Master of Science (MS)
First Advisor's Name
James W. Fourquerean
First Advisor's Committee Title
Second Advisor's Name
Third Advisor's Name
Date of Defense
This experiment investigated causes of seasonality of δ15N and δ13C values in Thalassia testudinum leaf tissue by manipulating plant demand and nutrient supply in situ for 13 months. I clearly demonstrated that seagrass elemental content, stable C and N isotopic content, morphology and the concentration of NH4+ seagrass porewaters directly respond to manipulations of resources and also by the plant demand for nutrients to support growth. Isotopic values displayed marked seasonality with heavier values found in summer (δ15N=5.0% δ13C=-5.7%o) and lighter values in winter (δ15N=1.7%o δ13C= -9.4%o). Calculations of Δ (δ15N source DIN- δ15N plant product) indicate that T. testudinum is able to strongly fractionate against source pool DIN. Interpretation of an enriched N signature as pollution-derived must first recognize the isotopic seasonality of the plant demand relative to the nutrient supply. Only when these links have been explained can the full relevance of δ15N values be applied.
Bernard, Rebecca Jane, "Effects of light and nutrient supply on stable isotope composition and fractionation in nitrogen-limited seagrass beds" (2010). FIU Electronic Theses and Dissertations. 1599.
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