Reminder: Week 1 online reading assignment\Reminder: Week 1 online reading assignment\www.physicalgeography.net/fundamentals/chapter8.html

OPTIONAL Study Aid for this reading will be posted on lab website OPTIONAL Study Aid for this reading will be posted on lab website

Fig. 8q-1 some of the major surface ocean currentsFig. 8q-1 some of the major surface ocean currents

• Where are the cold currents? the warm currents?

• Which are linked to major ocean upwelling zones persistent on eastern boundaries of the Atlantic, Pacific & Indian Oceans?( *California, Peru, Canary, Benguela & W. Australia currents)

Light in water: lecture slides plus take-home study aid slidesLight in water: lecture slides plus take-home study aid slides

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Tropical species show great shapes

Homework:Homework: Read On-line web pages Read On-line web pages (links therein are optional) (links therein are optional)  ““What is hydrologic optics”What is hydrologic optics”             http://www.serc.si.edu/labs/phytoplankton/primer/hydrops.jsp http://www.serc.si.edu/labs/phytoplankton/primer/hydrops.jsp “The Color of the Ocean“The Color of the Ocean”” http://science.hq.nasa.gov/oceans/living/color.html

Homework: Chapter 10 in your reader: Homework: Chapter 10 in your reader: LightLight

Review: Review: Light travels as Light travels as waves of energy waves of energy (hv), (hv), Light energy is quantified in Watts or Joules, terms used in heat budgetsLight energy is quantified in Watts or Joules, terms used in heat budgets

Photosynthetically AvailableRadiation = PAR

1.1. Waves of light have different Waves of light have different wavelengths (wavelengths (),), expressed as nanometers (nm) or Angstroms (A) expressed as nanometers (nm) or Angstroms (A) 1 nm = 10 A1 nm = 10 A

2.2. Purple and blue light waves have short Purple and blue light waves have short . . Red light has a longer Red light has a longer

3.3. Short Short carry more energy than Long carry more energy than Long ..

4. When the 4. When the of light matches the distance of light matches the distance ofof spacing in a chemical bond, then the spacing in a chemical bond, then the energy (hv) of the light is transferred to the energy (hv) of the light is transferred to the energy of the chemical =energy of the chemical = AbsorptionAbsorption

5. All molecules absorb light energy.. 5. All molecules absorb light energy.. Most dissipate the absorbed energy as heatMost dissipate the absorbed energy as heate.g. He.g. H22O, COO, CO22

Because of their dual Because of their dual nature as particles and nature as particles and waves, photons are waves, photons are often shown as often shown as squiggly lines.squiggly lines.

Conceptualization Conceptualization of a photonof a photon

• Light is absorbed in packets of energy Light is absorbed in packets of energy • Each packet = 1 photon =1 quantumEach packet = 1 photon =1 quantum• Energy content of a photon variesEnergy content of a photon varies inversely inversely with wavelength with wavelength• Measurements of rate of incoming photons are usually expressed in units of Measurements of rate of incoming photons are usually expressed in units of moles of photons/area/time = moles of photons/area/time = Photon Density FluxPhoton Density Flux (PDF) = Irradiance (I) (PDF) = Irradiance (I)

Light also acts like a Stream of Particles, called Light also acts like a Stream of Particles, called PhotonsPhotons or or QuantaQuanta (hv). (hv).Most important to study of biology (photosynthesis, photochemistry, bio-optics)Most important to study of biology (photosynthesis, photochemistry, bio-optics)

Absorbed photon increases Absorbed photon increases the the resonance energyresonance energy of the of the chemical , pushing electron chemical , pushing electron to higher excited state.to higher excited state.

of chemical bonds

That “extra” That “extra” resonance energyresonance energy can can transferred between chemicals (e.g. transferred between chemicals (e.g. pigments) in packets called pigments) in packets called excitonsexcitons. . Energy transductionEnergy transduction

Light Absorption & Resonance Energy Transduction are 1st steps in PhotosynthesisLight Absorption & Resonance Energy Transduction are 1st steps in Photosynthesis

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

PARPAR (400-700 nm)(400-700 nm) = photosynthetically available radiation = photosynthetically available radiation

= = s absorbed by photosynthetics pigmentss absorbed by photosynthetics pigments

Sum of all ‘colors’ of light energies of PARSum of all ‘colors’ of light energies of PAR = = white light PARwhite light PAR, with flux , with flux QQ = = QQPARPAR

