Delta smelt drought monitoring operations near Rio Vista, Photo by USFWS

SCIENCE NEWS: Rethinking Bay-Delta fish trends by combining multiple surveys; Evaluating non-native fish populations in the San Joaquin River; The secret life of water after a wildfire; and more …

Zooming out: Rethinking Bay-Delta fish trends by combining multiple surveys

The San Francisco Bay-Delta is among the most intensively studied ecosystems in the world. Numerous long-term fisheries monitoring programs have been conducted there since the late 1950s, but differences in the methods, scope, spatial coverage, and timing of these surveys make it difficult to compare and combine the data collected. As a result, researchers often rely on data from only one or a few of these surveys to identify patterns and draw conclusions about species trends. This fragmented approach provides an incomplete picture, which in turn can lead to incorrect inferences. To attempt a more holistic use of available information, a recent study by researchers from the University of California, Davis combined data from numerous surveys into multi-survey indices (Stompe et al. 2020). These indices could help more accurately detect trends in fish populations, and using them to reexamine existing hypotheses suggests that some commonly held beliefs about the Bay-Delta ecosystem, such as the Pelagic Organism Decline, may need to be reevaluated. … ” Read more from FishBio here: Zooming out: Rethinking Bay-Delta fish trends by combining multiple surveys

Video: Evaluating non-native fish populations in the San Joaquin River

Our newest video features our ongoing project to study the non-native fishes of the San Joaquin River in California’s Central Valley. Non-native fishes outnumber natives in the San Joaquin, but we know surprisingly little about them, such as the sizes of their populations. This video shows how we are using large, cylindrical fyke traps to catch bass and catfish for a mark-recaptures study. The species included in this study are striped bass, large and smallmouth bass, white catfish, and channel catfish.  The fish are marked with tags and released, in hopes of recapturing them again. Each time a tagged fish is recaptured, it gives us information about fish movements, and helps us estimate the size of the population. … ”  Read more from FishBio here:  Video: Evaluating non-native fish populations in the San Joaquin River

Drought and the Sacramento–San Joaquin Delta, 2012–2016: Environmental review and lessons

Droughts are common in California. The drought of 2012-2016 had no less precipitation and was no longer than previous historical droughts, but came with record high temperatures and low snowpack, which worsened many drought impacts. Water supplies for agriculture and urban users statewide struggled to meet water demands. Conservation and rationing, increased groundwater pumping and a diversified economy helped keep California’s economy robust in most sectors. The drought degraded environmental conditions in the Sacramento-San Joaquin Delta (Delta) as the region became saltier and warmer, invasive weeds spread, and iconic fishes like salmon and Delta smelt had strong declines. … ”  Read more from the California Water Blog here: Drought and the Sacramento–San Joaquin Delta, 2012–2016: Environmental Review and Lessons

Tahoe’s State of the Lake Report released

Turning out-of-control shrimp into dog treats, learning the lake physics of safe paddleboarding and maintaining a long-term data set during a pandemic are just some of the activities that have made for a unique year at Lake Tahoe.  Today, the UC Davis Tahoe Environmental Research Center released its annual Tahoe: State of the Lake Report. The report informs nonscientists about important factors affecting the health of Lake Tahoe. It also intends to provide the scientific underpinnings for ecosystem restoration and management decisions within the Lake Tahoe Basin. … ”  Read more from UC Davis here:  Tahoe’s State of the Lake Report released

UCI engineers evaluate snow drought in different parts of the world

Environmental engineers at the University of California, Irvine have developed a new framework for characterizing snow droughts around the world. Using this tool to analyze conditions from 1980 to 2018, the researchers found a 28-percent increase in the length of intensified snow-water deficits in the Western United States during the second half of the study period.  Results from the application of the new snow-water equivalent index and implications for human populations in impacted regions are covered in a study published today in Proceedings of the National Academy of Sciences.  “Snow is an important global water resource that plays a vital role in natural processes, agriculture, hydropower and basic socio-economic conditions of various regions,” said lead author Laurie Huning, UCI post-doctoral scholar in civil & environmental engineering. “While other forms of drought are well-studied, variations in snow droughts on a global scale have been examined to a far lesser extent until now.” … ”  Read more from the UC Irvine here: UCI engineers evaluate snow drought in different parts of the world

The secret life of water after a wildfire: Modeling the changes to the hydrological cycle after a wildfire

