Aquatic subsidies transport anthropogenic nitrogen to riparian spiders

摘要

Stable nitrogen isotopic composition (δ~(15)N) of aquatic biota increases with anthropogenic N inputs such as sewage and livestock waste downstream. Increase in δ~(15)N of riparian spiders downstream may reflect the anthropogenic pollution exposure through predation on aquatic insects. A two-source mixing model based on stable carbon isotopic composition showed the greatest dependence on aquatic insects (84%) by horizontal web-building spiders, followed by intermediate (48%) and low (31%) dependence by cursorial and vertical web-building spiders, respectively. The spider body size was negatively correlated with the dietary proportion of aquatic insects and spider δ~(15)N. The aquatic subsidies transported anthropogenic N to smaller riparian spiders downstream. This transport of anthropogenic N was regulated by spider's guild designation and body size.