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At least 829 records · Page 46Linked to original sources

Bridging the energy gap: Anadromous blueback herring feeding in the Hudson and Mohawk rivers, New York

Adult blueback herring Alosa aestivalis (N = 116) were collected during the 1999, 2000, and 2002-2004 spawning runs from sites on the Hudson and Mohawk rivers, and gut contents were analyzed. Thirty-four fish (33% of those examined) were found to contain food material. Food items were present in 41% of Mohawk River samples and 11% of Hudson River samples; all Hudson River fish containing food were captured in small tributaries above the head of tide. Hudson River fish predominantly consumed zooplankton, while Mohawk River fish consumed benthic aquatic insects in large quantities, including Baetidae, Ephemeridae, and Chironomidae. Using stable isotope analysis and a mixing model, we found that fish collected later in the season had significantly decreased marine-derived C. Condition indices of later-season fish were equal to or greater than those of fish collected earlier in the season. Blueback herring in this system may face increased energy requirements as they migrate farther upstream during spawning runs, and feeding may provide energy subsidies needed to maintain fitness over their expanded migratory range. ?? Copyright by the American Fisheries Society 2007.

Transactions of the American Fisheries Society↗

Effects of climatic variations over 11 years on nitrate-nitrogen concentrations in the Raccoon River, Iowa

Nitrate-nitrogen (NO3-N) concentrations at public water supply intakes on the Des Moines and Raccoon Rivers in Iowa exceeded the maximum contaminant level (MCL) of 10 mg L-1 for public water supplies established by the USEPA for extended periods of time from March through early August 1990. The excessive NO3-N levels followed 2 yr of less-than normal precipitation in 1988 and 1989. The largest daily NO3-N load (771 t) transported during the last 17 yr in the Raccoon River occurred in June 1990. The streamflow hydrograph for the Raccoon River for March 1990 prior to seasonal fertilizer application indicates that high NO3-N concentrations characterize the recession side of the hydrograph. High NO3-N concentrations in streamflow persisted as streamflow decreased to baseflow conditions. This implies that substantial quantities of NO3-N were being leached from the soil and transported by subsurface flow during early 1990. A multiple linear-regression model was developed to predict NO3-N concentrations in the Raccoon River from readily-obtainable streamflow and climatic data. The four-variable model explained about 70% of the variability in the concentration of NO3-N. The mean streamflow for the previous 7-d period accounted for about 50% of the total variability.

Iowa↗

Davis Pond freshwater prediversion biomonitoring study: freshwater fisheries and eagles

