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USGS2014

Near-field receiving water monitoring of trace metals and a benthic community near the Palo Alto Regional Water Quality Control Plant in South San Francisco Bay, California: 2013

Trace-metal concentrations in sediment and in the clam Macoma petalum (formerly reported as Macoma balthica ), clam reproductive activity, and benthic macroinvertebrate community structure were investigated in a mudflat 1 kilometer south of the discharge of the Palo Alto Regional Water Quality Control Plant (PARWQCP) in South San Francisco Bay, Calif. This report includes the data collected by U.S. Geological Survey (USGS) scientists for the period January 2013 to December 2013. These data serve as the basis for the City of Palo Alto’s Near-Field Receiving Water Monitoring Program, initiated in 1994. Following significant reductions in the late 1980s, silver (Ag) and copper (Cu) concentrations in sediment and M. petalum appear to have stabilized. Data for other metals, including chromium (Cr), mercury (Hg), nickel (Ni), selenium (Se), and zinc (Zn), have been collected since 1994. Over this period, concentrations of these elements have remained relatively constant, aside from seasonal variation that is common to all elements. In 2013, concentrations of Ag and Cu in M. petalum varied seasonally in response to a combination of site-specific metal exposures and annual growth and reproduction, as reported previously. Seasonal patterns for other elements, including Cr, Ni, Zn, Hg, and Se, were generally similar in timing and magnitude as those for Ag and Cu. In M. petalum , all observed elements showed annual maxima in January–February and minima in April, except for Zn, which was lowest in December. In sediments, annual maxima also occurred in January–February, and minima were measured in June and September. In 2013, metal concentrations in both sediments and clam tissue were among the lowest concentrations on record. This record suggests that regional-scale factors now largely control sedimentary and bioavailable concentrations of Ag and Cu, as well as other elements of regulatory interest, at the Palo Alto site. Analyses of the benthic community structure of a mudflat in South San Francisco Bay over a 40-year period show that changes in the community have occurred concurrent with reduced concentrations of metals in the sediment and in the tissues of the biosentinel clam, M. petalum , from the same area. Analysis of the M. petalum community shows increases in reproductive activity concurrent with the decline in metal concentrations in the tissues of this organism. Reproductive activity is presently stable (2013), with almost all animals initiating reproduction in the fall and spawning the following spring. The community has shifted from being dominated by several opportunistic species to a community where the species are more similar in abundance, a pattern that indicates a more stable community that is subjected to fewer stressors. In addition, two of the opportunistic species ( Ampelisca abdita and Streblospio benedicti ) that brood their young and live on the surface of the sediment in tubes have shown a continual decline in dominance coincident with the decline in metals; both species had short-lived rebounds in abundance in 2008, 2009, and 2010. Heteromastus filiformis (a subsurface polychaete worm that lives in the sediment, consumes sediment and organic particles residing in the sediment, and reproduces by laying its eggs on or in the sediment) showed a concurrent increase in dominance and, in the last several years before 2008, showed a stable population. H. filiformis abundance increased slightly in 2011–2012 and returned to pre-2011 numbers in 2013. An unidentified disturbance occurred on the mudflat in early 2008 that resulted in the loss of the benthic animals, except for those deep-dwelling animals like Macoma petalum . Animals immediately returned to the mudflat in 2008, which was the first indication that the disturbance was not due to a persistent toxin or to anoxia. The reproductive mode of most species present in 2013 is reflective of the species that were available either as pelagic larvae or as mobile adults. Although oviparous species were lower in number in this group, the authors hypothesize that these species will return slowly as more species move back into the area. The use of functional ecology was highlighted in the 2013 benthic community data, which show that the animals that have now returned to the mudflat are those that can respond successfully to a physical, nontoxic disturbance. Today, community data show a mix of animals that consume the sediment, filter feed, have pelagic larvae that must survive landing on the sediment, and brood their young. USGS scientists continue to observe the community’s response to the 2008 defaunation event because it allows them to examine the response of the community to a natural disturbance (possible causes include sediment accretion or freshwater inundation) and compare this recovery to the long-term recovery observed in the 1970s when the decline in sediment pollutants was the dominating factor.

California↗

USGS2015

Occurrence and distribution of fecal indicator bacteria and gene markers of pathogenic bacteria in Great Lakes tributaries, March-October 2011

From March through October 2011, the U.S. Geological Survey (USGS), conducted a study to determine the frequency of occurrence of pathogen gene markers and densities of fecal indicator bacteria (FIB) in 22 tributaries to the Great Lakes. This project was funded as part of the Great Lakes Restoration Initiative (GLRI) and included sampling at 22 locations throughout 6 states that border the Great Lakes. A total of 177 environmental samples were collected at USGS streamgaging stations during both normal-flow and high-flow conditions and were analyzed by the Michigan Bacteriological Research Laboratory at the USGS Water Science Center in Lansing, Michigan. Water samples were analyzed for the presence of FIB concentrations (FIB; fecal coliform bacteria, Escherichia coli [ E. coli ], and enterococci) by using membrane filtration and serial dilution methods. The resulting enrichments from standard culturing of the samples were then analyzed by using polymerase chain reaction (PCR) to determine the occurrence of pathogen gene markers for Shigella species, Campylobacter jejuni and coli , Salmonella species, and pathogenic E. coli , including Shiga toxin-producing E. coli (STEC).

Great Lakes↗

USGS2015

Near-field receiving water monitoring of trace metals and a benthic community near the Palo Alto Regional Water Quality Control Plant in south San Francisco Bay, California: 2014

