Conservative Water Quality Lecture 7. Chemical Properties: dissolved oxygen Remember, along with...

Conservative Water Conservative Water QualityQuality

Lecture 7Lecture 7

Chemical Properties: Chemical Properties: dissolved oxygendissolved oxygen

Remember, along with temperature, dissolved Remember, along with temperature, dissolved oxygen (D.O.), is paramount in metabolic oxygen (D.O.), is paramount in metabolic regulationregulation

[D.O.] and temp. both determine the [D.O.] and temp. both determine the environmental niche aquatic organisms environmental niche aquatic organisms occupyoccupy

occupation of niches is controlled by a occupation of niches is controlled by a complex set of behavioral and physiological complex set of behavioral and physiological activities (acclimation) activities (acclimation)

acclimation is slow wrt D.O. (hours, weeks) acclimation is slow wrt D.O. (hours, weeks)

Chemical Variables: Chemical Variables: dissolved oxygendissolved oxygen

Although OAlthough O22 is rather abundant in the atm (21%), it is rather abundant in the atm (21%), it is only marginally soluble in water (6 ppm is not is only marginally soluble in water (6 ppm is not much)much)

What are the implications to fish/invertebrates?What are the implications to fish/invertebrates? Even metabolic rates of aqua-communities can Even metabolic rates of aqua-communities can

effect rapid changes in [D.O.]effect rapid changes in [D.O.] this effect increases with temp (interaction) this effect increases with temp (interaction) solubilitysolubility decreasesdecreases with with increasedincreased temp/saltemp/sal other factors: BP (direct), altitude (indirect), other factors: BP (direct), altitude (indirect),

impurities (indirect)impurities (indirect)

Oxygen Solubility CurveOxygen Solubility Curve

Chemical Variables: Chemical Variables: dissolved dissolved oxygenoxygen

factors affecting D.O. consumption:factors affecting D.O. consumption:water temperature (2-3x for every water temperature (2-3x for every

1010ooC)C)environmental (medium) D.O. environmental (medium) D.O.

concentration (determines lower limit)concentration (determines lower limit)fish size (Rc greater for small vs. large)fish size (Rc greater for small vs. large)level of activity (resting vs. forced)level of activity (resting vs. forced)post-feeding period, etc. (2x, 1-6 hrs post-feeding period, etc. (2x, 1-6 hrs

post feeding)post feeding)

Oxygen Consumption vs. Oxygen Consumption vs. SizeSize

for Channel Catfish (26for Channel Catfish (26ooC)C)

O2 cons. Rate Increase in

(mg/kg/hr) oxygen consumption

Fish size (g) Nonfed Fed from feeding (%)

2.5 880 1,230 40

100 400 620 55

500 320 440 38

1,000 250 400 60

From Lovell (1989)


What might be considered What might be considered minimal levels of minimal levels of maintenance of D.O.?maintenance of D.O.?

hard to determine due to hard to determine due to compounding effects (can’t compounding effects (can’t standardize conditions)standardize conditions)

major factor: exposure timemajor factor: exposure time for most species:for most species:

long-term: 1.5 mg/Llong-term: 1.5 mg/L medium term: 1.0 mg/Lmedium term: 1.0 mg/L short-term: 0.3 mg/L short-term: 0.3 mg/L


In general warm-water species are more In general warm-water species are more tolerant of low D.O. concentrationstolerant of low D.O. concentrations

Ictalurus punctatusIctalurus punctatus: adults/1.0 mg/L, : adults/1.0 mg/L, fingerlings 0.5 mg/Lfingerlings 0.5 mg/L

Procamberus clarkiiProcamberus clarkii: : adults/2.0 mg/L, adults/2.0 mg/L, juveniles/1.0 mg/L juveniles/1.0 mg/L

Litopenaeus vannameiLitopenaeus vannamei: adults/0.5-0.8 mg/L: adults/0.5-0.8 mg/L Litopenaeus stylirostrisLitopenaeus stylirostris: adults/1.2-1.4 mg/L: adults/1.2-1.4 mg/L