In January 2001, the construction of the Davis Pond freshwater diversion structure was completed by the U.S. Army Corps of Engineers. The diversion of freshwater from the Mississippi River is intended to mitigate saltwater intrusion from the Gulf of Mexico and to lessen the concomitant loss of wetland areas. In addition to the freshwater inflow, Barataria Bay basin would receive nutrients, increased flows of sediments, and water-borne and sediment-bound compounds. The purpose of this biomonitoring study was, therefore, to serve as a baseline for prediversion concentrations of selected contaminants in bald eagle ( Haliaeetus leucocephalus ) nestlings (hereafter referred to as eaglets), representative freshwater fish, and bivalves. Samples were collected from January through June 2001. Two similarly designed postdiversion studies, as described in the biological monitoring program, are planned. Active bald eagle nests targeted for sampling eaglet blood (n = 6) were generally located southwest and south of the diversion structure. The designated sites for aquatic animal sampling were at Lake Salvador, at Lake Cataouatche, at Bayou Couba, and along the Mississippi River. Aquatic animals representative of eagle prey were collected. Fish were from three different trophic levels and have varying feeding strategies and life histories. These included herbivorous striped mullet ( Mugil cephalus ), omnivorous blue catfish ( Ictalurus furcatus ), and carnivorous largemouth bass ( Micropterus salmoides ). Three individuals per species were collected at each of the four sampling sites. Freshwater Atlantic rangia clams ( Rangia cuneata ) were collected at the downstream marsh sites, and zebra mussels ( Dreissena spp.) were collected on the Mississippi River. The U.S. Geological Survey (USGS) Biomonitoring of Environmental Status and Trends (BEST) protocols served as guides for fish sampling and health assessments. Fish are useful for monitoring aquatic ecosystems because they accumulate pesticides and other contaminants. Biomarker data on individual fish, generated at the USGS National Wetlands Research Center (Lafayette, La.), included percent white blood cells in whole blood, spleen weight to body weight ratio, liver weight to body weight ratio, condition factor, splenic macrophage aggregates, and liver microsomal 7-ethoxyresorufin-o-deethylase (EROD) activity. Fish age was estimated by comparing total lengths with values from the same species in the Southeast United States as determined from the literature. Contaminant analyses were coordinated by the U.S. Fish and Wildlife Service (USFWS) Analytical Control Facility (Laurel, Md.), where residues of organochlorine (OC) pesticides, total polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), aliphatic hydrocarbons (AHs), and trace elements were determined. The organic contaminant data were generated at the Mississippi State University Chemical Lab (Mississippi State, Miss.), and the inorganic contaminant data were generated by the Texas A&M University Geochemical and Environmental Research Group (College Station, Tex.). Statistical tests were performed to assess relationships among contaminants, fish age, fish species, and collection sites. Trends in interspecific differences among fish in concentrations of contaminants were noted. Striped mullet (hereafter mullet) frequently displayed the highest chemical concentrations. Levels of contaminants were generally higher in samples obtained from the Mississippi River than in those collected from the diversion area and were higher in mussels and clams (hereafter bivalves) than in fish. Because the Mississippi River sampling site for mullet and largemouth bass was downriver of the structure and south of New Orleans and the catfish site was upriver, the downriver data may not be directly reflective of the results from the receiving waters at the Davis Pond structure. Compared to the Caernarvon freshwater prediversion study in 1990 that assessed possible influx of contaminants with the freshwater diversion, contaminant levels in fishes and bivalves in this study were generally lower, yet three nontoxic inorganic elements in Davis Pond fish samples exhibited ranges of concentrations that were more than two times higher than did those from Caernarvon. Levels in bivalves were different between diversions but about equal in the numbers of trace elements showing high levels per location. Contaminant values were compared to those listed in various literature and agency sources, both regional and national, including the National Contaminant Biomonitoring Program (NCBP), in which the 85th percentile and above represents what is considered to be an elevated contaminant concentration and cause for concern. Generally, bivalves were at the high end of their ranges for both organic and inorganic contaminants. In this study, OCs were detectable in 67 percent of fish from the Mississippi River site, ranging from 0.15 to 1.09 μg/g wet weight (ww) or fresh weight (fw), and in 11 percent of the fish from the marsh sites, ranging from 0.06 to 0.612 μg/g ww. Bivalves from the Mississippi River had OC levels of 0.096 μg/g ww, whereas none were detectable in bivalves at the marsh sites. In this study, p,p ’-dichlorodiphenyldichloroethylene ( p,p’ -DDE) (a biodegradation product of DDT [dichlorodiphenyl trichloroethane]) and total PCBs were the most frequently detected OCs and were primarily from the Mississippi River. For total OC content, using adjusted least squares means, some significant interactions were noted between fish species and sites. PAHs were detected in aquatic animals at all sites (range of 0.017–17.534 μg/g ww), as were AHs (range of 0.423–4.549 μg/g ww); the highest levels of PAHs and AHs were found in bivalves from the Mississippi River. When analysis of variance (α = 0.05) was performed with data from aquatic animals, there were only two significant relationships between PAHs, AHs, and OCs between species, site, and age or the interaction among these variables. There was an interaction between fish species and n-decane (an AH) in that mullet and largemouth bass had significantly higher levels than did catfish ( P = 0.0175). When general linear means were used to investigate associations of inorganic contaminants among fish species, site, and age or any interactions among these variables, no significant results were noted for arsenic, cadmium, lead, beryllium, boron, molybdenum, or nickel. The range of mercury in fish in this study was 0.04–0.14 μg/g ww (0.14– 0.48 μg/g dry weight [dw]), with the most elevated levels detected in predatory largemouth bass at the sampling point farthest downstream from the structure and within the marsh area. Mercury was positively correlated with fish age ( P = 0.0152), where levels were estimated to increase 0.0253 parts per million (ppm) dw per year. In the Mississippi River, catfish showed significantly higher levels of mercury than did mullet or largemouth bass ( P = 0.00167). Among fish species, mullet displayed the highest levels in fish of aluminum, barium, manganese, and iron, all considered to have low toxicity in hydrologic systems. An interaction between fish and site was seen with aluminum ( P = 0.0031), where concentrations in mullet were significantly higher in the Mississippi River than at the other sites, as was also seen with barium ( P = 0.0009), chromium ( P = <0.0001), manganese ( P = 0.0004), strontium ( P = 0.0074), vanadium ( P = 0.0156), and zinc ( P = 0.0059). For iron ( P = 0.0.0001), mullet and largemouth bass at both the Mississippi River and Lake Salvador showed higher levels than did catfish, and these two species showed higher levels at two of the four sites. An interaction between fish and site was also seen with chromium ( P = <0.0001) in that concentrations in mullet were significantly higher in the Mississippi River than at the other sites, as was also seen with strontium ( P = 0.0074), vanadium ( P = 0.0156), and zinc ( P = 0.0059), metals for which deleterious effects have been demonstrated in other ecosystems. The NCBP program lists the 85th percentile for zinc at 34.2 μg/g fw (117.9 μg/g dw). In the Davis Pond prediversion biomonitoring study (hereafter the current study), one fish (MUL31RIVER, fish ID 8) showed values higher than that (125.4 μg/g dw or 37.54 μg/g ww), and the Mississippi River bivalve sample (MUSSRIVER) had a value of 140 μg/g dw (41.2 μg/g ww). In the current study, approximately 86 percent of the fish had measurable selenium levels, yet none reached the 85th percentile. The 85th percentile for selenium from the NCBP was 0.73 μg/g ww. Significantly higher levels of selenium were seen in mullet than in largemouth bass and catfish ( P = 0.0023). The NCBP 85th percentile for lead is 0.22 μg/g ww (0.76 μg/g dw). In the current study, the range of concentrations of lead was as much as 18.3 ppm dw (MUL31RIVER, fish ID 8), with the three most elevated values (range of 3.46–5.31 μg/g ww) coming from mullet from the Mississippi River. Biomarker data are measurable and directly reflect the condition of the animal, and measuring more than one biomarker in an individual increases confidence in health assessments. In the current study, biomarkers included macrophage aggregates (MAs), liver (hepatosomatic index [HSI]) and spleen (splenosomatic index [SSI]) weight to body weight ratios, percent white blood cells (WBCs) in whole blood, and condition factor. Few significant differences were noted with any of the biomarkers between sites, and there were no relationships between species and sites. For improved use of biomarker assessments, an increase in fish sample size would be useful for postdiversion sampling, as would comparisons of fish of the same sex and reproductive condition. During the current study, success for eagle nests in the diversion area and reference sites was similar as determined by numbers of nestlings fledged. When temperatures were below average during winter 2000, nests in both regions similarly failed. At each nest, the primary evidence of food items was small mammals. Eaglets (n = 6) generally appeared healthy, and whole blood concentrations of organic contaminants exceeded detection limits with three incidences of p,p’ -DDE (0.002–0.006 μg/L ww) and one incidence of oxychlordane (0.002 μg/L ww). The levels of p,p’ -DDE were well below those that have been inversely correlated with productivity and success rates of nesting bald eagles on a regional scale. The low values found in the whole blood samples for OC pesticides and PCBs were even lower when corrected for plasma volume. Aluminum values were 3.66 and 5.75 μg/L in two samples, zinc ranged from 5.21 to 6.77 μg/L ww in six samples, and silicon ranged from 1.7 to 4.6 μg/L in four samples. Selenium was detectable in each bird with the range at 0.332–0.566 μg/L ww, and strontium ranged from 0.0581 to 0.0975 μg/L ww. Mercury was detectable in blood samples from each bird and ranged from 0.0254 to 0.0845 μg/L ww, whereas lead was detectable in four samples and ranged from 0.0042 to 0.0136 μg/L ww. Although no detectable levels of total PCBs were found (also correlated with decreased reproductive productivity), 70 percent of the aquatic animals from the Mississippi River contained total PCBs (range 0.13–0.79 μg/L), whereas only about 7 percent of the aquatic animals sampled from the marsh area contained PCBs. Suggestions for postdiversion sampling include lowering the analytical detection limit for some metals, sampling aquatic animals over the course of a single season, obtaining a higher sample number of mature fish of one species (for example, blue catfish) within a range of total lengths for biomarker analyses, obtaining otoliths for estimating fish ages, assessing dioxins in eaglet blood, examining triazines in water, and obtaining all Mississippi River fish samples as close to the Davis Pond structure intake as possible. Because contaminants found in blood of eaglets reflect their prey species and because of the contaminant levels found in fish in the current study, eaglets may not be consuming primarily these species; therefore, obtaining juvenile nutria ( Myocastor coypus ) or turtle species for contaminant analyses might be considered, as well as collecting greater blood volume and using plasma to measure OCs and PCBs. Data obtained postdiversion will be compared with prediversion data to monitor changes.

