Mollusc-shell debris derived from aquaculture can promote macrofaunal communities with a high bioturbation capacity

Nuria Casado-Coy,Pablo Sánchez-Jerez,Jesus S Troncoso,Carlos Sanz-Lazaro

doi:10.1016/j.aquaculture.2021.737642

Nuria Casado-Coy, Pablo Sánchez-Jerez + Show 2 more

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https://doi.org/10.1016/j.aquaculture.2021.737642

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Abstract

Marine aquaculture releases mollusc shell debris which can accumulate on the seabed. Due to its low degradability, mollusc shell debris becomes integrated into the sediment, modifying both its structure and associated biogeochemical processes. These changes are expected to influence the biological assemblages within the sediment, which play a key role in the biogeochemical processes due to bioturbation. We performed an in-situ experiment to test the effects of mollusc shell-hash on the bioturbation capacity of the macrofaunal assemblages within the sediments affected by marine aquaculture. The aquaculture facilities chosen were a fish farm in an oligotrophic area of the Mediterranean over a sandy sediment, and a mussel farm in the Atlantic located in an estuary over silty sediment. Mollusc shell-hash promoted macrofaunal assemblages with a high bioturbation potential, regardless of the influence of aquaculture. Nevertheless, in the sediment from the mussel-farm, the shell-hash did not have a marked effect on the macrofaunal assemblages. The effect of shell-hash on promoting macrofaunal communities with a high bioturbation potential capacity is therefore dependent on the existing environmental conditions in the area, including the natural organic matter input and grain size of the sediment. Shell-hash could be used a strategy to improve the ecosystem function of sediments as a circular economy-oriented management practice.

Highlights

Aquaculture is a widespread activity in coastal marine areas (FAO, 2020) with associated environmental drawbacks (Edgar et al, 2010; Mckindsey et al, 2011; Riera et al, 2013)
The acid volatile sulphates (AVS-S) accumulation in the experimental units from the fish farm only changed under the influence of aquaculture, where it increased by 151.7 ± 108.1 mg⋅kg− 1 compared to the samples that were not influence by aquacul ture
The NH4+ porewater concentration in the experimental units increased by 522.8 μM under the influence of aquaculture, while shellhash increased it by 47.0 ± 31.5 μM where there was no aquaculture influence and by 229.6 ± 124.0 μM where there was, compared to the samples with no shell-hash

Summary

Introduction

Aquaculture is a widespread activity in coastal marine areas (FAO, 2020) with associated environmental drawbacks (Edgar et al, 2010; Mckindsey et al, 2011; Riera et al, 2013). Studies have focused on the organic waste derived from uneaten pellets, faeces, and pseu dofaeces from the species being farmed (Crawford et al, 2003; Hargrave et al, 2008; Sanz-Lazaro and Marín, 2008), but waste is generated by the biofouling linked to aquaculture facility structures (Fitridge et al, 2012; Sanchez-Jerez et al, 2019a, 2019b). Biofouling grows in the structures of fish farm facilities, and, natu rally or due to its mechanical removal as maintenance activities to prevent damage, such as the excessive increase of weight and limitation of water exchange (Bannister et al, 2019) these debris settle in the sediment.

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