Lectures 8-9

Lectures 8-9 - Reminder: Midterm 1 is one week from today...

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Unformatted text preview: Reminder: Midterm 1 is one week from today on Friday February 1st Reminder: • Midterm 1 is 15% of your final grade Midterm • It covers all lectures through Monday January 28th It • It covers all reading assigned for weeks 1-4 (up to and including “Ecology of Water Columns) It • It will be short answer comprehensive based upon understanding of content, not problem solving. It Extended office hours next week for Professor Prézelin Monday 11AM-1PM Wednesday 10AM-NOON Phyto Story: The monster diatom Phyto Common Indo-Pacific Ocean species, invaded English Channel in 1977 when likely introduced by ballast waters of ships or exotic shellfish (oysters) transplanted to European coastal mariculture facilities. Invasion spread Big!! rapidly to Atlantic coast of France by 1978 & Norway by 1979. Effects on the environment: They bloom & produce copious mucilage that glue particles in water together & sink to blanket the seabed in particulate mucilage, affecting gas & nutrient exchange at sediment/water column interface. Regular sized diatoms Fucoxanthin marker pigment Effects on commercial interests: Fishing trawls Effects become clogged or broken by heavy grey slime. Light-inhibited PP and µ Light-inhibited Light saturated PP Pmax and µ at ~60 % Pmax, cell division rates become maximal, eg. µ =µ max Light limited PP but Light saturated µ Light Light limited PP & Growth rates (µ ) Pmax No PP, No growth, possible Senescence No (decay, death, ), formation Resting stages, Parameters of Photosynthesis-Irradiance curves Photosynthetic potential slopes α , alpha alpha β , beta beta I I t Chl-specific α = relative quantum yield Chl-specific α β = Ps rate/ PFD = Pmax/alpha Pmax/alpha t I Indices of Photoadaptation Indices Photoinhibition I without photoinhibition, Ps = Pmax tanh (I/I ) . = Pmax/beta Pmax/beta with photoinhibition, Ps = [Pmax tanh (I/I )] k describing )] minus [ eq. describing shape of beta] . k Beta varies from a linear to exponential decline Beta Comparison of P-I curves for different algae under different growth conditions Comparison P-I relationships are a “signature” of the P-I photo-physiological state of the phytoplankton cell, population, and mixed community • Which has the highest Pmax? Which • Which has the highest alpha? Which • Which has the lowest Ik? Which • At 50 µ Ein m-2 s-1, which has the greatest which rates of Ps? rates • At 200 µ Ein m-2 s-1, which has the greatest which rates of Ps? rates • Above what QPAR does Ceratophylum Above Ceratophylum Ps rates exceed those of Hydrilla? Ps Hydrilla One mole of hv = one Einstein of hv One = one Ein one P-I sampling strategies for determination of in situ rates of primary productivity, PP P-I For determinations of instantaneous in situ PP at one place (z) and time (t) For instantaneous PPz,t, expressed as mg C/m3/hr or mgC/mg Chl/hr need to measure (Qpar)z,t and (Chl a)z,t and experimentally determine (P-I)z,t, using (P-I)z,t, could estimate PP for other conditions (Qpar)z,t and (Chl a)z,t using although the accuracy would depend on the P-I response remaining constant the i.e. Daily rates of PP at same location Daily (PP)z, expressed as mg C/m3/day or mgC/mg Chl/day i.e. Integrated water column PP Integrated (Σ PP)t, expressed as mg C/m2/hr or mgC/mg Chl/hr) PP)t, i.e. Daily integrated water column PP Daily Σ PP, expressed as mg C/m2/day or mgC/mg Chl/day) PP Accuracy increases with knowledge of how P-I, Chl a, and Qpar vary as f(x) of t,z. Case Study: Santa Barbara Channel (SBC) Case Pt. Conception, at the western boundary of Pt. the Santa Barbara Channel (SBC), is a (SBC) is major biogeographic and coastal oceanic boundary that strongly influences the physical and biological dynamics of the marine ecosystems within the Channel. SBC is considered a transition zone between cold water ecosystems to the north of Pt. Conception and the warm water ecosystems of Southern California. water This is one reason why there is a rich This diversity of animal and plant life within the SBC. A most excellent place for research!! SBC. Before SBC, brief summary of various bio-optical approaches to estimate in situ PPz,t Before 1. Optical measurements of QPAR(λ )z,t, measured or estimated aph(λ )z,t, assumed or estimated measured assumed operational φ (λ ) z,t. FULLY SPECTRAL APPROACH operational FULLY PP z,t = Σ PAR( QPAR(λ )z,t x aph(λ ) z,t x φ (λ ) z,t ) )z,t z,t z,t PP z,t aph( Field measurements will also include vertical profiles of [Chl a] for biomass estimates. If accessory pigments also measured, could tell how phytoplankton community composition varied in space and time. If temperature or density profiles measured, could tell how PP was distributed with respect to water mass type and potential vertical mixing. If nutrients were measured, could tell if phytoplankton if productivity was likely to be nutrient-limited or nutrient-repleted nutrient-repleted 2. Gas Exchange Experiments ( hv-dependent rates of O2 evolution or inorganic carbon uptake) 2. or a) for O2 gas exchange, bottle experiments in situ or O2 electrode experiments under for bottle in simulated in situ (sis) conditions. simulated b) for radiolabeled H14CO3/14CO2 uptake experiments, bottle experiments in situ or b) radiolabeled CO2 in photosynthetron experiments under sis conditions. photosynthetron In situ studies give rates of PPz.t whether or not QPAR is known while sis studies of PP require In knowledge of in situ depth profiles of QPAR and [Chl] [Chl] In situ bottle measurements provide estimtew ofin situ rates of PP for one t,z but has no predictive value P-I approach allows for estimating and predicting in situ PP for any t,z where light &Chl are known any Chl biomass as f(x) of depth (z) Photoinhibition and/or Photoinhibition photorespiration photorespiration • NB: this FW experiment NB: measured O2 changes in bottles, which is why respiration values are reported reported • marine PP studies use C14 uptake bottles similarly deployed; do not get respiration rates and PP measurement is something between NPP and GPP between • Problem with C14 bottles, some of uptake C14 gets respired during long incubations & bacteria accumulate & community biology changes biology hv PP Light saturated Light photosynthesis, Pmax photosynthesis, Light-limited (alpha Light-limited portion of P-I curve) portion Can predict in situ Ps rates if IF water column was well mixed, Chl was constant as a IF function of depth, & just one P-I Curve could describe phytoplankton photophysiology throughout the water Chl distribution or Q profiles change PAR column, then the depth-dependent PP could be viewed as ...
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