ON THE DISTRIBUTION OF RED ALGAE ( RHODOPHYTA ) ON THE CORAL REEF OF PARI ISLANDS , SERIBU ISLANDS

Many species of red algae are economically important for their carrageenan contents. Since May 1974 to June 1975 an intensive survey on their distributions have been carried out on the fringing reef of Pari Islands, Seribu Islands. Thirty five species of Rhodophyta have been identified and their species composition and relative importance as compared to Phaeophyta and Chlorophyta have been studied. Environmental factors, such as bottom type and seasonal influence on their distribution, emphasized in the discussion. Further studies on inventory and the distribution of these algae will be continued particularly in support of the culture experiments for some of the species.


INTRODUCTION
Some species of red algae are economically important as supplementary food and as raw materials for industries producing carrageenan for cosmetics, pharmacies, etc.
The inventory of algae in some areas is important for further studies on their taxonomy, morphology, and distribution.The data obtained is also necessary to support marine culture experiments.Marine culture helps improving natural stock which is being depleted by environmental factors.
Some investigators have been working on the same subject with different methods such as collecting, transecting, and standing crop assessing.TAYLOR (1937) and DAWSON (1955) made their studies in U S A ; Z A N E V E L D ( 1 9 5 5 ) a n d S U R J O D I N O T O & P A R D A N I N G S I H (1964) in Indonesia, TSUDA (1972) in the Caroline Island, VARMA & RAO (1962) in India, and DOTY (1970) in the Philippines.
The economically important algae in Pamban area, India, were confined to shallow regions, generally tp depths less than 2-3 meters and .practicallynone of the weeds are found deeper than 7 meters.They are distributed along the coral beds or on the rocky substratum covered with a thin layer of sand (VARMA & RAO 1962).
Thirteen genera of edible and commercial algae were recorded from the coral reef of Pari Island, five of which were red algae (SURJODINOTO & PARDANINGSIH 1964) Some species of Rhodophyta are depositors of calcium carbonate i.e. calcareous algae like Liagora sp., Peyjssonelia sp. and other species of Corallinaceae (DAWSON 1966) SUKARNO (1975) found that algae formed the dominant biota on the reef flats of Ayer Island, growing attached on rubbles or hard substrate and in the algal regions on the outer edges of the reef, where groups of Scleractinian corals were rare.
The difference between low and high water in this area is about one meter.Most of the reefs (sand flats) are not submerged during low tides except the moat with rubble substrates (Figs. 1, 2, and 3).
The data were obtained by observation, collection (made during December 1973 to May 1975), transect measurements (made during July 1972 to June 1975), and by standing crop determinations (made during August 1974 to January 1975).In the last case, transect lines were stretched at north-south direction, parallel to and at one to two hundred meters distance from one another.Observations were made by counting the number of species and the number of specimens for each species of algae found within one square metre areas along the transect lines.The distance between one area and the other is ten metres.Standing crop determinations were based on the wet weight of each algal species harvested per square meter.The samples were placed in 70% alcohol as liquid preservations and were also preserved as dry herbaria.

NOTES ON THE DISTRIBUTION OF RED ALGAE
Algal growths are generally found on rocky substrates or dead corals which are permanently submerged at the moat of reef.
Laurencia, Hypnea, and Acanthophora are found on sand flats.At the slopes of reef, Galaxaura, Liagora, and Zellera are collected.Halymenia durvillae and Hypnea sp. are found attached on living corals.The genera Amphiroa, Lithothamnion, and Goniolithon (Corallinaceae) generally grow on live or dead coral beds.Amphiroa is also found on the sea grass areas at the edge of lagoons.
Vegetation group of Laurencia obtusa is frequently found on dead coral fragments i.e. at the southeast of Burung Island.
Some species of sea grass (Spermatophyta) like Enhalus acoroides, Thalassia sp., and Halophyla spp.are found distributed in this area especially on the edge of lagoons and sand flats..

TRANSECTS
A total number of 73 transect lines were observed covering 3,098 square meters.From the transect lines individual and group algae were counted.Table II and III shows the quantities, distribution and dominance of algal groups.

The Area of Tikus Island
In this area red algae are found more abundant and more varied on rocky substrates than on sandy habitats.The amount of Rhodophyta is smaller than Phaeophyta (Sargassum spp., Padina spp., and Turbinaria spp.) and Chlorophyta (Caulerpa spp.and Halimeda spp.).Some of the species such as Laurencia spp., Acanthophora spp., Hypnea spp., and Gracilaria spp.are found in greater number than Eucheuma spp., Amphiroa spp., and Galaxaura spp.