Trace-metal concentrations in sediment and in the clam Macoma petalum (formerly reported as Macoma balthica ), clam reproductive activity, and benthic macroinvertebrate community structure were investigated in a mudflat 1 kilometer (km) south of the discharge of the Palo Alto Regional Water Quality Control Plant (PARWQCP) in South San Francisco Bay, Calif. This report includes the data collected by U.S. Geological Survey (USGS) scientists for the period January 2014 to December 2014. These append to long-term datasets extending back to 1974, and serve as the basis for the City of Palo Alto’s Near-Field Receiving Water Monitoring Program, initiated in 1994. Following significant reductions in the late 1980s, silver (Ag) and copper (Cu) concentrations in sediment and M. petalum appear to have stabilized. Data for other metals, including chromium (Cr), mercury (Hg), nickel (Ni), selenium (Se), and zinc (Zn), have been collected since 1994. Over this period, concentrations of these elements have remained relatively constant, aside from seasonal variation that is common to all elements. In 2014, concentrations of Ag and Cu in M. petalum varied seasonally in response to a combination of site-specific metal exposures and annual growth and reproduction, as reported previously. Seasonal patterns for other elements, including Cr, Ni, Zn, Hg, and Se, were generally similar in timing and magnitude as those for Ag and Cu. In M. petalum , all observed elements showed annual maxima in January–February and minima in April, except for Zn, which was lowest in December. In sediments, annual maxima also occurred in January–February, and minima were measured in June and September. In 2014, metal concentrations in both sediments and clam tissue were among the lowest on record. This record suggests that regional-scale factors now largely control sedimentary and bioavailable concentrations of Ag and Cu, as well as other elements of regulatory interest, at the Palo Alto site. Analyses of the benthic community structure of a mudflat in South San Francisco Bay over a 40-year period show that changes in the community have occurred concurrent with reduced concentrations of metals in the sediment and in the tissues of the biosentinel clam, M. petalum , from the same area. Analysis of M. petalum shows increases in reproductive activity concurrent with the decline in metal concentrations in the tissues of this organism. Reproductive activity is presently stable (2014), with almost all animals initiating reproduction in the fall and spawning the following spring. The entire infaunal community has shifted from being dominated by several opportunistic species to a community where the species are more similar in abundance, a pattern that indicates a more stable community that is subjected to fewer stressors. In addition, two of the opportunistic species ( Ampelisca abdita and Streblospio benedicti ) that brood their young and live on the surface of the sediment in tubes have shown a continual decline in dominance coincident with the decline in metals; both species had short-lived rebounds in abundance in 2008, 2009, and 2010. Heteromastus filiformis (a subsurface polychaete worm that lives in the sediment, consumes sediment and organic particles residing in the sediment, and reproduces by laying its eggs on or in the sediment) showed a concurrent increase in dominance and, in the last several years before 2008, showed a stable population. H. filiformis abundance increased slightly in 2011–2012 and returned to pre-2011 numbers in 2014. An unidentified disturbance occurred on the mudflat in early 2008 that resulted in the loss of the benthic animals, except for deep-dwelling animals like Macoma petalum . However, within two months of this event animals returned to the mudflat. The resilience of the community suggested that the disturbance was not due to a persistent toxin or to anoxia. The reproductive mode of most species present in 2014 is reflective of species that were available either as pelagic larvae or as mobile adults. Although oviparous species were lower in number in this group, the authors hypothesize that these species will return slowly as more species move back into the area. The use of functional ecology was highlighted in the 2014 benthic community data, which showed that the animals that have now returned to the mudflat are those that can respond successfully to a physical, nontoxic disturbance. Today, community data show a mix of species that consume the sediment, or filter feed, have pelagic larvae that must survive landing on the sediment, and those that brood their young. USGS scientists view the 2008 disturbance event as a response by the infaunal community to an episodic natural stressor (possibly sediment accretion or a pulse of freshwater), in contrast to the long-term recovery from metal contamination. We will compare this recovery to the long-term recovery observed after the 1970’s when the decline in sediment pollutants was the dominating factor.

California↗

USGS2015

Health and condition of endangered juvenile Lost River and shortnose suckers relative to water quality and fish assemblages in Upper Klamath Lake, Oregon, and Clear Lake Reservoir, California

Executive Summary Most mortality of endangered Lost River ( Deltistes luxatus ) and shortnose ( Chasmistes brevirostris ) suckers in Upper Klamath Lake, Oregon, appears to occur within the first year of life. However, juvenile suckers in Clear Lake Reservoir, California, appear to survive longer and may even recruit to the spawning populations. Our goal in this study was to develop productive lines of inquiry into the causes of mortality of juvenile suckers, especially in Upper Klamath Lake, through comparison of sucker health and environmental conditions in both lakes. The health of juvenile suckers was associated with physical, biological, and chemical characteristics in each lake from July to September 2013 and 2014. Water-quality dynamics differed substantially between lakes. Diel fluctuations were greater for dissolved-oxygen concentrations and pH in Upper Klamath Lake than in Clear Lake Reservoir, but diel temperature fluctuations were greater in Clear Lake Reservoir. Minimum dissolved-oxygen concentrations were as low as 1.0 milligram per liter (mg/L) in Upper Klamath Lake, but were no lower than 5.7 mg/L in Clear Lake Reservoir. Unionized ammonia (NH 3 ) concentrations were near or less than the minimum reporting limit of 0.002 mg/L NH 3 in Clear Lake Reservoir and generally were less than the concentration known to cause cellular changes to the gills or mortality of suckers in Upper Klamath Lake. Concentrations of microcystins were less than the detection limit (≤0.10 microgram per liter [μg/L]) in both dissolved (<63 micrometers [μm]) and particulate (≥63 μm) fractions of water samples collected from Clear Lake Reservoir in both years. In Upper Klamath Lake, concentrations of microcystins were relatively low in the 2013 particulate fractions and dissolved fractions of samples in both years, but as high as 44.30 μg/L, more than 44 times the World Health Organization recommended levels for drinking water (1 μg/L), in the 2014 particulate fraction. However, there was little histological evidence and no chemical evidence that these concentrations in water were harmful to suckers that we captured. The species and age compositions of juvenile sucker populations differed between lakes. A total of 98 percent of all juvenile suckers captured in Upper Klamath Lake were age-0. In contrast, as many as six age classes of suckers were represented in Clear Lake Reservoir, indicating much better juvenile survival than in Upper Klamath Lake. Based on genetic species identification, 98 percent of juvenile suckers collected from Clear Lake Reservoir were shortnose or Klamath largescale suckers ( Catostomus snyderi ). In contrast, there was a high degree of apparent genetic hybridization in juvenile suckers collected from Upper Klamath Lake, and both Lost River and non-Lost River juvenile suckers were nearly equally represented in samples. Neither gross nor histological examination revealed a high prevalence of abnormalities in suckers that might indicate a mechanism for juvenile mortality in Upper Klamath Lake. Therefore, high mortality primarily may have occurred outside our study period (for example, in spring or over winter), or was owing to a factor that could not be detected with our methods (for example, predation). Alternatively, abnormalities in a small percentage of passively captured suckers in Upper Klamath Lake may indicate health-related issues that were more prevalent in populations than in our samples. Some apparent symptoms of stress or exposure to irritants, such as peribiliary cuffing in hepatocytes and mild inflammation and necrosis in gill tissues, were present in suckers from both lakes and do not appear to be clues to the cause of differential mortality between lakes. Seasonal trends in energy storage as glycogen and triglycerides were similar between lakes, indicating prey availability was not a factor in differential mortality. Differences in sucker health and condition between lakes were considered the most promising clues to the causes of differential juvenile sucker morality between lakes. A low prevalence of petechial hemorrhaging of the skin (16 percent) and deformed opercula (8 percent) in Upper Klamath Lake suckers may indicate exposure to a toxin other than microcystin. Suckers grew slower in their first year of life, but had similar or greater triglyceride and glycogen levels in Upper Klamath Lake compared to Clear Lake Reservoir. These findings do not suggest a lack of prey quantity but may indicate lower prey quality in Upper Klamath Lake.

