• Life on earth probably evolved in Life on earth probably evolved in water water

• Most animals are 50-65% waterMost animals are 50-65% water

• water exists in all three physical water exists in all three physical states of matter: solid, liquid, and states of matter: solid, liquid, and gas gas

• 71% of the Earth Surface - Sea Water71% of the Earth Surface - Sea Water

• regulates the climate, dilute wasteregulates the climate, dilute waste

• major habitat for living creaturesmajor habitat for living creatures

Drm Abymv‡i cvwb †K wbgœwjwLZ fv‡e ‡kªYxweb¨vm Kiv nq-1| mnRvZ cvwb (connate water)2| DrmvwiZ cvwb (juvenile or magmatic water)3| mvgyw`ªK cvwb (oceanic water)

4| Nbxf~Z cvwb (condensed water)5| f~Mf©¯’ cvwb (infiltrated water)

6| b`x I n«‡`i cvwb (Rivers Lakes)7| eid (Ice caps and glaciers) 8| †gN (Atmosphere) cvwbi aiY (Kinds of Water) t

c„w_ex‡Z mKj cvwb GK ai‡Yi bq| wefbœ ¯’v‡bi cvwbi g‡a¨ ¸bv¸b I ˆewk‡ó¨i w`K w`‡q A‡bK cv_©K¨ i‡q‡Q| ¯^v` Abymv‡i cvwb `yB ai‡Yi-

¯^v`y cvwb I jebv³ cvwb|

Ae¯’vb Abymv‡i cvwb Avevi `yB ai‡bi-f~c„ô¯’ cvwbf~Mf©¯’ cvwb|

3

• 1. has cohesive behavior 1. has cohesive behavior

• 2. resists changes in temperature 2. resists changes in temperature

• 3. has a high heat of vaporization 3. has a high heat of vaporization and cools surfaces as it evaporates and cools surfaces as it evaporates

• 4. expands when it freezes 4. expands when it freezes

• 5. is a versatile solvent5. is a versatile solvent

Characteristics of HCharacteristics of H2200

Water (H2O) is a very unusual substance with many strange and unique properties that are so important to Life on Planet Water - Life which is based on Water and adapted to its unique and anomalous properties. How does this simple molecule, composed of two hydrogen atoms and one oxygen atom, behave the way it does and how does it support life?

Some familiar properties of water are:

It's colourless;

It's tasteless;

It's odourless;

It feels wet;

It dissolves nearly everything;

It exists in three forms: liquid, solid, gas, and is cycled though the water cycle;

It can absorb a large amount of heat;

It sticks together into beads or drops;

It flows and erodes the surface of the earth;

it moves sediments to form beaches, river banks and bars;

It shapes lipid and protein molecules and give them their 3-dimensional form which is critical to their function

It's part of every living organism on the planet.

Objectives

• What physical and chemical properties of water have a direct impact on fish/invert culture?

• Must know this to design systems to achieve appropriate criteria.

• What are optimal levels of these factors?

Chemical/Physical Properties of Water

Physical properties of water

Physical properties of water

Physical properties of water

04/21/23 Prepared by: Prof. Rodriguez 10

• 4. Oceans and lakes don't freeze 4. Oceans and lakes don't freeze

• because of hydrogen bonding, water because of hydrogen bonding, water is less dense as a solid than it is as a is less dense as a solid than it is as a liquid.liquid.

• consequently, ice floats.consequently, ice floats.

Physical properties of water

04/21/23 12

• 5. water is a versatile solvent owing 5. water is a versatile solvent owing it to the polarity of the water it to the polarity of the water molecule molecule

• ionic compounds dissolve in waterionic compounds dissolve in water

Physical Variables: temperature

• most influential biological factor

• can also be an economic factor (i.e., energy)

• impractical to maintain in outdoor cultures or very large-scale

• affects oxygen solubility and Q10 (i.e., metabolism), O2 consumption

• Environmental parameter having the greatest impact on aquaculture species.

• Impractical to control in large-scale aquatic situations.• Implies proper geographical location.• Temperature affects rates of physiological processes and levels

of other parameters.• Metabolism is the engine, temp controls rate of engine.

• Physiological processes affected: – Respiratory rate (metabolic rate)

• metabolic rate increases with temperature• fish consume oxygen 2-3x faster at 30C vs. 20C• Conclusion?

