Interannual changes in δ¹⁵N baseline in a lake–swamp–river food web: effects of summer precipitation in West Siberian forest steppe

• Published in: Biogeochemistry 2020-09, Vol.150 (2), p.217-233
• Main Authors: Kanaya, Gen, Yurlova, Natalia I., Yadrenkina, Elena N., Okano, Jun-ichi, Shikano, Shuichi
• Format: Article
• Language: English
• Subjects: Anthropogenic factors; Aquatic habitats; Aquatic plants; Arid regions; Benthic fauna; Benthos; Biogeosciences; Carbon; Catchment area; Catchments; Consumers; Denitrification; Dissolved inorganic carbon; Earth and Environmental Science; Earth Sciences; Ecosystems; Environmental Chemistry; Epiphytes; Evaporation; Fish; Food; Food chains; Food webs; Foods; Fractionation; Hydrology; Inflow; Invertebrates; Isotope fractionation; Isotope ratios; Lakes; Life Sciences; Livestock; Livestock farming; Macrophytes; Microorganisms; Mineral nutrients; Nutrients; Organic matter; ORIGINAL PAPERS; Particulate organic matter; Photosynthesis; Phytoplankton; Plankton; Precipitation; Ratios; Rivers; Sewage; Stable isotopes; Steppes; Swamps; Zoobenthos; Zooplankton
• ISSN: 0168-2563; 1573-515X
• DOI: 10.1007/s10533-020-00694-3

Frequency and intensity of precipitation events can alter hydrological conditions of lotic systems and material inflow from the catchment. In this study, interannual changes in food web structure were investigated in a lake–swamp–river system in the semi-arid West Siberian forest-steppe region using carbon and nitrogen stable isotope ratios (δ¹³C and δ¹⁵N). The δ¹⁵N signatures of aquatic producers and consumers including zooplankton, benthic invertebrates, and fish sharply increased (up to 7.2% in range) in 2009 under high summer precipitation. This would reflect the inflow of ¹⁵N-rich nutrients accumulated in the catchment through natural and anthropogenic activities, e.g., sewage, livestock farming, evaporation, and/or microbial denitrification. In 2010, benthic producers including epiphytes and macrophytes were more ¹³C-enriched, which is likely due to limited supply of dissolved inorganic carbon (DIC) under water stagnation, leading to a large isotopic fractionation during photosynthesis. However, ¹³C-enrichments in the benthic producers were not reflected to those of aquatic consumers in the habitat. Interannual changes in δ¹³C of particulate organic matter (POM; a proxy of phytoplankton) were reflected to those of zooplankton, benthic invertebrates, and fish fry, suggesting the trophic importance of autochthonous phytoplankton in the system. These findings suggest that occasional precipitation events in semi-arid forest-steppe regions can modify nutrient flux from the catchment, leading to changes in δ¹⁵N baseline in the lotic food web.