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Daniel J. Cain

Publications and source records attributed to Daniel J. Cain.

At least 37 records · Page 2Linked to original sources
USGS2013

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, 2012

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 to December 2012. 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 in 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 2012, 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 for previous time periods. 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 2012, 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 39-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 (2012), 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. 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 2012 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 2012 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↗
USGS2012

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: 2011

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 2011 to December 2011. 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, mercury, nickel, selenium, and zinc, 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 2011, 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, Hg, Ni, Se, and Zn, were generally similar in timing and magnitude as those for Ag and Cu. In 2011, 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 38-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 (2011), 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. 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 2011 is reflective of the species that were available either as pelagic larvae or as mobile adults. Although egg layers 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 2011 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↗
USGS2011

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: 2010

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 for the period January 2010 to December 2010 and extends a critical long-term biogeochemical record that dates back to 1974. These data serve as the basis for the City of Palo Alto’s Near-Field Receiving Water Monitoring Program initiated in 1994. In 2010, metal concentrations in both sediments and clam tissue were among the lowest concentrations on record and consistent with results observed since 1991. Following significant reductions in the late 1980s, silver (Ag) and copper (Cu) concentrations appear to have stabilized. Annual mean concentrations have fluctuated modestly (2–4 fold) in a nondirectional manner. Data for other metals, including chromium, mercury, nickel, selenium, vanadium, and zinc, have been collected since 1994. Over this period, concentrations of these elements, which likely reflect regional inputs and systemwide processes, have remained relatively constant, aside from typical seasonal variation that is common to all elements. Within years, the winter months (January–March) generally exhibit maximum concentrations, with a decline to annual minima in spring through fall. Concentrations of chromium (Cr) and vanadium (V) in sediments have shown an upward trend since 2005. Chromium concentrations are approaching the record maximum levels observed in 2003, and concentrations of V in sediments in 2010 were the highest annual average concentrations on record. Mercury (Hg) concentrations in sediments and M. petalum in 2010 were comparable to concentrations observed in 2009 and were generally consistent with data from previous years. Selenium (Se) concentrations in sediment varied among years and showed no sustained temporal trend. During 2009–2010, sedimentary Se concentrations declined from the record high observed in 2008 to concentrations that were among the lowest on record. Selenium in M. petalum was slightly higher in 2010 than in 2009. Overall, Cu and Ag concentrations in sediments and soft tissues of the clam, M. petalum , remained representative of the concentrations observed since 1991 following significant reductions in the discharge of these elements from the PARWQCP. This indicates that, as with other elements of regulatory interest, regional-scale factors now largely affect sedimentary and bioavailable concentrations of Ag and Cu. Analyses of the benthic community structure of a mudflat in South San Francisco Bay over a 37-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 (2010), with almost all animals initiating reproduction in the fall and spawning the following spring of most years. 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 last several years prior to 2008, showed a stable population. 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 use of functional ecology was highlighted in the 2010 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 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↗
USGS2010

Calibrating biomonitors to ecological disturbance: a new technique for explaining metal effects in natural waters

Bioaccumulated toxic metals in tolerant biomonitors are indicators of metal bioavailability and can be calibrated against metal‐specific responses in sensitive species, thus creating a tool for defining dose–response for metals in a field setting. Dose–response curves that define metal toxicity in natural waters are rare. Demonstrating cause and effect under field conditions and integrated chemical measures of metal bioavailability from food and water is problematic. The total bioaccumulated metal concentration in any organism that is a net accumulator of the metal is informative about metal bioavailability summed across exposure routes. However, there is typically no one universal metal concentration that is indicative of toxicity, especially across species, largely because of interspecies differences in detoxification. Stressed organisms are also only present across a narrow range in the dose–response curve, limiting the use of singles species as both biomonitors and bioindicator of stress. Herein we show, in 3 field settings, that bioaccumulated Cu concentrations in a metal‐tolerant, riverine biomonitor (species of the caddisfly genus Hydropsyche spp.) can be calibrated against metal‐specific ecological responses across very wide ranges of contamination. Using the calibrated dose–response, we show that reduced abundance of species and individuals from particularly sensitive mayfly families (heptageniid mayflies) is more than 2‐fold more sensitive to bioavailable Cu than other traditional measures of stress like EPT or total number of benthic macroinvertebrate species. We propose that this field dose‐response curve be tested more widely for general application, and that calibrations against other stress responses be developed for biomonitors from lakes, estuaries, and coastal marine ecosystems.