– Efficiency of feeding/assimilation– Growth– Behavior– Reproduction

• Each species has a characteristic growth curve with an optimum range.

• Also have upper and lower temperature limits (lower lethal limit, upper lethal limit).

• Outside tolerable temperature range, disease and stress become more prevalent.

corals 28-30

Chinook salmon 10-14

Tilapia28-30

Pacific white shrimp26-32

oC

•High specific heat: •Specific heat: number of calories necessary to raise 1 gram of water 1 degree Celsius

•Peculiar density-temperature relationship: pure water most dense when at 4 degrees Celsius.

Physical properties of water

Physical properties of water: cohesion

Physical properties of water: viscosity and buoyancy

Diffusion and osmosis

Physical conditions in the aquatic environment

– Light–Temperature–Oxygen–Salinity–Acidity

Physical conditions:

1. Light

• Some incident sunlight is reflected from the water’s surface

• The lower the angle of the sun, the greater the reflectance

The amount of light that penetrates the water’s surface varies with latitude, season

• Light that does penetrate is absorbed by water molecules…

Fig. 4.6

• Different wavelengths penetrate to different depths

• E.g. for visible light:– Red: most rapidly absorbed– Blue: least rapidly absorbed --> greatest

penetration

• Suspended particles in the water also absorb and scatter light --> reduces penetration even further

Physical conditions

2. Temperature

• Water is most dense at 4oC

• Lake in summer: – temperature drops with increasing depth– Stratification of water column

• Epilimnion: warm surface water• Thermocline: rapid decline in temperature• Hypolimnion: cold, dense water (~4oC)

Temperature

• Tropical lakes: thermocline all year

• Temperate lakes: only in summer– Autumn: surface cools --> temperature

becomes uniform throughout (~4oC)Mixing of all parts = fall turnover– Increased nutrient levels at the surface

Fig. 4.7

Temperature

• Temperate lakes in winter– surface colder than 4oC– Bottom near 4oC

• Temperate lakes in spring– Ice melts --> surface warms --> ~4oC

throughoutSpring turnover

Temperature

• Oceans: never undergo complete turnover

• Winter: thermocline rises

• Summer: thermocline descendsBottom never mixes with top

Temperature

• Flowing waters: temperature variable

• Shallow waters: follow air temperature– Track changes slowly

Physical Variables: Density

• Already mentioned as an aspect of fluids.• Pure water is most dense at 4oC.• Below this it becomes less dense and freezes at

0oC.• When you add impurities to water (e.g., salt), its

density increases.• Thus, seawater freezes at a lower temp (-1.4oC).• For all intents and purposes, a minor issue for

aquaculture.

• On average, concentration of dissolved salts, On average, concentration of dissolved salts, i.e., i.e., the salinity, in seawater is 3.5% or 35the salinity, in seawater is 3.5% or 35‰.‰.

• The relative abundances of the ions listed above The relative abundances of the ions listed above does not change, even though salinity does; are does not change, even though salinity does; are said to be conservative.said to be conservative.

• Relative abundances of minor and trace Relative abundances of minor and trace constituents do varyconstituents do vary

Determining SalinityDetermining Salinity• Evaporation of water to weight the salt is an Evaporation of water to weight the salt is an

imprecise methodimprecise method• Because of the constancy of composition if we Because of the constancy of composition if we

measure one component we can get a more measure one component we can get a more precise measurementprecise measurement

• Salinity ppt = 1.80655 x Chlorinity in pptSalinity ppt = 1.80655 x Chlorinity in ppt• If chlorinity is 19.2 ppt, what is the salinity of sea If chlorinity is 19.2 ppt, what is the salinity of sea

water?water?• 34.7 ppt = 35 ppt34.7 ppt = 35 ppt

Sources of SaltSources of Salt• Rivers (winds and glaciers are a less Rivers (winds and glaciers are a less

important, indirect source)important, indirect source)

• Weathering of oceanic crustWeathering of oceanic crust

• Hydrothermal Vents associated with Mid-Hydrothermal Vents associated with Mid-ocean ridges and other submarine ocean ridges and other submarine volcanoesvolcanoes

• Biologic activityBiologic activity

• Interaction with Particulate matter: clays Interaction with Particulate matter: clays and organic matter absorb dissolved and organic matter absorb dissolved metalsmetals

Direct PrecipitationDirect Precipitation• Hydrothermal Activity: (f. 7.4)Hydrothermal Activity: (f. 7.4)

• Reaction between seawater and new Reaction between seawater and new oceanic crustoceanic crust

• Minerals like magnesium is incorporated Minerals like magnesium is incorporated into depositsinto deposits

• Calcium is added to sea waterCalcium is added to sea water

Physical Variables: salinity (S)

• Often considered a chemical attribute of water.

