Internal variations in nutrient concentrations and the C and N stable isotope ratios in leaves of the seagrass Enhalus acoroides

We analyzed the content of tissue nutrients (carbon, nitrogen, and phosphorus), the C:N:P ratio, the carbon stable isotope ratio ( δ 13 C ) and the nitrogen stable isotope ratio ( δ 15 N ) of leaves of Enhalus acoroides (L. f.) Royle growing in two submerged beds in southwest Thailand. The N and P concentrations and δ 15 N decreased with increasing distance along the leaf. The maximum ranges in one leaf were 1.80–4.05% for N, 2.85–6.64 mg g−1 for P, and 1.28–2.93‰ for δ 15 N . The C:N, C:P, and N:P ratios increased as the distance along the leaf increased. The maximum ranges in one leaf were 12.5–24.3 for C:N, 162–622 for C:P, and 14.0–28.9 for N:P. In contrast, C concentration and δ 13 C fluctuated with distance along the leaf, and the longest leaves from each beds showed similar patterns of fluctuation. The variation of the chemical signature within leaves suggests that special attention is needed to apply these data to the evaluation of nutrient conditions during growth in food-web analyses involving seagrass beds.