Integrated Environmental Assessment and Management↗
USGS2010

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; 2009

Results reported herein include trace element concentrations in sediment and in the clam Macoma petalum (formerly reported as Macoma balthica (Cohen and Carlton, 1995)), clam reproductive activity, and benthic macroinvertebrate community structure for a mudflat one kilometer south of the discharge of the Palo Alto Regional Water Quality Control Plant (PARWQCP) in South San Francisco Bay. This report includes data collected for the period January 2009 to December 2009 and extends a critical long-term biogeochemical record dating back to 1974. These data serve as the basis for the City of Palo Alto’s Near-Field Receiving Water Monitoring Program, initiated in 1994. In 2009, metal concentrations in both sediments and clam tissue were among the lowest concentrations on record and consistent with results observed since 1991. Following significant reductions in the late 1980s, silver (Ag) and copper (Cu) concentrations appeared to have stabilized. Annual mean concentrations have fluctuated modestly (2–4 fold) in a nondirectional manner. Data for other metals, including chromium, mercury, nickel, selenium, vanadium, and zinc, have been collected since 1994. Over this period, concentrations of these elements, which more likely reflect regional inputs and systemwide processes, have remained relatively constant, aside from typical seasonal variation that is common to all elements. Within years, the winter months (January–March) generally exhibit maximum concentrations, with a decline to annual minima in spring through fall. Mercury (Hg) in sediments and M. petalum were comparable to concentrations observed in 2008 and were generally consistent with data from previous years. Selenium (Se) concentrations in sediment varied among years and showed no sustained temporal trend. In 2009, sedimentary Se concentrations declined from the record high concentrations observed in 2008 to concentrations that were among the lowest on record. Selenium in M. petalum was unchanged from 2008. Overall, Cu and Ag concentrations in sediments and soft tissues of the clam, M. petalum , remained representative of the concentrations observed since 1991 following significant reductions in the discharge of these elements from the PARWQCP. This suggests that, as with other elements of regulatory interest, regional-scale factors now largely influence sedimentary and bioavailable concentrations of Ag and Cu. Analyses of the benthic community structure of a mudflat in South San Francisco Bay over a 36-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 reproductive activity 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, with almost all animals initiating reproduction in the fall and spawning the following spring of most years. 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 suggests 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 and 2009. 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, with the last several years prior to 2008 showing a stable population. 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 use of functional ecology was highlighted in the 2009 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 we see plenty of animals that consume the sediment, have pelagic larvae that must survive landing on the sediment, and in some cases have eggs that must survive being laid in the sediment. We continue to observe the community’s response to the defaunation event, because it allows us 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 longer-term recovery we observed in the 1970s, when the decline in sediment pollutants was the dominating factor.

