Isotopic evidence of microbial pathways in macroalgal detritus-based coastal food webs

Abstract

Deep subtidal coastal food webs are increasingly a focus of interest 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) analysis to gain insights on the relative importance and origins of various detritus sources. 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, I explicitly examine the ecological and MSI methodological effects of microbial decomposition of algal detritus. This study provides evidence that microbial decomposition of detritus may have cascading trophic effects. The results also suggest that microbial biofilms may act as a distinct trophic level, which can introduce a significant amount of error to MSI mixing models if not accounted for.