TITLE: HLY-02-03 VPR Data

AUTHOR:
C. J. Ashjian and S. M. Gallager
Department of Biology
Woods Hole Oceanographic Institution
Woods Hole, MA 02543
Tel: (508)289-3457
Fax: (508)457-2134
Email: cashjian@whoi.edu

FUNDING SOURCE AND GRANT NUMBER: NSF OPP-0124766

DATA SET OVERVIEW:

Video Plankton Recorder Data Collection and Analysis

     Data were collected on a cruise (HLY0203) to the
Chukchi and Beaufort Seas on the USCGC Healy from July 17 -
August 26, 2002 as part of the Shelf Basin Interactions
program.  The primary sampling instrument was a self-
contained, battery powered, single camera Auto Video
Plankton Recorder (AutoVPR; SeaScan, Inc.) that was deployed
from the stern of the ship in a stainless-steel cage. The
AutoVPR records video image frames from a Pulnix TM7 CCD
camera at 720 x 640 pixels at 30 Hz as a wavelet compressed
data stream together with coincident data from a SeaBird
SBE49 CTD operating at 10Hz. The image field of view was
calibrated to 1.3 x 1.0 x 6.8 cm (length x width x depth)
with a precision of  ± 0.02 cm giving an image volume of
8.84 ± 0.34 ml. With a vertical profiling speed of 0.5 ms-1,
a new image volume was recorded every 1.6 cm providing
nearly contiguous vertical coverage by video information and
CTD data at an interval of 5 cm. Profiles were conducted
between the surface to 10 m off the bottom or to a maximum
depth of 350 m. Immediately following a deployment, video
files were down loaded from the internal PC104 computer to a
desk top PC via Ethernet. Video files were decompressed and
in-focus targets extracted as Regions of Interest (ROI) and
written to disk as tagged interchange files (tif) using
software provided with the instrument.  Extracted images
were identified to taxon or particle type manually and
merged by time with pressure, temperature, salinity, and
density data from the CTD using Matlab (Mathworks, Inc.)
routines. Average pressure, temperature, salinity, and
density and taxon or particle concentrations were calculated
in 1-second intervals.  Down and up casts were averaged by
depth (1-m intervals) to yield a single profile.
     Thirty-three deployments of the AutoVPR were conducted,
although data from only twenty-nine profiles are considered
here (of the four deployments not considered, two were
conducted far to the south, one was a single replicate, and
one contained no data).  Profiles were collected at most of
the standard SBI stations regardless of the time of day.
Daylight was present throughout all 24 hours for these
dates.  Over 61,000 in-focus images were collected from
these profiles.  Nine taxa or particle types were
identified:  copepods, diatom chains, decaying diatoms,
larvaceans, benthic larvae (primarily polychaete and
echinoderm), marine snow, medusae (hydromedusae and
scyphomedusae not differentiated), nauplii (primarily
copepod) and radiolarians.  Decaying diatoms were diatom
chains that were observed visually to have accumulated
flocculent material along the rod but were still easily
identified as diatom chains Data from rarely observed taxa
(e.g., pteropods, chaetognaths, ostracods) are not
presented.

DATA FORMAT:
     There is a single data file for each cast using the
AutoVPR.  The data files are named according to the station
number.  Each data file contains 14 columns. There is a
header row at the top that describes the variables.  Columns
contain as follows:  Columns 1:2=cast location (Latitude,
Longitude) in decimal degrees, Column 3 = pressure in dbars,
Column 4 = Water temperature (°C), Column 5 = Salinity,
Column 6 = Density (sigma-t units), Column 7 = copepods
(#/L), Column 8 = diatom rods (#/L), Column
9=Decaying/Fuzzy Diatoms (#/L), Column 101 = Larvaceans
(#/L), Column 11=Benthic Larvae (#/L), Column 12 = Marine
Snow (#/L), Column 13= Medusae (#/L), Column 15=Nauplii
(#/L), Column 14 = Radiolarians (#/L).
     An accompanying table contains details on the date,
time, location, water depth, and tow depth for each profile.
Times/dates are presented both in Alaska Time and GMT.