INTRODUCED MARINE SPECIES IN PAGO ... - Bishop Museum

Skelton, P. A., Algae survey report
is the easternmost limit for the natural spread of mangroves. Seagrasses (Halophila ovalis and
Syringodium isoetifolium) find their easternmost limit here, being absent from the Cook Islands
and then reappearing with a different species in French Polynesia (Halophila decipens). This may
indicate that the distribution of some marine plants is still continuing eastward. It is highly possible
that some of the algae recorded in our surveys have recently been brought in from neighboring
countries, particularly Western Samoa. Two species that could be considered in this category are
Caulerpa serrulata and Halymenia durvillei. These two species are found abundant at the Apia
Harbor and were found to be common in Utulei. It is interesting to note that these two algae have
an Indo-Pacific distribution but had not been recorded from American Samoa by Setchell, despite
the fact that both species are fairly large. Another species of interest is Codium mamillosum.
Although only a juvenile specimen was collected, it is noted that Codium species are notorious in
terms of invasiveness. Codium arenicola is a species found in Southeast Asia but it appears to
have spread as far east as Apia Harbor including Suva Harbor (pers. observ.). This alga is yet to
be found in Pago Pago Harbor, although with frequent commuting between Apia Harbor and
Pago Pago, it may find its way here. Another Codium species that is of concern worldwide is
Codium fragilis ssp. tomentosoides with an Atlantic origin has spread to North America, the
Mediterranean and New Zealand. Grateloupia filicina is an alga with its type locality from Italy was
collected from the main Dock. It would be tempting to label this alga as invasive species but it has
been recorded from Hawai‘i (Abbott 1999) and French Polynesia (Payri and N’Yeurt 1997).
There is one alga that has a disjunct distribution, Sporocladopsis erythraea. This minute green
alga was recorded from the Red Sea by Nasr (1944). There are only two Sporocladopsis species
known with the second species (Sporocaldopsis novae-zealandiae) found in New Zealand and
Australia (Millar and Kraft 1994). The occurrence of this alga in our collections was a surprise
find, as it was epiphytic on the base of a Sargassum anapense an endemic brown alga to Samoa.
We consider the presence of Sporocladopsis erythraea as native, and it may well be more
common than currently reported, but its small size and cryptic habitat may contribute to its being
overlooked.
Discussion
The algal diversity within the tropical Pacific Ocean to some extent generally follows the pattern
seen in other tropical marine organisms (e.g. corals, fishes, gastropods, etc.), with the highest
diversity found in the Indo-Malay region. Algae, unlike other tropical marine organisms have their
highest species diversity in a few but widely dispersed areas ranging from temperate (South
Australia), sub-tropical (southern Japan) to tropical Philippines (Bolton 1994). All of these places
contain over 800 species, and their floras continue to receive much attention from scientists. By
contrast, the Pacific Islands have had little scientific study of their marine flora. Of the few better
known places [Hawai‘i (400 spp.), Fiji (500 spp.), French Polynesia, and Samoa (both with over
300 spp.)] many areas and reefs remain to be surveyed. These surveys are important as they
provide the baseline information needed when discussing introduced marine species.
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