Katherine Filippino | Old Dominion University (original) (raw)
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Papers by Katherine Filippino
Limnology and Oceanography, 2004
The cycling of the radiatively important gas carbonyl sulfide (OCS) was studied in surface waters... more The cycling of the radiatively important gas carbonyl sulfide (OCS) was studied in surface waters of the Sargasso Sea. In August 1999, surface OCS concentrations averaged 8.6 pmol L Ϫ1 , showed minor diel variations, and varied little with depth. An OCS precursor, total dissolved organic sulfur (DOS), was lowest at the surface (40 nmol L Ϫ1 ) and increased with depth. The photoproduction rate of OCS from in situ incubations averaged 9.6 pmol L Ϫ1 h Ϫ1 , whereas dark production was 7.0 pmol L Ϫ1 h Ϫ1 . Apparent quantum yields were 10 Ϫ5 -10 Ϫ7 from 313-436 nm and varied with the water depth irradiated. In March 2000, there were strong diel variations in surface OCS (highest in late afternoon; overall average, 16.9 pmol L Ϫ1 ). Depth profiles in the afternoon showed surface water maxima and decreases with depth, whereas DOS had a surface maximum of 419 nmol L Ϫ1 and decreased with depth. Dark production was 4.0 pmol L Ϫ1 h Ϫ1 . Modeling of the diel cycle suggested a photoproduction rate of 16.4 pmol L Ϫ1 h Ϫ1 . Overall, the photochemical production of OCS strongly depended on DOS and chromophoric dissolved organic matter, whereas dark production was influenced by the presence of particles and perhaps microbial respiration, showing a direct biotic influence on OCS cycling.
Estuaries and Coasts, 2011
Total maximum daily loads for nitrogen (N) are currently being established for the Chesapeake Bay... more Total maximum daily loads for nitrogen (N) are currently being established for the Chesapeake Bay watershed. While we know inorganic N is bioavailable in the environment and therefore its input contributes to cultural eutrophication, the bioavailability of organic N is unclear. Using bioassay experiments, we examined the impact of effluent-derived organic nitrogen (EON) from wastewater treatment plants on natural water samples collected along an estuarine/salinity gradient within the lower Chesapeake Bay watershed. All of the inorganic N and between 31% and 96% of the EON was removed during biotic bioassays within the first 2 days. Further, there was substantial abiotic reactivity of effluent N when it was added to natural water samples. Results demonstrate that organic and inorganic N in effluent is removed to support the growth of microbial communities. These are the first results aimed at assessing the reactivity of EON in natural waters along an estuarine/salinity gradient.
Environmental Science & Technology, 2010
The goal of this study was to investigate three potential ways that the soluble organic nitrogen ... more The goal of this study was to investigate three potential ways that the soluble organic nitrogen (N) fraction of wastewater treatment plant (WWTP) effluents, termed effluent organic N (EON), could contribute to coastal eutrophication -direct biological removal, photochemical release of labile compounds, and salinitymediated release of ammonium (NH 4 + ). Effluents from two WWTPs were used in the experiments. For the bioassays, EON was added to water from four salinities (∼0 to 30) collected from the James River (VA) in August 2008, and then concentrations of N and phosphorus compounds were measured periodically over 48 h. Bioassay results, based on changes in DON concentrations, indicate that some fraction of the EON was removed and that the degree of EON removal varied between effluents and with salinity. Further, we caution that bioassay results should be interpreted within a broad context of detailed information on chemical characterization. EON from both WWTPs was also photoreactive, with labile NH 4 + and dissolved primary amines released during exposure to sunlight. We also present the first data that demonstrate that when EON is exposed to higher salinities, increasing amounts of NH 4 + are released, further facilitating EON use as effluent transits from freshwater through estuaries to the coast.
