Restoration Project

Fullerton University - Newport

Restoration Objective:

Silvetia is an important species in the intertidal zone as it provides food and shelter for many species and is highly productive. For these reasons, researchers attempted to re-establish Silvetia populations at specific locations on a southern California shore in a two-phase study which experimentally tested a series of biotic and abiotic factors that may impact restoration success.

Site Selection Criteria:

The four study sites were chosen based on similarities in physical characteristics and variations in the abundances of Silvetia. The sites are characterized by similar geologic origin, are moderately protected from large wave activity and are exposed to similar oceanographic regimes due to their close proximity, including temperature, salinity and wave action.

Cause Of Decline:

In California, increased urbanisation of coastal regions over the past several decades has resulted in increased anthropogenic disturbance and loss of fleshy seaweeds, including the rockweed Silvetia compressa. Like other canopy-forming, fleshy seaweeds, Silvetia is an important biogenic species in the mid-intertidal zone as it is highly productive, provides a source of food for many grazers and forms habitat for a diverse assemblage of seaweeds and invertebrates in southern California. This species also has low dispersal distances from parent populations, and as a consequence the rate of natural local recovery following extirpation is likely low.

Key Reasons For Decline:

Multiple

Scientific Paper

Reestablishment of the Southern California Rocky Intertidal Brown Alga, Silvetia compressa: An Experimental Investigation of Techniques and Abiotic and Biotic Factors That Affect Restoration Success

S.G. Whitaker, J.R. Smith, S.N. Murray, , Restoration Ecology, Vol. 18.https://doi.org/10.1111/j.1526-100X.2010.00717.x

Organisation:

Fullerton University

Site Observations:

Observation Date

1st Feb 2007 – 1st Feb 2008

Action Summary:

Juvenile Silvetia thalli were transplanted to four sites with a combination of simulated canopy and herbivore exclusion treatments. Two size classes of rockweeds (juveniles and reproductive adults) were transplanted on horizontal and partially shaded, north-facing vertical surfaces.

Lessons Learned:

Canopy cover enhanced survivorship of transplanted Silvetia thalli, but removal of grazers did not. Larger transplants exhibited the highest survival rates, and restoration results were promising.

Project Outcomes:

Transplant survival of juveniles from phase I was low (19%) at the end of the 12 month monitoring period, and although enhanced by the presence of a canopy; site and herbivore presence did not affect survival. In Phase II, transplant survival was moderate (36%) but lower than natural survival rates (67%). Larger thalli exhibited significantly higher survival rates than smaller thalli in both the transplanted and naturally occurring populations, particularly on vertical surfaces. Higher mortality on horizontal surfaces may have been due to differences in desiccation stress and human trampling.

Nature of Disturbance:

Higher mortality on horizontal surfaces may have been due to differences in desiccation stress and human trampling.

Key Reasons For Decline:

Multiple

Indicator Data:

Indicator:

Ending Value:

Starting Value:

Percent Survival

39.25
%
4.5
%
Costings:
Cost Currency:USD

Observation Date

1st Feb 2007 – 1st Feb 2008

Action Summary:

Juvenile Silvetia thalli were transplanted to four sites with a combination of simulated canopy and herbivore exclusion treatments. Two size classes of rockweeds (juveniles and reproductive adults) were transplanted on horizontal and partially shaded, north-facing vertical surfaces.

Lessons Learned:

Canopy cover enhanced survivorship of transplanted Silvetia thalli, but removal of grazers did not. Larger transplants exhibited the highest survival rates, and restoration results were promising.

Project Outcomes:

Transplant survival of juveniles from phase I was low (19%) at the end of the 12 month monitoring period, and although enhanced by the presence of a canopy; site and herbivore presence did not affect survival. In Phase II, transplant survival was moderate (36%) but lower than natural survival rates (67%). Larger thalli exhibited significantly higher survival rates than smaller thalli in both the transplanted and naturally occurring populations, particularly on vertical surfaces. Higher mortality on horizontal surfaces may have been due to differences in desiccation stress and human trampling.

Nature of Disturbance:

Higher mortality on horizontal surfaces may have been due to differences in desiccation stress and human trampling.

Key Reasons For Decline:

Multiple

Indicator Data:

Indicator:

Ending Value:

Starting Value:

Percent Survival

9.5
%
4.5
%
Costings:
Cost Currency:USD