Exploring scientific and management implications of upper trophic level food webs in the Delta

Delta Stewardship Council (Delta Council) | April 17th, 2024

The Sacramento-San Joaquin Delta (the Delta) has complex and evolving ecosystems characterized by multiple food webs that vary in time and space. Here, food webs are defi

The Sacramento-San Joaquin Delta (the Delta) has complex and evolving ecosystems characterized by multiple food webs that vary in time and space. Here, food webs are defined as the network of species interactions (competition, predation) and interactions with their environment that are related through the flow of energy through the ecosystem (e.g., Paine 1980). Physical modifications, in addition to the introduction of non-native species and the changing climate, have significantly altered the structure and energetic pathways of the food webs for decades. The science clearly suggests that predicting the impacts of habitat restoration, fisheries, changes in environmental drivers (e.g., climate, changes in nutrient loading, invasive species) on the ecological carrying capacity and productivity of the Delta, as well as the bioaccumulation of contaminants on species or the ecosystem, requires an understanding of food web processes.

Exposure history determines pteropod vulnerability to ocean acidification along the US West Coast

Nature Portfolio (Springer Nature) | July 3rd, 2017

The pteropod Limacina helicina frequently experiences seasonal exposure to corrosive conditions (Ωar  < 1) along the US West Coast and is recognized as

The pteropod Limacina helicina frequently experiences seasonal exposure to corrosive conditions (Ωar  < 1) along the US West Coast and is recognized as one of the species most susceptible to ocean acidification (OA). Yet, little is known about their capacity to acclimatize to such conditions. We collected pteropods in the California Current Ecosystem (CCE) that differed in the severity of exposure to Ωar conditions in the natural environment. Combining field observations, high-CO2 perturbation experiment results, and retrospective ocean transport simulations, we investigated biological responses based on histories of magnitude and duration of exposure to Ωar < 1. Our results suggest that both exposure magnitude and duration affect pteropod responses in the natural environment. However, observed declines in calcification performance and survival probability under high CO2 experimental conditions do not show acclimatization capacity or physiological tolerance related to history of exposure to corrosive conditions. Pteropods from the coastal CCE appear to be at or near the limit of their physiological capacity, and consequently, are already at extinction risk under projected acceleration of OA over the next 30 years. Our results demonstrate that Ωar exposure history largely determines pteropod response to experimental conditions and is essential to the interpretation of biological observations and experimental results.

Extreme and compound events in lakes

Nature Portfolio (Springer Nature) | August 19th, 2025

Key points Lake heatwaves have increased in average intensity, average duration and total duration globally, at rates of 0.15 ± 0.3 °C per decade, 2.1 

Key points Lake heatwaves have increased in average intensity, average duration and total duration globally, at rates of 0.15 ± 0.3 °C per decade, 2.1 ± 3.1 days per decade and 8.8 ± 7.6 days per decade, respectively, since the 1980s. The probability of lake heatwave events is three times more likely in a 1.5 °C warming scenario and 25 times more likely in a 3.5 °C scenario compared with pre-industrial conditions. Half of the world’s largest lakes experienced declines in water storage between 1992 and 2020, accompanied by corresponding reductions in surface extent. Extreme events in lakes can cause considerable impacts, including the onset of hypoxia, harmful algal blooms, disruption of food webs and loss of ecosystem services. Basin-scale anthropogenic stressors, such as nutrient enrichment, land-use change and water withdrawal, interact with climate extremes to increase the frequency, intensity and ecological consequences of in-lake extremes.

Extremophile hotspots linked to containerized industrial waste dumping in a deep-sea basin

Oxford University Press (OUP) | September 9th, 2025

Decaying barrels on the seafloor linked to DDT contamination have raised concerns about the public health implications of decades old industrial waste dumped off the coas

Decaying barrels on the seafloor linked to DDT contamination have raised concerns about the public health implications of decades old industrial waste dumped off the coast of Los Angeles. To explore their contents, we collected sediment cores perpendicular to five deepsea barrels. The concentration of DDT and its breakdown products were highly elevated relative to control sites yet did not vary with distance from the barrels, suggesting that they were not associated with the contamination. Sediment cores collected through white halos surrounding three barrels were enriched in calcite and had elevated pH. The associated microbial communities were low diversity and dominated by alkalophilic bacteria with metagenome-assembled genomes adapted to high pH. A solid concretion sampled between a white halo and barrel was composed of brucite, a magnesium hydroxide mineral that forms at high pH. Based on these findings, we postulate that leakage of containerized alkaline waste triggered the formation of mineral concretions that are slowly dissolving and raising the pH of the surrounding sediment pore water. This selects for taxa adapted to extreme alkalinity and drives the precipitation of “anthropogenic” carbonates forming white halos, which serve as a visual identifier of barrels that contained alkaline waste. Remarkably, containerized alkaline waste discarded >50 years ago represents a persistent pollutant creating localized mineral formations and microbial communities that resemble those observed at some hydrothermal systems. These formations were observed at one-third of the visually identified barrels in the San Pedro Basin and have unforeseen, long-term consequences for benthic communities in the region.

