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Harmful cyanobacteria blooms are a growing threat in estuarine waters as upstream blooms are exported into coastal environments. Cyanobacteria can produce potent toxins, one of which-hepatotoxic microcystins (MCs)-can persist and accumulate within the food web. Filter-feeding invertebrates may biomagnify toxins up to 100× ambient concentrations. As such, bivalves can be used as an environmentally relevant and highly sensitive sentinel for MC monitoring. To date there has been little research on cyanotoxin bioaccumulation in estuaries. The Sacramento-San Joaquin Delta (Delta) aquatic food web has undergone a profound change in response to widespread colonization of aquatic invasive species such as Asian clams (Corbicula fluminea) in the freshwater portion of the Delta. These clams are prolific-blanketing areas of the Delta at densities up to 1000 clams/m 2 and are directly implicated in the pelagic organism decline of threatened and endangered fishes. We hypothesized that Asian clams accumulate MCs which may act as an additional stressor to the food web and MCs would seasonally be in exceedance of public health advisory levels. MCs accumulation in Delta Asian clams and signal crayfish (Pacifastacus leniusculus) were studied over a two-year period. ELISA and LC-MS analytical methods were used to measure free and protein-bound MCs in clam and crayfish tissues. We describe an improved MC extraction method for use when analyzing these taxa by LC-MS. MCs were found to accumulate in Asian clams across all months and at all study sites, with seasonal maxima occurring during the summer. Although MC concentrations rarely exceeded public health advisory levels, the persistence of MCs year-round still poses a chronic risk to consumers. Crayfish at times also accumulated high concentrations of MCs. Our results highlight the utility of shellfish as sentinel organisms for monitoring in estuarine areas., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Ellen Preece reports financial support was provided by Delta Water Quality and Ecosystem Restoration Grant Program. Timothy Otten reports financial support was provided by Delta Water Quality and Ecosystem Restoration Grant Program. Raphael Kudela reports financial support was provided by Delta Water Quality and Ecosystem Restoration Grant Program. Raphael Kudela reports a relationship with San Francisco Estuary Institute that includes: funding grants. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Cyanobacteria harmful algal blooms (CHABs) are a growing water quality problem in the upper San Francisco Estuary (California), also known as the Sacramento-San Joaquin Delta. We conducted cyanobacteria and cyanotoxin monitoring from 2020 to 2023, which spanned California's driest consecutive 3-year period and one of the wettest years on record (2023). To assess the impact of CHABs over this range of hydrologic conditions, we monitored invasive Asian Clams (Corbicula fluminea) for microcystin contamination and used molecular tools (qPCR and sequencing) to characterize cyanobacteria in the water column. We also used solid phase adsorption toxin tracking (SPATT) samplers to track microcystins (MCs) and other cyanotoxins in 2023. During the drought years, record breaking MCs, in excess of 1000 μg/L, were documented in water grab samples and Asian clams also accumulated higher MCs relative to the wet year. However, MCs were present in Asian clams during the entire study period. SPATT's confirmed MC presence during wet 2023 and sequencing results corroborated the integrative sampler findings. Yet, no MC was detected in water grab samples at our primary sampling sites during the drought year of 2022 or the wet year of 2023. This highlights the importance of using multiple sampling modalities to provide a more accurate assessment of MC contamination, especially in large estuaries where traditional discrete monitoring can easily miss episodic and transient CHAB events., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Ellen Preece reports financial support was provided by Delta Water Quality and Ecosystem Restoration Grant Program implemented by the State of California Department of Fish and Wildlife. Timothy Otten reports financial support was provided by Delta Water Quality and Ecosystem Restoration Grant Program implemented by the State of California Department of Fish and Wildlife. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Cyanobacterial harmful algal blooms (CHABs) have become a persistent seasonal problem in the upper San Francisco Estuary, California also known as the Sacramento-San Joaquin Delta (Delta). The Delta is comprised of a complex network of open water bodies, channels, and sloughs. The terminus of the Stockton Channel is an area identified as a CHAB "hotspot." As CHABs increase in severity, there is an urgent need to better understand CHAB drivers to identify and implement mitigation measures that can be used in an estuarine complex like the Delta. We investigated water quality conditions and nutrient dynamics in the Stockton Channel by measuring nutrients in the water column, sediments, and pore waters. In situ nutrient addition bioassay experiments were used to assess the effects of nutrient enrichment on total algal/cyanobacterial growth and pigment concentrations. In both June and September, relative to unamended controls, total chlorophyll and cyanobacterial pigment concentrations were unaffected by nutrient additions; hence, the study area showed signs of classical hypereutrophication, with ambient nitrogen and phosphorus present in excess of algal growth requirements. A cyanobacterial bloom, dominated by Microcystis spp. was present throughout the study area but was most severe and persistent at the shallowest site at the channel terminus. At this site, Microcystis spp. created water quality conditions that allowed for a prolonged bloom from June through September. While targeted nutrient reductions are recommended for long term mitigation, on a shorter timescale, our findings suggest that physical/mechanical controls are the more promising alternative approaches to reduce the severity of CHABs in the terminus of the Stockton Channel., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:Ellen Preece reports financial support, article publishing charges, statistical analysis, and writing assistance were provided by City of Stockton, Port of Stockton, California State Water Resources Control Board, Central Valley Regional Water Quality Control Board. Hans Paerl reports financial support, administrative support, equipment, drugs, or supplies, statistical analysis, travel, and writing assistance were provided by Delta Science Program, National Science Foundation, National Institute of Health., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Similar to many large river valleys globally, the Sacramento River Valley has been extensively drained and leveed, hydrologically divorcing river channels from most floodplains. Today, the former floodplain is extensively managed for agriculture. Lack of access to inundated floodplains is recognized as a significant contributing factor in the decline of native Chinook Salmon (Oncorhynchus tshawytscha). We observed differences in salmon growth rate, invertebrate density, and carbon source in food webs from three aquatic habitat types-leveed river channels, perennial drainage canals in the floodplain, and agricultural floodplain wetlands. Over 23 days (17 February to 11 March, 2016) food web structure and juvenile Chinook Salmon growth rates were studied within the three aquatic habitat types. Zooplankton densities on the floodplain wetland were 53x more abundant, on average, than in the river. Juvenile Chinook Salmon raised on the floodplain wetland grew at 0.92 mm/day, 5x faster than fish raised in the adjacent river habitat (0.18 mm/day). Two aquatic-ecosystem modeling methods were used to partition the sources of carbon (detrital or photosynthetic) within the different habitats. Both modeling approaches found that carbon in the floodplain wetland food web was sourced primarily from detrital sources through heterotrophic pathways, while carbon in the river was primarily photosynthetic and sourced from in situ autotrophic production. Hydrologic conditions typifying the ephemerally inundated floodplain-shallower depths, warmer water, longer water residence times and predominantly detrital carbon sources compared to deeper, colder, swifter water and a predominantly algal-based carbon source in the adjacent river channel-appear to facilitate the dramatically higher rates of food web production observed in the floodplain. These results suggest that hydrologic patterns associated with seasonal flooding facilitate river food webs to access floodplain carbon sources that contribute to highly productive heterotrophic energy pathways important to the production of fisheries resources., Competing Interests: The authors have declared that no competing interests exist.

