Authors:Schacter; Carley R.
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Hartman, C. Alex
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Herzog, Mark P.
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Peterson, Sarah H.
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Tarjan, L. Max
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Wang, Yiwei
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Strong, Cheryl
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Tertes, Rachel
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Warnock, Nils
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Ackerman, Joshua T. Abstract: The South Bay Salt Pond Restoration Project aims to restore many former salt production ponds, now managed for wildlife and water quality, to tidal marsh. However, because managed ponds support large densities of breeding waterbirds, reduction of pond habitat may influence breeding waterbird distribution and abundance. We investigated habitat use associated with breeding, feeding, and roosting behaviors during the breeding season for American Avocets (Recurvirostra americana), Black-necked Stilts (Himantopus mexicanus), Forster’s Terns (Sterna forsteri), and Caspian Terns (Hydroprogne caspia) in south San Francisco Bay in 2019 after substantial tidal marsh restoration, and compared results to a 2001 survey (before restoration). In 2019, managed ponds (26% of currently available habitat) were selected by waterbirds engaged in breeding behaviors (> 39% of observations), foraging (> 42%), and roosting (> 73%). Waterbirds avoided tidal... PubDate: Thu, 8 Jun 2023 00:00:00 +0000
Authors:Hutton; Paul H.
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Roy, Sujoy B. Abstract: The deviation of specific electrical conductance (EC) from conservative mixing behavior is well-established in the scientific literature. This principle is based on the observation that, as salt concentration in a water sample increases, the mobility of individual ions in the sample decreases, and thus their ability to conduct electricity decreases. Despite this fact, some commonly used models for salinity transport in the San Francisco Estuary (estuary) utilize EC as a primary simulation constituent, treating it as a conservative quantity. Such a modeling approach has likely been followed to exploit the wide availability of EC data for model calibration and validation, and to obviate the need to translate between EC and salinity in a domain characterized by multiple source waters with varying ionic make-ups. Arguably, this approach provides a reasonable trade-off between data translation error and model simulation error. In this paper, we critically evaluate this approach, employing... PubDate: Thu, 8 Jun 2023 00:00:00 +0000
Authors:Lee; Calvin Y.
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Smith, April G.
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Hassrick, Jason L.
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Kalmbach, Andrew J.
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Sabal, Megan C.
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Cox, Daniel M.
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Grimaldo, Lenny F.
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Schultz, Andrew Abstract: Zooplankton density and community composition in estuaries can be affected by variation in freshwater inputs, with important implications for higher trophic levels. In the San Francisco Estuary, management agencies have initiated autumn flow augmentations in the form of changes to reservoir releases or to exported water from the South Delta to increase and improve available habitat for endangered Delta Smelt, Hypomesus transpacificus, during the season when their body condition most influences fecundity. Autumn flow augmentation only occurs in years with higher precipitation, effectively moving the Low-Salinity Zone (LSZ) downstream to key foraging habitats for Delta Smelt in Suisun Bay and Suisun Marsh. To assess whether augmented flow enhanced prey resources for Delta Smelt, we compared autumn zooplankton abundance, biomass, spatial distribution, and community composition in years when flow was augmented (2017, 2019) with reference years when flow was not augmented... PubDate: Thu, 8 Jun 2023 00:00:00 +0000
Authors:Lacy; Jessica R.
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Dailey, Evan T.
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Morgan–King, Tara L. Abstract: We investigated wind-wave and suspended-sediment dynamics in Little Holland Tract and Liberty Island, two subsided former agricultural tracts in the Cache Slough complex in the northern Sacramento-San Joaquin Delta which were restored to tidal shallows to improve habitat. Turbidity, and thus suspended-sediment concentration (SSC), is important to habitat quality because some species of native fishes, including the Delta Smelt, are found preferentially in more turbid waters. Data from October 2015 to August 2016 show that average SSC was greater within Little Holland Tract than in the primary breach that connects the basin to surrounding channels: approximately twice as great at a shallower station farther from the breach and 15% greater at a deeper station closer to the breach. Suspended-sediment concentration within Little Holland Tract was directly related to wave shear stress and inversely related to water depth, based on linear regression. We used measurements of suspended-sediment... PubDate: Tue, 21 Mar 2023 00:00:00 +000
Authors:Howard; Ian M.
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Stahle, David W.
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Torbenson, Max C. A.
