BIOL 4120: Principles of EcologyBIOL 4120: Principles of Ecology

Lecture 4: Aquatic Lecture 4: Aquatic EnvironmentEnvironment

Dafeng HuiDafeng Hui

Room: Harned Hall 320Room: Harned Hall 320

Phone: 963-5777Phone: 963-5777

Email: dhui@tnstate.eduEmail: dhui@tnstate.edu

Topics for this class:

4.1 Global water cycling between Earth and 4.1 Global water cycling between Earth and atmosphereatmosphere

4.2 Physical properties of water (H2O)4.2 Physical properties of water (H2O)4.3 Light in aquatic environments4.3 Light in aquatic environments4.4 Temperature in aquatic environments4.4 Temperature in aquatic environments4.5 Oxygen (O2) in aquatic environments4.5 Oxygen (O2) in aquatic environments4.6 Acidity in aquatic environments4.6 Acidity in aquatic environments4.7 Water movement in fresh water and marine 4.7 Water movement in fresh water and marine

environmentsenvironments4.8 Tides in marines coastal environment4.8 Tides in marines coastal environment4.9 Transition zone (estuaries)4.9 Transition zone (estuaries)

Water is essential for life Water is essential for life (75-95% weight of living (75-95% weight of living cell)cell)

Over 75% of the EarthOver 75% of the Earth’’s s surface is covered by surface is covered by waterwater

• Oceans contain 97%.Oceans contain 97%.

• Polar ice caps and Polar ice caps and glaciers contain 2%.glaciers contain 2%.

• Freshwater in lakes, Freshwater in lakes, streams, and ground streams, and ground water make up less water make up less than 1%.than 1%.

(Saltwater and fresh (Saltwater and fresh water)water)

4.1 Global Hydrologic (water) cycle 4.1 Global Hydrologic (water) cycle between Earth and atmosphere Cyclebetween Earth and atmosphere Cycle

The The waterwater (or (or hydrologichydrologic) ) cyclecycle is is the process by which water travels in the process by which water travels in a sequence from the air to Earth and a sequence from the air to Earth and returns to the atmospherereturns to the atmosphere

Solar radiation is the driving force Solar radiation is the driving force behind the water cycle because it behind the water cycle because it provides energy for the evaporation provides energy for the evaporation of waterof water

Water Cycles between Earth and Water Cycles between Earth and the Atmospherethe Atmosphere

The Hydrologic CycleThe Hydrologic Cycle

Precipitation Precipitation (PPT)(PPT)

InterceptionInterception InfiltrationInfiltration Groundwater Groundwater

rechargerecharge RunoffRunoff Evaporation Evaporation

(E)(E) Transpiration Transpiration

(T)(T)

Distribution of water is not static (processes)

Global water budgetGlobal water budgetLandPools (10^3 km3):Glaciers: 29,000Groundwater:4,000Lake: 229Soil: 67Fluxes (km3/yr):PPT: 111,000ET: 71,000River flow:40,000

OceanPools:Ocean:1.37*10^6Fluxes:PPT:385,000ET: 425,000

Water Reservoirs and fluxes

(Horne & Goldman, 1994)

Renewal Time300-11,000 yrs12,000 yrs60-300 yrs330 days

7-11 days7 days

In water (HIn water (H22O), the atoms are O), the atoms are asymmetrically bound to one anotherasymmetrically bound to one another

The hydrogen atoms share an The hydrogen atoms share an electron with the oxygen atom electron with the oxygen atom through a through a covalentcovalent bondbond• Because electrons are unequally shared Because electrons are unequally shared

and spend more time around oxygen, and spend more time around oxygen, water is considered a water is considered a polarpolar molecule molecule

Because of their polarity, water Because of their polarity, water molecules bond with one another due molecules bond with one another due to hydrogen bondingto hydrogen bonding

4.2 Water Has Important Physical 4.2 Water Has Important Physical PropertiesProperties

4.2 Physical properties of water (H2O)4.2 Physical properties of water (H2O)

Basic Structure 1. Covalent bonding of 2H + O atoms 2. Polar-covalent bond 3. Inter-molecule attraction 4. H-bonds among water moleculars

