Summary of absorption and pigment analyses in
support of reservoir monitoring by the Los Angeles Department of Water and
Submitted August 7, 1998 to Dr. Brian White
Los Angeles Department of Water and Power
Scripps Institution of Oceanography Photobiology Group
Dr. B. Greg Mitchell, Principal Investigator
La Jolla, CA 92093-0218
619-534-2687; fax: 619-534-2997
From late February through late June, the Scripps Photobiology Group
(SIO SPG) carried out analyses of particle, detrital and soluble absorption
coefficients (ap, ad, as) and chlorophyll plus phaeo pigments (chl+phaeo)
for samples collected periodically by technicians of the Los Angeles Department
of Water and Power (LADWP). The work accomplished through the end of July,
1998 is summarized in this report.
The report is organized by tabbed sections as follows:
- Financial Summary Summary of salary, wages and spectrophotometer service
- LADWP Summary data Print out of a summary Microsoft Excell worksheet
- LADWP Summary graphs Graphs of key summary parameters for two reservoirs
- ap/ad/as sampling log Log sheets of all absorption spectra run by SIO
- Chl sampling log Log sheets of all chlorophyll + phaeopigment analyses
- Chl sample Raw readings and estimates of chlorophyll and phaeopigments
- ap/ad/as Processed Graphs Spectra of Processed ap/ad/as in units of
- ap/ad/as Raw Graphs Raw absorbances determined for each spectrum
- Protocols Summary of the methods used for analyses
Observations and Conclusions
After a very preliminary evaluation of raw and processed data, several
key points and conclusions may be drawn based on evaluating the graphs in
the tabbed sections "LADWP Summary Graphs" and "ap/ad/as
Processed Graphs". These preliminary observations and conclusions are
not construed as a final, scientific interpretation, but rather a brief,
- Figure 1 indicates chlorophyll bloomed at REOS Hollywood site but not
the Stone Canyon site. LADWP chlorophyll estimates at REOS Hollywood were
generally much higher than the SIO SPG estimates (e.g. up to 50x higher)
but at Stone Canyon, the SIO SPG chl estimate were similar to LADWP, and
sometimes even higher but up to a factor of 2.
- Figure 2 indicates that the SIO SPG ap(675) nm generally tracks the
chlorophyll estimates of LADWP with REOS Hollywood revealing the bloom
after 5/5/98 and tracks the declining LADWP chl estimate in Stone Canyon
- Figure 3A and 3B illustrate the change in the ratio of ap400/ap675
over time. REOS Hollywood drops from extraordinarily high ratios of 40-60
early to less than 10 after the bloom onset around 5/5/98. In Stone Canyon,
this ratio is between 4-10, with no clear systematic time dependence.
- Figure 4 summaries the parameter ap*(675) which is defined as the ratio
of ap*(675)/chl (for LADWP chl estimates) or ap*(675)/chl+phaeo for the
SIO SPG chl+phaeo graphs. Values at REOS Hollywood using LADWP chl range
from 0.004 to 0.016. Values of 0.016 are quite reasonable compared to oceanic
observations; values of 0.004 would be low. Values in Figure 4C using the
SIO SPG chl+phaeo for REOS Hollywood indicate values of ap*(675) from 0.2
to 0.6, values considered very high compared to typical oceanic conditions.
At Stone Canyon the ap*(675) using SIO SPG values are lower, but not substantially,
than the LADWP, and in general, the range in values of about 0.005 to 0.05
range from moderately low, to moderately high, compared to oceanic values,
but the Stone Canyon values using LADWP chl average ap*(675) of approximately
0.02 which would be a very reasonable oceanic value.
- Examination of the spectral ap and ad plots reveal that after the chlorophyll
bloom, there is significant un-extracted chlorophyll after the methanol
extraction of the ap sample at the REOS Hollywood site. The result is residual
absorption at the red peak. This is not noted for the Stone Canyon reservoir
which seems to extract very well with MeoH, similar to typical oceanic
samples. We believe that the lack of adequate extraction using methanol
indicates the potential presence of cyanobacteria which are known to be
difficult to extract. This is further supported by the appearance of a
strong absorption shoulder near 490-500 nm during the bloom period at REOS
Hollywood. Such a shoulder could be consistent with presence of phycourobilin,
a common pigment in cyanobacteria. However, strong absorption in the phycoerythrin
absorption region near 545 nm is not noted. It is possible to have cyanobacteria
that have high phycourobilin/phycoerythrobilin so that the 545 nm absorption
may be minor.
- The bulk extraction and spectrophotometeric method of LADWP could possibly
overestimate chlorophylls if significant non-chlorophyll pigments are extracted
with absorption in the region used for the spectrophotometric absorption
method. This would not be a surprising finding given the huge ap400/ap675
ratios that indicate extreme concentrations of detrital particulates, some
of which will extract and absorb in the same wavebands as chlorophyll.
- It is possible that the filtration of samples and storage dark on ice
for up to 24 hours for the SIO SPG chlorophyll led to some chlorophyll
degradation and loss.
- ap, ad and as estimates provide a unique method to partition the turbidity
of the REOS optics system into the phytoplankton, detrital and soluble
fractions, and are therefore a valuable asset for future data in support
of the REOS systems.
- At 400nm the as is generally 2x-5x larger than ap and is even larger
relative to ap at 300nm.
- Stone Canyon as values are 1.5x to 2x larger than REOS Hollywood values.
- Chlorophyll methods of both SIO SPG and LADWP need to be scrutinized.
We propose a detailed single day pigment determination intercomparison
where SIO SPG technicians join LADWP technicians for one day of sampling.
The plan would be to:
- A. take samples for standard LADWP spectrophotometric and SIO SPG fluorometric,
plus additional samples for HPLC methods.
- Replicate samples of each method, one set to extract 24 hours, the
other to be ground after arrival at SIO SPG lab, and then kept for 24 hours.
- All samples to be filtered fresh and extracted immediately.
- Results, especially the HPLC methods, will allow definitive determination
of problems in chlorophyll estimates noted above
- Carry out a detailed integration and interpretation of the REOS in
water optics and the water sampled ap, ad, and as data sets.
- Continue sampling for particle and soluble optics, and pigments, if
Descriptions for filenames
The zip diskette contains :
- backup raw data files.
- processed excel spreadsheets of the data.
- unprocessed excel spreadsheets of the data.
- procedures and protocols.
- fully processed data files.
- LADWP summary report.
The raw data files are in the subdirectory :/backup_of_samples/*.*
The *.sp2 are files that were run on the Varian spectrophotometer.
The *.dx are files that were run on the Perkin Elmer spectrophotometer.
The processed data files are in the subdirectory : /report_to_ladwp/processed_results/*.*
The files with the extensions of *.fr1 are ap/ad files.
The files with the extensions of *.sp6 are as files.
Graphs maybe generated using the asstaplt.m files in the program subdirectory
along with the block files. Read the apadpro32_552_readme.doc for protocol
on running the apadpro32_552.exe program. The asstaplt.m file is a Matlab
program. It is used to generate processed graphs only. Processing of the
data is done with apadpro32_552.exe