Estuaries and Coasts, 2009
To determine the effects of the Chesapeake Bay outflow plume on the coastal ocean, nutrient conce... more To determine the effects of the Chesapeake Bay outflow plume on the coastal ocean, nutrient concentrations and climatology were evaluated in conjunction with nitrogen (N) and carbon (C) uptake rates during a 3-year field study. Sixteen cruises included all seasons and captured high- and low-flow freshwater input scenarios. Event-scale disturbances in freshwater flow and wind speed and direction strongly influenced the location and type of plume present and thus the biological uptake of N and C. As expected, volumetric primary productivity rates did not always correlate with chlorophyll a concentrations, suggesting that high freshwater flow does not translate into high productivity in the coastal zone; rather, high productivity was observed during periods where recycling processes may have dominated. Results suggest that timing of meteorological events, with respect to upwelling or downwelling favorable conditions, plays a crucial role in determining the impact of the estuarine plume on the coastal ocean.
Estuaries and Coasts, 2009
During August and September 2007, the lower Chesapeake Bay and its tributaries experienced a mass... more During August and September 2007, the lower Chesapeake Bay and its tributaries experienced a massive bloom of Cochlodinium polykrikoides Margalef (>104 cells per milliliter) that persisted for over a month, was extremely patchy, and at times penetrated into the Atlantic Ocean. The onset of the bloom coincided with a period of intense rainfall and stormwater runoff after a protracted summer drought period. Genetic evidence showed this species to be distinct from many Asian strains but similar to other North American strains. Populations dominated by C. polykrikoides took up a variety of nitrogenous compounds to support their growth and were able to mobilize additional sources of organic nutrients through peptide hydrolysis. Bioassays determined that C. polykrikoides exerted a lethal affect on juvenile fish and shellfish, causing 100% mortality of juvenile fish (Cyprinodon variegates) in less than 24 h and 20% mortality in juvenile American oysters (~21 mm; Crassostrea virginica) within 72 h.
Remote Sensing of Environment
Satellite imagery has proven to be a powerful tool for measuring chlorophyll a in surface waters.... more Satellite imagery has proven to be a powerful tool for measuring chlorophyll a in surface waters. While this provides an estimate of total phytoplankton biomass, it does not distinguish between phytoplankton groups, many of which have functional differences and therefore affect biogeochemical cycles differently. Phytoplankton pigment analysis has been used to quantify a wide range of photosynthetic and accessory pigments, and chemotaxonomic analysis (e.g. CHEMTAX) has been used to successfully quantify functional taxonomic groups in nature based on pigment distributions. Here, we combine CHEMTAX analysis with satellite-derived distributions of specific phytoplankton pigments to describe the distributions of particular components of the phytoplankton community in the northeast coast of the United States from space. The spatial and seasonal variations in phytoplankton community structure elucidated through satellite remote sensing methods generally agreed with observations of abundance estimates of cell counts. Diatoms were generally the most abundant phytoplankton in this region, especially during Winter-Spring and in the inner shelf, but phytoplankton populations shifted to increasing abundance of other taxa during Summer, especially offshore. While still preliminary, satellite-derived taxa-specific information with proper regional controls holds promise for providing information on phytoplankton abundance to a taxonomic group level which would greatly improve our understanding of the impacts of human activity and climate change on ecosystems.
Estuarine Coastal and Shelf Science, 2011
a b s t r a c t Nutrient concentrations, primary productivity, and nitrogen uptake rates were mea... more a b s t r a c t Nutrient concentrations, primary productivity, and nitrogen uptake rates were measured in coastal waters of the Mid-Atlantic Bight over a two-year period that included measurements from all four seasons. In order to assess carbon productivity and nitrogen demand within the context of the physical environment, the region was divided into three distinct hydrographic regimes: the Chesapeake and Delaware Bay outflow plumes (PL), the southern Mid-Atlantic shelf influenced by the Gulf Stream (SS), and the mid-shelf area to the north of the Chesapeake Bay mouth (MS). Annual areal rates of total nitrogen (N) uptake were similar across all regions (10.9 AE 2.1 mol N m À2 y À1 ). However, annual areal rates of net primary productivity were higher in the outflow plume region (43 mol C m À2 y À1 ), than along the Mid-Atlantic shelf and in areas influenced by the Gulf Stream (41 and 34 mol C m À2 y À1 , respectively). Rates of net primary productivity were not well correlated with Chl a concentrations and were uncoupled with net N uptake rates. Seasonally averaged annual areal rates of net primary productivity for the Mid-Atlantic Bight measured in this study were higher than those calculated in previous decades and provide important validation information for biogeochemical models and satellite remote sensing algorithms developed for the region.
