as a Major Consumer of Fixed Nitrogen.

Crocosphaera watsonii (hereafter referred to as ) is a key nitrogen (N) fixer in the ocean, but its ability to consume combined-N sources is still unclear. Using microcosm incubations with an ecological model, we show that has high competitive capability both under low and moderately high combined-N concentrations. In field incubations, accounted for the highest consumption of ammonium and nitrate, followed by picoeukaryotes.

Using metatranscriptomics to estimate the diversity and composition of zooplankton communities.

DNA metabarcoding is a rapid, high-resolution tool used for biomonitoring complex zooplankton communities. However, diversity estimates derived with this approach can be biased by the co-detection of sequences from environmental DNA (eDNA), nuclear-encoded mitochondrial (NUMT) pseudogene contamination, and taxon-specific PCR primer affinity differences. To avoid these methodological uncertainties, we tested the use of metatranscriptomics as an alternative approach for characterizing zooplankton communities.

Nanomolar phosphate supply and its recycling drive net community production in the subtropical North Pacific.

Seasonal drawdown of dissolved inorganic carbon (DIC) in the subtropical upper ocean makes a significant contribution to net community production (NCP) globally. Although NCP requires macronutrient supply, surface macronutrients are chronically depleted, and their supply has been unable to balance the NCP demand. Here, we report nanomolar increases in surface nitrate plus nitrite (N+N, ~20 nM) and phosphate (PO, ~15 nM) from summer to winter in the western subtropical North Pacific.

Longitudinal and Vertical Variations of Dissolved Labile Phosphoric Monoesters and Diesters in the Subtropical North Pacific.

The labile fraction of dissolved organic phosphorus (DOP) - predominantly consisting of phosphoric esters - is an important microbial P source in the subtropical oligotrophic ocean. However, unlike phosphate, knowledge for labile DOP is still limited due to the scarcity of broad and intensive observations. In this study, we examined the concentrations and size-fractionated hydrolysis rates of labile phosphoric monoesters and diesters along a >10,000 km longitudinal transect in the North Pacific (23°N; upper 200-m layer).