San Diego State University - La Lobera

Restoration Project

San Diego State University - La Lobera

Restoration Objective:

This study examined sites post disturbance and conducted field manipulations to investigate factors driving temporal variability in the southern limit of Macrocystis pyrifera.

Site Selection Criteria:

Sites were selected 500 m apart that were located 1–3 km south of the then southern limit of M. pyrifera.

Cause Of Decline:

The giant kelp, Macrocystis pyrifera, forms dense forests on shallow rocky reefs along the west coast of North America, from central Baja California, Mexico, to central California, USA. Over the past two decades, several El Niños of varying strength have impacted the eastern Pacific Ocean and resulted in widespread mortality in M. pyrifera along the west coast of North America and increased variability in the location of the species’ southern range limit along the Baja California peninsula. Although these populations have generally recovered within 1–2 years after the El Niños ended, longer term changes near the species’ southern range limit may also have resulted from competitive interactions with subsurface kelps and turf algae that were able to survive the El Niños.

Key Reasons For Decline:


Scientific Paper

Delayed recovery of giant kelp near its southern range limit in the North Pacific following El Niño

M.S. Edwards, G. Hernandez-Carmona
Marine Biology, Vol. 147.

Site Observations:

Observation Date

1st Jun 2000 – 1st Jun 2001

Action Summary:

Three sites were chosen in which all E. arborea was cleared by cutting sites a few centimetres above the substrate and transporting the thalli away in mesh bags. In addition, an unmanipulated control area of equal size was established adjacent to each clearing. The recolonisation of E. arborea and M. purifera was then observed.

Lessons Learned:

Measurements were taken both 4 months and 1 year following the start of the experiment to study recolonisation patterns.

Project Outcomes:

The observational and experimental results of this study suggest that M. pyrifera is removed from its southern limit by the high temperatures and large waves associated with El Niños, while E. arborea is able to survive and recruit in high densities and thereby delay or even prevent M. pyrifera recovery. Observational studies showed in areas where E. aborea and M. pyrifera co-occurred, their densities were negatively correlated over the 5 years of this study. The field experiment showed that at both 4 months and 1 year after areas occupied by E. arborea were cleared, substantial recruitment of M. Pyrifera occurred, while recruitment was negligible in uncleared areas.

Key Reasons For Decline:


Area of Restoration (Ha)


Indicator Data:


Ending Value:

Starting Value:

Adult Kelp Count

Transplant Info: