INTRODUCTION
The data
presented in this report were collected during cruise 0607*
of the California Cooperative Oceanic Fisheries Investigations (CalCOFI)
program aboard the RV New Horizon 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 P144. 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 by the Scripps Ocean Data Facility for dissolved silicate, phosphate, nitrate, nitrite, and ammonium using procedures similar to those described in Gordon et al. (1993) and Koroleff (1969, 1970). 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 63.10 µCi of 14C as NaHCO3 (200
µl of 335.90 µCi/ml stock) prepared in a 0.3 g/liter solution of sodium
carbonate (Fitzwater et al.,
1982). An adjustment to the specific
activity was made to account for the 10 ml aliquot removed for DOC-14 analysis
on CCE-LTER samples. 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 diffusion chamber that was then
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) California
Current Ecosystem Long Term Ecological Research Program: The CCE-LTER
program augments standard CalCOFI measurements to further characterize the
lower trophic levels as well as the carbon system. These additional samples, taken at all
CalCOFI stations, are for measurements of particulate organic carbon and
nitrogen, dissolved organic carbon and nitrogen, taxon-specific phytoplankton
pigments, flow-cytometric counts of bacteria and picoautotrophs, microscopic
counts of nano- microplankton, determination of mesozooplankton size structure
using a Laser Optical Plankton Counter, and mesozooplankton community
structure. (M. Ohman, SIO)
5) SCCOOS
Nearshore and Bio-optical Observations: The
objective of these observations is to extend CalCOFI time series to the
nearshore and make bio-optical observations for the development of empirical
proxies for particle size load and structure and phytoplankton biomass and
rates of primary production. The
nearshore observations consist of 9 stations at the ends and interspersed with
current CalCOFI lines on the 20 m isobath with a standard set of CalCOFI
observations. Bio-optical measurements
at all CalCOFI and SCCOOS stations consist of irradiance at 9 wavelengths,
light transmission at three wavelengths, fluorescence of Chl a, CDOM and
phycoerythrin and light scattering at three wavelengths.
6) Bio-optics. Spectral
radiometry of the top 100 meters of the water column were measured daily with a
multi-spectral free fall radiometer (PRR-800, Biospherical). Water
samples obtained from the CTD/rosette cast were analyzed for determination of
absorption by particulate, detrital materials, and algal HPLC pigments.
(G. Mitchell, SIO)
7) Marine mammal observations. During daylight transits, visual line-transect
surveys were conducted by marine mammal observers focusing on
cetaceans. Acoustic line-transect surveys were performed
using a towed hydrophone array which consists of multiple hydrophone elements
that sample sounds up to 100 kHz allowing for localization of calling
animals. Acoustic monitoring also takes place on individual stations
using sonobuoys.
(J. Hildebrand, SIO)
8) O2 Isotopes. Water samples were collected at 38 stations for analysis of isotopic composition of dissolved oxygen to assess in situ primary production rates and compare with CalCOFI 14-C primary production. Isotopic analysis was performed at the University of Washington
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.