• Salinity: the measure of the concentration of dissolved ions in water (ppt, mg/L).

• Practical Salinity Units (psu)

• Major ions: Na+ and Cl-

• Substantial ions: Mg2+, Ca2+, K2+, SO4=, and

bicarbonates HCO3-

• Salinity sum total of geological and hydrological conditions in region.

Major and Minor Ions

Physical Variables: Salinity

• Freshwater surface waters in arid regions have higher salinity, changes rapidly with rainfall.

• Marine seawater salinity: 35 ppt +/- 2 ppt.• Brackishwater: highly variable salinity due to

tidal and run-off effects.• Heavy rainfall in ocean often creates freshwater

lens effect.• Artificial sea salts are relatively expensive and

should only be used for small systems, those that have salinity flux, and biosecurity.

Physical Variables: salinity

How to measure salinity:

• chlorinity

• glass hydrometer

• conductivity meter

• refractometer

• mutiparameter water quality meter

• Other methods?

Salinity and Physiology

• Many aquaculture species have the ability to modify blood/hemolymph cellular osmotic pressure to achieve homeostasis.

• If not, physiological stress results.• Osmoregulation: maintenance of cellular pressure

relative to an external medium via transport of salts and other low molecular weight compounds (e.g., amino acids).

• Very energy-expensive activity.• Holding/production systems should be designed with

additional aeration for areas with high salinity flux.

Physical Variables: Salinity

• Euryhaline: having an osmoregulatory capacity and ability to tolerate varying levels of salinity.

• Stenohaline: limited tolerance• Most freshwater fish have a blood osmotic

pressure of 7 g/L.• If external salinity increases above this, growth

is reduced• Most species we culture around here are

euryhaline: red drum, penaeid shrimp, etc., but some aren't (oysters, urchins, catfish, tilapia)

Physical Variables: Salinity

• For fish and crustaceans, the body fluids are one solution, the surrounding pond water is the other solution.

• Freshwater species have body fluids more concentrated in ions than the surrounding water (hypersaline or hypertonic).

• Saltwater species are just the opposite: hyposaline or hypotonic.

Physical Variables: Salinity

• Although several marine crustacea are euryhaline, they cannot accommodate quick changes in salinity.

• They must be gradually acclimated.

• Most farms/hatcheries have facilities for acclimation.

• Rate should not typically exceed 1 or 2 ppt per hour.

Physical Variables: Electrical Conductance

• Electrical Conductance: the measurement of of the dissolved mineral content (salinity) of water.

• Changes in direct proportion to salinity.• Water ionizes slowly and, thus, is a poor

conductor of electricity.• Unit of measurement: microohm/cm• Range: 20 - 1,500, much higher for sw.• Can be used to estimate salinity or TDS.

Physical Variables: Turbidity

• Turbidity: measurement of light penetration in water.

• Produced by dissolved and suspended substances (clay, humics, silt, plankton, colored compounds).

• Typically measured with secchi disk or turbidometer.

• More dense = higher turbidity.• Some forms are more

desirable than others.

Physical Variables: Turbidity

• Clay turbidity of over 30 cm typically retards phytoplankton blooms in freshwater.

• Fine particles can increase respiratory rate, smother fish eggs, clog filtration equipment.

• Fish appear to be more sensitive to suspended solids than clay turbidity.

• Upper tolerance level: around 80 mg/L vs 20,000 mg/L for clay turbidity

Physical Variables: Total Gas Pressure

• Total Gas Pressure (TGP): the sum of the partial pressures of all gases dissolved in water.

• Barometric Pressure (BP): weight of the atmosphere imparted on water surface.

• equillibrium: TGP = BP• When TGP > BP, gas goes from water to atm.• When BP > TGP, gas goes from atm to water.

