Magnesium and zinc stable isotopes as a new tool to understand Mg and Zn sources in stream food webs. Issue 8 (26th August 2020)

• Record Type: Journal Article
• Authors: Nitzsche, Kai Nils; Shin, Ki‐Cheol; Kato, Yoshikazu; Kamauchi, Hiromitsu; Takano, Shotaro; Tayasu, Ichiro
• Is Part Of: Ecosphere. Volume 11:Issue 8(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-08-26
• Subjects: aquatic macroinvertebrates -- feeding habits -- goby -- magnesium -- non‐traditional stable isotopes -- stream -- zinc; Ecology -- Periodicals; Ecology; Periodicals; 577.05
• DOI: 10.1002/ecs2.3197
• Languages: English
• ISSNs: 2150-8925

Abstract

Abstract: Non‐traditional stable isotopes of metals were recently shown as new dietary tracers in terrestrial and marine mammals. Whether these metal stable isotopes can be used to understand feeding habits in stream food webs is not known yet. In this study, we explored the potential of stable isotopes of essential Mg (δ 26 Mg) and Zn (δ 66 Zn) as a new tool in stream ecology. For this purpose, we determined δ 26 Mg and δ 66 Zn values of stream organisms and their potential metal sources in upper and lower reaches of two streams in the Lake Biwa catchment, Central Japan. Our goals were (1) to explore variations in δ 26 Mg and δ 66 Zn across organisms of different feeding habits and (2) to understand Mg and Zn sources to stream organisms. Overall, δ 26 Mg and δ 66 Zn values of organisms were neither related to each other, nor to δ 13 C and δ 15 N values, indicating different elemental sources and factors controlling isotopic fractionation depending on element and taxa. Low δ 26 Mg values in filter‐feeding caddisfly larvae and small gobies indicated aqueous Mg uptake. Higher δ 26 Mg values in leaf‐shredding crane fly and grazing mayfly larvae suggested Mg isotopic fractionation during Mg uptake from the diet. While the δ 26 Mg values of stonefly nymphs reflected those of caddisfly larvae as a potential prey, the highest δ 26 Mg values found in dobsonfly nymphs can be explained by 26 Mg enrichment during maturing. δ 66 Zn values of caddisfly and mayfly larvae indicated Zn was a mixture of aqueous and dietary available Zn, while higher δ 66 Zn values in crane fly larvae pointed to Zn isotopic fractionation during Zn uptake from plant litter. δ 66 Zn values in stonefly and dobsonfly nymphs were often in the range of those of caddisfly larvae as their prey, while dragonfly nymphs and small goby were depleted in 66 Zn relative to their dietary Zn sources. We conclude that δ 26 Mg is a promising indicator to assess Mg sources in stream ecology depending on taxa, while the use of δ 66 Zn is limited due to the complexity in Zn sources.