INTRODUCTION
The data presented in this report were
collected during cruise 0401*
of the California Cooperative Oceanic Fisheries Investigations (CalCOFI)
program aboard the RV David Starr Jordan
of Scripps Institution of Oceanography,
STANDARD PROCEDURES
CTD/Rosette Cast Data
A Sea-Bird Electronics, Inc.,
Conductivity-Temperature-Depth (CTD) instrument (Seabird 911, Serial number
1049) with a rosette was deployed at each station on these cruises. The rosette was equipped with 24 ten-liter
plastic (PVC) bottles equipped with epoxy-coated springs and Viton
O-rings. Each CTD/rosette cast usually
sampled 20 depths to a maximum sampling depth of 525 meters, bottom depth
permitting. Occasional stations have
multiple bottles tripped at the same depth to provide more water for ancillary
programs. The sample spacing was designed to sample depth intervals as close as
10 meters around the sharp upper thermocline features such as the chlorophyll,
oxygen, nitrite maxima and the shallow salinity minimum. Salinity, oxygen and nutrients were determined
at sea for all depths sampled. Chlorophyll-a and
phaeopigments were determined at sea on samples from the top 200 meters, bottom
depth permitting.
Pressures and temperatures assigned to the
water sample data were derived from the CTD signals recorded just prior to the
bottle trip. Pressures have been
converted to depths by the Saunders (1981) pressure-to-depth conversion
technique. CTD temperatures reported
with the bottle data have been rounded to the nearest hundredth of a degree
Celsius.
Salinity samples were collected from all rosette bottles and analyzed at sea using a Guildline model 8410 Portasal salinometer. Salinity samples were drawn into 200 ml Kimax high-alumina borosilicate bottles that were rinsed three times with sample prior to filling. The results were compared with the CTD salinity to verify that the rosette bottle did not mis-trip or leak. The salinometer was standardized before and after each group of samples with standardized seawater. Periodic checks on the conductivity of the standardized seawater were made by comparison with IAPSO Standard Seawater batch P140. Salinity values were calculated using the algorithms for the Practical Salinity Scale, 1978 (UNESCO, 1981a) and are reported to three decimal places, provided that accepted standards were met.
Nutrient samples were analyzed at sea for dissolved silicate, phosphate, nitrate and nitrite using procedures similar to those described in Gordon et al., 1993. Samples were collected in 45 ml high-density polypropylene screw-capped tubes, which were rinsed three times prior to filling. Standardizations were done at the beginning and end of each group of samples with a set of mid-concentration range standards prepared fresh for each run. Samples not analyzed immediately after collection were refrigerated and run the following day. Sets of six different concentration standards were analyzed periodically to determine the deviation from linearity as a function of concentration, for the silicate, nitrate and phosphate analyses. Final sample concentrations were corrected for deviations from linearity using a second order polynomial.
Samples for chlorophyll-a and phaeopigments were collected in calibrated 138 ml
polyethylene bottles and filtered onto Whatman GF/F filters. The pigments were extracted in cold 90%
acetone (Venrick and Hayward, 1984) for a mimimum of 24 hours. Chlorophyll a and pheopigment concentrations
were determined from fluorescence readings before and after acidification with
a Turner Designs Fluorometer Model 10-AU-005-CE (Yentsch and Menzel, 1963;
Holm-Hansen et al., 1965).
Evaluation of the water sample data
involved comparisons with the CTD data, adjacent stations and consideration of
the variation of a property as a function of density or depth and the
relationships with other properties (Klein, 1973). Precision estimates for routine analyses were
made on CalCOFI cruise 9003 and are reported in SIO Ref. 91-4.
Primary Productivity Sampling
Primary productivity samples were taken
each day shortly before local apparent noon (LAN). Primary production was
estimated from 14C uptake using a simulated in situ
technique. Light penetration was
estimated from the Secchi depth (assuming that the 1% light level is three
times the Secchi depth). The depths with
ambient light intensities corresponding to light levels simulated by the
on-deck incubators were identified and sampled on the rosette up-cast. Occasionally an extra bottle or two were
tripped in addition to the usual 20 levels sampled in the combined
rosette-productivity cast in order to maintain the normal sampling depth resolution. Triplicate samples (two light and one dark
control) were drawn from each productivity sample depth into 250 ml
polycarbonate incubation bottles.
Samples were inoculated with 10 µCi of 14C as NaHCO3
(200 µl of 50 µCi/ml stock)
prepared in a 0.3 g/liter solution of sodium carbonate (Fitzwater et al., 1982).
Samples were incubated from LAN to civil twilight in seawater-cooled
incubators with neutral-density screens which simulate in situ
light levels. At the end of the
incubation, the samples were filtered onto Millipore HA filters and placed in
scintillation vials. One half ml of 10%
HCl was added to each sample. The sample
was then allowed to sit, without a cap, at room temperature for 12 hours (after
Lean and Burnison, 1979). Following this,
10 ml of scintillation cocktail were added to each sample and the samples were
returned to SIO where the radioactivity was determined with a scintillation
counter. Salinity, oxygen, nutrients,
chlorophyll-a and phaeopigments were determined from
all rosette productivity bottles.
Macrozooplankton Net Tows
Macrozooplankton was sampled with a 71 cm
mouth diameter paired net (bongo net) equipped with 0.505mm plankton mesh. Bottom depth permitting, the nets were towed
obliquely from 210 meters to the surface.
