Evaluation of end-of-pipe measures proposed for controlling cyanobacteria blooms and other things people might do in these
Miquel Lürling, Els Faassen, Lisette de Senerpont Domis,, Guido Waajen, Frank van Oosterhout, Yora Tolman Methods Beating the Blues
1) Source oriented (nutrients) 2) Public oriented (exposure) 3) Effect oriented (blooms/scums)
Set of measures per water(type) Dredging Wet dredging is also active fish removal Restoration 1000 Ecological De Ploeg condition Bergen-op-Zoom 1000 Cyanobacteria )
800 -1 Authorities decided: Eukaryote algae 500 g l g -600 Dredging Dredging µ Bad 200 400 - Fish stock manipulationVariable results dredging 95 200
- Remove sewer overflow 3 Poor 0 46 Etten-Leur (€25-60 per m sediment)
800 ( concentration Moderate - Creating soft banks a 23 Good 600 - Planting macrophytes 10.8 ) -1 400 6.8 Excellent -l g Inform citizens feeding µ
( → System analysis?Chlorophyll- a 200 3 ducks/fish 7 8 9 0 1 2 0 0 1 1 00 01 014 0 20 20 2 20 20 2 2013 2 Someren 500 Molenwiel 350 Year 400 Chlorophyll- )
-1 Total CHL-a → 300 Authorities300 decided: Cheaper alternatives?Cyanobacteria CHL-a g L g median 2006-2012 µ 200 - Dredging 250 100 - Creating few soft banks 200 0 -600 PlantingBennekom2006 2008macrophytes2010 2012 2014 Jaar 150 concentration ( concentration 400 a 100 - Fisherman reintroduced fish 200 50
Chlorophyll- 0 0 2006 2008 2010 2012 2014 2006 2007 2008 2009 2010 2011 2012 2013 2014 Year Year Combination of measures: - Dredging - Fish stock manipulation - Water level fluctuation (less pump) - Creating soft banks - Planting macrophytes - Prohibition dog outlet - Restricting in feeding water birds - No carps, no baiting Restoration Restoration EcologicalEcological condition condition )
-1 1500 )
-1 1000 g l g 1000 µ Bad
g l Bad
µ 500 500
360200 Poor 95 Poor 180 46 Moderate
concentration ( concentration Moderate 90 a 23 Good Good 10.840 6.8 Excellent Total P concentration ( Excellent 20 3 Chlorophyll-
ol l ol ol d ol tr d ond ntrr trontr trol nd ond P o n o n o P -C C 09- 9 0- 1-Con2-Pon 13-Pond 14- 0 -Co1 -Co1 1 0 0 2 00 0 1 2012-Pon 2014-P 2 2009-Pond2 0120 01 20 20 2013-Pond2 2009-Cont2 2 YearYear Restoration
l o ol tr r d n n o o -C -Cont -Pond P 0 1 2 009-Pond 01 01 01 2 2 2 2 2013-Pond 2014- Sd (m) 0.22 0.24 0.23 0.50 0.60 0.63 TP (µg/L) 366 548 585 46 26 22 TN (mg/L) 3.42 2.57 2.93 0.44 0.82 0.82
O2 (%) 68 115 105 99 95 89 pH 6.8 8.1 8.3 7.9 7.7 7.8 CYA-CHLa 206.4 20.3 25.0 11.6 0.1 0.3 Total-CHLa 410.9 322.3 269.9 26.2 7.7 8.8 2) Public oriented measures
? Information about risks, increase awareness ? Change of habits ? Warnings (e.g. swimming ban) 3) Public oriented • Inform water profiles, newspaper, signs...