California, Oregon↗

USGS2016

Logistic and linear regression model documentation for statistical relations between continuous real-time and discrete water-quality constituents in the Kansas River, Kansas, July 2012 through June 2015

The Kansas River is a primary source of drinking water for about 800,000 people in northeastern Kansas. Source-water supplies are treated by a combination of chemical and physical processes to remove contaminants before distribution. Advanced notification of changing water-quality conditions and cyanobacteria and associated toxin and taste-and-odor compounds provides drinking-water treatment facilities time to develop and implement adequate treatment strategies. The U.S. Geological Survey (USGS), in cooperation with the Kansas Water Office (funded in part through the Kansas State Water Plan Fund), and the City of Lawrence, the City of Topeka, the City of Olathe, and Johnson County Water One, began a study in July 2012 to develop statistical models at two Kansas River sites located upstream from drinking-water intakes. Continuous water-quality monitors have been operated and discrete-water quality samples have been collected on the Kansas River at Wamego (USGS site number 06887500) and De Soto (USGS site number 06892350) since July 2012. Continuous and discrete water-quality data collected during July 2012 through June 2015 were used to develop statistical models for constituents of interest at the Wamego and De Soto sites. Logistic models to continuously estimate the probability of occurrence above selected thresholds were developed for cyanobacteria, microcystin, and geosmin. Linear regression models to continuously estimate constituent concentrations were developed for major ions, dissolved solids, alkalinity, nutrients (nitrogen and phosphorus species), suspended sediment, indicator bacteria ( Escherichia coli , fecal coliform, and enterococci), and actinomycetes bacteria. These models will be used to provide real-time estimates of the probability that cyanobacteria and associated compounds exceed thresholds and of the concentrations of other water-quality constituents in the Kansas River. The models documented in this report are useful for characterizing changes in water-quality conditions through time, characterizing potentially harmful cyanobacterial events, and indicating changes in water-quality conditions that may affect drinking-water treatment processes.

Kansas↗

USGS2016

Near-field receiving water monitoring of trace metals and a benthic community near the Palo Alto Regional Water Quality Control Plant in south San Francisco Bay, California; 2015

Trace-metal concentrations in sediment and in the clam Macoma petalum (formerly reported as Macoma balthica ), clam reproductive activity, and benthic macroinvertebrate community structure were investigated in a mudflat 1 kilometer south of the discharge of the Palo Alto Regional Water Quality Control Plant (PARWQCP) in South San Francisco Bay, California. This report includes data collected by U.S. Geological Survey (USGS) scientists for the period from January 2015 to December 2015. These data are appended to long-term datasets extending back to 1974, and serve as the basis for the City of Palo Alto’s Near-Field Receiving Water Monitoring Program, initiated in 1994. Following significant reductions in the late 1980s, silver (Ag) and copper (Cu) concentrations in sediment and M. petalum appear to have stabilized. Data for other metals, including chromium (Cr), mercury (Hg), nickel (Ni), selenium (Se), and zinc (Zn), have been collected since 1994. Over this period, concentrations of these elements have remained relatively constant, aside from seasonal variation that is common to all elements. In 2015, concentrations of Ag and Cu in M. petalum varied seasonally in response to a combination of site-specific metal exposures and annual growth and reproduction, as reported previously. Seasonal patterns for other elements, including Cr, Ni, Zn, Hg, and Se, were generally similar in timing and magnitude as those for Ag and Cu. In M. petalum , all observed elements showed annual maxima in January–February and minima in April, except for Zn, which was lowest in December. In sediments, annual maxima also occurred in January–February, and minima were measured in June and September. In 2015, metal concentrations in both sediments and clam tissue were among the lowest on record. This record suggests that regional-scale factors now largely control sedimentary and bioavailable concentrations of Ag and Cu, as well as other elements of regulatory interest, at the Palo Alto site. Analyses of the benthic community structure at the same mudflat over a 40-year period show that changes in the community have occurred concurrent with reduced concentrations of metals in the sediment and in the tissues of the biosentinel clam, M. petalum , from the same area. Analysis of M. petalum shows increases in reproductive activity concurrent with the decline in metal concentrations in the tissues of this organism. Reproductive activity is presently stable (2015), with almost all animals initiating reproduction in the fall and spawning the following spring. The entire infaunal community has shifted from being dominated by several opportunistic species to a community where the species are more similar in abundance, a pattern that indicates a more stable community that is subjected to fewer stressors. In addition, two of the opportunistic species ( Ampelisca abdita and Streblospio benedicti ) that brood their young and live on the surface of the sediment in tubes have shown a continual decline in dominance coincident with the decline in metals; both species had short-lived rebounds in abundance in 2008, 2009, and 2010 and showed signs of increasing abundance in 2015. Heteromastus filiformis (a subsurface polychaete worm that lives in the sediment, consumes sediment and organic particles residing in the sediment, and reproduces by laying its eggs on or in the sediment) showed an increase in dominance, concurrent with the decrease in Ag and Cu concentrations, and in the last several years before 2008, showed a stable population. H. filiformis abundance increased slightly in 2011–2012 and returned to pre-2011 abundance in 2015. An unidentified disturbance occurred on the mudflat in early 2008 that resulted in the loss of the benthic animals, except for deep-dwelling animals like M. petalum . However, within two months of this event animals returned to the mudflat. The resilience of the community suggested that the disturbance was not due to a persistent toxin or to anoxia. The reproductive mode of most species present in 2015 is reflective of species that were available either as pelagic larvae or as mobile adults. Although oviparous (live-birth) species were lower in number in this group, the authors hypothesize that these species will return slowly as more species move back into the area. The use of functional ecology was highlighted in the 2015 benthic community data, which showed that the animals that have now returned to the mudflat are those that can respond successfully to a physical, nontoxic disturbance. Today, community data show a mix of species that consume the sediment, or filter feed, have pelagic larvae that must survive landing on the sediment, and those that brood their young. USGS scientists view the 2008 disturbance event as a response by the infaunal community to an episodic natural stressor (possibly sediment accretion or a pulse of freshwater), in contrast to the long-term recovery from metal contamination. We will compare this recovery to the long-term recovery observed after the 1970s when the decline in sediment pollutants was the dominating factor.