California↗
USGS2009

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: 2008

Results reported herein include trace element concentrations in sediment and in the clam Macoma petalum (formerly reported as Macoma balthica (Cohen and Carlton, 1995)), clam reproductive activity, and benthic macroinvertebrate community structure for a mudflat one kilometer south of the discharge of the Palo Alto Regional Water Quality Control Plant (PARWQCP) in South San Francisco Bay. This report includes data collected for the period January 2008 to December 2008 and extends a critical long-term biogeochemical record dating back to 1974. These data serve as the basis for the City of Palo Alto's Near-Field Receiving Water Monitoring Program, initiated in 1994. In 2008, metal concentrations in both sediments and clam tissue were among the lowest concentrations on record and consistent with results observed since 1991. Following significant reductions in the late 1980's, silver (Ag) and copper (Cu) concentrations appeared to have stabilized. Annual mean concentrations have fluctuated modestly (2–4 fold) in a nondirectional manner. Data for other metals, including chromium, mercury, nickel, selenium, vanadium, and zinc, have been collected since 1994. Over this period, concentrations of these elements, which more likely reflect regional inputs and systemwide processes, have remained relatively constant, aside from typical seasonal variation that is common to all elements. Within years, concentrations generally reach maximum in winter months (January–March) and decline to annual minima in spring through fall. Mercury (Hg) in sediments spiked to the highest observed level in January 2008. However, sedimentary concentrations for the rest of the year and concentrations of Hg in M. petalum for the entire year were consistent with data from previous years. Average selenium (Se) concentrations in sediment were the highest on record, but there is no evidence, yet, to suggest a temporal trend of increasing sedimentary Se. Selenium in M. petalum was not elevated relative to past years. Overall, Cu and Ag concentrations in sediments and soft tissues of the clam, M. petalum , remained representative of the concentrations observed since 1991 following significant reductions in the discharge of these elements from PARWQCP, suggesting that, similar to other elements of regulatory interest, regional scale factors now largely influence sedimentary and bioavailable concentrations of Cu and Ag. Analyses of the benthic-community structure of a mudflat in South San Francisco Bay over a 31-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 reproductive activity 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, with almost all animals initiating reproduction in the fall and spawning the following spring of most years. 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 suggests a more stable community that is subjected to less stress. 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. Heteromastus filiformis , a subsurface polychaete worm that lives in the sediment, consumes sediment and organic particles residing in the sediment, and reproduces by laying their eggs on or in the sediment, has shown a concurrent increase in dominance and is now showing signs of population stability. 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, which is indicative that the disturbance was not due to a persistent toxin or due to anoxia. This event allows us to examine the response of the mudflat benthic community to a natural disturbance (possible causes include sediment accretion or freshwater inundation) and compare this recovery to the longer term recovery we observed in the 1970s.

California↗
USGS2008

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: 2007

Results reported herein include trace element concentrations in sediment and in the clam Macoma petalum (formerly reported as Macoma balthica (Cohen and Carlton 1995)), clam reproductive activity, and benthic macroinvertebrate community structure for a mudflat one kilometer south of the discharge of the Palo Alto Regional Water Quality Control Plant in South San Francisco Bay. This report includes data collected for the period January 2007 to December 2007, and extends a critical long-term biogeochemical record dating back to 1974. These data serve as the basis for the City of Palo Alto’s Near-Field Receiving Water Monitoring Program, initiated in 1994. Metal concentrations in both sediments and clam tissue during 2007 remained consistent with results observed since 1990. Most notably, copper and silver concentrations in sediment and clam tissue are elevated for the second consecutive year, but the values remain well within the range of past findings. Other metals such as chromium, nickel, vanadium, and zinc remained relatively constant throughout the year except for maximum values that generally occur in winter months (January-March). Mercury levels in sediment and clam tissue were some of the lowest seen on record. Last year’s elevated selenium levels appear to be transient, and selenium concentrations have returned to background levels. Overall, metal concentrations in sediments and tissue remain within past findings. Analyses of the benthic-community structure of a mudflat in South San Francisco Bay over a 31-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 reproductive activity 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, with almost all animals initiating reproduction in the fall and spawning the following spring of most years. 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 suggests a more stable community that is subjected to less stress. 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. Heteromastus filiformis , a subsurface polychaete worm that lives in the sediment, consumes sediment and organic particles residing in the sediment, and reproduces by laying their eggs on or in the sediment, has shown a concurrent increase in dominance and is now showing signs of population stability. These changes in species dominance reflect a change in the community from one dominated by surface dwelling, brooding species to one with species with varying life history characteristics.

