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Optical Sensors Mary Jane Perry University of Maine ALPS Workshop 31 March 2003 La Jolla, California. What variables are amenable to detection and measurement by optical sensors ?.

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optical sensors mary jane perry university of maine alps workshop 31 march 2003 la jolla california
Optical SensorsMary Jane PerryUniversity of MaineALPS Workshop31 March 2003La Jolla, California
slide2

What variables are amenable to detection

and measurement by optical sensors ?

* Particles -> scatter light - biologics (viruses, bacteria, phytoplankton, zooplankton, small fish) - inorganics (non-biogenic & biogenic, CaCO3)* Particles and dissolved materials -> selective absorption in UV and visible - phytoplankton - iron-rich minerals - C-DOM - nitrate

slide3

1. Individual particles * imaging (video plankton recorder) * analysis (flow cytometer) 2. Radiometric analysis of “bulk” optics * passive * active

Two approaches to optical measurement:

slide5

Today:Scientific questionsExamples of measurement from individual particle analysis radometeric sensorsChallenges for ALPS optical sensors

scientific questions

Scientific questions

What species are in the plankton and how does species composition change in response to environmental variability?

* events - storms, aeolian Fe-rich dust

* inter-annual and climatic change

* HABs, species invasion, top predator loss

(we don’t know due to lack of sustained observations)

scientific questions7

Scientific questions

What are the patterns of distribution

and abundance of:

* individual species

- bioluminescent organisms, salps, etc.

* “bulk” variables

- particulate & dissolved organic carbon

- suspended minerals

- total phytoplankton (satellite limitations-->)

north atlantic spring bloom april9
North Atlantic spring bloom, April

pigment concentration pixels / month

scientific questions10

Scientific questions

How do processes vary in space/time and

in response to environmental variability?

* carbon cycle

net carbon fixation

carbon flux

coccolithophorid production

* sediment resuspension and

riverine mineral delivery

imaging of individual particles

Imaging of individual particles

Goal to identify taxa

Target particles:

phytoplankton, zooplankton & small fish

Challenges

Image quality

Pattern recognition algorithms

(Presentation of organism to camera)

Large size and high power consumption

Some systems have been deployed on AUVs

slide12

Copepods - video plankton recorder

(Gallager and Davis, WHOI)

slide13

Flow Cytometery of individual particles

*individual particle scattering and fluorescence*could be coupled w/ molecular probes* large size & high power consumption (data from Cytobuoy)

radiometry second approach to optical measurement

Radiometry - second approach to optical measurement

* “Bulk” properties (vs. individual particles)

* Active and passive sensors

* Smaller and lower power (vs. individual particles)

*** Concept of proxies

e.g., phytoplankton can be measured as

absorption coefficient

beam c or scattering coefficient (if no inorganics)

fluorescence intensity

diffuse attenuation coefficient (Kd)

remote sensing reflectance

radiometry

Radiometry

* Inherent Optical Properties

absorption, scattering, attenuation

* Apparent Optical Properties irradiance, radiance, reflectance, diffuse attenuation coefficient

* energy conversions

fluorescence

bioluminescence

radiometry16

Radiometry

* Inherent Optical Properties - active

absorption, scattering, attenuation

* Apparent Optical Properties - passive irradiance, radiance, reflectance, diffuse attenuation coefficient

* energy conversions

fluorescence - active

bioluminescence - passive

slide17

Active sensors - higher energy - internal light source + nighttime and at depth Passive sensors + lower energy - solar light source - daytime only and in photic zone + diffuse attenuation coefficient fouling independent

slide18

Active radiometers * Inherent Optical Properties absorption scattering (total, forward, backscattering)attenuation (beam c)* Energy conversionfluorescence

eriksen seaglider
Eriksen Seaglider

WET Lab bb2f, measure chl fluorescence

as proxy for phytoplankton

and particle backscattering at 2 ls

slide20
gli

Glider track

off Washington

Next 3 figures,

please note

axis is time

slide24

Bishop et al. Iron stimulation (by dust storm)

of phytoplankton production at Station PAPA, 2001

Two drifters with beam transmissometer

(a proxy for POC)

slide26

Passive radiometers * Apparent Optical Properties irradiance and radiance diffuse attenuation coefficient * Energy conversion bioluminescence

e d l
Ed (l)

Underwater

light field

(data from Carder, on an AUV)

Lu(l)

slide28

Mitchell et al. Evolution of phytoplankton bloom in the Sea of Japan. Ed, Lu was measured at 3 l ,with on-board calculation of Kd.

SOLO drifter

track in

Sea of Japan,

spring 2000

slide31
AUV measured backscattering, chlorophyll fluorescence, and bioluminescence in Monterey BayHaddock et. al. (complements of J. Case)

bb

BL

F

slide33

Sensor sizePower requirementsSensor calibration, QA, QCStability in long-term deployments (long-term)Biofouling solutions Interpretation of proxies; need for multiple proxiesVolume sampled in patchy environmentsOptimization of sampling rate; conditional samplingData storage, on-board processingGeospatial/temporal data analysis