Many practical aquaculturists will Many practical aquaculturists will recommend that D.O. concentrations do not recommend that D.O. concentrations do not drop below 6.0 mg/Ldrop below 6.0 mg/L

this is an impractical guideline in that this this is an impractical guideline in that this level can seldom be achieved at nightlevel can seldom be achieved at night

a more practical guideline might be to a more practical guideline might be to maintain D.O. levels around 90% saturationmaintain D.O. levels around 90% saturation

no lower than 25% saturation for extended no lower than 25% saturation for extended periodsperiods

Chemical Variables: Chemical Variables: dissolved oxygen/behaviordissolved oxygen/behavior

if D.O. levels in the medium are adequate, if D.O. levels in the medium are adequate, fish meet increased demands due to fish meet increased demands due to locomotion or post-feeding by increased locomotion or post-feeding by increased rate of ventilation or large “gulps” of waterrate of ventilation or large “gulps” of water

declining D.O.: seek zones of higher D.O., declining D.O.: seek zones of higher D.O., reduce activity (reduced MR), stop reduce activity (reduced MR), stop consumption of feedconsumption of feed

compensatory pointcompensatory point: when D.O. demand : when D.O. demand cannot be met by behavioral or cannot be met by behavioral or physiological responsesphysiological responses

Chemical Variables: Chemical Variables: dissolved oxygen/behaviordissolved oxygen/behavior

upon reaching compensatory point: gaping upon reaching compensatory point: gaping at surface, removal of oxygen from surfaceat surface, removal of oxygen from surface

shown in both fish and invertebratesshown in both fish and invertebrates small aquatic animals are more efficientsmall aquatic animals are more efficient some oxygen provided by glycolysis or some oxygen provided by glycolysis or

anaerobic metabolism, but blood pH dropsanaerobic metabolism, but blood pH drops pH drop in blood reduces carrying capacity of pH drop in blood reduces carrying capacity of

hemoglobin (hemocyanin?)--> deathhemoglobin (hemocyanin?)--> death

Oxygen/Temperature Oxygen/Temperature InteractionInteraction

Oxygen consumption Oxygen consumption increases with temperature increases with temperature until a maximum is until a maximum is achievedachieved

peak consumption rate is peak consumption rate is maintained over a small maintained over a small temp rangetemp range

consumption rate decreases consumption rate decreases rapidly as temp increasesrapidly as temp increases

lethal temperature finally lethal temperature finally achievedachieved

Chemical Variables: Chemical Variables: dissolved oxygen/sourcesdissolved oxygen/sources major producer of D.O. in ponds is major producer of D.O. in ponds is

primary productivity (up to 80%), primary productivity (up to 80%), diffusion is low (<3%)diffusion is low (<3%)

incoming water can often be deficient incoming water can often be deficient depending upon source water conditionsdepending upon source water conditions

major consumers: primary productivity, major consumers: primary productivity, aquatic species (density dependent), CODaquatic species (density dependent), COD

diel fluctuation diel fluctuation indirect relationships (algae, secchi) indirect relationships (algae, secchi)

Oxygen BudgetOxygen BudgetI nput O2 (kg/ ha) % of total Photosynthesis 4,130 76.9 I nflowing water 94 1.7 Aeration 99 1.8 Diff usion 1,050 19.6 Total 5,373 100.0Output Overflow, drainage 32 0.6 Phyto respiration 3,090 57.5 Benthic respiration 1,040 19.4 Fish/ shrimp resp. 1,210 22.5

Total 5,372 100.0

Diel Oxygen FluctuationDiel Oxygen Fluctuation

Typical pattern = Typical pattern = oxygen max during oxygen max during late afternoonlate afternoon

difference in difference in surface vs. benthic surface vs. benthic for stratified pondsfor stratified ponds

dry season = faster dry season = faster heating at surface heating at surface and less variation and less variation

Influence of Sunlight on Influence of Sunlight on Photosynthesis/OPhotosynthesis/O22

ProductionProduction

Photorespiration: Photorespiration: predictablepredictable

Chemical Variables: Chemical Variables: total total alkalinityalkalinity

total alkalinitytotal alkalinity: the total amount of : the total amount of titratable bases in water expressed as mg/L titratable bases in water expressed as mg/L of equivalent CaCOof equivalent CaCO33

“ “alkalinity” is primarily composed of the alkalinity” is primarily composed of the following ions: COfollowing ions: CO33

