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  • 1
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    Effects of watershed land use on nitrogen concentrations and δ15 Nitrogen in groundwater (2006)
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    Publication Date: 2022-05-25
    Description: Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Biogeochemistry 77 (2006): 199-215, doi:10.1007/s10533-005-1036-2.
    Description: Eutrophication is a major agent of change affecting freshwater, estuarine, and marine systems. It is largely driven by transportation of nitrogen from natural and anthropogenic sources. Research is needed to quantify this nitrogen delivery and to link the delivery to specific land-derived sources. In this study we measured nitrogen concentrations and δ15N values in seepage water entering three freshwater ponds and six estuaries on Cape Cod, Massachusetts and assessed how they varied with different types of land use. Nitrate concentrations and δ15N values in groundwater reflected land use in developed and pristine watersheds. In particular, watersheds with larger populations delivered larger nitrate loads with higher δ15N values to receiving waters. The enriched δ15N values confirmed nitrogen loading model results identifying wastewater contributions from septic tanks as the major N source. Furthermore, it was apparent that N coastal sources had a relatively larger impact on the N loads and isotopic signatures than did inland N sources further upstream in the watersheds. This finding suggests that management priorities could focus on coastal sources as a first course of action. This would require management constraints on a much smaller population.
    Description: This work was supported by funds from the Woods Hole Oceanographic Institution Sea Grant Program, from the Cooperative Institute for Coastal and Estuarine Environmental Technology, from Massachusetts Department of Environmental Protection to Applied Science Associates, Narragansett, RI, as well as from Palmer/McLeod and NOAA National Estuarine Research Reserve Fellowships to Kevin Kroeger. This work is the result of research sponsored by NOAA National Sea Grant College Program Office, Department of Commerce, under Grant No. NA86RG0075, Woods Hole Oceanographic Institution Sea Grant Project No. R/M-40.
    Keywords: Cape Cod ; Nitrogen ; Groundwater ; Stable isotopes ; Land use
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: 198655 bytes
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  • 2
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    Experimental assessment of the macroalgae Ascophyllum nodosum and Fucus vesiculosus for monitoring N sources at different time-scales using stable isotope composition (2015)
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    Publication Date: 2022-05-25
    Description: © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Journal of Experimental Marine Biology and Ecology 466 (2015): 24-33, doi:10.1016/j.jembe.2015.01.014.
    Description: Stable isotope composition of brown macroalgae has been widely used to monitor N loading during the last decades but some of the required assumptions when using them to detect anthropogenic inputs remain untested. In this study several experiments were run with two key species, A. nodosum and F. vesiculosus, to determine internal nitrogen isotope dynamics. First, the equilibration of the isotopic values of the different parts of the thallus of these species was tested by growing them under different water sources. Then, nitrate uptake capacity and N transport along the frond were tested by 15N enrichment experiments. The results indicate that although the growing tips had the highest uptake rates, older parts of the frond of both species have the capacity to incorporate N at low rates. No evidence of N transport along the thallus, from the tip to the basal segment of the frond or the converse was found. These results show that the growing tips of these macroalgae can be used to monitor N loadings at time scales from weeks (F. vesiculosus) to months (A. nodosum). The use of non-growing parts of the thallus to do retrospective studies cannot be recommended because of their measurable exchange of N with the surrounding water.
    Description: This research was funded by projects ANILE (CTM2009-08396 and CTM2010-09904-E) of the Plan Nacional de I+D+I (Spain) and RADIALES of the Instituto Español de Oceanografía (Spain). I.G.V. was supported by a FPI fellowship from Ministerio de Economía y Competitividad (Spain).
    Keywords: Stable isotopes ; Enrichment ; Growth rate ; Phaeophyceae ; DIN
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 3
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    Impact of burrowing crabs on C and N sources, control, and transformations in sediments andfood webs of SW Atlantic estuaries (2011)
    Inter-Research
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © Inter-Research, 2005. This article is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Marine Ecology Progress Series 293 (2005): 155-164, doi:10.3354/meps293155.
    Description: The intertidal burrowing crab Chasmagnathus granulatus is the dominant species in soft bare sediments and vegetated intertidal areas along the SW Atlantic estuaries (southern Brazil, 28°S, to northern Patagonia, 42°S). C. granulatus creates burrows that can reach densities of 60 burrows m–2, and its burrowing activities increase water and organic matter content of sediments. To evaluate the long-term effect of burrows on the origin and transformation of accumulated organic matter within sediments, we compared C and N stable isotope signatures of sediments, plants, and consumers within areas with and without crabs. 15N signatures of sediments and primary producers were enriched by 3 to 7‰ in areas with crabs. The enrichment was present in 4 different Argentine estuarine environments (Mar Chiquita coastal lagoon, 37°46’S, 57°19’W, Bahia Blanca, 38°50’S, 62°07’W, San Blas, 40°33’S, 62°14’W, San Antonio, 40°48’S, 64°52’W). Enrichment owing to crab activity appeared to overwhelm possible different N loads, anthropogenic influence, and other properties. Crab activity thus uncoupled the nitrogen dynamics in sediments from external controls. Enrichment of the heavier isotope of N could be the result of an increase in denitrification rates in areas with burrows. Crabs therefore forced faster transformation of available to unavailable nitrogen, making less inorganic nitrogen available to deeper waters. Food webs in areas with and without crabs were similar in shape, but less mobile benthic organisms (nematodes, fiddler crabs and the polychaete Laeonereis acuta) showed enriched N isotopic signatures. The benthic food web seemed separate from that of suspension feeders or water column consumers. Benthic microalgae were an important source for infauna, and marsh plants were particularly important for burrowing crabs.
    Description: This research was supported by Marine Biological Laboratory (MBL, Woods Hole, Massachusetts) Summer Research Fellowships to F.B. and O.I. This study was partially supported by the Fundacion Antorchas (13956-46 to F.B. and 14116/230 to O.I.). P.M. was supported by a fellowship from CONICET.
    Keywords: Estuaries ; Food webs ; Stable isotopes
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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