For a narrow waveband of PAR (e.g. blue light) For a narrow waveband of PAR (e.g. blue light) = = spectral PARspectral PAR, with flux , with flux QQ = = QQPAR(PAR())

Solar radiation (sunlight) at the ocean surfaceSolar radiation (sunlight) at the ocean surface

Define UVRDefine UVR = ultraviolet radiation (280- 400 nm), = ultraviolet radiation (280- 400 nm), with flux with flux QQ = = QQUVRUVR

UVR UVR < 295 nm do not the ocean surface; < 300 nm do not penetrate in oceans/lakes< 295 nm do not the ocean surface; < 300 nm do not penetrate in oceans/lakesEnvironmentally Relevant UVREnvironmentally Relevant UVR = (300-400 nm)= = (300-400 nm)= most energetic light reaching earthmost energetic light reaching earthUVR excitation energyUVR excitation energy breaks chemical bonds.. Esp. those of DNA, RNA & proteins breaks chemical bonds.. Esp. those of DNA, RNA & proteins

Light in water:Light in water: PURE WATER ABSORPTION & ATTENUATION ARE OPTICAL CONSTANTSPURE WATER ABSORPTION & ATTENUATION ARE OPTICAL CONSTANTS

MaximumMaximum depth penetration (in depth penetration (in meters) of different wavelengths meters) of different wavelengths (colors) of Q(colors) of QPARPAR into into clear watersclear waters

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Attenuation of UVR and PAR by pure water

Note this is a log Plot of attenuation rate

Attenuated Light, Iz = QIz = QPARPARzz

Incident Light, Io = QIo = QPARPARoo

Absorbed + Scattered Light

See readings for review and added details

Absorption due to Absorption due to colored DOM = cDOMcolored DOM = cDOM

UnderWater Light (UWL) is absorbed by WATER, cDOM & phytos

Phytos AbsorptionShort wavelength UV and violet/blue light are in Short wavelength UV and violet/blue light are in fact fact scatteredscattered about about twicetwice as strongly as red light. as strongly as red light. For wavelengths in the visible light range, For wavelengths in the visible light range, selective scattering causes us to see the blue color. selective scattering causes us to see the blue color. Scattering is why light below a few meters is said Scattering is why light below a few meters is said to be ‘to be ‘diffusediffuse’.. Bouncing in all directions. ’.. Bouncing in all directions.

Phytoplankton pigmentation evolved to absorb different types of UWL fields.Phytoplankton pigmentation evolved to absorb different types of UWL fields.

(cDOM)

(particles)

Spectral properties of UWLSpectral properties of UWL vary widely vary widely

Case I: Open OceanCase I: Open Ocean Case II: Coastal and Inland watersCase II: Coastal and Inland waters

In coastal waters the depth of the euphotic zone decreases and ocean color shifts from blue to green as phytoplankton biomass, cDOM and particle load

increases.

Euphotic zoneEuphotic zone = = depths where phytoplankton grow ~depths where phytoplankton grow ~1% of surface Io1% of surface Io

• Over the dayOver the day the depth of the euphotic zone deepens and shallow as sun rises and sets.the depth of the euphotic zone deepens and shallow as sun rises and sets.• For intercomparison purposesFor intercomparison purposes, UWL field properties are reported as measurements , UWL field properties are reported as measurements made made atat solar noon solar noon unless otherwise specified. unless otherwise specified. • Why Why would scientists take care to also report the time of year & the sky conditions when would scientists take care to also report the time of year & the sky conditions when

presenting UWL data?presenting UWL data?

Calculating Attenuation Coefficients for “white light” Qpar Calculating Attenuation Coefficients for “white light” Qpar

Beer-Lambert lawBeer-Lambert law describes the describes the exponential decrease in irradiance with depthexponential decrease in irradiance with depth

IIzz = I = I00.e.e--kkdd.z.z

• • IIzz is irradiance at a given depth is irradiance at a given depth

• • II00 is irradiance at the surface is irradiance at the surface

• • kkdd is the diffuse is the diffuse attenuation coefficientattenuation coefficient

• • zz is depth in meters. is depth in meters.

