BEERS ET AL,: PLANKTON AND UPWELLING OFF PERU 



Our purpose was to return to the same patch of 

 water, sampling it on successive days as it 

 "evolved." In general, the temperature and 

 fluorescence of the surface water were used to 

 determine the desired location of sampling after 

 the navigational capabilities of the ship had been 

 used to locate the general area. 



Physical measurements, i.e., temperature and 

 salinity, were either by continuous vertical pro- 

 files generally from the surface to the bottom, 

 or 500 m, using a STD (Salinity-Temperature- 

 Depth Measuring System, The Bissett-Berman 

 Corp. Model 940) "■ or at the surface (3 m) using 

 a thermo-salinograph (The Bissett-Berman 

 Corp. Model 6600T). Both systems were elec- 

 tronically interfaced to a shipboard IBM 1800 

 computer. 



Vertical profiles of cun-ent velocity were made 

 at Stations 99 and 101 using a Hydro Products, 

 Model 502, meter having a precision Savonius 

 rotor to sense current speed and a direction vane 

 coupled with a magnetic compass. The instru- 

 ment, lowered on the hydrowire, measured the 

 currents for 15 min at each of a series of depths 

 through the upper 200 or 500 m. At each station 

 the current direction and speed were referenced 

 to the deepest observation. The lower practical 

 current threshold is considered to be about 2.5 

 cm/sec. 



Phytoplankton nutrient concentrations (i.e., 

 PO4, NO3 + NO2, and SiO:i) in water from the 

 surface pump or taken by water bottles from 

 various depths were determined using an Auto- 

 analyzer and methods described in Strickland 

 and Parsons (1968). A Turner fluorometer 

 with a continuous flow-through cell (Lorenzen, 

 1966) was used for mapping surface phyto- 

 plankton pigment distribution. Vertical profiles 

 of extracted chlorophyll and phaeophytin were 

 done following the procedure of Holm-Hansen 

 et al. (1965). 



Levels of primary production through the 

 euphotic zone were measured by the radiocar- 

 bonate uptake method at seven stations (see 

 Table 3). Stations 59, 68, 77, and 87 were 

 associated with Patch 1 while Stations 88, 93, and 



° The use of trade names is merely to facilitate de- 

 scriptions; no endorsement is implied. 



99 were in the second mass of upwelled water 

 (Patch 2) followed. Water was collected by 

 Van Dorn bottles from depths corresponding to 

 80, 30, 20, 15, 5, and 1.5^; of the surface irra- 

 diance at each location. These depths were es- 

 timated from Secchi disc depths. Incubation of 

 samples in deck incubators cooled by surface 

 seawater was for 6 (noon to sunset) or 24 hr. 



At each site where primary production was 

 measured, water samples were taken for anal- 

 ysis by the inverted microscope method of Uter- 

 mohl (1958) of the phytoplankton species com- 

 position, numerical abundance, and estimates of 

 biomass (volume and organic carbon). Gener- 

 ally aliquots from the several depths sampled at 

 each site were integrated to provide a composite 

 sample over the euphotic zone, preserved with 

 5^; Formalin (pH 8.2 it 0.2), and studied as 

 described in University of California, Institute 

 of Marine Resources (1971, see footnote 4) and 

 Reid, Fuglister, and Jordan (1970). 



Unconcentrated samples for study of the cil- 

 iate populations were taken along with the phy- 

 toplankton as above. In addition, the ciliates 

 of the euphotic zone were studied at eight addi- 

 tional sites where the larger zooplankton abun- 

 dance was measured and they were also deter- 

 mined in integrated samples from depth inter- 

 vals, generally 20 to 30 m sampled at 5-m 

 intervals, below the photosynthetic compen- 

 sation point (1.5';r surface irradiance) at 10 

 stations. 



Samples of the microzooplankton populations 

 concentrated on 35-/u, mesh cloth after excluding 

 larger material on 202-;tt mesh filters were col- 

 lected from the surface (3 m) using the intake 

 in the ship's hull at most stations where biologi- 

 cal sampling was carried out and during certain 

 of the mapping operations. These samples pro- 

 vided material for study of all microzooplankton 

 groups other than the ciliates, many of which 

 are too small to be retained by this size mesh. 

 An unconcentrated pump sample taken for total 

 ciliates is not considered here as there were in- 

 dications the pump was damaging the non-lori- 

 cate forms. Methods of analysis of the total 

 microzooplankton and ciliate populations includ- 

 ing conversion from a volume estimate to or- 

 ganic carbon are given in Beers and Stewart 



861 



