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Cyanobacterial harmful algal blooms (cyanoHABs) can harm people, animals, and affect consumptive and recreational use of inland waters. Monitoring cyanoHABs is often limited. However, chlorophyll‐a (chl‐a) is a common water quality metric and has been shown to have a relationship with cyanobacteria. The World Health Organization (WHO) recently updated their previous 1999 cyanoHAB guidance values (GVs) to be more practical by basing the GVs on chl‐a concentration rather than cyanobacterial counts. This creates an opportunity for widespread cyanoHAB monitoring based on chl‐a proxies, with satellite remote sensing (SRS) being a potentially powerful tool. We used Sentinel‐2 (S2) and Sentinel‐3 (S3) to map chl‐a and cyanobacteria, respectively, classified chl‐a values according to WHO GVs, and then compared them to cyanotoxin advisories issued by the California Department of Water Resources (DWR) at San Luis Reservoir, key infrastructure in California's water system. We found reasonably high rates of total agreement between advisories by DWR and SRS, however rates of agreement varied for S2 based on algorithm. Total agreement was 83% for S3, and 52%–79% for S2. False positive and false negative rates for S3 were 12% and 23%, respectively. S2 had 12%–80% false positive rate and 0%–38% false negative rate, depending on algorithm. Using SRS‐based chl‐a GVs as an early indicator for possible exposure advisories and as a trigger for in situ sampling may be effective to improve public health warnings. Implementing SRS for cyanoHAB monitoring could fill temporal data gaps and provide greater spatial information not available from in situ measurements alone. Plain Language Summary: Lakes often have algal blooms that create a water quality concern, especially when they contain cyanobacteria, which can be toxic to both humans and animals. These harmful algal blooms are of great concern in areas with limited water supply in states such as California. While it is often difficult and costly to collect and monitor toxin concentrations, monitoring concentrations of chlorophyll‐a (chl‐a) –a measure of how much algae are present—is relatively common and can even be accomplished using satellite remote sensing. There have been multiple studies that have found a relationship between toxins produced by cyanobacteria and chl‐a. The World Health Organization (WHO) has recently released (2021) an updated release of their previous 1999 guidance values for toxin monitoring based on chl‐a concentration. With satellite data, we were able to measure chl‐a concentration in a major reservoir in California, and then classify the chl‐a measurements into the WHO's guidance values for toxins. We compared the satellite‐based guidance values to the public advisory levels currently set by the California Department of Water Resources. Our results indicate that SRS of chl‐a is a reasonable substitute for cyanobacteria toxin advisories, and our framework can be applied to similar cyanobacteria dominated lakes. Key Points: The World Health Organization (WHO) updated cyanobacteria harmful algal blooms (cyanoHABs) guidelines for chlorophyll‐a (chl‐a) as a proxyWith satellite remote sensing (SRS), we estimated and classified chl‐a to compare cyanotoxins advisories used by CaliforniaThis study provides a framework for evaluating public health utility of SRS for enhancing cyanotoxin monitoring globally [ABSTRACT FROM AUTHOR]

As temperatures rise, it is increasingly important to monitor changes in habitat conditions for aquatic species and mitigate emerging stressors. The ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) instrument provides temperature products at a spatial and temporal scale not previously available. Here, we utilize ECOSTRESS temperature products to assess fluctuations in thermal habitat suitability for an endangered fish species and we also demonstrate the utility of the data set to assess water surface and bulk temperature changes following completion of two tidal wetland restoration efforts in the San Francisco Estuary and Sacramento–San Joaquin River Delta (Bay Delta). During all hours of the day throughout the 2018–2022 study period, key Delta Smelt habitat areas including Honker Bay, West Suisun Bay, and Mid Suisun Bay had greater than 75% of their areas suitable; there were several instances during which less than 25% of the area was thermally suitable generally coinciding with heatwave events. Overall, midday hours are less frequently suitable than morning and evening hours. Early evidence from ECOSTRESS indicates that there may be a decrease in surface water temperature of up to several degrees in tidal restoration areas, but more data is needed to show statistically significant outcomes. The ECOSTRESS record began in summer of 2018, and a longer record is needed to fully capture temperature changes associated with wetland processes and restoration efforts. Future applications of ECOSTRESS products can the capacity to help further understand ecosystem conditions and how restoration efforts affect water temperature, informing decisions that benefit Delta Smelt and other at‐risk aquatic species. Plain Language Summary: Water temperatures are rising in the San Francisco Estuary and Sacramento–San Joaquin River Delta (Bay Delta), negatively affecting endangered fish survivability. An instrument aboard the International Space Station called the ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) can give vital information about Bay Delta water temperatures at a broader scale than field measurements with reasonable spatial resolution and on a more frequent basis than previously available to understand where habitat management efforts would be most useful and even assess the impacts of previous restoration efforts on temperature. Here, we look at how favorable the Bay Delta water temperatures are for endangered Delta Smelt and assess the effects of two completed restoration efforts on water temperature (The Tule Red and Winter Island tidal wetland restoration projects). As managers and decision makers continue to evaluate actions toward protecting endangered aquatic species, ECOSTRESS can provide information to support the decision making process. Key Points: Aquatic thermal habitat conditions vary diurnally and spatiallyMidday periods and inland regions have unsuitable habitat for the Delta Smelt most frequentlyECOsystem Spaceborne Thermal Radiometer Experiment on Space Station shows early evidence of surface water temperature cooling benefits from tidal wetland restoration projects of up to 5.4°C [ABSTRACT FROM AUTHOR]