In the Western United States, we have seen increases in wildfire frequency and severity. The dry conditions from the onset of climate change has added fuel to the fire. The burning of tens to thousands of square kilometers has left profound changes to the landscape, primarily by removing vegetation, but also by leaving layers of ash and burnt soil. Undoubtedly, these changes to the landscape perturb the balance of hydrological processes. However, the complex feedbacks between these processes makes anticipating the changes to the hydrological cycle challenging.  In California, many of the wildfires occur in the Sierra Nevada mountains, which are the source of 70% of California’s water resources.  Understanding the feedbacks and implications of disturbances on the hydrological cycle can help watershed managers plan for future scenarios with wildfires and climate extremes.  … ”  Read more from AGU-H3S here:  The secret life of water after a wildfire

Surfs up!  Celebrating public recreation and shorebird conservation at Surf Beach in Santa Barbara County

Photo credit: Ron LeValley/USFWS

In a way that truly embodies the spirit of Californians who banded together to pass the Coastal Act 44 years ago, the U.S. Fish and Wildlife Service, Vandenberg Air Force Base, California Coastal Commission and the community of Lompoc came together this year to amend a closure policy to provide increased beach access to their closest beach, Surf Beach in Santa Barbara County.  Managed by Vandenberg Air Force Base, Surf Beach is home to tiny shorebirds that have been tirelessly fighting for survival after years of habitat loss and human activity. Western snowy plovers, often confused with the much more common sanderling, are a threatened species under the Endangered Species Act and have benefited from protections from human disturbance during the critical summertime breeding season at Surf Beach. … ”  Read more from the US FWS here: Surfs up!  Celebrating public recreation and shorebird conservation at Surf Beach in Santa Barbara County

America’s elusive crayfish and the eDNA that’s finding them

The Shasta crayfish and signal crayfish are two similar looking arthropods on two very different ecological trajectories. As one spreads in abundance, originating in the Pacific Northwest and spreading throughout the world, the other has been reduced to a handful of remaining populations spread throughout one river and its tributaries.  Pacifastacus leniusculus – the signal crayfish – has met few obstacles in its widely successful expansion from the Pacific Northwest southward in California and Nevada, as well as Europe and Japan. By some expert accounts, it has reached invader status. And while invasive species are rarely good for the surrounding food webs, it’s Pacifastacus fortis – the Shasta crayfish – that’s suffered the most at the signal crayfish’s fortune. … ”  Read more from Environmental Monitor here: America’s elusive crayfish and the eDNA that’s finding them

Satellite survey shows California’s sinking coastal hotspots

A majority of the world population lives on low lying lands near the sea, some of which are predicted to submerge by the end of the 21st century due to rising sea levels.  The most relevant quantity for assessing the impacts of sea-level change on these communities is the relative sea-level rise—the elevation change between the Earth’s surface height and sea surface height. For an observer standing on the coastland, relative sea-level rise is the net change in the sea level, which also includes the rise and fall of the land beneath observer’s feet. … ”  Read more from PhysOrg here: Satellite survey shows California’s sinking coastal hotspots

Bay Area coastal flooding triggers regionwide commute disruptions

For decades, the low-lying neighborhoods along the San Francisco Bay have experienced coastal flooding and the subsequent traffic disruptions. But a new computational model by Stanford researchers reveals that, due to the nature of road networks in the region, commuters living outside the areas of flooding may experience some of the largest commute delays.  By integrating traffic models with regional flood maps, researchers have demonstrated how San Francisco Bay Area commute disruptions spread substantially inland, creating longer delays for communities with sparse road networks than for those in the areas of flooding. … ”  Read more from PhysOrg here: Bay Area coastal flooding triggers regionwide commute disruptions

Q&A: Meet Letitia Grenier, newest PPIC CalTrout Ecosystem Fellow

We are excited to introduce Letitia Grenier — Senior Scientist at the San Francisco Estuary Insitute and Aquatic Science Center — as the second appointed Public Policy Institute of California (PPIC) CalTrout Ecosystem Fellow! We recently got to know her through an interview. Check out her answers in our latest post. … 1. How does it feel to be the second CalTrout Ecosystem PPIC Fellow?  Very exciting. I feel honored to be given this opportunity!  The chance to think at a higher level, synthesize across many successful projects, and connect with people who have innovated in the realm of ecosystem restoration is unique and precious.  I feel like I am getting the opportunity to learn in a new area and apply my knowledge and experience in a new way. … ”  Read more from Cal Trout here: Q&A: Meet Letitia Grenier, newest PPIC CalTrout Ecosystem Fellow

