Restoration design and monitoring aim to answer key questions about the best methods for subtidal restoration, species use of restored reefs, and to assessing whether these types of treatments can provide physical benefits in addressing climate changes in San Francisco Bay. We have assembled an interdisciplinary team to build on previous restoration lessons and move toward integrating multiple habitats. The San Francisco Bay Living Shorelines: Near-shore Linkages Project is testing subtidal restoration techniques, restoring critical eelgrass and oyster habitat, testing the individual and interactive effects of restoration techniques on habitat values, beginning to evaluate connectivity between submerged areas and adjacent tidal wetlands and creeks, and testing alternatives to hard/structural stabilization, in a multi-objective project. Due to limited historical information on distribution and abundance of native oysters and eelgrass, we use the term “restoration” to mean enhancing valuable functions and services promoted by these types of features in SF Bay and elsewhere, rather than in the strict sense of replacing previously known distributions or extent.
Potential Climate Change Adaptation Approach
In addition, in developing the California (State Resources Agency) Climate Change Adaptation Strategy, state agencies have recommended the use of Living Shorelines as a potential adaptation method to reduce the need for engineered hard shoreline protection devices and to provide habitat functions and values. The State Coastal Conservancy Climate Change Policy also recommends implementation of Living Shorelines due to their ability to reduce erosion and trap sediment, allowing for both buffering of tidal wetlands and migration of habitats (“estuary rollover"), towards a goal of stronger estuarine habitat resiliency in the future with sea level rise and other climate-change-related projections.
Overarching Project Goal
To create biologically rich and diverse subtidal and low intertidal habitats, including eelgrass and oyster reefs, as part of a self-sustaining estuary system that restores ecological function and is resilient to changing environmental conditions.
1) Use a pilot-scale, experimental approach to establish native oysters and eelgrass at multiple locations in San Francisco Bay.
2) Compare the effectiveness of different restoration treatments in establishing these habitat-forming species.
3) Determine the extent to which restoration treatments enhance habitat for invertebrates, fish, and birds, relative to areas lacking structure and pre-treatment conditions.
4) Determine if the type of treatment (e.g., oyster reefs, eelgrass plantings, or combinations of oyster reefs and eelgrass) influences habitat values differently.
5) Begin to evaluate potential for subtidal restoration to enhance functioning of nearby intertidal mudflat, creek, and marsh habitats, e.g., by providing food resources to species that move among habitats.
6) Evaluate potential for living subtidal features to reduce water flow velocities, attenuate waves, and increase sedimentation, and assess whether different restoration treatments influence physical processes differently.
7) Determine if position in the Bay, and the specific environmental context at that location, influences foundational species establishment, habitat provision, and physical processes conferred by restoration treatments.
8) Where possible, compare the ability to establish restoration treatments, habitat functions, and physical changes along mudflats/wetlands versus armored shores.
We identified two locations in the Bay that would meet our most important site selection criteria, and should allow us to meet many of our objectives. In 2012, we constructed one of the project sites along a portion of the San Rafael shoreline for a majority of our work. In addition, we used a location offshore of Eden Landing Ecological Reserve, just south of the San Mateo Bridge on the east side of the Bay. More detail about these sites and the surrounding watersheds, water depths, land uses, etc., are included in the project description.
Two Experimental Designs:
Pacific Shell Bag Mounds—Larger scale experiment to test biological and physical effects. This experiment includes four 32 x 10m treatment plots situated parallel to the shore, approximately 200 m from shore. This design allows us to compare the effects of Pacific oyster shell bags, eelgrass, and both together, with a control of the same size. This experiment is at a large enough scale to compare effects on physical factors such as wave attenuation and accretion, as well as effects on biological properties that operate at larger scales (for example, bird and fish utilization, water quality interactions of oysters and eelgrass). The large experiment is at the TNC site only.
Baycrete Substrate element—Smaller scale experiment to examine small-scale biological effects. This experiment consists of replicate 1x1 m substrate elements of different types, intended to compare native oyster recruitment and growth parameters to inform future restoration projects. At TNC in 2012, this experiment was set up in the 30-m spaces between and on either side of the line of larger scale plots described above. At TNC, four oyster substrate types not tested in the large scale experiment (reef balls, mini reef ball stacks, layer cakes, and oyster blocks) are replicated 5 times, for a total of 20 elements. These elements are placed in groups (blocks) of four, with each of the four substrate types represented in each block.
A substrate element experiment will be the only project installed at Eden Landing in 2012. This is similar to that described for TNC in that it includes 1x1 m substrate elements replicated in 5 blocks and aligned parallel with the shoreline at about 200 m from shore. However, at Eden Landing, there are 5 substrate types: the 4 tested in the TNC substrate element experiment, plus the substrate type used in the larger scale project at TNC (oyster shell bags). In addition, there are 5 replicate 1x1m plots of eelgrass planted, one in each block, as well as a treatment that includes one of the oyster substrate types along with eelgrass planted directly adjacent to it. More detail about these designs is included in the project description.