Children residing in mining towns are potentially disproportionately exposed to metal(loid)s via ingestion and dust inhalation, thus, increasing their exposure when engaging in school or home gardening or playing outside. This citizen science study assessed preschool children's potential arsenic (As), cadmium (Cd), and lead (Pb) exposure via locally grown produce, water, incidental soil ingestion, and dust inhalation at four sites. Participants were trained to properly collect water, soil, and vegetable samples from their preschools in Nevada County, California. As, Cd, and Pb concentrations in irrigation sources did not exceed the U.S. EPA's maximum contaminant and action levels. In general, garden and playground As and Pb soil concentrations exceeded the U.S. EPA Regional Screening Level, CalEPA Human Health Screening Level, and California Department of Toxic Substances Control Screening Level. In contrast, all Cd concentrations were below these recommended screening levels. Dust samples (<10 μm diameter) were generated from surface garden and playground soil collected at the preschools by a technique that simulated windblown dust. Soil and dust samples were then analyzed by in-vitro bioaccessibility assays using synthetic lung and gastric fluids to estimate the bioaccessible fraction of As, Cd, and Pb in the body. Metal(loid) exposure via grown produce revealed that lettuce, carrot, and cabbage grown in the preschool gardens accumulated a higher concentration of metal(loid) than those store-bought nation-wide. None of the vegetables exceeded the respective recommendation maximum levels for Cd and Pb set by the World Health Organization Codex Alimentarius Commission. The results of this study indicate that consumption of preschool-grown produce and incidental soil ingestion were major contributors to preschool-aged children's exposure to As, Cd, and Pb. Traditionally, this level of site- and age-specific assessment and analyses does not occur at contaminated sites. The results of this holistic risk assessment can inform future risk assessment and public health interventions related to childhood metal(loid) exposures., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Blooms of the cyanobacterium Microcystis spp. could affect fish health through the ingestion of colonies as well as exposure to dissolved microcystins in the water column. The goal of the present study was to evaluate the dietary exposure pathway through which Microcystis spp. blooms may affect liver function and nutritional status using a novel approach involving multiple analytical methods to assess the potential risk. Our study was conducted using threadfin shad, Dorosoma petenense, which is a pelagic fish commonly exposed to Microcystis spp. blooms in the upper San Francisco Estuary. The approach incorporated published and optimized methods that offer multiple lines of evidence including in situ hybridization, immunohistochemistry, histopathology, condition factor indices, and nutritional profiles. Measurements of threadfin shad health and tissue condition were conducted at sites where Microcystis was present or absent during the 2007 bloom season. The results showed that dietary exposure to fish from Microcystis blooms resulted in the accumulation of microcystin in the gut and liver tissues of threadfin shad collected from the sites with blooms. Although toxicity endpoints were likely confounded by antecedent conditions, our findings demonstrate dietary exposure of Microcystis toxins to fish using a novel approach with multiple lines of evidence. Environ Toxicol Chem 2020;39:787-798. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC., (© 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.)