Physical Variables: Total Gas Pressure (implications)

• Supersaturation is an unstable condition, which can result in gas bubble trauma.

• Chronic % TGP of over 105% undesirable.

• Long-term exposure in catfish of 110% causes gas bubble trauma (Tucker and Robinson, 1990).

• Bubbles are formed when gas comes out of solution.

• Embolisms, restriction of flow in blood vessels.

Physical Variables: Total Gas Pressure (GB trauma)

• Gas Bubble Trauma is affected by submersion depth.

• Greater depth = hydrostatic pressure = gases remaining in solution.

• At 21oC, P is reduced by 67 mm Hg for every meter of submersion.

• Implications of tank culture?

• Implications for recirculating systems?

Chemical Properties: Dissolved Oxygen (DO)

• Along with temperature, dissolved oxygen (DO), is important in metabolic regulation.

• Dissolved oxygen concentration and temp both determine the environmental niche aquaculture organisms occupy.

• Occupation of niches is controlled by a complex set of behavioral and physiological (acclimatorial) activities.

• Acclimation is slow with D.O. (hours, weeks)

Chemical Variables: dissolved oxygen (DO)

• although oxygen is rather abundant in the atm (21%), it is only slightly soluble in water (6 mg/L is not much)

• implications to fish/invertebrates?

• Even metabolic rates of aqua-communities can effect rapid changes in [D.O.]

• this effect increases with temp (interaction)

• solubility decreases with increased temp/sal

• other factors: BP (direct), altitude (indirect), impurities (indirect)

Oxygen Solubility Curve

Chemical Variables: Dissolved Oxygen (DO)

Factors affecting D.O. consumption:– Water temperature (2-3x for every 10oC).– Environmental (medium) D.O. concentration

(determines lower limit).– Animal size (respiration greater for small vs. large).– Level of activity (resting vs. forced).– Post-feeding period, etc. (2x, 1-6 hrs post feeding).

Chemical Variables: Dissolved Oxygen (DO)

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

• Hard to determine due to compounding effects (can’t standardize conditions).

• Major factor: exposure time• For most species:

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

Oxygen/Temperature Interaction

• Oxygen consumption increases with temperature until a maximum is achieved.

• Peak consumption rate is maintained over a small temp range.

• Consumption rate decreases rapidly as temp increases.

• Lethal temperature finally achieved.

Diel Oxygen Fluctuation

• Typical pattern = oxygen max during late afternoon.

• Difference in surface vs. benthic for stratified ponds.

• Dry season = faster heating at surface and less variation.

Chemical Variables: Total Alkalinity

• Total Alkalinity: the total amount of titratable bases in water expressed as mg/L of equivalent CaCO3.

• “Alkalinity” is primarily composed of the following ions: CO3

-, HCO3-, hydroxides, ammonium,

borates, silicates, phosphates.

• Alkalinity in ponds is determined by both the quality of the water and bottom muds.

• Calcium is often added to water to increase its alkalinity, buffer against pH changes.

Chemical Variables: Total Alkalinity

• Thus, a total alkalinity determination of 200 mg/L would indicate good buffering capacity of a water source.

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

• Natural seawater is around 115-120 mg/L.• Seldom see pH problems in natural seawater.• Water having alkalinity reading of less than 30 mg/L

are problematic.

Chemical Variables: Total Alkalinity

Total Alkalinity level can be associated with several potential problems:

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

• Natural waters with less than 40 mg/L alkalinity as CaCO3 have limited. biofiltration capacity, pH independent

• Low alkalinity = low CO2→ low nat prod.

• Low alkalinity = high pH.

Chemical Variables: Total Hardness

• Total Hardness: total concentration of metal ions expressed in terms of mg/L of equiva- lent CaCO3.

• Primary ions are Ca2+ and Mg2+, also iron and manganese.

• Total Hardness approximates total alkalinity.• Calcium is used for bone and exoskeleton

formation and absorbed across gills.• Soft water = molt problems for crustaceans, bone

deformities.

Chemical Variables: pH

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

• pH: the negative logarithm of the hydrogen ion concentration (activity) of a substance.

• Most salt water aquaria regulate pH to 8.1, similar to seawater

• pH of ocean water is stable due to carbonate buffering system

Chemical Variables: pH

• Other sources of change:– Decay of organic matter.– Oxidation of compounds in bottom sediments.