Kd Kd for for QQPARPAR indicate transparency but do indicate transparency but do notnot indicate possible color indicate possible color difference in UWL. difference in UWL.

To recognize color differences, would need to measure spectral attenuation coefficients for To recognize color differences, would need to measure spectral attenuation coefficients for Kd (Kd (),), looking at narrow bandwidths of visible spectrum at a time, e.g. looking at narrow bandwidths of visible spectrum at a time, e.g. QPAR(QPAR())

See Fig. 10-8 in readingsSee Fig. 10-8 in readings

In the water column, light (e.g. QIn the water column, light (e.g. QPARPAR) ) is absorbed exponentially with deptis absorbed exponentially with depthh

When plotted as depth vs log % surface When plotted as depth vs log % surface irradiance (Io), the line is straightirradiance (Io), the line is straight

IoIo

Iz1% Io Absorption of UVR and PAR by pure water

IoE 184 - The Basics of Satellite Oceanography. 6. Oceanographic Applications: Ocean color observations

Examples of Water Color ImagesExamples of Water Color Images

This true color satellite image of SW coast of Florida shows patch of intense phytoplankton biomass (bloom).

Case II waters

This aerial photograph the spatial variability high concentrations of phytoplankton and suspended matter change water color in the coastal zone .

Example is typical of Santa Barbara Channel after major storm events.

Study Aid: Study Aid: after completing your readings on Light Properties, consider the following image of after completing your readings on Light Properties, consider the following image of sunlight on a story day shining down on a shallow sandy water column.sunlight on a story day shining down on a shallow sandy water column.

1.1. What might account for What might account for the difference in color at A & B?the difference in color at A & B?

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

note the 2 arrowsnote the 2 arrows

AA

BB

44. What color is pure water? What makes it whiter?, . What color is pure water? What makes it whiter?, greener?, redder? Do these waters appear to have abundant greener?, redder? Do these waters appear to have abundant phytoplankton biomass? Do you think there is much phytoplankton biomass? Do you think there is much cDOM? Why or why not?cDOM? Why or why not?

2.2. How might the following play a How might the following play a role in explaining the difference?role in explaining the difference?

sandy bottom,sandy bottom,sun with broken cloudssun with broken cloudsdepthdepth

33. What is the equation that . What is the equation that describes the 3 spectral describes the 3 spectral components that account for the components that account for the spectral attenuation of light in spectral attenuation of light in natural waters?natural waters?

5. What color is your favoriteswimming place? Why?

Study Aid: 1. Which side of this lake suffers from eutrophication (nutrient pollution)?

2. How can you tell? Color change is 2. How can you tell? Color change is obvious but what does it mean? obvious but what does it mean?

3. If you were to see this event with an 3. If you were to see this event with an uninformed friend, what would you uninformed friend, what would you tell them to explain this remarkable tell them to explain this remarkable site?site?

Consider how nutrients affect Consider how nutrients affect phytoplankton growth and absorption; phytoplankton growth and absorption; how biomass can clump and form how biomass can clump and form particles that scatter light; how cDOM particles that scatter light; how cDOM might be come into play and affect might be come into play and affect spectral light attenuation (color) in the spectral light attenuation (color) in the water column.water column.

Study Aid: Reading of Chapter 10 on “Light”

1. How does light regulate aquatic ecology?1. How does light regulate aquatic ecology? (eg. photosynthesis, vision, heat budgets, etc(eg. photosynthesis, vision, heat budgets, etc))

consider making a list and be as specific as you can; refer and revise this list as other lectures consider making a list and be as specific as you can; refer and revise this list as other lectures and readings are completed.and readings are completed.

Pay close attention to this chapter as info is considered fundamental; consider forming study groups early.Pay close attention to this chapter as info is considered fundamental; consider forming study groups early.