California↗

USGS2017

Water quality and bed sediment quality in the Albemarle Sound, North Carolina, 2012–14

The Albemarle Sound region was selected in 2012 as one of two demonstration sites in the Nation to test and improve the design of the National Water Quality Monitoring Council’s National Monitoring Network (NMN) for U.S. Coastal Waters and Tributaries. The goal of the NMN for U.S. Coastal Waters and Tributaries is to provide information about the health of our oceans, coastal ecosystems, and inland influences on coastal waters for improved resource management. The NMN is an integrated, multidisciplinary, and multi-organizational program using multiple sources of data and information to augment current monitoring programs. This report presents and summarizes selected water-quality and bed sediment-quality data collected as part of the demonstration project conducted in two phases. The first phase was an occurrence and distribution study to assess nutrients, metals, pesticides, cyanotoxins, and phytoplankton communities in the Albemarle Sound during the summer of 2012 at 34 sites in Albemarle Sound, nearby sounds, and various tributaries. The second phase consisted of monthly sampling over a year (March 2013 through February 2014) to assess seasonality in a more limited set of constituents including nutrients, cyanotoxins, and phytoplankton communities at a subset (eight) of the sites sampled in the first phase. During the summer of 2012, few constituent concentrations exceeded published water-quality thresholds; however, elevated levels of chlorophyll a and pH were observed in the northern embayments and in Currituck Sound. Chlorophyll a , and metals (copper, iron, and zinc) were detected above a water-quality threshold. The World Health Organization provisional guideline based on cyanobacterial density for high recreational risk was exceeded in approximately 50 percent of water samples collected during the summer of 2012. Cyanobacteria capable of producing toxins were present, but only low levels of cyanotoxins below human health benchmarks were detected. Finally, 12 metals in surficial bed sediments were detected at levels above a published sediment-quality threshold. These metals included chromium, mercury, copper, lead, arsenic, nickel, and cadmium. Sites with several metal concentrations above the respective thresholds had relatively high concentrations of organic carbon or fine sediment (silt plus clay), or both and were predominantly located in the western and northwestern parts of the Albemarle Sound. Results from the second phase were generally similar to those of the first in that relatively few constituents exceeded a water-quality threshold, both pH and chlorophyll a were detected above the respective water-quality thresholds, and many of these elevated concentrations occurred in the northern embayments and in Currituck Sound. In contrast to the results from phase one, the cyanotoxin, microcystin was detected at more than 10 times the water-quality threshold during a phytoplankton bloom on the Chowan River at Mount Gould, North Carolina in August of 2013. This was the only cyanotoxin concentration measured during the entire study that exceeded a respective water-quality threshold. The information presented in this report can be used to improve understanding of water-quality conditions in the Albemarle Sound, particularly when evaluating causal and response variables that are indicators of eutrophication. In particular, this information can be used by State agencies to help develop water-quality criteria for nutrients, and to understand factors like cyanotoxins that may affect fisheries and recreation in the Albemarle Sound region.

North Carolina, Virginia↗

USGS2017

Cyanobacteria of the 2016 Lake Okeechobee and Okeechobee Waterway harmful algal bloom

The Lake Okeechobee and the Okeechobee Waterway (Lake Okeechobee, the St. Lucie Canal and River, and the Caloosahatchee River) experienced an extensive harmful algal bloom within Lake Okeechobee, the St. Lucie Canal and River and the Caloosahatchee River in 2016. In addition to the very visible bloom of the cyanobacterium Microcystis aeruginosa , several other cyanobacteria were present. These other species were less conspicuous; however, they have the potential to produce a variety of cyanotoxins, including anatoxins, cylindrospermopsins, and saxitoxins, in addition to the microcystins commonly associated with Microcystis. Some of these species were found before, during, and 2 weeks after the large Microcystis bloom and could provide a better understanding of bloom dynamics and succession. This report provides photographic documentation and taxonomic assessment of the cyanobacteria present from Lake Okeechobee and the Caloosahatchee River and St. Lucie Canal, with samples collected June 1st from the Caloosahatchee River and Lake Okeechobee and in July from the St. Lucie Canal. The majority of the images were of live organisms, allowing their natural complement of pigmentation to be captured. The report provides a digital image-based taxonomic record of the Lake Okeechobee and the Okeechobee Waterway microscopic flora. It is anticipated that these images will facilitate current and future studies on this system, such as understanding the timing of cyanobacteria blooms and their potential toxin production.

Florida↗

USGS2017

Near-field receiving water monitoring of trace metals and a benthic community near the Palo Alto Regional Water Quality Control Plant in south San Francisco Bay, California; 2016

Trace-metal concentrations in sediment and in the clam Macoma petalum (formerly reported as Macoma balthica ), clam reproductive activity, and benthic macroinvertebrate community structure were investigated in a mudflat 1 kilometer south of the discharge of the Palo Alto Regional Water Quality Control Plant (PARWQCP) in south San Francisco Bay, Calif. This report includes the data collected by U.S. Geological Survey (USGS) scientists for the period January 2014 to December 2016. These append to long-term datasets extending back to 1974. A major focus of the report is an integrated description of the 2016 data within the context of the longer, multi-decadal dataset. This dataset supports the City of Palo Alto’s Near-Field Receiving Water Monitoring Program, initiated in 1994. Significant reductions in silver and copper concentrations in sediment and M. petalum occurred at the site in the 1980s following the implementation by PARWQCP of advanced wastewater treatment and source control measures. Since the 1990s, concentrations of these elements appear to have stabilized at concentrations somewhat above (silver) or near (copper) regional background concentrations Data for other metals, including chromium (Cr), mercury (Hg), nickel (Ni), selenium (Se), and zinc (Zn), have been collected since 1994. Over this period, concentrations of these elements have remained relatively constant, aside from seasonal variation that is common to all elements. In 2016, concentrations of silver and copper in M. petalum varied seasonally in response to a combination of site-specific metal exposures and annual growth and reproduction, as reported previously. Seasonal patterns for other elements, including Cr, Ni, Zn, Hg, and Se, were generally similar in timing and magnitude as those for Ag and Cu. This record suggests that legacy contamination and regional-scale factors now largely control sedimentary and bioavailable concentrations of silver and copper, as well as other elements of regulatory interest, at the Palo Alto site. Analyses of the benthic community structure of a mudflat in south San Francisco Bay over a 40-year period show that changes in the community have occurred concurrent with reduced concentrations of metals in the sediment and in the tissues of the biosentinel clam, M. petalum , from the same area. Analysis of M. petalum shows increases in reproductive activity concurrent with the decline in metal concentrations in the tissues of this organism. Reproductive activity is presently stable (2016), with almost all animals initiating reproduction in the fall and spawning the following spring. The entire infaunal community has shifted from being dominated by several opportunistic species to a community where the species are more similar in abundance, a pattern that indicates a more stable community that is subjected to fewer stressors. In addition, two of the opportunistic species ( Ampelisca abdita and Streblospio benedicti ) that brood their young and live on the surface of the sediment in tubes have shown a continual decline in dominance coincident with the decline in metals; both species had short-lived rebounds in abundance in 2008, 2009, and 2010 and showed signs of increasing abundance in 2016. Heteromastus filiformis (a subsurface polychaete worm that lives in the sediment, consumes sediment and organic particles residing in the sediment, and reproduces by laying its eggs on or in the sediment) showed a concurrent increase in dominance and, in the last several years before 2008, showed a stable population. H. filiformis abundance increased slightly in 2011–2012 and returned to pre-2011 numbers in 2016. An unidentified disturbance occurred on the mudflat in early 2008 that resulted in the loss of the benthic animals, except for deep-dwelling animals like Macoma petalum . However, within two months of this event animals returned to the mudflat. The resilience of the community suggested that the disturbance was not due to a persistent toxin or anoxia. The reproductive mode of most species present in 2016 is reflective of species that were available either as pelagic larvae or as mobile adults. Although oviparous species were lower in number in this group, the authors hypothesize that these species will return slowly as more species move back into the area. The use of functional ecology was highlighted in the 2016 benthic community data, which showed that the animals that have now returned to the mudflat are those that can respond successfully to a physical, nontoxic disturbance. Today, community data show a mix of species that consume the sediment, or filter feed, have pelagic larvae that must survive landing on the sediment, and those that brood their young. USGS scientists view the 2008 disturbance event as a response by the infaunal community to an episodic natural stressor (possibly sediment accretion or a pulse of freshwater), in contrast to the long-term recovery from metal contamination. We will compare this recovery to the long-term recovery observed after the 1970s when the decline in sediment pollutants was the dominating factor.

