Land use changes biomass and temporal patterns of insect cross-ecosystem flows

Area of Science:

• Ecology
• Environmental Science
• Aquatic Entomology

Background:

• Emergent aquatic insects are crucial food sources, linking aquatic and terrestrial ecosystems.
• Limited understanding exists on how land use impacts insect emergence biomass and composition.
• Previous research lacks annual perspectives, hindering analysis of biomass export and phenological shifts.

Purpose of the Study:

• To investigate the effects of land use on aquatic insect emergence biomass, abundance, and phenology.
• To compare insect emergence between forested and agricultural stream sites over one year.
• To identify key land-use-related environmental drivers influencing insect emergence patterns.

Main Methods:

• Continuous monitoring of biomass, abundance, and identity of over 45,000 aquatic insects.
• Paired study design comparing 20 agricultural stream sites with adjacent upstream forested sites.
• Recording of land-use-related environmental variables, including pesticide toxicity and electrical conductivity.

Main Results:

• Agricultural sites showed higher total insect biomass (2-7 mg day⁻¹ m⁻²) and abundance (7-36 ind day⁻¹ m⁻²) compared to forested sites.
• Observed turnover in insect families, with shorter generation times in agricultural sites suggesting higher resilience.
• Significant shifts in emergence phenology, with earlier peaks in total abundance and biomass in agricultural areas.

Conclusions:

• Land use demonstrably alters the composition and phenology of aquatic insect emergence.
• Pesticide toxicity and electrical conductivity emerged as key drivers of these land-use-related changes.
• Altered insect emergence patterns likely influence food-web dynamics across aquatic-terrestrial ecosystems.