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At least 307 records · Page 17Linked to original sources
USGS2015

Mercury and methylmercury in reservoirs in Indiana

Mercury (Hg) is an element that occurs naturally, but evidence suggests that human activities have resulted in increased amounts being released to the atmosphere and land surface. When Hg is converted to methylmercury (MeHg) in aquatic ecosystems, MeHg accumulates and increases in the food web so that some fish contain levels which pose a health risk to humans and wildlife that consume these fish. Reservoirs unlike natural lakes, are a part of river systems that are managed for flood control. Data compiled and interpreted for six flood-control reservoirs in Indiana showed a relation between Hg transport, MeHg formation in water, and MeHg in fish that was influenced by physical, chemical, and biological differences among the reservoirs. Existing information precludes a uniform comparison of Hg and MeHg in all reservoirs in the State, but factors and conditions were identified that can indicate where and when Hg and MeHg levels in reservoirs could be highest. As part of a statewide monitoring network for Hg and MeHg in Indiana streams, 66 water samples were collected from four reservoir tailwater sites (downstream near the dams) on a quarterly schedule for 5 years. The reservoirs were Brookville Lake, Cagles Mill Lake, J. Edward Roush Lake, and Mississinewa Lake. Particulate-bound Hg concentrations were significantly lower in tailwater samples than in samples from free-flowing streams in the statewide network. (Free-flowing streams were not affected by dams and were not upstream from these reservoirs.) These data indicated the reduced flow velocity of water upstream from dams was allowing particulate-bound Hg to settle out of the water in the reservoir pools. The concentration ratios of MeHg to Hg were significantly higher in the tailwater samples than in samples from free-flowing streams, and the MeHg to Hg ratios were significantly higher in summer than in other seasons. To evaluate the conditions related to MeHg formation, pools of three reservoirs (Brookville Lake, Monroe Lake, and Patoka Lake) were investigated during summer hydrologic conditions. Water temperature and dissolved oxygen were measured from the water surface to the lake bottom at 10 to 17 transects across each reservoir to identify three thermal strata, defined by water temperature, dissolved oxygen concentration, and depth. Depth-specific water samples were collected from these thermal strata throughout each reservoir, from the headwaters to the dam and from the tailwater. Mercury concentrations higher than 0.04 nanogram per liter (ng/L) were detected in all 53 samples, and MeHg concentrations higher than 0.04 ng/L were detected in 53 percent of the samples. The investigation found a zone of water below 8 or 9 meters, with temperatures less than 18 degrees Celsius and dissolved oxygen less than 3.5 milligrams per liter, extending through nearly half the reservoir area in Monroe Lake and Patoka Lake. This zone had abundant dissolved MeHg and concentration ratios of dissolved MeHg to Hg that ranged from 25 to 82 percent. This zone also had water with pH less than 7 and decreased dissolved sulfate, conditions indicating sulfate reduction by microorganisms that promoted a high potential for the conversion of Hg to MeHg. Reservoir outflow came from this zone at Monroe Lake and contributed to a tailwater concentration ratio for dissolved MeHg to Hg of 56 percent. Reservoir outflow at Patoka Lake was not from this zone, and dissolved MeHg was not detected in the tailwater. In contrast, samples from the summer pool at Brookville Lake had no MeHg detections even though Hg was detected, probably because the water pH higher than 7 inhibited sulfate reduction and did not promote the conversion of Hg to MeHg. Mercury and MeHg concentrations and the concentration ratios of MeHg to Hg in water varied among the six reservoirs in Indiana, and the differences were related to a combination of factors that could apply to other reservoirs. In areas with moderate to high rates of atmospheric Hg wet and dry deposition, Hg runoff and transport to streams and reservoirs was potentially highest for reservoirs with heavily forested watersheds in steep terrains of near-surface bedrock. Methylmercury concentrations and concentration ratios of MeHg to Hg were highest for reservoirs with the longest summer pools and highest inflow-to-outflow retention times, where water-chemistry conditions favoring sulfate reduction promoted conversion of Hg to MeHg. Methylmercury (reported as Hg) in fish-tissue samples collected for the State fish consumption advisory program was used to describe MeHg food-web accumulation and magnification in the reservoirs. The highest percentages of fish-tissue samples with Hg concentrations that exceeded the criterion of 0.30 milligram per kilogram for protection of human health were from Monroe Lake (38 percent) and Patoka Lake (33 percent). A review of the number and size of fish species caught from these two reservoirs resulted in two implications for fish consumption by humans. First, the highest numbers of fish harvested for potential human consumption were species more likely to have MeHg concentrations lower than the human-health criterion (crappie, bluegill, and catfish). Second, although largemouth bass were likely to have MeHg concentrations higher than the human-health criterion, they were caught and released more often than they were harvested. However, the average size largemouth bass (in both reservoirs) and above-average size walleye (in Monroe Lake) that were harvested for potential human consumption were likely to have MeHg concentrations higher than the human-health criterion.

