The impact of global environmental problems on continental and coastal marine waters ------------------------------------Water related environmental risk of global importance
Global change and cyanobacterial blooms in French freshwater ecosystems Jacquet S, Dufour P, Latour D, Briand JF, Bernard C, Humbert JF
NEAR conference, Geneva, 17 July 2003
What are Cyanobacteria ? Blue-green algae Photosynthetic prokaryotes Long evolutionary history (3.5 Gy) High tolerance to stress (pollution, UV…) Bloom forming species : proliferation phases Toxic forms Ecological implications
Cyanobacterial blooms result from competitive situations between phytoplanktonic species
Environmental factors favoring these situations : ! Nutrient pollution (54 % of eutrophic lakes in Europe) !
Stability and “high” temperature of the water column (blooms occur principally in summer)
Why cyanobacteria are often the winner in competitive situations ? - Control of their buoyancy - Heterocysts , akinetes - Photo-heterotrophic - High reserve capacities - Accessory pigments (ex: phycoerythrin) - Multicellular organization (filaments, colonies) - Poor food quality - Synthesis of toxins
nutrient/light uptake & resistance
defense against predation
… and the winner is:
Impacts of cyanobacteria ! Ecological impact : - Perturbations of the ecosystem functioning - Shade - toxin accumulation and transfer thru the trophic chains - Anoxia at the end of the bloom ! Sanitary impacts : - Mortality and morbidity in aquatic and terrestrial invertebrates and vertebrates Example: In Switzerland, more than 100 cattle deaths were attributed during the last two decades to cyanotoxin poisoning
- Human contamination
Human poisoning by cyanotoxins ! Short term effects - Gastrointestinal and/or hepatic illnesses - Death of kidney dialysis patients in Brazil ! Chronic term effects - Hepatic carcinoma
Principal routes of exposure ! Oral exposure through drinking water, ! Oral and dermal exposure trough recreational water use ! Oral exposure through consumption of toxic products and/or algal health food tablets ! Haemo-dialysis
What is global change ? Eutrophisation / re-oligotrophisation (restoration) (phosphorus) Increase of temperature (warmer winter and springs) Urbanization of catchment's area (more inhabitants and constructions around the lakes) New types of pollution (agriculture, industry & domestic sources)
4 case-studies in France # Planktothrix rubescens in Lake Bourget # Planktothrix agardhii in Lake Viry # Microcystis aeruginosa in Grangent reservoir # Cylindrospermopsis raciborskii in the Francs-Pécheurs pond
The case of Planktothrix rubescens Decrease of P from 120 µg/l to 30 µg/l in the last 20 years In the largest natural French lake: Lake Bourget BUT problems with the toxic cyanobacterium P. rubescens since 1996-97
Lake Bourget
The case of Planktothrix rubescens in Lake Bourget 0m
50 m July 99
April 00
July 00
April 01
MCYS-RR (µg/l) 6
10 m 15 m
5 4
20 m
WHO drinking water guideline conc. of 1µg/l
3 2 1
03
-a oû t-9 31 9 -a oû t-9 9 13 -s ep t-9 9 29 -s ep t-9 9 14 -o ct -9 9 03 -n ov -9 9 16 -n ov -9 9 29 -n ov -9 9 07 -d éc -9 9 22 -d éc -9 05 9 -ja nv -0 18 0 -ja nv -0 31 0 -ja nv -0 0 15 -fé vr -0 0
0
July 01
April 02
How to explain P. rubescens bloom since 6 years ?
P +++
24 °C
P +++
P +++
PP+
7 °C
Eutrophic conditions
P +++ Meso-trophic conditions
P. rubescens is - low light, low temperature, low nutrient adapted - photo-heterotrophic - filamentous and toxic and hence little grazed - probably little affected by parasitism (viruses) - able to regulate its buoyancy - enhanced by P pulses, …
A possible scenario Climatic influence = Warmer winter & spring
Advance of spring bloom & zooplankton development = Advance in population decline & advance of clear water phase
Human pressure = Reduction of P
Advance of P-depleted Surface waters = Sinking of population & the P-depleted zone
Very competitive species for the new environmental conditions: low nutrient, low light of metalimnion
Planktothrix rubescens Low grazing, low viral attack, stable water column
The case of Microcystis aeruginosa Grangent reservoir
The case of Microcystis aeruginosa water 0,5 m
Sediment 0-2cm
100
1500 1000
50 500 0
Sediment colonies.mL-1
Water colonies.L-1
2000
0 1/4
1/5
1/6
1/7
= recruitment from benthic colonies Cause: O2 reduction = growth stimulation and back of floatability
The case of Microcystis aeruginosa Benthic colonies
12
1200
8
800
4
400
0
0 1/2
1/3
1/4
1/5
1/6
1/7
Colonies.ml-1
Temperature (°C)
Temperature at 40m
1/8
Cause : Temperature elevation of hypolimnion (>8°C) = metabolic activity, bloom and surface accumulation
The case of Microcystis aeruginosa 2000 No bloom
400
8
8°C 4
200
0
0 1/4
1/5
1/6
1/7
1/8
M. aeruginosa
800
600
12
8°C
8
8°C
400
4 200
0
0 1/4
1/5
1/6
1/7
1/8
In this context, increasing temperature (global warming) will increase the problem of this eutrophicated ecosystem ?