Louisiana↗

Ground-water hydrology of the Willamette basin, Oregon

The Willamette Basin encompasses a drainage of 12,000 square miles and is home to approximately 70 percent of Oregon's population. Agriculture and population are concentrated in the lowland, a broad, relatively flat area between the Coast and Cascade Ranges. Annual rainfall is high, with about 80 percent of precipitation falling from October through March and less than 5 percent falling in July and August, the peak growing season. Population growth and an increase in cultivation of crops needing irrigation have produced a growing seasonal demand for water. Because many streams are administratively closed to new appropriations in summer, ground water is the most likely source for meeting future water demand. This report describes the current understanding of the regional ground-water flow system, and addresses the effects of ground-water development. This study defines seven regional hydrogeologic units in the Willamette Basin. The highly permeable High Cascade unit consists of young volcanic material found at the surface along the crest of the Cascade Range. Four sedimentary hydrogeologic units fill the lowland between the Cascade and Coast Ranges. Young, highly permeable coarse-grained sediments of the upper sedimentary unit have a limited extent in the floodplains of the major streams and in part of the Portland Basin. Extending over much of the lowland where the upper sedimentary unit does not occur, silts and clays of the Willamette silt unit act as a confining unit. The middle sedimentary unit, consisting of permeable coarse-grained material, occurs beneath the Willamette silt and upper sedimentary units and at the surface as terraces in the lowland. Beneath these units is the lower sedimentary unit, which consists of predominantly fine-grained sediments. In the northern part of the basin, lavas of the Columbia River basalt unit occur at the surface in uplands and beneath the basin-fill sedimentary units. The Columbia River basalt unit contains multiple productive water-bearing zones. A basement confining unit of older marine and volcanic rocks of low permeability underlies the basin and occurs at land surface in the Coast Range and western part of the Cascade Range. Most recharge in the basin is from infiltration of precipitation, and the spatial distribution of recharge mimics the distribution of precipitation, which increases with elevation. Basinwide annual mean recharge is estimated to be 22 inches. Rain and snowmelt easily recharge into the permeable High Cascade unit and discharge within the High Cascade area. Most recharge in the Coast Range and western part of the Cascade Range follows short flowpaths through the upper part of the low permeability material and discharges to streams within the mountains. Consequently, recharge in the Coast and Ranges is not available as lateral ground-water flow into the lowland, where most ground-water use occurs. Within the lowland, annual mean recharge is 16 inches and most recharge occurs from November to April, when rainfall is large and evapotranspiration is small. From May to October recharge is negligible because precipitation is small and evapotranspiration is large. Discharge of ground water is mainly to streams. Ground-water discharge is a relatively large component of flow in streams that drain the High Cascade unit and parts of the Portland Basin where permeable units are at the surface. In streams that do not head in the High Cascade area, streamflow is generally dominated by runoff of precipitation. Ground-water in the permeable units in the lowland discharges to the major streams where there is a good hydraulic connection between aquifers and streams. Ground-water discharge to smaller streams, which flow on the less permeable Willamette silt unit, is small and mostly from the Willamette silt unit. Most ground-water withdrawals occur within the lowland. Irrigation is the largest use of ground water, accounting for 240,000 acre feet of withdrawals, or 81 p

Scientific Investigations Report↗

Effects of climate, vegetation, and soils on consumptive water use and ground-water recharge to the Central Midwest Regional aquifer system, mid-continent United States

