Reminder: Midterm 1 is one week from today on Friday February 1st

1. Big!! Reminder: Midterm 1 is one week from today on Friday February 1st • Midterm 1 is 15% of your final grade • It covers all lectures through Monday January 28th • It covers all reading assigned for weeks 1-4 (up to and including “Ecology of Water Columns) • It will be short answer comprehensive based upon understanding of content, not problem solving. Extended office hours next week for Professor Prézelin Monday 11AM-1PM Wednesday 10AM-NOON Phyto Story: The monster diatom Coscinodiscus wailessi Common Indo-Pacific Ocean species, invaded English Channelin 1977 when likely introduced by ballast waters of ships or exotic shellfish (oysters) transplanted to European coastal mariculture facilities. Invasion spread 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 mucilage, affecting gas & nutrient exchange at sediment/water column interface. Effects on commercial interests: Fishing trawls become clogged or broken by heavy grey slime. Regular sized diatoms

2. Light-inhibited PP and m Light saturated PP and m at ~60 % Pmax, cell division rates become maximal, eg. m =mmax Light limited PP but Light saturated m Light limited PP & Growth rates (m ) No PP, No growth, possible Senescence (decay, death, ), formation Resting stages, Pmax

3. slopes b, beta a, alpha Ik It a b = Ps rate/ PFD Ik = Pmax/alpha It = Pmax/beta Parameters of Photosynthesis-Irradiance curves without photoinhibition,Ps = Pmax . tanh (I/Ik) with photoinhibition,Ps = [Pmax . tanh (I/Ik)] minus [ eq. describing shape of beta] Beta varies from a linear to exponential decline

4. Comparison of P-I curves for different algae under different growth conditions P-I relationships are a “signature” of the photo-physiological state of the phytoplankton cell, population, and mixed community • Which has the highest Pmax? • Which has the highest alpha? • Which has the lowest Ik? • At 50 mEin m-2 s-1, which has the greatest rates of Ps? • At 200 mEin m-2 s-1, which has the greatest rates of Ps? • Above what QPAR does Ceratophylum Ps rates exceed those of Hydrilla? One mole of hv = one Einstein of hv = one Ein = 6.02 x 10 23 molecules

5. Chl biomass as f(x) of depth (z) hv PP Can predict in situ Ps rates if Chl distribution or QPAR profiles change 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 • NB: this FW experiment measured O2 changes in bottles, which is why respiration values are reported • marine PP studies use C14 uptake bottles similarly deployed; do not get respiration rates and PP measurement is something between NPP and GPP • Problem with C14 bottles, some of uptake C14 gets respired during long incubations & bacteria accumulate & community biology changes Photoinhibition and/or photorespiration Light saturated photosynthesis, Pmax Light-limited (alpha portion of P-I curve) IF water column was well mixed, Chl was constant as a function of depth, & just one P-I Curve could describe phytoplankton photophysiology throughout the water column, then the depth-dependent PP could be viewed as

6. P-I sampling strategies for determination of in situ rates of primary productivity, PP For determinations of instantaneous in situ PP at one place (z) and time (t) 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 although the accuracy would depend on the P-I response remaining constant i.e. Daily rates of PP at same location (PP)z, expressed as mg C/m3/day or mgC/mg Chl/day i.e. Integrated water column PP (SPP)t, expressed as mg C/m2/hr or mgC/mg Chl/hr) i.e. Daily integrated water column PP SPP, expressed as mg C/m2/day or mgC/mg Chl/day) Accuracy increases with knowledge of how P-I, Chl a, and Qpar vary as f(x) of t,z.

7. Lecture 10: FYI for readings on waters in or near the Santa Barbara Channel (SBC) SBC resides in northern portion of the Southern California Bight (not Bite) California Current (CC): cool, nutrient rich, flows south along the outer edge of the Continental Shelf (1000 m). Southern California CounterCurrent (SCCC):warmer, lower nutrient waters of the northerly flow of the hugs the coastline until encountering the SBC which block much of the flow and divert it seward to mix with the CC. Episodic upwelling north of Pt. Conception produces cold, nutrient rich water which mixes with the CC waterforming sharpfrontal boundaries as it encounters the SCCC. Subtropical oligotrophic waters flow north along the coast in summer months, more so in El Nino years Marked gradients in the physical, chemical, biological and optical properties of the upper water column (0 to 160 m) are observed across the SBC coastal region. SST

8. The abundance, composition and photosynthetic capabilities of phytoplankton communities vary widely across the frontal boundaries in SBC and extending seaward Surface Pmax/vol Surface Chl /vol Surface water temperature, SST From your reading P et al 1987

9. SBC, fig. From P et al. 1987. Note differences in pigment concentration range for cold, front, warm waters

10. expressed as mg C/m3/hr Synechococcus Diatom-dominated ??

11. Net phytoplankton feed the linear food via larger zooplankton Nano- and pico-phytoplankton feed the microbial loop Comment on phytoplankton size and food chain dynamics