Bay Foundation - Underwater Arch

Restoration Project

Bay Foundation - Underwater Arch

Restoration Objective:

This project aimed to restore kelp forests to rocky reefs to improve the biomass and productivity associated with rocky reefs. It also aimed to engage the local community in management of the kelp forest ecosystem.

Site Selection Criteria:

Sites were selected that historically had populations of kelp.

Cause Of Decline:

California kelp forests have been severely depleted by human activity, mainly overfishing, which has caused several ecological shifts within the habitat, primarily attributed to the loss of key predator species, including otters and predatory fish. This has resulted in an increased abundance of sea urchins, contributing to kelp overgrazing.

Key Reasons For Decline:


Scientific Paper

Palo Verdes kelp forest restoration project, year 5: July 2017–June 2018. The Bay Foundation

P. House, A. Barilotti, H. Burdick, T. Ford, J. Williams, C. Williams, D. Pondella
Los Angeles CA.


Site Observations:

Observation Date

13th Jun 2013 – 22nd Jun 2017

Action Summary:

Citizen scientists culled urchins, reducing sea urchin density from as high as 100 sea urchins per square meter to < 2 sea urchins per square meter.

Lessons Learned:

This project shows the success of using community engagement and in particular collaboration with commercial urchin fishers to curb urchin density for kelp restoration. Urchins were removed periodically when densities were seen to increase above 2 urchins per square metre.

Project Outcomes:

Underwater Arch Cove was observed to support no more than two urchins per square metre in fall 2015. However in year 4 of the project, one area showed more than 2 urchins per square metre in summer 2016, but this was largely contained and then controlled. In year 5 of the project Underwater Arch looked to be on track with giant kelp, fish biomass, and invertebrates with lowered purple urchin densities. However, during annual monitoring at the end of year 5 another section was observed with high urchin densities.

Key Reasons For Decline:


Area of Restoration (Ha)


Indicator Data:


Ending Value:

Starting Value:

Adult Kelp Count