California↗

USGS2018

Near-field receiving-water monitoring of trace metals and a benthic community near the Palo Alto Regional Water Quality Control Plant in south San Francisco Bay, California—2017

Trace-metal concentrations in sediment and in the clam Macoma petalum (formerly reported as Macoma balthica ), clam reproductive activity, and benthic macroinvertebrate community structure were investigated in a mudflat 1 kilometer south of the discharge of the Palo Alto Regional Water Quality Control Plant (PARWQCP) in south San Francisco Bay, Calif. This report includes the data collected by U.S. Geological Survey (USGS) scientists for the period January 2017 to December 2017. These append to long-term datasets extending back to 1974. A major focus of the report is an integrated description of the 2017 data within the context of the longer, multi-decadal dataset. This dataset supports the City of Palo Alto’s Near-Field Receiving Water Monitoring Program, initiated in 1994. Significant reductions in silver and copper concentrations in sediment and M. petalum occurred at the site in the 1980s following the implementation by PARWQCP of advanced wastewater treatment and source control measures. Since the 1990s, concentrations of these elements appear to have stabilized at concentrations somewhat above silver (Ag) or near copper (Cu) regional background concentrations. Data for other metals, including chromium (Cr), mercury (Hg), nickel (Ni), selenium (Se), and zinc (Zn), have been collected since 1994. Over this period, concentrations of these elements have remained relatively constant, aside from seasonal variation that is common to all elements. In 2017, concentrations of silver and copper in M. petalum varied seasonally in response to a combination of site-specific metal exposures and annual growth and reproduction, as reported previously. Seasonal patterns for other elements, including Cr, Ni, Zn, Hg, and Se, were generally similar in timing and magnitude as those for Ag and Cu. This record suggests that legacy contamination and regional-scale factors now largely control sedimentary and bioavailable concentrations of silver and copper, as well as other elements of regulatory interest, at the Palo Alto site. Analyses of the benthic community structure of a mudflat in south San Francisco Bay over a 40-year period show that changes in the community have occurred concurrent with reduced concentrations of metals in the sediment and in the tissues of the biosentinel clam, M. petalum , from the same area. Analysis of M. petalum shows increases in reproductive activity concurrent with the decline in metal concentrations in the tissues of this organism. Reproductive activity is presently stable (2017), with almost all animals initiating reproduction in the fall and spawning the following spring. The entire infaunal community has shifted from being dominated by several opportunistic species to a community where the species are more similar in abundance, a pattern that indicates a more stable community that is subjected to fewer stressors. In addition, two of the opportunistic species ( Ampelisca abdita and Streblospio benedicti ) that brood their young and live on the surface of the sediment in tubes have shown a continual decline in dominance coincident with the decline in metals; both species had short-lived rebounds in abundance in 2008, 2009, and 2010 and showed signs of increasing abundance in 2017. Heteromastus filiformis (a subsurface polychaete worm that lives in the sediment, consumes sediment and organic particles residing in the sediment, and reproduces by laying its eggs on or in the sediment) showed a concurrent increase in dominance and, in the last several years before 2008, showed a stable population. H. filiformis abundance increased slightly in 2011–2012 and returned to pre-2011 numbers in 2017. An unidentified disturbance occurred on the mudflat in early 2008 that resulted in the loss of the benthic animals, except for deep-dwelling animals like M. petalum . However, within two months of this event animals returned to the mudflat. The resilience of the community suggested that the disturbance was not due to a persistent toxin or anoxia. The reproductive mode of most species that were present in 2017 is reflective of species that were available either as pelagic larvae or as mobile adults. Although oviparous species were lower in number in this group, the authors hypothesize that these species will return slowly as more species move back into the area. The use of functional ecology was highlighted in the 2017 benthic community data, which showed that the animals that have now returned to the mudflat are those that can respond successfully to a physical, nontoxic disturbance. Today, community data show a mix of species that consume the sediment, or filter feed, have pelagic larvae that must survive landing on the sediment, and those that brood their young. USGS scientists view the 2008 disturbance event as a response by the infaunal community to an episodic natural stressor (possibly sediment accretion or a pulse of freshwater), in contrast to the long-term recovery from metal contamination. We will compare this recovery to the long-term recovery observed after the 1970s when the decline in sediment pollutants was the dominating factor.