Temperature and sea level are predicted to rise with climate change, bringing an urgency to evaluating future viability of native fish. Lamprey are confronted with widespread habitat degradation, migratory barriers, and episodes of environmental change projected to be commonplace in the future. In California, range contraction likely shifted lamprey rearing downstream, but the extent and physiological constraints that restrict estuarine rearing are unclear. We used a single-season occupancy model to describe juvenile lamprey estuarine distribution and found occupancy was regionally variable and constrained by temperature. Habitat and hydrology providing thermal refugia may be critical for future persistence., (© 2019 The Authors. Journal of Fish Biology published by John Wiley & Sons Ltd on behalf of The Fisheries Society of the British Isles.)

The herbicides glyphosate, imazamox and fluridone are herbicides, with low toxicity towards fish and invertebrates, which are applied to waterways to control invasive aquatic weeds. However, the effects of these herbicides on natural isolates of phytoplankton and cyanobacteria are unknown. Three species of microalgae found in the San Francisco Estuary (SFE)/Sacramento-San Joaquin River Delta (Delta) ( Microcystis aeruginosa , Chlamydomonas debaryana , and Thalassiosira pseudonana ) were exposed to the three herbicides at a range of concentrations in 96-well plates for 5-8 days. All three algal species were the most sensitive to fluridone, with IC 50 of 46.9, 21, and 109 µg L -1 for M. aeruginosa , T. pseudonana and C. debaryana, respectively. Imazamox inhibited M. aeruginosa and T. pseudonana growth at 3.6 × 10 4  µg L -1 or higher, and inhibited C. debaryana growth at 1.0 × 10 5  µg L -1 or higher. Glyphosate inhibited growth in all species at ca. 7.0 × 10 4  µg L -1 or higher. Fluridone was the only herbicide that inhibited the microalgae at environmentally relevant concentrations in this study and susceptibility to the herbicide depended on the species. Thus, the application of fluridone may affect cyanobacteria and phytoplankton community composition in water bodies where it is applied.

Rationale: Oxygen isotope ratios (δ 18 O values) of fish otoliths (ear bones) are valuable geochemical tracers of water conditions and thermal life history. Delta Smelt (Hypomesus transpacificus) are osmerid forage fish endemic to the San Francisco Estuary, California, USA, that are on the verge of extinction. These fish exhibit a complex life history that allows them to survive in a dynamic estuarine environment; however, a rapidly warming climate threatens this thermally sensitive species. Here we quantify the accuracy and precision of using δ 18 O values in otoliths to reconstruct the thermal life histories of Delta Smelt., Methods: Delta Smelt were reared for 360 days using three different water sources with different ambient δ 18 O water values (-8.75‰, -5.28‰, and -4.06‰) and different water temperatures (16.4°C, 16.7°C, 18.7°C, and 20.5°C). Samples were collected after 170 days (n = 28) and 360 days (n = 14) post-hatch. In situ δ 18 O values were measured from the core of the otolith to the dorsal edge using secondary ion mass spectrometry (SIMS) to reconstruct temporally resolved thermal life histories., Results: The δ 18 O otolith values for Delta Smelt varied as a linear inverse function of water temperature: 1000 ln α = 18.39 (±0.43, 1SE)(10 3 TK -1 ) - 34.56 (±1.49, 1SE) and δ 18 O otolith(VPDB)  - δ 18 O water (VPDB)  = 31.34(±0.09, 1SE) - 0.19(±0.01, 1SE) × T ° C. When the ambient δ 18 O water value is known, this species-specific temperature-dependent oxygen isotope fractionation model facilitated the accurate (0.25°C) and precise (±0.37°C, 2σ) reconstruction of the water temperature experienced by the fish. In contrast, the use of existing general fractionation equations resulted in inaccurate temperature reconstructions., Conclusions: The species-specific δ 18 O otolith fractionation equation allowed for accurate and precise reconstructions of water temperatures experienced by Delta Smelt. Characterization of ambient δ 18 O water values remains a critical next step for reconstructing thermal life histories of wild Delta Smelt. This tool will provide new insights into habitat utilization, potential thermal refugia, and resilience to future warming for this critically endangered fish., (© 2019 John Wiley & Sons, Ltd.)

Recycling water from municipal wastewater offers a reliable and sustainable solution to cities and regions facing shortage of water supply. Places including California and Singapore have developed advanced water reuse programs as an integral part of their water management strategy. Membrane technology, particularly reverse osmosis, has been playing a key role in producing high quality recycled water. This feature paper highlights the current status and future perspectives of advanced membrane processes to meet potable water reuse. Recent advances in membrane materials and process configurations are presented and opportunities and challenges are identified in the context of water reuse.