Estuaries worldwide are experiencing stress due to increased droughts, which often prompt intervention by environmental managers and government agencies. Effective management of water resources in estuarine systems can be enhanced by new technologies and methodologies to support decision-making processes. Here, we evaluate the use of high-frequency, high-resolution satellite remote sensing within two managementrelevant case studies in the San Francisco Estuary and the Sacramento--San Joaquin River Delta. We used a remote sensing-derived time series of turbidity maps to (1) identify favorable turbidity conditions for the endangered fish species, delta smelt (Hypomesus transpacificus), during the height of the great California drought in the dry season of 2015, and (2) evaluate changes in turbidity following the installation of an emergency saltwater intrusion barrier. The mapping results indicate several persistent areas of turbidity refugia throughout the summer in the north and west Delta; however, there was infrequent connectivity. A comparison of images captured during ebb tides before and after barrier installation showed a mean increase of 6.6 Nephelometric Turbidity Units (NTU) in the San Joaquin River and 4 NTU in Fisherman's Cut. Our assessment of the barrier supports previous findings, which used field samples to conclude barrier installation may have resulted in increased turbidity near the barrier and enhances these findings by providing spatial context. [ABSTRACT FROM AUTHOR]

This study utilizes satellite data to investigate water quality conditions in the San Francisco Estuary and its upstream delta, the Sacramento--San Joaquin River Delta. To do this, this study derives turbidity from the European Space Agency satellite Sentinel-2 acquired from September 2015 to June 2019 and conducts a rigorous validation with in situ measurements of turbidity from optical sensors at continuous monitoring stations. This validation includes 965 matchup comparisons between satellite and in situ sensor data across 22 stations, yielding R² = 0.63 and 0.75 for Nephelometric Turbidity Unit and Formazin Nephelometric Unit (FNU) stations, respectively. This study then applies remote sensing to evaluate patterns in turbidity during the Suisun Marsh Salinity Control Gates Action ("Gates action"), a pilot study designed to increase habitat access and quality for the endangered Delta Smelt. The basic strategy was to direct more freshwater into Suisun Marsh, creating more low salinity habitat that would then have higher (and more suitable) turbidity than upstream river channels. For all seven acquisitions considered from June 29 to September 27, 2018, turbidity conditions in Bays and Sloughs subregions were consistently higher (and more suitable) (26-47 FNU) than what was observed in the upstream River region (13-25 FNU). This overall pattern was observed when comparing images acquired during similar tidal stages and heights. [ABSTRACT FROM AUTHOR]

Arctic wetlands store nearly half of the world's soil organic carbon and are crucial to the global carbon cycle. However, most Earth system models fail to account for wetlands given heterogeneity and uncertainty surrounding the response of different wetland types to climate change.We analyzed summer (June-August) carbon dioxide (CO2) exchange, meteorological conditions, and ecological conditions at four Arctic wetlands. Micrometeorological flux tower data were used to assess CO2 exchange and meteorological conditions across 7 to 9 years of data. Climate data were used to assess meteorological conditions across 30 years of data. Satellite data described ecological conditions. Each site acted as a CO2 sink, but strength varied, ranging from -49 to -93 g C/m² per summer. A trend analysis was used to investigate how CO2 balance and surrounding conditions may have changed. CO2 exchange significantly changed at one site, becoming a stronger sink. Changes in meteorological conditions were variable across sites with the exception of air temperature which, when considering significant trends, unanimously increased across sites. Ecological conditions suggested increased vegetation cover regardless of statistical significance at all sites. A conditional random forest algorithm was used to evaluate drivers of CO2 exchange. Cumulative precipitation and evapotranspiration were the main drivers of net ecosystem exchange and gross primary productivity, while ecosystem respiration was primarily driven by air temperature, suggesting that projected changes in temperature and precipitation patterns will influence the carbon balance of Arctic wetlands. Variability across sites emphasizes the need for long-term observations across wetland types and climatic gradients. [ABSTRACT FROM AUTHOR]

