Mike Twardowski

WET Labs, Inc.

Narragansett, RI

Emerging sensor technologies for linking optical, biogeochemical,

biological and ecological properties

www.wetlabs.comwww.wetlabs.com

www.wetlabs.comwww.wetlabs.com

Science Challenges

• What are the sources of backscattering?

• How can we get more than chl?

• Why do closure attempts usually fall short

of expectations?

• At what temporal/spatial scales do optical

properties need to be resolved in

coastal/inland waters for algorithm

development/validation?

Technical Challenges

• VSF measurements

• Polarized scattering

• Better characterization of optically

relevant particles

• Better analytical models for particle

scattering

• Better assessments of measurement

biases and uncertainties

• Spatial and temporal sampling at

relevant scales

• Measurements in very high turbidity

MASCOT: VSF (10:10:170 deg; 658 nm) ECOVSF: VSF (60 to 170 deg; multi- ) ECOBB3: VSF (124 deg; 470, 532, 650 nm) LISST: VSF (0.08 to 13 deg; 650 nm) AC9: absorption and attenuation (9 ) SBE49 CTD

VSF Measurement Considerations

5+ orders of magnitude variation in intensity from the near-forward to backward in single VSF

several orders of magnitude natural dynamic range in intensity at any single angle

rapid temporal variability in particle fields in surface waters

rejecting ambient light is challenging at surface, particularly for low scattering signals in the backward

calibration without absolute “standard”

Phase functions from Scripps Pier

1 – background

2 – mineral laden

3 – bubble laden

90 min record

Twardowski et al. 2012

inversion

Minerals

Bubbles

Colloids

Phase functions of randomly oriented asymmetric

hexahedra (mineral-mimicking)

monodispersions with radius 0.01 to 162 um, log spaced

Discrete Dipole

Approx

(DDA)

and

Improved

Geometrical

Optics Model

(IGOM)

Twardowski et al. 2012

Bubbles from Inversion

single bubble theory

• First time the theoretical bubble VSFs

have been verified with in-situ

measurements

• Currently the only method of resolving

small bubbles in seawater

• Backscattering is higher with coating

Bubbles resolved with optics and acoustics

23 and 10 kHz

acoustic signal

from bubbles sizes

143 and 332 m

large bubble

size class from

inversion

Outline Instrumentation Deployment Modes Results I Results II

200 600 1000 1400 1800 2200

Time (s)

4

3

2.5

Bu

bb

le c

on

ce

ntr

atio

n

(/m

L)

Pa

rtic

le c

on

ce

ntr

ation

(/m

L)

(c)

200 600 1000 1400 1800 2200

Bu

bb

le c

on

ce

ntr

atio

n

(/m

L)

60

10

1

100

11

200 600 1000 1400 1800

Bubbles in a Ship wake (Comparison among instruments)

HOLOSUB: Segmentation & Edge detection Particle concentration [8.5 µm, 250 µm]

Acoustic resonator: Bubble size concentration [13 µm, 250 µm]

VSF inversion: Bubble concentration

Log-normal population,

Mode: 10 µm, S.D.: 1.1 µm

Twardowski, Talapatra, Czerski, Vagle

Polarized scattering measurements

0 50 100 150

-0.2

0

0.2

0.4

0.6

0.8

-S12/S11

de

gre

e o

f lin

ea

r p

ola

riza

tio

n (

-S1

2/S

11

)

1m binned data

C

angledegre

e o

f lin

ea

r

pola

rizatio

n

ideal

Rayleigh

-S12

S11

B

angle

Santa Barbara

Channel

Sept, 2008

90 m

particle

max

10-4

10-3

10-2

10-1

100

-120

-100

-80

-60

-40

-20

0

beta(theta)

de

pth

(m

)

10°

20° 30°

A

depth

(m

)

(m-1 sr-1)

0 50 100 150

-0.2

0

0.2

0.4

0.6

0.8

-S12/S11

de

gre

e o

f lin

ea

r p

ola

riza

tio

n (

-S1

2/S

11

)

1m binned data

C

angledegre

e o

f lin

ea

r

pola

rizatio

n

ideal

Rayleigh

-S12

S11

B

angle

-S12

S11

B

angle

Santa Barbara

Channel

Sept, 2008

Santa Barbara

Channel

Sept, 2008

90 m

particle

max

10-4

10-3

10-2

10-1

100

-120

-100

-80

-60

-40

-20

0

beta(theta)

de

pth

(m

)

10°

20° 30°

A

depth

(m

)

(m-1 sr-1)

10-4

10-3

10-2

10-1

100

-120

-100

-80

-60

-40

-20

0

beta(theta)

de

pth

(m

)

10°

20° 30°

A

depth

(m

)

(m-1 sr-1)

Observed polarization during periods of bubble injection

in the near-surface

0 20 40 60 80 100 120 140 160 180

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

S12/S

11

angle

Lorenz-Mie Theory

measurements

Multi-angle airborne polarimeter

Chowdhary et al. 2012

62 m

altitude

410 nm 550 nm

Closure assessments usually don’t work…

• For measurements: Absorption is typically largest source

of uncertainty (scattering error and flow cell required)

– McKee-Piskozub making progress on scattering error

• Disruption of aggregates (e.g., Boss et al. 2009)

• Hyperspectral backscattering

• Are the assumptions used in modeling and

measurements valid?

