Organically selective movement and deposit-feeding in juvenile sea cucumber, Australostichopus mollis determined in situ and in the laboratory

Highly accurate methods were used to investigate varying types of feeding selectivity in juvenile sea cucumber, Australostichopus mollis both in situ and in laboratory experiments. Juvenile A. mollis exhibited significant levels of positive selectivity for organic particles. Nitrogen enrichment in fine grain foregut samples exceeded 100% compared to diet sediments, whilst carbon enrichment was as high as 145%. Foregut organic enrichment was, however, less than that reported for other aspidochirote holothurians. In laboratory behavioural experiments significantly more juveniles inhabited areas where sediment total organic matter (TOM) was higher. However, the ability of juveniles to distinguish between different TOM levels of sediments became limited once TOM in treatments exceeded approximately 3%. Comparative analyses of grain size spectra in foregut and diet sediments, however, showed feeding is non-selective for particle size. The ability of juvenile A. mollis to effectively select organic particles from sediments underlines the importance of deposit-feeding sea cucumbers in nutrient recycling and regulation in coastal sediments.

► Deposit-feeding sea cucumbers exhibit organically selective feeding and movement.
► Organically selective feeding increases organic intake efficiency in sea cucumber.
► Efficient organic uptake drives nutrient recycling/regulation in coastal sediments.
► Selective movement underlines potential for impacted sediment remediation.