Hydrography and distribution of chaetognaths over the continental shelf off North Carolina 1 1 



5148 5149 5150 5151 



' ^ I I 



5152 515 3 STA NBR 5154 



Fig. 9. (A) Distribution of temperature in ° C, (B) salinity in ''/^^ and (C) density (o,), in Section VIII, 



Long Bay, January 1954. 



along the continental slope. During other parts of Caryn Cruise 64, the position of 

 maximum current was observed to shift as much as 14 miles either side of the mean 

 axis of flow (which off Onslow Bay normally lies about 18 miles south-east of the 100 

 fathom line. Associated with these shifts of position were onshore and offshore 

 deflections in the direction of the current (von Arx, Bumpus and Richardson, 1955). 

 This provides the energy to push water up the slope across the shelf. It also appears 

 from salinity measurements that as the meanders move offshore they draw low salinity 

 water (from the surface over the shelf) into the current. 



The proximity of the Florida Current to the continental shelf precludes the occur- 

 rence (between the Current and the Carolinian coastal water) of slope water such as is 

 found north-east of Cape Hatteras between the continental shelf and the Gulf Stream. 



DISTRIBUTION OF THE CHAETOGNATHS 

 The chaetognaths collected in this area include 12 species representing three genera: 

 Sagitta bipunctata, S. enflata, S. helenae, S. hexaptera, S. hispida, S. lyra, S. minima, 

 S. serratodentata, S. tenuis, Krohnitta pacifica, K. subtilis, and Pterosagitta draco. 



The quantitative composition of the plankton tows is recorded (Tables 1 and ID. 

 The species are listed in the order of their association with water of low or high salinity 

 from left to right. The stations are arranged in the order of distance from the coa^.t. 

 The ranges of individual species overlap others considerably and in many cases 

 completely. Nevertheless the tables show that there is a general correlation between 

 salinity tolerance and the distance from the coast at which various species were found. 

 The most euryhaline-^urythermal species was 5". enflata (Pierce, 1953), although 

 it is doubtful if it can tolerate for long periods salinities as low as those in which 

 5. hispida are usually found. S. hispida, S. helenae, and S. tenuis are species which are 

 largely restricted to water of the continental shelf below Hatteras. The remainder o^ 



