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Large‐scale variability in surface bacterial carbon demand and growth efficiency in the subtropical northeast Atlantic Ocean
Author(s) -
Alonso-Sáez Laura,
Gasol Josep M.,
Arístegui Javier,
Vilas Juan C.,
Vaqué Dolors,
Duarte Carlos M.,
Agustí Susana
Publication year - 2007
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.2007.52.2.0533
Subject(s) - upwelling , environmental science , heterotroph , oceanography , nutrient , trophic level , subtropics , environmental chemistry , bacterial growth , seawater , biology , ecology , chemistry , bacteria , geology , genetics
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.