The Central Midwest aquifer system, in parts of Arkansas, Colorado, Kansas, Missouri, Nebraska, New Mexico, South Dakota, and Texas, is a region of great hydrologic diversity. This study examines the relationships between climate, vegetation, and soil that affect consumptive water use and recharge to the groundwater system. Computations of potential recharge and consumptive water use were restricted to those areas where the aquifers under consideration were the immediate underlying system. The principal method of analysis utilized a soil moisture computer model. This model requires four types of input: (1) hydrologic properties of the soils, (2) vegetation types, (3) monthly precipitation, and (4) computed monthly potential evapotranspiration (PET) values. The climatic factors that affect consumptive water use and recharge were extensively mapped for the study area. Nearly all the pertinent climatic elements confirmed the extreme diversity of the region. PET and those factors affecting it--solar radiation, temperature, and humidity--showed large regional differences; mean annual PET ranged from 36 to 70 inches in the study area. The seasonal climatic patterns indicate significant regional differences in those factors affecting seasonal consumptive water use and recharge. In the southern and western parts of the study area, consumptive water use occurred nearly the entire year; whereas, in northern parts it occurred primarily during the warm season (April through September). Results of the soil-moisture program, which added the effects of vegetation and the hydrologic characteristics of the soil to computed PET values, confirmed the significant regional differences in consumptive water use or actual evapotranspiration (AET) and potential groundwater recharge. Under two different vegetative conditions--the 1978 conditions and pre-agricultural conditions consisting of only grassland and woodland--overall differences in recharge were minimal. Mean annual recharge under both conditions averaged slightly more than 4.5 inches for the entire study area, but ranged from less than 0.10 inches in eastern Colorado to slightly more than 15 inches in Arkansas.

Arkansas, Colorado, Kansas, Missouri, Nebraska, Ne↗

Some aspects of aquatic insect populations of pools and riffles in gravel bed streams in western United States

Relationships were studied between aquatic-insect populations on rocks of different sizes and variations of populations between different stream localities. All aquatic insects were counted and identified on streambed gravels and cobbles chosen at random from four rivers on three to four types of locations ranging from riffles to pools. The measurements used span 3 to 4 months in 1 year. Insect density (number of insects per unit of rock area) was determined to be a function of rock size. Highest insect densities occurred on rocks between 45 and 90 mm mean diameter, with larger and smaller rocks having lower insect densities. The insect population differed significantly with location within a stream; that is, from pool to riffle, as well as by stream and season.

Journal of Research of the U.S. Geological Survey↗

Diurnal photosynthesis cycle in CAM and non-CAM seasonal pool aquatic macrophytes

Seasonal pools undergo marked diurnal changes in pH, free carbon dioxide, and oxygen levels. Previous studies showed that Isoetes howellii utilized crassulacean acid metabolism (CAM) photosynthesis as a means of assimilating carbon at night when ambient carbon dioxide levels are high. However, much of the pool flora is not CAM. We hypothesized that coexistence under extreme carbon—limiting conditions would select for other photosynthetic characteristics in these non—CAM species. Quantitative carbon uptake measurements wee made in the field on the CAM Isoetes howellii and the non—CAM Eleocharis acicularis, Downingia bella, and Plagiobothrys undulatus. Despite wide phylogenetic separation, thee species are structurally convergent in that they all produce aquatic stage with an isoetid growth form. They are functionally similar in that none appear to utilize bicarbonate, and all are carbon limited through much of the day, as indicated by a marked midday depression in carbon uptake that last through the afternoon. All four species were capable of carbon fixation at night, although only in Isoetes howellii was this accompanied by an overnight accumulation of acid. It was estimated that dark fixation in I. howelli contributed up to 40% of its total carbon gain under submerged conditions, but was <1% under aerial conditions. The role of dark fixation in the other three, non—CAM, species is unknown. Short—term (1 s) steady—term (1 s) steady—state 1 4 C tracer studies in the laboratory revealed that, under submerged conditions in the light, all species assimilated carbon into the C 3 photosynthetic product phosphoglycerate (PGA) and the C 4 photosynthetic products of malate, citrate, and aspartate. The proportion of label fixed into C 4 organic acids was greatest in E. acicularis. The ratio of RuBP carboxylase/PEP carboxylase was broadly similar in all species, ranging from 8.8 to 11.5. When the pools dried down and the plants became aerial, photosynthetic rates increased and a midday depression such as occurred under submergence was not observed. Carbon fixation in the dark became negligible, and the RuBP carboxylase/PEP carboxylase ratio increased. Seasonal changes in biomass showed I. howellii and E. acicularis dominated the pools early in the season, and the biomass of the other two species increased later when the pools dried. The latter species, D. bella and P. undulatus, also had higher rates of photosynthesis under aerial conditions.

Ecology↗

Data logging of body temperatures provides precise information on phenology of reproductive events in a free-living arctic hibernator

Precise measures of phenology are critical to understanding how animals organize their annual cycles and how individuals and populations respond to climate-induced changes in physical and ecological stressors. We show that patterns of core body temperature ( T b ) can be used to precisely determine the timing of key seasonal events including hibernation, mating and parturition, and immergence and emergence from the hibernacula in free-living arctic ground squirrels ( Urocitellus parryii ). Using temperature loggers that recorded T b every 20 min for up to 18 months, we monitored core T b from three females that subsequently gave birth in captivity and from 66 female and 57 male ground squirrels free-living in the northern foothills of the Brooks Range Alaska. In addition, dates of emergence from hibernation were visually confirmed for four free-living male squirrels. Average T b in captive females decreased by 0.5–1.0°C during gestation and abruptly increased by 1–1.5°C on the day of parturition. In free-living females, similar shifts in T b were observed in 78% ( n = 9) of yearlings and 94% ( n = 31) of adults; females without the shift are assumed not to have given birth. Three of four ground squirrels for which dates of emergence from hibernation were visually confirmed did not exhibit obvious diurnal rhythms in T b until they first emerged onto the surface when T b patterns became diurnal. In free-living males undergoing reproductive maturation, this pre-emergence euthermic interval averaged 20.4 days ( n = 56). T b -loggers represent a cost-effective and logistically feasible method to precisely investigate the phenology of reproduction and hibernation in ground squirrels.

