Rocky Reef Ecology

The Portuguese Bend landslide on the Palos Verdes Peninsula began in the late 1950’s, releasing large amounts of sediments to the ocean between Whites Point and Abalone Cove and covering a large section of rocky reef habitat. Despite this source of sedimentation, productive rocky reef and kelp forest habitat extended well offshore and downshore towards Whites Point as recently as the late 1980’s. In the early 1990’s there were patches of buried reef adjacent to Portuguese Bend but this burial did not extend to the southeast. On June 2, 1999, a massive landslide occurred involving 17 acres near the Trump National Golf Course.

At present, in the region of the peninsula between Portuguese Bend and Point Fermin much of the historic low-lying reefs

continue to be heavily impacted by sedimentation due to reef burial and scour from these historic landslides. The only healthy reefs in the area are characterized by high-relief rocky outcrops that are resistant to the effects of sedimentation.

The Palos Verdes Reef Restoration Project seeks to restore rocky-reef habitat by emulating the form of the most productive extant reef in the region, KOU Rock (right), which consistently has greater fish biomass than any other reef on the peninsula.

Funding Source: NOAA Montrose Settlements Restoration Program

Lead Staff Researchers: Jonathan Williams, Matt Robart

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Adjacent to the largest urban area on the west coast of the United States, kelp forests in Santa Monica Bay are directly affected by anthropogenic impacts associated with urban development and population increase. These include an extensive and diverse set of stressors including commercial and recreational fishing, sedimentation, urban runoff, and pollution. Subtidal observations by Santa Monica Baykeeper in 2010 identified 61.5 hectares of nearshore rocky reef that were dominated by high densities of purple sea urchins and devoid of kelp. Subsequent community monitoring efforts have further qualified these barrens as areas featuring low diversity and productivity relative to areas of the Palos Verdes Peninsula that were currently supporting temporally and spatially stable giant kelp forests. Further, the urchins in these barrens are in poor physical condition with low gonadosomatic indices relative to urchins in neighboring kelp forests. The persistence of these urchin barrens, especially in the context of favorable conditions for giant kelp recruitment and development in southern California, argues for the active restoration of these barren reefs. The goals of this project is to reduce the density of purple sea urchins (Strongylocentrotus purpuratus) to two per square meter within the boundaries of sea urchin barrens off the Palos Verdes Peninsula, which will in turn minimize sea urchin grazing pressure and restore biogenic habitat to rocky reefs that historically supported kelp forests. Over time this will increase the spatial and temporal stability, biomass, and production associated with kelp forests and rocky reefs on the Palos Verdes Peninsula. The VRG assesses the response of these communities to restoration activities through annual subtidal monitoring at restoration sites.

Funding Source: NOAA Montrose Settlements Restoration Program

Partners: , , Commercial Sea Urchin Harvesters

Lead Staff Researcher: Jonathan Williams

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Press Release: New Hope for Kelp Beds and Commercial Fisheries after Sea Urchin Devastation

Habitat restoration is an important tool for managing degraded ecosystems, yet the success of restoration projects depends in part on adequately identifying preferred sites for restoration. Species distribution modeling using a machine learning approach provides novel tools for mapping areas of interest for restoration projects. Here we use stacked-species distribution models (s-SDMs) to identify candidate locations for installment of manmade reefs, a useful management tool for restoring structural habitat complexity and the associated biota in marine ecosystems. We created species distribution models for 21 species of commercial, recreational, ecological, or conservation importance within the Southern California Bight based on observations from long-term reef surveys combined with high resolution (200 x 200m) geospatial environmental data layers. We then combined the individual species models to create a stacked-species habitat suitability map, identifying over 800 km²of potential area for reef restoration within the Bight. The stacked-species distribution model provides insight for marine restoration projects in southern California specifically, but more generally this method can also be widely applied to other types of habitat restoration including both marine and terrestrial.

Funding Source: NOAA Saltonstall-Kennedy Grant

Lead Staff Researcher: Amanda Zellmer

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