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As part of the Regional Monitoring Program (RMP) and the USGS’s long-term Wildlife Contaminants Program, the USGS samples double-crested cormorant (Phalacrocorax auritus) and Forster’s tern (Sterna forsteri) eggs throughout the San Francisco Bay Estuary approximately every three years to assess temporal trends in contaminant concentrations. This sampling has been carried out in 2006, 2009, and 2012. Although RMP sampling was scheduled to take place in 2015, it was delayed until 2016. This document summarizes egg collections for 2016, as well as mercury concentrations in Forster’s tern eggs on an individual egg basis.
Several lines of evidence from the Regional Monitoring Program and other studies have suggested that sediment grain size characteristics influence amphipod (Eohaustorius estuarius) survival in 10 day toxicity tests. Two workshops were convened to address the influence of non-contaminant factors on amphipod toxicity tests, and the current project was prioritized based on the recommendations of experts participating in these workshops. The study was designed to investigate the effects of kaolin clay on amphipod survival since this is the dominant clay type in Francisco Estuary sediments. In these experiments reference sand was spiked with increasing concentrations of kaolin to determine whether there was a dose-based relationship between amphipod mortality and increasing concentrations of this type of clay. Wild-caught E. estuarius were collected from Beaver Creek Beach (Oregon) and supplied by Northwest Aquatic Sciences. The initial experiment did not demonstrate a dose-response relationship: E. estuarius survival in all concentrations from 10% to 100% kaolin was lower than in the sand control, and survival in the clay spiked sand was also highly variable. This experiment exposed a mixture of amphipod size classes representative of those typically provided by the amphipod supplier. Reasoning that variable response to clay was related to variable tolerances by the different amphipod size classes, a follow-up experiment was conducted to investigate this relationship. Amphipods were separated into small, medium and large size classes and these were exposed to 100% kaolin. These results showed survival in 100% clay was 86%, 82% and 66% by small, medium and large amphipods, respectively. To further investigate size-related responses to clay, small, medium and large amphipods were exposed to concentrations of sand spiked with clay from 0 to 100%. The results of this experiment showed that smaller amphipods tolerated high clay concentrations better than larger animals, but there was not a strict monotonic dose-response relationship. Conclusions based on this experiment were constrained by an inability to sort amphipods into three distinct size classes, because there were not enough of the largest animals present at the Oregon collection site. In addition, grain size analysis of the sand spiked clay suggested that the clay tended to flocculate in the treatments above 70% kaolin. This experiment was repeated when three distinct size classes were present in December 2014. The results of this experiment also showed that smaller amphipods tolerated high kaolin better than larger amphipods. As in the previous experiment, there was not a monotonic response to clay, especially at the higher kaolin concentrations, and the grain size analysis also showed flocculation occurred in the highest clay treatments. Despite these inconsistencies, the results of this experiment suggest that tolerance of E. estuarius to clay varies with amphipod size. Average survival was 81%, 79%, and 65% for small, medium and large amphipods, respectively in concentrations > 50% clay. Possible mechanisms for size specific clay effects on this amphipod species include lower survival related to reduced energy reserves in larger animals, inhibition of gill function, and inhibition of feeding and locomotion through clogging of amphipod setae. The results suggest that use of smaller amphipods in routine monitoring of high clay sediments will reduce the influence of this factor on test results. Additional experiments with high clay reference site sediments from San Francisco Bay are recommended to confirm the size related response with field sediments.
One component of the Sycamore Alluvial Woodland Habitat Mapping and Regeneration Studies Project is this annotated bibliography of existing scientific literature pertaining to California sycamore ecology. This annotated bibliography is a product of an extensive review into documents, mapping efforts, and personal communications, and presents sources that have been determined to be relevant to understanding the factors that influence California sycamore health and regeneration in central California. The annotated bibliography is divided into the following sections by topic: General Ecology; Historical and Present Distribution; Restoration Ecology and Management; Wildlife Ecology; Geomorphology; Hydrology and Soils; and Health and Regeneration. Each item is briefly summarized and its relevance to the project is described. References that fall under multiple categories are cross-referenced within the document. Similarly, key words are indicated or each reference to highlight various subtopics affecting California sycamore ecology.
This study reconstructs the historical landscape of the Petaluma River watershed and documents the major landscape changes that have taken place within the watershed over the past two centuries. Prior to Spanish and American settlement of the region, the Petaluma River watershed supported a dynamic and interconnected network of streams, riparian forests, freshwater wetlands, and tidal marshes. These habitats were utilized by a wide range of plant and animal species, including a number of species that are today listed as threatened or endangered such as Ridgway’s Rail, Black Rail, salt marsh harvest mouse, California red-legged frog, Central California Coast steelhead, and soft bird’s beak (CNDDB 2012, SRCD 2015). Agricultural and urban development beginning in the mid-1800s has significantly altered the landscape, degrading habitat for fish and wildlife and contributing to contemporary management challenges such as flooding, pollutant loading, erosion, and sedimentation. While many natural areas and remnant wetlands still exist throughout the watershed—most notably the Petaluma Marsh—their ecological function is in many cases seriously impaired and their long-term fate jeopardized by climate change and other stressors. Multi-benefit wetland restoration strategies, guided by a thorough understanding of landscape history, can simultaneously address a range of chronic management issues while improving the ecological health of the watershed, making it a better place to live for both people and wildlife.