Indiana↗
USGS2006

Testing the junk-food hypothesis on marine birds: Effects of prey type on growth and development

The junk-food hypothesis attributes declines in productivity of marine birds and mammals to changes in the species of prey they consume and corresponding differences in nutritional quality of those prey. To test this hypothesis nestling Black-legged Kittiwakes (Rissa tridactyla) and Tufted Puffins (Fratercula cirrhata) were raised in captivity under controlled conditions to determine whether the type and quality of fish consumed by young seabirds constrains their growth and development. Some nestlings were fed rations of Capelin (Mallotus villosus), Herring (Clupea pallasi) or Sand Lance (Ammodytes hexapterus) and their growth was compared with nestlings raised on equal biomass rations of Walleye Pollock (Theragra chalcograma). Nestlings fed rations of herring, sand lance, or capelin experienced higher growth increments than nestlings fed pollock. The energy density of forage fish fed to nestlings had a marked effect on growth increments and could be expected to have an effect on pre- and post-fledging survival of nestlings in the wild. These results provide empirical support for the junk-food hypothesis.

Waterbirds↗
USGS1963

Insecticides: effects on cutthroat trout of repeated exposure to DDT

Cutthroat trout were periodically exposed to p, pp-DDT, in acetone solution or in the food. Excessive mortality occurred only in lots treated with high concentrations of DDT, probably as a result of decreased resistance to nonspecific stressors. Surviving fish in these lots were significantly larger than those in the control lot, or in the lots treated with low concentrations of DDT. The number and volume of eggs produced was not reduced by DDT, but mortality among sac fry appeared to be highest in the lots treated with high concentrations. The data suggest that the sublethal concentrations of DDT ordinarily encountered in the environment are unlikely to damage a fishery.

Science↗
USGS1982

Changes in vegetation structure in seeded nesting cover in the prairie pothole region

A sample of 365 stands of seeded nesting cover (mixtures of cool-season grasses and legumes) was studied in the glaciated prairie pothole region during 1977-79. Measurements of species composition, canopy cover, plant height, and visual obstruction values differed with stand age but only in a general way when results from over the entire region were pooled. Maximum values for plant height and visual obstruction occurred once per stand during the first 10 growing seasons. Although the year of maximum growth was variable and unpredictable, stands showed trends of degeneration in height and visual obstruction after the year of maximum growth.Seeded nesting cover grew similarly throughout the region when on soils of capability class IV or better and within a precipitation range of 30 to 61 cm. Precipitation was the factor that most affected stand growth, especially the amount received in the year before spring measurements. Height and visual obstruction values within a stand were also directly affected by some individual species and by the percentage of grass within a stand. In 2 of the 3 study years, the height and visual obstruction values of residual cover were extremely reduced by ice pack, heavy snow pack, or a combination of snow pack and harvest by rodents. Such events, if frequent, largely negate the possibility of using minimum visual obstruction or plant height measurements for assessing quality of vegetation for wildlife cover and management purposes.Species composition, number of species, and canopy cover varied most during the first three growing seasons and least during the next six. Succession toward dominance by native grasses and forbs and woody species was retarded by the predominance of the species of seeded nesting cover, at least during the first 10 growing seasons.All stands had at least one species present that was either a noxious weed, a problem cropland weed, or a nuisance weed. Weeds were usually local in distribution. Five weed species needing special management attention on public lands are leafy spurge (Euphorbia podperae), wormwood (Artemisia absinthium), Canada thistle (Cirsium arvense), musk thistle (Carduus nutans), and plumeless thistle (Carduus acanthoides). Sites disturbed by mammal diggings or those skipped during planting operations became revegetated mostly with species other than those of seeded nesting cover.Successfully established stands on good sites provided substantial food and cover for wildlife for at least 6 years and retained stand composition for at least 10 years. Further study will be necessary to determine longevity of these stands. Except for mandatory noxious weed control, no management treatments of seeded nesting cover were necessary before the seventh growing season, at which time some stands needed renovation. The primary goals for management of seeded nesting cover should be stand quality and longevity. Guidelines to these goals are suggested.

