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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)
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Reminder: Midterm 1 is one week from today on Friday February 1st
Extended office hours next week for Professor Prézelin
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
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,
= 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
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
Ps rates exceed those of Hydrilla?
One mole of hv = one Einstein of hv = one Ein
= 6.02 x 10 23 molecules
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
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
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.
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.
The abundance, composition and photosynthetic capabilities of phytoplankton communities vary widely across the frontal boundaries in SBC and extending seaward
Surface Chl /vol
Surface water temperature, SST
From your reading P et al 1987
Note differences in pigment concentration range for cold, front, warm waters
Nano- and pico-phytoplankton feed the microbial loop
Comment on phytoplankton size and food chain dynamics