BIOL 4120 Principles of Ecology Lecture 4 Aquatic

BIOL 4120: Principles of Ecology Lecture 4: Aquatic Environment Dafeng Hui Room: Harned Hall 320 Phone: 963 -5777 Email: dhui@tnstate. edu

Topics for this class: 4. 1 Global water cycling between Earth and atmosphere 4. 2 Physical properties of water (H 2 O) 4. 3 Light in aquatic environments 4. 4 Temperature in aquatic environments 4. 5 Oxygen (O 2) 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)

4. 1 Global Hydrologic (water) cycle between Earth and atmosphere Cycle n n 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)

Water Cycles between Earth and the Atmosphere n n 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

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

Global water budget Land Pools (10^3 km 3): Glaciers: 29, 000 Groundwater: 4, 000 Lake: 229 Soil: 67 Fluxes (km 3/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

Water Reservoirs and fluxes Renewal Time 300 -11, 000 yrs 12, 000 yrs 60 -300 yrs 330 days 7 -11 days 7 days (Horne & Goldman, 1994)

4. 2 Water Has Important Physical Properties n n In water (H 2 O), 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 n Because of their polarity, water molecules bond with one another due to hydrogen bonding

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

Physical and chemical properties n n n High specific heat capacity: Specific Heat: 1. 0 (also called Heat Capacity) • calories required to raise 1 g H 2 O 1 o. C high • (e. g. from 10 to 11 o. C) Latent heat: energy released or absorbed in the transformation of water from one state to another. 1 calorie to raise 1 o. C; 536 calories to change 100 o. C water to vapor; 86 calories ice to 1 o. C water Peculiar density-temperature relationship density increases as T decreases (when T> 4 o. C), then decrease to 0 o. C, 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).

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

n n n 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).

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

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.

n 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

4. 5 Oxygen concentration in aquatic environment High O 2 in the surface due to diffusion O 2 is dissolved in water O 2 concentration in water is determined by solubility and diffusion.

Vertical profile of oxygen in the Atlantic Ocean O 2 declines to minimum O 2 zone (5001000 m). The increase caused by influx of O 2 rich cold water sank in the polar water.

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: 0. 065 -0. 30 unit)

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 (CO 2).

Forms of Carbon n Carbon-bicarbonate equilibrium • Carbon dioxide: CO 2 • Carbonic acid: H 2 CO 3 • Bicarbonate: HCO 3 • Carbonate: CO 32 - CO 2 + H 2 O H 2 CO 3 HCO 3 - + H+ CO 32 - + 2 H+

n Measurement: p. H =-log([H+]) (value between 1 -14) n n Pure water: 7 Acidic: <7 Alkaline: >7 Ocean water tends to be slightly alkaline with a p. H range of 7. 5 -8. 4

Proportions of the forms of CO 2 in Relation to p. H Free Bicarbonate Carbonate p. H CO 2 HCO 3– CO 3= 4 5 6 0. 996 0. 962 0. 725 0. 004 0. 038 0. 275 1. 26 x 10 -9 1. 20 x 10 -7 0. 91 x 10 -5 7 8 9 10 0. 208 0. 025 0. 003 0. 000 0. 792 0. 972 0. 966 0. 757 2. 60 x 10 -4 3. 20 x 10 -3 0. 031 0. 243

4. 8 Water movements shape fresh water and marine environments n Water movement in the fresh water • Stream flow rate (velocity of a stream) • Determined by n n n Shape and steepness of stream Intensity of rainfall If Flow Rate>50 cm/s, remove all >5 mm in diameter

n Water movement in the ocean (lake) • Wave • Generated by wind Upwelling:

4. 9 Tides dominate the marine coastal environment 3. 27 3. 49 Centrifugal force: 3. 38 Tides: due to the gravitational pulls of the Sun and the Moon. 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.

Intertidal Zonation Dramatic shifts in env. Conditions: Inundation and exposure Intertidal zone: area lying between the water line of high and low tide.

4. 10 Transition zone (Estuary) n n 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) n n 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.

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

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