe: 30, 91, and 183 m, with a 183 m reference site. Three replicates of these “settlement plates” will be collected at each site after 2, 5, and 10 years. The percent cover of non-motile organisms and counts of motile species will be assessed from photographs taken of each plate and species identified to the lowest practical taxonomic unit. The first sets of plates were retrieved in September of 2014, the second set in October 2017. The pipes provide complex, hard substrate in an area otherwise devoid of rock and cobble and observations from the underwater video and findings from the settlement plates will be presented.

Session Title

Recovery and Monitoring for ESA-listed Rockfish and Habitats in the Salish Sea

Keywords

Marine outfall, Rockfish, Biota, Habitat

Conference Track

SSE11: Species and Food Webs

Conference Name

Salish Sea Ecosystem Conference (Seattle, WA : 2018)

Document Type

Event

SSEC Identifier

SSE11-273

Start Date

4-4-2018 4:30 PM

End Date

4-4-2018 4:45 PM

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 4th, 4:30 PM Apr 4th, 4:45 PM

If you build it, they will come: marine habitat provided by a wastewater outfall

King County built a new marine outfall in 2008 that discharges treated wastewater effluent to the Puget Sound Central Basin about 1.6 kilometers offshore at a depth of 183 meters (m). The outfall consists of two 1.6 m diameter HDPE pipes weighted with concrete anchors. To assess the artificial reef effect of the exposed pipes and its use as habitat by marine organisms, underwater video has been collected annually since 2009 at the shallower depths (to -91 m MLLW). Initial video showed rapid colonization by barnacles and other invertebrates. Several rockfish species have routinely been seen on the pipes, particularly at the -24 to -37 m MLLW depth range. Most of the typically solitary rockfish species appear to be subadults that are schooling together, suggesting the pipes might serve as transitional habitat. In 2014, WDFW observed a bocaccio rockfish near the pipes, the first confirmed Central Basin sighting in at least 12 years at that time. During the same survey, over 50 canary rockfish were also seen and canaries were also seen in 2017. To assess biological colonization of the pipes, ten pieces of pipe-material were deployed in 2012 at four depths near the pipe: 30, 91, and 183 m, with a 183 m reference site. Three replicates of these “settlement plates” will be collected at each site after 2, 5, and 10 years. The percent cover of non-motile organisms and counts of motile species will be assessed from photographs taken of each plate and species identified to the lowest practical taxonomic unit. The first sets of plates were retrieved in September of 2014, the second set in October 2017. The pipes provide complex, hard substrate in an area otherwise devoid of rock and cobble and observations from the underwater video and findings from the settlement plates will be presented.