Significant roles of bacteriochlorophylla supplemental to chlorophylla in the ocean.

Bacteriochlorophylla (BChla)-based phototrophy cannot be ignored in understanding of carbon cycle in the ocean. However, the role of BChla relative to chlorophylla (Chla) along environmental gradients remains unclear. On the basis of the investigations in the Pacific, Indian Oceans and the China Seas, we show that the average contribution of BChla relative to Chla is higher in open-ocean compared with shelf environments, the estimated BChla-based phototrophy could reduce respiratory organic carbon consumption of 2.4% and 5.4% of the primary productions in the shelf and oceanic waters, respectively. This suggests that BChla-based phototrophy has an important role supplemental to Chla-based photosynthesis in the ocean's carbon cycle and would be critical for a marine region to be a sink or a source of atmospheric CO(2).