cyanobacteria and potentially toxin-producing species in lake … · 2019-02-20 · cyanobacteria...

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

Lake Sevan

Lake Sevan –

River Hrazdan –

Lake Yerevan

Cascade

(1965-1968)

40°9′35.04″N and 44°28′36.54″E

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)

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

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

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.

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)

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

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).

The Lake Yerevan shoreline

The Hrazdan Gorge

Sewage discharge

Gorge with spring

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!!!

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

Thank you very much

Acknowledgments:

Prof. Dr. Herwig StiborProf. Dr. Linda Lawton

Dr. Triantafyllos Kaloudis