Abstract: Skeletonema costatum is a common dominant diatom species in the coastal environments. The capacity of S. costatum to utilize nitrate (NO₃^-), urea, and five amino acids was studied, and the growth of S. costatum under different proportions of NO₃^- and urea was examined. Furthermore, the maximum specific growth rate (μ_max) and halfsaturation constant (K_s) of S. costatum were determined using NO₃^- as the sole nitrogen (N) source. The purpose of this study is to understand the impact of nitrogen enrichment on the growth of diatoms and primary productivity of marine environments. The tesults showed that S. costatum was able to utilize both dissolved inorganic nitrogen (NO₃^-) and dissolved organic nitrogen (urea, almandine, glycine, threonine, serine and aspartic acid). The best growth was recorded in culture with NO₃^-, followed in culture with urea. Alanine was one of the most easily utilized amino forms, followed by threonine, serine and aspartic acid. However, the growth was relatively lower when using glycine as sole N source compared with the other amino acids. Algal cells grew better in culture with both NO₃^- and urea as nitrogen sources compared with that with NO₃^- or urea as sole N nutrient. Maximum cell density was found in the culture with 75% urea and 25% NO₃^-. The specific growth rate and environmental capacity increased with the increasing NO₃^- concentration (0-1000 μmol·L^-1), and the μ_max and K_s of S. costatum were 0.426 d^-1 and 25.0 μmol·L^-1, respectively. The results suggested that S. costatum could use various organic N, and grew well under high N levels. Therefore, the sufficient organic N and high N concentration in the coastal waters might play important roles in the occurrence of algal blooms.

Key words: PI-MVM, ecological poverty, poverty type, multidimensional poverty measurement, spatial distribution., poverty degree