California↗

USGS2019

Southern sea otter (Enhydra lutris nereis) population biology at Big Sur and Monterey, California --Investigating the consequences of resource abundance and anthropogenic stressors for sea otter recovery

The range of the southern sea otter ( Enhydra lutris nereis ) spans most of the central California coast from Half Moon Bay to Gaviota. Some coastal areas within this range are heavily developed and highly impacted by humans, while other areas are wild and largely pristine. Determining the relative importance of food resource abundance, environmental conditions, and anthropogenic increases in pathogens and pollutants to population change in sea otters is critical to understanding limitations to population growth. To investigate the causal links between the sluggish population growth of sea otters in central California and factors that could be driving variation in survival and reproduction, we designed a study to compare two distinct subpopulations—one in an area of low human impact (Big Sur) and one in an area of high human impact (Monterey). Between 2008 and 2011, the U.S. Geological Survey and collaborators conducted a telemetry-based study of sea otters at these two locations. The results of this study were not consistent with the hypothesis that sea otters adjacent to human population centers (Monterey) experience higher exposure to pollutants and pathogens than those in lower impacted areas (Big Sur). In fact, based on serological analysis, female sea otters from Big Sur showed higher exposure rates to Toxoplasma gondii than did female otters from Monterey, while domoic acid exposure appeared to be similar at both sites. Gene expression (specifically transcription) analysis did not indicate any consistent differences between the two populations that would have suggested a response to pathogen or toxin exposure, although there were temporal changes in gene transcription for sea otters at Big Sur following potential exposure to run-off from wildfires that occurred during the study. Together, these metrics suggest that variation in exposure to environmental stressors occurred, but patterns were not clearly attributable to differences in human population densities or land-use patterns. When compared to Monterey, sea otters in Big Sur spent more time feeding, had a higher degree of dietary specialization, were in poorer body condition, and had lower survival rates (both pups and adults). Together, these metrics suggest that otters at Big Sur had greater nutritional stress, consistent with lower per-capita resource abundance. Overall, study results indicate that density-dependent population regulation, mediated by per-capita resource abundance, is the most significant factor currently limiting population growth in the center part of the range. Additionally, spatial and temporal variation in environmental and anthropogenic stressors also can affect sea otter health, although patterns of variation are complex and are not simply a function of proximity to human populations. We also found that exposure to environmental stressors (either natural or anthropogenic in origin) often is associated with resource limitation. Finally, our results indicate that sea otter populations are structured at relatively small spatial scales, and the processes that regulate population abundance (including density-dependent resource abundance) also occur at these smaller, more local scales.

California↗

USGS2019

Effects of microcystin-LR on juvenile Lost River suckers (Deltistes luxatus) during feeding trials, Upper Klamath Lake, Oregon, 2014−16

Executive Summary Historically, populations of Lost River suckers ( Deltistes luxatus ) of the Upper Klamath Basin were so numerous that they were commercially harvested; however, declining numbers throughout the 20th century led to the listing of the species under the United States Endangered Species Act in 1988. Habitat destruction, poor water quality, competition with (and predation by) nonnative species, especially fathead minnows ( Pimephales promelas ) and yellow perch ( Perca flavescens ), are hypothesized as primary causes of population decline (U.S. Fish and Wildlife Service, 2013). Age data indicate that almost all adult suckers presently in Upper Klamath Lake spawning populations were hatched in the early 1990s. While entrainment of young fish (especially larvae) may contribute, catch-at-length and age data suggest consistently high mortality during the first year of life may be preventing the recruitment of young adults. The specific causes of juvenile sucker mortality are unknown; however, the absence of juvenile suckers in trap net catches coincides with degraded water quality associated with the decay of cyanobacteria blooms and exposure to toxic microcystin produced by Microcystis cyanobacteria. Water-quality data collected in Upper Klamath Lake from 2011 to 2016 suggest that microcystin concentrations in Upper Klamath Lake reached potentially lethal levels based on literature findings from studies on a variety of fish species. We conducted a laboratory feeding trial to determine if microcystin toxicity could potentially be a direct cause of juvenile Lost River sucker mortality. We examined the effects of environmentally relevant doses of microcystin on the survival and health of hatchery-reared juvenile Lost River suckers. Results from this laboratory study suggest that Lost River suckers are very tolerant of the microcystin-LR toxin. Histopathological analysis revealed no evidence of tissue changes associated with microcystin-LR exposure. Although no direct effects of microcystin-LR exposure were detected, suckers could potentially be negatively affected through added energy expenditures and stress associated with excretion of microcystin. Furthermore, microcystin may adversely affect other organisms in Upper Klamath Lake that could alter food availability or habitat of the suckers.

Oregon↗

USGS2021

Near-field receiving-water monitoring of trace metals and a benthic community near the Palo Alto Regional Water Quality Control Plant in south San Francisco Bay, California—2019

Trace-metal concentrations in sediment and in the clam Limecola petalum (formerly reported as Macoma balthica and M. petalum ), clam reproductive activity, and benthic macroinvertebrate community structure were investigated in a mudflat 1 kilometer south of the discharge of the Palo Alto Regional Water Quality Control Plant (PARWQCP) in south San Francisco Bay, Calif. This report includes the data collected by the U.S. Geological Survey (USGS) for the period January 2019 to December 2019. These data append to long-term datasets extending back to 1974. A major focus of the report is an integrated description of the 2019 data within the context of the longer, multidecadal dataset. This dataset supports the City of Palo Alto’s Near-Field Receiving-Water Monitoring Program, initiated in 1994. Significant reductions in silver and copper contamination occurred at the site in the 1980s following the implementation by PARWQCP of advanced wastewater treatment and source control measures. Since the 1990s, concentrations of these elements in surface sediments have continued to decrease, although more slowly. Silver appears to have stabilized at concentrations about twice the regional background concentration. Presently, sediment copper concentrations appear to be near the regional background level. Over the same period (1994–2019), sedimentary iron and zinc also exhibited modest declines. Sedimentary aluminum, chromium, mercury, nickel, and selenium have not exhibited any trend. Since 1994, concentrations of silver and copper in L. petalum have varied seasonally, apparently in response to a combination of site-specific metal exposures and cyclic growth and reproduction, as reported previously. Seasonal patterns for other elements, including chromium, mercury, nickel, selenium, and zinc, were generally similar in timing and magnitude as those for silver and copper. The annual growth and reproductive cycle explained a small amount of the variance in annual silver and zinc tissue metal concentrations. However, interannual trends are not apparent for any element. Biological effects of elevated silver and copper contamination at the Palo Alto site have been interpreted from data collected during and after the recession of these contaminants. Concentrations of both elements in the soft tissues of L. petalum declined with sedimentary copper and silver. This pattern was associated with changes in the reproductive activity of L. petalum , as well as the structure of the benthic invertebrate community. Reproductive activity of L. petalum increased as metal concentrations in L. petalum declined and presently is stable with almost all animals initiating reproduction in the fall and spawning the following spring. Analyses of the benthic community structure indicate that the infaunal invertebrate community has shifted from one dominated by several opportunistic species when silver and copper exposures were highest to one in which the species abundance is more evenly distributed, a pattern that indicates a more stable community that is subjected to fewer stressors. Importantly, this long-term change is unrelated to other metals and other measured environmental factors, including salinity and sediment composition. In addition, two of the opportunistic species ( Ampelisca abdita and Streblospio benedicti ) that brood their young and live on the surface of the sediment in tubes have shown a continual decline in dominance coincident with the decline in metals. Both species had short-lived rebounds in abundance in 2008, 2009, and 2010 and showed signs of increasing abundance in 2019. Heteromastus filiformis (a subsurface polychaete worm that lives in the sediment, consumes sediment and organic particles residing in the sediment, and reproduces by laying its eggs on or in the sediment) showed a concurrent increase in dominance and, in the last several years before 2008, showed a stable population. H. filiformis abundance increased slightly in 2011–2012 and returned to pre-2011 numbers in 2019. An unidentified disturbance occurred on the mudflat in early 2008 that resulted in the loss of the benthic animals, except for deep-dwelling animals like L. petalum . However, within two months of this event, animals returned to the mudflat. The resilience of the community suggested that the disturbance was not caused by a persistent toxin or anoxia. The reproductive mode of most species that were present in 2019 was indicative of species that were available either as pelagic larvae or as mobile adults. Although oviparous species were lower in number in this group, the authors hypothesize that these species will return slowly as more species move back into the area. The use of functional ecology was highlighted in the 2019 benthic community data, which showed that the animals that have now returned to the mudflat are those that can respond successfully to a physical, nontoxic disturbance. Today, community data show a mix of species that consume the sediment, or filter feed, those that have pelagic larvae that must survive landing on the sediment, and those that brood their young. USGS scientists view the 2008 disturbance event as a response by the infaunal community to an episodic natural stressor (possibly sediment accretion or a pulse of freshwater), in contrast to the long-term recovery from metal contamination. We will compare this recovery to the long-term recovery observed after the 1970s when the decline in sediment pollutants was the dominating factor.