Physical and chemical propertiesPhysical and chemical properties High specific heat capacity:High specific heat capacity: Specific Heat: 1.0 (also called Heat Capacity)Specific Heat: 1.0 (also called Heat Capacity)

• calories required to raise 1 g H2O 1oC calories required to raise 1 g H2O 1oC high high

• (e.g. from 10 to 11oC)(e.g. from 10 to 11oC) Latent heat: energy released or absorbed in the Latent heat: energy released or absorbed in the

transformation of water from one state to another.transformation of water from one state to another. 1 calorie to raise 1oC; 536 calories to change 100oC 1 calorie to raise 1oC; 536 calories to change 100oC

water to vapor; 86 calories ice to 1oC waterwater to vapor; 86 calories ice to 1oC water Peculiar density-temperature relationshipPeculiar density-temperature relationship density increases as T decreases (when T> 4density increases as T decreases (when T> 4ooC), then C), then

decrease to 0decrease to 0ooC, freezing (ice)C, freezing (ice) CohesionCohesion

Due to the hydrogen bonding, water molecules tend to Due to the hydrogen bonding, water molecules tend to stick firmly to each other, resisting external forces that stick firmly to each other, resisting external forces that would break the bonds (drop of water, transpiration).would break the bonds (drop of water, transpiration).

Properties (cont.)Properties (cont.)

Surface tension-strong Surface tension-strong attraction within the attraction within the water body and water body and weaker attraction in weaker attraction in the surface caused the surface caused that molecules at the that molecules at the surface are drawn surface are drawn downward.downward.

High viscosity: Viscosity: property of a material that measures

the force necessary to separate the molecules and allow passage of an object through liquid.

Frictional resistance is 100 times greater than air.

Water is 860 times denser than air.• Organisms in water have similar density to Organisms in water have similar density to

water, the neutral buoyancy helps against the water, the neutral buoyancy helps against the force of gravity, thus require less investment force of gravity, thus require less investment in structure material such as skeletonsin structure material such as skeletons

• Organisms in deep water need to adapt to the Organisms in deep water need to adapt to the high pressure (20 to 1000 atm).high pressure (20 to 1000 atm).

4.3 Light in aquatic environments4.3 Light in aquatic environments

Reflection

Interception by particles: absorb or scatter by

Absorption by water: shortwave+

Red, yellow, green and violet

Only blue wavelength to penetrate deeper water

Change in light quantity and quality have important implications to life in aquatic environments.

4.4 Temperature in aquatic 4.4 Temperature in aquatic environmentsenvironments

Temperature change is the result of the exponential decline in solar radiation with water depth.

T profile in the ocean

The vertical profile of T varies seasonally.

Fall turnover: cool dense surface water sinks, displace the warmer water below, create uniform T.

Flowing body of water (stream or river) has a quite different T Flowing body of water (stream or river) has a quite different T profile. Must take into account all the factorsprofile. Must take into account all the factors• Water and its depthWater and its depth• Temperature AltitudeTemperature Altitude• Geography Biotic environmentGeography Biotic environment

4.5 Oxygen concentration in 4.5 Oxygen concentration in aquatic environmentaquatic environment

O2 is dissolved in water

O2 concentration in water is determined by solubility and diffusion.

High O2 in the surface due to diffusion

Vertical profile of oxygen in the Vertical profile of oxygen in the Atlantic OceanAtlantic Ocean

O2 declines to minimum O2 zone (500-1000 m). The increase caused by influx of O2 rich cold water sank in the polar water.

4.6 Water functions as a solvent4.6 Water functions as a solvent

Solution: a homogeneous liquid with 2 or more substances mixed.

Solvent: dissolving agent

Solute: substance that is dissolved

Aqueous solution: water as solvent

Ions: Compounds of electrically charged atoms

Cations: positive

Anions: negative

Practical salinity units (PSU, o/oo): grams of chlorine per kilogram of water.