Special Scientific Report - Wildlife↗
USGS1998

Proactive responses to human impacts that balance development and Atlantic salmon (Salmo salar) conservation: An integrative model

Incorporating human impacts into conservation plans is critical to protect natural resources. Using a model that examines how anthropogenic changes might be proactively influenced to promote conservation, we argue that a denser human population does not spell inevitable doom for Atlantic salmon (Salmo salar). Humans affect the Atlantic salmon ecosystem deleteriously through landscape alteration, exploitation, external inputs, and resource competition. An intact ecosystem provides positive feedback to society by providing food, ecosystem services, and improving the quality of life. As Atlantic salmon and associated ecosystem benefits are increasingly valued by society, policies, laws, and regulations that protect salmon populations and habitats are codified into a 'control system' or institutional infrastructure. Via research that helps maintain wild salmon populations and in informing the public about the benefits of a healthy Atlantic salmon ecosystem, scientists can influence public attitudes and facilitate the implementation of environmental policies that moderate harmful anthropogenic changes. Because exchange among scientists is of paramount importance in increasing our understanding of important interrelationships between humans and fish, we recommend the establishment of an international salmon organizational for research.

Conference Paper↗
USGS1992

Interactive effects of arsenate, selenium, and dietary protein on survival, growth, and physiology in mallard ducklings

High concentrations of arsenic (As) and selenium (Se) have been found in aquatic food chains associated with irrigation drainwater. Total biomass of invertebrates, a maJor source of protein for wild ducklings, may vary in environments that are contaminated with selenium. Dayold mallard (Anas platyrhynchos) ducklings received an untreated diet (controls) containing 22% protein or diets containing 15 ppm Se (as selenomethionine), 60 ppm Se, 200 ppm As (as sodium arsenate), 15 ppm Se with 200 ppm As, or 60 ppm Se with 200 ppm As. In a concurrent experiment, the same sequence was repeated with a proteinrestricted (7%) but isocaloric diet. After 4 weeks, blood and tissue samples were collected for biochemical and histological examination. With 22% protein and 60 ppm Se in the diet, duckling survival and growth was reduced and livers had histopathological lesions. Arsenic alone caused some reduction in growth. Antagonistic interactive effects occurred between As and Se, including complete to partial alleviation of the following Se effects: mortality, impaired growth, hepatic lesions and lipid peroxidation, and altered glutathione and thiol status. With 7% protein, survival and growth of controls was less than that with 22% protein, Se (60 ppm) caused 100% mortality, and As (200 ppm) caused mortality, decreased growth, and liver histopathology. These findings suggest the potential for antagonistic effects of Se and As on duckling survival, growth, and physiology with adequate dietary protein but more severe toxicological effects when dietary protein is diminished.

Archives of Environmental Contamination and Toxico↗
USGS2007

Environmental and plant community determinants of species loss following nitrogen enrichment

Global energy use and food production have increased nitrogen inputs to ecosystems worldwide, impacting plant community diversity, composition, and function. Previous studies show considerable variation across terrestrial herbaceous ecosystems in the magnitude of species loss following nitrogen (N) enrichment. What controls this variation remains unknown. We present results from 23 N-addition experiments across North America, representing a range of climatic, soil and plant community properties, to determine conditions that lead to greater diversity decline. Species loss in these communities ranged from 0 to 65% of control richness. Using hierarchical structural equation modelling, we found greater species loss in communities with a lower soil cation exchange capacity, colder regional temperature, and larger production increase following N addition, independent of initial species richness, plant productivity, and the relative abundance of most plant functional groups. Our results indicate sensitivity to N addition is co-determined by environmental conditions and production responsiveness, which overwhelm the effects of initial community structure and composition. ?? 2007 Blackwell Publishing Ltd/CNRS.

