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West Sacramento, CA, United States

Miles A.K.,U.S. Geological Survey | Van Vuren D.H.,University of California at Davis | Tsao D.C.,500 Industrial Boulevard | Yee J.L.,U.S. Geological Survey
California Fish and Game

As mitigation for habitat impacted by the expansion of a pier on Suisun Bay, California, two vehicle parking lots (0.36 ha and 0.13 ha) were restored by being excavated, graded, and contoured using dredged sediments to the topography or elevation of nearby wetlands. We asked if pickleweed (Sarcocornia pacifica L, [Amaranthaceae]) colonization could be enhanced by experimental manipulation on these new wetlands. Pickleweed dominates ecologically important communities at adjacent San Francisco Bay, but is not typically dominant at Suisun Bay probably because of widely fluctuating water salinity and is outcompeted by other brackish water plants. Experimental treatments (1.0-m2 plots) included mulching with pickleweed cuttings in either the fall or the spring, tilling in the fall, or applying organic enrichments in the fall. Control plots received no treatment. Pickleweed colonization was most enhanced at treatment plots that were mulched with pickleweed in the fall. Since exotic vegetation can colonize bare sites within the early phases of restoration and reduce habitat quality, we concluded that mulching was most effective in the fall by reducing invasive plant cover while facilitating native plant colonization. Source

Seesholtz A.M.,500 Industrial Boulevard | Manuel M.J.,Pacific States Marine Fisheries Commission | Van Eenennaam J.P.,University of California at Davis
Environmental Biology of Fishes

California’s Sacramento River mainstem was previously the only known spawning area for the Southern Distinct Population Segment of North American green sturgeon, Acipenser medirostris. Our study provides the first documentation of green sturgeon spawning in the Feather River, a major tributary of the Sacramento River. Egg mats were used to sample two lower Feather River sites from April 12 to July 7, 2011, and we collected 13 green sturgeon eggs at one of those sites. Developmental stages of the eggs ranged from early gastrulation (Stage 15) to post-neurulation (Stage 27), which led us to estimate that four independent spawning events occurred between June 12 and June 19. Spawning occurred after a flow increase while water temperatures were at an optimum (<17.5 °C) for eggs. Results suggest that the area near Thermalito Afterbay Outlet may be important green sturgeon spawning habitat and that the lower Feather River has the potential to provide a second production area of Southern Distinct Population Segment green sturgeon. It should be noted that 2011 was a wet water year and supplemental sampling is needed to understand if water-year type affects green sturgeon usage of the lower Feather River. Given this new information, future management decisions and water management strategies for the Feather River system should take green sturgeon life-history needs into consideration. © 2014, Springer Science+Business Media Dordrecht. Source

Brooks M.L.,Southern Illinois University Carbondale | Fleishman E.,University of California at Santa Barbara | Fleishman E.,University of California at Davis | Brown L.R.,U.S. Geological Survey | And 13 more authors.
Estuaries and Coasts

Human effects on estuaries are often associated with major decreases in abundance of aquatic species. However, remediation priorities are difficult to identify when declines result from multiple stressors with interacting sublethal effects. The San Francisco Estuary offers a useful case study of the potential role of contaminants in declines of organisms because the waters of its delta chronically violate legal water quality standards; however, direct effects of contaminants on fish species are rarely observed. Lack of direct lethality in the field has prevented consensus that contaminants may be one of the major drivers of coincident but unexplained declines of fishes with differing life histories and habitats (anadromous, brackish, and freshwater). Our review of available evidence indicates that examining the effects of contaminants and other stressors on specific life stages in different seasons and salinity zones of the estuary is critical to identifying how several interacting stressors could contribute to a general syndrome of declines. Moreover, warming water temperatures of the magnitude projected by climate models increase metabolic rates of ectotherms, and can hasten elimination of some contaminants. However, for other pollutants, concurrent increases in respiratory rate or food intake result in higher doses per unit time without changes in the contaminant concentrations in the water. Food limitation and energetic costs of osmoregulating under altered salinities further limit the amount of energy available to fish; this energy must be redirected from growth and reproduction toward pollutant avoidance, enzymatic detoxification, or elimination. Because all of these processes require energy, bioenergetics methods are promising for evaluating effects of sublethal contaminants in the presence of other stressors, and for informing remediation. Predictive models that evaluate the direct and indirect effects of contaminants will be possible when data become available on energetic costs of exposure to contaminants given simultaneous exposure to non-contaminant stressors. © 2011 Coastal and Estuarine Research Federation. Source

Maier K.L.,U.S. Geological Survey | Gatti E.,U.S. Geological Survey | Gatti E.,Jet Propulsion Laboratory | Wan E.,U.S. Geological Survey | And 5 more authors.
Quaternary Research (United States)

We document characteristics of tephra, including facies and geochemistry, from 27 subsurface sites in the Sacramento-San Joaquin Delta, California, to obtain stratigraphic constraints in a complex setting. Analyzed tephra deposits correlate with: 1) an unnamed tephra from the Carlotta Formation near Ferndale, California, herein informally named the ash of Wildcat Grade (<~1.450 to >~. 0.780. Ma), 2) the Rockland ash bed (~. 0.575. Ma), 3) the Loleta ash bed (~. 0.390. Ma), and 4) middle Pleistocene volcanic ash deposits at Tulelake, California, and Pringle Falls, Bend, and Summer Lake, Oregon, herein informally named the dacitic ash of Hood (<~0.211 to >~. 0.180. Ma). All four tephra are derived from Cascades volcanic sources. The Rockland ash bed erupted from the southern Cascades and occurs in up to >. 7-m-thick deposits in cores from ~. 40. m subsurface in the Sacramento-San Joaquin Delta. Tephra facies and tephra age constraints suggest rapid tephra deposition within fluvial channel and overbank settings, likely related to flood events shortly following volcanic eruption. Such rapidly deposited tephra are important chronostratigraphic markers that suggest varying sediment accumulation rates in Quaternary deposits below the modern Sacramento-San Joaquin Delta. This study provides the first steps in a subsurface Quaternary stratigraphic framework necessary for future hazard assessment. © 2015. Source

Sustaita D.,Silverado | Sustaita D.,University of Connecticut | Quickert P.F.,SAFE , LLC | Patterson L.,500 Industrial Boulevard | And 2 more authors.
Journal of Wildlife Management

We undertook a 2-year (2002-2004) mark-recapture study to investigate demographic performance and habitat use of salt marsh harvest mice (Reithrodontomys raviventris halicoetes) in the Suisun Marsh. We examined the effects of different wetland types and microhabitats on 3 demographic variables: density, reproductive potential, and persistence. Our results indicate that microhabitats dominated by mixed vegetation or pickleweed (Salicornia spp.) supported similar salt marsh harvest mouse densities, reproductive potential, and persistence throughout much of the year, whereas few salt marsh harvest mice inhabited upland grass-dominated microhabitats. We found that densities were higher in diked wetlands, whereas post-winter persistence was higher in tidal wetlands, and reproductive potential did not differ statistically between wetland types. Our results emphasize the importance of mixed vegetation for providing adequate salt marsh harvest mouse habitat and suggest that, despite their physiognomic and hydrological differences, both diked and tidal wetlands support salt marsh harvest mouse populations by promoting different demographic attributes. We recommend that habitat management, restoration, and enhancement efforts include areas containing mixed vegetation in addition to pickleweed in both diked and tidal wetlands. Copyright © 2011 The Wildlife Society. Source

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