Howes Brian L.

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Howes
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Brian L.
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  • Article
    Nitrogen interception and export by experimental salt marsh plots exposed to chronic nutrient addition
    (Inter-Research, 2010-02-11) Brin, Lindsay D. ; Valiela, Ivan ; Goehringer, Dale ; Howes, Brian L.
    Mass balance studies conducted in the 1970s in Great Sippewissett Salt Marsh, New England, showed that fertilized plots intercepted 60 to 80% of the nitrogen (N) applied at several treatment levels every year from April to October, where interception mechanisms include plant uptake, denitrification and burial. These results pointed out that salt marshes are able to intercept land-derived N that could otherwise cause eutrophication in coastal waters. To determine the long-term N interception capacity of salt marshes and to assess the effect of different levels of N input, we measured nitrogenous materials in tidal water entering and leaving Great Sippewissett experimental plots in the 2007 growing season. Our results, from sampling over both full tidal cycles and more intensively sampled ebb tides, indicate high interception of externally added N. Tidal export of dissolved inorganic N (DIN) was small, although it increased with tide height and at high N input rates. NH4+ export was generally 2 to 3 times NO3– export, except at the highest N addition, where DIN export was evenly partitioned between NO3– and NH4+. Exports of dissolved organic N were not enhanced by N addition. Overall, export of added N was very small, <7% for all treatments, which is less than earlier estimates. Apparent enhanced tidal export of N from N-amended plots ceased when N additions ended in the fall. Nitrogen cycling within the vegetated marsh appears to limit N export, such that interception of added N remains high even after over 3 decades of external N inputs.
  • Article
    Coupled nitrification–denitrification measured in situ in a Spartina alterniflora marsh with a 15NH4+ tracer
    (Inter-Research, 2005-09-01) Hamersley, Michael R. ; Howes, Brian L.
    Measurements of N losses by denitrification from saltmarsh sediments have proved difficult because of the importance of plant metabolism and tidal cycles to sediment N cycling. In vitro approaches often do not measure the dominant coupled nitrification–denitrification pathway and/or alter in situ plant growth and redox conditions. We developed an in situ 15NH4+ tracer approach to measure coupled nitrification–denitrification fluxes in an undisturbed New England Spartina alterniflora saltmarsh. The tracer was line-injected into sediments underlying natural S. alterniflora stands and in similar areas receiving long-term N amendment (up to 11.2 mol organic N m–2 yr–1 for 16 to 23 yr), and 15N retention and loss routes were followed for 1 to 5 d. Denitrification losses in unfertilized grass stands ranged from 0.4 to 11.9 mmol N m–2 d–1 (0.77 ± 0.18 mol N m–2 yr–1). Denitrification in unfertilized sediments remained low until late summer, but underwent a ca. 4-fold increase in August and September, although sediment temperatures and respiration rates were high throughout the summer. Plant N uptake may limit the availability of N to support denitrification during the early summer, and denitrification may be released from competition with plant uptake in late summer, when plant growth slows. Denitrification rates in fertilized areas ranged from 22 to 77 mmol N m–2 d–1 (10.5 ± 4.9 mol N m–2 yr–1), and denitrification was likely controlled by the availability of fertilizer N rather than by competition with plants, since N was added in excess of plant demand. Our results emphasize the importance of in situ measurements of denitrification in understanding the dynamics of saltmarsh N cycling.