--, HCO, HCO33--, hydroxides, , hydroxides,

ammonium, borates, silicates, phosphatesammonium, borates, silicates, phosphates alkalinity in ponds is determined by both the alkalinity in ponds is determined by both the

quality of the water and bottom mudsquality of the water and bottom muds calcium is often added to water to increase calcium is often added to water to increase

its alkalinity, buffer against pH changesits alkalinity, buffer against pH changes


thus, a total alkalinity determination of 200 thus, a total alkalinity determination of 200 mg/L would indicate good buffering capacity mg/L would indicate good buffering capacity of a water sourceof a water source

natural freshwater alkalinity varies between natural freshwater alkalinity varies between 5 mg/L (soft water) to over 500 mg/L (hard 5 mg/L (soft water) to over 500 mg/L (hard water)water)

natural seawater is around 115-120 mg/Lnatural seawater is around 115-120 mg/L seldom see pH problems in natural seawaterseldom see pH problems in natural seawater water having alkalinity reading of less than water having alkalinity reading of less than

30 mg/L are problematic30 mg/L are problematic


total alkalinity level can be associated with total alkalinity level can be associated with several potential problems in aquaculture:several potential problems in aquaculture:

< 50 mg/L: copper compounds are more < 50 mg/L: copper compounds are more toxic, avoid their use as algicidestoxic, avoid their use as algicides

natural waters with less than 40 mg/L natural waters with less than 40 mg/L alkalinity as CaCO3 have limited alkalinity as CaCO3 have limited biofiltration capacity, pH independentbiofiltration capacity, pH independent

low alkalinity = low COlow alkalinity = low CO22 --> low nat prod --> low nat prod low alkalinity = high pHlow alkalinity = high pH

Chemical Variables: Chemical Variables: total total hardnesshardness

total hardnesstotal hardness: total concentration of : total concentration of metal ions expressed in terms of mg/L of metal ions expressed in terms of mg/L of equivalent CaCOequiva- lent CaCO33

primary ions are Caprimary ions are Ca2+2+ and Mg and Mg2+2+, also iron and , also iron and manganesemanganese

total hardness approximates total alkalinitytotal hardness approximates total alkalinity calcium is used for bone and exoskeleton calcium is used for bone and exoskeleton

formation and absorbed across gillsformation and absorbed across gills soft water = molt problems, bone soft water = molt problems, bone

deformitiesdeformities

Chemical Variables: Chemical Variables: pHpH

pH: the level or intensity of a substance’s pH: the level or intensity of a substance’s acidic or basic characteracidic or basic character

pHpH: the negative logarithm of the : the negative logarithm of the hydrogen ion concentration (activity) of a hydrogen ion concentration (activity) of a substancesubstance

pH = -log(1/[HpH = -log(1/[H++])]) ionization of water is low (1x10ionization of water is low (1x10-7-7 moles of moles of

HH++/L and 1x10/L and 1x10-7-7 moles OH moles OH--/L)/L) neutral pH = similar levels of Hneutral pH = similar levels of H++ and OH and OH--

Chemical Variables: Chemical Variables: pHpH at acidic pH levels, the quantity of H+ at acidic pH levels, the quantity of H+

predominatespredominates acidic pH = pH < 7, basic = pH >7acidic pH = pH < 7, basic = pH >7 most natural waters: pH of 5-10, usually most natural waters: pH of 5-10, usually

6.5-9; however, there are exceptions6.5-9; however, there are exceptions acid rain, pollutionacid rain, pollution can change due to atm COcan change due to atm CO2,2, fish respiration fish respiration pH of ocean water is stable (carbonate pH of ocean water is stable (carbonate

buffering system, later)buffering system, later)

Chemical Variables: Chemical Variables: pHpH

Other sources of change:Other sources of change:decay of organic matterdecay of organic matteroxidation of compounds in bottom oxidation of compounds in bottom

sedimentssedimentsdepletion of COdepletion of CO22 by phytoplankton on diel by phytoplankton on diel

basisbasisoxidation of sulfide containing minerals in oxidation of sulfide containing minerals in

bottom soils (e.g., oxidation of iron pyrite bottom soils (e.g., oxidation of iron pyrite by sulfide oxidizing bacteria under by sulfide oxidizing bacteria under anaerobic conditions)anaerobic conditions)

