Graduate Thesis Or Dissertation
 

Mitigating cyanobacterial harmful algae blooms : the role of plant humics

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/pn89db20p

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  • Cyanobacterial harmful algae blooms (cyanoHABs) are a growing concern worldwide due to damage of ecosystems and threats to human health. Previous research indicates that plant humics from aquatic and wetland vascular plants are effective inhibitors of cyanobacterial metabolism and growth and may be useful as control agents for mitigating cyanoHABs. Using lake-side incubations, we exposed natural phytoplankton assemblages to plant humics. Three plant species, Hordeum vulgare (barley straw), Typha latifolia (cattail), and the submerged, aquatic invasive Myriophyllum spicatum (Eurasian watermilfoil) were tested for inhibitory effects against cyanobacteria in mesocosm experiments. Trials were conducted on a eutrophied Northern Michigan lake against five cyanobacterial genera (Microcystis, Anabaena, Lyngbya, Oscillatoria, and Arthrospira) and one Chlorophyta (Ulothrix). Lakeside mesocosm experiments were conducted in 3.4L jars containing lake water at continuous oxygen saturation. Treatment effectiveness was assessed via microscopic analysis of cyanobacterial and Chlorophyte biomass. Total phosphorus, soluble reactive phosphorus, and total nitrogen changes were analyzed with each treatment. All treatments significantly inhibited Microcystis growth rates. Anabaena was significantly inhibited by M. spicatum at all doses. Lyngbya was significantly inhibited in over 65% of all treatments. Oscillatoria growth rates were unaffected in all but two treatments, and Ulothrix was unaffected in all but one treatment. Results indicate that plant humic substances are effective in suppressing cyanobacterial growth and that local aquatic plants introduce less phosphorus while exhibiting similar inhibition rates as barley straw. This work suggest that fringing wetlands and submerged aquatic plants may play an important role in regulating harmful cyanobacterial blooms by providing inhibitory humics and that this role should be considered when determining wetland value.
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