Dynamic of Chromophoric Dissolved Organic Matter CDOM in the Mayagez Bay

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Dynamic of Chromophoric Dissolved Organic Matter
(CDOM) in the Mayagüez Bay

• Patrick Reyes-Pesaresia and Fernando
  Gilbes-Santaellab
• aDepartment of Marine Science
• bDepartment of Geology
• University of Puerto Rico at Mayagüez
• 6th Annual NOAA-CREST Symposium
• February 22, 2008

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What is this famous Chromophoric (Colored)
Dissolved Organic Matter (CDOM)

• CDOM is an operational definition
• They are all the dissolved organic substances
  in a water sample that after being filtered (0.22
  µm) absorbs light in the UV-visible region of the
  electromagnetic spectrum.
• CDOM is one of the four components that absorbs
  visible light in the aquatic environment.
• a(?) aw(?) ad(?) aph(?) ag(?)
• Where
• a(?) total absorption
• aw(?) water absorption
• ad (?) detritus absorption
• aph(?) phytoplankton absorption
• ag(?) CDOM absorption

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Of what is this CDOM made off?

• The bad thing is that no body is quite sure of
  its composition!
• 1- It is believed that CDOM is the result of the
  decomposition of terrestrially derived plant
  material mostly lignins that are then transformed
  to humic and fulvic acids both by biotic and
  abiotic factors and that are later transported to
  coastal environments
• 2- Other workers suggest that sugars can be a
  source of CDOM after being modified by biotic and
  abiotic.

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What we really know is what it does it the
aquatic environment

• 1- It is noise in the remote sensing signal for
  chlorophyll-a estimates in coastal waters
• 2- It can influence the quality and quantity of
  light in aquatic environments.
• 3-It can control the availability of nutrients
  that are used by phytoplankton
• 4- It has been related to the production of H2O2,
  free radicals and oxidation state of metals
• 5- It compose a large fraction of the Dissolved
  Organic Matter (DOM 40-60) with the advantage
  that it can be studied by Remote Sensing
  Techniques

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CDOM Absorption Coefficient Spectrum and of
Chlorophyll-a Percent of Absorption
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Objectives

• To determine the contribution of the CDOM to
  the bio-optical properties in the Mayagüez Bay
  from an inshore-offshore gradient between the
  rainy and dry season.
• What are the possible effects of the river
  transported clays on the CDOM when they enter in
  contact with marine waters?
• Use Remote Sensing Reflectance gathered with a
  portable Spectroradiometer (GER-1500) to monitor
  the dynamics of CDOM

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Study Area
Inshore stations A1 AAA1 Y1 G1 Offshore
stations A2 AAA2 Y2 G2
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Field Work
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Field Work

• Bio-optical package profiles
• Salinity (CTD)
• Temperature (CTD)
• Total absorption and attenuation coefficient
  at 9 wavelengths (ac-9)
• Chlorophyll-a Fluorescence (Fluorometer)
• Backscattering at 6 wavelengths
  (Hydroscatt-6)
• Downwelling irradiance (OCR-200 Ed) and and
  upwelling radiance (OCR-200 Lu) at 7 wavelenghts
  one for PAR
• GER-1500 Spectroradiometer (Remote Sensing
  Reflectance)

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Laboratory Work

• Samples taken in the field were analyzed for
• CDOM
• Absorption coefficient
• Spectral Slopes
• Chlorophyll-a concentration
• Total Suspended Solids (TSS) concentration
• Laboratory experiments
• Marine and River water end member dilutions
• As above solids extracted from the river
  waters

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Dilution diagram between marine and river water
end members
Clays were qualitatively identified by XRD
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A1 station salinity and 412 total absorption
profiles
River discharge
River discharge
Resuspention?
Resuspention?
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Real time series CDOM (ag375) concentration for
inshore and offshore stations
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Real time series Total Suspended Solids
concentration for inshore and offshore stations
High river discharge
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Salinity comparison between the Rainy and Dry
season
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Total Suspended Solids comparison between the
Rainy and Dry season
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ac-9 (412 nm channel) comparison between the
Rainy and Dry season
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Rrs412/Rrs510 vs. ac-9 412 channel
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Rrs412/Rrs510 vs. CDOM ag 412 channel
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ac-9 412 channel vs. CDOM ag412 Correlation
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Summary

• We have found significant differences between
  seasons for salinity, CDOM absorption (ag375) and
  TSS
• During the wet season the CDOM absorption
  coefficient and the TSS distribution are
  correlated to salinity due to the rivers
  discharge.
• During the dry season the CDOM and TSS on can be
  explained due to the resuspention of both from
  the bottom.
• Laboratory mixing experiment between marine
  and river waters end members indicate that CDOM
  is lost possibly by flocculation during estuarine
  mixing and clays material transported by river
  waters decrease further the CDOM signal
  (absorption coefficient) during estuarine mixing.
  This fact will help further in the understanding
  of the biogeochemistry of CDOM dynamics.
• CDOM Absorption coefficient (ag412) is well
  correlated with the total absorption 412 measured
  with the ac-9 and with the remote sensing band
  ratios Rrs412/Rrs510.

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CDOM Distribution the Mayagüez Bay

• 1- During the wet season the CDOM absorption
  coefficient and the TSS distribution are
  correlated to Salinity due to the rivers
  discharge.
• 2 - During the dry season the high CDOM
  absorption coefficient and TSS can be explained
  due to the resuspention for both from the bottom.

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Questions?