Seasonal variation of nitrogen and phosphorus pools in the Suruga Bay

Elemental stoichiometry of inorganic and organic matter, especially for nitrogen (N) and phosphorus (P), is an important parameter for understanding of biogeochemical cycles within marine environments. We determined the pools of N and P for dissolved and particulate organic matter (DOM and POM, respectively) and inorganic matter in the Suruga Bay. Seawater samples were taken from 0 m to 1500 m in February. April, July, October, and December, 2001. Nitrate plus nitrite (NO_3 + NO_2), phosphate (PO_4), dissolved and particulate organic nitrogen (DON and PON, respectively) and those of phosphorus (DOP and POP) were measured, and then N : P ratios were calculated for each pool. N : P ratios showed seasonal variation and notable differences among the pools : N : P ratio was 0 - 15 for the inorganic pool [(NO_3 + NO_2) : PO_4], 20 - 30 for DOM (DON : DOP) and 10 - 16 for POM (PON : POP) . As a result, N : P ratio for inorganic and POM pools were lower than Redfield ratio (= 16 : 1), while that for DOM pool was higher. In other words, N was more deficient than P for inorganic and POM pools. In contrast to this result, P was more deficient than N for DOM. Based on these results, we propose that PON is preferentially remineralized over POP, while DOP is preferentially remineralized over DON in the Suruga Bay.publishe