Journal of Comparative Physiology B: Biochemical, ↗

Stochastic agent-based model for predicting turbine-scale raptor movements during updraft-subsidized directional flights

Rapid expansion of wind energy development across the world has highlighted the need to better understand turbine-caused avian mortality. The risk to golden eagles ( Aquila chrysaetos ) is of particular concern due to their small population size and conservation status. Golden eagles subsidize their flight in part by soaring in orographic updrafts, which can place them in conflict with wind turbines utilizing the same low-altitude wind resource. Understanding the behavior of soaring raptors in varying atmospheric conditions can therefore be relevant to predicting and mitigating their risk of collision. We present a predictive movement model that simulates individual paths of golden eagles during directional flight (such as migration) that is subsidized by orographic updraft. We modeled eagles in a 50 km by 50 km study area in Wyoming containing three wind power plants with documented golden eagle collisions with turbines. The movement model is applicable to any region where ground elevation is known at turbine scale ( &lt; "> < 50 m) and wind conditions are known at facility scale ( &lt; "> < 3 km). For a given set of atmospheric conditions, the model simulates movements of thousands of orographic soaring eagles to produce a density map quantifying the relative probability of eagle presence. We validated the simulated tracks with GPS telemetry data showing four directional tracks made by golden eagles transiting through the area in 2019 and 2020. For each eagle track, validation was performed using the ratio of the model-simulated eagle presence likelihood with uniform eagle presence and the presence computed using directed random-walk movements. We found that the predictive performance of the model was significantly better (likelihood ratio &gt; "> > 1) for low-altitude movements than high-altitude movements that can involve thermal-soaring. We employed the model to produce seasonal presence maps for migrating golden eagles. We found significant turbine-level variations in eagle presence between northerly and southerly migration routes through the study area. Overall, the proposed model offers a generalizable, probabilistic, and predictive tool to assist wind energy developers, ecologists, wildlife managers, and industry consultants in estimating the potential for conflict between soaring birds and wind turbines, thereby reducing the need for site-specific data on golden eagle movements.

Wyoming↗

Impact of climate variability on runoff in the north-central United States

Large changes in runoff in the north-central United States have occurred during the past century, with larger floods and increases in runoff tending to occur from the 1970s to the present. The attribution of these changes is a subject of much interest. Long-term precipitation, temperature, and streamflow records were used to compare changes in precipitation and potential evapotranspiration (PET) to changes in runoff within 25 stream basins. The basins studied were organized into four groups, each one representing basins similar in topography, climate, and historic patterns of runoff. Precipitation, PET, and runoff data were adjusted for near-decadal scale variability to examine longer-term changes. A nonlinear water-balance analysis shows that changes in precipitation and PET explain the majority of multidecadal spatial/temporal variability of runoff and flood magnitudes, with precipitation being the dominant driver. Historical changes in climate and runoff in the region appear to be more consistent with complex transient shifts in seasonal climatic conditions than with gradual climate change. A portion of the unexplained variability likely stems from land-use change.

Iowa, Kansas, Minnesota, Missouri, Nebraska, North↗

Hunting influences the diel patterns in habitat selection by northern pintails Anas acuta

Northern pintail Anas acuta (hereafter pintail) populations wintering within Suisun Marsh, a large estuarine managed wetland near San Francisco Bay, California,USA, have declined markedly over the last four decades. The reasons for this decline are unclear. Information on how hunting and other factors influence the selection of vegetation types and sanctuaries would be beneficial to manage pintail populations in SuisunMarsh. During 1991-1993, we radio-marked and relocated female pintails (individuals: N = 203, relocations: N = 7,688) within Suisun Marsh to investigate habitat selection during the non-breeding months (winter). We calculated selection ratios for different vegetation types and for sanctuaries, and examined differences in those ratios between hunting season (i.e. hunting and non-hunting), age (hatchyear and after-hatch-year), and time of day (daylight or night hours). We found that diel patterns in selection were influenced by hunting disturbance. For example, prior to the hunting season and during daylight hours, pintails selected areas dominated by brass buttons Cotula coronopifolia, a potentially important food source, usually outside of sanctuary boundaries. However, during the hunting season, pintails did not select brass buttons during daylight hours, but instead highly selected permanent pools, mostly within sanctuaries. Also, during the hunting season, pintails showed strong selection for brass buttons at night. Sanctuaries provided more area of permanent water pools than within hunting areas and appeared to function as important refugia during daylight hours of the hunting season. Wildlife managers should encourage large protected permanent pools adjacent to hunted wetlands to increase pintail numbers within wetland environments and responsibly benefit hunting opportunities while improving pintail conservation.