Facilitating Adaptive Management in California’s Sacramento–San Joaquin Delta

University of California, Davis (UC Davis) | July 1st, 2017

Uncertainties in understanding ecosystems increase the risk that management will fail to achieve desired results. Adaptive management is a structured, iterative applicati

Uncertainties in understanding ecosystems increase the risk that management will fail to achieve desired results. Adaptive management is a structured, iterative application of science-based knowledge to reduce uncertainties and build flexibility into decision-making. However, adaptive management is more easily planned than implemented, and it is only beginning to be applied in the California’s Sacramento–San Joaquin Delta. We draw from two assessments of adaptive management in the Delta and examples of its use elsewhere to suggest how the process can be facilitated. Although a highly structured adaptive-management process may not always be needed, several elements are essential. Adaptive management should begin by clearly identifying the problem, goals, and objectives; recognizing uncertainties; identifying decision points and alternative approaches; recognizing when adjustments are needed and having the flexibility to make them; and considering societal and political constraints. Model complexity should be matched to that of the system and management needs; experiments can help unravel causal relationships. Monitoring, analyses, and syntheses require comprehensive data-management systems. More frequent and organized communications among scientists, managers, stakeholders, and decision-makers are necessary. We propose the establishment of an “Adaptive Management Team” to coordinate efforts across the management spectrum of the Delta and to provide guidance and link individual projects to shared approaches and experiences. Reliable long-term support will be needed to assess results of management actions, adjust approaches where improvement is likely, and strive toward the legislated goals of enhancing the Delta ecosystem while also providing reliable water supplies to much of California, and doing both these things in a manner that protects values of the Delta as a place where people live and work. 

Faster, bigger, more severe: Extreme wildfire spread sets the stage for forest ecosystem change in western and boreal North America

American Association for the Advancement of Science (AAAS) | August 12th, 2026

A relatively small number of rapidly spreading wildfire events burn disproportionately large areas. But beyond area burned, do fast fires produce distinct postfire ecolog

A relatively small number of rapidly spreading wildfire events burn disproportionately large areas. But beyond area burned, do fast fires produce distinct postfire ecological outcomes? Here, we measure daily linear fire growth rates and assess relationships between fire spread, burn severity, and metrics of postfire landscape resilience from 3499 fires occurring between 2012 and 2023 in conifer-dominated forests of Canada and the western US. We find that as linear spread rate increases, so too does fire severity, proportion of area burned at high severity, and distance to surviving live tree seed sources. Thus, not only do the fastest fires burn outsized areas, but these areas have less remaining tree cover and reduced capacity for recovery, setting the stage for long-term vegetation shifts. Given anticipated increases in extreme fire spread as fire seasons lengthen and weather becomes more fire-conducive, our findings highlight growing needs to effectively reduce undesired impacts, manage postfire landscapes to sustain forest ecosystem functions, and foster social-ecological adaptation.

Feather River Salmonid Habitat Improvement Project Proposed Mitigated Negative Declaration

California Department of Water Resources (DWR) | October 6th, 2022

An initial study/proposed mitigated negative declaration (IS/MND) has been prepared to assess the proposed project’s potential effects on the physical environment and t

An initial study/proposed mitigated negative declaration (IS/MND) has been prepared to assess the proposed project’s potential effects on the physical environment and the significance of those effects. Based on the analysis conducted in the IS, DWR has determined that the proposed project would not have any significant adverse effects on the environment because environmental commitments and mitigation measures would be implemented to reduce impacts to a less-than-significant level.

Field Assessment of Naled and Its Primary Degradation Product (Dichlorvos) in Aquatic Ecosystems Following Aerial Ultra-low Volume Application for Mosquito Control

Archives of Environmental Contamination and Toxicology (Springer) | March 13th, 2023

Naled, an organophosphate insecticide, is applied aerially at ultra-low volumes over aquatic ecosystems near Sacramento, California, USA, during summer months for mosqui

Naled, an organophosphate insecticide, is applied aerially at ultra-low volumes over aquatic ecosystems near Sacramento, California, USA, during summer months for mosquito control. Two ecosystem types (rice fields and a flowing canal) were sampled in 2020 and 2021. Naled and its primary degradation product (dichlorvos) were measured in water, biofilm, grazer macroinvertebrates, and omnivore/predator macroinvertebrates (predominantly crayfish). Maximum naled and dichlorvos concentrations detected in water samples one day after naled application were 287.3 and 5647.5 ng/L, respectively, which were above the U.S. Environmental Protection Agency’s aquatic life benchmarks for invertebrates. Neither compound was detected in water more than one day after the application. Dichlorvos, but not naled, was detected in composite crayfish samples up to 10 days after the last aerial application. Detections in water from the canal showed that the compounds were transported downstream of the target application area. Factors such as vector control flight paths, dilution, and transport through air and water likely affected concentrations of naled and dichlorvos in water and organisms from these aquatic ecosystems.

Fill Mead First: A Technical Assessement

Utah State University | October 11th, 2016

The Fill Mead First (FMF) plan would establish Lake Mead reservoir as the primary water storage facility of the main-stem Colorado River and would relegate Lake Powell re

The Fill Mead First (FMF) plan would establish Lake Mead reservoir as the primary water storage facility of the main-stem Colorado River and would relegate Lake Powell reservoir to a secondary water storage facility to be used only when Lake Mead is full. The objectives of the FMF plan are to re-expose some of Glen Canyon’s sandstone walls that are now inundated, begin the process of re-creating a riverine ecosystem in Glen Canyon, restore a more natural stream-flow, temperature, and sediment-supply regime of the Colorado River in the Grand Canyon ecosystem, and reduce system-wide water losses caused by evaporation and movement of reservoir water into ground-water storage. 

Final Environmental Assessment Sacramento River Winter-Run Chinook Salmon Management Measures for Fisheries Managed under the Pacific Coast Salmon Fishery Management Plan

National Marine Fisheries Service (NMFS) | March 1st, 2018