Large‐scale variability in surface bacterial carbon demand and growth efficiency in the subtropical northeast Atlantic Ocean

• Published in: Limnology and Oceanography
• Main Authors: Alonso-Sáez, Laura, Gasol, Josep M., Arístegui, Javier, Vilas, Juan C., Vaqué, Dolors, Duarte, Carlos M., Agustí, Susana
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2007
• Subjects: North Atlantic; Northeast Atlantic
• Online Access: http://dx.doi.org/10.4319/lo.2007.52.2.0533; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.4319%2Flo.2007.52.2.0533; https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.2007.52.2.0533

We present surface estimates of bacterial respiration, bacterial heterotrophic production (BHP), and bacterial growth efficiency (BGE), and their relationship with nutrient availability, along a trophic gradient from coastal upwelling waters to the open‐ocean waters of the eastern North Atlantic. Bacterial respiration generally ranged between 10 and 30 µg C L −1 d −1 and was relatively unaffected by nutrient enrichment. In contrast, BHP showed higher variability (more than one order‐of‐magnitude range) and was affected by carbon and/or phosphorus additions in different regions. Empirical bacterial carbon‐to‐leucine (Leu) conversion factors (CFs) (range, 0.02–1.29 kg C mol Leu −1 ) decreased from the coast to the open ocean, largely influencing the BHP estimates in oligotrophic waters. We found high percentages of Leu respiration in oceanic waters (average 68% of Leu taken up by bacteria), possibly related to the low CFs found offshore. Empirical CFs were highly correlated to BGE (Pearson correlation coefficient r = 0.86, n = 12, p < 0.0004, log‐log transformed), which varied between 1% in offshore waters and 56% in the upwelling waters. Empirical CFs could be critical not only for accurately constraining BHP, but probably also for predicting BGE in oceanic waters.