Hattenrath Theresa K.

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Theresa K.

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  • Article
    Nitrogen stable isotopes in the shell of Mercenaria mercenaria trace wastewater inputs from watersheds to estuarine ecosystems
    (Inter-Research, 2008-11-25) Carmichael, Ruth H. ; Hattenrath, Theresa K. ; Valiela, Ivan ; Michener, Robert H.
    We tested the usefulness of δ15N values in the organic matrix of whole shells from Mercenaria mercenaria as tracers of anthropogenic nitrogen inputs to coastal ecosystems. Low and high stringency acidification methods were used to define parameters for reliable δ15N determination in shell material for comparison with δ15N values in soft tissues. δ15N values in shell from transplanted and native clams reflected %-wastewater contribution to estuaries, but were 2.3 to 2.5% lighter than δ15N values in soft tissues. Accuracy of δ15N values in shell material depended on recovering a sufficient quantity of organic N from shell (~70 µg) and was not altered by acidification method. Reliable δ15N values were obtained with as little as 80 mg of shell and using 100 µl of acid, but higher stringency methods (treating more shell with more acid for longer duration) typically yielded more N for subsequent stable isotope analysis. Conversely, higher concentrations of acid reduced N recovery. These results suggest that the content of N recovered was of greater concern to obtaining reliable δ15N values from shell material than acidification effects. Differences between δ15N values in shell material and soft tissues likely reflected differences in N assimilation among tissues. In combination with other analyses, this method may be applied to refine modern and historical trophic assessments and discern natural from anthropogenic influences on coastal ecosystems
  • Preprint
    The influence of anthropogenic nitrogen loading and meteorological conditions on the dynamics and toxicity of Alexandrium fundyense blooms in a New York (USA) estuary
    ( 2010-02-17) Hattenrath, Theresa K. ; Anderson, Donald M. ; Gobler, Christopher J.
    The goal of this two-year study was to explore the role of nutrients and climatic conditions in promoting reoccurring Alexandrium fundyense blooms in the Northport-Huntington Bay complex, NY, USA. A bloom in 2007 was short and small (3 weeks, 103 cells L-1 maximal density) compared to 2008 when the A. fundyense bloom, which persisted for six weeks, achieved cell densities >106 cells L-1 and water column saxitoxin concentrations >2.4 x 104 pmol STX eq. L-1. During the 2008 bloom, both deployed mussels (used as indicator species) and wild soft shell clams became highly toxic (1,400 and 600μg STX eq./100g shellfish tissue, respectively) resulting in the closure of shellfish beds. The densities of benthic A. fundyense cysts at the onset of this bloom were four orders of magnitude lower than levels needed to account for observed cell densities, indicating in situ growth of vegetative cells was responsible for elevated bloom densities. Experimental enrichment of bloom water with nitrogenous compounds, particularly ammonium, significantly increased A. fundyense densities and particulate saxitoxin concentrations relative to unamended control treatments. The δ15N signatures (12 to 23‰) of particulate organic matter (POM) during blooms were similar to those of sewage (10 to 30‰) and both toxin and A. fundyense densities were significantly correlated with POM δ15N (p < 0.001). These findings suggest A. fundyense growth was supported by a source of wastewater such as the sewage treatment plant which discharges into Northport Harbor. Warmer than average atmospheric temperatures in the late winter and spring of 2008 and a cooler May contributed to an extended period of water column temperatures optimal for A. fundyense growth (12 – 20ºC), and thus may have also contributed toward the larger and longer bloom in 2008. Together this evidence suggests sewage-derived N loading and above average spring temperatures can promote intense and toxic A. fundyense blooms in estuaries.