Assessing Algal Community Structure and Nutrient Uptake Kinetics Across a Nutrient Gradient in Agricultural Streams

• Author / Creator

  van Klaveren, Nikki

• Streams provide important ecosystem services, such as the transformation of organic matter and water purification, while transporting water from headwaters to larger receiving waterbodies downstream. Excess nutrients introduced through anthropogenic land use put stress on aquatic ecosystems and disrupt the ecosystem services we rely on. Current ecosystem health can be determined through structural and functional stream assessments to identify criteria required to maintain ecosystem services. Periphytic algal communities occupy a key position in stream ecosystems through coupling the abiotic environment with aquatic food webs, and are therefore a strong candidate for structural assessment. Nutrient cycling is a critical ecosystem service and a dynamic functional indicator of stream health as uptake saturation limits the capacity of the system to take up nutrients through biotic and abiotic processes. Ecosystem responses to anthropogenic land use and nutrient loading may differ between ecoregions such as the Grassland and Parkland ecoregions found in Alberta, Canada, due to the inherent differences in physicochemical variables affecting the biotic components. Therefore, region-specific nutrient criteria may be required to reflect these differences. Here, we explore both structural and functional metrics of stream function at 55 streams in watersheds that are agriculturally dominated, but with varying degrees of land use pressures such that a gradient in nutrient concentration is established. Periphyton samplers were deployed in each stream for one month in late-spring and again in mid-summer, and harvested algae were identified to genus. Ordination and threshold analyses were conducted to assess the impact of nutrient loading on the biotic components of the stream ecosystems and to identify bioindicator taxa. Nutrient injection experiments were performed in a subset of these streams to assess nutrient uptake kinetics and saturation dynamics, and to determine the limiting nutrient. Nitrogen was determined to be the limiting nutrient in this region by both approaches, but no threshold could be identified through either algal community shifts or uptake saturation. Algal communities appear to be resilient to the nutrient gradient sampled in this study, and continue to contribute to nutrient uptake even at the highest concentrations of nutrients. The results of this research could inform watershed management programs in Alberta's agricultural region by suggesting nutrient criteria that maintain aquatic ecosystem health.

• Subjects / Keywords

  • community structure
  • ecosystem function
  • uptake kinetics
  • nitrogen
  • stream
  • nutrients
  • algae

• Graduation date

  Fall 2020

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-wvph-8t84

• License

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