Nitrogen biofiltration capacities and photosynthetic activity of Pyropia yezoensis Ueda (Bangiales, Rhodophyta): groundwork to validate its potential in integrated multi-trophic aquaculture (IMTA)
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Porphyra spp. (currently Porphyra and Pyropia) are major sources of seafood globally. In this study, we investigated the effects of ammonium concentration, water temperature, and thallus stocking density on N-ammonium uptake rate (NUR), tissue nutrients content, N–NH4 + filtration efficiency (NUE: nitrogen uptake efficiency %) of Pyropia yezoensis at a laboratory scale and in a mesoscale to evaluate the potential of this species as a biofilter. Additionally, photosynthetic activity was examined using Diving-PAM fluorometer to evaluate the health status. At a laboratory scale, the NUR and tissue nitrogen (N) content of P. yezoensis increased with increasing NH4 + concentrations in the medium. The NUR at thallus stocking densities of 5 and 10 g fresh weight (FW) L–1 were significantly higher than that at 20 g FW L–1. Effective quantum yield (∆ F/F’ m ) and tissue N content was significantly higher at all stocking densities than that at the beginning of experiment. The NUE was over 90 % at 10 and 17 °C, while all thalli cultured at 25 °C died after 5 days. In a mesoscale, the NUE at a thallus stocking density of 10.0 g FW L–1 was significantly higher than that at a stocking density of 5.0 g FW L–1. No differences in the NUE occurred between 10 °C and 17 °C. Photosynthetic activity (∆F/F’m and rETRmax) of P. yezoensis at optimal culture condition (10–12 °C and 10 g FW L–1) increased over time through the experiment. This indicates that thallus was healthy during culture and chlorophyll a fluorescence can be as a monitoring tool for evaluating the physiological status of seaweeds in an integrated multi-trophic aquaculture.
KeywordsNitrogen biofiltration IMTA Pyropia yezoensis Photosynthetic activity Stocking density Temperature
We would like to thank Dr. M S Hwang for her kind help. This work was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (2012R1A1A1012429), and the Jeju Sea Grant College Program funded by the Ministry of Oceans and Fisheries of Korea.
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