General Information General Information
http://www.wageningenur.nl/nl/Dossiers/dossier/Blauwalg.htm
Booklet for water managers, politicians, students, etc. General Information 3) Effect oriented measures • Inhibition of cyanobacterial growth Physical: Aeration, water movement, US Chemical: Algicides Biological: Barley straw, Dreissena, EM • Decimation of cyanobacterial blooms Physical: US, dynamite, skimmer, jets + air Chemical: Algicides Biological: Viruses • Inhibition scum inflow Jets, bubble screen, dam, floating screen Bubble screen
Artificial mixing in Lake Nieuwe Meer
From Huisman et al. 2004 Ecology 85: 2960-2970 Artificial mixing experiment in the deep Lake Nieuwe Meer 2003
Mixing prevents bloom of Microcystis Artificial mixing in shallow waters? →Removing/preventing scums? →Reducing foul odours? Enclosure experiment shallow water
Cyanobacteria Controls Aeration 250 250 ) Rest Algae ) -1 Total in pond -1 200 200 (µg l (µg l a a 150 150
100 100
50 50 Chlorophyll- Chlorophyll-
0 0 012345678910 012345678910 Week Week Mixing in shallow waters stimulates cyanobacteria Ultrasound Heavily promoted in the Netherlands Several large applications in 2007
Claims: Clear water within few days Resonance gas vesicles: kills only cyano’s Harmless to all other aquatic life A) 12 kHz B) 20 kHz (in only one)
C) 28 kHz D) 44 kHz
Agilent 54622D Mixed Signal Oscilloscope
Testing in 800 ml 4 controls 4 Ultrasound Anabaena sp. PCC7122 Control Ultrasound 0.30 0.30 A) Aan Controle B) Uit Controle (19-32 d) Ultrageluid Ultrageluid uit (19 -32 d) P < 0.001 Marginal growth inhibition 0.25 0.25 ) ) -1 -1 , d 0.20 P = 0.002 0.20 d , µ P = 0.004 µ
0.15 P = 0.762 P = 0.483 0.15 NoP = 0.009 effect on Φps2 0.10 0.10 Groeisnelheid ( Groeisnelheid( 0.05 0.05
0.00 0.00 Chlorofyl Deeltjes Biovolume Chlorofyl DeeltjesFilament Biovolume fragmentation
0.6
Control P = 0.735 0.5 Ultrasound
) Continuous exposure:
-1 0.4 P = 0.696
0.3 P = 0.340 No effect on C. raciborskii, 0.2 Growth rate (d rate Growth
0.1 M. aeruginosa (unicells) and
0.0 Scenedesmus obliquus C. raciborskii M. aeruginosa S. obliquus Test organisms Effect of ultrasound on Daphnia
Ultrasound
100
120 80 100 0 kHz 80
20 kHz 60
28 kHz 40
60 36 kHz 20
44 kHz 0
Gemiddelde overlevingstijd (min) 20 28 36 44 40 Ultrageluid frequentie (kHz) Survivors (%) Survivors 20
0
0 20 40 60 80 100 120 140 160 Controls Time (min) 1 8 0 0 A ) C o n tro le 1 6 0 0
1 4 0 0 ) Totaal fytoplankton -1 1 2 0 0 Cyanobacteriën g l µ ( 1 0 0 0 a a
8 0 0
6 0 0 Chlorofyl- 4 0 0
2 0 0
0 B ) 0Ultrageluid 0.16 1 4 6 8 11 14 15 18 19 21 25 1 6 0 0 T ijd (d ) 1 4 0 0 ) Totaal fytoplankton -1 1 2 0 0 Cyanobacteriën g l g µ ( 1 0 0 0 a a 8 0 0 Ultrasound 6 0 0 Chlorofyl- 4 0 0
2 0 0
0 C )0 D 0.16 a p h n 1 ia 4 6 8 11 14 15 18 19 21 25 Does not kill cyano’s T ijd (d ) 1 5 0 0 C o n tro le
) Ultrageluid
-1 Does not clear water l # ( 1 0 0 0 Acute lethal to Daphnia Daphnia Daphnia 5 0 0 No gasvesicle ruptures
0 0 0.16 1 4 6 8 11 14 15 18 19 21 25 T ijd (d ) Ultrasound made water green
21 days
Ultrasound
Control Ultrasound Control Field trials: 1) Zwaanshoek
No clearing water
Govaert et al., 2007 Univ. Leuven/Kortrijk, Belgium