California↗

Morphology and sedimentation on open-coast intertidal flats of the Changjiang Delta, China

On many intertidal flats, lateral aggradation and reworking by large tidal channels is the dominant sedimentary process. On the open-coast intertidal flats of the Changjiang Delta large laterally migrating tidal channels are absent. Instead, numerous shallow tidal creeks cut across the intertidal flats. On these flats, vertical rather than lateral migration dominates sedimentation. Observations over semidiurnal tidal cycles show that both flood and ebb tides have the potential to deposit their own mud-sand couplets, but four couplets per day are rarely preserved. Reworking by tidal currents and/or weak waves results in loss of tidal couplets or amalgamation of two or more thin couplets into a single thick couplet. Measurements of preserved couplets show that they can represent a single flooding or ebbing event (half day) to a period of several neap-spring cycles. Diastems within amalgamated couplets are generally not distinguishable. The key agent for reworking open-coast intertidal flat deposits is not tidal creek migration but seasonal storm waves. Seasonal storm deposits consist of a basal scour and sand-dominant laminae with mud pebbles, grading upward to mud-dominated layers of fair-weather deposits. Sand-dominated layers are also reworked.

Conference Paper↗

Animal migration amid shifting patterns of phenology and predation: Lessons from a Yellowstone elk herd

Migration is a striking behavioral strategy by which many animals enhance resource acquisition while reducing predation risk. Historically, the demographic benefits of such movements made migration common, but in many taxa the phenomenon is considered globally threatened. Here we describe a long-term decline in the productivity of elk ( Cervus elaphus ) that migrate through intact wilderness areas to protected summer ranges inside Yellowstone National Park, USA. We attribute this decline to a long-term reduction in the demographic benefits that ungulates typically gain from migration. Among migratory elk, we observed a 21-year, 70% reduction in recruitment and a 4-year, 19% depression in their pregnancy rate largely caused by infrequent reproduction of females that were young or lactating. In contrast, among resident elk, we have recently observed increasing recruitment and a high rate of pregnancy. Landscape-level changes in habitat quality and predation appear to be responsible for the declining productivity of Yellowstone migrants. From 1989 to 2009, migratory elk experienced an increasing rate and shorter duration of green-up coincident with warmer spring&ndash;summer temperatures and reduced spring precipitation, also consistent with observations of an unusually severe drought in the region. Migrants are also now exposed to four times as many grizzly bears ( Ursus arctos ) and wolves ( Canis lupus ) as resident elk. Both of these restored predators consume migratory elk calves at high rates in the Yellowstone wilderness but are maintained at low densities via lethal management and human disturbance in the year-round habitats of resident elk. Our findings suggest that large-carnivore recovery and drought, operating simultaneously along an elevation gradient, have disproportionately influenced the demography of migratory elk. Many migratory animals travel large geographic distances between their seasonal ranges. Changes in land use and climate that disparately influence such seasonal ranges may alter the ecological basis of migratory behavior, representing an important challenge for, and a powerful lens into, the ecology and conservation of migratory taxa.

Idaho, Montana, Wyoming↗

Yellow-Billed Cuckoo Distribution, Abundance, and Habitat Use Along the Lower Colorado and Tributaries, 2006 Annual Report

Executive Summary This 2006 annual report details the first season of a 2-year study documenting western yellow-billed cuckoo (Coccyzus americanus occidentalis) distribution, abundance, and habitat use throughout the Lower Colorado River Multi-Species Conservation Plan boundary area. We conducted cuckoo surveys at 55 sites within 17 areas, between 11 June and 13 September. The 243 visits across all sites yielded 180 yellow-billed cuckoo detections. Cuckoos were detected at 27 of the 55 sites, primarily at the Bill Williams River National Wildlife Refuge AZ sites (n = 117 detections) and the Grand Canyon National Park-Lake Mead National Recreation Area AZ delta sites (n = 29 detections). There were also cuckoos at the Gila River-Colorado River Confluence, AZ (n = 9), Overton Wildlife Management, NV area (n = 7), and Limitrophe Division North, AZ (n = 6); however, at these sites the numbers were much lower and very few of these birds were considered to be paired or breeding. The greatest number of detections (n = 79) occurred during the second survey period (3-23 July). In 2006, we confirmed five breeding events, including one nesting observation and sightings of four juveniles; all confirmed breeding was at the Bill Williams River NWR and Grand Canyon NP-Lake Mead NRA delta sites. The breeding status of most of our detections were unknown, however, we observed 17 adult cuckoos carrying nest material or food and 40 cuckoo detections were detected while counter-calling occurred in same area during repeated surveys. We used playback recordings to survey for western yellow-billed cuckoos. Compared to simple point counts or surveys, this method increases the number of detections of this secretive, elusive species. It has long been suspected that cuckoos have a fairly low response rate, and that the standard survey method of using playback recordings may fail to detect all birds present in an area. In 2006, we found that the majority (72%) of cuckoo detections were solicited through playback at all study sites. The number of solicited detections peaked during the first half of July and then declined as the breeding season progressed, while the number of unsolicited detections (cuckoos heard calling before playback was initiated) remained fairly constant. The majority (64%) of cuckoo detections, solicited or unsolicited, were aural; 27 percent were both heard and seen and nine percent were visual detections only. Cuckoos in areas with the largest populations had the highest rate of vocalizations before playback or after the first broadcast. In contrast, more than half the responses at sites with fewer cuckoos (with < 10 detections per site) first occurred after three or more playback recordings. This type of baseline information will be used to help refine the survey protocol for 2007, and to create hypotheses that can serve as the foundation for a full-scale evaluation and optimization of this survey technique. Our preliminary analysis of vegetation data from occupied and unoccupied sites in 2006 focused on general patterns in the distribution and abundance of woody species. The density and composition of woody riparian vegetation varied considerably among the study areas. Much of the variation in tree density was due to the patterns of abundance of trees in the smallest size class (< 8 cm dbh). The dominant tree species at the cuckoo survey sites were cottonwood, willow, and tamarisk. Tamarisk was the most common tree, due to the abundance of small (< 8 cm dbh) individuals. When occupied and unoccupied sites were compared, occupied sites tended to have higher average canopy cover, attributable to higher average cover of the mid and low canopy. The dominant canopy at occupied sites most often consisted of cottonwood or willow trees. In addition, occupied sites in most areas had lower than average total tree density whereas unoccupied sites were denser than average. When densities of trees in different size classes were com