Chemical Variables: Chemical Variables: carbon dioxidecarbon dioxide

normal component of all natural watersnormal component of all natural waters sourcessources: atmospheric diffusion, respiration : atmospheric diffusion, respiration

of cultured species, biological oxidation of of cultured species, biological oxidation of organic compoundsorganic compounds

usually transported in the blood as HCOusually transported in the blood as HCO33--

converted to COconverted to CO22 at the gill interface, at the gill interface, diffusion into mediumdiffusion into medium

as the level of COas the level of CO22 in the medium increases, in the medium increases, the gradient allowing diffusion is lessthe gradient allowing diffusion is less


this causes blood COthis causes blood CO22 levels to increase, levels to increase, lowering blood pHlowering blood pH

with lower blood pH, carrying capacity of with lower blood pH, carrying capacity of hemoglobin decreases, also binding hemoglobin decreases, also binding affinity for oxygen to hemoglobinaffinity for oxygen to hemoglobin

this phenomenon is known as the this phenomenon is known as the Bohr-Bohr-Root effectRoot effect

COCO22 also interferes with oxygen uptake also interferes with oxygen uptake by eggs and larvae by eggs and larvae

COCO22 Level Affects Level Affects Hemoglobin SaturationHemoglobin Saturation


in the marine environment, excesses of COin the marine environment, excesses of CO2 2 are are mitigated by the mitigated by the carbonate buffering systemcarbonate buffering system

COCO22 reacts with water to produce H reacts with water to produce H22COCO33, carbonic , carbonic acidacid

HH22COCO3 3 reacts with CaCOreacts with CaCO3 3 to form HCOto form HCO33--

(bicarbonate) and CO(bicarbonate) and CO332-2- (carbonate) (carbonate)

as COas CO22 is used for photosynthesis, the reaction is used for photosynthesis, the reaction shifts to the left, converting bicarbonates back to shifts to the left, converting bicarbonates back to COCO22

what large-scale implications does this have?what large-scale implications does this have?

The Effect of pH on The Effect of pH on Carbonate BufferingCarbonate Buffering


Concentrations of COConcentrations of CO22 are small, even though are small, even though it is highly soluble in it is highly soluble in waterwater

inverse relationship inverse relationship between [CObetween [CO22] and ] and temperature/salinitytemperature/salinity

thus, COthus, CO22 solubility solubility depends upon many depends upon many factorsfactors

Chemical Variable: Chemical Variable: carbon carbon dioxidedioxide

COCO22 is not particularly toxic to fish or is not particularly toxic to fish or invertebrates, given sufficient D.O. is invertebrates, given sufficient D.O. is availableavailable

maximum tolerance level appears to be maximum tolerance level appears to be around 50 mg/L for most speciesaround 50 mg/L for most species

good working level of around 15-20 mg/Lgood working level of around 15-20 mg/L diel fluctuation opposite to that of D.O.diel fluctuation opposite to that of D.O. higher levels in warmer months of yearhigher levels in warmer months of year

Part II: Nitrogenous Part II: Nitrogenous Compounds in WaterCompounds in Water

Evolution of the Nitrogen CycleEvolution of the Nitrogen Cycle

Unlike carbon or oxygen, nitrogen is not very available to life

it’s conversion requires biological activity

nitrogen cycle is required by life, but also driven by it

cycle is rather complex and has evolved as the atmosphere became oxygenated

as we know, Earth’s original atm was oxygen-poor


Earliest forms of nitrogen-reducing bacteria had to have been anaerobic

other option: NH4+ already existed in

some formtoday these ancient N-fixers either

only exist in anaerobic environments or the N-fixing apparati are carefully guarded from intracellular oxygen


As Earth’s atmosphere became more O2-rich, more NO3 became available

this created niches occupied by organisms that could reduce NO3 to NH3 (many higher plants can do this)

converting NO3 back to N2 (denitrification) is an arduous process and has evolved more recently