California↗

USGS2024

Knowledge gaps and opportunities in water-quality drivers of aquatic ecosystem health

This report identifies key scientific gaps that limit our ability to predict water quality effects on health of aquatic ecosystems and proposes approaches to address those gaps. Topics considered include (1) coupled nutrient-carbon cycle processes and related ecological-flow-regime drivers of ecosystem health, (2) anthropogenic and geogenic toxin bioexposure, (3) fine sediment drivers of aquatic ecosystem health, and (4) freshwater salinization. Each topic is addressed in terms of scientific gaps, approaches, and timelines to help guide portions of the U.S. Geological Survey Water Mission Area ( https://www.usgs.gov/mission-areas/water-resources ) research portfolio and other national research efforts. The report provides an assessment of several of the major challenges and opportunities concerning water quality impacts on aquatic ecosystem health. It will be important to maintain broad-based expertise and flexibility to address the full range of long-term water quality issues facing the Nation’s water resources.

Open-File Report↗

USGS2004

Chemical Data for Detailed Studies of Irrigation Drainage in the Salton Sea Area, California, 1995?2001

The primary purpose of this report is to present all chemical data from the Salton Sea area collected by the U.S. Geological Survey between 1995 and 2001. The data were collected primarily for the Department of the Interior's National Irrigation Water Quality Program (NIWQP). The report also contains a brief summary and citation to investigations done for the NIWQP between 1992 and 1995. The NIWQP began studies in the Salton Sea area in 1986 to evaluate effects on the environment from potential toxins, especially selenium, in irrigation-induced drainage. This data report is a companion to several reports published from the earlier studies and to interpretive publications that make use of historical and recent data from this area. Data reported herein are from five collection studies. Water, bottom material, and suspended sediment collected in 1995-96 from the New River, the lower Colorado River, and the All-American Canal were analyzed for elements, semi-volatile (extractable) organic compounds, and organochlorine compounds. Sufficient suspended sediment for chemical analyses was obtained by tangential-flow filtration. A grab sample of surficial bottom sediment collected from near the deepest part of the Salton Sea in 1996 was analyzed for 44 elements and organic and inorganic carbon. High selenium concentration confirmed the effective transfer (sequestration) of selenium into the bottom sediment. Similar grab samples were collected 2 years later (1998) from 11 locations in the Salton Sea and analyzed for elements, as before, and also for nutrients, organochlorine compounds, and polycyclic aromatic hydrocarbons. Nutrients were measured in bottom water, and water-column profiles were obtained for pH, conductance, temperature, and dissolved oxygen. Element and nutrient concentrations were obtained in 1999 from cores at 2 of the above 11 sites, in the north subbasin of the Salton Sea. The most-recent study reported herein was done in 2001 and contains element data on suspended material isolated by continuous-flow centrifugation on samples collected in transects extending out from the Whitewater, the Alamo, and the New Rivers into the Salton Sea. Chemical data on suspended sediment and bottom material from tributory rivers and the Salton Sea itself show that many insoluble constituents, including selenium and DDE, are concentrated in the fine-grained, organic- and carbonate-rich bottom sediment from deep areas near the center of the Salton Sea. Data also show that selenium and arsenic are markedly enriched in seston (plankton, partially-degraded algal detritus, and mineral matter that compose suspended particulates in the lake) collected just below the water surface in the Salton Sea. This result indicates that bio-concentration in primary producers in the water column provides an important pathway whereby high selenium residues accumulate in fish and fish-eating birds at the Salton Sea.

Scientific Investigations Report↗

USGS2005

Status of fish communities in the Rio Grande, Big Bend National Park, Texas - comparison before and after Spring 2003 period of low flow

During 2003–04 the U.S. Geological Survey, in cooperation with the National Park Service, re-evaluated the status of fish communities in three reaches of the Rio Grande in Big Bend National Park that originally were evaluated when the three reaches were established for study in 1999. The objective was to determine whether there were measurable differences between 1999 and 2003–04 (referred to as 2004) fish community status that likely are attributable to a rare 58-day period of low flow (less than 1 cubic meter per second) in spring 2003 at the Johnson Ranch gaging station on the Rio Grande in Big Bend National Park. The total number of fish species collected at all three sites (Boquillas, Johnson Ranch, and Santa Elena) in 1999 was greater than in 2004. The number of fish species collected at the Boquillas site in 1999 (10) was twice that collected in 2004; the number of species collected at the Johnson Ranch site in 1999 (nine) was almost twice that collected in 2004 (five). In contrast, the numbers at the Santa Elena site were nearly the same, 15 species in 1999, 14 in 2004. Percent community similarity for the Boquillas site is 8.04, for the Johnson Ranch site, 6.65, and for the Santa Elena site, 47.6, which indicates considerably more similarity between the 1999 and 2004 fish communities at the Santa Elena site than for the Boquillas and Johnson Ranch sites. At the Boquillas and Johnson Ranch sites, the fish communities shifted from small minnow (Cyprinidae) dominated in 1999 to largely gar (Lepisosteidae) and catfish (Ictaluridae) dominated in 2004. In contrast, no such shift occurred at the Santa Elena site between 1999 and 2004. Differences in flow conditions between the two downstream sites and the Santa Elena site might account for the dissimilar findings. The findings of the study provide some evidence that the spring 2003 period of low flow affected fish communities, but the findings are not definitive as other factors such as increased salinity, algal toxins, bioavailable contaminants, and exotic species can affect fish populations and, ultimately, fish community structure.

