Brown meets green: light and nutrients alter detritivore assimilation of microbial nutrients from leaf litter

Area of Science:

• Ecology
• Aquatic Ecosystems
• Microbial Ecology

Background:

• Autotroph-heterotroph microbial interactions are crucial for energy and nutrient transfer in aquatic detrital food webs.
• Understanding these interactions provides insight into bottom-up controls within these ecosystems.

Purpose of the Study:

• To investigate microbial responses to nutrient and light availability during litter decomposition.
• To determine the trophic transfer of microbial carbon and phosphorus to caddisfly larvae (Pycnopsyche sp.).

Main Methods:

• Liriodendron tulipifera litter was subjected to varying nutrient and light conditions.
• Litter-associated microbial biomass and production (algal, fungal, bacterial) were quantified.
• Microbes were labeled with 14C and 33P to trace carbon and phosphorus assimilation and incorporation by Pycnopsyche sp.

Main Results:

• Algal and fungal production increased with higher nutrient and light availability.
• Pycnopsyche sp. assimilated fungal carbon most efficiently and incorporated bacterial carbon most efficiently.
• Fungi supported the majority (89.6-93.1%) of Pycnopsyche sp. carbon growth, with highest overall carbon incorporation in high-nutrient, shaded litter.

Conclusions:

• Autotroph-heterotroph microbial interactions significantly influence energy and nutrient transfer in detrital food webs.
• Fungal biomass plays a dominant role in supporting the growth of detritivores like Pycnopsyche sp.