Estimation of carbon released by mesopelagic fish in the global open
ocean using a carbon release model and model fish-derived parameters
Linbin Zhou
CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China, CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Provincial Key Laboratory of Applied Marine Biology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China
Corresponding Author:[email protected]
Author ProfileAbstract
The role of zooplanktivorous mesopelagic fish in the ocean carbon cycle
is attracting increasing attention. However, little information is
available regarding the carbon budget of marine zooplanktivorous fish,
let alone that of mesopelagic fish. Here, we propose a carbon release
model that divides fish-released carbon into two parts (i.e., food
carbon release and body carbon release, based on the source (ingested
food and the fish body, respectively)) and three forms (dissolved
organic carbon (DOC), CO2, and particulate carbon (PC)). By feeding a
model marine zooplanktivorous fish, marine medaka (Oryzias melastigma),
a radiocarbon-labeled living rotifer, Brachionus plicatilis, we
quantified a detailed carbon budget for the fish that includes the
allocation of released food and body carbon to DOC, CO2, and PC. The
results indicate that 53%–75% of the ingested food carbon was not
assimilated but was released mainly as DOC (48%–59%), followed by CO2
(30%–40%) and PC (11%–13%). The release (/efflux) rates of fish
body carbon changed from 0.12 to 0.053 d-1 when daily food rations
shifted from 2.2% to 4.3% of the fish biomass. DOC, CO2, and PC
accounted for 39%–42%, 40%–45%, and 16%–18% of the carbon
released from the fish body, respectively. By using the carbon release
model and the parameters derived from the model fish and from the
literature, we estimate that mesopelagic fish in the global open ocean
produce 1.34–15.2, 0.95–10.8, and 0.35–3.97 Pg C/y of DOC, CO2, and
PC, respectively. Our results show that marine zooplanktivorous fish can
transform substantial fractions of their daily ingested food and
released body carbon into DOC and that mesopelagic fish may be important
sources of DOC and fast-sinking PC in the ocean.