2. Study Fig. 10.1 closely (seasonal changes in solar light as a function of latitude) & thoughtfully2. Study Fig. 10.1 closely (seasonal changes in solar light as a function of latitude) & thoughtfullyNote solar radiation highest in N. Hemisphere summer & S. Hemisphere “austral summer”, the later Note solar radiation highest in N. Hemisphere summer & S. Hemisphere “austral summer”, the later occurring at time of N. Hemisphere winter; what happens near the equator? Since unused radiation occurring at time of N. Hemisphere winter; what happens near the equator? Since unused radiation dissipates to heat, this figure also shows how the earth is heated by the sun during different seasons. dissipates to heat, this figure also shows how the earth is heated by the sun during different seasons. Consider this uneven heating when upcoming lectures discuss the forces that drive winds and, in turn, Consider this uneven heating when upcoming lectures discuss the forces that drive winds and, in turn, how wind drives currents. For a review of major currents, see online reading assignment for week 1. how wind drives currents. For a review of major currents, see online reading assignment for week 1. Bonus: how might a change this heat distribution (eg. uneven global warming) affect dessert Bonus: how might a change this heat distribution (eg. uneven global warming) affect dessert formation, precipitation, winds, currents? Clearly a case where biology (us) change atmospheric formation, precipitation, winds, currents? Clearly a case where biology (us) change atmospheric chemistry, resulting in heat budget changes that affect fundamental physics of the planet and, in turn, chemistry, resulting in heat budget changes that affect fundamental physics of the planet and, in turn, have huge biological effects.have huge biological effects.

3. Learn to recognize names, wavelengths & units of measure of light color and intensity 3. Learn to recognize names, wavelengths & units of measure of light color and intensity the better you know, the easier your understanding of light attenuation, absorption, utilization, etc.the better you know, the easier your understanding of light attenuation, absorption, utilization, etc.Don’t need to know ConversionsDon’t need to know Conversions between units but understand that different units do exist between units but understand that different units do exist

4. Generalities of how light is measured with different instruments should be understood.4. Generalities of how light is measured with different instruments should be understood.if you are taking the accompanying lab to this course, a deeper understanding of these methodologiesif you are taking the accompanying lab to this course, a deeper understanding of these methodologies(as described in the reading) should help you in your laboratory/field studies. (as described in the reading) should help you in your laboratory/field studies.

5. Eqs. 10.1 and 10.2 are fundamental equations from which other useful equations are derived.5. Eqs. 10.1 and 10.2 are fundamental equations from which other useful equations are derived.Why is blue light more energetic than red light? Of UV radiation, PAR and IR, which has most/least E?Why is blue light more energetic than red light? Of UV radiation, PAR and IR, which has most/least E?What is light attenuation in the water column? Why does it get dark at depth? Where does theWhat is light attenuation in the water column? Why does it get dark at depth? Where does the attenuated light energy go?attenuated light energy go?

Study Aid: Self Test of Chapter 10 on “Light”

1. What is the lowest wavelength of light entering the water column? Is this wavelength in the UV, PAR or IR?

2. What units are used when measuring the ENERGY of incoming solar radiation?What units are used when measuring the NUMBER of PHOTONS (quanta) of incoming radiation?

3. Some light instruments (photometers) measure the INTENSITY (photon flux) of all PAR light (e.g. “white light”) at once; others (spectroradiometers) measure the INTENSITY of narrow wavebands of PAR light (e.g. “spectralLight). How does the attenuation of ‘white’ PAR and spectral PAR compare as a function of depth? ThoughtQuestion: What are the possible differences in the uses of ‘white light’ and ‘spectral’ data in studies of bio-optics of phytoplankton ecology?

4. What percent of total sunlight reaching the ocean surface is PAR? What percent is UV radiation? IR?

5. Clouds/fog can reduce incident radiation (Io, sunlight reaching earth surface) by how much? What about effects of natural local topography?.. Eg. mountains, trees, ice (with and without air bubbles), snow, sand? What about unnatural effects, e.g. buildings, pavement, windows, greenhouses, oil slicks? What others can you think of? Look around as you walk campus or go to the beach and ask yourself why the light is variable in different places and how frequently does it change.. Minutes, hours (dawn, noon, dusk), daily, seasonally, yearly.

6. Light scatters differently at different wavelengths. Of red vs blue vs UV radiation, which scatters more? What is the formula that calculates by how much a specific wavelength of light will scatter? Which of the variables in 5) above tend to scatter light rather than absorb it? Eg. Under cloudy skies are incoming photons absorbed and/or scattered?

7. What color of light penetrates deepest in oligotrophic water columns? As more DOM is present, what happens both to the depth of penetration and the color of light that penetrates deepest? Why? What is the effect of particles? Of phytoplankton (and their pigments)?

8. How do the light penetration (transparency) of lakes, coastal oceans and oligotrophic central gyres compare?