Blurred Lines: Autotrophic and Heterotrophic Food Resources and Macroinvertebrate Communities in Hea
Abstract Food webs of temperate, forested headwater streams are energetically supported by leaf debris decomposed by microbes and macroinvertebrate shredders. Recent studies suggest algae may influence leaf decomposition and shredder growth. Thus, leaf-associated algae may correspond to macroinvertebrate communities. We manipulated light in three high and three low nutrient streams in Maryland’s Piedmont in winter 2017. In each stream, five red maple leaf bags were exposed to ambient light and five were shaded; macroinvertebrates and algae were recovered from leaves after four weeks. Algal biomass (chlorophyll-a) was significantly higher under ambient light (p<0.001) and high nutrient conditions (p=0.001). Macroinvertebrate abundance exhibited a significant interaction (p=0.006; lowest abundance: ambient light/low nutrient). Total macroinvertebrate biomass and diversity (Hill numbers) did not vary. Predator and collector-filterer abundance was highest in high nutrient conditions (p=0.009, p=0.039, respectively), and collector-filterer abundance was highest in shade (p=0.002). Ephemerellid abundance increased with light (p<0.001), showed a significant interaction (p=0.007), and was significantly correlated to algal biomass (r=0.417, p=0.001). These results suggest specific macroinvertebrate taxa may shift relative to leaf-associated algae although community level responses may be limited. Stream restoration techniques may improve with the application of leaf-algae-macroinvertebrate relationships.
Author: Rebecca Eckert
Institution: University of Maryland
Location: College Park, MD USA