Reference basin Ultrasound basin Field trials: 2) Tholen & 3) Gouden Ham
Tholen 23-10-2007 Kardinaal et al., 2008: Transducers were not able preventing bloom and surface scums Gouden Ham
‘t Groene Eiland 140x103 140 3000
120x103 120 2500
2000 100x103 100 1500 kHz
80x103 80 1000
500 60x103 60 Microcystis 0 kHz cell MHz
40x103 40 1 10 100 Radius gas bubble (µm) 20x103 20 2.2 - 1.3 0.020 - 0.005 0 0 Gas vesicles Microcystis cell Anabaena Daphnia filament
0.01 0.1 1 10 100 1000 10000 Radius gas bubble (µm)
No theoretical support for claim χ χ gas vesicle resonance 1 3 2 2 2 + 6 0 = 2 0 + + − 3 2 0 0 0 0 Branson Digital Sonifier 450 M. aeruginosa killed at 4 W/mL in 4 cycles of 30 sec
• In our studies no effect of 0.00085 W/mL
• MHz frequencies only travel 10 to 20 cm in water
• Low frequency ultrasound will not rupture gasvesicles or damage cyanobacteria
Ultrasound in Laguna de Sauce is a waste of money Please, be critical on the fancy brochures of the commercial suppliers Examples taken from the internet
https://conference.ifas.ufl.edu/aw13/Presentations/2- Wednesday/Grand%20Floridian/Session%208b/0300%20Whatley.pdf Another example
https://conference.ifas.ufl.edu/aw13/Presentations/2- Wednesday/Grand%20Floridian/Session%208b/0300%20Whatley.pdf
Ultrasound Laboratory assays: Does not kill cyano’s & does not clear water Acute lethal to Daphnia ThereNo gasvesicle is ruptures no music in Fieldfighting trials: cyanobacteria Stopped in Tholen and Gouden Ham (Kardinaal et al., 2007) Stopped in Rijnland Area (Govaert et ali., 2007; Stroom, pers. comm.) withAnd more ineffectiveness:commercial NUON: LG Sonic XXL doesn’t work ultrasoundProf. Muylaert: No effect systems! on cyano’s in lab (pers. comm) (univ. Kortrijk/Leuven) Golden algae as biological control of cyanobacteria? • (Poterio)Ochromonas eats WorldMicrocystis widecells and very blooms: small colonies ShinyBUT: golden algae • Golden algae omnipresent, still world wide cyanobacteria • Golden algae eat only small particles do not control Microcystis • Golden algae might produces foul odors and toxins (Chlorosulfolipids) Ochromonas cyanobacteria!• Golden algae might cause fish kills
From Van donk et al 2009 1000-faces of “Effective Micro-organisms” They come in many formulations, but are they as ‘effective’ as claimed?
EM-A EM-mudballs ACF32 Poco CBX suspension EM-mudballs/Bokashi balls heavily promoted in Almere EM-mudballs Dosis-response: 0, 0.01, 0.1, 0.25, 0.5, 1.0, 5.0 and 10 g l-1 Advised dose
0.5 A A AB A 0.4
) BC C -1 C 0.3
0.2 Growth rate (d rate Growth
0.1 D
0.0 0 0.01 0.1 0.25 0.5 1 5 10 EM-mudball concentration (g l-1) EM-mudballs:
In 3 Erlenmeyer experiments, in beakers (250 ml) and aquaria (1.2 l) no support for claimed mechanism EM-mudball Aquarium experiment 42.5 g in 25 l water EM-mudball
Start Day 1 Day 5 Day 15
Controls )
-1 180
g l g EM-ball
µ 160 Control (
a 140
120
100
80
60
40
20
0 Cyanobacteria chlorophyll- Cyanobacteria 0 3 6 9 12 15 27 30 Time (d) After 1 month
With EM- mudball