Processes of spread and patterns of persistence of invasive species affect species and communities in the new environment. Predicting future rates of spread is of great interest for timely management decisions, but this depends on models that rely on understanding the processes of invasion and historic observations of spread and persistence. Unfortunately, the rates of spread and patterns of persistence are difficult to model or directly observe, especially when multiple rates of spread and diverse persistence patterns may be co-occurring over the geographic distribution of the invaded ecosystem. Remote sensing systematically acquires data over large areas at fine spatial and spectral resolutions over multiple time periods that can be used to quantify spread processes and persistence patterns. We used airborne imaging spectroscopy data acquired once a year for 5 years from 2004 to 2008 to map an invaded submerged aquatic vegetation ( SAV) community across 2220 km2 of waterways in the Sacramento-San Joaquin River Delta, California, USA, and measured its spread rate and its persistence. Submerged aquatic vegetation covered 13-23 km2 of the waterways (6-11%) every year. Yearly new growth accounted for 40-60% of the SAV area, ~50% of which survived to following year. Spread rates were overall negative and persistence decreased with time. From this dataset, we were able to identify both radial and saltatorial spread of the invaded SAV in the entire extent of the Delta over time. With both decreasing spread rate and persistence, it is possible that over time the invasion of this SAV community could decrease its ecological impact. A landscape-scale approach allows measurements of all invasion fronts and the spatial anisotropies associated with spread processes and persistence patterns, without spatial interpolation, at locations both proximate and distant to the focus of invasion at multiple points in time. [ABSTRACT FROM AUTHOR]

Frequent invasions in coastal ecosystems result in novel species interactions that have unknown ecological consequences. Largemouth BassMicropterus salmoidesand Brazilian waterweedEgeria densaare introduced species in the Sacramento–San Joaquin River Delta (the Delta) of California, a highly modified estuary. In this system, Brazilian waterweed and Largemouth Bass have seen marked increases in distribution and abundance in recent decades, but their association has not been specifically studied until now. We conducted a 2-year, bimonthly electrofishing survey with simultaneous sampling of water quality and submerged aquatic vegetation (SAV) biomass at 33 locations throughout the Delta. We used generalized linear mixed models to assess the relative influences of water temperature, conductivity, Secchi depth, and SAV biomass density on the abundance of both juvenile-sized and larger Largemouth Bass. Water temperature had a positive relationship with the abundance of both size-classes, but only juvenile-sized fish had a positive association with SAV biomass density, with highest abundances at intermediate SAV densities. In contrast, larger fish were generally ubiquitous across all sampling conditions, even when SAV was absent or present at low densities. Our results on the Largemouth Bass–SAV relationship are consistent with those of previous studies from lake systems within the Largemouth Bass's native range, where they interact with a different SAV species assemblage. These results are supportive of the hypothesis that the proliferation of Brazilian waterweed has expanded Largemouth Bass rearing habitat in the Delta. Finally, this study has implications for tidal wetland restoration plans for the Delta, suggesting that the larger-sized Largemouth Bass may still inhabit restored areas even if invasive SAV establishment is limited. Received March 30, 2015; accepted October 27, 2015 [ABSTRACT FROM AUTHOR]

Greenberg, Jonathan Asher, Erin L. Hestir, David Riano, George J. Scheer, and Susan L. Ustin, 2012. Using LiDAR Data Analysis to Estimate Changes in Insolation Under Large-Scale Riparian Deforestation. Journal of the American Water Resources Association (JAWRA) 48(5): 939-948. DOI: 10.1111/j.1752-1688.2012.00664.x Abstract: Riparian vegetation provides shade from insolation to stream channels. A consequence of removing vegetation may be an increase in insolation that can increase water temperatures and negatively impact ecosystem health. Although the mechanisms of riparian shading are well understood, spatially explicit, mechanistic models of shading have been limited by the data requirements of precisely describing the three-dimensional structure of a riparian corridor. Remotely acquired, high spatial resolution LiDAR data provide detailed three-dimensional vegetation structure and terrain topography over large regions. By parameterizing solar radiation models that incorporate terrain shadowing with LiDAR data, we can produce spatially explicit estimates of insolation. As a case study, we modeled the relative change in insolation on channels in the Sacramento-San Joaquin River Delta under current conditions and under a hypothesized deforested Delta using classified LiDAR, rasterized at a 1-m resolution. Our results suggest that the removal of levee vegetation could result in a 9% increase in solar radiation incident on Delta waters, and may lead to water temperature increases. General, coarse-scale channel characteristics (reach width, azimuth, levee vegetation cover, and height) only accounted for 72% of the variation in the insolation. This indicates that the detailed information derived from LiDAR data has greater explanatory power than coarser reach-scale metrics often used for insolation estimates. [ABSTRACT FROM AUTHOR]

Summary [ABSTRACT FROM AUTHOR]