Temperature (°C)
8°C
temperature 12
Colonies.L-1
Colonies.L-1
600
M. aeruginosa
Temperature (°C)
temperature
800
2001 Bloom
The case of Planktothrix agardhii • Filamentous, uniseriate • Maximum length : 300 µm • no mucilage • non colony forming • Gas vesicles • no heterocysts • no akinetes • European northern area : Scandinavia,Estonia, Germany, The Netherlands, France…), also Japan, Korea and Minnesota (United States) • The more southern countries : Spain and Florida (US)
The case of Planktothrix agardhii
Viry-Châtillon, 25 km south of Paris, France Surface : 978 000 m2 Depth : 5.3 m max 2.8 m mean Main activity : fishing, sailing, water-skiing
The case of Planktothrix agardhii
4,5E+06
90
4,0E+06
80
3,5E+06
70
3,0E+06
60
2,5E+06
50
2,0E+06
40
1,5E+06
30
1,0E+06
20
5,0E+05
10
0,0E+00
0
6,0
5,0
MCYST-LR eq. (µg / L)
100
4,0
3,0
2,0
1,0
0,0 20 /0 1/ 99 24 /0 2/ 99 25 /0 3/ 99 20 /0 4/ 99 18 /0 5/ 99 22 /0 6/ 99 20 /0 7/ 99 18 /0 8/ 99 23 /0 9/ 99 14 /1 0/ 99 16 /1 1/ 99 16 /1 2/ 99 03 /0 2/ 00
5,0E+06
conc. chl.(µg/L), Secchi disk (cm)
trichomes nb / L
Viry-Châtillon recreational area
H2O (PP2A)
Cells (HPLC-DAD)
20
/0 1 24 /99 /0 2 25 /99 /0 3 20 /99 /0 4 18 /99 /0 5 22 /99 /0 6 20 /99 /0 7 18 /99 /0 8 23 /99 /0 9 14 /99 /1 0 16 /99 /1 1 16 /99 /1 2 03 /99 /0 2/ 00
Cells (PP2A)
P. agardhii
L. redekei (x10)
chl. a
Secchi disk
2.3 ± 1.9 µg/L MCYST-LR eq. (cells) • perenial bloom of P. agardhii • only one associated microalgae : max. : 5.2 µg/L MCYST-LR eq. (cells) Limnothrix redekei (Cyanobacteria)
The case of Planktothrix agardhii
$ eutrophication $ perennial bloom $ Highest P. agardhii biomass not correlated with highest MCYSTs concentrations $ High MCYSTs concentrations $ Contamination of the food web ? $ Public health threats
The case of Cylindrospermopsis raciborskii
C. raciborskii = filamentous
cyanobacteria with heterocyst & akinetes producing hepatotoxins (cylindrospermopsin) & neurotoxins (PSP) Important sanitary problems in Australia and south America
The case of Cylindrospermopsis raciborskii ! Present on all continents ! initially described as a typical tropical & sub-tropical species ! For the last 50 years, colonization of latitudes further north : - Central Asia in the 1950’s - Greece in the 40’s - Hungria in the 60’s - Volga in the 60’s - Austria in the 90’s - France - Germany
The case of Cylindrospermopsis raciborskii
Questions : ! What is the origin of invading strains in France ? ! Why this tropical strain occurs under temperate latitudes by now ? The 3 working hypotheses : ! Clone selection of C. raciborskii, adapted to temperate climate, while colonization of the species towards north ! High temperature tolerance of C. raciborskii for growth in very different conditions ! Global warming increases the probability of encountering good conditions for C. raciborskii growth
The case of Cylindrospermopsis raciborskii
RBRE2 RBRE1 CBRE1 CBRE2 CMEX CBRE3
16S ITS1 rpoC1 nifH
99
AF118 AF115
99
CAUS60 CAUS99 CAUS59
South and central America
0.01
99
CFRAN1 CFRAN2 AF117
Australia + Africa
CAL66
CFRAN3 CHON
Europe
The case of Cylindrospermopsis raciborskii
The case of Cylindrospermopsis raciborskii 0.5
0.9
0.4
0.8 0.7
0.3
µ (d-1)
µ (d-1)
0.6
0.2 0.1
0.5 0.4
0.0
0.3
-0.1
0.2 0.1
-0.2 10
15
20
25
30
35
Temperatures (°C)
40
45
0 0
50
100
150
200
250
300
350
400
450
Light Intensity (µEm-2s-1)
! No selection of C. raciborskii clones adapted to temperate climate ! Tolerance to a wide range of light and temperature with optima corresponding to typical tropical conditions (30°C). Global warming could favor the dispersion
500
Conclusions & “take home messages” Developments of freshwater toxic cyanobacteria have a negative impact on biodiversity, ecosystem functioning and potentially animal and human health. These proliferations can occur everywhere and health risks for terrestrial vertebrates are still largely ignored almost everywhere. Note also that the toxicity of many cyanobacteria is due to unknown toxins to date. SO: - More awareness & surveys are required with efficient monitoring tools ; - Take care about eutrophication but also of re-oligotrophisation processes (no real rule), species-dependent situations ; - Have in mind that global change (typically warmer winters and springs) is likely to favor these proliferations ; - We know almost nothing about toxin accumulation and transfer thru the food web : a very important research perspective.
