WHP Line No.: PR6
Last Updated: January 28, 1997

CRUISE REPORT: Repeat Hydrography on Line PR6:
WOCE Cruise No. 18DD9512/1

Chief Scientist: Phil Boyd 
Ship: John P. Tully
Ports of Call:  none
Cruise Dates: August 22 to September 13, 1995
Expedition Designation: 18DD9512/1

Cruise Narrative
Our repeat hydrography section was a joint program with Canadian JGOFS.

A full CTD survey along Line PR6 to a depth of 3000 m was completed ,
with CTD casts at 29 stations and rosette/hydro casts at 10 stations.
Two additional surveys were conducted: a sawtooth survey to the N and S
of Line P (up to 20 miles) from P26 to P19 involving underway sampling
only, and a hydrographic survey from P19 to P12 involving both underway
and CTD sampling.   Salinity, oxygen and nutrients (NO3 & NO2, PO4 and
Si) were analyzed onboard ship.

A bio-optical mooring was deployed at Stn. PRS1 to assess temporal
changes in phytoplankton biomass and production in relation to the
mixed layer depth and PAR.  The mooring was placed to within 2-3 m of
its theoretical position.

JGOFS participants collected samples at 5 stations for abundance and
activities of bacteria, phytoplankton, micro- and meso-zooplankton and
incubated water to measure growth and grazing rates of various groups
of plankton.  The natural abundance of stable isotopes (15N and 13C) in
suspended particulate matter was determined along Line P.

Cruise Summary Information
Cruise track
Line PR6 starts at the mouth of Juan de Fuca Strait on the west coast
of Canada, and heads almost due west for 900 n mi.  The terminal
station is PRS1, formerly designated Ocean Weather Station Papa (50 N,
145 W).

Table of Stations by type

Sample type:
No. stations:
Max. depth (m):

CTD casts
29
3007 db 

Rosette/Hydro casts
10
3862 

Loop samples
30
5

Mooring
1


Profiling Alace float
1
800 m


Floats and Drifters deployed
A profiling Alace float was deployed at station PRS1.


Principal Investigators  
Howard Freeland
Ocean circulation 
IOS

C.S. Wong
Climate chemistry
IOS

Frank Whitney
WOCE coordinator
IOS

Philip Boyd
JGOFS coordinator
UBC


Preliminary Results

A diatom patch was noticed in the vicinity of station P20, eliciting
increased sampling in this area.

The temperature and salinity structure along Line PR6 define several regions:
1.   very near the coast, cooler more saline waters are upwelled as
previously described by Freeland and others.
2.  two lenses of warm, low salinity water between P4 & 10, and P15 &
18 have different characteristics.  The near shore pool with salinity
less than 32 psu is restricted to the upper 20 m.  Further offshore,
fresh water appears to be mixed deeper but the mixed layer is thermally
confined to the upper 20 m;
3.  beyond P20, salinity increases abruptly by 0.2 psu at the surface
and remains fairly uniform out to P26.  The mixed layer deepens to 30m.
 
  
Transmissivity is a good indicator of phytoplankton density (data
collected at P2, 4, 12- 20, 24 and 26).  Although this data is sparser
than T and S, regions with increased biomass can still be defined as:
1.  upwelling near the coast which increases nutrient supply;
2.  subsurface chlorophyll maximum between P4 and 12, which is formed
by a nutricline below the nitrate depleted surface layer (trans. data
only at P4 and 12); 3.  a break in the subsurface chlorophyll layer
coincident with a doming in salinity at P13;
4.  a second subsurface chlorophyll layer from P15 to 19, which is also
a region where a persistent current from the north (at P16) was notice
by the ship as it tried to hold station, and;
5.  a region of high surface biomass seen at P20, followed by an increase in 
transmissivity towards P26.  Nitrate is found in surface waters from P18, westward.

The two dominant features of biomass distribution apparently are
nutrient supply and stratification.

Goals Achieved
CTD survey of Line PR6. 
Successful Rosette casts at 10 stations on Line P.
Completion of JGOFS sampling for plankton and productivity
measurements.  A mooring with an optical package and S4 current meter,
both in the mixed layer, was deployed.


Problems and Goals not Achieved

The Alaskan Gyre component of the cruise was canceled in order to study
the higher than normal abundance of large diatoms observed at Stn.
P20.

Cruise Participants & Affiliations

Phil Boyd
Chief scientist
UBC

Reg Bigham
 Watch, mooring
IOS

John Love
Salts, watch
IOS

Wendy Richardson
Oxygen, watch
IOS

Ron Bellegay
Watch, carbonates
IOS

Janet Barwell-Clarke
Nutrients, FD*, prod. expt.
IOS

Ou-Jin Jeong
mooring observer
IOS

Robert Goldblatt
Zooplankton biomass
UBC

Hugh Maclean
Watch, plankton sampling
UBC

Maureen Soon
particulate 13C & 15N
UBC

Michael Lipsen
bacteria enumeration 
UBC

Delphine Thibault
Zooplankton excretion
Rimouski U.

