摘要 : <abstract type="main"> <title type="main">Abstract</title> <p> Dinitrogen (N ₂ ) fixation rates were investigated in the euphotic layer of the Bismarck and Solomon Seas using ... 展开 <abstract type="main"> <title type="main">Abstract</title> <p> Dinitrogen (N ₂ ) fixation rates were investigated in the euphotic layer of the Bismarck and Solomon Seas using ¹⁵ N ₂ incubation assays taking into account both the particulate and the dissolved pools. Average depth‐integrated particulate N ₂ fixation rates were 203 (range 43–399) and 1396 (range 176–3132)?μmol N m ^?2 d ^?1 in the Bismarck and Solomon Seas, respectively. In both seas, N ₂ fixation measured in the dissolved pool was similar to particulate N ₂ fixation, highlighting the potentially substantial underestimation of N ₂ fixation in oceanic budgets when only particulate N ₂ fixation is considered. Among the diazotroph phylotypes targeted using quantitative polymerase chain reaction amplification of <fi>nifH</fi> genes, <fi>Trichodesmium</fi> was the most abundant. Regression analyses suggest that it accounted for the major proportion of N ₂ fixation. However, unicellular cyanobacterial and non‐cyanobacterial diazotrophs were also occasionally abundant. This study reports high pelagic N ₂ fixation rates and confirms that the Western Tropical South Pacific is a hot spot for marine N ₂ fixation. </p> </abstract> 收起