This study synthesizes a diverse array of data to examine the ecological patterns, ecosystem functions, and hydrology that characterized a central portion of the Laguna de Santa Rosa during the mid-19th century, and to analyze landscape changes over the past 150 years. The primary purpose of this study was to help guide restoration actions and other measures aimed at reducing nutrient loads within this portion of the Laguna de Santa Rosa watershed.
As sea level rise accelerates, our shores will be increasingly vulnerable to erosion. Particular concern centers around the potential loss of San Francisco Bay’s much-valued tidal marshes, which provide natural flood protection to our shorelines, habitat for native wildlife, and many other ecosystem services. Addressing this concern, this study is the first systematic analysis of the rates of marsh retreat and expansion over time for San Pablo Bay, located in the northern part of San Francisco Bay.
• Over the past two decades, more of the marshes in San Pablo Bay have expanded (35% by length) than retreated (6%).
• Some areas have been expanding for over 150 years.
• Some marsh edges that appear to be retreating are in fact expanding rapidly at rates of up to 8 m/yr.
• Marsh edge change may be a useful indicator of resilience, identifying favorable sites for marsh persistence.
• These data can provide a foundation for understanding drivers of marsh edge expansion and retreat such as wind direction, wave energy, watershed sediment supply, and mudflat shape.
• This understanding of system dynamics will help inform management decisions about marsh restoration and protection.
• This study provides a baseline and method for tracking marsh edge response to current and future conditions, particularly anticipated changes in sea level, wave energy, and sediment supply.
Recommended next steps:
• This pilot study for San Pablo Bay marshes should be extended to other marshes in San Francisco Bay.
• These initial marsh expansion and retreat findings should be further analyzed and interpreted to improve our understanding of system drivers and identify management responses.
• A program for repeated assessment should be developed to identify and track changes in shoreline position, a leading indicator of the likelihood marsh survival.
This study investigates the relative distribution, health, and regeneration patterns of two major stands of sycamore alluvial woodland (SAW), representing managed and natural settings. Using an array of ecological and geomorphic field analyses, we discuss site characteristics favorable to SAW health and regeneration, make recommendations for restoration and management, and identify next steps. Findings from this study will contribute to the acquisition, restoration, and improved management of SAW as part of the Santa Clara Valley Habitat Plan (VHP).
Context Effective river restoration requires understanding a system’s potential to support desired functions. This can be challenging to discern in the modern landscape, where natural complexity and heterogeneity are often heavily suppressed or modified. Historical analysis is therefore a valuable tool to provide the long-term perspective on riverine patterns, processes, and ecosystem change needed to set appropriate environmental management goals and strategies.
Objective In this study, we reconstructed historical (early 1800s) riparian conditions, river corridor extent, and dry-season flow on the lower Santa Clara River in southern California, with the goal of using this enhanced understanding to inform restoration and management activities.
Method Hundreds of cartographic, textual, and visual accounts were integrated into a GIS database of historical river characteristics.
Results We found that the river was characterized by an extremely broad river corridor and a diverse mosaic of riparian communities that varied by reach, from extensive ([100 ha) willow-cottonwood forests to xeric scrublands. Reach-scale ecological heterogeneity was linked to local variations in dry-season water availability, which was in turn underpinned by regional geophysical controls on groundwater and surface flow.
Conclusions Although human actions have greatly impacted the river’s extent, baseflow hydrology, and riparian habitats, many ecological attributes persist in more limited form, in large part facilitated by these fundamental hydrogeological controls. By drawing on a heretofore untapped dataset of spatially explicit and long-term environmental data, these findings improve our understanding of the river’s historical and current conditions and allow the derivation of reach-differentiated restoration and management opportunities that take advantage of local potential.
Ecological resilience is a powerful heuristic for ecosystem management in the context of rapid environmental change. Significant efforts are underway to improve the resilience of biodiversity and ecological function to extreme events and directional change across all types of landscapes, from intact natural systems to highly modified landscapes such as cities and agricultural regions. However, identifying management strategies likely to promote ecological resilience remains a challenge. In this article, we present seven core dimensions to guide long-term and large-scale resilience planning in highly modified landscapes, with the objective of providing a structure and shared vocabulary for recognizing opportunities and actions likely to increase resilience across the whole landscape. We illustrate application of our approach to landscape-scale ecosystem management through case studies from two highly modified California landscapes, Silicon Valley and the Sacramento–San Joaquin Delta. We propose that resilience-based management is best implemented at large spatial scales and through collaborative, cross-sector partnerships.