Controls with EM-mudball “Effective Micro-organisms”: Many formulations are NOT ‘effective’! Effective Micro- organisms do not control EM-A EM-mudballs ACF32 Poco CBX suspension “CBXcyanobacteria! contains ‘rare’ cyanobacteria that will purify the water and thereby eliminate blue-greens” (De Roo, pers. comm.) “Poco has cured 25 people from cancer” (Wisman 30-01-08) ARCADIS-UvA method: H2O2
-1 Low doses of H2O2 (< 2.5 mg l ) Kills only cyanobacteria (?) Rapid removal from system
M. Drábková, H.C.P. Matthijs, W. Admiraal & B. Maršálek
Selective effects of H2O2 on cyanobacterial photosynthesis PHOTOSYNTHETICA 45 (3): 363-369, 2007 -3 Toxicity as EC 5 0 values (g m ) fo r H 2 O 2 (concentration which causes 50 % inhibition of the photosynthetic yield, Fv/Fm) ) -1
3 0
Cyanobacteria Green algae 2 5 D ia to m
2 0
1 5 Cyanobacteria are more sensitive concentration, mg mg l concentration,
2 than eukaryotic algae O 2 1 0 (greens and diatoms)
5
values (H values 0
50 i a e is ti s il d itata r ino a ap EC lathrata ariabil c inh . grac v erug . c C re a S. nidulans A T. C. N. seminulum M. P. sub S. quadricauda Modified from Phytoplankton species Drábková et al 2007 First application of ARCADIS-UvA method Koetshuisplas, Veendam Netherlands July 17th 2009
© Pictures made by Bart Reeze, ARCADIS -1 H2O2 (2 mg l )
Data were kindly provided by ARCADIS-UvA, Dr Matthijs 8e+5 20
) 18 -1 7e+5 cyanobacteria toxins (MC) 16
6e+5 )
14 -1 g l g
(cells ml (cells 5e+5
12 µ
4e+5 10
8 3e+5 6 2e+5 4 Microcystins ( Microcystins 1e+5 2
0 Planktothrix agardhii Planktothrix 0
1 3 7 14 28 35 Days -1 2 mg H2O2 l kills >80% of cyanobacteria in 3 hrs No effect on eukaryotic phytoplankton
-1 H2O2 disappears rapidly to < 1 mg l in few hours Cyanobacteria (Planktothrix agardhii) reduced to very low levels Microcystins were release but decreased in time
Safe bathing water in Koetshuisplas for long period regular repeating needed M. aeruginosa Strain LEA 13
100 Colony Unicell 80
60
40
20 Lab colony is more resistant
Photosystem efficiency (% of control) of (% efficiency Photosystem 0 than unicell (same strain)
0 2 4 6 8 -1 H2O2 (mg.L ) Field samples tested 1) Beek & Donk 2) Boxtel A) Microcystis dominance 5) Eindhoven B) Other cyanobacteria dominance 6) Grave 10) Someren 100 100 11) Berglandweg 12) Kaukasusweg 15) Roosendaal 80 16) Bergen-op-Zoom 80 3) Budel 4) Deurne 7) Middelrode 8) St-Michielsgestel 60 60 9) St Oedenrode 13) Reggevijver 14) Essche Stroomvijver 17) Valkenswaard 40 40
20 20 PSII efficiency (% of control) efficiency PSII PSII efficiency (% control) of efficiency PSII 0 0
0 2 4 6 8 10 12 0 2 4 6 8 10 12 -1 -1 H2O2 concentration (mg L ) H2O2 concentration (mg L )
Aphanizomenon flos-aquae 10 Anabaena planktonica Microcystis aeruginosa Microcystis flos-aquae ) -1 8 Variability in the field L 2 O
2 Microcystis in situ can be less sensitive 6 Floating biomass
4 EC50 (mg H EC50 2
0 0 200 400 600 800 1000 1200 1400 1600 Cyanobacteria chlorophyll-a concentration (µg L-1) Hydrogen peroxide exposure → release of microcystins ARCADIS-UvA claim fighting cyanobacteria with low dose H2O2 is efficient, but there are doubts on generality and toxins release Plant-tree and extracts - many claims:
it will become the most promising method to control algal bloom“ (Hu and Hong 2008)
