Dynamics of δ15N isotopic signatures of different intertidal macroalgal species: Assessment of bioindicators of N sources in coastal areas. Issue 1 (15th September 2016) - Lemesle, Stéphanie
Abstract: δ 15 N of annual ( Ulva sp., Porphyra sp.) and perennial intertidal seaweed species ( Chondrus crispus, Fucus sp.) collected on 17 sampling points along the French coast of the English Channel in 2012 and 2013 were assessed on their suitability as bioindicators of N pollution in coastal areas. A sine function applied for δ 15 N time series data showed for all the species the same seasonal trend with lowest δ 15 N values in April and highest in summer but with no significant interspecific differences of amplitude (α) and phase angle (ϕ). This model provides a useful tool for monitoring the inter-annual changes of N pollution. An interspecific variability of δ 15 N values was observed, probably due to their tolerance to emersion. An in vitro study for comparing the kinetic acquisition of the isotopic signal and N uptake mechanisms of each species underlined the influence of algal physiology on the δ 15 N interspecific variability. Highlights: Seaweed species studied showed the same seasonal trend of δ 15 N in 2012 and 2013. A sine model of δ 15 N seasonality is proposed as a tool for biomonitoring N pollution. δ 15 N of intertidal species is largely influenced by external parameters. δ 15 N integration scale is distinct for annual and perennial algae but complementary.