Evisceration of Holothuria poli by mechanical, chemical and hypoxia stress methods and its bioremediation potentials for the pisciculture wastewater

Abstract

In this work, we investigated the potential benefits of Holothuria (Roweothuria) poli Delle chiaje, 1824, in the bioremediation of aquaculture farm effluents in the Mediterranean Sea as well as the impact of mechanical, chemical and hypoxic stress conditions on the process of evisceration. The usefulness of H. poli as an effective candidate for fish farm effluent bioremediation was tested by placing 14 sea cucumbers in aquaria with 50 L of aquaculture wastewater for 21 days and examining the physicochemical parameters of this wastewater at fixed times (0, 7, 14 and 21 days). Interestingly, the results clearly showed that the addition of H. poli reduces chemical oxygen demand (COD), total organic carbon (TOC) and suspended matter (SM). In the second part of this work, we examined the exposure of H. poli to mechanical, chemical and hypoxic stimuli under controlled laboratory conditions. The results showed that the evisceration was strongly induced by potassium chloride (KCl) and sodium hydroxide (NaOH), compared with magnesium chloride (MgCl2), sodium chloride (NaCl), sodium sulphate (Na2SO4) and sodium bicarbonate (NaHCO3). In addition, high mechanical pressure and hypoxia (exposure to ambient air) also resulted in the evisceration of H. poli. In conclusion, the sea cucumber H. poli is an effective candidate for the fish farm effluent bioremediation in the Mediterranean and is useful for sustainable integrative multitrophic aquaculture.