Figure 5 . Relative contributions of different forms of carbon to the released food carbon over the entire 36-h depuration at different food rations (a ) and the allocation of the ingested food carbon of marine medaka (b ). Data are the mean ± SD (n =3–5). The error bars represent the standard deviations. DOC, dissolved organic carbon; CO2, carbon dioxide; PC, particulate carbon. The food rations are expressed as a percentage of the fish dry weight (DW). The values in brackets in subfigure (b) indicate the means of the above-noted ranges.
3.3 Release and turnover of fish body carbon
The body carbon of the fish was replaced and released at relatively high rates. The K e was 0.053 d-1 at the daily food ration of 4.3% fish DW, whereas the rate was significantly increased (0.12 d-1) at the daily food ration of 2.2% fish DW (ANCOVA, p < 0.05) (Figure 6a).
The proportions of DOC, CO2, and PC for both daily food rations did not show clear change trends with depuration time (least-squares regression, p > 0.1) (Figure 6b, c). For the entire 8-d depuration, the proportions of DOC, CO2, and PC did not vary significantly between the two daily food rations (Figure 7a). DOC, CO2, and PC accounted for 39%–42% (40.4% on average), 40%–45% (42.6% on average), and 16%–18% (16.9% on average) of the released body carbon, respectively (Figure 7b).
Figure 6 . Retention of 14C-labeled structural carbon in marine medaka during the 8-d depuration (a ) and the relative contribution of different forms of carbon to the released fish body carbon at daily food rations of 2.2% (b ) and 4.3% (c ) of the fish dry weight (DW). Data are the mean ± SD (n =3–5). The error bars represent the standard deviations. DOC, dissolved organic carbon; CO2, carbon dioxide; PC, particulate carbon. Note the natural logarithm scale in subfigure (a )