Acanthophora, a Possible Invader of the Marine Flora of Hawaii 1 
Maxwell S. Doty 2 
In THE FALL OF 1952, a small algal fragment 
was brought to the author from Pearl Harbor 3 
by Mr. Charles Cutress. In April, 1953, a much 
larger piece of the alga was brought in by Mr. 
Spencer Tinker, who had found it washed ashore 
near the Waikiki Beach Laboratory of the Uni- 
versity of Hawaii. Both collections were readily 
determined as representing a species of Acan- 
thophora Lamouroux (1813: 132), a rhodo- 
phytan genus. This genus is distinct and clearly 
recognizable among the floral elements occur- 
ring in this part of the world. A search of the 
literature and the herbaria available revealed 
no Pacific records of this genus from the Ha- 
waiian Islands or, with one exception, east of 
the Western Caroline and Marianas islands 
north of the equator. 
Other collections during succeeding years, and 
field observations as well, revealed a huge in- 
crease in the abundance of the species in Ha- 
waii during the next few years. In May, 1953, 
Dr. D. W. Strasburg found this alga "in abun- 
dance” at Keehi Lagoon, between Pearl Harbor 
and the Port of Honolulu on the leeward side 
of Oahu. Later the same month, a dense growth 
of the alga was found by the author ( numbered 
10774) and Dr. E. Y. Dawson at Hauula, north 
of Honolulu, on the windward side of the is- 
land of Oahu. Parts of this collection are the 
earliest collections from Hawaii represented in 
both the Bishop Museum and the University of 
California herbaria. From that time on, Acan- 
thophora has been so common on the leeward 
1 This work was made possible by a research time 
grant from the Graduate Research Committee of the 
University of Hawaii and facilitated by Office of Naval 
Research contract 2591 (00). 
Contribution number 154 of the Hawaii Marine 
Laboratory. Manuscript received January 23, 1961. 
2 Botany Department, University of Hawaii, Hono- 
lulu 14, Hawaii. 
3 According to Mr. Mikihiko Oguri, this algal col- 
lection probably came from West Loch, between Lau- 
launui Island and the northwestern shore. 
side of Oahu that it has not often been preserved 
as an herbarium specimen. 
Finally, during June, 1956, Dr. Otto Degener 
collected and sent in a specimen (his no. 24105) 
from Mokuleia on the windward shore of the 
island of Oahu, northwestward from Honolulu, 
collected by himself, Miss Marie Neal, and Dr. 
Constance Hartt, with the annotation ”... ubiq- 
uitous some distance within the reef; observed 
very rare here last year. This is first time aggres- 
sive marine alga threatening native kinds.” Cer- 
tainly it appears to be replacing (crowding out) 
elements of the native flora. Degener, who has 
paid close attention to the reef population at this 
particular site, feels the alga probably was not 
there until, at most, 2 years before this collection 
was made. 
Not only have frequency of observance and 
density of standing crop increased, but the dis- 
tribution has been that of a progressive en- 
circling of Oahu, one of the few islands of the 
Hawaiian Group where Acanthophora has been 
found. 
The alga has spread to Kauai, another of the 
Hawaiian Islands. Mr. Jan Newhouse has passed 
on local stories that the alga was not found 
around Kauai until about 1954 or 1955, and 
the observation that it is now ubiquitous. This 
genus was recorded from Kauai by Kohn and 
Helfrich ( 1957 : 243 ) . Their mention of the 
genus was based on observations of Newhouse 
about November, 1956, and was not included 
among the algae they collected and had identi- 
fied by Dawson at the time their earlier work 
(Helfrich and Kohn, 1955) was completed in 
October and November of 1955. It has been 
found neither among our earlier extensive col- 
lections from Kauai nor by Newhouse among 
his, but during August I960, Dr. Charles La- 
moureux and Mr. Tadayuki Kato made a collec- 
tion (Lamoureux coll. no. 1542) of Acantho- 
phora on Kauai at Poipu Beach. 
Specific, though in part cursory, searches dur- 
ing I960 for Acanthophora on the islands of 
547 
