The Distribution and Biogeography of Zostera marina (Eelgrass) in Alaska 1 
C. Peter McRoy 2 
Although innumerable botanists have 
visited Alaska to record and study its flora, most 
accounts terminate at the high-tide line. Con- 
sequently, the marine vegetation, especially that 
of the most northern coasts of Alaska, has re- 
ceived little attention and the distributions of 
many species are sketchily known. Zostera 
marina Linnaeus, the common eelgrass, has 
probably received more interest than most, be- 
cause of its importance as a waterfowl food. 
In spite of this, the distribution outlined by 
Hulten (1941:95, 1960:69, 1964:256) and 
other published sources (Anderson, 1959:48; 
Porsild, 1932:90-94; Polunin, 1940:40-41; 
Setchell, 1920:563-579, 1935:560-577; Murie 
and Scheffer, 1959:396) is very incomplete in 
the light of recent surveys of the coast. By 
compiling the results of personal efforts and 
communications over the past few years, I can 
now document in detail the distribution of this 
species in Alaska. 
An additional result of searching and study- 
ing the distribution of Zostera in Alaska has 
been a review of the mechanisms of dispersion 
that have established and maintained this dis- 
tribution. These aspects of the study of Zostera 
have in turn led to considerations of the bio- 
geography of the species which can be recon- 
structed from distribution records and disper- 
sion mechanisms. 
Distribution Survey 
The genus Zostera contains 11 species of 
shallow-water, soft-bottom marine plants (Set- 
chell, 1935). The most widespread species of 
the genus, Zostera marina , occurs discontinu- 
ous^ throughout the boreal Northern Hemi- 
sphere from the seas of Okhotsk and Japan to 
the Baltic and Mediterranean (Setchell, 1935: 
571). On the Pacific coast of North America 
1 Contribution No. 42 from the Institute of Marine 
Science, University of Alaska. Manuscript received 
December 16, 1967. 
2 Institute of Marine Science, University of Alaska, 
College, Alaska 99701. 
Z. marina extends from Port Clarence, 65° N 
(Porsild, 1932:90) to Agiabampo Lagoon, 
26° N, in the Gulf of California (Steinbeck 
and Ricketts, 1941:254). 
In Alaska, Zostera forms a distinct subtidal 
zone in protected bays, inlets, and lagoons along 
the coast from Bering Strait south (Hulten, 
1941:95). During 1967 I was able to survey 
many miles of the Alaska coast to locate and 
examine the Zostera beds. These surveys in- 
cluded Southeast Alaska, Prince William Sound, 
the Cold Bay region of the Alaska Peninsula, 
parts of the Seward Peninsula near Nome and 
Teller, the coast of the Chukchi Sea between 
Kivalina and Cape Thompson, and the vicinity 
of Point Barrow. The observations from these 
field trips have been combined with the pub- 
lished records and personal observations of 
several people to present a detailed listing of 
the locations of Zostera beds on the coast of 
Alaska (Fig. 1 and Table 1). 
In Southeast Alaska, the Alexander Archi- 
pelago, Zostera is found in most of the bays 
and inlets of the outer coast, but it is absent 
from many of these on the inside waters (Fig. 
1 and Table 1). This is apparently due to the 
turbid effluent of glaciers. No plants were found 
in any of the areas receiving large amounts 
of glacial runoff although other environmental 
conditions appeared quite suitable for their 
growth. For example, in Doty Cove and Lime- 
stone Inlet in Stephens Passage (near Juneau) 
the absence of Zostera is enigmatic in winter 
months when ambient waters are clear; but in 
summer the problem is solved by the presence 
of very turbid water from nearby Taku Inlet. 
In bays and inlets receiving quantities of the 
turbid glacial water the subtidal zone of soft 
bottoms usually occupied by Zostera is devoid 
of all macrophytes. 
The coast from Cross Sound to Prince Wil- 
liam Sound is rugged and exposed to the open 
sea; most of the existing bays harbor glaciers 
or glacial streams. Zostera has been reported 
only in Yakutat Bay (Setchell, 1920:567; Fig. 
507 
