AEI prepress abstract  -  DOI: https://doi.org/10.3354/aei00319

Analysis of algal growth- and morphogenesis-promoting bacterial factors (AGPFs) in an integrated multi-trophic aquaculture system for farming the green seaweed Ulva

Fatemeh Ghaderiardakani, Gianmaria Califano, Jan Frieder Mohr, Maria Helena Abreu, Juliet C. Coates, Thomas Wichard*

*Email: thomas.wichard@uni-jena.de

ABSTRACT: The marine green macroalgal species Ulva (Chlorophyta) require the presence of a combination of regulatory morphogenetic compounds released by their associated epiphytic bacteria in addition to nutritional parameters. The activity of algal growth- and morphogenesis-promoting factors (AGPFs) derived from bacteria were estimated in a land-based integrated multitrophic aquaculture (IMTA) system of fish and macroalgae (located at the coastal lagoon Ria de Aveiro, Portugal), using a standardised bioassay with axenic cultures of Ulva during a snapshot study. The study thus informs aspects of the various potential aquaculture–environment interactions. It was observed that both the water from the lagoon (external to the farm system) and the water from the fish pond (input for algae cultures) could completely restore the normal growth and morphology of the macroalga under axenic conditions. The results highlight the presence of a sufficient chemical cocktail of AGPFs in this IMTA system required for growth and morphogenesis of Ulva. In addition, the water from fish farming increases the nutrient availability (nitrate and ammonium) needed for macroalgae production at low concentrations of metal contaminants. Interestingly, the abundance of known morphogenesis-inducing bacteria (e.g., Maribacter, Sulfitobacter) were enriched in the Ulva aquaculture water of compared to the water from the lagoon. We thus conclude that sustainable growth and development of Ulva can benefit from multitrophic aquaculture systems and shallow-water systems, due to the naturally enriched AGPFs and their in situ production by bacteria in intensive algal aquacultures.