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Granato–Souza, Daniela
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Poulsen, Cody Abstract: Subsets of annual and sub-annual tree-ring chronologies are used to reconstruct seasonal precipitation totals in northern California. The specific seasons selected for reconstruction are based on the strongest monthly precipitation signals recorded in the tree-ring data. Earlywood width of gray pine is best correlated with Oct-Dec precipitation at the onset of the wet season. Latewood width of ponderosa pine is correlated with Mar–Apr totals at the end of the wet season. These earlywood and latewood width chronologies are used to develop separate reconstructions of precipitation for the “autumn” (Oct–Dec) and “spring” (Mar–Apr) seasons. Total ring-width chronologies of blue oak are highly correlated with October–April precipitation totals and are used to reconstruct precipitation for the “wet season.” We then computed one additional skillful reconstruction by subtracting the reconstructed spring totals from the wet season precipitation estimates (i.e., “winter” [Oct–Feb]). We... PubDate: Tue, 21 Mar 2023 00:00:00 +000
Authors:Sommer; Ted
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Conrad, J. Louise
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Culberson, Steven Abstract: Science is the foundation for a wide range of activities, including evaluation, innovation, and technology, which in turn support management. Without good science, resource management in regions such as the San Francisco Estuary is handicapped, and must proceed with outdated conceptual models, operating strategies, and technologies. At the same time, we recognize that poor communication can interfere with conversations between scientists and managers, even when high-quality data and publications are available. In this essay, we have tried to address an important part of this issue: helping scientists to understand how to produce actionable science. Our hope is that these suggestions will, at the least, help improve dialog between scientists and the managers responsible for the estuary’s resources. PubDate: Tue, 21 Mar 2023 00:00:00 +000
Authors:Mussen; Timothy D.
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Driscoll, Sara
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Cook, Michael E.
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Nordin, Justin D.
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Guerin, Marianne
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Rachiele, Richard
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Smith, Donald J.
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Mine Berg, Gry
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Thompson, Lisa C. Abstract: Phytoplankton subsidies from river inputs and wetland habitats can be important food sources for pelagic organisms in the Sacramento–San Joaquin Delta (Delta). However, while the Sacramento River is a key contributor of water to the Delta, providing 80% of the mean annual inflow, the river is only a minor source of phytoplankton to the system. The reason for low phytoplankton biomass in the Sacramento River is not well understood but appears to be associated with a 65-km stretch of the lower river where chlorophyll-a (Chl-a) concentrations can decline by as much as 90%. We conducted two surveys along the lower Sacramento River, in spring and fall of 2016, to investigate the relative contributions of different factors potentially driving this Chl-a decline. Our study evaluated the change in Chl-a concentrations as a result of dilution from tributaries, light availability, nutrient concentrations, nutrient uptake, phytoplankton productivity, zooplankton grazing, and clam grazing.... PubDate: Tue, 21 Mar 2023 00:00:00 +000
Authors:Hestir; Erin
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Dronova, Iryna Abstract: Remote-sensing methods are being used to study a growing number of issues in the San Francisco Estuary, such as (1) detecting the optical properties of chlorophyll-a concentrations and dissolved organic matter to assess productivity and the nature of carbon inputs, (2) creating historical records of invasive aquatic vegetation expansion through space and time, (3) identifying origins and expansions of invasions, and (4) supporting models of greenhouse-gas sequestration by expanding restoration projects. Technological capabilities of remote sensing have likewise expanded to include a wide array of opportunities: from boat-mounted sensors, human-operated low-flying planes, and aerial drones, to freely accessible satellite imagery. Growing interest in coordinating these monitoring methods in the name of collaboration and cost-efficiency has led to the creation of diverse expert teams such as the Remote Imagery Collaborative, and monitoring frameworks such as the Interagency... PubDate: Thu, 2 Feb 2023 00:00:00 +0000
Authors:Windham–Myers; Lisamarie
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Oikawa, Patty
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Deverel, Steve
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Chapple, Dylan
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Drexler, Judith Z.
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Stern, Dylan Abstract: The aquatic landscapes of the Sacramento–San Joaquin Delta (hereafter, the Delta) and Suisun Bay represent both a significant past and future soil carbon stock. Historical alterations of hydrologic flows have led to depletion of soil carbon stocks via emissions of carbon dioxide (CO2), and loss of elevation as a result of subsidence. Optimizing ecosystem hydrology in the Delta and Suisun Bay could both reduce and reverse subsidence while also providing significant opportunities for climate mitigation and adaptation. Emissions of greenhouse gases (GHGs)—notably CO2, methane (CH4 ), and nitrous oxide (N2O)—contribute to global warming at different rates and intensities, requiring GHG accounting and modeling to assess the relative benefits of management options. Decades of data collection, model building, and map development suggest that past and current management actions have both caused—and can mitigate—losses of soil carbon. We review here the magnitude of potential GHG offsets,... PubDate: Wed, 1 Feb 2023 00:00:00 +0000
Authors:Boyer; Katharyn E.
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Safran, Samuel M.
