The Eastern Mediterranean Sea (EMS), is ultra-oligotrophic with unusual anti-estuarine circulation. It is P depleted and the limited enrichment studies which have been carried out, suggest seasonal changes in nutrient limitation. In this study high sensitivity dissolved nutrients (and associated parameters) were determined monthly over an annual cycle at a pelagic location in the SE Levantine basin. Nitrate & Nitrite (N_ox) concentrations were high (300–500 nM) during the winter mixing period and enabled a concurrent phytoplankton increase in which larger picoeukaryotes and eukaryotes were dominant. After the thermal stratification of the water column commenced, N_ox decreased through early summer transition period to low values (generally 50 nM or less) in the late summer. DIP remained at low nM concentrations the entire year while DOP decreased from 40 nM in winter to 30 nM in summer.. Prochlorococcus, the smallest picocyanobacteria, that does not typically utilize nitrate, dominated during the summer when both N_ox and DIP concentrations were lowest. Ammonium concentrations were low (10–100 nM) with no systematic changes with season or depth. As a result, the DIN:DIP ratios were high (20–825) in winter and low (2–66) in summer, showing that these ratios vary seasonally. The dynamics of nutrient availability combined with the temporal changes in total chlorophyll and the altered dominance of the predominant phytoplankton species (i.e. nitrate-metabolizing Synechococcus during winter versus the smaller Prochlorococcus abundant in summer), leads to our hypothesis that the seasonal change in DIN:DIP indicates a switch from P limitation in winter during the annual phytoplankton increase to N&P or even N limitation in summer. Export Production (172 mmol N m⁻² y⁻¹) determined from the calculated loss of N_ox from the photic zone, was similar to previous estimates in the EMS. Our results in terms of seasonally changing nutrient dynamics and resulting productivity confirm that the EMS has many of the characteristics found in P starved ocean gyre systems.

东地中海 (EMS) 是超贫营养的，具有不寻常的反河口环流。磷已耗尽且已进行的有限富集研究表明营养限制的季节性变化。在这项研究中，在东南黎凡特盆地的一个远洋位置，在一年周期内每月测定高灵敏度溶解养分（和相关参数）。在冬季混合期间，硝酸盐和亚硝酸盐 (N _ox ) 浓度很高 (300-500 nM)，并且使浮游植物同时增加，其中较大的微核生物和真核生物占主导地位。水柱热分层开始后，N _ox在夏末，通过初夏过渡期降低到低值（通常为 50 nM 或更少）。DIP保持在低浓度纳米整整一年，而DOP为40nm夏季..下降，冬季到30nm原绿球藻，最小picocyanobacteria，不通常使用硝酸盐，夏天当两个n中占主导地位_牛和 DIP 浓度最低。铵浓度低 (10-100 nM)，没有随季节或深度的系统变化。因此，冬季的 DIN:DIP 比率较高 (20–825)，夏季较低 (2–66)，表明这些比率随季节而变化。营养物质可用性的动态结合总叶绿素的时间变化和主要浮游植物物种（即冬季代谢硝酸盐的聚球藻与夏季丰富的较小的原绿球藻）的优势地位的改变，导致我们假设 DIN 的季节性变化： DIP 表明从每年浮游植物增加期间冬季的 P 限制转换到夏季的 N&P 甚至 N 限制。出口产量（172 mmol N m ^-2 y^-1 ) 从光区的 N _ox计算损失确定，与之前在 EMS 中的估计值相似。我们在季节性变化的养分动态和由此产生的生产力方面的结果证实，EMS 具有许多在缺磷的海洋环流系统中发现的特征。