  • Article
    Water quality measurements in Buzzards Bay by the Buzzards Bay Coalition Baywatchers Program from 1992 to 2018
    (Nature Research, 2021-03-05) Jakuba, Rachel W. ; Williams, Tony ; Neill, Christopher ; Costa, Joseph E. ; McHorney, Richard ; Scott, Lindsay ; Howes, Brian L. ; Ducklow, Hugh W. ; Erickson, Matthew ; Rasmussen, Mark
    The Buzzards Bay Coalition’s Baywatchers Monitoring Program (Baywatchers) collected summertime water quality information at more than 150 stations around Buzzards Bay, Massachusetts from 1992 to 2018. Baywatchers documents nutrient-related water quality and the effects of nitrogen pollution. The large majority of stations are located in sub-estuaries of the main Bay, although stations in central Buzzards Bay and Vineyard Sound were added beginning in 2007. Measurements include temperature, salinity, Secchi depth and concentrations of dissolved oxygen, ammonium, nitrate + nitrite, total dissolved nitrogen, particulate organic nitrogen, particulate organic carbon, ortho-phosphate, chlorophyll a, pheophytin a, and in lower salinity waters, total phosphorus and dissolved organic carbon. The Baywatchers dataset provides a long-term record of the water quality of Buzzards Bay and its sub-estuaries. The data have been used to identify impaired waters, evaluate discharge permits, support the development of nitrogen total maximum daily loads, develop strategies for reducing nitrogen inputs, and increase public awareness and generate support for management actions to control nutrient pollution and improve water quality.
  • Article
    Response of benthic metabolism and nutrient cycling to reductions in wastewater loading to Boston Harbor, USA
    (Elsevier, 2014-10-02) Tucker, Jane ; Giblin, Anne E. ; Hopkinson, Charles S. ; Kelsey, Samuel W. ; Howes, Brian L.
    We describe the long-term response of benthic metabolism in depositional sediments of Boston Harbor, MA, to large reductions in organic matter and nutrient loading. Although Boston Harbor received very high loadings of nutrients and solids it differs from many eutrophic estuaries in that severe hypoxia was prevented by strong tidal flushing. Our study was conducted for 9 years during which a series of improvements to sewage treatment were implemented, followed by 10 years after the culminating step in the clean-up, which was to divert all wastewater effluent offshore. Counter to expectations, sediment oxygen demand and nutrient effluxes initially increased at some stations, reaching some of the highest rates recorded in the literature, and were spatially and temporally quite variable. Early increases were attributed to macrofaunal effects, as sediments at some sites were rapidly colonized by tube-building amphipods, Ampelisca spp., which dominated a dense macrofaunal mat community. As reductions in loading progressed, however, mean rates in oxygen uptake and release of ammonium, nitrate, and phosphate all decreased. At the point of outfall diversion, rates and variability had already decreased substantially. By the end of the study, average oxygen uptake had decreased from 74 to 41 mmol m−2 d−1 and spatial and temporal variability had decreased. Similarly, nutrient fluxes were less than half the rates measured at the start of the project and also less variable. Other evidence of improved conditions included a decrease in the carbon content of sediments at most stations and higher Eh values at all stations, illustrating less reducing conditions. Denitrification also showed an overall decrease from the beginning to the end of the 19-year study, but was highest during the intermediate phases of the cleanup, reaching 9 mmol N m−2 d−1. At the end of the study denitrification averaged for all sites was 2.2 mmol N m−2 d−1, but when compared to current loadings, had become a more important overall sink for N within the harbor. Few long-term examinations of the responses of sediment biogeochemistry to reductions in nutrient and organic matter loading have been reported. Our findings demonstrate that benthic fluxes may respond to reductions in loading in complex ways, and sediments need not represent a long-term legacy that would impede ecosystems recovery.