California↗
USGS2007

Using biodynamic models to reconcile differences between laboratory toxicity tests and field biomonitoring with aquatic insects

Aquatic insects often dominate lotic ecosystems, yet these organisms are under-represented in trace metal toxicity databases. Furthermore, toxicity data for aquatic insects do not appear to reflect their actual sensitivities to metals in nature, because the concentrations required to elicit toxicity in the laboratory are considerably higher than those found to impact insect communities in the field. New approaches are therefore needed to better understand how and why insects are differentially susceptible to metal exposures. Biodynamic modeling is a powerful tool for understanding interspecific differences in trace metal bioaccumulation. Because bioaccumulation alone does not necessarily correlate with toxicity, we combined biokinetic parameters associated with dissolved cadmium exposures with studies of the subcellular compartmentalization of accumulated Cd. This combination of physiological traits allowed us to make predictions of susceptibility differences to dissolved Cd in three aquatic insect taxa: Ephemerella excrucians , Rhithrogena morrisoni , and Rhyacophila sp. We compared these predictions with long-term field monitoring data and toxicity tests with closely related taxa: Ephemerella infrequens , Rhithrogena hageni , and Rhyacophila brunea. Kinetic parameters allowed us to estimate steady-state concentrations, the time required to reach steady state, and the concentrations of Cd projected to be in potentially toxic compartments for different species. Species-specific physiological traits identified using biodynamic models provided a means for better understanding why toxicity assays with insects have failed to provide meaningful estimates for metal concentrations that would be expected to be protective in nature.

Environmental Science & Technology↗
USGS2007

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--2006

Results reported herein include trace element concentrations in sediment and in the clam Macoma petalum (formerly reported as Macoma balthica (Cohen and Carlton 1995)), clam reproductive activity, and benthic macroinvertebrate community structure for a mudflat one kilometer south of the discharge of the Palo Alto Regional Water Quality Control Plant in South San Francisco Bay. This report includes data collected for the period January 2006 to December 2006, and extends a critical long-term biogeochemical record dating back to 1974. These data serve as the basis for the City of Palo Alto's Near-Field Receiving Water Monitoring Program, initiated in 1994. Metal concentrations in both sediments and clam tissue during 2006 were consistent with results observed since 1990. Most notably, copper and silver concentrations in sediment and clam tissue increased in the last year but the values remain well within range of past data. Other metals such as chromium, nickel, vanadium, and zinc remained relatively constant throughout the year except for maximum values generally occurring in winter months (January-March). Mercury levels in sediment and clam tissue were some of the lowest seen on record. Conversely, selenium concentrations reached a maximum level but soon returned to baseline levels. In all, metal concentrations in sediments and tissue remain within past findings. There are no obvious directional trends (increasing or decreasing). Analyses of the benthic-community structure of a mudflat in South San Francisco Bay over a 31-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 reproductive activity 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, with almost all animals initiating reproduction in the fall and spawning the following spring of most years. 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 suggests a more stable community that is subjected to less stress. 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. Heteromastus filiformis, a subsurface polychaete worm that lives in the sediment, consumes sediment and organic particles residing in the sediment, and reproduces by laying their eggs on or in the sediment, has shown a concurrent increase in dominance. These changes in species dominance reflect a change in the community from one dominated by surface dwelling, brooding species to one with species with varying life history characteristics. For the first time since its invasion in 1986, the non-indigenous filter-feeding clam Corbula (Potamocorbula) amurensis has shown up in small, but persistent, numbers in the benthic community.

