Abstract Background Studies into biofilms and interactions with anthropogenic substrates like microplastic polymers are predominantly represented in the literature concerning marine environments. Less is known about microplastics in riverine environments that feed the microplastic accumulation of marine environments, transporting potentially harmful or pathogenic organisms that have accumulated on the microplastics. Environmental nutrient loads, seasonality, and geography are all known to influence microbiome formation. This project compared the microbial diversity of biofilms that developed on microplastics to natural stone substrates in an impaired and unimpaired section of the Quinnipiac River Watershed. We evaluated microbial diversity and composition via 16S rRNA gene sequencing while monitoring total colony and fecal coliform colony counts using standard water monitoring methods. Results Total coliform colony counts were higher in the impaired Quinnipiac River than in unimpaired Honeypot Brook (W = 583, p = 0.037) and on the microplastic substrate than stone substrate (W = 1038, p = 0.022). Sequenced features to the class level were dominated by Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria, comprising 75% of the community biome. Simpson’s Diversity indices indicated that within the two substrates, there was little variation in the features present. However, it was noted that microplastic alpha diversity trended slightly lower than the stone. Further analysis of common aquatic enteropathogens showed that the genera Citrobacter was significantly more abundant on the microplastics at both locations. Conclusions Our results indicate impaired waterbodies with a microplastic burden may retain greater fecal coliform bacterial loads than unimpaired waterbodies. Increased microplastic loads in compromised lotic systems may have an additive impact. Water quality remediation and careful monitoring are recommended to reduce this effect. Comparing this study with environmental community analysis could provide valuable insight into preferential surface attachment of bacteria onto microplastic.
Intensively managed restored wetlands and flooded croplands of California's Central Valley support millions of wintering waterbirds.While the benefits to wintering waterfowl are well documented, the effect of intensive management on birds at other times of the year is less clear.Practices such as drainage, mowing, disking and burning may be a nuisance to these nontarget birds at best or life threatening at worst.Alternatively, irrigation over the summer may create habitat that might otherwise be lacking in the dry season.Our objective was to assess the influence of management, adjacent land use, and habitat characteristics on the richness, diversity, and occupancy of birds other than waterfowl in the spring and summer.We conducted 640 bird surveys on restored wetlands managed at varying levels in 2008 (4 April-30 July) and 2009 (19 April-16 July) and used likelihood-based modeling to evaluate occupancy and the relative importance of intensity of management and various environmental factors.Management was not the most important predictor of the richness, diversity, or occupancy of nontarget birds in the summer; rather, variables such as wetland size, vegetation composition, and landscape characteristics were more important for most bird guilds.Contrary to the commonly held view that restored wetlands in California's Central Valley support only wintering waterfowl, they also support a diverse avifauna year round regardless of how they are managed.Bird occupancy and diversity in restored wetlands may be enhanced by creating and maintaining large, complex mosaics of vegetation.
Abstract As many as 500,000 waterfowl reside in California, USA, during summer, but little is known about the availability or quality of their habitats. Wetland size and distribution serve as proximate cues for habitat selection by breeding waterfowl in other parts of North America such as the Prairie Pothole Region. In heavily modified landscapes such as California's Central Valley, disturbance from factors like crop cultivation and urban development may limit access, affect survival, and decrease reproductive success. Water limitations due to recurring seasonal droughts pose another potential threat to breeding waterfowl. Spatial and temporal disparities in environmental resources may provide clearer indications of ultimate habitat selection. We addressed waterfowl habitat selection in 9 regions surveyed annually by California's Department of Fish and Wildlife to determine relative importance of drought severity, wetland area, and habitat quality on mallard ( Anas platyrhynchos ) and other waterfowl population dynamics from 2007–2019. High‐quality habitat supports long‐term population persistence of waterfowl. This study period included an extended drought (2012–2015) and flooding (2016–2017). Statewide, habitat quality was the best predictor of mallard and other waterfowl population fluctuations. The model that included intermediate habitat quality, which accounted for influence of adjacent land‐use, outperformed models that included wetland area alone. At the regional level, drought severity out‐ranked other variables in most regions, suggesting management at regional scales must account for climate. Drought accounted for bird declines in some regions and possible increases in others. This information could be used to identify areas for conservation priority based on projected drought frequency and severity.
The relative influence of physical, chemical, and biotic wetland characteristics on wetland use by spring migrating lesser scaup (Aythya affinis (Eyton); hereafter scaup) is not well understood. We com- pared characteristics of used and unused wetlands in eastern South Dakota. Used wetlands were larger (>2 ha; P = 0.05), with higher amphipod densities (>500 individuals m -2 ; P = 0.01) and higher chlorophyll-a concentra- tions (>0.2; P < 0.05). These wetlands had lower ionic conductivity (1.8 mS; P = 0.02), lower nitrates (1.0 ppm; P = 0.01), lower submerged aquatic vegetation density (P < 0.01), and lower fine sediment proportions (≤150 µm grain size; P < 0.01). Wetland use was best described by amphipod and submerged aquatic vegetation densities. The predictive model explained 50.4% of the variation in scaup use in a reserve dataset. Thresholds of tolerance by amphipods in relation to wetland habitats in the upper Midwest should be investigated further as indicators of a broader range of water and habitat quality characteristics for scaup.
