Nutrient Distribution Along the Labrador and Baffin Island 



Coast, 1965 



David A. McGill and Nathaniel Corwin ^ 

 Woods Hole Oceanographic Institution, Woods Hole, Mass. 



Interest in the oceanographic conditions of the 

 Labrador Sea has greatly intensified in recent 

 years, as the important relationship of this area 

 to the western North Atlantic has been demon- 

 strated. For many years the standard section 

 from South "\A'olf Island, Labrador to Cape Fare- 

 well, Greenland has been occupied by the U.S. 

 Coast Guard in a post season cruise by the Ice 

 Patrol. Analysis of this section has shown the 

 presence of coastal currents near Labrador with 

 markedly different characteristics from the off- 

 shore water masses. The nutrient chemistry of 

 tins standard section has been examined by the 

 present autliors in recent years and show a similar 

 abrupt transition between the coastal and offshore 

 conditions. Wliile recent Soviet research reports 

 (VNIRO-PINRO, 1960; 1962) have given in- 

 formation on the chemistry and biology of the 

 region south of the standard section along the 

 Newfoundland coast and banks, details on the 

 coastal conditions in northern Labrador and Baf- 

 fin Island have been lacking. Accordingly, the 

 1965 post season Ice Patrol survey was planned to 

 provide data on coastal sections from South Wolf 

 Island, Labrador to the margin of the Baffin Sea 

 basin. The report on the nutrient chemistry for 

 the coastal waters surveyed which is given here 

 greatly augments the available observations, 

 especially in the Hudson Strait and Ungava Bay 

 area, which has been previously little studied 

 (Dunbar, 1951). 



METHODS 



The analytical techniques have been given in 

 previous reports, especially McGill and Corwin 

 (1965) where references to individual methods 

 may be found. Frozen samples collected during 

 the Ice Patrol Post Season Survey were stored 

 until analysis could be undertaken in Woods Hole. 



'Contribution No. 1838 form the Woods Hole Oceanographic 

 Institution. This work was supported in part by the Office of 

 Naval Research under contract Nonr-2196(00) NR-083-004. 



The assistance of John Schilling and Mrs. Juanita 

 Mogardo is again gratefully acknowledged. The 

 nutrient data are published in this volume along 

 with the other observations at each station. Since 

 relatively little detail exists in the contours of 

 these sections due to the greatly restricted depths 

 along the continental shelf, profiles of all the dis- 

 tributions are not given. Only the nitrite- 

 nitrogen profiles are shown and the significance 

 of these is discussed below. The other distribution 

 patterns are described verbally. The locations of 

 the sections mentioned are shown on the inset maps 

 accompanying figures 1 and 2. 



DISTRIBUTION OF NUTRIENTS 



Inoi-ganic phosphate-phosphorus values near 0.5 

 f«gA/l at the surface along the cost occur through- 

 out the area. In the southern sections, the surface 

 phosphate concentration decreases at the offshore 

 extremity to values near 0.20 /igA/1. A concen- 

 tration of 1.00 MgA/1 is reached near a depth of 200 

 meters in all sections. Along the continental slope 

 in deep water the phosphate level increases to about 

 1.10 /xgA/1. Sections A, B, and C— south of Hud- 

 son Strait — show a value of about 0.90 ftgA/l at 

 100 meters on the continental shelf. This general 

 pattern also occurs in section D across the mouth of 

 Hudson Strait. The small decline in surface 

 values at stations 9455-9457 (at the northern end 

 of the section) relative to the remainder of the sec- 

 tion may possibly indicate the westward-moving 

 inflow to the Hudson Strait. Section D' repre- 

 senting Ungava Bay (see map) has relatively high 

 phosphate concentrations : 1.00 /ligA/l occurs near 

 100 meters and occupies the remainder of the basin 

 except where a near-shore current is suggested at 

 stations 9463. Sections E and F are generally 

 similar to section D. In section G a bubble of 

 phosphate greater than 1.00 /xgA/1 is found at 

 about 50 meters and this may represent the outflow 

 from Davis Strait in a current moving southwest- 

 ward toward the coast after exchanges with Baffin 



35 