– Randomly oriented particles…?

Need better characterization of

undisturbed optically relevant particles

0

0.2

0.4

0.6

0.8

1

1.2

0 20 40 60 80 100 120 140 160 180 200

Wa

Scattering Angle (deg)

r=1.0

r=0.999

r=0.998

r=0.995

r=0.990

r=0.985

r=0.980

r=0.970

r=0.960

r=0.950

Modeled weighting functions for reflective tube absorption scattering error

McKee and Piskozub, unpub.

Marcos et al. 2011

Nonrandom particle distributions completely change our

interpretation of radiative transfer

Adding shear to a

culture of E coli

increased

backscattering 30%

, ’ ’

In situ holographic microscope: HOLOCAM

3-D imaging of particles from

<1 to 1000 µm size range in

undisturbed, in-situ volumes

WET Labs HOLOCAM JHU prototype

• size and shape parameters of particles

characterized in an undisturbed remote

volume in every image

• orientation of all particles

• 3-D relative location of all particles

• particle tracking

• possibly some particle density

characterization also SPM

• shear and turbulent dissipation rates

Malkiel

et al.

(2003)

Simple bench top inline DHM

30 cm

cuvette

CCD

camera

spatial

filter

20X

objective

CW

laser

CW laser good for quiescent solutions

A Free-Drifting Submersible Digital Holographic

Imaging System (Holosub)

PROTOTYPE TO HOLOCAM

Joe Katz (Johns Hopkins University)

a b C

4

8

12

16

22.4 22.6 22.8 23σt (kg/m3) Shear rate (/s)

400 800

Dep

th (

m)

-0.1 -0.06 0 0.04Small Particle Count (/ml)

Dissipation rate (m2/s3×10-7)1.0 1.2 1.4

East Sound, WA, USA May, 2010

pulsed laser

PIV

water density

PSD

particle

concentration

Talapatra et al., in review

Long diatom chains

6 ml sample volume

Eucampia

Chaetoceros

socialis

(~1 mm)

Pseudonitzchia

preferential

orientation!

4.2 m 3.1 m

15.8 m 6.7 m

22.4 22.6 22.8 23Density - 103 (kg/m3)

C

Shear rate (/s)

ba

20 40 60Angle (Degrees)

4

8

12

16

Dep

th (m

)

(II)

(I)

(III)

-0.1 -0.06 0 0.04

Diatom Mean chain Length (mm)1.0 2.0 1.0 2.0 3.0 4.0

Diatom chain count (/mL)

1.0 1.2 1.4

Dissipation rate (m2/s3×10-7)

Most of the water column shows statistically

significant deviations from a randomly

oriented particle field!

Talapatra et al., in review

Next Generation Submersible Holocamera

sample volumes:

10 L high mag

2.25 mL low mag

1 m

Concept for sampling effects of orientation

Polarization and orientation

Pseudonitzschia

Sampling resolution: LOBO Land/Ocean Biogeochemical Observatory

Small mooring system

Hourly, real-time observations

Maintenance cycle ~ 4 months

Instrumentation • Temperature, Conductivity, Pressure, Dissolved O2,

Chlorophyll and phycobiliprotein pigment fluorescence,

DOM fluorescence, Turbidity

WET Labs – SeaBird WQM

• Nitrate – Satlantic SUNA sensor

• Phosphate – WET Labs CYCLE sensor

• Ammonium – WET Labs CYCLE sensor

• Wireless telemetry via cellular phone

Emphasis on high quality, accuracy, and reliability

(x,y,z,dt)

Autonomous Moored Profiler (AMP)

High resolution sampling

of the full water column

Maintenance cycle 1-2

months

150 meter capable

Featured design for OOI

The AMP design evolution

represents over a decade of

commitment.

Dep

th (

m)

Salinity

(x,y,dz,dt)

Sullivan et al. (2010)

Cont. Shelf Res. 30: 50-65 decimal day (PDT)

Monterey Bay 2002

Monterey Bay 2005

Resolving phytoplankton dynamics with AMP

highly motile dinoflagellates non-motile diatoms

decimal day (PDT)

2005

physics

behavior

2002

Underlying Mechanisms

Mapping optical properties with a towed

vehicle (DOLPHIN)

tow 1

tow 4

(dx,dy,dz,dt)

Hudson River plume

Thank you!