Isotopic evidence and consequences of the role of microbes in macroalgae detritus-based food webs

Abstract

Deep subtidal coastal food webs are increasingly a focus among coastal researchers, largely due to the reliance of these systems on subsidies of organic detritus donated from allochthonous sources. To better understand the dynamics of these food webs, researchers have frequently employed multiple stable isotope (MSI; δ 13 C, δ 15 N, δ 34 S) analysis to gain insights into the relative importance and origins of various sources of detritus. However, the role of microbial decomposition in these detritus-based food webs has been poorly quantified and frequently overlooked in MSI food web mixing models. In this study, we explicitly examined the ecological and MSI methodological effects of microbial decomposition of algal detritus. We found a relationship between δ 15 N enrichment and microbial abundance on decomposing kelp blades, and evidence that this pattern is influenced by the underlying biochemistry of the kelp. C:N ratios supported the hypothesis that microbial biofilms utilize nitrogen from kelp detritus, rather than augment the detrital nitrogen content. The results also showed that microbial effects can introduce a nonnegligible amount of error to MSI mixing models if left unquantified.KEY WORDS: Detritus · δ 15 N · Microbes · Isotopes · Kelp · Food webs · δ 13 C · δ 34 S Resale or republication not permitted without written consent of the publisher Editorial responsibility: Just Cebrian,

Sustained productivity and respiration of degrading kelp detritus in the shallow benthos: Detached or broken, but not dead

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Sandy Beaches as Biogeochemical Hotspots: The Metabolic Role of Macroalgal Wrack on Low-productive Shores

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Degradation dynamics and processes associated with the accumulation of Laminaria hyperborea (Phaeophyceae) kelp fragments: an in situ experimental approach

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