Restoration Project

Pacific Shellfish Institute - Puget Sound

Restoration Objective:

This artificial reef was installed to mitigate the loss of intertidal rearing habitat caused by development of a large marina.

Site Selection Criteria:

The elevation of the habitat was chosen at a level thought to be most suitable for salmonoids. The mitigation area for the project was sized and located to optimally result in a doubling of epibenthic food resources in shallow subtidal and intertidal waters.

Cause Of Decline:

Mitigation was needed to offset the environmental cost of a new marina. In particular, the loss of epibenthic prey populations that are important to juvenile salmon and marine resident fish.

Key Reasons For Decline:

Physical Disturbance

Scientific Paper

Creation of rocky intertidal and shallow subtidal habitats to mitigate for the construction of a large marina in Puget Sound, Washington

D. Cheney, R. Oestman, G. Volkhardt, J. Getz, , Bulletin of Marine Science, Vol. 55.https://www.ingentaconnect.co...4/00000055/f0020002/art00040

Organisation:

Pacific Shellfish Institute

Site Observations:

Observation Date

1st Nov 1990 – 12th Jun 1991

Action Summary:

A 2.0 hectare rocky beach was constructed between -2.5 and +2.5m within a marine in late 1990 and early 1991 (Area N). In late 1990, a 3.0ha rocky beach and kelp habitat was created between 0 and -2.5m on the east side of the marina (Area B). In early 1990, an 0.2ha shallow rocky subtidal habitat was created between 0 and -2.5m on the west side of the marina (Area C). A control site was established west of the marina. The rocky habitats for Areas B and C were constructed by spreading approximately 5,400m of 10 to 20cm diameter, pit-run aggregate on an existing mud-sand bottom. The artificial beach (Area A) was constructed by layering 3,060m3 of 10 to 15cm diameter aggregate over a linear distance of 450 m of fill, then covering this material with a thin layer of 3 to 6cm diameter beach gravel.

Lessons Learned:

Notes a range of percent covers for the different tide heights of the reef, but these are estimated.

Project Outcomes:

There were substantial differences in benthic composition between the control and mitigation sites, with various kelp species (mainly Nereocystis, Laminaria and Sargassum) colonising the mitigation rock in all areas. Sand substrates were not utilised by attached micro-algae, but they were often covered either totally or partially with benthic diatoms and drift algae. The distribution and density of macroalgae generally increased between subsequent sampling periods in areas where suitable uncolonized substrates were available.

Key Reasons For Decline:

Physical Disturbance

Area of Restoration (In Square Metres)

32,000

Indicator Data:

Indicator:

Ending Value:

Starting Value:

Presence / Absence of Kelp

Costings:
Cost Currency:USD