  • Dataset
    Buzzards Bay Water Quality Data from the Buzzards Bay Coalition’s Baywatchers Program 1992-2018 August 2020 version
    (Woods Hole Oceanographic Institution, 2020-08-28) Jakuba, Rachel W. ; Williams, Tony ; Neill, Christopher ; Costa, Joseph E. ; McHorney, Richard ; Scott, Lindsay ; Howes, Brian L. ; Ducklow, Hugh W. ; Erickson, Matthew ; Rasmussen, Mark
    The Buzzards Bay Coalition’s Baywatchers Monitoring Program collected summertime water quality information at more than 150 stations around Buzzards Bay, Massachusetts from 1992 to 2018. Baywatchers monitoring data document nutrient-related water quality and the effects of nitrogen pollution. The large majority of stations are located in sub-estuaries of the main Bay, although stations in central Buzzards Bay and Vineyard Sound were added beginning in 2007. Measurements include temperature, salinity, Secchi depth and concentrations of dissolved oxygen, ammonium, nitrate + nitrite, total dissolved nitrogen, particulate organic nitrogen, particulate organic carbon, ortho-phosphate, chlorophyll a, pheophytin a, and in lower salinity waters, total phosphorus and dissolved organic carbon. The Baywatchers dataset provides a long-term record of the water quality of Buzzards Bay and its sub-estuaries. The data have been used to identify impaired waters, evaluate discharge permits, support the development of nitrogen total maximum daily loads, develop strategies for reducing nitrogen inputs, and increase public awareness and generate support for management actions to control nutrient pollution and improve water quality. The Readme, STN_EQUIV, Stations and Methods, S_D for WFH, and Acknowledge tabs were updated and corrections were made for Time and POC on 2018 Upper Bay samples and deleted CH1 from sonde method column where no CHL data existed, moved words like "sample lost" from Chl and Pheo data columns to comments column.
  • Dataset
    Buzzards Bay Water Quality Data from the Buzzards Bay Coalition’s Baywatchers Program 1992-2020
    (Woods Hole Oceanographic Institution, 2021-07-09) Jakuba, Rachel W. ; Williams, Tony ; Neill, Christopher ; Costa, Joseph E. ; McHorney, Richard ; Scott, Lindsay ; Howes, Brian L. ; Ducklow, Hugh W. ; Erickson, Matthew ; Rasmussen, Mark
    The Buzzards Bay Coalition’s Baywatchers Monitoring Program collected summertime water quality information at more than 150 stations around Buzzards Bay, Massachusetts from 1992 to 2020. Baywatchers monitoring data document nutrient-related water quality and the effects of nitrogen pollution. The large majority of stations are located in sub-estuaries of the main Bay, although stations in central Buzzards Bay and Vineyard Sound were added beginning in 2007. Measurements include temperature, salinity, Secchi depth and concentrations of dissolved oxygen, ammonium, nitrate + nitrite, total dissolved nitrogen, particulate organic nitrogen, particulate organic carbon, ortho-phosphate, chlorophyll a, pheophytin a, and in lower salinity waters, total phosphorus and dissolved organic carbon. The Baywatchers dataset provides a long-term record of the water quality of Buzzards Bay and its sub-estuaries. The data have been used to identify impaired waters, evaluate discharge permits, support the development of nitrogen total maximum daily loads, develop strategies for reducing nitrogen inputs, and increase public awareness and generate support for management actions to control nutrient pollution and improve water quality. The Readme, STN_EQUIV, Stations and Methods, S_D for WFH, and Acknowledge tabs were updated and corrections were made for Time and POC on 2018 Upper Bay samples and deleted CH1 from sonde method column where no CHL data existed, moved words like "sample lost" from Chl and Pheo data columns to comments column.
  • Dataset
    Buzzards Bay Water Quality Data from the Buzzards Bay Coalition’s Baywatchers Program 2021-2023
    (Woods Hole Oceanographic Institution, 2025-01-15) Jakuba, Rachel W. ; Williams, Tony ; Neill, Christopher ; Costa, Joseph E. ; McHorney, Richard ; Scott, Lindsay ; Howes, Brian L. ; Ducklow, Hugh W. ; Erickson, Matthew ; Rasmussen, Mark
    The Buzzards Bay Coalition’s Baywatchers Monitoring Program collected summertime water quality information at more than 150 stations around Buzzards Bay, Massachusetts from 1992 to 2023. Baywatchers monitoring data document nutrient-related water quality and the effects of nitrogen pollution. The large majority of stations are located in sub-estuaries of the main Bay, although stations in central Buzzards Bay and Vineyard Sound were added beginning in 2007. Measurements include temperature, salinity, Secchi depth and concentrations of dissolved oxygen, ammonium, nitrate + nitrite, total dissolved nitrogen, particulate organic nitrogen, particulate organic carbon, ortho-phosphate, chlorophyll a, pheophytin a, and in lower salinity waters, total phosphorus and dissolved organic carbon. The Baywatchers dataset provides a long-term record of the water quality of Buzzards Bay and its sub-estuaries. The data have been used to identify impaired waters, evaluate discharge permits, support the development of nitrogen total maximum daily loads, develop strategies for reducing nitrogen inputs, and increase public awareness and generate support for management actions to control nutrient pollution and improve water quality. The Readme, STN_EQUIV, Stations and Methods, S_D for WFH, and Acknowledge tabs were updated and corrections were made for Time and POC on 2018 Upper Bay samples and deleted CH1 from sonde method column where no CHL data existed, moved words like "sample lost" from Chl and Pheo data columns to comments column.
