Arctic Zooplankton- — JOHNSON 
321 
the Bering Strait and eastern Chukchi Sea. How- 
ever, other studies indicate that plankton or- 
ganisms may be transported across rather well- 
defined currents by eddy diffusion, and the pre- 
vailing currents along the Siberian coast might 
bring expatriates into the western portion of 
the Chukchi Sea. Brodskii (1950 ) does not in- 
clude E. gracilis in his list of copepods of the 
Polar Basin. 
Gurney (1931) has pointed out the specific 
variabilities that may occur in several species of 
Eurytemora living in different habitats in Eu- 
rope. It remains to be shown to what extent E . 
foveola may also be morphologically variable 
in diverse environments. The great range of 
Alaskan lagoon and estuarian habitats and the 
seven or more species on the Alaskan coast 
should provide excellent material for such a 
study. 
SALINITY RELATIONS 
Although the data are too few to give more 
than a glimpse into the salinity tolerances ob- 
served for the various copepod species identi- 
fied, still it is worthwhile to record such analyses 
as can be made from this area. Figure 19 ap- 
pears to divide the copepods encountered into 
three groups with respect to salinity range and 
preference. ( 1 ) Acartia bifilosa and A. clausi 
occurred over nearly the whole range encoun- 
tered but not below 0.83 %o at which value only 
relatively few specimens were found, especially 
A. clausi. The former was the dominant copepod 
in the two lagoons having highest salinities 6.42 
to 15.96 /co. (2) Cyclops spp., Eurytemora can- 
adensis , and Limnocalanus j o bans eni ranged 
from 0.1 6 to about 7 %c but appeared to thrive 
best at 0.73 to 0.83 %o. Eurytemora foveola n. 
sp. probably belongs to this group but stands 
somewhat alone in occurring only in ranges 
from 0.18 to 0.73 %o at which salinities it was 
dominant. Limnocalanus grimaldi, in this unique 
situation, occurred also at only a very low 
salinity, but elsewhere in the arctic it has a 
strong affinity for the sea. ( 3 ) The final group, 
into which Acartia bifilosa and A . clausi ex- 
tended, are the characteristically marine forms 
occurring in lagoon no. 2 south with salinities 
of 14.31 to 15.96 /co. Only in the more saline 
lagoons, nos. 2 and 4 south, was there any ap- 
preciable range in salinity from top to bottom. 
These two lagoons are also probably the ones 
most readily invaded by marine forms, but the 
influx of fresh water appears also to be quite 
high in these lagoons. Hence the communities 
are probably more or less transitory and fluc- 
tuate with repeated recolonizations. 
Whittaker and Fairbanks (1958) have studied 
the occurrence of various nonmarine copepods 
in inland lakes and ponds of different salt con- 
tent. The salinities and fauna they dealt with 
are of course not directly comparable with those 
of coastal lagoons, since the ratio of salts differ 
and their more saline species have different 
taxonomic relationships. But it is interesting to 
note that the transition between saline and 
fresh-water communities in their study was 
"somewhere between 425 and 875 ppm” for 
most bodies of water. If a comparison is justi- 
fied it must be with the fresh-water fauna of 
the lagoons, then lagoons nos. 1, 3, 5, and 6 
south and 1 and 2 north could be expected to 
foster truly fresh-water species and the occur- 
rence of Eurytemora canadensis and Limnocal- 
FlGS. 16—18. Eurytemora foveola n. sp. 16, Female, genital field and operculum, ventral; 17, male, mandi- 
bular blade; 18, male, labrum. 
