Figure 8 . Carbon flow in and release from mesopelagic fish in the global open ocean. The solid and dotted lines show the carbon flows from the ingested food and the structural body carbon (fish body), respectively. a , diel vertically-migrating mesopelagic fish, and b , nonmigrating mesopelagic fish. DOC, dissolved organic carbon; CO2, carbon dioxide; PC, particulate carbon.
Our results showed that the vertical migration of mesopelagic fish contributes greatly to the active export of carbon. Assuming that half of the daily food carbon release by the DVM mesopelagic fish occurs in deep waters, the global active exports of DOC, CO2, and PC mediated by the DVM mesopelagic fish are 0.28–4.59, 0.19–3.13, and 0.07–1.14 Pg C/y, respectively (Text S5; Table S1).
The results also showed that FC release was approximately 3.7 times as much as BC release(Table 1). For all the DVM and NM mesopelagic fishes at both low and high latitudes, the DOC released from food was more than 4 times higher than that released from the fish body, and the CO2 and PC released from food were more than 2 times higher than those released from the fish body (Table 1).
Table 1.Carbon release model scenarios for mesopelagic fish in the global open ocean. The mesopelagic fishes were divided into diel vertically migrating (DVM) and nonmigrating (NM) groups, and the global open ocean was divided into two regions: open oceans in 40°N–40°S, and other regions in high latitudes up to 70°N/S.