Plant protein-based feeds and commercial feed enable isotopic tracking of aquaculture emissions into marine macrozoobenthic bioindicator species

ABSTRACT

Brittle stars (Ophiura spp.) and other benthic macrofauna were collected in a prospective mariculture area in the North Sea to determine if these taxa could be used as indicator species to track nutrients released from future offshore aquaculture sites. We analysed natural carbon and nitrogen stable isotopic signatures in tissues from macrofauna and compared these to six feed ingredients and four experimental diets made thereof, as well as to a commercial feed with and without lipid and carbonate removal. Our data suggest practicability of using isotopic signatures of Ophiura spp. to track aquaculture-derived organic material if plant-based fish diet ingredients and commercial feed were used for fish farming in the German Exclusive Economic Zone. Diets with high fish meal content would not be detected in Ophiura spp. using isotopic measures due to the similarity with the marine background. Our data provide valuable baseline information for studies on the impact of offshore aquaculture on the marine environment.

KEYWORDS:

• Benthic fauna
• brittle stars Ophiura
• carbon-13
• environmental monitoring
• fish feed
• German EEZ (Exclusive Economic Zone)
• nitrogen-15
• North Sea
• offshore aquaculture
• stable isotopes

Acknowledgements

The authors thank Dr M. Kloppmann (Thünen Institute of Sea Fisheries, Hamburg) for providing samples of benthic macrofauna and Dr F. Meyberg, B. Alpers and G.-M. Velasquez (University of Hamburg) for their help with sample preparation and Dr A. Giesemann and her team at the Stable Isotope Laboratory of the Thünen Institute of Climate-Smart Agriculture (Braunschweig) for conducting the stable isotope measurements. They also thank the anonymous reviewers for comments on an earlier manuscript version.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This project was partly funded by the Federal Ministry of Food and Agriculture (BMEL) based on a decision of the Parliament of the Federal Republic of Germany via the Bundesanstalt für Landwirtschaft und Ernährung (BLE) under the innovation support program, grant 2817301010.