“barley straw can be an effective control method” (Purcell et al. 2013)
“effective and environmentally-sound option for the control of cyanobacterial and microalgal blooms” (Iredale et al. 2012)
“very useful for controlling of M. aeruginosa based blooms” (Shao et al. 2013)
• • • ) )
-1 1400 Fructus mume Salvia miltiorrhiza 1400 -1 A) Fructus mume B) Salvia miltiorrhiza A) B) 0.5 0.5 g L g 0 mg L-1 0 mg L-1 g L µ µ 1200 1200 30 mg L-1 40 mg L-1 0.4 0.4 60 mg L-1 80 mg L-1 1000 120 mg L-1 160 mg L-1 1000 240 mg L-1 320 mg L-1 -1 0.3 0.3 800 480 mg L 640 mg L-1 800
600 600 0.2 0.2 concentration ( concentration concentration ( concentration -1 a a 400 400 -1 0 mg L 0 mg L -1 0.1 -1 40 mg L 0.1 30 mg L -1 -1 80 mg L 200 200 60 mg L -1 -1 160 mg L Photosystem II efficiency PhotosystemII efficiency 120 mg L -1 0.0 240 mg L-1 320 mg L 0.0 0 0 -1 480 mg L-1 640 mg L Chlorophyll- Chlorophyll- ) ) -1 -1 -4 -1 0 3 6 -4 -1 0 3 6 C)-4 D-Lysine -1 0 3 6 D)-4 L- Lysine -1 0 3 6 1400 C) D-Lysine D) L- Lysine 1400 0.5 0.5
g g L Time (d)-1 Time (d)-1 g L Time (d) Time (d) µ 1200 0 mg L 0 mg L 1200 µ -1 -1 0.5 mg L 0.5 mg L 0.4 0.4 1.4 mg L-1 1.4 mg L-1 1000 -1 -1 1000 4.3 mg L 4.3 mg L -1 -1 13.0 mg L 13.0 mg L 0.3 0.3 800 38.9 mg L-1 38.9 mg L-1 800
600 600 0.2 0.2 concentration ( concentration ( concentration -1 -1 a 400 400 a 0 mg L 0 mg L 0.1 0.5 mg L-1 0.5 mg L-1 0.1 1.4 mg L-1 1.4 mg L-1 200 200 4.3 mg L-1 4.3 mg L-1 Photosystem IIefficiency 0.0 13.0 mg L-1 13.0 mg L-1 0.0 PhotosystemII efficiency 0 0 38.9 mg L-1 38.9 mg L-1 Chlorophyll- Chlorophyll-
) -4 -1 0 3 6 -4 -1 0 3 6 -1 Moringa oleifera 1400 E)-4 Moringa -1 0oleifera 3 6 -4 -1 0 3 6 0.5 E)
g g L Time (d)-1 Time (d) Time (d) Time (d) µ 1200 0 mg L -1 4 mg L 0.4 8 mg L-1 1000 -1 16 mg L -1 32 mg L 0.3 800 64 mg L-1 Effect of plant 600 0.2
concentration ( concentration -1 a 400 0 mg L /lysine is 0.1 4 mg L-1 8 mg L-1 200 -1 16 mg L Photosystem IIefficiency -1 short-lived 0.0 32 mg L 0 64 mg L-1 Chlorophyll-
-4 -1 0 3 6 -4 -1 0 3 6 Time (d) Time (d) Parkvijver Roosendaal 2000 http://www.helpdeskwater.nl/onderwerpen/water-ruimte/ecologie_maatregelen/meren/ingreep-biologie/rottend_stro/ @20092/maatregelen_meren_op/ Field experiment Barley NO success
600 4x105 ) Barley straw Renewal -1 Chlorophyll-a application Barley straw g L g
Cyanobacteria ) 500 µ Chlorophytes -1 Diatoms 3x105 Rest 400
300 2x105 concentration ( concentration
a a 200
105
100 Phytoplankton (cells (cells mL Phytoplankton
Chlorophyll- 0 0 9 9 9 9 0 0 0 0 9 9 9 00 0 0 00 00 00 No effect99 in other0 pond study0 too0 0 00 00 /19 /19 /19 1 /2 /20 /20 /2 /2 /2 2 2 7 8 9 2/ 3 5 6 7 8 9 0/ 1/ 1/ 1/ 1/ 1 1/1/20001/2/20001/ 1/4/20001/ 1/ 1/ 1/ 1/ 1 1 1/10/19991/11/19991/ 1/ 1/ Date
)
-1 Control -1
g l g 1000 Barley straw extract (25 ml l ) Nutrients in Barley straw µ extract promote algae
100 concentration ( concentration a 10 Chlorophyll- 1 0 2 4 7 10 14 17 21 24 28 Time (d) accepted Flocking and sinking cyanobacteria out the water column Turbid Turbid a) b)
Clear Clear Nutrient loading Nutrient loading Only ballast is not effective in sinking cyanobacteria 1600 )
