Aquatic hyphomycetes: a potential source of polyunsaturated fatty acids in detritus-based stream food webs
Résumé
To date, aquatic hyphomycetes have mainly been considered as a source of carbohydrates, mineral elements and proteins for detritivores in detritus-based headwater streams. Yet, consumers are highly dependent on other molecules, such as essential fatty acids, to complete their biological cycle. These molecules might be limiting in detritus-based ecosystems since they are primarily synthesized by autotrophic organisms. We investigated: (i) if aquatic hyphomycetes are able to synthesize polyunsaturated fatty acids (PUFAs); and (ii) if the abundance of phosphorus, often considered as a limiting factor in headwater streams, could affect the proportions of PUFAs in aquatic hyphomycetes. All hyphomycete species tested synthesized high amounts of PUFAs (C18 omega 3 and omega 6) and the proportions of these essential fatty acids varied with P availability. This study sheds new light on the importance of aquatic hyphomycetes in the detritus-based stream food web, but also on potential co-variations between mineral nutrient limitation and the availability of essential fatty acids for consumers.