Ecology Letters↗
USGS2024

Low rate of population establishment of a freshwater invertebrate (Gammarus lacustris) in experimental conservation translocations

Conservation translocations may be a useful tool for the restoration of declining freshwater invertebrates, but they are poorly represented in the literature. We conducted a before-after/control-impact (BACI) experiment to test the efficacy of conservation translocation for re-establishing abundant populations of the amphipod Gammarus lacustris , a declining species and wildlife food resource in depressional wetlands in the upper Midwest of the United States of America. Each study site ( n = 19) contained at least one treatment wetland receiving translocated G. lacustris from a local donor and one control wetland. We selected study wetlands based on a suite of wetland characteristics and randomly assigned recipient versus control treatment. Gammarus lacustris was detected post-translocation at only 2 of 22 recipient wetlands (1 of 19 sites). Overall, there was a statistical increase in G. lacustris density in recipient wetlands compared to controls; however, the results were of minimal biological significance due to being driven by a single site with low G. lacustris densities. Accordingly, our results suggest that future conservation translocations of amphipods might be successful if limited to recently restored wetlands or informed by a more complex habitat suitability model to differentiate dispersal limitations from habitat limitations. To develop such a model would involve identifying the fewest, most influential physical and biological factors (e.g. wetland size/structure, fish, aquatic vegetation, and water chemistry) from the numerous inter-related factors that correlate with the abundance of naturally occurring G. lacustris ; candidate wetlands to receive amphipods would be those for which the model predicts abundant G. lacustris but in which they do not presently occur.

Minnesota↗
USGS1970

Soil-food chain-pesticide wildlife relationships in aldrin-treated fields

Soil-food-chain-pesticide wildlife relationships were investigated to learn the concentration of pesticide residues present in soils, macro-invertebrates, vertebrates, and seeds as a result of annual applications of aldrin at recommended rates for pest control. Two central Missouri cornfields treated with aldrin at 1 lb/acre, for 16 and 15 of the past 17 years, were selected for study during 1965-67. Primary samples collected for residue analyses included soils, earthworms (Lumbricidae), crickets (Gryllidae), and two kinds of ground beetles (Carabidae) obtained during early April, June, August, and October. Vertebrates and plant seeds collected during 1967 included white-footed mice ( Peromyscus maniculatus ), toads ( Bufo americanus ), snakes ( Thamnophis sirtalis and Pituophis sayi ), corn ( Zea Mays ), foxtail ( Setaria Faberii ), and annual sunflower ( Helianthus annuus ). Pesticide residues consisted primarily of dieldrin, the degradation product of aldrin. Combined aldrin and dieldrin residues, as two field all-season averages, wet weight basis, were: soils, 0.31 ppm; earthworms, 1.49 ppm; crickets, 0.23 ppm; Harpalus ground beetles, 1.10 ppm; Poecilus ground beetles, 9.67 ppm; white-footed mice, 0.98 ppm; toads, 3.53 ppm; garter snakes, 12.35 ppm; and corn, foxtail, and sunflower seeds less than 0.02 ppm each. Unusually high average residues (37.48 ppm) in Poecilus beetles during June, 1967, were attributed to abnormally high soil moisture and predacious feeding habits of these insects.

Missouri↗
USGS2012

Flow-adjusted trends in dissolved selenium load and concentration in the Gunnison and Colorado Rivers near Grand Junction, Colorado, water years 1986--2008