-1 Red Soil 1400 Bauxite g L g Gravel µ Al modified Zeolite 1200 La modified Bentonite
1000
800
concentration ( concentration 600 a
400 in top of water column of water top in
200
Chlorophyll- 0 0 100 200 300 400 500 Ballast (mg L-1) Effective sinking cyanobacteria with low dose flocculent 1000 )
-1 Bauxite Al modified zeolite
g L g La modified bentonite
µ 800 Gravel Red soil
600
400
200 in top column ofwater top in 0 concentration ( concentration a Chlorophyll-
0 100 200 300 400 Ballast (mg L-1) in presence of PAC (2 mg Al L-1) 50 ) 10 40 60
-1 600 20 70 L
a 30 80 90 0 (no removal) 500 10 % 20 % 40 50 30 % 20 60 40 % 70 50 %
g chlorophyll- g 400 30 60 % µ 80 70 % 80 % 90 90 % 300 100 %
50 40 60 70 200
80 90
100
Cyanobacterial biomass ( biomass Cyanobacterial 50 60 70 80 90 25 50 100 200 400 Red soil (mg L-1) in combination with PAC (2 mg Al L-1) 3000 Top 0.5 8.0 3000 0.5 8.0
2500 2500 0.4 0.4 7.5 7.5 2000 2000
0.3 0.3 ) )
-1 1500 7.0 -1 1500 7.0 pH pH g L 0.2 g L 0.2 µ 1000 1000
6.5 6.5 Top Chlorophyll-a 0.1 Top Chlorophyll-a 0.1 500 Top PSII-efficiency 500 Top PSII-efficiency pH pH
0 0.0 6.0 0 0.0 6.0 control 0 20 40 80 160 240 320 control 0 40 80 160 240 320 concentration ( concentration (µ a a 500 X Data 500 X Data PSII efficiency (-) PSII efficiency (-) 0.1 0.1 Bottom Chlorophyll-a Bottom Chlorophyll-a 1000 Bottom PSII-efficiency 1000 Bottom PSII-efficiency
0.2 0.2 1500 1500 Chlorophyll- Chlorophyll-
2000 2000 0.3 0.3
2500 2500 0.4 0.4 3000 3000 Bottom 3500 0.5 3500 0.5
control 0 20 40 80 160 240 320 control 0 40 80 160 240 320 Red soil concentration (mg L-1) Red soil concentration (mg L-1) + PAC (2 mg Al L-1) + Chitosan (2 mg L-1) pH = 9 pH = 7 EC = 10000 μS cm-1 EC = 100 μS cm-1
2000 3500 Top 0.5 8 Jacarepaguá 10
3000 0.6 0.4 1500 9 7 2500 Top Chlorophyll-a Top PSII-efficiency 0.3 pH 2000 0.4
) 8 ) 1000 -1 pH -1
6 pH 1500 g L g L Top Chlorophyll-a
0.2 µ µ Top PSII-efficiency 7 1000 pH 0.2 500 5 0.1 500 6
0 0.0 4 0 0.0 Control 0 1 2 4 8 16 32 control 0 1 2 4 8 16 32 concentration ( concentration ( a a X Data 500 X Data PSII efficiency (-) PSII efficiency (-) 0.1 500 0.2 1000
0.2
1500 Chlorophyll- Chlorophyll- 1000 0.4 2000 0.3 Bottom Chlorophyll-a Bottom PSII-efficiency
2500 1500 0.4 0.6 3000 Bottom Chlorophyll-a Bottom PSII-efficiency 3500 Bottom 0.5 2000
control 0 1 2 4 8 16 32 Control 0 1 2 4 8 16 32 -1 Chitosan concentration (mg -1L) Chitosan concentration (mg L) -1 + Red soil (320 mg L-1) + Red soil (320 mg L) 700 0.6 600 Jacarépagua - top 2 mg L -1 Chitosan + 320 mg L -1 Red Soil 0.5 Vandamme et al 2013 Trends in Biotechonology 31(4): 500
0.4 Chlorophyll-a 400 PSII-efficiency
0.3 -1
) 300 Chitosan 2 mg L -1
g L g 0.2
µ 200
0.1 100
0 0.0 pH 5.4 6.8 7.3 7.8 5 6 7 8 9 10 concentration ( concentration PSII-efficiency
a X Data 200 0.1
0.2 400 Chlorophyll- 0.3 600 Chlorophyll-a PSII-efficiency 0.4
800 0.5 Jacarépagua - bottom 1000 5 6 7 8 9 10 0.6 pH Mitigation should always start with a system analysis
Scenarios: Doing nothing Curative measures = fighting the symptoms → Flock & Sink → Algaecides ☺ Preventive measures = tackling nutrient fluxes → External/internal ☺ Combined measures Email: [email protected] = speeding up recovery