Evaluating sea cucumbers as extractive species for benthic bioremediation in mussel farms

Filter-feeding mussels blend suspended particles into faeces and pseudo-faeces enhancing organic matter flows between the water column and the bottom, and strengthening benthic-pelagic coupling. Inside operating farms, high bivalve densities in relatively confined areas result in an elevated rate of organic sinking to the seabed, which may cause a localized impact in the immediate surrounding. Deposit-feeding sea cucumbers are potentially optimal candidates to bioremediate mussel organic waste, due to their ability to process organic-enriched sediments impacted by aquaculture waste. However, although the feasibility of this polyculture has been investigated for a few Indo-Pacific species, little is known about Atlanto-Mediterranean species. Hence, for the first time, in the present study, we conducted a comparative investigation on the suitability of different Mediterranean sea cucumber species, to be reared in Integrated Multitrophic Aquaculture (IMTA) with mussels. A pilot-scale experiment was accomplished operating within a mussel farm where two sea cucumbers species, Holothuria tubulosa and Holothuria polii, were caged beneath the long-line mussel farm of Mytilus galloprovincialis. After four months, H. tubulosa showed high survivorship (94%) and positive somatic growth (6.07%); conversely H. polii showed negative growth (− 25.37%), although 92% of specimens survived. Furthermore, sea cucumber growth was size-dependent. In fact, smaller individuals, independently from the species, grew significantly faster than larger ones. These results evidenced a clear difference in the suitability of the two sea cucumber species for IMTA with M. galloprovincialis, probably due to their different trophic ecology (feeding specialization on different microhabitats, i.e. different sediment layers). Specifically, H. tubulosa seems to be an optimal candidate as extractive species both for polycultures production and waste bioremediation in M. galloprovincialis operating farms.

Description

This investigation was supported from “Regione Puglia” in the frame of PO FEAMP project (CUP: B18I17000950009) and from funding within the PO FEAMP measure 2.47 project (CUP: J89J19000920005). The authors wish to thank Ittimar Soc. Coop. for allowing access to their mussel farm and their technical support in the field work, and the staff of A.Ge.I. Agricoltura Gestione Ittica S.c.r.l. for their organizational and operational assistance. This work was also supported by FCT—Fundação para a Ciência e a Tecnologia, I.P., within the scope of the project MARE (UIDB/04292/2020) and the Associate Laboratory ARNET (LA/P/0069/2020), A.P. was supported with the Scientific Employment Stimulus—Institutional Call—CEECINST/00051/2018.

URI

http://hdl.handle.net/10400.8/8791

Citation

Grosso, L., Rampacci, M., Pensa, D. et al. Evaluating sea cucumbers as extractive species for benthic bioremediation in mussel farms. Sci Rep 13, 1457 (2023). https://doi.org/10.1038/s41598-023-28733-7