AN ABSTRACT OF THE THESIS OF Susan A.F. Theis for the degree of Master of Science in Botany and Plant Pathology presented on December 8, 2014. Title: Mitigating Cyanobacterial Harmful Algae Blooms: The Role of Plant Humics Abstract approved: ____________________________________________ Allen J Milligan Abstract: 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. ©Copyright by Susan A.F. Theis December 8, 2014 All Rights Reserved Mitigating Cyanobacterial Harmful Algae Blooms: The Role of Plant Humics by Susan A.F. Theis A THESIS submitted to Oregon State University in partial fulfillment of the requirement for the degree of Master of Science Presented December 8, 2014 Commencement June 2015 Master of Science thesis of Susan A.F. Theis presented on December 8, 2014. APPROVED: ________________________________________________ Major Professor, representing Botany and Plant Pathology ________________________________________________ Head of the Department of Botany and Plant Pathology ________________________________________________ Dean of the Graduate School I understand that my thesis will become part of the permanent collection of Oregon State University libraries. My signature below authorizes release of my thesis to any reader upon request. _________________________________________________ Susan A.F. Theis, Author TABLE OF CONTENTS Page 1. Mitigating Cyanobacterial Harmful Algae Blooms ................................................... 1 1.1 Introduction .......................................................................................................... 3 1.2 Study Site ............................................................................................................. 8 1.3 Materials and Methods ......................................................................................... 8 1.3.1 Plant material ............................................................................................... 9 1.3.2 Mesocosms .................................................................................................. 9 1.3.3 Algal composition ..................................................................................... 10 1.3.4 Time and Dosage ....................................................................................... 10 1.3.5 Data Analysis ............................................................................................ 11 1.3.6 Statistics .................................................................................................... 12 1.4 Results ................................................................................................................ 14 1.4.1 Hordeum vulgare ....................................................................................... 14 1.4.2 Myriophyllum spicatum ............................................................................. 15 1.4.3 Typha latifolia ........................................................................................... 16 1.4.4 Community Results ................................................................................... 18 1.5 Discussion .......................................................................................................... 21 1.5.1 Mechanisms ............................................................................................... 21 1.5.1.1 Reactive Oxygen Species .................................................................... 21 1.5.1.2 HS Components and direct toxicity ................................................... 23 TABLE OF CONTENTS (Continued) Page 1.5.2 Mesocosm Conditions ............................................................................... 24 1.5.2.1 Light Attenuation ............................................................................. 25 1.5.2.2 Microbial Role ..................................................................................... 26 1.5.3 Experimental Effectiveness ....................................................................... 26 1.5.3.1 Nutrient Dynamics ............................................................................. 27 1.5.3.2 Hordeum vulgare ................................................................................ 28 1.5.3.3 Myriophyllum spicatum ...................................................................... 29 1.5.3.4 Typha latifolia .................................................................................... 30 1.5.4 General Phytoplankton Trends .................................................................. 33 1.5.5 Management Implications ..................................................................... …35 1.5.5.1 Wetland Valuation .............................................................................. 37 1.5.5.2 Active Management Strategies ........................................................... 39 1.6 Conclusion ........................................................................................................ 40 Bibliography ................................................................................................................. 65 LIST OF FIGURES Figure Page 1. H. vulgare (barley straw) treatment effects on the growth rates of Microcystis, Ulothrix, Lyngbya, Oscillatoria, and Arthrospira ……………………...41 2. Linear correlation of H. vulgare treatment doses (g/L) and growth rates (µ/d) of Microcystis.........................……………………….………………....42 3. Linear correlation of H. vulgare treatment doses (g/L) and growth rates (µ/d) of Lyngbya……………………………………………………………………...42 4. Linear correlation of H. vulgare treatment doses (g/L) and growth rates (µ/d) of Oscillatoria………………………………………………………………….43 5. Linear correlation of H. vulgare treatment doses (g/L) and growth rates (µ/d) of Arthrospira…………………………………………………………..43 6. Linear correlation of H. vulgare treatment doses (g/L) and growth rates (µ/d) of Microcystis, Lyngbya, Oscillatoria, and Arthrospira………………….44 7. H. vulgare (barley straw) treatments on (A) total phosphorus, (B) soluble reactive phosphorus, and (C) total nitrogen………………………………………..45 8. Myriophyllum spicatum treatment effects on the growth rates of Microcystis, Anabaena, Ulothrix, Lyngbya, Oscillatoria, and Arthrospira…………46 9. Linear correlation of M. spicatum treatment doses (g/L) and growth rates (µ/d) of Microcystis ……………………………………………….................47 10. Linear correlation of M. spicatum treatment doses (g/L) and growth rates (µ/d) of Ulothrix……………………………………………………………………..47 11. Linear correlation of M. spicatum treatment doses (g/L) and growth rates (µ/d) of Lyngbya……………………………………………………………..48 12. Linear correlation of M. spicatum treatment doses (g/L) and growth rates (µ/d) of Arthrospira………………………………………………………….48 13. Linear correlation of M. spicatum treatment doses (g/L) and growth rates (µ/d) of Microcystis, Lyngbya, Oscillatoria, and Arthrospira………………..49 LIST OF FIGURES (Continued) Page 14. M. spicatum treatments on (A) total phosphorus, (B) soluble reactive phosphorus, and (C) total nitrogen ………………………………………………..50 15. Typha latifolia (cattail) green shoot treatments effect on the growth rates of Microcystis, Ulothrix, Lyngbya, Oscillatoria, and Arthrospira….………..51 16. T. latifolia green shoot treatment impacts on (A) total phosphorus, (B) soluble reactive phosphorus, and (C) total nitrogen…..……………..………..52 17. Typha latifolia (cattail) brown shoot treatment effects on the growth rates of Microcystis, Ulothrix, Lyngbya, Oscillatoria, and Arthrospira….….........53 18. Linear correlation of T. latifolia brown shoot treatment doses (g/L) and growth rates (µ/d) of Microcystis ……………..………………………….......54 19. Linear correlation of T. latifolia brown shoot treatment doses (g/L) and growth rates (µ/d) of Lyngbya…………………………………………………54 20. Linear correlation of T. latifolia brown shoot treatment doses (g/L) and growth rates (µ/d) of Microcystis, Lyngbya, Oscillatoria, and Arthrospira………………………………………………………………………...55 21. T. latifolia brown shoot treatments on (A) total phosphorus, (B) soluble reactive phosphorus, and (C) total nitrogen…….…………….…………………...56 22. Typha latifolia (cattail) root treatments effects on the growth rates of Microcystis, Ulothrix, Lyngbya, Oscillatoria, and Arthrospira………….……..57 23. T. latifolia root treatments on (A) total phosphorus, (B) soluble reactive phosphorus, and (C) total nitrogen………………………………………………..58 24. Increases in total phosphorus (µg/L) from controls in treatments significantly inhibiting Microcystis………………………………………….......59 25. Increases in total phosphorus (µg/L) from controls in treatments significantly inhibiting Lyngbya………………………………………………60 26. Increases in total phosphorus (µg/L) from controls in treatments inhibiting Oscillatoria………………………………..……………………….61