Gaseous NitrogenGaseous Nitrogen Nitrogen is the major gas in the

atmosphere after oxygen, second limiting factor constitutes 78.1% of total gases in air solubility in water is largely dependent

upon two physio-chemical factors: temperature and salinity

at saturation/equillibrium it has higher values than oxygen or CO2

Nitrogen Saturation ValuesNitrogen Saturation Values

Generalized Nitrogen CycleGeneralized Nitrogen Cycle Nitrogen dynamics in the

environment involves some fairly complex cycling

N is relatively unreactive as an element

cyclic conversions from one form to another are mainly mediated by bacteria

Cycle occurs in both aerobic and anaerobic environments

nitrogen cycle

Process 1: Process 1: fixationfixation Nitrogen fixation refers

to the conversion of N2 to either NO3 or NH4 by bacteria

terrestrial systems: soil bacteria in root nodules of legumes

aquatic systems: blue green algae

biological, meteorological, industrial transformations also occur

Nitrogen FixationNitrogen FixationType of Fixation N2 fixed (1012 g per year)

Non-biological

industrial About 50

combustion About 20

lightning About 10

Total About 80

Biological

Agricultural land About 90

Forest + nonag land About 50

Sea About 35

Total About 175

Process 2: Process 2: nitrificationnitrification The term nitrification

refers to the conversion of ammonium to nitrate (pathway 3-4 opposite)

Responsible: nitrifying bacteria known as chemoautotrophs

These bacteria gain their energy by oxidizing NH3,

while using CO2 as a source of carbon to synthesize organic compounds

The nitrogen cycle, once more!

Process 3: Process 3: denitrificationdenitrification

By this process, NO3 in soil or water is converted into atm N2, nitric oxide or nitrous oxide

this must occur under anaerobic conditions (anaerobic respiration)

presence of O2 can reverse the reaction

again, mediated by bacteria (Pseudomonas sp., Alkaligenes sp. and Bacillus sp.)

Denitrification = step 5, above

Aquatic Nitrogen CyclingAquatic Nitrogen Cycling For aquaculturists, cycling

transforms usually begin with the decomposition of organic matter from either plant or animal sources

major source in aquaculture: feeds

ultimately excreted as amine groups on amino acids or excreted in soluble form primarily as NH3/NH4

+, other compounds

amino acid

Release of NHRelease of NH33

NH3 separated from organic protein via microbial activity

Process referred to as deaminification or ammonification

NH3 is released to water column (mineralization) and assimilated into primary productivity (NH3 + H+ --> NH4

+) ammonification is

heterotrophic, under aerobic or anaerobic conditions

ammonification

Aquatic Nitrogen CyclingAquatic Nitrogen Cycling

NH3 and NH4+ are both either

assimilated by aquatic plants for growth or nitrified (oxidized) to NO3

- (nitrate)nitrate can also be used as a growth

substrate (Guillard’s F medium)two step process:

NH4+ + 1.5O2 NO2

- + 2H+ + H2O

NO2- + 0.5O2 NO3

-

Note: these are oxygen-driven reactions

Aquatic Nitrogen CyclingAquatic Nitrogen Cycling Conversion of ammonia (NH3) to nitrate

(NO3-) is via chemoautotrophic bacteria

first step by Nitrosomonas sp. second step by Nitrobacter sp. Both steps/reactions use NH4

+ and NO2- as

an energy source, CO2 as a carbon source this is a non-photosynthetic type of growth

Aquatic Nitrogen Aquatic Nitrogen CyclingCycling

Reaction runs best at pH 7-8 and 25-30oC however; under low DO, it runs in reverse NO3

- is converted to NO2= and other forms

can go all the way backwards to NH3

occurs in the hypolimnion under eutrophic (stagnant) conditions

REM: nitrogen also fixed by leguminous plants, free living bacteria, blue-green algae

magnitude of this transform not well studied

Nitrogen: Nitrogen: aqueous aqueous formsforms

Gaseous form of nitrogen (N2) is most prevalent followed by: nitrite, nitrate, ammonia or

ammonium nitrite is seldom a problem unless DO levels are

low (to be discussed later) ratio of NH3:NH4

+ rises with pH unfertilized ponds: TAN (NH3 +NH4

+) = 0.05-0.075 mg/L

fertilized ponds: TAN = 0.5 mg/L, 0.075 mg NO3-

Nitrogen AmendmentsNitrogen Amendments Nitrogen added as

fertilizer to ponds: urea Immediately upon

addition, it starts to decline

only small portion detectable from metabolic processes

plants typically take it up, die, mud deposit

inorganic nitrogen typically denitrified in the hypolimnion

high afternoon pH = increased volatization

urea

Nitrogen Equillibria: Nitrogen Equillibria: NHNH33/NH/NH44++

ammonia (NH3) is toxic to fish/inverts

pH affects proportion of NH3/NH4

+ as pH increases, NH3

increases calculation example

TAN = 1.5 mg/L, 26oC, pH = 8.6

answer: 0.35 mg NH3/L

Affect of pH/temp on NH3/NH4+

equillibria

More on AmmoniaMore on Ammonia As mentioned, initial source: feed, direct source:

excretion can calculate daily dosage/loading if you know:

NPUNPU and % protein in feed NPU is 0.4 (approx.) for most aquaculture feeds equ.: (1.0 - NPU)(pro/6.25)(1000) = g NH3/kg feed for 1.0 ha pond receiving 100 kg of 30% protein

feed/day, loading is 1,920 g NH3

dilution in 10 x 106 L is 0.192 mg NH3/L if NPU stays constant, NH3 production increases

with increased feeding

Ammonia ToxicityAmmonia Toxicity

Both NH3 and NH4+ are toxic to fish/inverts:

as medium NH3 increases, ability to excrete internal NH3 decreases (fighting gradient)

blood/tissue NH3 increases causes increase in blood pH

result: imbalance in enzyme activity, reduced membrane stability

increased O2 consumption by tissues, gill damage, reduced O2 transport (Root/Bohr, but other direction)

reduced growth, histological changes in gills/other organs


Short term exposure toxic at 0.7-2.4 mg/L 96 hr LC50 varies from 0.5-3.8 mg/L for

most fish toxicity tolerance varies due to biological

variability of different strains of species eggs are most tolerant (fish) larvae least tolerant, older = more

tolerant same probably holds true for inverts


Species 96- hour LC50 (mg/L NH3) Pink salmon 0.08- 0.1 Brown trout 0.50- 0.70 Rainbow trout 0.16- 1.10 Largemouth bass 0.9- 1.4 Common carp 2.2 Channel catfish 0.50- 3.8 Shrimp 5.71

Ammonia Toxicity in Ammonia Toxicity in PondsPonds

NH3 is more toxic when DO levels are low

however, toxic effect is probably nullified by resultant increase in CO2

thus, increased CO2 = decreased NH3

increased CO2 = decreased pH in some cases, fish have been shown

to acclimate to increases in NH3

Nitrite (NONitrite (NO22--) Toxicity) Toxicity

Nitrite reacts with hemoglobin to form methemoglobin

in process, iron converted from ferrous (Fe2+) to ferric (Fe3+) form

ferric form of iron cannot bind with oxygen blood changes from red to brown, appears

anemic those fish having methemoglobin reductase

enzyme can convert iron moeity back to ferrous

maybe same for crustaceans?


Recovery from nitrite toxicity usually occurs when fish are transferred to better water

complete recovery can occur in 24 h how does it get into system in first place? Nitrite is quickly transported across gill

membrane by lamellar chloride cells cells can’t distinguish between NO2

- and Cl- thus: nitrite absorption regulated by

nitrite:chloride ratio in medium


Nitrite is about 55 times more toxic in freshwater vs. 16 ppt seawater

Question: Can you add NaCl to water to reverse nitrite toxicity?

24 hr LC50 values vary tremendously in fish

safe bet: authors say 4.5 mg/L


Species 48- or 96- hr LC50 (mg/L NO2- N)

Rainbow trout 0.19- 0.39

Chinook salmon 0.88

Common carp 2.6

Channel catfish 7.1- 13

Largemouth bass 140

Guadeloupe bass 160

Shrimp, freshwater 8.5- 15.4

Shrimp, saltwater 45- 204 mg/L

Nitrate (NONitrate (NO33--) Toxicity) Toxicity

Nitrate builds up in ponds, like nitrite, when ponds are cooler

Nitrobacter does not function well under cool or cold water conditions

however, nitrates are least toxic form of soluble nitrogen

effects are similar to nitrite toxicity, but values of levels are much higher

Nitrate ToxicityNitrate Toxicity

Species 96- hr LC50 (mg/L NO3- N)

Guppy 180- 200

Guadeloupe bass 1,260

Chinook salmon 1,310

Rainbow trout 1,360

Channel catfish 1,400

Bluegill 420- 2,000

Shrimp Who knows???

Conservative Water Quality Lecture 7. Chemical Properties: dissolved oxygen Remember, along with...

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