Ken Crocker
Zooplankton grazing
Memorial U.

Jennifer Putland
Micro-zooplankton
Memorial U.

Paul Matthews
bacterial productivity
Memorial U.

Neil Price
Fe uptake
McGill

Maite Maldonado
bacteria respiration & 
production
McGill

IOS = Institute of Ocean Sciences, Sidney, B.C., Canada.
UBC = University of British Columbia, Vancouver, B.C., Canada

Measurement Techniques and Calibrations

CTD profiles
	At all stations, a Guildline 8715 CTD coupled with
	transmissometer was lowered to a maximum 3007 m.

Water sampling
	A rosette holding a Guildline 8737 CTD and 23-10 L
	polycarbonate Niskin bottles was used for most water sampling.
Go-Flo bottles clamped on Kevlar hydro line were used to collect clean
water for plankton studies.
 
	Each rosette/hydro station consisted of two casts - a down cast
	and an up cast.  The CTD profile is taken from the down cast.
The bottles were tripped on the up cast and CTD pressure (dbar) and CTD
temperature (uncorrected) recorded from this upcast.
	At each station, samples for surface chlorophyll, salinity and nutrients were collected from the ship's sea water loop which pumps water from
about 5 m continuously into the laboratory.
 


Salinity
	Samples were collected in glass bottles and analyzed onboard
	ship using a Guildline Model 8410 Portasal.  The Portasal was
standardized daily with IAPSO standard sea water.

Oxygen 
	An automated titration system (Brinkman Dosimat and Fiber Optic
	Probe Colorimeter) using the micro-Winkler method (Carpenter,
1965), titrated samples to the iodine end-point.  Standards were
prepared as outlined in WOCE Report 73/91.
  

Nutrients
	Samples from hydro casts were collected in polystyrene tubes
	and refrigerated for a maximum of 12 h before being analyzed.
Loop samples (USW) were stored up to 2 days at 4oC before being
analyzed.  NO3+NO2, PO4 and Si were analyzed using a Technicon
Autoanalyzer.
	NO3+NO2 samples were reduced with Cd/Cu, then complexed with
sulfanilamide and N-Naphthylethylene-diamine to form an azo dye
(Technicon Method No. 158-71W/B).  PO4 produces a molybdenum blue
complex in presence of acidic molybdate and ascorbic acid (Technicon
Method No. 155-71W).  Dissolved Si also forms a molybdenum blue complex
and oxalic acid removes PO4 interference (Technicon Method 186-72W).
	Concentrated standards were freshly prepared the week before
	the cruise from oven dried reagents.  Working standards were
made every 1 to 2 days by diluting 1 to 6 mL of various stock solutions
to 250 mL with 3.2% NaCl (w/v in double run Milli-Q water).

Table.  Laboratory temperatures for nutrients.

Date
Temp (C)
Date
Temp (C)

Aug 24
23.8
Sept. 1
23.5 to 25.9

Aug 27
23.0 to 25.1
Sept. 2
20.0

Aug 28
24.2
Sept. 3
23.4 to 24.3

Aug 31
24.1 to 24.8
Sept. 8
20.6 to 21.8



TCO2, 13C and Alkalinity - a single profile was collected at PRS1.
Samples were fixed with HgCl2 and refrigerated.

O18/O16 - samples were collected in 60 mL polyethylene bottles and refrigerated.

JGOFS sampling -  Go-flo bottles were used to collect water for POC/N,
DOC/N, chlorophyll, nano- and micro-plankton and incubation
experiments.  Deck incubations were conducted to measure growth rates
of bacteria, phytoplankton and micro- zooplankton.

	Sp FOR SALINITY, OXYGEN, AND NUTRIENTS
	
	Duplicate samples came from Niskin bottles tripped within  1.3 m of each other.  

Parameter
Depth Range (m)
Conc. Range
Sp

Salinity
10 to 3712
32.2 to 34.7
0.0044 (k=23)

Oxygen
10 to 3712
63.7 to 280.0 uM/kg
1.09 (k=22)

Silicate
10 to 3712
10.0 to 171uM/kg
0.42 (k=16)

Nitrate + Nitrite
10 to 3712
0.0 to 41.8 uM/kg
0.22 (k=16)

Phosphate
10 to 3712
0.34 to 2.95
0.017 (k=16)


Where the standard deviation of pairs Sp = {(sum d2)2k}1/2, d is the
difference between pairs, and k is the number of pairs.


References

Carpenter, J.H.  1965. The Chesapeake Bay Institute technique for the Winkler 
dissolved oxygen method.  Limnol. Oceanogr., 10: 141-143.

Technicon Industrial Method No. 155-71W.  1973.  Orthophosphate in water and 
seawater. 

Technicon Industrial Method No. 158-71W/A.  1977.  Nitrate and nitrite in water and 
seawater. 

Technicon Industrial Method No. 186-72W/B.  1977.  Silicates in water and seawater.

WOCE Report 73/91.  1991.  A comparison of methods for the determination of 
dissolved oxygen in seawater.

