Vantuna Research Group, Occidental College - Palos Verdes beach

Restoration Project

Vantuna Research Group, Occidental College - Palos Verdes beach

Restoration Objective:

It was designed as a series of high-relief modules to provide essential habitat for fishes and substrate for giant kelp, other marine algae, and marine invertebrates to become attached to. The intention was to create a productive rocky-reef ecosystem in an area with limited hard substrate that had previously been lost.

Site Selection Criteria:

Selected within a landslide impacted sediment zone but adjacent to natural reef and located in an area with favourable oceanographic conditions to support recruitment and recovery.

Cause Of Decline:

The 18th hole of what is now Trump National Golf Club slid into the ocean and onto the rocky reefs below in 1999, and long-term reef burial has been noted in all surveys since (e.g., Pondella et al., 2015; Pondella et al., 2018). Much of the historic low-lying reef continues to be impacted by chronic sedimentation due to reef burial, scour, and associated turbidity, significantly decreasing the amount of habitable rocky reef habitat in the area.

Key Reasons For Decline:

Sedimentation

Scientific Paper

Rebirth of a reef: As-built description and rapid returns from the Palos Verdes Reef Restoration Project

Williams, J. P., Williams, C. M., Pondella, D. J., & Scholz, Z. M. (2022).https://www.frontiersin.org/j...3389/fmars.2022.1010303/full

Organisation:

Vantuna Research Group, Occidental College

Site Observations:

Observation Date

8th May 2020 – 1st Nov 2021

Action Summary:

Quarry rock boulders were placed on top of previously buried rocky reef habitat that had been sedimented due to landslides. Natural succession was allowed to occur due to direct connectivity with nearby healthy reef and kelp habitat. The reef was monitored for 18 months following construction.

Quarry rock boulders were placed at a maximum sediment depth of 1 m, constructing approximately 2.76 ha of reef at 16.7–21.1 m depth with a mix of 1–4 m relief. Rock was transported across the Catalina Channel on a flat barge towed by tugboat, secured to a derrick barge, and placed using a front-end track loader along engineered gridlines.

Lessons Learned:

Constructing the reef on shallow sediment (<1 m) over buried hard substrate minimised long-term subsidence; high-relief design (1–4 m) improved resistance to sedimentation; and selecting a site with favourable oceanographic conditions and direct connectivity to healthy natural reef supported rapid recruitment and succession.

Project Outcomes:

PVR modules showed rapid, significantly positive responses in fish density, fish biomass, kelp density, and biotic benthic cover following reef construction. It appears that this high relief feature, coupled with immediate proximity to the natural reefs that support giant kelp, created a substrate that was optimal for kelp recruitment and a unique opportunity to examine rapid succession as it attracted a wide array of taxa almost immediately.

Area of Restoration (Ha)

3

Distance to nearest kelp forest (in metres)

1

Indicator Data:

Indicator:

Ending Value:

Starting Value:

Adult Kelp Density

21.0000
/ m2
0.1700
/ m2

Fish Density

0.9470
/ m2
0.0518
/ m2

Animal biomass

0.0611
g WW/m2
0.0084
g WW/m2
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