OPC_CCS

U.S. GLOBEC Northeast Pacific California Current Program
Optical Plankton Counter (OPC) Project description

Contact for this dataset is:
Dr. Meng Zhou (meng.zhou@umb.edu)
Phone: 617-287-7419; Lab: 617-287-6186
 

This project addresses one of 3 central hypotheses of the U.S. GLOBEC
Northeast Pacific (NEP) Study:

Spatial and temporal variability in mesoscale circulation constitutes
the dominant physical forcing on zooplankton biomass, production,
distribution, species interactions and retention and loss in coastal
regions.(U.S. GLOBEC Northeast Pacific Implementation Plan,
U.S. GLOBEC Report No. 17).

We attached an Optical Plankton Counter (see Zhou and Tande, 2002) to
the OSU towed body (SeaSoar) to make 3-dimensional mesoscale surveys
(in a 100-km-wide coastal region from Newport, Oregon to Crescent
City, California) aimed at determining the distribution and
productivity of zooplankton in relation to their physical environment.
The OPC provides counts and size estimates of zooplankton sized
particles that pass through the instrument.  The OPC data with other
data sets (e.g., acoustics; ADCP-derived velocities) collected on
these surveys, and from companion ships doing net sampling of
zooplankton will allow estimation of growth and mortality rates of
zooplankton using teh biomass spectra method (Zhou and Huntley, 1997).

Data Description

The OPC-CCS data are organized on the GLOBEC server by transect within
cruise.  The master (level0) page lists all of the cruises--there were
two cruises in each of 2000 and 2002.  Clicking on a cruise will show
all of the casts collected and processed from that cruise (Level1),
along with the start date and time of the transect.  Clicking on a
cast will bring up the Level2 file that shows OPC profile data.  The
raw data stream is averaged and output at every 4-m bin.  The towed
body undulates between a near-surface, shallow depth and a deeper
depth (which hopefully is ABOVE the bottom).  During normal ascent and
descent rates of the SeaSoar, approx. 5-30 readings are averaged
within every 4 m depth bin.  At times of particularly slow depth
change, more readings are included in these averages.  Average
latitude and longitude and date/time (GMT) for each depth bin are
shown.  OPC data for each reported depth bin include the total
abundance of particles (no per m3), total carbon biomass (ug C/m3;
estimated from equivalent spherical diameter (ESD) based on Rodriguez
and Mullin (1986)), and a biomass spectrum (50 size classes of
particles).  The header for the biomass spectrum header (minimum of
0.33; maximum of 4.09) values are log10 based carbon intervals of
individual particle size.  There are 50 biomass size classes.  The
data for each of the spectra are the accumulated carbon of that size
particle, normalized by the water volume, then normalized by the
carbon interval, then expressed as log10 units.  So the unit of
biomass for each spectral class is log10(biomass spectrum (1/m3)).



Level 0 variables	  Contents[units]
cruiseid		  Cruise ID
year			  Year


Level 1 Variables	  Contents[units]
transect		  Transect Description
start_month_gmt		  Month of Transect Start (GMT)
start_day_gmt		  Day of Transect Start (GMT)
start_time_gmt		  Time of Transect Start (GMT)


Level 2 Variables	  Contents[units]
elptime			  Elapsed time from Start Time [hours]
month_gmt		  Month
day_gmt			  Day
time_gmt		  Time
lat			  Latitude [decimal degrees]
lon			  Longitude [decimal degrees]
depth			  Depth of Observation [meters]
abundance		  Total Abundance [counts/m3]
biomass			  Total Biomass [ug C/m3]
biovol			  Total Biovolume [mm3/m3]
fluor			  Chlorophyll [mg/m3] See Note 1 below.
0.33			  Smallest Size Class of biomass spectrum (Note2)
0.41
0.49
0.56
0.64
0.72
0.79
0.87
0.95
1.02
1.10
1.18
1.25
1.33
1.41
1.48
1.56
1.64
1.71
1.79
1.87
1.94
2.02
2.10
2.17
2.25
2.33
2.40
2.48
2.56
2.63
2.71
2.79
2.86
2.94
3.02
3.09
3.17
3.25
3.32
3.40
3.48
3.55
3.63
3.71
3.78
3.86
3.94
4.01
4.09			Largest Size Class of biomass spectrum (Note2)


Note 1:  A fluorometer was interfaced with the OPC only for cruise
NH0005.  For all other cruises, the 'fluor' field value of 0.00 means
'no data'.

Note 2: Biomass spectrum contents:
Header value of 0.33 means particles of ca. 10^0.33 = 2.138 ugC per
particle.  Largest particle size (header value 4.09 is particles of
ca. 12302 ugC per particle.     

References

Rodriguez, J. and M. M. Mullin. 1986.  Relation between biomass and
body weight of plankton in a steady state oceanic ecosystem.
Limnol. Oceanogr., 31, 361-370.

Zhou, M. and M. E. Huntley. 1997.  Population dynamics theory of
plankton based on biomass spectra.  Mar. Ecol. Prog. Ser., 157, 61-73.

Zhou, M. and K. S. Tande. 2002.  Optical Plankton Counter workshop
report.  International Global Ocean Ecosystems Dynamics Program
Report, No. 17, 67 pp.

More Information about these data are available from:

Dr. Meng Zhou
Dept. of Environmental, Coastal and Ocean Sciences
University of Massachusetts-Boston
Boston, MA 02125
meng.zhou@umb.edu
Phone: 617-287-7419; Lab: 617-287-6186
FAX: 617-287-7474
http://www.harbor2.umb.edu/zhou/zhou06.htm