The tow time for a standard tow was 21.5 minutes. Volumes filtered were determined from
flowmeter readings and the mouth area of the net. Only one sample of each pair was retained and
preserved. The biomass, as wet
displacement volume, after removal of large (>5 ml) organisms, was
determined in the laboratory ashore.
These procedures are summarized in greater detail in Kramer et al. (1972). An
Optical Plankton Counter (OPC, Dave Checkley, SIO) was routinely used in one
side of the paired bongo net frame. The
purpose of the OPC is to obtain information on the vertical distributions of
size categories of zooplankton, using data from the counter, without affecting
the ongoing time series of data obtained from the catches of the integrative
bongo net.
Avifauna Observations (Point Reys
Bird Observatory)
Sea birds were counted within a 300-meter wide strip
off to one side of the ship. Counts were
made while underway between stations during periods of daylight. These counts were summed over 20 nautical
mile (nm) intervals, or the distance between consecutive stations, whichever
was less. Included at the end of this
report are individual maps of the most numerous bird species (individuals/nm).
Ancillary Programs
Several ancillary programs produced data on
these cruises that are not presented in this report. These programs include:
1) Underway Data. Continuous near surface measurements of
temperature, salinity and in vivo
chlorophyll fluorescence were recorded from seawater pumped through the ship’s
uncontaminated seawater system. Water
was drawn from a depth of approximately 3 meters. The data were logged in one-minute averages
using a Sea-Bird Electronics, Inc., SBE 45 MicroTSG Thermosalinograph and a
Wetlabs Wetstar fluorometer.
2) ADCP. Continuous profiles of ocean currents and
acoustic backscatter between 20 and 500 meters deep were measured along the
shiptrack from a hull-mounted 150 kHz Acoustic Doppler Current Profiler (ADCP).
The ADCP data were averaged over 3-minute intervals. Sixty 8-meter depth bins
were recorded. (T. Chereskin, SIO)
3) Underway
Sea Surface xCO2. Continuous measurements of the partial pressure of
CO2 were made from the ship's uncontaminated seawater system. The seawater was
equilibrated in a membrane contactor with a gas loop that was analyzed with a
Licor 6262 infrared CO2/H2O analyzer. One-minute averages were recorded and the
mole fraction of CO2 (xCO2) at sea surface temperature was calculated. The
system was calibrated with standard gases traceable to CMDL every two hours; at
that time absolute zero and atmospheric samples were also collected.
(G. Friederich, MBARI)
4) Taxon-specific pigments:
Water samples were collected from a depth of 10 m for the analysis of
taxon-specific pigments (chlorophylls and carotenoids) by high-pressure liquid
chromatography. (R. Goericke, SIO)
TABULATED DATA
CTD/Rosette Cast Data
The time reported is the Coordinated Universal Time (UTC) of the first rosette bottle trip on the up cast. The rosette bottles tripped on the up cast are reported as cast 2, where cast 1 is considered to be the down CTD profile. The sample number reported is the cast number followed by a two-digit rosette bottle number. Bottom depths, determined acoustically, have been corrected using British Admiralty Tables (Carter, 1980) and are reported in meters. Weather conditions have been coded using WMO code 4501. Secchi depths are reported for most daylight stations.
Data values from discreet sampled CTD rosette were interpolated and are reported for standard depths. Interpolated or extrapolated standard level data are noted by the footnote “ISL” printed after the depth. Multiple bottles tripped at the same depth to provide water for ancillary programs are not used in the calculation of standard depth data. Density-related parameters have been calculated from the International Equation of State of Seawater 1980 (UNESCO, 1981b). Computed values of potential temperature, sigma-theta, specific volume anomaly (SVA), and dynamic height or geopotential anomaly are included with both observed and interpolated standard depth levels.
On stations where primary productivity samples were drawn a footnote appears after each productivity depth sampled. The corresponding primary productivity data are reported in a separate section following the tabulated rosette cast data.
Primary Productivity Data
In addition to the normal hydrographic data
that are reported in the rosette cast data section, the tabulated data include:
the in situ light levels at which the
samples were collected, the uptake from each of the replicate light bottles,
uptake 1 and uptake 2 (which have been corrected for dark uptake by subtracting
the dark value), the mean of the two uptake values and the dark uptake. The uptake values are totals for the
incubation period. Also shown are the
times of LAN, civil twilight, and the value of the mean uptake integrated from
the surface to the deepest sample, assuming the shallowest value continues to
the surface and that negative values (when dark uptake exceeds light uptake)
are zero. The uptake data are reported
to two significant digits (values <1.00) or one decimal (values >1.00). Incubation time, LAN, and civil twilight are
given in local Pacific Standard Time (PST); to convert to UTC, add eight hours
to the PST time. Incubation light
intensities are listed in a footnote at the bottom of each page.
Macrozooplankton Data
Macrozooplankton biomass volumes are
tabulated as total biomass volume (cm3/1000m3 strained) and as the total volume minus the volume of
larger organisms under the heading “Small.”
Tow times are given in local PST (+8) time.
FOOTNOTES
In addition to footnotes,
special notations are used without footnotes because the meaning is always the
same:
D:
CTD salinity value listed in place of normal shipboard salinity
analysis.
ISL: After a depth value indicates that this is an
interpolated or extrapolated standard level.
U:
Uncertain value. Values which are
not used in interpolation because they seem to be in error without
apparent reason.