A research retrospective: offshore fault mapping of the San Andreas

In the early morning hours of April 18th, 1906, an alarming shake and rumble underfoot along the coastal areas of northern California gave way to a living nightmare of unprecedented devastation. At 5:12am, what would be considered one of the most devastating earthquake events in U.S. history wreaked unimaginable havoc on the burgeoning city of San Francisco.  This California earthquake ranks as one of the most well-known and impactful of all time. Today, its importance stems not only from the sheer magnitude of the quake (7.7-7.9), but also from the wealth of scientific knowledge derived from studying the event. Rupturing the northernmost 477 kilometers (296 miles) of the San Andreas fault from northwest of San Juan Bautista to the triple junction at Cape Mendocino, the earthquake confounded geologists with its large, horizontal movement and the massive length of the fault rupture. … ”  Read more at the USGS here:  A research retrospective: offshore fault mapping of the San Andreas

Measuring, monitoring, and modeling ecosystem cycling

The terrestrial biosphere—the regions of Earth’s land surface that support life—continuously exchanges carbon and water with the atmosphere. Plants capture atmospheric carbon dioxide (CO2) through valves in their leaves, converting the gas into compounds for growth through photosynthesis and respiration. Meanwhile, water moves from the ground through plant roots and stems to leaves, where it is gradually released, or transpired, back into the atmosphere.  Changing climate conditions may shift the balance of ecosystem carbon and water cycles by altering plant processes like photosynthesis, transpiration, and respiration. … ”  Read more from EOS here:  Measuring, monitoring, and modeling ecosystem cycling

Indigenous people vital for understanding environmental change

Grassroots knowledge from Indigenous people can help to map and monitor ecological changes and improve scientific studies, according to Rutgers-led research.  The study, published in the Journal of Applied Ecology, shows the importance of Indigenous and local knowledge for monitoring ecosystem changes and managing ecosystems. The team collected more than 300 indicators developed by Indigenous people to monitor ecosystem change, and most revealed negative trends, such as increased invasive species or changes in the health of wild animals. Such local knowledge influences decisions about where and how to hunt, benefits ecosystem management and is important for scientific monitoring at a global scale. … ”  Read more from Science Daily here:  Indigenous people vital for understanding environmental change

A surprising range of climate events may be predictable years in advance

An increase in the likelihood of a “Greenland Block” – a bulge of high pressure that stalls over the massive island and can cause extreme weather both in North America and Europe – could be predictable years in advance.  So too could changes in ocean acidity in the California Current System, which sustains rich and economically important fisheries, as well as fluxes in the amount of organic matter produced by phytoplankton in the ocean, which forms the base of the marine food pyramid.  Even probable increases or decreases in the amount of carbon dioxide taken up by plants, and the resulting impacts on the concentration of carbon dioxide in the atmosphere, may be predictable several years out. … ”  Read more from NCAR here: A surprising range of climate events may be predictable years in advance

Tiny plants crucial for sustaining dwindling water supplies: Global analysis

A global meta-analysis led by UNSW scientists shows tiny organisms that cover desert soils — so-called biocrusts — are critically important for supporting the world’s shrinking water supplies.  Biocrusts are a rich assortment of mosses, lichens, cyanobacteria, and microscopic organisms such as bacteria and fungi that live on the surface of dryland soils. Drylands, collectively, are the world’s largest biome.  “Biocrusts are critically important because they fix large amounts of nitrogen and carbon, stabilise surface soils, and provide a home for soil organisms,” said lead author Professor David Eldridge from UNSW Science. … ”  Read more from Science Daily here: Tiny plants crucial for sustaining dwindling water supplies: Global analysis

New smartphone game lets you solve real-world ecological puzzles

EcoBuilder, which is downloadable now on smartphones and tablets, teaches players how ecosystems work and aims to crowdsource solutions to unsolved ecological puzzles.  Ecosystem research looks at how animals and plants interact with each other and their environment. Climate change and other human interventions pose ongoing threats to how ecosystems function, resulting in changes to carbon flows and even extinctions of certain species. … ”  Read more from PhysOrg here:  New smartphone game lets you solve real-world ecological puzzles

