Sammanfattning

Emerging aquatic insects link aquatic and adjacent terrestrial food webs by subsidizing terrestrial predators with high -quality prey. One of the main constituents of aquatic subsidy, the non-biting midges (Chironomidae), showed altered emergence dynamics in response to the mosquito control agent Bacillus thuringiensis var. israelensis (Bti). As riparian spi-ders depend on aquatic subsidy, they may be affected by such changes in prey availability. Thus, we conducted a field study in twelve floodplain pond mesocosms (FPMs), six were treated with Bti (2.88 x 109 ITU/ha, VectoBac WDG) three times, to investigate if the Bti-induced shift in chironomid emergence dynamics is reflected in their nutritional value and in the diet of riparian spiders. We measured the content of proteins, lipids, glycogen, and carbohydrates in emerged Chironomidae, and determined the stable isotope ratios of female Tetragnatha extensa, a web-building spi-der living in the riparian vegetation of the FPMs. We analysed the proportion of aquatic prey in spiders' diet, niche size, and trophic position. While the content of nutrients and thus the prey quality was not significantly altered by Bti, ef-fects on the spiders' diet were observed. The trophic position of T. extensa from Bti-treated FPMs was lower compared to the control while the aquatic proportion was only minimally reduced. We assume that spiders fed more on terrestrial prey but also on other aquatic organisms such as Baetidae, whose emergence was unaffected by Bti. In contrast to the partly predaceous Chironomidae, consumption of aquatic and terrestrial primary consumers potentially explains the observed lower trophic position of spiders from Bti-treated FPMs. As prey organisms vary in their quality the suggested dietary shift could transfer previously observed effects of Bti to riparian spiders conceivably affecting their populations. Our results further support that anthropogenic stressors in aquatic ecosystems may translate to terrestrial predators through aquatic subsidy.

Nyckelord

Chironomidae; Tetragnatha extensa; Stable isotope analysis; Nutrient content; Bacillus thuringiensis var; israelensis; Aquatic -terrestrial linkage

Publicerad i

Science of the Total Environment
2023, Volym: 873, artikelnummer: 162351
Utgivare: ELSEVIER

SLU författare

• Bundschuh, Mirco

  • Institutionen för vatten och miljö, Sveriges lantbruksuniversitet
    
  • Rheinland-Pfälzische Technische Universität Kaiserslautern-Landau (RPTU)

Globala målen

Skydda, återställa och främja ett hållbart nyttjande av landbaserade ekosystem, hållbart bruka skogar, bekämpa ökenspridning, hejda och vrida tillbaka markförstöringen samt hejda förlusten av biologisk mångfald


UKÄ forskningsämne

Ekologi
Miljövetenskap


Publikationens identifierare

DOI: https://doi.org/10.1016/j.scitotenv.2023.162351

Permanent länk till denna sida (URI)

https://res.slu.se/id/publ/121825