THE GENUS CERATIUM IN THE PACIFIC AND 

 NORTH ATLANTIC OCEANS 



INTRODUCTION 



The present paper, which constitutes a part of the 

 Carnegie plankton reports, deals only with the one peri- 

 dinian — (dinoflagellate) genus Ceratium. This genus 

 consists of a large number of species of which many are 

 very common and widespread marine forms. They con- 

 stitute a characteristic and often dominant part of the 

 planktonic community. The present report deals with 

 fifty-eight species, which comprise all but one or two of 

 the known marine forms as well as three new species. 



Because of their constant participation in the ma- 

 rine phytoplankton, the Ceratia have of late been given 

 considerable attention in general oceanographic re- 

 searches. Thus, Peters (1934) has investigated the dis- 

 tribution and biology of the Ceratia collected by the Me- 

 teor during its Intensive oceanographic investigation of 

 the South Atlantic Ocean in 1925 to 1927 and Nielsen 

 (1934) has done likewise for the collections of the Dana 

 made in the SouthPacific during 1928 to 1930. The pres- 

 ent collections are unique in their extensive nature, 

 bringing together comparable material from widely sep- 

 arated regions of the Pacific and North Atlantic oceans. 



In the Atlantic the stations extended along the Gulf 



Stream or North Atlantic West Wind Drift, in the North 

 Sea, in the arctic currents about Iceland and Greenland, 

 and In the Labrador Current. There is also a line ex- 

 tending through the Sargasso Sea to the North Equatorial 

 Current and Equatorial Countercurrent. From here 

 there are stations running along the former current and 

 into the Caribbean Sea. 



In the Pacific the collections are even more exten- 

 sive. There are two lines crossing the equatorial cur- 

 rents; one in the central Pacific between longitudes 140° 

 and 150° west, the other west of this at about longitude 

 175° west. Tropical stations in the North Pacific are 

 scattered widely over the east and west parts; north of 

 the Marshall Islands, between Guam and Japan; between 

 the United States and Hawaii; and north and south of Ha- 

 waii. In the South Pacific there is a line of stations in a 

 region of indefinite currents between Peru and Samoa. 

 There are stations from Peru southeastward at 40° south 

 latitude and north to Easter Island. Other stations are 

 in the region of the Galapagos Islands and the Panamic 

 area. 



THE HYDROGRAPHY OF THE REGIONS INVESTIGATED 



Currents 



North Atlantic Ocean. --The central part of the North 

 Atlantic s»irface water consists of a huge vortex running 

 clockwise. The southern part of this circuit is repre- 

 sented by the North Equatorial Current which has a west- 

 erly course and is composed of water of high temperature 

 and low nutrient content. This current merges with the 

 Florida Current which has a northerly set off the east 

 coast of the United States. It, too, is composed of warm, 

 nutrient-poor water. This current, in turn, becomes the 

 North Atlantic West Wind Drift which flows eastward to 

 the coast of Europe. This current loses its tropical 

 characteristics as it progresses, becoming colder and 

 richer in nutrient salts. When it reaches Europe, some 

 of this water is deflected to the south to join the North 

 Equatorial Current, and thus to resume the circuit; 

 other parts continue northeastward around the British 

 Isles and finally into the Arctic Ocean. To the north of 

 the West Wind Drift there -is a general movement of arc- 

 tic water southward, more specifically in the form of the 

 Greenland Current and the Labrador Cvirrent. This cold, 

 nutrient-rich water meets the warm water to the south 

 at the polar front (subpolar convergence) which lies at 

 about latitude 40° north off the coast of America, and 

 from there extends west northwestward (see chart 50). 

 The surface temperatures at this convergence drop sud- 

 denly from 21° to 11° C. K should also be noted that 



within the North Atlantic West Wind Drift there is a 

 sudden drop in temperature and increase in nutrients at 

 about 40° west longitude. Although the Carnegie stations 

 are rather widely separated in this region, the change is 

 striking, with a surface temperature of 21.°18 recorded 

 at station 14 and 15.°50 at station 3. Similarly the phos- 

 phate content of the upper 50 meters increased from 14 

 to 64 mg P04/m3. In addition to the above stations there 

 were four stations in the Caribbean Sea. The water here 

 was the warmest of any Atlantic region visited, with tem- 

 peratures all above 28° C, and it was practically devoid 

 of phosphate. 



North Pacific Ocean . - -The main body of the North 

 Pacific is involved in a clockwise rotation similar to that 

 in the North Atlantic although it is modified by the differ- 

 ent configuration of the continents. The North Equatorial 

 Current is well developed; itsmiddle part is about at 10° 

 north latitude. It is warm, poor in nutrients, and has 

 temperatures as high as 29.°5 C. This current turns 

 northward off the Asiatic coast where it is known as the 

 Kuroshio Current, just as the corresponding current of 

 the Atlantic becomes the Florida Current. The Kuroshio 

 is warm and poor In nutrients. The waters of this cur- 

 rent turn eastward and flow south of the Aleutian Islands 

 as the North Pacific West Wind Drift. The waters now, 

 howevei , are cold and rich in nutrients, with surface 

 temperatures around 8° C, and the phosphate content of 

 the upper 50 meters is over 100 mg P04/ni3. These 



