FISHERY BULLETIN: VOL. 76, NO. 2 



crop, primary productivity, and w^ater tempera- 

 ture, and to explore the significance of ring 

 biomass distribution. 



METHODS 



The major portion of the data to be presented in 

 this paper w^as collected on RV Chain cruise 125 

 (August 1975) and on RV Knorr cruise 53 

 (November 1975). The ring sampled (designated 

 Ring-D by the Naval Oceanographic Office), was 

 formed in February 1975. It was, therefore, about 

 6 mo old when first sampled and 9 mo old when 

 sampled again in November. In November the 

 slope water was hydrographically complex. It is 

 likely that some of our intended slope water tows 

 (MOC 39 and MOC 40) may have been taken in the 

 vicinity of a warm core ring (Saunders 1971). The 

 upper 200 m of the water column at that station 

 was warmer and more saline than is typical for the 

 slope water. In addition, infrared satellite photo- 

 graphs clearly show the presence of this warm ring 

 during the period of sampling. Other slope water 

 stations may have been influenced by the passage 

 of a warm core ring. In analyzing the data, MOC 

 39 and 40 are considered separately and desig- 

 nated warm core ring tows. Data corroborating 

 specific points or conclusions have been drawn 

 from collections made on KV Atlantis cruise 71, 

 RV Chain cruise 1 11, and RVif/iorr cruises 35 and 

 38 (Table 1). 



Collections in Gulf Stream cold core rings, the 

 northern Sargasso Sea, and slope water were 

 made with three types of sampling gear: on the 

 early cruises 1-m diameter ring nets or modified 

 opening/closing 70-cm diameter bongo nets 

 (McGowan and Brown 1966), on the two most re- 

 cent cruises a multiple opening/closing net and 

 environmental sensing system — MOCNESS 



(Wiebe, Burt, Boyd, and Morton 1976)— with a 

 mouth area of 1 m x 1.4 m (effective area is 1 m^). 

 All nets were constructed from 0.333-mm Nitex^ 

 gauze; depth recorders and flow meters were used 

 on all tows. 



The 1-m nets were hauled obliquely, ideally to a 

 depth of 800 m. On some cruises a second haul was 

 taken to a depth of 300 m. Bongo nets were towed 

 obliquely within the depth intervals 0-250, 250- 

 500, and 500-750 m. With occasional exceptions, 

 the MOCNESS sampled both from 800 m to the 

 surface in 100-m intervals, and from 200 m to the 

 surface in 25-m intervals. Sampling with 1-m and 

 bongo nets was almost always done at night, while 

 at most MOCNESS stations samples were taken 

 both day and night. The types of tows taken on the 

 five cruises are given in Table 1. All samples were 

 preserved in 5-10% Formalin buffered to pH 8.0 

 with sodium tetraborate. In the vicinity of all 

 plankton hauls, hydrographic casts were made 

 yielding nearly concomitant vertical profiles of 

 temperature, salinity, oxygen, chlorophyll, nu- 

 trients, primary productivity, and phytoplankton 

 species (see Wiebe, Hulburt, Carpenter, Jahn, 

 Knapp, Boyd, Ortner, and Cox 1976 for methods). 



Zooplankton biomass was measured by the 

 method of Ahlstrom and Thrailkill (1963) after 

 removal of all organisms greater than 5 cm^. Dis- 

 placement volumes were measured 5 to 9 wk after 

 a cruise. No attempt has been made in this paper 

 to partition the biomass according to taxa. The 

 species composition of those samples already 

 examined appears similar to that reported for the 

 region by Grice and Hart (1962), Deevey (1971), 

 and Deevey and Brooks (1971). 



^Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



Table l. — Summary of slope water, ring, and Sargasso Sea zooplankton sample stations. 



'Positions of stations Illustrated in Wiebe, Hulburt, Carpenter, Jatin, Knapp, Boyd, Ortner, and Cox (1976) 



^Sargasso Sea; MOC 1,2 (35°37', 68°3r), MOC 3,4 (35°22', 68°17'), MOC 12 (34°ir, 7r40'), MOC 13,14,15 (34°10', 7r34'); 

 ring: MOC 5,11 (34°29' 69°56'), MOC 6,7 (34°34', 69°52'), MOC 8 (34°31', 69°49'), MOC 10 (34°33'. 69°53'); slope water: MOC 16,17 

 (38°02', 69°59'), MOC 18,19 (38°05'.70°02'), MOC 20,21 (39°05', 70°12').AII positions are north latitude and west lonaitude, 



^Sargasso Sea: MOC 23,24,25 (-32"44', 71°10'), MOC 26 (32°52', 7r08'), MOC 34 (34"12', 70°30'); ring: MOC 27, 28, 29 (33°49', 

 7r54'), MOC 31 (35°50', 7r48'), MOC 32 (33°56', 71 °54'), MOC 33 (34°03', 71 °56'): warm core nng: MOC 39,40 (40°04', 68°05'): slope 

 water: MOC 35,36 (38°51 ', 67°47'), MOC 37,38 (38°55', 67°46'), MOC 41,42 (39°59', 69°00). All positions are nortti latitude and west 

 longitude. 



324 



