1. BIOL 4120: Principles of Ecology Lecture 4: Aquatic Environment
Dafeng Hui
Room: Harned Hall 320
Phone:

2. Topics for this class:
4.1 Global water cycling between Earth and atmosphere
4.2 Physical properties of water (H2O)
4.3 Light in aquatic environments
4.4 Temperature in aquatic environments
4.5 Oxygen (O2) in aquatic environments
4.6 Acidity in aquatic environments
4.7 Water movement in fresh water and marine environments
4.8 Tides in marines coastal environment
4.9 Transition zone (estuaries)

3. 4.1 Global Hydrologic (water) cycle between Earth and atmosphere Cycle
Water is essential for life (75-95% weight of living cell)
Over 75% of the Earth’s surface is covered by water
Oceans contain 97%.
Polar ice caps and glaciers contain 2%.
Freshwater in lakes, streams, and ground water make up less than 1%.
(Saltwater and fresh water)

4. Water Cycles between Earth and the Atmosphere
The water (or hydrologic) cycle is the process by which water travels in a sequence from the air to Earth and returns to the atmosphere
Solar radiation is the driving force behind the water cycle because it provides energy for the evaporation of water

5. The Hydrologic Cycle Precipitation (PPT) Interception Infiltration
Groundwater recharge
Runoff
Evaporation (E)
Transpiration (T)
Distribution of water is not static (processes)

6. Global water budget Land Pools (10^3 km3): Glaciers: 29,000
Groundwater:4,000
Lake: 229
Soil: 67
Fluxes (km3/yr):
PPT: 111,000
ET: 71,000
River flow:40,000
Ocean
Pools:
Ocean:1.37*10^6
Fluxes:
PPT:385,000
ET: 425,000

7. Water Reservoirs and fluxes
Renewal Time
300-11,000 yrs
12,000 yrs
yrs
330 days
7-11 days
7 days
(Horne & Goldman, 1994)

8. 4.2 Water Has Important Physical Properties
In water (H2O), the atoms are asymmetrically bound to one another
The hydrogen atoms share an electron with the oxygen atom through a covalent bond
Because electrons are unequally shared and spend more time around oxygen, water is considered a polar molecule
Because of their polarity, water molecules bond with one another due to hydrogen bonding

9. 4.2 Physical properties of water (H2O)
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4.2 Physical properties of water (H2O)
water is a polar molecule and that liquid water is held together by the hydrogen bonding that results from that polarity
Basic Structure
1. Covalent bonding of 2H + O atoms
2. Polar-covalent bond
3. Inter-molecule attraction
4. H-bonds among water moleculars

10. Physical and chemical properties
4/22/2017
Physical and chemical properties
High specific heat capacity:
Specific Heat: 1.0 (also called Heat Capacity)
calories required to raise 1 g H2O 1oC high
(e.g. from 10 to 11oC)
Latent heat: energy released or absorbed in the transformation of water from one state to another.
1 calorie to raise 1oC; 536 calories to change 100oC water to vapor; 86 calories ice to 1oC water
Peculiar density-temperature relationship
density increases as T decreases (when T> 4oC), then decrease to 0oC, freezing (ice)
Cohesion
Due to the hydrogen bonding, water molecules tend to stick firmly to each other, resisting external forces that would break the bonds (drop of water, transpiration).
Link to organism: 75-95% water, relative stable T
Presence of ice on the surface bodies functions to insulate the waters below, helping to keep larger bodies of water from freezing solid during winter months.

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

12. Frictional resistance is 100 times greater than air.
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 water, the neutral buoyancy helps against the force of gravity, thus require less investment in structure material such as skeletons
Organisms in deep water need to adapt to the high pressure (20 to 1000 atm).
Buoyancy: when a body is immesed in water, but its weight is less than that of water, itwill be subjected to an upward force called …
Sea level: pressure is 1 atm
Every 10 meter in the water, pressure increase 1 atm

13. 4.3 Light in aquatic environments
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4.3 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
Properties of water influence all the organisms living there. Environmental factors also will influence the organisms, both plants and animals. See how environmental changes.
Light strikes the surface of water: reflection
Intercept and absorb or scatter it.
Even in clear water, only 40% shortwave radiation reaches a depth of 1 meter. Water first absorbs visible Red light and infrared radiation. Then yellow, followed by green and violet, leaving only blue wavelengths to penetrate deeper water.
Change in light quantity and quality have important implications to life in aquatic environments.

