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Aquaculture Environment Interactions

    AEI prepress abstract   -  DOI: https://doi.org/10.3354/aei00403

    Reduced physiological performances in a free-living coralline alga induced by salmon faeces deposition

    Erwann Legrand, Tina Kutti, Erika V. Gonzalez Casal, Samuel P. S. Rastrick, Sissel Andersen, Vivian Husa

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    ABSTRACT: Maerl beds are composed through the accumulation of free-living coralline algae and have considerable ecological significance due to the high diversity of associated fauna and flora. The rapid expansion of the Atlantic salmon Salmo salar aquaculture industry in Norway may have major impacts on surrounding maerl beds through the release of considerable amounts of effluents, including fish faeces. This study is the first to test the effects of salmon faeces and inorganic sediment deposition on the photosynthesis, respiration, calcification and pigment content of the coralline alga Lithothamnion soriferum, in a 6 wk laboratory experiment. Inorganic sediment and salmon faeces deposition significantly reduced the amount of light reaching the surface of coralline algae. No impact of inorganic sediment deposition was detected on L. soriferum physiology, while salmon faeces deposition increased respiration rate and reduced net primary production and calcification. Bacterial degradation of the salmon faeces is likely to release toxic compounds which have a drastic impact on L. soriferum physiology. Burial by inorganic sediment and salmon faeces deposition also reduce flow velocity in the vicinity of thalli, limiting nutrient and gas exchanges. This effect may be more adverse with salmon faeces deposition due to the flocculation of sticky faeces particles. Carbon dioxide accumulation in the vicinity of L. soriferum may lead to a decline in pH and alter the calcification process in cell walls. In natural maerl beds, the negative effect of faeces deposition may be exacerbed by longer-term exposure and the presence of other chemicals released by fish farms.