We detected significant variation in the compositions of the PA pools between the spring and fall cruises. This is likely due to differences between seasons in the composition of the plankton Danusertib (phytoplankton, zooplankton and bacteria) that produce (Nishibori et al., 2003 and Hamana and Matsuzaki, 1992; Hamana et al., 2004) and degrade (Sowell et al., 2009 and Mou et al., 2011) polyamines. Differences in the composition of the plankton community may also explain the dominance of spermidine and/or spermine over putrescine in the PA pool. Putrescine has been identified as the predominant PA in other marine environments (Badini et al., 1994 and Nishibori et al., 2003).
5. Conclusion
We optimized an HPLC method to allow reliable and simultaneous measurements of 20 DFAAs and 5 PAs in seawater. Our measurements of seawater at the Gray's Reef National Marine Sanctuary demonstrated spindle apparatus concentrations of individual PA and DFAA compounds were often comparable. Both PAs and DFAAs generally represented a small fraction of the labile DON pool; however, occasionally total PAs may reach concentrations approaching total DFAAs. Our data suggest that PAs are occasionally an important component of labile marine DON. Correlations between PA concentrations and bacterial abundance suggest that PAs are tightly coupled to the dynamics of bacterial communities in the ocean.
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