INTRODUCED MARINE SPECIES IN PAGO ... - Bishop Museum

Skelton, P. A., Algae survey report
Fortunately for American Samoa, the algal inventory began in the early 1920s. Although, the flora
of the neighboring islands of Western Samoa began much earlier with an inventory carried out by
Grunow (1874) followed by Reinbold (1896). It is important to note that the marine flora of the two
countries are very similar and therefore should be considered as one (except for the remote atolls
of Swains and Rose part of American Samoa). The updated algal list for the Archipelago,
compiled by Skelton and South (1999, 2002) provides a checklist against possible recent
introductions. We must be cautious as we acknowledge that many cryptic species and species
found only in deeper waters were probably missed by earlier collectors, and careful analyses
need to be made to determine their introduced status. For example, the red alga Chrysymenia
kainbachii was first described from Papua New Guinea, and was collected in our surveys from the
Fagasa site. This alga has not been listed in previous algal compilations from the Archipelago
and it could easily be considered as an introduced species. However, this alga has been
recorded from Fiji and as far north as Hawai‘i. Moreover, the site where it was collected (Fagasa)
is fairly remote from potential source of introductions such as ports and harbors. It is therefore
unlikely to be an introduced species.
Utulei was found to be the most diverse site with 56 species recorded and 16 species were new
additions to Setchell’s list. Fagatele and Fagasa with 47 and 42 species, respectively, were the
next sites with high diversity. The numbers of new additions from these two sites were 16 species
for Fagatele and 15 for Fagasa. The majority of the new additions consist of minute epiphytic
algae such as Herposiphonia secunda, Griffithsia subcylindrica, Dictyopteris repens and
Hypoglossum anomalum. Some larger seaweeds are also found from our surveys include
Halymenia durvillei (ca 20 cm tall), Caulerpa serrulata (spread to > 10 cm, 5 cm tall) and
Galaxaura filamentosa (5 cm). Halymenia durvillei is an edible seaweed in Samoa (known locally
as Limu mumu or Limu aau). There has been an increased abundance of this seaweed in the
Apia Harbor, Western Samoa (pers. observ.). Caulerpa serrulata is also found abundant in the
Apia Harbor, especially near the break-wall by the Matautu Wharf (pers. observ.). Both these
algae were collected from Utulei (by the Harbor entrance). It is reasonable to assume the two
algae to have been introduced into the Pago Pago Harbor from neighboring Apia Harbor.
Although more studies including molecular work will need to be undertaken to confirm this.
Galaxaura filamentosa is a red alga that is often covered in fine silt, thus could have been easily
overlooked. It was collected from all of the sites except the docks, thus it is considered part of the
native flora.
Of the six sites that are considered vulnerable to introduced species (Aua, Docks 1 and 2,
Leloaloa, Onesosopo and Utulei), the algal flora was found to be very similar to those from other
less vulnerable sites. Only one alga Grateloupia filicina was found to be an anomaly in the flora,
although it has been reported from Fiji (South and Skelton 2003, in prep.), Hawai‘i (Abbott 1999)
and from French Polynesia (Payri and N’Yeurt 1997). This alga could be considered a recent
introduction as it was only found at the main dock attached to a rope that was anchoring a landing
craft. This is the first record of this species from the Archipelago.
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