– Depletion of CO2 by phytoplankton on diel basis.

– Oxidation of sulfide containing minerals in bottom soils (e.g., oxidation of iron pyrite by sulfide oxidizing bacteria under anaerobic conditions).

Chemical Variables: Carbon Dioxide

• Normal component of all natural waters.• Sources: atmospheric diffusion, respiration of

cultured species, biological oxidation of organic compounds.

• Usually transported in the blood as HCO3-

• Converted to CO2 at the gill interface, diffusion into medium.

• As the level of CO2 in the medium increases, the gradient allowing diffusion is less.

Chemical Variables: carbon dioxide

• Concentrations of CO2 are small, even though it is highly soluble in water

• inverse relationship between [CO2] and temperature/salinity

• thus, CO2 solubility depends upon many factors

Chemical Variable: Carbon Dioxide

• CO2 is not particularly toxic to fish or invertebrates, given sufficient D.O. is available.

• Maximum tolerance level appears to be around 50 mg/L for most species.

• Good working level of around 15-20 mg/L.• Diel fluctuation opposite to that of D.O.• Higher levels in warmer months of year.

Dissolved GasesDissolved Gases• The proportions of gases in the The proportions of gases in the

atmosphere is not the same as their atmosphere is not the same as their proportions in seawater, (Table 7.4)proportions in seawater, (Table 7.4)

• There is less NThere is less N22 (nitrogen gas) in the ocean (nitrogen gas) in the ocean than in the atmosphere, than in the atmosphere,

• much more oxygen, much more oxygen, • and even more COand even more CO22. . • All this COAll this CO22 in the oceans keeps CO in the oceans keeps CO22 from from

being in the atmosphere and causing being in the atmosphere and causing global warming. global warming.

• The colder the water, the more The colder the water, the more gas can dissolve in itgas can dissolve in it. .

• When you leave your can of pop in the When you leave your can of pop in the car in the sun, then open it, what car in the sun, then open it, what happens? happens?

• Pop sprays all over you. Pop sprays all over you. • That's because the gas has exsolved That's because the gas has exsolved

(come out of solution); a lot has (come out of solution); a lot has accumulated in the little space at the accumulated in the little space at the top of the can. top of the can.

• Very active fish, such as trout and salmon, Very active fish, such as trout and salmon, require very cold water to live in because require very cold water to live in because they have high oxygen requirements. they have high oxygen requirements.

• They literally suffocate when the water They literally suffocate when the water gets too warm, and the oxygen levels drop. gets too warm, and the oxygen levels drop.

• This explain why these fish don't live down This explain why these fish don't live down south.south.

• 'Thermal pollution' occurs when electric 'Thermal pollution' occurs when electric plants put warm water into streams, plants put warm water into streams, lowering the oxygen levellowering the oxygen level..

• COCO22 is important because it is needed by is important because it is needed by plants so they can photosynthesize. plants so they can photosynthesize.

• OO22 is important because animals need it for is important because animals need it for respiration:respiration:photosynthesisphotosynthesis: :

• COCO22 + H + H22O + energy [from the sun] O + energy [from the sun] O O22 + sugar (organic matter)+ sugar (organic matter)respiration (the reverse of respiration (the reverse of photosynthesis): photosynthesis):

• OO22 + sugar + sugar COCO22 + H + H22O + energyO + energy

Dissolved OxygenDissolved Oxygen

• seawater\atmosphere exchange at seawater\atmosphere exchange at air water interface only (f.7.8)air water interface only (f.7.8)

• biological processes that affect Obiological processes that affect O22 concentration: photosynthesis and concentration: photosynthesis and respirationrespiration

• typical distribution of Otypical distribution of O22 in water in water column and processes that control column and processes that control this distributionthis distribution

Phytoplankton NutrientsPhytoplankton Nutrients

• inorganic sources of N, P, S and other inorganic sources of N, P, S and other atoms required for phytoplankton atoms required for phytoplankton growthgrowth

• photosynthesis and respiration photosynthesis and respiration contributes in nutrient distributioncontributes in nutrient distribution

• Especially important, because so much is Especially important, because so much is needed, are needed, are N (nitrogen) and P (phosphorus). N (nitrogen) and P (phosphorus).