Estuarine Coastal and Shelf Science, 2011
Nutrient concentrations, primary productivity, and nitrogen uptake rates were measured in coastal... more Nutrient concentrations, primary productivity, and nitrogen uptake rates were measured in coastal waters of the Mid-Atlantic Bight over a two-year period that included measurements from all four seasons. In order to assess carbon productivity and nitrogen demand within the context of the physical environment, the region was divided into three distinct hydrographic regimes: the Chesapeake and Delaware Bay outflow plumes (PL), the southern Mid-Atlantic shelf influenced by the Gulf Stream (SS), and the mid-shelf area to the north of the Chesapeake Bay mouth (MS). Annual areal rates of total nitrogen (N) uptake were similar across all regions (10.9 ± 2.1 mol N m -2 y -1). However, annual areal rates of net primary productivity were higher in the outflow plume region (43 mol C m -2 y -1), than along the Mid-Atlantic shelf and in areas influenced by the Gulf Stream (41 and 34 mol C m -2 y -1, respectively). Rates of net primary productivity were not well correlated with Chl a concentrations and were uncoupled with net N uptake rates. Seasonally averaged annual areal rates of net primary productivity for the Mid-Atlantic Bight measured in this study were higher than those calculated in previous decades and provide important validation information for biogeochemical models and satellite remote sensing algorithms developed for the region.
Limnology and Oceanography, 2004
The cycling of the radiatively important gas carbonyl sulfide (OCS) was studied in surface waters... more The cycling of the radiatively important gas carbonyl sulfide (OCS) was studied in surface waters of the Sargasso Sea. In August 1999, surface OCS concentrations averaged 8.6 pmol L Ϫ1 , showed minor diel variations, and varied little with depth. An OCS precursor, total dissolved organic sulfur (DOS), was lowest at the surface (40 nmol L Ϫ1 ) and increased with depth. The photoproduction rate of OCS from in situ incubations averaged 9.6 pmol L Ϫ1 h Ϫ1 , whereas dark production was 7.0 pmol L Ϫ1 h Ϫ1 . Apparent quantum yields were 10 Ϫ5 -10 Ϫ7 from 313-436 nm and varied with the water depth irradiated. In March 2000, there were strong diel variations in surface OCS (highest in late afternoon; overall average, 16.9 pmol L Ϫ1 ). Depth profiles in the afternoon showed surface water maxima and decreases with depth, whereas DOS had a surface maximum of 419 nmol L Ϫ1 and decreased with depth. Dark production was 4.0 pmol L Ϫ1 h Ϫ1 . Modeling of the diel cycle suggested a photoproduction rate of 16.4 pmol L Ϫ1 h Ϫ1 . Overall, the photochemical production of OCS strongly depended on DOS and chromophoric dissolved organic matter, whereas dark production was influenced by the presence of particles and perhaps microbial respiration, showing a direct biotic influence on OCS cycling.
