Validating a novel method to quantify the influence of heterotrophic microbial biofilms on stream ecosystem function

  • Funded By: Notre Dame Environmental Change Initiative
  • ECI Investigators: Brittany Hanrahan, Jennifer Tank

Validating a novel method to quantify the influence of heterotrophic microbial biofilms on stream ecosystem function

Excess fertilizer nutrients, like inorganic nitrogen (N) and phosphorus (P), enter streams from adjacent agricultural lands and cause numerous environmental problems for downstream systems including impaired water quality, compromised food webs, and recurring “dead zones” from senescing algal blooms. Therefore, maximizing the potential of headwater streams to process nutrients prior to downstream export is critical for maintaining healthy freshwater resources. Headwater streams are biogeochemical “hotspots” within watersheds where nutrients from the adjacent terrestrial landscape undergo efficient biological retention and transformations, thereby delaying transport downstream. Previous research at ND-LEEF demonstrated that substrate heterogeneity on the stream bottom and the development of substrate-specific and unique biofilms has the potential to influence nutrient processing at the reach-scale in streams. However, the relative contribution of heterotrophic biofilms to these reach-scale nutrient dynamics is not known. Heterotrophic biofilms (e.g. bacteria and fungi) are major components of stream biofilms (in addition to algae) and are critical to stream ecosystem function, yet their role in biogeochemical cycling is often difficult to partition and hence biofilm activity is treated as a “black box”. 

Using new research techniques, researchers work to “open the black box” of biofilm function, specifically targeting heterotrophic microbial communities and quantify their influence on stream ecosystem function using the experimental streams at ND-LEEF. These results will have implications for managing headwater stream ecosystems to improve their capacity to act as biological filters and reduce the amount of nutrient pollution entering downstream systems, especially in agricultural landscapes. 
 

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