California↗
USGS2006

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: 2005

Trace elements in sediment and the clam Macoma petalum (formerly reported as Macoma balthica (Cohen and Carlton 1995)), clam reproductive activity and benthic, macroinvertebrate community structure are reported for a mudflat one kilometer south of the discharge of the Palo Alto Regional Water Quality Control Plant in South San Francisco Bay. This report includes data collected for the period January to December 2005, and extends a critical long-term biogeochemical record dating back to 1974. These data serve as the basis for the City of Palo Alto’s Near-Field Receiving Water Monitoring Program, initiated in 1994. Metal concentrations in both sediments and clam tissue during 2005 were consistent with results observed since 1990. Copper and zinc concentrations in sediment and bivalve tissue displayed a continued decrease over the last decade. In 2005, Cu concentrations were at or below the effects range-low (ERL) concentration (34 µg/g) for the entire year, the first time this has been observed. Also, zinc concentrations never exceeded the ERL (150 µg/g). Yearly average concentrations of copper, zinc and silver in Macoma petalum for 2005 were some of the lowest recorded since monitoring for metals began in 1975. The concentrations of mercury and selenium in sediments, during April and January 2004, respectively, were the highest values observed for these elements during this study. Later in 2005, concentrations decreased to historic levels. The increase in mercury and selenium in 2004 was not a permanent trend and concentrations of these elements in sediments and clams at Palo Alto remain similar to concentrations observed elsewhere in the San Francisco Bay. Analyses of the benthic-community structure of a mudflat in South San Francisco Bay over a 31-year period show that changes in the community have occurred concurrent with with reduced concentrations of metals in the sediment and in the tissues of the biosentinal clam Macoma petalum from the same area. Analysis of the reproductive activity 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 with almost all animals initiating reproduction in the fall and spawning the following spring of most years. 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 suggests a more stable community that is subjected to less stress. 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. Heteromastus filiformis , a subsurface polychaete worm that lives in the sediment, consumes sediment and organic particles residing in the sediment, and reproduces by laying their eggs on or in the sediment has shown a concurrent increase in dominance. These changes in species dominance reflect a change in the community from one dominated by surface dwelling, brooding species to one with species with varying life history characteristics. For the first time since its invasion in 1986, the non-indigenous filter-feeding bivalve Corbula ( Potamocorbula ) amurensis has shown up in small but persistent numbers in the benthic community.

California↗
USGS2004

Linking metal bioaccumulation of aquatic insects to their distribution patterns in a mining-impacted river

Although the differential responses of stream taxa to metal exposure have been exploited for bioassessment and monitoring, the mechanisms affecting these responses are not well understood. In this study, the subcellular partitioning of metals in operationally defined metal-sensitive and detoxified fractions were analyzed in five insect taxa. Samples were collected in two separate years along an extensive metal contamination gradient in the Clark Fork River (MT, USA) to determine if interspecific differences in the metal concentrations of metal-sensitive fractions and detoxified fractions were linked to the differences in distributions of taxa relative to the gradient. Most of the Cd, Cu, and Zn body burdens were internalized and potentially biologically active in all taxa, although all taxa appeared to detoxify metals (e.g., metal bound to cytosolic metal-binding proteins). Metal concentrations associated with metal-sensitive fractions were highest in the mayflies Epeorus albertae and Serratella tibialis , which were rare or absent from the most contaminated sites but occurred at less contaminated sites. Relatively low concentrations of Cu were common to the tolerant taxa Hydropsyche spp. and Baetis spp., which were widely distributed and dominant in the most contaminated sections of the river. This suggested that distributions of taxa along the contamination gradient were more closely related to the bioaccumulation of Cu than of other metals. Metal bioaccumulation did not appear to explain the spatial distribution of the caddisfly Arctopsyche grandis , considered to be a bioindicator of metal effects in the river. Thus, in this system the presence/absence of most of these taxa from sites where metal exposure was elevated could be differentiated on the basis of differences in metal bioaccumulation.

Montana↗
USGS2004

Near field receiving water monitoring of trace metals in clams (macoma balthica) and sediments near the Palo Alto Water Quality Control Plant in South San Francisco Bay, California: 2000

Trace element concentrations were analyzed on samples of fine-grained sediments and clams (Macoma balthica) collected from a mudflat one kilometer south of the discharge of the Palo Alto Regional Water Quality Control Plant in South San Francisco Bay. This report serves as a continuation of the Near Field Receiving Water Monitoring Study, which was started in 1994. The data for 2003, herein, are interpreted within that context. Metal concentrations in both sediments and clam tissue samples have been within the range of values produced by seasonal variability; however, copper and zinc, display continued decreases over the last decade. In 2003, copper in sediment was observed to drop below the ERL (Effects Range-Low) concentration for the third consecutive year and zinc concentrations never exceeded the ERL. Yearly average concentrations of copper, zinc and silver in Macoma balthica for 2003 are some of the lowest recorded since monitoring began in 1975. Mercury and selenium concentrations in sediments and clams at Palo Alto were similar to concentrations observed elsewhere in the San Francisco Bay.

