Fondriest Environmental is at the Water Management Association of Ohio‘s 43rd annual conference in Columbus this week, where the theme is “Valuing Water: Exploring the interactions between people, markets and water.” Our Paul Nieberding is exhibiting, so be sure to stop by and see him between sessions.
The conference proceedings (PDF) list an impressive array of presentations this year, including one from Justin Chaffin, research coordinator at The Ohio State University’s Stone Laboratory.
We spoke with Chaffin for a 2013 story on his study of a record-setting harmful algal bloom on Lake Erie, and then again for an industry profile piece that originally appeared in the Summer 2013 issue of the Environmental Monitor’s quarterly print edition. His WMAO presentation covers nitrogen enrichment experiments on cyanobacteria blooms in Grand Lake St. Marys and in Lake Erie’s Maumee and Sandusky Bays. Here’s the abstract:
Blooms of cyanobacteria often occur in waters that have high phosphorus (P) and low nitrogen (N) concentrations, and the growth rate of the cyanobacteria is often constrained by N. For these reasons, many scientists have suggested that regulation of both P and N is required to prevent blooms. However, because N occurs in many bioavailable forms, regulation of a particular form may be beneficial rather than regulation of all N forms. To address how N- stressed cyanobacteria growth and toxin production responds to various N inputs, N enrichment experiments (nitrate, ammonium, urea) were performed during N-limited cyanobacterial blooms in Maumee and Sandusky Bays of Lake Erie and in Grand Lake St. Marys (GLSM). Bioavailable N (nitrate, urea, and ammonium) concentrations were also determined. Microcystis aeruginosa dominated the Maumee Bay bloom, where the highest growth rates were in response to ammonium additions, and lowest growth rates were in response to nitrate. Urea resulted in intermediate growth rates. All forms of N resulted in similar microcystin concentrations that were greater than control and phosphate-only enrichment. Planktothrix agardhii dominated the Sandusky Bay and GLSM blooms, where nitrate, ammonium, and urea addition resulted in similar growth rates and microcystin concentrations. Incubations using stable isotope 15N showed the cyanobacteria had a preference for ammonium, but the other N forms were also assimilated in the presence of ammonium. These results show that cyanobacterial blooms will assimilate multiple forms of N to support growth and microcystin production. These results suggest that N loadings above current levels will exacerbate cyanobacterial bloom, but do not answer the question regarding the need to lower N loading. However, all forms of bioavailable N need to be constrained if lake managers do decide that N abatement is needed.