As a result of elevated selenium concentrations, many western Colorado rivers and streams are on the U.S. Environmental Protection Agency 2010 Colorado 303(d) list, including the main stem of the Colorado River from the Gunnison River confluence to the Utah border. Selenium is a trace metal that bioaccumulates in aquatic food chains and can cause reproductive failure, deformities, and other adverse impacts in birds and fish, including several threatened and endangered fish species. Salinity in the upper Colorado River has been the focus of source-control efforts for many years. Although salinity loads and concentrations have been previously characterized at the U.S. Geological Survey (USGS) streamflow-gaging stations at the Gunnison River near Grand Junction, Colo., and at the Colorado River near the Colorado-Utah State line, trends in selenium load and concentration at these two stations have not been studied. The USGS, in cooperation with the Bureau of Reclamation and the Colorado River Water Conservation District, evaluated dissolved selenium (herein referred to as "selenium") load and concentration trends at these two sites to inform decision makers on the status and trends of selenium. This report presents results of the evaluation of trends in selenium load and concentration for two USGS streamflow-gaging stations: the Gunnison River near Grand Junction, Colo. ("Gunnison River site"), USGS site 09152500, and the Colorado River near Colorado-Utah State line ("Colorado River site"), USGS site 09163500. Flow-adjusted selenium loads were estimated for the beginning water year (WY) of the study, 1986, and the ending WY of the study, 2008. The difference between flow-adjusted selenium loads for WY 1986 and WY 2008 was selected as the method of analysis because flow adjustment removes the natural variations in load caused by changes in mean-daily streamflow, emphasizing human-caused changes in selenium load and concentration. Overall changes in human-caused effects in selenium loads and concentrations during the period of study are of primary interest to the cooperators. Selenium loads for each of the 2 water years were calculated by using normalized mean-daily streamflow, measured selenium concentration, standard linear regression techniques, and data previously collected at the two study sites. Mean-daily streamflow was normalized for each site by averaging the daily streamflow for each day of the year over the 23-year period of record. Thus, for the beginning and ending water years, estimations could be made of loads that would have occurred without the effect of year-to-year streamflow variation. The loads thus calculated are illustrative of the change in loads between water years 1986 and 2008, and are not the actual loads that occurred in those 2 water years. The estimated 50th and 85th percentile selenium concentrations associated with the selenium loads were also calculated for WY 1986 and WY 2008 at each site. Time-trends in selenium concentration at the two sites were charted by using regression techniques for partial residuals for the entire study period (WY 1986 through WY 2008). Annual selenium load for the Gunnison River site was estimated to be 23,196 pounds for WY 1986 and 16,560 pounds for WY 2008, a 28.6 percent decrease. Lower and upper 95-percent confidence levels for WY 1986 annual load were 22,360 and 24,032 pounds. Lower and upper 95-percent confidence levels for WY 2008 annual load were 15,724 and 17,396 pounds. Estimated 50th percentile daily selenium concentrations decreased from 6.41 to 4.57 micrograms/liter from WY 1986 to WY 2008, whereas estimated 85th percentile daily selenium concentrations decreased from 7.21 to 5.13 micrograms/liter from WY 1986 to WY 2008. Annual selenium load for the Colorado River site was estimated to be 56,587 pounds for WY 1986 and 34,344 pounds for WY 2008, a 39.3 percent decrease. Lower and upper 95-percent confidence levels for WY 1986 annual load were 53,785 and 59,390 pounds. Lower and upper 95-percent confidence levels for WY 2008 annual load were 31,542 and 37,147 pounds. Estimated 50th percentile daily selenium concentrations decreased from 6.44 to 3.86 micrograms/liter from WY 1986 to WY 2008, whereas estimated 85th percentile daily selenium concentrations decreased from 7.94 to 4.72 micrograms/liter from WY 1986 to WY 2008.

Colorado↗
USGS2000

Tracking the spring migration of a bar-headed goose ( Anser indicus ) across the Himalaya with satellite telemetry

Soil-food-chain-pesticide wildlife relationships were investigated to learn the concentration of pesticide residues present in soils, macro-invertebrates, vertebrates, and seeds as a result of annual applications of aldrin at recommended rates for pest control. Two central Missouri cornfields treated witb aldrin at 1 lb/acre, for 16 and 15 of the past 17 years, were selected for study during 1965-67. Primary samples collected for residue analyses included soils, earthworms (Lumbricidae), crickets (GryIlidae), and two kinds of ground beetles (Carabidae) obtained during early April, June, August, and October. Vertebrates and plant seeds collected during 1967 included white-footed mice (Peromyscus maniculatus), toads (Bufo americanus), snakes (Thamnophis sirtalis and Pituophis sayi), corn (Zea Mays), foxtail (Setaria Faberii), and annual sunflower (Helianthus annuus). Pesticide residues consisted primarily of dieldrin, the degradation product of aldrin. Combined aldrin and dieldrin residues, as two field all-season averages, wet weight basis, were: soils, 0.31 ppm; earthworms, 1.49 ppm; crickets, 0.23 ppm; Harpalus ground beetles, 1.10 ppm; Poecilus ground beetles, 9.67 ppm; white-footed mice, 0.98 ppm; toads, 3.53 ppm; garter snakes, 12.35 ppm; and corn, foxtail, and sunflower seeds less than 0.02 ppm each. Unusually high average residues (37.48 ppm) in Poecilus beetles during June, 1967, were attributed to abnormally high soil moisture and predacious feeding habits of these insects.

