Mitigating Freshwater Cyanobacteria Blooms

K.G. Sellner1, A. Place2, M. Paolisso3, Y. Gao4, E. Williams2, E. VanDolah3, J. Biondi1, & S. Shah5

1Chesapeake Research Consortium, Edgewater, MD, USA

2Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Sciences, Baltimore, MD, USA 3Department of Anthropology, University of Maryland, College Park, MD, USA

4Horn Point Laboratory, University of Maryland Center for Environmental Sciences, Cambridge, MD, USA 5GEMSTONE Program, University of Maryland, College Park, MD, USA

NOAA HAB-PCM Grant NA10NOS4780154

Microcystis Blooms on MD’s Eastern Shore, USA

• Dog mortalities in 24-48 h in 2009 at Higgins Mill Pond; [microcystin] = 2 x 104 µg/L. Continued blooms today

• Summer blooms in Lake Williston in 2009-2011, exceeding WHO levels for recreational use

• Goal: To adapt Chinese freshwater sediment-cyanobacteria flocculation technology for MD waters as a potential routine mitigation technique by non-science personnel

– Any local sediment + chitosan

– 100 mg sed/L + 10 mg chitosan

• Foundation: GEMSTONE Team lab results (Crete, 2010)

• Preliminary flocculation expt. in 2011 at Williston brought cyanobacteria to the bottom

Established Methods: Preliminary Lab Results

To minimize costs + facilitate easy mixing in the field

• Pan et al. (2006) chitosan soln lowers pH<4; same soln in diluted table vinegar (0.5% HAc) & filtered lake water results in pH>6.7

• Flocculation as effective (97%-98% in 51 h)

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Hac&DI stan stan+chit DI Control

t50=25 h

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vin&LW stan stan+chit LW Control

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[200 mg sed+50 mg chit]/L

Preliminary Lab Results

Contrary to Pan et al. (2006), little flocculation at

[100 mg sed+10 mg chit]/L regardless of sediment size or

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Stancill's Clay

stan, no chit stan+10 mg chit stan+25 mg chit stan+50 mg chit

Sand Flocculation of HMP Blooms • Greater flocculation of cyanobacteria with smaller sand grain size &

chitosan addition (similar result for all Chl a) • Much more sediment & chitosan required vs. Pan et al. (2006)

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Stancill’s Clay Flocculation of HMP Blooms

• To rapidly remove HMP cyanobacteria blooms, must add very high sediment & chitosan levels

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Note: Near 100% & faster removal at [5 g Stancill’s+0.15 g Chit/L] vs. SANDS+Chit

Summary Table of Flocculation Abilities for Field Blooms

SEDIMENT + CHITOSAN/L t50 (h)

1.5 g <125 µm SAND + 0.03 g 6.9

3 g 125-250 µm SAND + 0.06 g 2

5 g <125 µm SAND + 0.15 g 0.98

5 g 125-250 µm SAND + 0.15 g 1.15

1.5 g STANCILL’S + 0.03 g 28.19

3 g STANCILL’S + 0.06 g 20.44

5 g STANCILL’S + 0.15 g 0.3

102 g STANCILL’S + 1.235 g to 4650 L* 0.16

All other lower concentrations of sediments with or without chitosan never removed 50% of bloom cyanobacteria

t50 = time (h) to remove 50% of the field cyanobacteria bloom

*October, low cyanobacteria abundance

Lake Draining+Barley Straw: Cyanobacteria from Cores

Geitlerinema acutissimum

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Incubated Samples, Chl/PC<10

Core/Water Over Core PC Growth

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Pseudanabaena sp.

Synechococcus

•Cyanobacteria bloom in 2011 with microcystin >10 ug/L •Drained lake in fall, flushing bloom and sedimented vegetative populations out •Exposed 2/3 of lake bottom for >5 months •Deployed barley straw along lake shore in early spring •Collected and incubated cores in May 2012, gradual inc to 28.5oC •For samples with chl/PC<10, collected samples for PP composition

RESULT: No Microcystis from cores or overlying water

Barley Straw & M. aeruginosa • Previous lab & field results

have indicated barley straw effects on freshwater cyanobacteria

• M. aeruginosa LE3 + 4.5 & 9.1 g barley straw/L

• 46% reduction in M. aeruginosa over 29 d, with removal beginning at day 13

• Extract from water logged barley straw inhibited cultured M. aeruginosa growth on occasion

• Short half-life of extract

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Removal Effic=46%,

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2012 Lake Draining + Barley Straw

• Absence of vegetative Microcystis in sediments

• Very late appearance of M. aeruginosa

• Low toxin levels Oct July

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2013 Barley Straw

• Just begun barley straw bale deployments in – Lake Williston (yr 2)

– 240 acre saline (S=11) pond on dredge material island in Chesapeake Bay

• Monitoring sediment & water column cyanobacteria & toxins

Future Research

• Large 4 m3 lake limnocorral expts (before, during, late bloom)

• Chitosan additions, then sediment? • Kill surface bloom, then

flocculate+ballast • Conduct ‘impacts’ assessments (fish,

in- and epi-fauna) • Assess lake draining/flushing effects • Barely straw exposures in lake & saline

pond: cyano growth & toxin production

• Hand-off effective, inexpensive strategies to state for routine use?

So Practical, Inexpensive Options for Freshwaters/Tidal-freshwaters?

• Little confidence in previously published clay flocculation results for freshwaters, i.e., any sediment + low chitosan can remove Microcystis

• Sediment additions effective in removing Microcystis in freshwaters are far above TSS levels permitted in loads allowed

• Increasing chitosan concentrations might work but then $$$ become an issue

• Lake draining & pre-bloom barley straw looks promising and are CHEAP!

Management in Future

Ultimately mitigation is a BAND-AID for much larger problem of nutrient load reductions

Need political will to

manage land use to insure nutrient inputs decline

Acknowledgements • G. acutissimum: http://nordicmicroalgae.org/taxon/Geitlerinema%20amphibiium; F. Acker, ANSP

• Pseudanabaena: http://enpub.fulton.asu.edu/pwest/myweb/Taste%20and%20Odor%20Stuff/Taxonomic%20guide/Guide_Images/Pseudanabaena_2_photos.html

• Synechococcus: http://protist.i.hosei.ac.jp/pdb/images/Prokaryotes/Chroococcaceae/Synechococcus/index.html

• Stancill’s = kaolinite, illite, and some quartz (D. Vanko, pers. comm.)