The Area of Pari Island
In this area red algae (Rhodophyta) are smaller in number than Phaeophyta.Acanthophora and Hypnea (Rhodophyta); Sargassum and Padina (Phaeophyta); Caulerpa and Halimeda (Chlorophyta) are frequently found on sandy substrates.Besides the algae mentioned above, Laurencia are also found on rocky substrates.At certain areas Eucheuma spinosum is found in a relatively great number.

The Northeast Area of Burung Island
Phaeophyta in this area dominate over other algae.The important algae are Padina, Sargassum, Laurencia, Acanthophora, Gracilaria, and Hypnea.Caulerpa and Halimeda are the most common algae of the Chlorophyta.

STANDING CROPS
Measurements of standing crops from 15 stations shows that wet weight percentage of red algae varies from 18 to 100%.In the area of Eucheuma spinosum populations, the variations are between 18 to 45%.

NOTES ON THE DISTRIBUTION OF RED ALGAE
Table III.The number distribution and dominancy of benthic marine algae obtained from transect Communities of red algae reaching 100% are found to consist of Laurencia spp.only.The average red algae standing crops is 49.60% (Table IV).

EPIPHYTIC ALGAE
Red algae are also found on rafts used for culture experiment of Eucheuma spinosum in the lagoons and also as epiphytes on many thalli of other algae like Sargassum spp.Those are Acanthophora spicifera, Laurencia, Hypnea, Jania, Ceramium, and Polysiphonia.These algae are generally present on those rafts after one or two months following the beginning of cultivation experiments.

DISCUSSION
Thirty five species of red algae have been recorded from this area.This is much richer in species than that recorded by COURTENAY (1974) from Laudardale, Florida (11 species) and by DOTY (1970) from some areas in the Philippines (16 species) and still richer than that recorded by TSUDA & BELK (1972) from Caroline Island (32 species).But as compared to the 555 species recorded from Indonesian waters by VAN BOSSE (1928), the 320 species from around north Wellington Island ( ADAMS 1972) and 63 species from the waters of the Gulf of Mexico, (STAIDINGER & BREEDVELD 1971) the record from Pari Island is certainly not yet sufficient.From 54 species of useful algae from Indonesian waters (SUGIARTO 1968), 21 species are red algae and about half are known to this area.
The great species variations found here are possibly due to environmental conditions which are agreeable for red algal growth.The red algae are relatively adapted to shallow regions (FELDMAN 1951).Based on their substrates, the red algae in this area are generally "ephylithes" but are also found as "epiphytes" such as Laurencia, Hypnea, and Acanthophora spicifera.Exposure to direct sunlight on sandy habitats are tolerated by Acanthophora spicifera and A. dendroides.Some red algae such as Amphiroa sp.grow on seagrass areas, or attached to living corals such as Halymenia durvilleae and Hypnea sp.Galaxaura spp.generally grow on reef slopes.The red algae of the area can grow perennially and annually.
Visual observations show that the growth of thalli of some species of red algae generally occurs in August, September, and October.Further attention will be paid on this matter in the next study.

CONCLUSIONS
From the investigation that had been done in the coral reef of Pari Island, the following results are obtained : 1. Thirty five species of red algae have been identified from the collections obtained from the coral reef of Pari Island.2. The species variations and the percentage of wet weight per square meter of the red algae were greater in comparison to brown and green algae.3. Generally the algae grows in great numbers as "ephylithes" at moats of the reef than on sandy or muddy habitats.4. The quantities and qualities of growth are possibly related to environmental factors of this area.
5. Laurencia spp.are found in single populations whereas Eucheuma spinosum is nearly always found in mixed populations.6.The growth of algae of the area are apparent as perennial or annual.

Figure 2 :
Figure 2 : Cross section of typical bottom area in the coral reef of Pari Island.

3. and 4 .
Acanthophora spp., Laurencia spp., Sargassum spp., Padina spp., Caulerpa spp., and Halimeda spp.-TheArea of the Kongsi Island Concentration of algae are found predominantly on rocky habitats.Most of the Acanthophora, Eucheuma, Caulerpa, and Halimeda grow on this habitat.Of the Phaeophyta, Padina is found distributed on sandy and rocky habitats.Next important members of Phaeophyta are Sargassum and Turbinaria.

Table IV .
Wet weight composition per square meter obtained from standing crop measurements 5. ENVIRONMENTAL FACTORSa.