δ15N variation in Ulva lactuca as a proxy for anthropogenic nitrogen inputs in coastal areas of Gulf of Gaeta (Mediterranean Sea)

Abstract

We tested the capacity of Ulva lactuca to mark N sources across large marine areas by measuring variation in its δ(15)N at several sites in the Gulf of Gaeta. Comparisons were made with the macroalga Cystoseira amentacea. Variation of δ(15)N values was assessed also in the coastal waters off the Circeo Natural Park, where U. lactuca and C. amentacea were harvested, as these waters are barely influenced by human activities and were used as reference site. A small fragment from each frond was preserved before deployment in order to characterize the initial isotopic values. After 48 h of submersion, U. lactuca was more responsive than C. amentacea to environmental variation and δ(15)N enrichment in the Gulf of Gaeta was observed. The spatial distribution of δ(15)N enrichment indicated that different macro-areas in the Gulf were affected by N inputs from different origins. Comparison of the δ(15)N values of fragments taken from the same transplanted frond avoided bias arising from natural isotopic variability.

Epilithon δ15N signatures indicate the origins of nitrogen loading and its seasonal dynamics in a volcanic Lake

“…Inputs of nitrogen and phosphorous were also found in this part of the lake by Catalani et al (2006). As in studies of benthic macroalgal δ 15 N (Orlandi et al, 2014) and river epilithic δ 15 N (Schiller et al, 2009), our study also had fine temporal resolution. Indeed, in sites with high organic impact, δ 15 N increased by 2.6‰ between early summer 1 and 2, in association with a 40% increase in tourism pressure (as measured by earnings from parking meters), suggesting that even short-term, pulsed inputs of anthropogenic N can be detected by means of isotopic analysis of epilithon.…”

“…There is a strong need therefore for an accurate, practical and fast environmental monitoring tool. In marine, coastal, transitional water and lotic ecosystems, macroalgal and epilithic δ 15 N signatures have proved to be successful in determining the types and space-time variability of nitrogen loads (Bentivoglio et al, 2016;Cejudo et al, 2014;Cole et al, 2004;Dailer et al, 2010;Gartner et al, 2002;Jona-Lasinio et al, 2015;Orlandi et al, 2014, Pastor et al, 2013Peipoch et al, 2012;Schiller et al, 2009;Titlyanov et al, 2011;Vizzini et al, 2005), while in lacustrine ecosystems there is a lack of knowledge concerning epilithic δ 15 N signatures.…”

“…In addition, the nitrogen isotopic signature, δ 15 N, has been successfully used to monitor coastal marine habitats by determining the type of nitrogen input (Orlandi et al, 2014). Inorganic fertilisers have a δ 15 N range of −4‰ to +4‰, while for organic fertilisers and organic waste (including compost and animal excretion) δ 15 N can range from +6‰ to + 38‰ in exceptional cases (Cole et al, 2004;Dailer et al, 2010, Derse et al, 2007Jona-Lasinio et al, 2015;Kendall et al, 2007).…”

“…Given their ability to assimilate and store N inputs in their tissues, macroalgae (in marine ecosystems) and epilithon (in river ecosystems) can provide information on anthropogenic N loadings based on changes in their isotopic signatures (Cejudo et al, 2014;Cole et al, 2004;Costanzo et al, 2005;Jones et al, 2004;Pastor et al, 2014;Schiller et al, 2009;Yokoyama and Ishihi, 2006), even on short time scales (Orlandi et al, 2014), reflecting space-time variability in N availability (Jona-Lasinio et al, 2015;Vizzini et al, 2005). Several studies have been performed on macroalgal δ 15 N signatures in marine coastal ecosystems (Cole et al, 2004;Dailer et al, 2010;Gartner et al, 2002;Titlyanov et al, 2011) and coastal brackish lakes (Jona-Lasinio et al, 2015) and lagoons (Vizzini et al, 2005).…”

Lake Water Quality for Human Use and Tourism in Central Italy (Rome)

“…It is widely recognized that tourism represents a strong pressure for various aquatic ecosystems, both marine [29], [30] and freshwater [5], [6], [10]. On the other hand, a lack of knowledge of its effect in lacustrine ecosystems persists and the lake littoral zone might be a useful zone to sample in order to intercept the touristic pressure [31], [32].…”