Estuaries and Coasts, 2011
Total maximum daily loads for nitrogen (N) are currently being established for the Chesapeake Bay... more Total maximum daily loads for nitrogen (N) are currently being established for the Chesapeake Bay watershed. While we know inorganic N is bioavailable in the environment and therefore its input contributes to cultural eutrophication, the bioavailability of organic N is unclear. Using bioassay experiments, we examined the impact of effluent-derived organic nitrogen (EON) from wastewater treatment plants on natural water samples collected along an estuarine/salinity gradient within the lower Chesapeake Bay watershed. All of the inorganic N and between 31% and 96% of the EON was removed during biotic bioassays within the first 2 days. Further, there was substantial abiotic reactivity of effluent N when it was added to natural water samples. Results demonstrate that organic and inorganic N in effluent is removed to support the growth of microbial communities. These are the first results aimed at assessing the reactivity of EON in natural waters along an estuarine/salinity gradient.
Environmental Science & Technology, 2010
The goal of this study was to investigate three potential ways that the soluble organic nitrogen ... more The goal of this study was to investigate three potential ways that the soluble organic nitrogen (N) fraction of wastewater treatment plant (WWTP) effluents, termed effluent organic N (EON), could contribute to coastal eutrophication -direct biological removal, photochemical release of labile compounds, and salinitymediated release of ammonium (NH 4 + ). Effluents from two WWTPs were used in the experiments. For the bioassays, EON was added to water from four salinities (∼0 to 30) collected from the James River (VA) in August 2008, and then concentrations of N and phosphorus compounds were measured periodically over 48 h. Bioassay results, based on changes in DON concentrations, indicate that some fraction of the EON was removed and that the degree of EON removal varied between effluents and with salinity. Further, we caution that bioassay results should be interpreted within a broad context of detailed information on chemical characterization. EON from both WWTPs was also photoreactive, with labile NH 4 + and dissolved primary amines released during exposure to sunlight. We also present the first data that demonstrate that when EON is exposed to higher salinities, increasing amounts of NH 4 + are released, further facilitating EON use as effluent transits from freshwater through estuaries to the coast.
Estuaries and Coasts, 2009
To determine the effects of the Chesapeake Bay outflow plume on the coastal ocean, nutrient conce... more To determine the effects of the Chesapeake Bay outflow plume on the coastal ocean, nutrient concentrations and climatology were evaluated in conjunction with nitrogen (N) and carbon (C) uptake rates during a 3-year field study. Sixteen cruises included all seasons and captured high- and low-flow freshwater input scenarios. Event-scale disturbances in freshwater flow and wind speed and direction strongly influenced the location and type of plume present and thus the biological uptake of N and C. As expected, volumetric primary productivity rates did not always correlate with chlorophyll a concentrations, suggesting that high freshwater flow does not translate into high productivity in the coastal zone; rather, high productivity was observed during periods where recycling processes may have dominated. Results suggest that timing of meteorological events, with respect to upwelling or downwelling favorable conditions, plays a crucial role in determining the impact of the estuarine plume on the coastal ocean.
Estuaries and Coasts, 2009
During August and September 2007, the lower Chesapeake Bay and its tributaries experienced a mass... more During August and September 2007, the lower Chesapeake Bay and its tributaries experienced a massive bloom of Cochlodinium polykrikoides Margalef (>104 cells per milliliter) that persisted for over a month, was extremely patchy, and at times penetrated into the Atlantic Ocean. The onset of the bloom coincided with a period of intense rainfall and stormwater runoff after a protracted summer drought period. Genetic evidence showed this species to be distinct from many Asian strains but similar to other North American strains. Populations dominated by C. polykrikoides took up a variety of nitrogenous compounds to support their growth and were able to mobilize additional sources of organic nutrients through peptide hydrolysis. Bioassays determined that C. polykrikoides exerted a lethal affect on juvenile fish and shellfish, causing 100% mortality of juvenile fish (Cyprinodon variegates) in less than 24 h and 20% mortality in juvenile American oysters (~21 mm; Crassostrea virginica) within 72 h.