New research papers …

Nutrient status of San Francisco Bay and its management implications

By:  James E. Cloern, Tara S. Schraga,Erica Nejad, & Charles Martin

Abstract: “Nutrient enrichment has degraded many of the world’s estuaries by amplifying algal production, leading to hypoxia/anoxia, loss of vascular plants and fish/shellfish habitat, and expansion of harmful blooms (HABs). Policies to protect coastal waters from the effects of nutrient enrichment require information to determine if a water body is impaired by nutrients and if regulatory actions are required. We compiled information to inform these decisions for San Francisco Bay (SFB), an urban estuary where the best path toward nutrient management is not yet clear. Our results show that SFB has high nutrient loadings, primarily from municipal wastewater; there is potential for high algal production, but that production is not fully realized; and SFB is not impaired by hypoxia or recurrent HABs. However, our assessment includes reasons for concern: nitrogen and phosphorus concentrations higher than those in other estuaries impaired by nutrient pollution, chronic presences of multiple algal toxins, a recent increase of primary production, and projected future hydroclimatic conditions that could increase the magnitude and frequency of algal blooms. Policymakers thus face the challenge of determining the appropriate protective policy for SFB. We identify three crucial next steps for meeting this challenge: (1) new research to determine if algal toxins can be reduced through nutrient management, (2) establish management goals as numeric targets, and (3) determine the magnitude of nutrient load reduction required to meet those targets. Our case study illustrates how scientific information can be acquired and communicated to inform policymakers about the status of nutrient pollution, its risks, and strategies for minimizing those risks.

Click here to access this paper.

Carbon sources in the sediments of a restoring vs. historically unaltered salt marsh

By: Judith Z. Drexler, Melanie J. Davis, Isa Woo, & Susan De La Cruz

Abstract: Salt marshes provide the important ecosystem service of carbon storage in their sediments; however, little is known about the sources of such carbon and whether they differ between historically unaltered and restoring systems. In this study, stable isotope analysis was used to quantify carbon sources in a restoring, sparsely vegetated marsh (Restoring) and an adjacent, historically unaltered marsh (Reference) in the Nisqually River Delta (NRD) of Washington, USA. Three sediment cores were collected at “Inland” and “Seaward” locations at both marshes ~ 6 years after restoration. Benthic diatoms, C3 plants, C4 plants, and particulate organic matter (POM) were collected throughout the NRD. δ13C and δ15N values of sources and sediments were used in a Bayesian stable isotope mixing model to determine the contribution of each carbon source to the sediments of both marshes. Autochthonous marsh C3 plants contributed 73 ± 10% (98 g C m−2 year−1) and 89 ± 11% (119 g C m−2 year−1) to Reference-Inland and Reference-Seaward sediment carbon sinks, respectively. In contrast, the sediment carbon sink at the Restoring Marsh received a broad assortment of predominantly allochthonous materials, which varied in relative contribution based on source distance and abundance. Marsh POM contributed the most to Restoring-Seaward (42 ± 34%) (69 g C m−2 year−1) followed by Riverine POM at Restoring-Inland (32 ± 41%) (52 g C m−2 year−1). Overall, this study demonstrates that largely unvegetated, restoring marshes can accumulate carbon by relying predominantly on allochthonous material, which comes mainly from the most abundant and closest estuarine sources.

Click here to access this paper.

Tracking California’s sinking coast from space: Implications for relative sea-level rise

By: Em Blackwell, Manoochehr Shirzaei, Chandrakanta Ojha, and Susanna Werth

Abstract: Coastal vertical land motion affects projections of sea-level rise, and subsidence exacerbates flooding hazards. Along the ~1350-km California coastline, records of high-resolution vertical land motion rates are scarce due to sparse instrumentation, and hazards to coastal communities are underestimated. Here, we considered a ~100-km-wide swath of land along California’s coast and performed a multitemporal interferometric synthetic aperture radar (InSAR) analysis of large datasets, obtaining estimates of vertical land motion rates for California’s entire coast at ~100-m dimensions—a ~1000-fold resolution improvement to the previous record. We estimate between 4.3 million and 8.7 million people in California’s coastal communities, including 460,000 to 805,000 in San Francisco, 8000 to 2,300,00 in Los Angeles, and 2,000,000 to 2,300,000 in San Diego, are exposed to subsidence. The unprecedented detail and submillimeter accuracy resolved in our vertical land motion dataset can transform the analysis of natural and anthropogenic changes in relative sea-level and associated hazards.

Click here to access the paper.

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About Science News and Reports: This weekly feature, posted every Thursday, is a collection of the latest scientific research and reports with a focus on relevant issues to the Delta and to California water, although other issues such as climate change are sometimes included. Do you have an item to be included here? Submissions of relevant research and other materials is welcome. Email Maven

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