  • Dataset
    Buzzards Bay Water Quality Data from the Buzzards Bay Coalition’s Baywatchers Program 1992-2018
    (Woods Hole Oceanographic Institution, 2020-05-04) Jakuba, Rachel W. ; Williams, Tony ; Neill, Christopher ; Costa, Joseph E. ; McHorney, Richard ; Scott, Lindsay ; Howes, Brian L. ; Ducklow, Hugh W. ; Erickson, Matthew ; Rasmussen, Mark
    The Buzzards Bay Coalition’s Baywatchers Monitoring Program collected summertime water quality information at more than 150 stations around Buzzards Bay, Massachusetts from 1992 to 2018. Baywatchers monitoring data document nutrient-related water quality and the effects of nitrogen pollution. The large majority of stations are located in sub-estuaries of the main Bay, although stations in central Buzzards Bay and Vineyard Sound were added beginning in 2007. Measurements include temperature, salinity, Secchi depth and concentrations of dissolved oxygen, ammonium, nitrate + nitrite, total dissolved nitrogen, particulate organic nitrogen, particulate organic carbon, ortho-phosphate, chlorophyll a, pheophytin a, and in lower salinity waters, total phosphorus and dissolved organic carbon. The Baywatchers dataset provides a long-term record of the water quality of Buzzards Bay and its sub-estuaries. The data have been used to identify impaired waters, evaluate discharge permits, support the development of nitrogen total maximum daily loads, develop strategies for reducing nitrogen inputs, and increase public awareness and generate support for management actions to control nutrient pollution and improve water quality.
  • Dataset
    Buzzards Bay Water Quality Data from the Buzzards Bay Coalition’s Baywatchers Program 1992-2018 December 2020 version
    (Woods Hole Oceanographic Institution, 2020-12-08) Jakuba, Rachel W. ; Williams, Tony ; Neill, Christopher ; Costa, Joseph E. ; McHorney, Richard ; Scott, Lindsay ; Howes, Brian L. ; Ducklow, Hugh W. ; Erickson, Matthew ; Rasmussen, Mark
    The Buzzards Bay Coalition’s Baywatchers Monitoring Program collected summertime water quality information at more than 150 stations around Buzzards Bay, Massachusetts from 1992 to 2018. Baywatchers monitoring data document nutrient-related water quality and the effects of nitrogen pollution. The large majority of stations are located in sub-estuaries of the main Bay, although stations in central Buzzards Bay and Vineyard Sound were added beginning in 2007. Measurements include temperature, salinity, Secchi depth and concentrations of dissolved oxygen, ammonium, nitrate + nitrite, total dissolved nitrogen, particulate organic nitrogen, particulate organic carbon, ortho-phosphate, chlorophyll a, pheophytin a, and in lower salinity waters, total phosphorus and dissolved organic carbon. The Baywatchers dataset provides a long-term record of the water quality of Buzzards Bay and its sub-estuaries. The data have been used to identify impaired waters, evaluate discharge permits, support the development of nitrogen total maximum daily loads, develop strategies for reducing nitrogen inputs, and increase public awareness and generate support for management actions to control nutrient pollution and improve water quality. The Readme, STN_EQUIV, Stations and Methods, S_D for WFH, and Acknowledge tabs were updated and corrections were made for Time and POC on 2018 Upper Bay samples and deleted CH1 from sonde method column where no CHL data existed, moved words like "sample lost" from Chl and Pheo data columns to comments column.