14. Figure 3.7

15. 4.4 Temperature in aquatic environments
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.
Epilimnion
Thermoclined
Hypolimnion

16. 4/22/2017
Meadow
Temperature affects stream community, influencing presence or absence of cool-water (trout, small-mouthed bass) and warm-water (catfish, suckers ) speciese.
Flowing body of water (stream or river) has a quite different T profile. Must take into account all the factors
Water and its depth
Temperature Altitude
Geography Biotic environment

17. 4.5 Oxygen concentration in aquatic environment
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4.5 Oxygen concentration in aquatic environment
O2 is dissolved in water
O2 concentration in water is determined by solubility and diffusion.
High O2 in the surface due to diffusion
Diffusion: general tendency of molecules to move from a region of high concentration to low concentration.
O2 diffuse much slower in water than in air (10,000 times)

18. Vertical profile of oxygen in the Atlantic Ocean
O2 declines to minimum O2 zone ( m). The increase caused by influx of O2 rich cold water sank in the polar water.
O2 is not a limiting factor in terrestrial environments (21%). O2 in the water is 0.01 liters per liter (1%) maximum in fresh water at 0 oC. O2 often limits respiration and metabolic activity.

19. 4.6 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: unit)
Cl-1: chloride ions

20. 4.7 Acidity has a widespread influence on 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).
Solubility of CO2 is different to O2, it reacts with H2O.

21. Forms of Carbon Carbon-bicarbonate equilibrium Carbon dioxide: CO2
4/22/2017
Forms of Carbon
Carbon-bicarbonate equilibrium
Carbon dioxide: CO2
Carbonic acid: H2CO3
Bicarbonate: HCO3-
Carbonate: CO32-
Water has a considerable capacity to absorb CO2, thus it is abundant in both fresh and saltwater.
When CO2 diffused into surface of water, it reacts with H2O to produce H2CO3. H2CO3 dirther disassociates into a H+ and a HCO3-. Biocarbonate may further disassociate into carbonate and H+.
This reaction reproduce or absorb H+.
Generally, the most important source of carbon for photosynthesis
CO2 + H2O H2CO3 HCO3- + H+ CO H+

22. 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
Alkaline (have large number of OH- (hydroxyl ions).

23. 4/22/2017
pH exerts a power influence on distribution and abundance of organisms. When pH<4.5, majority organisms can’t survive. At low pH, aluminum begins to dissove. Aluminum is highly toxic to many species, and leads to decline in aquatic population.

24. Proportions of the forms of CO2 in Relation to pH
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Proportions of the forms of CO2 in Relation to pH
Free
Bicarbonate
Carbonate
pH CO2 HCO3– CO3=
x 10-9
x 10-7
x 10-5
x 10-4
x 10-3
The CO2-carbonic acid-biocarbonate-carbonate system functions as a buffer to keep the pH of water within a narrow range. It does this by absrob H+ when H+ are in excess, and produce it when they are in short supply.
At ph=7, most of CO2 is presented as HCO3-. At a high pH, more CO2 is presented as CO3-2-. At low pH, most of CO2 is presented as free CO2.

25. 4.8 Water movements shape fresh water and marine environments
Water movement in the fresh water
Stream flow rate (velocity of a stream)
Determined by
Shape and steepness of stream
Intensity of rainfall
If Flow Rate>50 cm/s, remove all >5 mm in diameter
A fast mountain stream and a slow-flowing stream. Different environmental conditions, and support quite different forms of aquatic life.

26. Water movement in the ocean (lake)
Wave
Generated by wind
Along the equator, the Coriolis effect acts to pull the westward-flowing currents to the north and south, resulting in an upwelling of deeper cold waters to the surface.
Upwelling:

27. 4.9 Tides dominate the marine coastal environment
Tides: due to the gravitational pulls of the Sun and the Moon.
3.49
3.27
Centrifugal force: 3.38
Tides influence the rhythm of life on ocean shores.
Movement of the earth and the moon: cen’trifugal force is 3.38 mg (to a kg of mass on earth)
Tides are not entirely regular, nor are they the same all over the Earth.
Atlantic: semi-daily; Gulf of Mexico: one daily tide; Pacific: mixed tides.

28. Intertidal Zonation Dramatic shifts in env. Conditions:
Inundation and exposure
Intertidal zone: area lying between the water lines of high and low tide
Inundation
Daily patter of inundatoin and exposure: wild temperature 38->10oC, intense solar radiation
Intertidal zone: area lying between the water line of high and low tide.

29. 4.10 Transition zone (Estuary)
Estuary: place where fresh water joins and mixes with the saltwater.
Features:
Considerable fluctuation in temperature, both daily and seasonally.
Large variation in salinity (vertical and horizontal)
Tidal overmixing: unstable salinity, saltwater on surface tends to sink as lighter fresh water in bottom rises, and mixing takes place from the surface to the bottom.
Limited number of species and high production.
High production because of high nutrient from streams and rivers.

30. Vertical and horizontal stratification of salinity from river mouth to the estuary
Brown: high tide
Blue: low tide.
Salinity increases with depth, as lighter freshwater flows over the denser saltwater.

31. The END