• Si (silica)Si (silica) is also important for all the siliceous is also important for all the siliceous organisms we've discussed: diatoms, organisms we've discussed: diatoms, radiolarians, and siliceous sponges.radiolarians, and siliceous sponges.

• N is necessary to make proteins. N is necessary to make proteins. • P is necessary to make new cells (it's part of the P is necessary to make new cells (it's part of the

cell wall), and also genetic material, DNA and cell wall), and also genetic material, DNA and RNA.RNA.

• N is useful for plants only in these forms: N is useful for plants only in these forms: • NONO33

-- nitratenitrate

• NONO22-- nitritenitrite

• NHNH44++ ammoniumammonium

• NN22, the gas, is not usable by most plants. , the gas, is not usable by most plants. • Only a few bacteria can break this very strong Only a few bacteria can break this very strong

molecule apart and turn it into nitrate. molecule apart and turn it into nitrate. • These are 'nitrogen-fixing bacteria'.These are 'nitrogen-fixing bacteria'.• P is useful in the form of P is useful in the form of phosphatephosphate, PO, PO44

3-3-

• Thus weathering, sedimentation, and Thus weathering, sedimentation, and ocean chemistry are all closely linked.ocean chemistry are all closely linked.

• Other ions in seawater, such as Cl Other ions in seawater, such as Cl –– and and SOSO4 4 , are not derived from weathering, but , are not derived from weathering, but

from volcanic degassing.from volcanic degassing.

The Carbonate System in The Carbonate System in SeawaterSeawater

• COCO22 in seawater is controlled by: ( f.7-10- in seawater is controlled by: ( f.7-10-

11)11)

• Exchange with the atmosphereExchange with the atmosphere

• Photosynthesis/Respiration: Photosynthesis/Respiration:

• 6CO6CO22 + 6H + 6H22 O O CC66 H H1212 O O66 + 6O + 6O22

The Carbonate BufferThe Carbonate Buffer

• Carbon Dioxide: COCarbon Dioxide: CO22 , ,

• Carbonic Acid: HCarbonic Acid: H22COCO33 , ,

• Bicarbonate: HCOBicarbonate: HCO33 , ,

• Carbonate: COCarbonate: CO332-2-

• COCO22 + H + H22O O HH22COCO33 . .

• HH22COCO33 HCOHCO33 + H+ H+2.+2.

• HCOHCO33 COCO332-2-+ H + H +3.+3.

• Another important reaction is the dissolution and Another important reaction is the dissolution and precipitation of calcium carbonate:precipitation of calcium carbonate:

• COCO33 + Ca + Ca+2+2 CaCO CaCO334.4...

• Importance of these reactionImportance of these reactions:s:• Maintain constant pH (seawater is said to be Maintain constant pH (seawater is said to be

buffered). buffered). • Few marine organisms can tolerate a pH very Few marine organisms can tolerate a pH very

different from 8.different from 8.

Biological ProductivityBiological Productivity• In general, shells of organisms are likely to In general, shells of organisms are likely to

be preserved where their production rate be preserved where their production rate is high, is high,

• Siliceous shells are preserved only where Siliceous shells are preserved only where the production rate is high. the production rate is high.

• Siliceous oozes occur where productivity Siliceous oozes occur where productivity rate is high and terrigenous sedimentation rate is high and terrigenous sedimentation rate low.rate low.

• Carbonate shells: the oceans are Carbonate shells: the oceans are supersaturated with respect to CaCOsupersaturated with respect to CaCO33 at the at the surface and become increasingly surface and become increasingly undersaturated with depth.undersaturated with depth.

• Shells more likely to be preserved at shallow Shells more likely to be preserved at shallow depth.depth.

• Lysocline: depth at which rapid dissolution of Lysocline: depth at which rapid dissolution of CaCOCaCO33 begins. begins.

• This is deeper than the depth where ocean This is deeper than the depth where ocean becomes undersaturated.becomes undersaturated.

CCDCCD• Carbonate Compensation Depth (or ‘snow Carbonate Compensation Depth (or ‘snow

line’): line’):

• depth where dissolution>supply of CaCOdepth where dissolution>supply of CaCO33

andand

• below which CaCObelow which CaCO33 shells are not shells are not

preserved in sediment.preserved in sediment.