Open-File Report↗

Seasonal variation in nutrient retention during inundation of a short-hydroperiod floodplain

Floodplains are generally considered to be important locations for nutrient retention or inorganic-to-organic nutrient conversions in riverine ecosystems. However, little is known about nutrient processing in short-hydroperiod floodplains or seasonal variation in floodplain nutrient retention. Therefore, we quantified the net uptake, release or transformation of nitrogen (N), phosphorus (P) and suspended sediment species during brief periods (1-2 days) of overbank flooding through a 250-m floodplain flowpath on the fourth-order Mattawoman Creek, Maryland U.S.A. Sampling occurred during a winter, two spring and a summer flood in this largely forested watershed with low nutrient and sediment loading. Concentrations of NO3- increased significantly in surface water flowing over the floodplain in three of the four floods, suggesting the floodplain was a source of NO3-. The upper portion of the floodplain flowpath consistently exported NH4+, most likely due to the hyporheic: flushing of floodplain soil NH4+, which was then likely nitrified to NO3- in floodwaters. The floodplain was a sink for particulate organic P (POP) during two floods and particulate organic N and inorganic suspended sediment (ISS) during one flood. Large releases of all dissolved inorganic N and P species occurred following a snowmelt and subsequent cold winter flood. Although there was little consistency in most patterns of nutrient processing among the different floods, this floodplain, characterized by brief inundation, low residence time and low nutrient loading, behaved oppositely from the conceptual model for most floodplains in that it generally exported inorganic nutrients and imported organic nutrients.

River Research and Applications↗

Dissolved organic carbon in Alaskan boreal forest: Sources, chemical characteristics, and biodegradability

The fate of terrestrially-derived dissolved organic carbon (DOC) is important to carbon (C) cycling in both terrestrial and aquatic environments, and recent evidence suggests that climate warming is influencing DOC dynamics in northern ecosystems. To understand what determines the fate of terrestrial DOC, it is essential to quantify the chemical nature and potential biodegradability of this DOC. We examined DOC chemical characteristics and biodegradability collected from soil pore waters and dominant vegetation species in four boreal black spruce forest sites in Alaska spanning a range of hydrologic regimes and permafrost extents (Well Drained, Moderately Well Drained, Poorly Drained, and Thermokarst Wetlands). DOC chemistry was characterized using fractionation, UV-Vis absorbance, and fluorescence measurements. Potential biodegradability was assessed by incubating the samples and measuring CO2 production over 1 month. Soil pore water DOC from all sites was dominated by hydrophobic acids and was highly aromatic, whereas the chemical composition of vegetation leachate DOC varied significantly with species. There was no seasonal variability in soil pore water DOC chemical characteristics or biodegradability; however, DOC collected from the Poorly Drained site was significantly less biodegradable than DOC from the other three sites (6% loss vs. 13-15% loss). The biodegradability of vegetation-derived DOC ranged from 10 to 90% loss, and was strongly correlated with hydrophilic DOC content. Vegetation such as Sphagnum moss and feathermosses yielded DOC that was quickly metabolized and respired. In contrast, the DOC leached from vegetation such as black spruce was moderately recalcitrant. Changes in DOC chemical characteristics that occurred during microbial metabolism of DOC were quantified using fractionation and fluorescence. The chemical characteristics and biodegradability of DOC in soil pore waters were most similar to the moderately recalcitrant vegetation leachates, and to the microbially altered DOC from all vegetation leachates.

Alaska↗

Streamflow gains and losses in New Fork and Green Rivers, upstream from Fontenelle Reservoir, Wyoming, October 2015

The Wyoming Landscape Conservation Initiative is a program created to implement a long-term, science-based program of assessing natural resources while facilitating responsible energy and other development and does studies in much of southwestern Wyoming, including all or parts of Lincoln, Sublette, Fremont, Sweetwater, and Carbon Counties. A synoptic study was completed by the U.S. Geological Survey as part of ongoing contributions to the Wyoming Landscape Conservation Initiative to better understand the streamflow dynamics in the New Fork and Green Rivers in an area with historical, current, and future energy development. Streamflow measurements were collected October 19–22, 2015, at 19 sites on the New Fork and Green Rivers in Wyoming to determine changes in streamflow and, where applicable, describe the inflow and outflow of groundwater. Streamflow in the New Fork River generally increased from 50 cubic feet per second (ft 3 /s) at the most upstream site near Pinedale, Wyoming, to 350 ft 3 /s at the mouth of the river. Streamflow in the Green River generally increased downstream from 250 ft 3 /s at the most upstream site at Warren Bridge to around 800 ft 3 /s at the most downstream site near La Barge, Wyo., upstream from Fontenelle Reservoir. Estimated streamflow gains and losses were calculated for five reaches on the New Fork River. Four of the five reaches on the New Fork River had a change greater than the associated measurement error and were gaining reaches; the reach with the largest gain was the most upstream reach. One reach, the most downstream reach, had a calculated change in streamflow less than the associated measurement error. Estimated streamflow gains and losses were calculated for four reaches on the Green River. One reach was determined to be a gaining reach, one was a losing reach, and two reaches had changes less than the associated measurement error. Comparing the annual streamflow hydrographs for three long-term streamgages likely showed the effects of applying irrigation water to the upstream areas of land draining to the Green and New Fork Rivers. Streamflows in the New Fork River near Big Piney and the Green River near La Barge, Wyo., are sustained later in the season compared to the upstream site of Green River at Warren Bridge, which has few diversions and minimal irrigation.