Remote Sensing of Environment
Satellite imagery has proven to be a powerful tool for measuring chlorophyll a in surface waters.... more Satellite imagery has proven to be a powerful tool for measuring chlorophyll a in surface waters. While this provides an estimate of total phytoplankton biomass, it does not distinguish between phytoplankton groups, many of which have functional differences and therefore affect biogeochemical cycles differently. Phytoplankton pigment analysis has been used to quantify a wide range of photosynthetic and accessory pigments, and chemotaxonomic analysis (e.g. CHEMTAX) has been used to successfully quantify functional taxonomic groups in nature based on pigment distributions. Here, we combine CHEMTAX analysis with satellite-derived distributions of specific phytoplankton pigments to describe the distributions of particular components of the phytoplankton community in the northeast coast of the United States from space. The spatial and seasonal variations in phytoplankton community structure elucidated through satellite remote sensing methods generally agreed with observations of abundance estimates of cell counts. Diatoms were generally the most abundant phytoplankton in this region, especially during Winter-Spring and in the inner shelf, but phytoplankton populations shifted to increasing abundance of other taxa during Summer, especially offshore. While still preliminary, satellite-derived taxa-specific information with proper regional controls holds promise for providing information on phytoplankton abundance to a taxonomic group level which would greatly improve our understanding of the impacts of human activity and climate change on ecosystems.
Estuarine Coastal and Shelf Science, 2011
a b s t r a c t Nutrient concentrations, primary productivity, and nitrogen uptake rates were mea... more a b s t r a c t Nutrient concentrations, primary productivity, and nitrogen uptake rates were measured in coastal waters of the Mid-Atlantic Bight over a two-year period that included measurements from all four seasons. In order to assess carbon productivity and nitrogen demand within the context of the physical environment, the region was divided into three distinct hydrographic regimes: the Chesapeake and Delaware Bay outflow plumes (PL), the southern Mid-Atlantic shelf influenced by the Gulf Stream (SS), and the mid-shelf area to the north of the Chesapeake Bay mouth (MS). Annual areal rates of total nitrogen (N) uptake were similar across all regions (10.9 AE 2.1 mol N m À2 y À1 ). However, annual areal rates of net primary productivity were higher in the outflow plume region (43 mol C m À2 y À1 ), than along the Mid-Atlantic shelf and in areas influenced by the Gulf Stream (41 and 34 mol C m À2 y À1 , respectively). Rates of net primary productivity were not well correlated with Chl a concentrations and were uncoupled with net N uptake rates. Seasonally averaged annual areal rates of net primary productivity for the Mid-Atlantic Bight measured in this study were higher than those calculated in previous decades and provide important validation information for biogeochemical models and satellite remote sensing algorithms developed for the region.
Estuarine Coastal and Shelf Science, 2011
Nutrient concentrations, primary productivity, and nitrogen uptake rates were measured in coastal... more Nutrient concentrations, primary productivity, and nitrogen uptake rates were measured in coastal waters of the Mid-Atlantic Bight over a two-year period that included measurements from all four seasons. In order to assess carbon productivity and nitrogen demand within the context of the physical environment, the region was divided into three distinct hydrographic regimes: the Chesapeake and Delaware Bay outflow plumes (PL), the southern Mid-Atlantic shelf influenced by the Gulf Stream (SS), and the mid-shelf area to the north of the Chesapeake Bay mouth (MS). Annual areal rates of total nitrogen (N) uptake were similar across all regions (10.9 ± 2.1 mol N m -2 y -1). However, annual areal rates of net primary productivity were higher in the outflow plume region (43 mol C m -2 y -1), than along the Mid-Atlantic shelf and in areas influenced by the Gulf Stream (41 and 34 mol C m -2 y -1, respectively). Rates of net primary productivity were not well correlated with Chl a concentrations and were uncoupled with net N uptake rates. Seasonally averaged annual areal rates of net primary productivity for the Mid-Atlantic Bight measured in this study were higher than those calculated in previous decades and provide important validation information for biogeochemical models and satellite remote sensing algorithms developed for the region.