California↗
USGS2003

Near field receiving water monitoring of trace metals in clams (Macoma balthica) and sediments near the Palo Alto water quality control plant in south San Francisco Bay, California: 2002

This report presents trace element concentrations analyzed on samples of fine-grained sediments and clams (Macoma balthica) collected from a mudflat one kilometer south of the discharge of the Palo Alto Regional Water Quality Control Plant in South San Francisco Bay. This report serves as a continuation of the Near Field Receiving Water Monitoring Study, which was started in 1994. The data for 2002, herein, are interpreted within that context. Metal concentrations in both sediments and clam tissue samples have been within the range of values produced by seasonal variability. However, copper and zinc, display continued decreases. Copper in sediment was observed to drop below the ERL (Effects Range-Low) concentration for the third consecutive year and zinc concentrations never exceeded the ERL. Yearly average concentrations of copper, zinc and silver in Macoma balthica for 2002 are some of the lowest recorded since monitoring began in 1975. Mercury and selenium concentrations in sediments and clams at Palo Alto were similar concentrations observed elsewhere in the San Francisco Bay.

California↗
USGS2002

Near field receiving water monitoring of trace metals in clams (macoma balthica) and sediments near the Palo Alto Water Quality Control Plant in South San Francisco Bay, California: 1999-2001

This report presents trace element concentrations analyzed on samples of fine-grained sediments and clams (Macoma balthica) collected from a mudflat one kilometer south of the discharge of the Palo Alto Regional Water Quality Control Plant in South San Francisco Bay. This report serves as a continuation of the Near Field Receiving Water Monitoring Study which was started in 1994. The data for 1999-2001 are interpreted within that context. Generally, metal concentrations in both sediments and clam tissue samples have been within the range of values produced by seasonal variability. Copper and zinc, however, display a continued decrease, recording the lowest winter maxima concentrations in both sediment and tissue samples in 2001. Yearly average of bioavailable copper, zinc and silver concentrations in 1999-2001 are some of the lowest recorded since monitoring began in 1975. A slight increase in mercury in sediments and selenium in tissue in early 2001 are also observed. These enrichments are believed to be mainly caused by hydrogeologic processes affecting the area although only continued sampling will confirm whether anthropogenic sources influence the concentrations of these elements.

Open-File Report↗
USGS2000

Metal exposure in a benthic macroinvertebrate, Hydropsyche californica, related to mine drainage in the Sacramento River

A biomonitoring technique was employed to complement studies of metal transport in the upper Sacramento River affected by acid mine drainage. Metals (Al, Cd, Cu, Fe, Hg, Pb, and Zn) were determined in a resident invertebrate, Hydropsyche californica (Insecta: Trichoptera), and streambed sediments (<62 µm) to assess metal contamination within a 111-km section of the river downstream of the mining area. Metals in H. californica also were interpreted to be broadly indicative of metal exposure in fish. Total Hg was determined in the whole body of the insect, whereas Al, Cd, Cu, Fe, Pb, and Zn were additionally separated into operationally defined cytosolic (used as an indicator of exposure to bioavailable metal) and particulate fractions. Total concentrations of Cd, Cu, Hg, Pb, and Zn in sediments were consistent with documented upstream sources of acid mine drainage. Metal distribution patterns in H. californica and sediments were generally consistent for Cd, Cu, and Pb but inconsistent for Hg and Zn. Concentrations in H. californica indicated that bioavailable Cd, Cu, Pb, and Zn was transported at least 120 km downstream of the mine sources. Zinc in H. californica was elevated, but unlike sediments, did not decrease downstream. Mercury in H. californica was not elevated.

California↗