Global Environmental Research↗
USGS2003

Effects of structural marsh management and salinity on invertebrate prey of waterbirds in marsh ponds during winter on the Gulf Coast Chenier Plain

Aquatic invertebrates are important food resources for wintering waterbirds, and prey selection generally is limited by prey size. Aquatic invertebrate communities are influenced by sediments and hydrologic characteristics of wetlands, which were affected by structural marsh management (levees, water-control structures and impoundments; SMM) and salinity on the Gulf Coast Chenier Plain of North America. Based on previous research, we tested general predictions that SMM reduces biomass of infaunal invertebrates and increases that of epifaunal invertebrates and those that tolerate low levels of dissolved oxygen (O2) and salinity. We also tested the general prediction that invertebrate biomass in freshwater, oligohaline, and mesohaline marshes are similar, except for taxa adapted to specific ranges of salinity. Finally, we investigated relationships among invertebrate biomass and sizes, sediment and hydrologic variables, and marsh types. Accordingly, we measured biomass of common invertebrate by three size classes (63 to 199 ??m, 200 to 999 ??m, and ???1000 ??m), sediment variables (carbon content, C:N ratio, hardness, particle size, and O, penetration), and hydrologic variables (salinity, water depth,temperature, 02, and turbidity) in ponds of impounded freshwater (IF), oligohaline (IO), mesohaline (IM), and unimpounded mesohaline (UM) marshes during winters 1997-1998 to 1999-2000 on Rockefeller State Wildlife Refuge, near Grand Chenier, Louisiana, USA. As predicted, an a priori multivariate analysis of variance (MANOVA) contrast indicated that biomass of an infaunal class of invertebrates (Nematoda, 63 to 199 ??m) was greater in UM marsh ponds than in those of IM marshes, and biomass of an epifaunal class of invertebrates (Ostracoda, 200 to 999 ??m) was greater in IM marsh ponds than in those of UM marshes. The observed reduction in Nematoda due to SMM also was consistent with the prediction that SMM reduces invertebrates that do not tolerate low salinity. Furthermore, as predicted, an a priori MANOVA contrast indicated that biomass of a single invertebrate class adapted to low salinity (Oligochaeta, 200 to 999 ??m) was greater in ponds of IF marshes than in those of IO and IM marshes. A canonical correspondence analysis indicated that variation in salinity and O2 penetration best explained differences among sites that maximized biomass of the common invertebrate classes. Salinity was positively correlated with the silt-clay fraction, O2, and O2 penetration, and negatively correlated with water depth, sediment hardness, carbon, and C:N. Nematoda, Foraminifera, and Copepoda generally were associated with UM marsh ponds and high salinity, whereas other invertebrate classes were distributed among impounded marsh ponds and associated with lower salinity. Our results suggest that SMM and salinity have relatively small effects on invertebrate prey of wintering waterbirds in marsh ponds because they affect biomass of Nematoda and Oligochaeta, and few waterbirds consume these invertebrates. ?? 2003, The Society of Wetland Scientists.

Wetlands↗
USGS2019

Skin and fin diseases

Fish are critically important to the welfare of this planet and its occupants, the health of both wild and captive fish populations paramount to our survival. This book presents the gross pathology of the most commonly encountered diseases and syndromes of fish in an organ system-based approach. It provides an overview of the diseases and disorders of tropical, ornamental, bait and food fish from freshwater, brackish and marine environments. Readers will gain a broader understanding of the basic biology of infectious and non-infectious diseases in fish, as well as novel diagnostic techniques and innovative disease control methods.

Book chapter↗
USGS2001

Time series of suspended-solids concentration, salinity, temperature, and total mercury concentration in San Francisco Bay during water year 1998

