Wayne Slade Ocean Optics Summer 2004 Dock Observatory – Estimating Total Suspended Matter from Particle Backscatter Wayne Slade Ocean Optics Summer 2004

Total Suspended Matter Comprised of sediments, dead or decaying plant and animal bits, and still living particles Basic indicator of water turbidity and “water quality” Light penetration affects photosynthesis Makes fish unhappy (gills) Makes people unhappy (aesthetics, water supply) More suspended material  more scattering (and maybe absorption) Therefore, optical methods offer potential for use as proxies for TSM Goal of our (Mike & Wayne) project  Establish a functional relationship between hard to measure TSM and plentiful dock observations of bbp(700)

Optical Proxies for TSM cp(630) (m-1) Bergmann et al. 2004 In situ TSM is time consuming  optical methods for “continuous” observation Many relationships between optical quantities and TSM are available Examples Bergmann et al. 2004 Babin et al. 2003 L&O bp = (bp*) TSM Mass-specific particle scatter (bp*) ~ 0.5-1.0 m2g-1 Babin et al. 2003

After Week 1 We looked at relating TSM with IOP… With the data collected so far, a relationship is not apparent Note that results are typically given log-log Relationship between TSM and bbp was not clearly visible… Revisit the problem with more dock sampling!

(1) Dock Measured bbp BB2F measures optical backscatter at two wavelengths (λ = blue 470nm, red 700nm) and chl fluorescence, θ = 117° β(117°,λ) = scale(λ)*DN(λ) + offset(λ) bbp (λ) = 2π [β (117°,λ) - βw(117°,λ)] Xp(117°) bbp values seem odd: Dock samples for bp(700) were ~1-2 m-1 bbp/bp ~ 10% ??

(2) Bottle Samples for TSM Routine (~daily) sampling Many sources of error and strife! SALTS! Sometimes not enough dried filters! ~8 samples (3 reps/sample)

(3) Matching Dock bbp(700) to TSM Typical dock sample time was 1300 Sample median values of dock TSM were matched with observatory bbp Observatory bbp are median of values from 1230 to 1330 High variability in both TSM and bbp is present…

(4) Linear Regression Results TSM [g m-3] = (48.3) bbp(700) + 3.45 TSM [g m-3] = (71.4) bbp(700) bbp(700) [m-1] = (0.012) TSM More dynamic range would be nice! We find (bbp*) ~ 0.01 m2 g-1 Reasonable compared to Babin? (bp*)~0.5-1.0 m2g-1 (bbp*) = Bp * (bp*) (~0.01 m2g-1) = (~0.01)(1.0 m2g-1) ☺

Observatory TSM Product

Discussion Results show link a between bbp(700) and TSM Need more dynamic range of in situ samples to show that the model is valid for all bbp observed at dock observatory 2 samples /day, at different times of day, across full tidal range Higher quality TSM would be nice (i.e. consistent lab technique, proper rinsing protocol) Should regression of TSM and bbp be forced to pass through origin?