Wyoming↗

Surface-water-quality data to support implementation of revised freshwater aluminum water-quality criteria in Massachusetts, 2018–19

The U.S. Geological Survey, in cooperation with the Massachusetts Department of Environmental Protection, performed a study to inform the development of the department’s guidelines for the collection and use of water-chemistry data to support calculation of site-dependent aluminum criteria values. The U.S. Geological Survey collected and analyzed discrete water-quality samples at four wastewater-treatment facilities and seven water-treatment facilities in eastern and central Massachusetts from April 2018 through May 2019. For each of the 11 facilities considered, water-quality samples were collected from treatment-plant effluent and receiving-water bodies. Samples were collected for laboratory analysis of major ions (calcium and magnesium ions are used to calculate total hardness), dissolved organic carbon (DOC), total organic carbon (TOC), and total recoverable aluminum. Field parameters for pH, temperature, and specific conductance were measured in situ concurrently with sample collection. Water-quality conditions differed among monitoring stations. The highest pH values were observed for stations on the Assabet River that receive effluent discharges from wastewater-treatment facilities (the Westborough, Marlborough, Hudson, and Maynard wastewater-treatment facilities). High DOC concentrations (greater than 10 mg/L) were measured in water bodies associated with large areas of riparian wetlands—Lily Pond (Cohasset) and Third Herring Brook (Hanover), and low DOC concentrations (less than 2.5 mg/L) were measured at three water bodies in central Massachusetts—Hocomonco Pond (Westborough), Wyman Pond (Fitchburg), and Monoosnoc Brook (Leominster). Wyman Pond (Fitchburg), Monoosnoc Brook (Leominster), and Lily Pond (Cohasset) also had low pH values and low total hardness concentrations. The monthly discrete pH, DOC, and total hardness data for selected stations on receiving-water bodies were used in the U.S. Environmental Protection Agency Aluminum Criteria Calculator Version 2.0 to estimate site-dependent total recoverable aluminum concentrations that—if not exceeded—would be expected to protect fish, invertebrates, and other aquatic life from adverse effects associated with acute and chronic aluminum exposures. The U.S. Environmental Protection Agency Calculator output provides values for the acute criterion, defined as the criterion maximum concentration (CMC), an estimate of the highest aluminum concentration in surface water to which an aquatic community can be exposed briefly without resulting in an unacceptable effect. This output also provides values for the chronic criterion, defined as the criterion continuous concentration (CCC), an estimate of the highest concentration of aluminum in surface water to which an aquatic community can be exposed indefinitely without resulting in an unacceptable effect. To determine aluminum criteria values typically evaluated for use as protective water-quality criteria, the monthly instantaneous CMC and CCC values were used to calculate the minimum, 5th percentile, and 10th percentile CMC and CCC values for selected monitoring stations. The monthly instantaneous aluminum CMC and CCC values generated using the EPA Calculator varied among stations. Aluminum CMC and CCC values were highest for four ambient (upstream) stations on the Assabet River associated with wastewater-treatment facilities (Westborough, Marlboro, Hudson, and Maynard). Aluminum CMC and CCC values were lower for stations associated with water-treatment facilities, and lowest for selected ambient stations on Lily Pond, Monoosnoc Brook, and Wyman Pond associated with water-treatment facilities in Cohasset, Leominster, and Fitchburg, respectively. For many stations, the highest CMC and CCC instantaneous aluminum criteria values generated using the U.S. Environmental Protection Agency Calculator were for months during the growing season for algae and aquatic macrophytes (April or May through September or October) and the lowest values were for months during the nongrowing season (October or November through March or April), indicating the importance of collecting water-quality data during the nongrowing season. Aluminum CMC and CCC values generated by the U.S. Environmental Protection Agency Calculator are sensitive to variations in the input parameters (pH, DOC, and total hardness). Aluminum solubility is particularly affected by pH. To characterize diel and seasonal variations in pH, multiparameter water-quality monitors recording continuous (15-minute interval) water temperature and pH were installed in the receiving-water body for one station near each facility upstream from the effluent discharge (in rivers) or at a station outside the immediate effect of effluent discharge (in ponds). Continuous water temperature and pH data were collected from April or May 2018 through November or December 2018. Continuous pH data indicated that the pond stations and Assabet River stations had large diel variations in pH during the growing season. Continuous pH data were used together with discrete DOC and total hardness data to evaluate the potential effect of diel variations in pH on calculated site-dependent aluminum criteria values. For the 11 stations, diel variations in pH were determined to correspond to differences in the 10th percentile of CMC values by a median of 160 μg/L, ranging from 0 to 610 μg/L, and differences in the 10th percentile of CCC values by a median of 40 μg/L, ranging from 15 to 210 μg/L. The low monthly instantaneous CMC and CCC values that have the greatest effect on the minimum, 5th percentile, and 10th percentile aluminum values tend to result during the nongrowing season (October or November through March or April) when the range of diel variations in pH is small, thus minimizing the effect of diel variations in pH on the lowest CMC and CCC values. Historical water-quality data on organic carbon in Massachusetts streams were investigated using data retrieved from the USGS National Water Information System database. An assessment of the availability of historical pH, DOC, and hardness data indicated that more data were available for TOC than for DOC. A linear regression equation was developed for the relation between DOC and TOC concentrations to inform the potential use of available data to evaluate water-quality conditions at additional sites across Massachusetts where only pH, hardness, and TOC data are available. DOC and TOC concentrations were well correlated in the 223 samples in which both constituents were analyzed, and the equation had a coefficient of determination ( R 2 ) equal to 0.93.

Massachusetts↗