The Wetlands Reserve Program (WRP) is one of several programs implemented by the United States Department of Agriculture to facilitate natural resource management on private lands. Since the WRP’s inception approximately 29,000 ha in California’s Central Valley (CCV) have been restored. However until now, actual benefits of the program to wildlife have never been evaluated. Hydrology in the CCV has been heavily modified and WRP wetlands are managed primarily to support wintering waterfowl. We surveyed over 60 WRP easements in 2008 and 2009 to quantify avian use and categorized bird species into 11 foraging guilds. We detected over 200 bird species in 2008 and 119 species in 2009, which is similar to or higher than numbers observed on other managed sites in the same area. We found that actively managed WRP wetlands support more waterfowl than sites under low or intermediate management, which is consistent with intended goals. Despite reported water shortages, greater upland and un-restored acreage in the southern CCV, WRP wetlands support large numbers of waterfowl and shorebirds, particularly in the early fall months. This is probably due to the severe lack of alternative habitat such as wildlife friendly crops at appropriate stages of the migration cycle. Improved access to water resources for hydrological management would greatly enhance waterfowl use in the southern CCV.
Primary ecosystem services provided by freshwater wetlands in the California Central Valley, USA, include water quality improvement, biodiversity support, and flood storage capacity. We describe these services for freshwater marshes, vernal pools, and riparian wetlands and the implications for wetlands restored under USDA programs in the Central Valley. California's Central Valley is a large sedimentary basin that was once covered by grasslands, extensive riparian forests, and freshwater marshes that today have been converted to one of the most intensive agricultural areas on earth. Remaining freshwater wetlands have been heavily altered, and most are intensively managed. Nitrogen loading from agriculture to surface and groundwater in the Central Valley was estimated to be 34.7 × 10 6 kg N/yr. Atmospheric deposition of nitrogen in the Central Valley was estimated to be 44.3 × 10 6 kg N/yr, of which ∼1.5 × 10 6 kg N/yr was introduced directly to wetlands. Our analysis indicates that wetlands enrolled in the USDA Wetland Reserve Program (WRP) may potentially denitrify the NO 3 ‐N load from relatively unpolluted source water in <18 days, but the potential to denitrify the NO 3 ‐N load from highly polluted source water is uncertain. Water management strongly influences use, diversity, and abundance of avian fauna as well as other biota. Freshwater marshes in the region continue to support important populations of breeding and wintering waterfowl and shorebirds whose populations fluctuate seasonally. Avian diversity in the little remaining area of Central Valley's riparian wetlands is also high and influenced by stand maturity, heterogeneity, and diversity. USDA conservation practices that promote these characteristics may support avian diversity. Effects of USDA conservation practices on non‐avian fauna are poorly understood and warrant further study.
Since most wetlands in the Sacramento Valley of California are dependent on artificial water delivery, supplying water for wetland management is the greatest challenge to wetland managers, especially during drought years. Efforts are needed to improve the security of water supplies for optimal habitat management and water quality improvement. This study contributes to these efforts by developing an eco-hydrologic model (Agricultural Policy/Environmental Extender [APEX]) of this wetland system, which has key components evaluated in the wetland simulation, including wetting and drying of wetland soils, competition and response of wetland species to wetland hydrology, settling of sediment, and nitrogen (N) removal. APEX model calibration (April of 2017 to May of 2018) and validation (June of 2018 to August of 2018) resulted in a percentage bias (PB) of 9.8% and –8.5%, respectively, for total volume of water holding in four serially connected wetlands. The N contents in the wetland waterbody were calibrated and validated using the monitored values collected during 2017 to 2018 and 2015 to 2016, respectively. All PB values for calibration and validation were over 35%. The calibrated model was used to evaluate the effects of wetland management and increasing temperature on N removal. Moreover, an additive regression model (ARM) was developed based on bird survey data and used to analyze bird dropping seasonal patterns and access their impacts on water quality in the studied wetlands. Based on the results of the model, the wetland water quality was influenced by waterfowl populations and eventually governed by water availability in each wetland cell. The N removal by wetlands was negatively affected by the volume of irrigation water. Moreover, increasing temperature caused a decrease in waterfowl population, which led to decreased N concentration by up to 42%. Overall, the results indicate that the developed model can be effectively used to quantify the effects of wetland management on water balance, water quality, and vegetation and to describe the nexus of wetland management, water use, and ecosystem service functions of managed wetlands.