Many physical processes affect how constituents within San Francisco Bay vary. Processes and their associated time scales include turbulence (seconds), semidiurnal and diurnal tides (hours), the spring-neap tidal cycle (days), freshwater flow (weeks), seasonal winds (months), ecological and climatic changes (years), and geologic changes (thousands of years). Continuous time series of data on basic state variables of the bay, such as suspended-solids concentration (SSC), salinity, and water temperature, provide insight on the effect and relative importance of physical processes on the bay. SSC time series and Regional Monitoring Program (RMP) water-quality data can be used to calculate time series of some traceelement concentrations (Schoellhamer, 1997a, 1997b). The purpose of this chapter is to describe qualitatively time series of SSC, salinity, water temperature, and mercury during water year 1998 (October 1997 through September 1998). Salinity, temperature, and sediment are important components of the San Francisco Bay estuarine system. Salinity and temperature affect the hydrodynamics (Monismith et al., 1996; Schoellhamer and Burau, 1998), geochemistry (Kuwabara et al., 1989), and ecology (Cloern, 1984; Nichols et al., 1986; Jassby et al., 1995) of the bay. Suspended sediments limit light availability in the bay, which, in turn, limits primary production (Cloern, 1987; Cole and Cloern, 1987), and thus food for higher trophic levels. Sediments deposit in ports and shipping channels, which must be dredged to maintain navigation (U.S. Environmental Protection Agency, 1992). Potentially toxic substances, such as metals and pesticides, adsorb to sediment particles (Kuwabara et al., 1989; Domagalski and Kuivila, 1993; Flegal et al., 1996; Schoellhamer, 1997a, 1997b). The transport and fate of suspended sediments are important factors in determining the transport and fate of constituents adsorbed on the sediments. For example, the concentration of suspended particulate chromium in the bay appears to be controlled primarily by sediment resuspension (Abu-Saba and Flegal, 1995). Concentrations of dissolved trace elements are greater in South Bay than elsewhere in San Francisco Bay, and bottom sediments are believed to be a significant source (Flegal et al., 1991). The sediments on the bay bottom provide habitat for benthic communities that can ingest these substances and introduce them into the food web (Luoma et al., 1985; Brown and Luoma, 1995, Luoma 1996). Bottom sediments also are a reservoir of nutrients that contribute to the maintenance of estuarine productivity (Hammond et al., 1985).

California↗
USGS2020

Spatial variability of phytoplankton in a shallow tidal freshwater system reveals complex controls on abundance and community structure

Estuaries worldwide are undergoing changes to patterns of aquatic productivity because of human activities that alter flow, impact sediment delivery and thus the light field, and contribute nutrients and contaminants like pesticides and metals. These changes can influence phytoplankton communities, which in turn can alter estuarine food webs. We used multiple approaches-including high-resolution water quality mapping, synoptic sampling, productivity and nitrogen uptake rates, Lagrangian parcel tracking, enclosure experiments and bottle incubations-over a short time period to take a “spatial snapshot” of conditions in the northern region of the San Francisco Estuary (California, USA) to examine how environmental drivers like light availability, nutrients, water residence time, and contaminants affect phytoplankton abundance and community attributes like size distribution, taxonomic structure, and nutrient uptake rates. Zones characterized by longer residence time (15–60 days) had higher chlorophyll-a concentrations (9 ± 4 µg L −1 ) and were comprised primarily of small phytoplankton cells (<5 µm, 74 ± 8%), lower ammonium concentrations (1 ± 0.8 µM), higher nitrate uptake rates, and higher rates of potential carbon productivity. Conversely, zones characterized by shorter residence time (1–14 days) had higher ammonium concentration (13 ± 5 µM) and lower chlorophyll-a concentration (5 ± 1 µg L −1 ) with diatoms making up a larger percent contribution. Longer residence time, however, did not result in the accumulation of large (>5 µm) cells considered important to pelagic food webs. Rather, longer residence time zones had a phytoplankton community comprised primarily of small cells, particularly picocyanobacteria that made up 38 ± 17% of the chlorophyll-a – nearly double the concentration seen in shorter residence time zones (22 ± 7% picocyanobacterial of chlorophyll-a). Our results suggest that water residence time in estuaries may have an effect as large or larger than that experimentally demonstrated for light, contaminants, or nutrients.

California↗
USGS2003

Lake Ontario: Food web dynamics in a changing ecosystem (1970-2000)

We examined stressors that have led to profound ecological changes in the Lake Ontario ecosystem and its fish community since 1970. The most notable changes have been reductions in phosphorus loading, invasion by Dreissena spp., fisheries management through stocking of exotic salmonids and control of sea lamprey ( Petromyzon marinus ), and fish harvest by anglers and double-crested cormorants ( Phalacrocorax auritus ). The response to these stressors has led to ( i ) declines in both algal photosynthesis and epilimnetic zooplankton production, ( ii ) decreases in alewife ( Alosa pseudoharengus ) abundance, ( iii ) declines in native Diporeia and lake whitefish ( Coregonus clupeaformis ), ( iv ) behavioral shifts in alewife spatial distribution benefitting native lake trout ( Salvelinus namaycush ), threespine stickleback ( Gasterosteus aculeatus ), and emerald shiner ( Notropis atherinoides ) populations, ( v ) dramatic increases in water clarity, ( vi ) predation impacts by cormorants on select fish species, and ( vii ) lake trout recruitment bottlenecks associated with alewife-induced thiamine deficiency. We expect stressor responses associated with anthropogenic forces like exotic species invasions and global climate warming to continue to impact the Lake Ontario ecosystem in the future and recommend continuous long-term ecological studies to enhance scientific understanding and management of this important resource.

