# Presentation: 153667

## The Effects of a Spring Resuspension Event on In-situ Optical Parameters and Phytoplankton Light Utilization

**The Effects of a Spring Resuspension Event on *****In-situ***** Optical Parameters and Phytoplankton Light Utilization**

**Trisha Bergmann**
**Gary Fahnensteil**
**Steven Lohrenz**
**David Millie**
**Oscar Schofield**

**Coastal Ocean Observation Lab**
**Institute of Marine and Coastal Sciences**
**Rutgers University**

## Study Area – Southern Lake Michigan

**Study Area – Southern Lake Michigan**

##  Optical closure in a variable light environment

** ****Optical closure in a variable light environment**
** ****Light utilization by phytoplankton communities**

## Temporal evolution of the sediment plume

**April 1999**

**June 1999**

**March 1999**

**Temporal evolution of the sediment plume**

**Notes:**
These plots are all along the J transect

Do we have image showing high reflectance in march 2000?  Measured Rrs was so high!

## Optical Properties of the sediment plume

**Attenuation  (m****-1****)**

**Absorption  (m****-1****)**

**1.5**

**0**

**0**

**1**

**Optical Properties of the sediment plume**

**Absorption  (m****-1****)**

**Attenuation  (m****-1****)**

**Notes:**
Absorption and attenuation in plume Vs. non-plume waters (see figures above and below) of the Cook nuclear power plant transect line (stations ck10, ck20, ck30, ck45 - the Final Four) March 1999.  Both attenuation and absorption are much higher within the plume waters. Scattering dominates total light attenuation in the RCP especially at low wavelengths. The increased attenuation, in turn dramatically alters the light available for phytoplankton growth.

## Optical Identification of the plume

**Optical Identification of the plume**

**Notes:**
Abs scale 1- 1.5

## Closure Between IOPs and AOPs

**Solving the Radiative Transfer Equation with Hydrolight 4.2**

**RTE**

**Notes:**
J99108
Do I need a figure like this??

Given this, one focus of EEGLE 2000 field campaign is to achieve optical closure in near surface waters which play a disproportionately large role in remote sensing algorithms. Furthermore, the measured and modeled radiometric quantities will provide inputs to primary productivity and food web models. 

## Hydrolight vs. measured data

**Hydrolight vs. measured data**

- Wavelength (nm)

- R2 measured vs
- modeled Rrs

**Notes:**
48 points from 2 years of spring data per wavelength for the r2 values
Measured and modeled figures are for 99153f (m110)
See also measured and modeled Kd cross shelf plots for the J transect 
Should r2 fig include slope of the line??

## Inversion of remote sensing reflectance vs. measured in-water data

**Remote Sensing Reflectance**
**(sr****-1****) at 555nm**

**bb/a at 555nm**

**Notes:**
Bb/a vs rrs measured at 555nm
Chl calced using O’Reilly equation vs Millie’s chl data

Next step – take it to remote sensing data.  

## Phytoplankton Community Composition II

**Phytoplankton Community Composition II**

**cryptophytes**
**chlorophytes **
**cyanobacteria**
**diatoms**

## Phytoplankton Distribution

- 0

- 5

- 10

- 15

- 20

- 25

- 30

- Distance from Shore (km)

- 0.26

- 0.30

- 0.34

- 0.38

- 0.42

- 0.46

- 0.50

- 0.54

- 0.58

- 0.62

- 0

- 5

- 10

- 15

- 20

- 25

- 30

- Distance from Shore (km)

- 100

- 80

- 60

- 40

- 20

- 0

- D

- e

- p

- t

- h

- (

- m

- )

- Diatom Relative Abundance

- March, 1999

- Cryptophyte Relative Abundance

- March, 1999

**Notes:**
ChemTax©-Derived Phytoplankton Relative Abundance
St. Joseph Transect; 23-25 March, 1999

## Phytoplankton Distribution

**% Chl - Cryptophytes**

**% Chl - Diatoms**

**Phytoplankton Distribution**

## Why is the sediment plume important to biology?

**Depth (m)**

- 5

- 10

- 40

- 70

- 100

**cryptophytes**
**chlorophytes **
**cyanobacteria**
**diatoms**

## Single Cell Absorption spectra for Diatoms and Cryptophytes

**Diatoms**
**Cryptophytes**

**Single Cell Absorption spectra for Diatoms and ****Cryptophytes**

**Wavelength (nm****-1****)**

**Single Cell **
**Absorption (m****-1****)**

**Chl *****a***

**Chl *****c******2***

**Alloxanthin**

**phycoerythrin**

**Chl *****a***

## Available Light field and potential absorption

**Available Light field and potential absorption**

- Irradiance Ed**(λ)** (μmol photons m-2 s-1)

- Potential Cryptophyte absorption **= Ed(λ)* a****PH****(λ)**

- Potential Diatom absorption **= Ed(λ)* a****PH****(λ)**

**Wavelength**

**Irradiance **
**(μmol photons m****-2**** s****-1****)**

**Notes:**
Rhodomonas lens and small centric diatom

Check these units!!!

## Rates of photon absorption for diatoms and cryptophytes

**Diatoms**
**Cryptophytes**

**Total photon absorption for ****cryptophytes**** is 2.5X that for diatoms at depth**
- photon abs. = efficiency of absorption (Qa) * surface area of cell * irradiance (Eo)

**Surface**

**Depth (30m)**

**Wavelength**

**Wavelength**

**Photon absorption **
**(photons s****-1 ****nm****-1****)**

**Photon absorption **
**(photons s****-1 ****nm****-1****)**

## Conclusions

**Conclusions**
** ****parameters calculated from Rrs measurements correlate well with in-water measured values**
** ****light availability within the recurrent sediment plume is spectrally restricted, affecting phytoplankton community composition**
** **

## Acknowledgements

**Acknowledgements**

**Larry Boihem**
**Kimberly Kelly**
**Augie Kutlewski**
**Merrett Tuel**
**Rich Stone**
**the Captain and Crew of the R/V Laurentian**
**Funding provided by NSF (OCE-9727342) and NOAA through the CoOP Great Lakes Initiative.**