Cyanobacteria and potentially toxin-producing species in Lake … · 2019-02-20 · Cyanobacteria...
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CyanoCost Action ES1105
Armenia as a near neighbour country
Cyanobacteria and potentially toxin-
producing species in Lake Yerevan (Armenia)
Dr. Arevik Minasyan
UNESCO Chair in Life Sciences
International Post-graduate
Educational Center, Armenia
19-21-th February, 2015, Seville, Spain
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Lake Sevan
Lake Sevan –
River Hrazdan –
Lake Yerevan
Cascade
(1965-1968)
40°9′35.04″N and 44°28′36.54″E
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Physico-chemical and hydrological characteristics of Lake Yerevan basin
• with typical low mixing, stratified with thermal column formation
• a surface elevation of 908 m
• water level manipulation up to the point of a surface elevation of 895 m (max)
• initial reservoir volume 0.005 km3
• present-day reservoir volume 0.004 km3
• bottom sediments volume about 25% of the initial volume
• shoreline = 6.3 km
• a surface area is 0.65 km2
• a maximal depth of 22 m
• T°C = +1 +2°C - +27 +28°C
• transparency 0.5 - 2 m
• pH = 8.09 – 8.37
(some data were provided by the HAYJRNAKHAGITS INSTITUTE CJSC)
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Proportional cyanobacterial biovolume in epilimnion
of Lake Yerevan (May-October, 2012/2013 – X 1 and
X 2 stations; May-October, 2014, X 1 – X 7 stations).
Biovolume calculation was performed with the method after Hillebrand et
al., 1999
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Total abundance of cyanobacterial cells in epilimnion of Lake Yerevan
Total abundance of CB in in-shore waters (X 1 – left bank, X 2 – right bank) of Lake Yerevan (cells ml-1) (May-October, 2012/2013/2014)
Total density of CB in photic zone of Lake Yerevan in May-October of 2014 (cells ml-1) (entry – X
3, center – X 4, near-shores – X 6 – left bank, and X 7 – right bank, and exit X 5 (cells ml-1)Sampling stations of Lake Yerevan
Nostoc linckia
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Nutrients? or/and Temperature?
less sunny area,
cold and wet,
subdominating by
Aphanothece/
Aphanocapsa
sunny area, hot,
dry dominating
by Microcystis/
Anabaena
intermediate,
transitional area
subdominating by
Planktothrix
Higher NO3- N level shifts the advantage
to Microcystis (Lehman et al. 2009).
10 x NH 4 -N > NO 3 -N > N 2
(Tandeau de Marsac and Houmard 1993)
Microcystis is a phosphate
storage specialist
(Kilham & Hecky 1988)
Microcystis ki = 0.8 h.
(Kromkamp et al. 1989)
“TN/TP rule” > 17 (mol: > 38)
TP = 15 - 100 μg/L
mesotrophic - eutrophic
TN = 401 - 1500 μg/L
meso=-eutrophic
Euphotic zone of Lake Yerevan
is phosphorus-limited
water level
± 13 m ≈ 0.5˚C
Anabaena sp. N:P ratios from 1,000:1 to 10:1
(Nalewajko and Murphy 2001)
Planktothrix agardhii -
high TP and low light
availability conditions.
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There are more than 50 morphospecies of Microcystis described, with 20 in temperate regions
and at least 11 in Europe (Komárek & Anagnostidis 1998; Komárek & Komárková 2002).
The main morphospecies of Microcystis in Europe: M. ichthyoblabe (icht) , M. fl os-aquae (f-a), M. aeruginosa (aer), M. Novacekii (nov),
M. viridis (vir), M. wesenbergii (wes); p (plankton), b (benthic). (Photos by Dr. Lenka Šejnohová, in: Ecology of Cyanobacteria II. Their
Diversity in Space and Time. Editor: Prof. Dr. Brian Whitton)
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Saxitoxins are classifiedas Scheduled Chemical
Weapons(Metcalf and Codd 2009)
A potential risk assessment
Three Microcystis genera based on oligopeptides spectrum:
• M. aeruginosa with microcystins and aeruginosins,
• M. ichthyoblabe with anabaenopeptins and microginins (Šejnohová et al. 2011);
• M. wesenbergii with cyanopeptolins and unknown peptides (Fastner et al. 2001).
For Anabaena genera based on toxins (Codd et al. 2005)
•microcystins
•anatoxin-a and homoanatoxin-a
•saxitoxins
•cylindrospermopsins
For Planktothrix genera based on toxins (Codd et al. 2005)
•microcystins
•saxitoxins
Internet photos by unknown author photo by A. Minasyan
Microcystis
aeruginosa
Planktothrix
agardhiiAnabaena
planktonica
Anabaena
flos-aquae
Anabaena
circilanis
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Water Sports?
Drinking?
Fishing?
Wildlife
conservation?
Irrigation?
Rest
zone?
Microcystins chemically stable molecules
survive extended boiling
(half-life, about 24 h)
and pH = 1 - 10 (Codd and Bell 1996).
Boiling of acidic solutions of saxitoxins induce
more toxic variants (Etheridge 2010).
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The Lake Yerevan shoreline
The Hrazdan Gorge
Sewage discharge
Gorge with spring
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World Health Organization (WHO, 2003)
for recreational waters
5000 cyanobacterial cells/ml
mild irritative effect
20000 cyanobacterial cells/ml
2– 4 µg microcystin/litre may be expected
up to 10 µg/litre being possible with highly toxic
blooms.
100000 cyanobacterial cells/ml
20 µg microcystin/litre
Microcystis has an average toxin content of
0.2 pg/cell.
Low Risk - < 10 ppb
Moderate Risk - 10-20 ppb
High Risk - > 20 ppb
Guidelines For Cyanobacteria in
Freshwater Recreational
Water Bodies
• Massachusetts Department of Public
Health (MDPH)
• Canadian Guideline
• Australian Guideline
• Oregon Health Authority (OHA)
Actual and/or
potential risk!!!
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Clean Waterfor Everybody =
= towards the World’s Better Future
The methods to mitigate water cyanobacterial bloom:
Hypolimnetic aeration to reduce the number of benthic
Microcystis colonies.
Water artificial mixing - specifically to prevent Microcystis
blooms (Chen et al. 2009)
Controlled strategy combining P reduction with the
transport of hypolimnetic water rich in free CO2 to the
epilimnion
Aeration accompanied by light-shading
Recovery of greenzone (especially the shoreline
macrophytic layer)
Hydrogen peroxide for selective suppression of harmful
cyanobacteria (Matthijs, H. & Visser, P., 2012)
Chlorination and ozonation (US EPA)
Mechanical cleaning
Cyanotoxins degradation:
Photocatalytic treatment (TiO2, light absorbtion) (L.Lawton
et al.)
Bacterial degradation of cyanotoxins (the bacterial
species/strains of Sphingomonas, Sphingocinicella,
Arthrobacter, Brevibacterium, Rhodococcus and
Burkholderia (Kato et al. 2009)
TOXIC
CYANOS
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Thank you very much
Acknowledgments:
Prof. Dr. Herwig StiborProf. Dr. Linda Lawton
Dr. Triantafyllos Kaloudis