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

Fig. 8q-1 some of the major surface ocean currents. Reminder: Week 1 online reading assignment www.physicalgeography.net/fundamentals/chapter8.html OPTIONAL Study Aid for this reading will be posted on lab website. Where are the cold currents? the warm currents?

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

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  1. Fig. 8q-1 some of the major surface ocean currents Reminder: Week 1 online reading assignment\ www.physicalgeography.net/fundamentals/chapter8.html OPTIONAL Study Aid for this reading will be posted on lab website • 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)

  2. Light in water: lecture slides plus take-home study aid slides Tropical species show great shapes Homework: Read On-line web pages (links therein are optional) “What is hydrologic optics”http://www.serc.si.edu/labs/phytoplankton/primer/hydrops.jsp“The Color of the Ocean” http://science.hq.nasa.gov/oceans/living/color.html Homework: Chapter 10 in your reader: Light

  3. Review: Light travels as waves of energy (hv), Light energy is quantified in Watts or Joules, terms used in heat budgets 1. Waves of light have different wavelengths (l), expressed as nanometers (nm) or Angstroms (A) 1 nm = 10 A Photosynthetically Available Radiation = PAR 2. Purple and blue light waves have short l. Red light has a longer l 3. Short l carry more energy than Long l. 4. When the l of light matches the distance of spacing in a chemical bond, then the energy (hv) of the light is transferred to the energy of the chemical =Absorption 5. All molecules absorb light energy.. Most dissipate the absorbed energy as heat e.g. H2O, CO2

  4. Light also acts like a Stream of Particles, called Photons or Quanta (hv). Most important to study of biology (photosynthesis, photochemistry, bio-optics) of chemical bonds Conceptualization of a photon That “extra” resonance energy can transferred between chemicals (e.g. pigments) in packets called excitons. Energy transduction Absorbed photon increases the resonance energy of the chemical , pushing electron to higher excited state. Because of their dual nature as particles and waves, photons are often shown as squiggly lines. • Light is absorbed in packets of energy • Each packet = 1 photon =1 quantum • Energy content of a photon varies inversely with wavelength • Measurements of rate of incoming photons are usually expressed in units of moles of photons/area/time = Photon Density Flux (PDF) = Irradiance (I) Light Absorption & Resonance Energy Transduction are 1st steps in Photosynthesis

  5. Solar radiation (sunlight) at the ocean surface PAR(400-700 nm) = photosynthetically available radiation = ls absorbed by photosynthetics pigments Sum of all ‘colors’ of light energies of PAR = white light PAR, with flux Q = QPAR For a narrow waveband of PAR (e.g. blue light) = spectral PAR, with flux Q = QPAR(l) Define UVR = ultraviolet radiation (280- 400 nm), with flux Q = QUVR UVR < 295 nm do not the ocean surface; < 300 nm do not penetrate in oceans/lakes Environmentally Relevant UVR = (300-400 nm)= most energetic light reaching earth UVR excitation energy breaks chemical bonds.. Esp. those of DNA, RNA & proteins

  6. Light in water:PURE WATER ABSORPTION & ATTENUATION ARE OPTICAL CONSTANTS Note this is a log Plot of attenuation rate Maximum depth penetration (in meters) of different wavelengths (colors) of QPAR into clear waters Attenuation of UVR and PAR by pure water

  7. UnderWater Light (UWL) is absorbed by WATER, cDOM & phytos Incident Light, Io = QPARo Absorbed + Scattered Light Absorption due to colored DOM = cDOM Attenuated Light, Iz = QPARz Phytos Absorption Short wavelength UV and violet/blue light are in fact scattered about twice as strongly as red light. For wavelengths in the visible light range, selective scattering causes us to see the blue color. Scattering is why light below a few meters is said to be ‘diffuse’.. Bouncing in all directions. See readings for review and added details

  8. Phytoplankton pigmentation evolved to absorb different types of UWL fields. (cDOM) (particles)

  9. Case II: Coastal and Inland waters Case I: Open Ocean 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. Spectral properties of UWL vary widely Euphotic zone = depths where phytoplankton grow ~1% of surface Io • Over the daythe depth of the euphotic zone deepens and shallow as sun rises and sets. • For intercomparison purposes, UWL field properties are reported as measurements made at solar noon unless otherwise specified. • Why would scientists take care to also report the time of year & the sky conditions when presenting UWL data?

  10. Calculating Attenuation Coefficients for “white light” Qpar In the water column, light (e.g. QPAR) is absorbed exponentially with depth Io Io Iz Absorption of UVR and PAR by pure water 1% Io When plotted as depth vs log % surface irradiance (Io), the line is straight Beer-Lambert law describes the exponential decrease in irradiance with depth Iz = I0.e-kd.z • Iz is irradiance at a given depth • I0 is irradiance at the surface • kd is the diffuse attenuation coefficient • z is depth in meters. See Fig. 10-8 in readings Kd for QPAR indicate transparency but do not indicate possible colordifference in UWL. To recognize color differences, would need to measure spectral attenuation coefficients for Kd (l), looking at narrow bandwidths of visible spectrum at a time, e.g. QPAR(l)

  11. Examples of Water Color Images 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. Case II waters This true color satellite image of SW coast of Florida shows patch of intense phytoplankton biomass (bloom). IoE 184 - The Basics of Satellite Oceanography. 6. Oceanographic Applications: Ocean color observations

  12. Study Aid: 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. A note the 2 arrows B 1. What might account for the difference in color at A & B? 2. How might the following play a role in explaining the difference? sandy bottom, sun with broken clouds depth 3. What is the equation that describes the 3 spectral components that account for the spectral attenuation of light in natural waters? 5. What color is your favorite swimming place? Why? 4. What color is pure water? What makes it whiter?, greener?, redder? Do these waters appear to have abundant phytoplankton biomass? Do you think there is much cDOM? Why or why not?

  13. Study Aid: 1. Which side of this lake suffers from eutrophication (nutrient pollution)? 2. How can you tell? Color change is obvious but what does it mean? 3. If you were to see this event with an uninformed friend, what would you tell them to explain this remarkable site? Consider how nutrients affect phytoplankton growth and absorption; how biomass can clump and form particles that scatter light; how cDOM might be come into play and affect spectral light attenuation (color) in the water column.

  14. Study Aid: Reading of Chapter 10 on “Light” Pay close attention to this chapter as info is considered fundamental; consider forming study groups early. 1. How does light regulate aquatic ecology?(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 and readings are completed. 2. Study Fig. 10.1 closely (seasonal changes in solar light as a function of latitude) & thoughtfully 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 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, 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 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, have huge biological effects. 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. Don’t need to know Conversions between units but understand that different units do exist 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 methodologies (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. 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 the attenuated light energy go?

  15. 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. “spectral Light). How does the attenuation of ‘white’ PAR and spectral PAR compare as a function of depth? Thought Question: 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?

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