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Potential overestimation of community respiration in the western Pacific boundary ocean: What causes the putative net heterotrophy in oligotrophic systems?
Author(s) -
Huang Yibin,
Chen Bingzhang,
Huang Bangqin,
Zhou Hui,
Yuan Yongquan
Publication year - 2019
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 - 10.1002/lno.11179
Subject(s) - biogeochemical cycle , photic zone , trophic level , primary production , biome , heterotroph , environmental science , biological pump , carbon cycle , incubation , plankton , atmospheric sciences , oceanography , environmental chemistry , biology , ecosystem , nutrient , ecology , phytoplankton , chemistry , geology , biochemistry , genetics , bacteria
Microbial metabolism is of great importance in affecting the efficiency of biological pump and global carbon cycles. However, the metabolic state of the oligotrophic ocean, the largest biome on Earth, remains contentious. We examined the planktonic and bacterial metabolism using in vitro incubations along the western Pacific boundary during September and October 2016. The integrated gross primary production (GPP) of the photic zone exhibited higher values in the region of 2°–8°N along 130°E and the western Luzon Strait, which is consistent with the regional variability of nutrients in the different ocean provinces. Spatially, the community respiration (CR) was less variable than the GPP and slightly exceeded the GPP at most of the sampling stations. Overall, the in vitro incubation results suggest a prevailing heterotrophic state in this region. A comparison of the metabolic rates from the in vitro incubations with recently published biogeochemical model results in the same region shows that our observed GPP values were close to those predicted by the model, but the measured CR was approximately 30% higher than the modeled values. We also found that most of the in vitro CR estimates were higher than the upper range of the empirical CR estimated from the sum of the contributions of the main trophic groups. Conversely, the estimates of the empirical CR support the rationality of the CR predicted by the biogeochemical model. In general, the results indicate that systematic net heterotrophy is more likely a result of the overestimation of CR measured by the light–dark bottle incubation experiments, although the exact cause of the methodological problem remains unknown.