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS1949

Dosage of sulfamerazine in the treatment of furunculosis in brook trout, Salvelinus fontinalis

To determine the most effective dosage of sulfamerazine in the treatment of furunculosis in brook trout, two experiments were run. In the first experiment, yearlings were used and the daily dosage rates were 4, 8, and 12 grams of sulfamerazine per 100 pounds of fish. In the lots treated with sulfamerazine, mortality was brought under control within 15 days and was less than a quarter as high as in the controls. Results with the 4‐gram rate were nearly as good as with the higher rates. Treatment was continued for 10 days or more after mortality dropped to zero, and recurrences were few. A large number of the dead were checked bacteriologically for furunculosis. In the second experiment fingerlings in an early stage of a furunculosis epizootic were used and the daily dosage rates were 2, 4 and 6 grams per 100 pounds of fish. Losses in the controls were extremely heavy, with only 6‐percent survival. Losses were heavy in all lots, but in those treated at the 4‐gram and 6‐gram rates, survival was 10 times as high as in the controls. Mortality declined sooner with the 6‐gram than with the 4‐gram rate, and recurrence was almost eliminated by treatment, at the higher rate, for 10 days after mortality dropped to zero. Discontinuance of treatment as late as 4 days after the discontinuance of mortality was followed by resumption of mortality at a considerable rate. In the treated lots, late dead were small thin fish which evidently had received little food and drug. Dead fish were “spot‐checked” for furunculosis. The recommended daily dosage rate is 6 grams per 100 pounds of fish, to be continued for 10 days after mortality stops and for a total of at least 3 weeks. Other recommendations include: the early elimination of undersized fish; the prompt removal of dead and dying fish; the maintenance of clean troughs and pools; and strict observation of all sanitary measures practiced in the control of infectious diseases.

Transactions of the American Fisheries Society↗
USGS1961

Use of 3-trifluormethyl-4-nitrophenol as a selective sea lamprey larvicide

The recent discovery of a group of chemical compounds that are significantly more toxic to sea lampreys than to other aquatic organisms offers promise of an early and effective control of this pest. The sea lamprey has all but destroyed the lake trout populations of Lakes Huron and Michigan. In Lake Superior, production of the lake trout fishery has declined to record low levels. Only a rapid and drastic reduction in sea lamprey predation can save the lake trout population there. Other species of food and game fishes have suffered severe decreases from persistent attack by the lamprey. The sea lamprey spends only a small portion of its life as a parasite in the Great Lakes. The fully grown and sexually mature adults migrate into streams to spawn and thereafter die. The eggs hatch in a week to 10 days and the larvae remain in the stream bottom for 5 years or longer before metamorphosis into the adult form. Following this transformation the young lampreys migrate downstream to the lakes to begin their parasitic existence. The life cycle of the sea lamprey has been described in detail elsewhere (Applegate 1950; Applegate and Moffett 1955). Control of the adult lampreys distributed throughout a body of open water as large as one of the Great Lakes, by known and available techniques, is not feasible. Fortunately, this pest can be attacked effectively at those stages in its life cycle when it is concentrated in restricted areas. Various devices have been developed which prevent spawning by blocking the streams below the spawning grounds. Electrical weirs, that repel or destroy the lampreys, have been used (Applegate, Smith, and Nielsen 1952; Erkkila, Smith, and McLain 1956). A serious shortcoming of this control method is the time required to achieve the desired effect. Even though the adults have been destroyed before spawning, 5 or more generations of larval lampreys are already in the stream-enough to provide an annual supply of parasitic adults for an equal period of time. Almost all the larvae of the sea lamprey live in the spawning streams. Treatment of these streams with selectively toxic chemicals that kill the larvae provides immediate reduction of all generations in the population before they become parasites. Control of the species can thus be achieved without a delay of several years.

Technical Report↗