Effects of different feeding rations on the CO2 fluxes at water-air interface and energy budget of sea cucumber Apostichopus japonicus (Selenka)

Feeding ration is one of the most important factors that directly affect growth and physiology progress of sea cucumber Apostichopus japonicus. In present study, a 32-day experiment was carried out to investigate the effects of feeding ration (1%, 3%, and 7% of total body weight, named F1, F3 and F7, respectively) on growth performance, carbon allocation, energy budget and CO2 fluxes at water-air interface. Results showed the maximum specific growth rate was observed at F3, while F7 showed negative growth. And F3 exhibited the highest enzyme activities associated with respiration in respiratory tree and body wall. Carbon intake, nitrogen intake and energy intake were significantly affected by feeding ration, while energy allocation between F1 and F3 on growth and excretion were no significant difference, suggesting that increased feeding ration slightly increased the digestive burden. Compared to F1, food conversion efficiency and fecal energy of F3 were reduced, while respiration metabolizable energy was increased. Mean CO2 flux at water-air interface of F3 was significantly higher than that of F1 at noon and dusk, and mean CO2 flux of F7 was significantly lowest than other groups at all sample times. Our results revealed that feeding rations influence CO2 fluxes at water-air interface by altering physiological status, carbon content, and energy allocation for respiration metabolizable of sea cucumber. Our study provides a theoretical basis for promoting the development of efficient low-carbon aquaculture technology for sea cucumber and sustainable development of the industry