NO. 9 MARINE INVERTEBRATES, ALASKA — MacGINITIE 2^ 



the Arctic such larvae or even small to adult animals may be pushed 

 many yards by ground ice. To a depth of lOO feet or more in the 

 bottom off Point Barrow there are holes (that have been gouged out 

 by ice) 6 feet or more below the surrounding bottom level. Although 

 they are uncommon off Barrow, icebergs (pi. 7) grind and shove 

 material along the bottom for a mile or more to where the water is 

 about 200 feet deep. No doubt if one were able to live among the 

 animals on the floor of the Arctic Ocean shelf, other factors contribut- 

 ing to distribution would be found. 



Today ship bottoms provide a medium for the dispersal of species. 

 This factor is more important outside the Arctic Ocean than within 

 it, although whalers have been anchoring off Point Barrow and farther 

 east for over a hundred years. Some whaling vessels froze in at 

 Herschel Island for three winters in succession before obtaining a 

 cargo of oil and whalebone. A ship bottom can become quite foul in 

 six months. How many Arctic animals would such a ship carry into 

 the Pacific? 



The conditions in the Arctic Ocean are so stable and show such 

 a small degree of variation that an animal living in one place on the 

 Continental Shelf could find equal optimal conditions at any other point 

 with similar bottom within the ocean on the shelf. Nothing is known 

 of the fauna of the deeper Arctic Ocean bottom. 



To verify my theory that the Continental Shelf of the Arctic Ocean 

 is a unit environment, it would be necessary actually to measure 

 ecological factors and sample the animal population at a sufficient 

 number of places to show that all equivalent parts of the shelf sup- 

 port the same associated types. 



A common practice among marine ecologists is to consider the ocean 

 bottom as unchanging aggregations of animals. Nothing is farther 

 from the truth. In checking the bottom off Newport Bay, Calif., near 

 the Kerckhoff Marine Laboratory, the writer has found that between 

 1948 and 1952 the type of animals once found in certain regions has 

 entirely changed. At Point Barrow there was an indication of why 

 the bottom there would change materially over considerable areas 

 (see "Winter Dredging"), although the general picture of the region 

 and the whole Continental Shelf of the Arctic Ocean would remain the 

 same. In the fall of 1949 a layer of mud killed off what most 

 people would call an anemone-Strongylocenfrotus-Psolus association. 

 Whether it will come back the same or as a Strongylocentrotus- 

 Psolus-anemone, or a Psolus-anemone-Strongylocentrotus, or some 

 other combination of the three is anybody's guess. Perhaps it will 

 become something entirely different, such as a Balanus crenatus- 