Chihuahua, Coahuila, Texas↗

USGS2010

Sedimentation, sediment quality, and upstream channel stability, John Redmond Reservoir, east-central Kansas, 1964-2009

A combination of available bathymetric-survey information, bottom-sediment coring, and historical streamgage information was used to investigate sedimentation, sediment quality, and upstream channel stability for John Redmond Reservoir, east-central Kansas. Ongoing sedimentation is reducing the ability of the reservoir to serve several purposes including flood control, water supply, and recreation. The total estimated volume and mass of bottom sediment deposited between 1964 and 2009 in the conservation pool of the reservoir was 1.46 billion cubic feet and 55.8 billion pounds, respectively. The estimated sediment volume occupied about 41 percent of the conservation-pool, water-storage capacity of the reservoir. Water-storage capacity in the conservation pool has been lost to sedimentation at a rate of about 1 percent annually. Mean annual net sediment deposition since 1964 in the conservation pool of the reservoir was estimated to be 1.24 billion pounds per year. Mean annual net sediment yield from the reservoir basin was estimated to be 411,000 pounds per square mile per year Information from sediment cores shows that throughout the history of John Redmond Reservoir, total nitrogen concentrations in the deposited sediment generally were uniform indicating consistent nitrogen inputs to the reservoir. Total phosphorus concentrations in the deposited sediment were more variable than total nitrogen indicating the possibility of changing phosphorus inputs to the reservoir. As the principal limiting factor for primary production in most freshwater environments, phosphorus is of particular importance because increased inputs can contribute to accelerated reservoir eutrophication and the production of algal toxins and taste-and-odor compounds. The mean annual net loads of total nitrogen and total phosphorus deposited in the bottom sediment of the reservoir were estimated to be 2,350,000 pounds per year and 1,030,000 pounds per year, respectively. The estimated mean annual net yields of total nitrogen and total phosphorus from the reservoir basin were 779 pounds per square mile per year and 342 pounds per square mile per year, respectively. Trace element concentrations in the bottom sediment of John Redmond Reservoir generally were uniform over time. As is typical for eastern Kansas reservoirs, arsenic, chromium, and nickel concentrations typically exceeded the threshold-effects guidelines, which represent the concentrations above which toxic biological effects occasionally occur. Trace element concentrations did not exceed the probable-effects guidelines (available for eight trace elements), which represent the concentrations above which toxic biological effects usually or frequently occur. Organochlorine compounds either were not detected or were detected at concentrations that were less than the threshold-effects guidelines. Stream channel banks, compared to channel beds, likely are a more important source of sediment to John Redmond Reservoir from the upstream basin. Other sediment sources include surface-soil erosion in the basin and shoreline erosion in the reservoir.

Scientific Investigations Report↗

USGS2011

Sedimentation and occurrence and trends of selected nutrients, other chemical constituents, and cyanobacteria in bottom sediment, Clinton Lake, northeast Kansas, 1977-2009

A combination of available bathymetric-survey information and bottom-sediment coring was used to investigate sedimentation and the occurrence of selected nutrients (total nitrogen and total phosphorus), organic and total carbon, 25 trace elements, cyanobacterial akinetes, and the radionuclide cesium-137 in the bottom sediment of Clinton Lake, northeast Kansas. The total estimated volume and mass of bottom sediment deposited from 1977 through 2009 in the conservation (multi-purpose) pool of the reservoir was 438 million cubic feet and 18 billion pounds, respectively. The estimated sediment volume occupied about 8 percent of the conservation-pool, water-storage capacity of the reservoir. Sedimentation in the conservation pool has occurred about 70 percent faster than originally projected at the time the reservoir was completed. Water-storage capacity in the conservation pool has been lost to sedimentation at a rate of about 0.25 percent annually. Mean annual net sediment deposition since 1977 in the conservation pool of the reservoir was estimated to be 563 million pounds per year. Mean annual net sediment yield from the Clinton Lake Basin was estimated to be 1.5 million pounds per square mile per year. Typically, the bottom sediment sampled in Clinton Lake was at least 99 percent silt and clay. The mean annual net loads of total nitrogen and total phosphorus deposited in the bottom sediment of Clinton Lake were estimated to be 1.29 million pounds per year and 556,000 pounds per year, respectively. The estimated mean annual net yields of total nitrogen and total phosphorus from the Clinton Lake Basin were 3,510 pounds per square mile per year and 1,510 pounds per square mile per year, respectively. Throughout the history of Clinton Lake, total nitrogen concentrations in the deposited sediment generally were uniform and indicated consistent inputs to the reservoir over time. Likewise, total phosphorus concentrations in the deposited sediment generally were uniform. Although, for two of three coring sites, a possible positive trend in phosphorus deposition was indicated. The Wakarusa River possibly was a larger contributor of nitrogen and phosphorus to Clinton Lake than was Rock Creek. As a principal limiting factor for primary production in most freshwater environments, phosphorus is of particular importance because increased inputs can contribute to accelerated reservoir eutrophication and the production of algal toxins and taste-and-odor compounds. Trace-element concentrations in the bottom sediment of Clinton Lake generally were uniform over time. As is typical for eastern Kansas reservoirs, arsenic, chromium, and nickel concentrations typically exceeded the threshold-effects guidelines, which represent the concentrations above which toxic biological effects occasionally occur. Zinc concentrations frequently exceeded the threshold-effects guideline. Trace-element concentrations did not exceed the probable-effects guidelines (available for eight trace elements), which represent the concentrations above which toxic biological effects usually or frequently occur. Cyanobacterial akinetes (cyanobacteria resting stage) in the bottom sediment of Clinton Lake, combined with historical water-quality data on chlorophyll-a and total phosphorus concentrations, indicated that the reservoir likely has been eutrophic throughout most of its history. A statistically significant increase in cyanobacterial akinetes in the bottom sediment indicated that Clinton Lake may have become more eutrophic over the life of the reservoir. The increase in cyanobacterial akinetes may, in part, be related to a possible increase in total phosphorus concentrations.

Scientific Investigations Report↗