Metabolic rate characteristics and sediment cleaning potential of the tropical sea cucumber Holothuria scabra

Abstract

The oxygen consumption rate (OCR) and ammonium excretion rate (AER) of a tropical sea cucumber, <i>Holothuria scabra</i>, were determined in laboratory experiments. OCR and AER exhibited a significant negative correlation to body weight (BW), expressed as a power function of \(\mathrm{BW:}\; \mathit{OCR} = 0.09 \times BW^{-0.58}(\mathrm{mgO_{2}/g/h, r^{2}=0.89, n=15})\) and \(AER = 0.38 \times BW^{-0.19}\) \((\mathrm{\mu\text{molN/g/h}}, \mathrm{r^{2}=0.54}, n=15)\). These values were comparable to those in previous studies on other sea cucumber species. The OCR of shrimp tank sediment was reduced to less than half \((4.5 \pm 0.3 \mathrm{\;to\;} 1.0 \pm 0.1\;\mathrm{mgO_{2}/gdry/h)}\) by the ingestion and excretion process of <i>H. scabra</i>. Acid volatile sulfide (AVS-S) concentration was also decreased to less than half (0.67 to 0.31 mgS/mgdry); despite the low reduction rates of organic carbon and nitrogen contents (0.19 to 0.14 mgC/mgdry and 0.022 to 0.019 mgN/mgdry, respectively). These results suggest that components in the sediment with high oxygen consumption potential were removed by <i>H. scabra</i>. These findings also provide fundamental information with which to evaluate the quantitative role of <i>H. scabra</i> in polyculture with shrimp.