Abstract Title

The physiological and transcriptional response of harmful algal blooms in nitrogen limited lakes

Start Date

24-5-2022 9:45 AM

End Date

24-5-2022 10:00 AM

Abstract

Nitrogen fixation (NFix), although potentially a significant source of nitrogen (N), is often overlooked or underrepresented in many ecological models. Given the cellular N-demand, and inherent N-rich toxin compounds, NFix may be an important microbial process in proliferating cyanobacterial harmful algal blooms (cHABs) in inland lakes. NFix is a lynchpin in the nitrogen cycle that converts inaccessible dinitrogen, N2, to bioavailable ammonia, NH3. To understand nutrient constraints, specifically N and P, and its effects on the physiological response and gene expression of cHABs we sampled a small, bloom prone lake every two weeks for five months. We monitored shifts and changes in community composition (using metagenomics), nutrients, and NFix rates. Peltier Lake, in Lino Lakes, MN routinely exhibits cHABs that include Dolichospermum, a cyanobacteria capable of producing toxins and fixing N. When Peltier became N-deficient, NFix rates increased from 0.089 nmol N hr-1L-1 to 2.5 nmol N hr-1L-1, roughly a 28x increase. This dramatic increase in NFix could offset the N-demand for the microbial community potentially supporting blooms and funding N to toxin production. Interestingly, Microcystsis, a non-N-fixer was also present in these blooms during N-limiting conditions. Together, this suggests that NFix although generally ignored may be important in cHABs.

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May 24th, 9:45 AM May 24th, 10:00 AM

The physiological and transcriptional response of harmful algal blooms in nitrogen limited lakes

Nitrogen fixation (NFix), although potentially a significant source of nitrogen (N), is often overlooked or underrepresented in many ecological models. Given the cellular N-demand, and inherent N-rich toxin compounds, NFix may be an important microbial process in proliferating cyanobacterial harmful algal blooms (cHABs) in inland lakes. NFix is a lynchpin in the nitrogen cycle that converts inaccessible dinitrogen, N2, to bioavailable ammonia, NH3. To understand nutrient constraints, specifically N and P, and its effects on the physiological response and gene expression of cHABs we sampled a small, bloom prone lake every two weeks for five months. We monitored shifts and changes in community composition (using metagenomics), nutrients, and NFix rates. Peltier Lake, in Lino Lakes, MN routinely exhibits cHABs that include Dolichospermum, a cyanobacteria capable of producing toxins and fixing N. When Peltier became N-deficient, NFix rates increased from 0.089 nmol N hr-1L-1 to 2.5 nmol N hr-1L-1, roughly a 28x increase. This dramatic increase in NFix could offset the N-demand for the microbial community potentially supporting blooms and funding N to toxin production. Interestingly, Microcystsis, a non-N-fixer was also present in these blooms during N-limiting conditions. Together, this suggests that NFix although generally ignored may be important in cHABs.