Ocean: 35 unit, Fresh water: 0.065-0.30 unit)

4.7 Acidity has a widespread influence 4.7 Acidity has a widespread influence on aquatic environmentson aquatic environments

Acidity: the abundance of hydrogen ions (H+) in solution.

Alkalinity: abundance of hydroxyl ions (OH-) in solution

Acidity in water is related to carbon dioxide (CO2).

Forms of CarbonForms of Carbon Carbon-bicarbonate equilibriumCarbon-bicarbonate equilibrium

• Carbon dioxide:Carbon dioxide: CO CO22

• Carbonic acid:Carbonic acid: H H22COCO33

• Bicarbonate:Bicarbonate: HCO HCO33--

• Carbonate:Carbonate: CO CO332-2-

CO2 + H2O H2CO3 HCO3- + H+ CO3

2- + 2H+

Measurement: pH =-log([H+])

(value between 1-14) Pure water: 7 Acidic: <7 Alkaline: >7

Ocean water tends to be slightly alkaline with a pH range of 7.5-8.4

Proportions of the formsProportions of the formsof COof CO22 in Relation to pH in Relation to pH

pH CO2 HCO3– CO3

=

4 0.996 0.004 1.26 x 10-9

5 0.962 0.038 1.20 x 10-7

6 0.725 0.275 0.91 x 10-5

7 0.208 0.792 2.60 x 10-4

8 0.025 0.972 3.20 x 10-3

9 0.003 0.966 0.031

10 0.000 0.757 0.243

Free Bicarbonate Carbonate

4.8 Water movements shape fresh 4.8 Water movements shape fresh water and marine environmentswater and marine environments

Water movement Water movement in the fresh waterin the fresh water• Stream flow rate Stream flow rate

(velocity of a (velocity of a stream)stream)

• Determined byDetermined by Shape and Shape and

steepness of streamsteepness of stream Intensity of rainfallIntensity of rainfall

If Flow Rate>50 If Flow Rate>50 cm/s, remove all >5 cm/s, remove all >5 mm in diametermm in diameter

Water movement in the ocean (lake)Water movement in the ocean (lake)• WaveWave• Generated by windGenerated by wind

Upwelling:

4.9 Tides dominate the marine 4.9 Tides dominate the marine coastal environmentcoastal environment

Tides: due to Tides: due to the the gravitational gravitational pulls of the pulls of the Sun and the Sun and the Moon.Moon.

Tides are not entirely regular, nor are they the Tides are not entirely regular, nor are they the same all over the Earth.same all over the Earth.

Atlantic: semi-daily; Gulf of Mexico: one daily Atlantic: semi-daily; Gulf of Mexico: one daily tide; Pacific: mixed tides.tide; Pacific: mixed tides.

Centrifugal force: 3.38

3.493.27

Intertidal ZonationIntertidal Zonation

Intertidal zone: area lying between the water line of high and low tide.

Dramatic shifts in env. Conditions:

Inundation and exposure

4.10 Transition zone (Estuary)4.10 Transition zone (Estuary)

Estuary: place where fresh water joins and Estuary: place where fresh water joins and mixes with the saltwater.mixes with the saltwater.

Features:Features:• Considerable fluctuation in temperature, both Considerable fluctuation in temperature, both

daily and seasonally.daily and seasonally.• Large variation in salinity (vertical and Large variation in salinity (vertical and

horizontal)horizontal) Tidal overmixing: unstable salinity, saltwater on Tidal overmixing: unstable salinity, saltwater on

surface tends to sink as lighter fresh water in bottom surface tends to sink as lighter fresh water in bottom rises, and mixing takes place from the surface to the rises, and mixing takes place from the surface to the bottom.bottom.

Limited number of species and high production.Limited number of species and high production.

Vertical and horizontal stratification Vertical and horizontal stratification of salinity from river mouth to the of salinity from river mouth to the

estuaryestuary

The ENDThe END