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Khanna, Shruti
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Patten, Melissa V. Abstract: Conversion of wetlands in the Sacramento–San Joaquin Delta beginning in the mid-1800s resulted in a pronounced shift from a wetland-dominated food web to one driven by open-water primary producers. Submersed and floating aquatic vegetation (SAV and FAV) now rank highest in potential net primary production (NPP) among producer groups, and provide a comparable amount of carbon to the detrital food web as marshes. However, important details of this contribution that relate to shifts in species composition and habitat extent were not understood. Here, we review how changes in aquatic vegetation influence NPP and trophic support from the historical to modern periods, within the modern period (the last 2 decades), and under future management and climate scenarios. We estimate that NPP of SAV and FAV during the historical period was approximately half that of today, before increases in open water and introduction of the highly productive water primrose. During the modern period (the... PubDate: Wed, 1 Feb 2023 00:00:00 +0000
Authors:Christman; Mairgareth A.
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Khanna, Shruti
,
Drexler, Judith Z.
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Young, Matthew J. Abstract: Substantial increases in non-native aquatic vegetation have occurred in the upper San Francisco Estuary over the last 2 decades, largely from the explosive growth of a few submerged and floating aquatic plant species. Some of these species act as ecosystem engineers by creating conditions that favor their further growth and expansion as well as by modifying habitat for other organisms. Over the last decade, numerous studies have investigated patterns of expansion and turn-over of aquatic vegetation species; effects of vegetation on ecosystem health, water quality, and habitat; and effects of particular species or communities on physical processes such as carbon and sediment dynamics. Taking a synthetic approach to evaluate what has been learned over the last few years has shed light on just how significant aquatic plant species and communities are to ecosystems in the Sacramento-San Joaquin Delta. Aquatic vegetation affects every aspect of the physical and biotic environment,... PubDate: Wed, 1 Feb 2023 00:00:00 +0000
Authors:Conrad; J. Louise
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Thomas, Madison
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Jetter, Karen
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Madsen, John
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Pratt, Paul
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Moran, Patrick
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Takekawa, John
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Darin, Gina Skurka
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Kenison, Lydia Abstract: Invasive aquatic vegetation (IAV) is a management challenge in the Sacramento–San Joaquin Delta and the Suisun Marsh that has commanded major resource investment for 4 decades. We review the history and supporting science of chemical, biological, and mechanical control of IAV in the Delta and Suisun March, and in flowing waters outside the region. Outside the Delta, there is a significant history of research on IAV control in lotic systems, but few studies come from tidal environments, and we found no investigations at a spatial scale like that of the Delta. The science of control efforts in the Delta is nascent but has seen marked growth over the recent decade. Since 1983, control of invasive submerged and floating species has been centralized within the California State Parks Division of Boating and Waterways (CDBW). The program relies on herbicides, with an annual budget that has exceeded $12.5 million since 2015. However, the results have been mixed because of the challenge... PubDate: Wed, 1 Feb 2023 00:00:00 +0000
Authors:Kudela; Raphael M.
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Howard, Meredith D. A.
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Monismith, Stephen
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Paerl, Hans W. Abstract: Harmful algal blooms (HABs) are on the rise worldwide. Known drivers for the proliferation and intensification of HAB events include increasing nutrient pollution, climate change, regulation and modification of hydrological flow, and the combined effect of climate drivers and nutrient pollution. The San Francisco Bay–Delta system has largely been immune to severe or acute HAB events, but there is both a potential and realized threat which has been underestimated and under-reported, in part because of the lack of coordinated sampling and data reporting. There is also increasing evidence that HABs must be considered in the context of a freshwater-to-marine continuum, and that the physical and political boundaries separating components of the Bay–Delta system are porous barriers to HABs and their toxins. Much remains to be learned about the ecology and physiology of HAB organisms in this system, but five primary environmental drivers can be identified: temperature, salinity, irradiance,... PubDate: Wed, 1 Feb 2023 00:00:00 +0000
Authors:Larsen; Laurel G.
,
Bashevkin, Samuel M.
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Christman, Mairgareth A.
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Conrad, J. Louise
,
Dahm, Clifford A.
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Thompson, Janet Abstract: The Sacramento–San Joaquin Delta (Delta) is a case-study of the Anthropocene “great accelerations,” with exponentially increasing temperatures and sea level over time, leading to rapid change in other ecosystem components. In nearly all these interconnected changes and across scales, primary producers play a major role, with diverse effects that mitigate or exacerbate the rapid change induced by climate or other human-driven perturbations. Through this anthropocentric lens, primary producers can be viewed as performing numerous ecosystem services—which ultimately benefit humans—as well as ecosystem disservices, which negatively affect human communities. For example, through carbon sequestration, wetlands can perform ecosystem services of mitigating warming at a global scale and combating relative sea-level rise at a local scale, while generating food that supports regional food webs and fisheries. On the other hand, invasive aquatic vegetation (IAV) can trap sediment before it... PubDate: Wed, 25 Jan 2023 00:00:00 +000
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